JPH06103557A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the transfer of a back coat layer to a magnetic layer and to reduce the occurrence frequency of drop-out by vapor-depositing a metal on one side of a nonmagnetic substrate opposite to the other side to be coated with the magnetic layer and forming the back coat layer by the vapor deposition. CONSTITUTION:A metal such as Al, Zn, Sn, Ni or Ag is used as a metal to be vapor-deposited to form a back coat layer, but Al is optimum from the viewpoint of cost, the rate of film formation and stability after oxidation. Since the formed back coat layer does not contain a binder, the electric conductivity does not lower and a satisfactory antistatic effect is obtd. Even when the back coat layer comes in contact with a magnetic layer in a wound state, the transfer of the back coat layer to the magnetic layer can be prevented and the occurrence frequency of drop-out can be reduced.

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 magnetic layer containing magnetic powder and a binder as main components on a non-magnetic support.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, for example, a magnetic tape, a magnetic layer is formed by applying a magnetic paint in which a magnetic powder is dispersed in a binder onto a film which is a non-magnetic support. The type is well known. In recent years, the coating type is shifting to the vapor deposition type, but the coating type is superior in terms of durability, and it is expected that the coating type will continue to be the mainstream for commercial use. As the film, PET (polyethylene terephthalate), polyimide, aramid or the like is used.

On the surface of the film opposite to the surface coated with the magnetic layer, a carbon (particle size of 10 to 10
100 nm) is dispersed in a binder (a vinyl chloride-based, urethane-based, nitrified cotton-based, etc. is used alone or as a mixture), and the thickness after drying is 0.4 to 1.0 μm by the gravure method, the reverse method or the die coating method. Is applied so that Here, the main points of the back coat layer are as follows.

(1) By having conductivity, dust is prevented from being attached due to the 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.

[0005]

By the way, a magnetic tape or the like is generally wound into a roll and stored.
In the wound state, as shown in FIG. 2, the magnetic layer on the front side of the magnetic tape and the back coat layer on the back side of the magnetic tape to be wound next are in contact with each other. However, since the magnetic layer contains a binder, and the backcoat layer also contains a binder, it is easy for them to stick to each other, and the backcoat layer is transferred to the magnetic layer, causing a dropout test (for testing the magnetic tape The problem of increasing the number of dropouts in the inspection to detect the dropout where the reproduction signal is missing due to scratches on the tape surface or foreign substances adhering, etc.) There was a point.

Regarding the back coat layer, although carbon has a good conductivity, there is a problem that the conductivity is lowered because the binder is added, and the antistatic effect is lowered. In view of such conventional problems, the present invention can prevent transfer of the back coat layer to the magnetic layer and improve the conductivity of the back coat layer in the magnetic recording medium having the coating type magnetic layer. The purpose is to be able to.

[0007]

Therefore, according to the present invention, in a magnetic recording medium having a magnetic layer containing magnetic powder and a binder as main components on a non-magnetic support, a magnetic layer coated surface of the non-magnetic support is provided. The back coating layer is formed by depositing a metal on the surface opposite to the above. There are various possible metal depositions for the back coat layer,
Al, Zn, Sn, Ni, Ag, etc. are used. However, Al is optimal in terms of price, vapor deposition rate, and stability after oxidation.

[0008]

In the above construction, since the back coat layer does not contain a binder, even if the magnetic layer and the back coat layer come into contact with each other in the rolled state, transfer of the back coat layer to the magnetic layer can be prevented. Further, since the back coat layer does not contain a binder, the conductivity is not lowered and a sufficient antistatic effect is obtained.

[0009]

EXAMPLE An example of the present invention will be described below. First,
On a PET film having a thickness of 9.8 μm, a magnetic coating material in which magnetic powder was dispersed in a binder was applied, and the magnetic tape having the magnetic layer thus formed was wound on a roll.

Next, using the vacuum vapor deposition apparatus of 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 unwinding roll 4 and a winding roll 5 are provided in the vacuum container 1, and the magnetic tape 6 is cooled by a cooling can while it is unwound from the unwinding roll 4 and wound on the winding 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 electron in the crucible 8 is irradiated with an electron beam from an electron beam gun 9 obliquely above, whereby the Al is evaporated by heating. 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. The tip of the oxygen introducing tube 11 guided from the outside to the inside of the vacuum container 1 is arranged so as to face the vapor deposition surface from the hole of the shielding plate 10. The amount of oxygen introduced can be adjusted by a flow rate control valve (not shown).

Here, the roll of the magnetic tape coated with the magnetic layer described above 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. While introducing oxygen, Al heated and evaporated by the electron beam gun 9 was attached. Regarding the amount of oxygen introduced, 25 cc of 99.998% pure oxygen was introduced per minute. Then, the magnetic tape 6 on which vapor deposition of the back coat layer was completed was wound up on a winding roll 5.

The reason for introducing oxygen is as follows. If the back coat layer is formed by simple vacuum deposition, that is, if it is a metal, the surface becomes too smooth and running stability deteriorates.Therefore, oxygen is introduced during vapor deposition to control the friction coefficient of the back coat layer. Then, the surface is roughened by the oxidizing action.

Here, it is desirable to set the oxygen introduction amount so that the resistance value (surface resistance) of the back coat layer becomes ⁵ to 10 ⁵ Ω / sq. That is, the introduction of oxygen weakens the metal bond and lowers the conductivity. Therefore, the resistance value is determined and the amount of oxygen introduced is regulated. A resistance value of 5 to 10 ⁵ Ω / sq means that the resistance value is 5 Ω.
When it is lower than / sq, the amount of oxygen is small and the friction coefficient of the back coat layer becomes too low. Resistance value is 10 ⁵ Ω / sq
If it is higher, the coefficient of friction becomes too high, and the conductivity becomes too low, which may lead to the attachment of dust. The target should be approximately 10 ³ Ω / sq. The center line average roughness corresponds to Ra = 8 to 20 nm.

Next, the characteristic measurements and the results of the examples will be described. The magnetic tape on which vapor deposition of the back coat layer had been completed as in the example was taken out into the air, slitted (cut) into a width of 8 mm, inserted into a cassette of 8 mm, and the dropout was measured. In addition, the measurement of dropout is
-16dB within 10μs using dropout counter
The dropout was made when the output decreased. In addition, the surface resistance of the back coat layer was measured. Further, the jitter (the degree of blurring of the luminance signal) was measured using a jitter meter (manufactured by Minato Electronics Co., Ltd.).

As a comparative example, carbon having a particle size of 20 nm and 60 nm mixed in a ratio of 1: 1 was used as a mixture of carbon and vinyl chloride.
The coating material dispersed in the binder mixed in 1 was applied to the same magnetic tape on which the magnetic layer had been applied as in the example so that the back coat layer had a thickness of 0.5 μm. Then, dropout, surface resistance, and jitter were measured in the same manner as in the example.

The results of these measurements are shown below. Dropout (pieces / minute) Surface resistance (Ω / sq) Jitter (ns) [Example] 24 7 × 10 ² 63 [Comparative Example] 32 5 × 10 ⁶ 74 From these results, in the Example of the present invention, Compared with the comparative example, which is the conventional method, the dropout was significantly reduced. It is considered that this means that the transcription has disappeared. Further, since the surface resistance is reduced and the conductivity is improved, the antistatic effect can be expected. Furthermore, jitter was reduced and running stability was improved.

In this embodiment, the back coat layer is vapor-deposited.
Occasionally, oxygen is introduced to control the surface roughness due to its oxidizing action.
I tried to roll it, but after vapor deposition
Then N ₂, O₂, Cl₂, CH_FourIrradiate gas ions such as
Alternatively, the surface roughness may be controlled.

[0020]

As described above, according to the present invention, since the back coat layer is a vapor deposition type containing no binder as compared with the coating type magnetic layer having a binder, the back side of the magnetic layer and the back layer are in a rolled state. Even when it comes into contact with the coat layer, it is possible to prevent the transfer of the back coat layer to the magnetic layer and reduce the number of dropouts.

Further, since the back coat layer is composed only of metal and does not contain a binder, the conductivity is not deteriorated and a sufficient antistatic effect can be obtained.

[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 is a diagram showing a state in which the tape is wound.

[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 Oxygen Introducing Tube

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer containing magnetic powder and a binder as main components on a non-magnetic support, a metal is vapor-deposited on the surface of the non-magnetic support opposite to the surface coated with the magnetic layer. A magnetic recording medium having a back coat layer formed thereon.