JPH06103569A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate trouble such as the sticking of dust and to obtain proper surface roughness when the back coat layer of a vapor-deposited tape is formed. CONSTITUTION:Aluminum(Al) evaporated by heating with an electron beam gun 9 is deposited on the rear side of a magnetic tape 6 with a magnetic layer formed by vapor-depositing a Co-Ni alloy and the Al vapor-deposited side is irradiated with ions of a gas such as N2 from an ion gun 11 to form a back coat layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art Magnetic recording media, such as magnetic tape,
A conventional coating tape made by applying a magnetic paint in which magnetic powder is dispersed in a binder on a film that is a non-magnetic support, and a vapor deposition method in which a metal is deposited on the film in a vacuum without any binder. There is a type tape.

Vapor deposition type tapes are 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. The main structure of the vapor-deposited tape currently on sale or under development is as shown in FIG. The film 21 is made of PET (polyethylene terephthalate), polyimide, aramid, or the like. Various thicknesses of 2 to 50 μm are used.

The magnetic layer 22 is formed by depositing a Co--Ni alloy (80% -20%) on the film 21 in a thickness of 1500Å by using a vacuum deposition method. An undercoat layer may be interposed between the film 21 and the magnetic layer 22 to improve the binding property and the like. The top coat layer 23 protects the magnetic layer 22,
Also, it is coated to have a function as a lubricant for smooth contact with the recording / reproducing head. As a coating method, a gravure method or a die coating method is used. The component is a fluorine-based lubricant, and perfluoropolyether (for example, a product name "Homblin" manufactured by Montedison Co., Ltd.) is used.

The back coat layer 24 is made of carbon (particle size 10 to 10
100 nm) is dispersed in a binder (a vinyl chloride type, a urethane type, a nitrification cotton type, etc. is used alone or mixed), and the thickness after drying is 0.4 to 1.0 μm by the gravure method, the reverse method or the die coating method. So that the magnetic layer 22 of the film 21
Apply on the surface opposite to the vapor deposition surface. Here, the main points of the back coat layer are as follows.

(1) By having conductivity, dust is prevented from being attached due to an antistatic effect. (2) Surface stability (coefficient of friction) is controlled to obtain running stability. (3) In terms of hardness, the front magnetic layer and the back are balanced to prevent warpage.

Conventionally, a coating material in which carbon is dispersed in a binder is applied as a back coat layer. The above (1) is controlled by the conductivity of carbon, and the above (2) is controlled by the particle size of carbon and the coating process. Due to the above (3)
Was satisfied by controlling the binder and the coating thickness.

[0008]

However, in the conventional case, even in the vapor deposition type tape, the back coat layer is a coating type, and if the back coat layer is first coated and then the magnetic layer is vacuum deposited, Degassing from the back coat layer (generated from the solvent of the binder) occurs in a vacuum system, and the degree of vacuum is reduced, resulting in poor vapor deposition.

Therefore, conventionally, after depositing the magnetic layer in vacuum, the tape is taken out into the atmosphere and then the back coat layer is applied. However, in this method, in the step of applying the back coat layer, the magnetic layer becomes dirty or dust is attached, and the dropout inspection (the magnetic tape is put in the inspection cassette deck and reproduced while recording a certain signal). However, there is a problem in that the number of dropouts is increased in the inspection for detecting dropouts where the reproduction signal is lost due to scratches on the tape surface or adhesion of foreign matter.

Further, although carbon has good conductivity,
Since the binder is added, there is a problem that conductivity is lowered and antistatic effect is lowered. In view of such circumstances, the present invention can solve problems such as adhesion of dust when forming a back coat layer on the surface of the non-magnetic support opposite to the magnetic layer deposition surface, and is also sufficient in terms of performance. The purpose is to obtain performance.

[0011]

Therefore, according to the present invention, when the back coat layer is formed on the surface of the non-magnetic support opposite to the magnetic layer deposition surface, the non-magnetic support is formed in vacuum. A method for manufacturing a magnetic recording medium, comprising depositing a metal on the surface opposite to the above, and irradiating the deposited surface with gas ions.

That is, like the magnetic layer, the back coat layer is formed by depositing a metal by the vacuum deposition method. By forming the back coat layer in vacuum in this manner, problems such as adhesion of dust do not occur, and since the binder is not included, conductivity is not lowered and a sufficient antistatic effect is obtained. still,
The vacuum vapor deposition of the magnetic layer and the back coat layer may be continuously performed, or may be divided into steps, and after one vapor deposition is wound up on a roll and then unwound from the roll, the other vapor deposition may be performed. Even if the magnetic recording medium is placed in the atmosphere in the middle of performing the division, no problem such as adhesion of dust will occur unless the magnetic recording medium is wound on a roll and unwound in the atmosphere.

If the back coat layer is formed by simple vacuum deposition, that is, if it is a metal, the surface roughness (center line average roughness) Ra remains as smooth as 1 to 2 nm and the friction coefficient is 0.6. Since it becomes as high as ~ 1.0 and the running stability becomes poor, the surface is roughened by irradiating the vapor deposition surface with gas ions, and the surface roughness of the back coat layer is adjusted to an appropriate range. Thereby, Ra = 10 to 20 nm can be adjusted, and the friction coefficient can be set to 0.1 to 0.4.

Various metals can be considered to be vapor-deposited as the back coat layer, but Al, Zn, Sn, Ni,
Ag or the like is used. However, Al is optimal in terms of price, vapor deposition rate, and stability after oxidation. As a method of ion irradiation, there are a Kauffman type and an ECR (high frequency) type.

As the gas, N ₂ , O ₂ , Cl ₂ , CH
Any ionizable gas such as ₄ may be used.

[0016]

EXAMPLE An example of the present invention will be described below. First,
1500 Å of Co-Ni alloy (80% -20%) was deposited on the PET film with a thickness of 9.8 μm by vacuum deposition.
The magnetic tape having the magnetic layer thus formed was wound on a roll.

Next, using the vacuum vapor deposition apparatus shown in FIG. 1, 1000 liters of Al metal was adhered to the back surface of this magnetic tape to form a back coat layer. The vacuum vapor deposition apparatus of FIG. 1 will be described. The vacuum container 1 is brought into a vacuum state by the operation of the turbo pump 2 and the rotary pump 3.

An unwind roll 4 and a take-up roll 5 are provided in the vacuum container 1, and the magnetic tape 6 is cooled by a cooling can while being unwound from the unwind roll 4 and wound by the take-up roll 5. 7 is wrapped around the lower side surface of the vehicle to run. A crucible 8 made of MgO is placed below the cooling can 7, and Al is put therein.

Then, the Al in the crucible 8 is irradiated with an electron beam from an electron beam gun 9 obliquely above and heated to evaporate Al. And
A shield plate 10 for restricting the vapor deposition range on the magnetic tape 6 is arranged between the crucible 8 and the cooling can 7. A Kauffman ion gun 11 is arranged on the cooling can 7 toward the magnetic tape 6 on the downstream side of the vapor deposition section.
A gas introduction pipe 12 is connected to the ion gun 11. In this example, N ₂ is ionized and the Al vapor deposition surface is irradiated with an acceleration voltage of 1.5 KV.

Here, the roll of the magnetic tape on which the above-mentioned magnetic layer is formed is set on the unwind roll 4, and the magnetic tape 6 is made to run on the cooling can 7 with the back surface of the magnetic tape 6 facing outside, and the electron beam gun 9 is used. Al that was heated and evaporated was deposited. Then, the Al vapor deposition surface was irradiated with N ₂ ions by the Kaufman ion gun 11 to obtain an appropriate surface roughness. Then, the magnetic tape 6 which has undergone the vapor deposition of the back coat layer and the surface treatment was wound on a winding roll 5.

After that, the magnetic tape was taken out into the atmosphere, and
A slitter (cut) having a width of mm was inserted into an 8 mm cassette, and a dropout was measured. A dropout counter was used for the measurement of dropout, and a dropout of -16 dB output within 10 μs was taken as a dropout.
As a comparative example, carbon having a particle size of 20 nm and 60 nm having a particle size of 1: 1 is mixed with vinyl chloride and urethane with a ratio of 1: 1.
Using the coating material dispersed in the binder mixed in, the same film as the magnetic layer deposited in Example 1 was coated as a back coat layer to a thickness of 0.5 μm. Then, the dropout was measured as in the example.

The measurement result is dropout =
8 pieces / minute, and in the comparative example, dropout = 11 pieces / minute. From this result, the dropout in the example of the present invention is about 30% lower than that of the comparative example of the conventional method. It is considered that the reason is that the adhesion of dust was prevented.

Further, in the example, a comparison was made between the case where only Al was vapor-deposited and the case where ion irradiation was carried out. Ra = 2n for the case where only Al was vapor-deposited.
m, friction coefficient = 0.8, but due to ion irradiation, R
a = 12 nm and friction coefficient = 0.25, which were in the proper range. still,
Although the vacuum vapor deposition apparatus of FIG. 1 has been described only for vapor deposition of the back coat layer, the present apparatus allows Al to be Co--N.
Instead of the i alloy, the ion irradiation was stopped, vacuum deposition of the magnetic layer was performed, and then the magnetic tape of the winding roll 5 was set on the winding roll 4 and the back surface of the back coat layer was formed on the back surface as described above. Deposition may be performed.

Further, a vapor deposition portion for the magnetic layer and a vapor deposition portion for the back coat layer are provided continuously in one traveling path in the vacuum container,
Vacuum deposition of the magnetic layer and the back coat layer may be continuously performed.

[0025]

As described above, according to the present invention, since the back coat layer is formed by vapor deposition in vacuum, problems such as adhesion of dust are solved, and since the binder is not contained, the conductivity is improved. As a result, the antistatic effect is improved. . Further, if the back coat layer is formed by simple vacuum deposition, the running stability is poor and the running stability is poor, but by running gas ions after the deposition to make the surface roughness appropriate, the running stability is also improved. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a vacuum vapor deposition apparatus used in an embodiment of the present invention.

[Fig. 2] Configuration diagram of vapor deposition type tape

[Explanation of symbols]

 1 Vacuum container 4 Unwinding roll 5 Winding roll 6 Magnetic tape 7 Cooling can 8 Crucible 9 Electron beam gun 10 Shielding plate 11 Kaufman ion gun 12 Gas introduction tube

Claims (1)

[Claims] 1. When a back coat layer is formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is deposited, a metal is deposited on the surface of the non-magnetic support on the opposite side in vacuum. And a method for manufacturing a magnetic recording medium, characterized in that the vapor deposition surface is irradiated with gas ions.