JPS58143435A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape with good durability, by forming a ferromagnetic layer on the surface of a tapelike base which moves along a cooling roll, etc., so that the partial pressure of oxygen is maximum and the ratio between the whole pressure of gas other than oxygen and a mean vapor-deposition speed is less than a specific value. CONSTITUTION:The inside of a vacuum tank 10 is partitioned by a partition 11 into a take-up room 12 and a vaporation room 13 to form mutually independent evacuation systems and on the tapelike base 2 which moves along a cylindrical can 1 as shown by an arrow, the magnetic layer is formed by emitting an electron beam 7 from an electron gun 6 to a vapor-deposition source 3 for Co-Ni, etc. In this case, the minimum angle of incidence of the vapor flow passed through the mask 4 is limited; when the part where the vapor is received is A, the center of the can 1 is 0, and the part that the vapor strikes at an angle close to a tangent is A, the mean vapor-desposition speed R (Angstrom /sec) depending upon the angle AOB and the moving speed V of the substrate 1 is calculated, and vapor deposition is carried out so that the relation when the partial pressure of oxygen is maximized and the partial pressure of gas other than oxygen is denoted as Pt is satisfied. In this case, Pa is pressure unit pascal. Thus, the long-life magnetic tape which is durable even when stored under various conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a magnetic recording medium, in which a ferromagnetic layer is formed by vacuum deposition on a tape-shaped substrate such as a polymer molded product, either directly or via a nonmagnetic layer.

In magnetic recording, the usefulness of a medium having a ferromagnetic metal thin film layer as a magnetic layer for short wavelength recording is well known.

However, in applying this medium to helical scan video applications and promoting short wavelength recording on a practical scale, the problem is the resistance of the ferromagnetic layer to corrosion and abrasion.

Conventionally, many of the methods used to solve this type of problem include coating, plating, vacuum deposition, and sputtering.

The method was to deposit a thin film protective layer of an organic material, metal, oxide, intermetallic compound 2 alloy, etc. by a known thin film forming method such as plasma or OVD.

In order to expect a protective effect from a thin film obtained by these methods, a film thickness of at least 600 mm is required, and this film thickness causes a space loss close to -edB at a recording wavelength of 0.5 μm. Practically unfavorable.

The present invention was developed in view of the above, and is based on the use of partial oxidation to form an oxide film on the surface of the metal constituting the magnetic layer.As a result of numerous experiments, the protective effect of the thin film was determined under the film formation conditions. I have completed the present invention by determining that there is an important relationship between the two. The present invention will be explained below using the drawings.

FIG. 1 shows an example of an apparatus for carrying out the invention.

In the present invention, as shown in the figure, one of the requirements is to move the tape-shaped substrate 2 along, for example, a cylindrical can 1 as a rotating cooling support.

Although FIG. 1 shows a cylindrical can 1 as a cooling support, it may be an endless belt-like cooling body or a combination of a cylindrical can and the above belt.

In the present invention, the maximum partial pressure component in the vacuum atmosphere during the formation of the ferromagnetic film is oxygen, and a certain relationship is maintained between the total pressure Pt (Pa) of other gases other than oxygen and the deposition rate. This fact greatly contributes to improving the durability of the ferromagnetic film, which will be described later.

The vapor deposition rate is defined as the average vapor deposition rate R [in/formula], which is the value obtained by dividing the obtained film thickness by the time during which the tape-shaped substrate moving along the rotating cooling support undergoes vapor deposition.

Now, as shown in FIG. 1, the tape-shaped substrate 2 moving along the circumferential side of the cylindrical can 1 is evaporated with a portion of the vapor flow from the evaporation source 3. Controlling the coercive force limits the minimum angle of incidence of the vapor flow by the mask 4. This mask also serves as a nozzle for introducing oxygen by adjusting the needle valve 6.

Of course, this does not mean that they can be arranged independently, but they are shown in a simplified manner. Let the center of the rotation axis of the rotary can be 0, and let the part where the steam is incident at an angle close to the tangent line be M, and the part that receives the steam at the minimum angle of incidence be B, and furthermore, let the moving speed of the base be V (m/5ecJ). , set the diameter of the can to 2D (
m), the average deposition rate R[in/see, l can be calculated by comparing OB with 2π radians and measuring the film thickness.

The evaporation source is heated by an accelerated electron beam 7 emitted from an electron gun 6. 8 is a feeding shaft for the tape-like base; 9
is the winding shaft. glow treatment means for pretreatment;
Although the glow processing means for post-processing, free rollers, expander rubber rollers, etc. are not shown in the drawings, they are of course provided as necessary.

The vacuum chamber 10 is partitioned into a winding chamber 12 mainly equipped with a winding mechanism and a deposition chamber 13 where vapor deposition is performed, each of which is provided with an independent exhaust system 14, 15.

FIG. 2 shows an endless belt 16 obtained by welding thin steel plates, for example, by two rotary drive bodies 17 and 18.
A case is shown in which the substrate 2 is rotated at a constant circumferential speed while being cooled, and the substrate 2 is conveyed along this rotation. A and B in the same figure are the first
This is the same as in the figure.

Using these devices, a substrate of polyethylene terephthalate film (thickness 10 μm) was used to create a film with a length of 1000 m.
After the film is flattened, it is slit to a width of %1/1 to create a magnetic tape.Then, 100m of this magnetic tape is wound onto a reel to form a 60'C9
After maintaining a constant sowing period in an environment of 5% RH, playback was performed at a recording wavelength of 0.83 μm using an open deck, and the frequency of clogging was limited to 3 times per 1 oom tape length.
The data was summarized as the number of days when the number of clogs occurred three or more times as the number of days when clogging started.

The evaporation source is a refractory container made of mgo or Z
Using a refractory container made of rO2, the electron beam is produced by optimizing the cand shape of the electron gun, the shape of the Wehnelt electrode, and the relative positional relationship between the two.
Adjustments were made to enable examination of ~80oO people/5ec).

The magnetic material mainly used was Go80%Ni2O%, but
Regarding whether the relationship described below depends on the material composition,
0086%Ni 15%, Go90%Ni1o%, 0o
7E% Ni25%, Go 70% Ni 30%,
A material composition of 100% Co was confirmed.

Regarding the thickness of the substrate, the thickness of the polyethylene terephthalate film is 6 μm to 26 μm.
I researched the materials up to 26μ thick.
Polyamide film and polyimide film were investigated with m constant.

The degree of vacuum was measured by placing nude gauges near the outlet of the pump and near the position of the substrate on which the film was to be formed, and examining the relative relationship.

Calibration was also performed using a quality analyzer, and the value obtained by subtracting the oxygen partial pressure from the total pressure was calculated as Pt (Pa).

Regarding whether there are differences depending on the type of vacuum evacuation system, we investigated oil diffusion pump systems, oil diffusion pumps with liquid nitrogen traps, cryopump systems, oil diffusion pumps and cold panel systems, and turbo molecular pump systems. We confirmed the cases in which each was used. For oil diffusion pump systems, use mineral oil.

We investigated the effects of several oils with different boiling points, such as silicone oil.

The diameter of the cylindrical can was 1 m, and a coaxial acceleration type electron gun of 30 KV and a maximum of 6 m was used to generate the electron beam.
0080%Ni2O% was placed in an O2 container and evaporated under an oxygen partial pressure of 2 x 10 Totr at a minimum incident angle of 36, changing the electron beam irradiation conditions and the moving speed of the substrate.
The head blinding start date was investigated using Pt/R (one Pa-5ec) as a parameter.The results are shown in FIG.

From Figure 3, the zone where the clogging start date suddenly drops is Pt.
/R= 7 X 10 ~ 8 X 10 [Pa-5
ec1 person]. The error par in Figure 3 was obtained from data at 10 points obtained by dividing a 1000 m long magnetic tape into 10 rolls, and was obtained from Pt/R
is 7 X 10 ~ 8 X 10 (Pa-5ec/
It has been shown that when the value exceeds 1, the start date of the blind date becomes earlier and the range of error par becomes wider.

This tendency remained almost unchanged even when the various conditions mentioned above were changed.

If oxidizing glow treatment or ozone treatment is applied after vapor deposition, the absolute value of the clogging start date will change, but the fact that there will be an inflection point where there is a sudden drop as mentioned above will hardly change. , indicating that the film quality is defective.

N2 as a gas component. N20. N2. Go, 0
It is interesting that when using 02 etc., the Pt/R shows almost similar trends, although there are differences in size depending on the conditions of the pump system etc. The cause is being investigated in detail, but it may be a type of contamination. It can be considered that this is the case.

Also, in Figure 2, 01mm = 20cm, 02B
~60crrL, 0102:100CWL,
0080%Ni2O% as magnetic material, oxygen partial pressure 3X1
Under 0 Totr, the minimum incident angle is 40 and the thickness is 0.1μ.
A magnetic layer with a thickness of m to 0.3 μm was formed.

When Pt/R is 10 (Pa-sec/person), the saturation value on the start date of blindness is 260 days on average at 60°C and 96% RH, and 440 days on average at 90% RH at 40', and the inflection point is Pt
/ R = 8.3 x 10 (Pa-sec 1 person)
existed in

As is clear from the above, the present invention provides i)
By forming a magnetic layer with Pt/R maintained below 7 x 10 (Pa-5ec/person), it is possible to easily obtain a highly durable magnetic recording medium that can withstand storage in various environments. The industrial value of this invention is in dogs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention;
FIG. 2 is a diagram showing a modification of the essential parts of the above-mentioned apparatus, and FIG. 3 is a diagram for explaining the present invention in detail, showing the relationship between the head clogging start date and Pt/R. 1... Cylindrical can, 2... Tape-shaped substrate, 3... Evaporation source, 6... Needle valve, 6... Electronic Gun, 10... Vacuum tank.

Claims (1)

[Claims] When a ferromagnetic layer is formed on a tape-shaped substrate moving along a rotating cooling support by a vapor deposition method in a vacuum in which the maximum partial pressure component is oxygen, other than oxygen is removed. Let the total pressure of the gas be Pt(
Pa) and the average deposition rate is R [person/person], then P
A method for manufacturing a magnetic recording medium, characterized in that the relationship t/R≦7X10-' (Pa-55/person) is satisfied.