JPH064862A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve mass productivity by introducing oxygen into an initial incident region of Co vapor and forming a nonmagnetic CoO ground layer. CONSTITUTION:While a high-polymer substrate 1 is made to travel along a cylindrical can 4, the nonmagnetic CoO ground layer is formed in the region on the side nearer the inlet of a nozzle 10 for forming the nonmagnetic CoO ground layer and in succession, A Co-O magnetic layer is formed on the side nearer the outlet. The nozzle 10 is disposed in proximity to the can 4 as far as possible at this time and oxygen is blown out toward the inlet side of the substrate 1 like an oxygen introducing direction 11, by which the quantity of the oxygen to be introduced is minimized. A shield 6 may be provided between the nozzle 10 and an evaporating source 8 to prevent an oxygen blow-off port from being closed by deposits during vapor deposition. The position of the nozzle 9 for oxygen introduction for forming the Co-O may not be near the outlet shield 7 and may be parted from the can 4. As a result, the magnetic tape having decreased drop-outs is produced with good mass productivity by one stroke.

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 excellent high density recording / reproducing characteristics.

[0002]

2. Description of the Related Art At present, magnetic recording / reproducing devices tend to be smaller and have higher densities, and metal thin film type media have been attracting attention as exceeding the limit of high density of conventional coating type media.
In this regard, a metal thin film type medium made of Co-Ni-O has been put to practical use as a magnetic tape for VTR.

However, home digital VTRs,
Further excellent high-density recording / reproducing characteristics are required for magnetic recording media compatible with next-generation VTRs such as high-definition VTRs. Co-Cr, Co-Ni-can be used as candidates.
Magnetic recording media containing Cr, Co-O, Co-Ni-O, or the like as a main component have been studied.

Among them, Co-O formed through a non-magnetic CoO underlayer has excellent magnetic characteristics and recording / reproducing characteristics, and is expected as a next-generation magnetic tape.

FIG. 4 shows a web coater type continuous vapor deposition apparatus using a cylindrical can system as an example of a magnetic recording medium manufacturing apparatus. In this figure, 1 is a long polymer substrate, and 2 and 3 are a supply roll and a winding roll of the polymer substrate 1, respectively. Polymer substrate 1
During the traveling of the cylindrical can 4 in the traveling direction 5 of the cylindrical can 4, the vaporized atoms are accumulated. At this time, an entrance-side shield 6 and an exit-side shield 7 are provided between the evaporation source 8 and the cylindrical can 4, and the positions thereof are adjusted to adjust the initial incidence angle R1 and the final incidence of evaporated atoms to the polymer substrate 1. The angle R2 can be controlled. When the Co—O film is reactively vacuum-deposited, oxygen is introduced from the oxygen introduction nozzle 9 so as to obtain desired magnetic characteristics.

[0006]

When the nonmagnetic CoO underlayer and the Co—O magnetic layer are sequentially formed by the apparatus shown in FIG. 4, there is a problem in mass productivity because two vapor deposition steps are required. It was Also, impurities are mixed into the surface of the substrate or the underlayer or scratches occur, resulting in frequent dropouts.
There was a problem in completing it as a magnetic tape.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to manufacture a magnetic tape with less dropout with good mass productivity.

[0008]

When a magnetic layer containing Co and O as the main components is formed on a long polymer substrate by a continuous vacuum deposition method, oxygen is introduced into an initial incidence region of Co vapor. A non-magnetic CoO underlayer is formed, and then the magnetic layer is formed in the final incidence region.

[0009]

According to the method of the first aspect, the non-magnetic CoO underlayer and the Co-O magnetic layer can be formed in a single vapor deposition step, so that mass productivity is improved. In addition, non-magnetic Co
After forming the O underlayer, the surface of
Since the O magnetic layer is formed, the surface of the CoO underlayer is not mixed with impurities or scratched, and the dropout is reduced.

Generally, the amount of oxygen introduced to form the non-magnetic CoO underlayer is significantly larger than the amount of oxygen introduced to form the Co—O magnetic layer. Therefore, in order to form a Co—O magnetic layer having a large saturation magnetization, it is necessary to reduce the influence of the introduction of oxygen for forming the non-magnetic CoO layer on the formation of the Co—O magnetic layer. However, the oxygen introduction nozzle for forming the non-magnetic CoO underlayer is introduced toward the entrance side of the traveling of the polymer substrate from a nozzle arranged in the vapor incident amount region and close to the polymer substrate. Then, since the reactive vapor deposition is performed before the oxygen diffuses, the introduction amount of oxygen can be suppressed to the minimum.

Next, a magnetic tape formed by arranging an oxygen introducing nozzle for forming a non-magnetic CoO in a region on the entrance side of the polymer substrate where the density of the vapor flow is 2/3 or less of the highest value, and Auger spectroscopic analysis of a magnetic tape formed on the outlet side and a magnetic tape formed in two steps for comparison showed that the oxygen introduction nozzle for forming non-magnetic CoO had the highest vapor flow density. In the case of the magnetic tape formed in the area on the entry side of the polymer substrate having a value of ⅔ or less, the distribution of the oxygen abundance ratio in the film thickness direction is the same as the magnetic tape formed in two steps. It was also changing rapidly. On the other hand, in the case of the magnetic tape formed further on the output side, the change in oxygen distribution was gradual. That is, the oxygen introducing nozzle for forming non-magnetic CoO is formed in two stages by arranging the oxygen introducing nozzle for forming the non-magnetic CoO in a region on the inlet side of the polymer substrate where the vapor flow density is 2/3 or less of the highest value. Similar to the separately formed magnetic tape, a thin film having a clear boundary between the non-magnetic layer and the magnetic layer can be obtained. As a result, it was found that excellent magnetic characteristics and recording / reproducing characteristics equivalent to those of the conventional magnetic tape formed by the vapor deposition method divided into two stages can be obtained. Further, as a factor for obtaining such a result, the oxygen introduction nozzle for forming the non-magnetic CoO has a region on the inlet side of the polymer substrate in which the vapor flow density is ⅔ or less of the highest value. It is speculated that the vapor flow acts as a barrier and prevents the oxygen flow from diffusing to the more outflow side region.

[0012]

(FIG. 1) is a schematic view of an example of a magnetic recording medium manufacturing apparatus capable of carrying out the manufacturing method of the present invention (FIG. 4).
Is a continuous vacuum vapor deposition apparatus having a structure in which an oxygen introduction nozzle 10 for forming non-magnetic CoO is arranged between the shields of the above apparatus.
In the apparatus shown in FIG. 1, the non-magnetic CoO underlayer is formed on the polymer substrate 1 while traveling along the cylindrical can 4 in a region on the entry side of the nonmagnetic CoO underlayer forming layer 10. Then, subsequently, a Co—O magnetic layer is formed in the region on the more output side. Here, the oxygen introducing nozzle 10 for forming the non-magnetic CoO underlayer is arranged as close as possible to the can (FIG. 1).
Oxygen is blown out toward the entrance side of the polymer substrate as in the oxygen introduction direction 11 described therein. By doing so, the amount of oxygen introduced can be minimized as described above. In our study, less than half the amount of oxygen was introduced compared to the case where oxygen was introduced from above the entrance-side shield 6 toward the substrate running direction. Further, a shield may be provided between the oxygen introduction nozzle 10 for forming the non-magnetic CoO underlayer and the evaporation source 8 so that the outlet of oxygen is not blocked by the deposit during vapor deposition. On the other hand, the position of the oxygen introducing nozzle 9 for forming the Co—O layer does not have to be near the outlet shield 7 as shown in (FIG. 1). You may do it.

Oxygen introducing nozzle 10 for forming a CoO underlayer
The change of the magnetic characteristics when the position of is changed will be described. The positions of the entrance-side shield and the exit-side shield were fixed at an incident angle of 80 ° and 40 °, respectively. For comparison, the outgoing shield is moved to the position of the CoO underlayer forming oxygen introducing nozzle to form the CoO underlayer, then the outgoing shield is returned, and the incoming shield is used for forming the CoO underlayer. It was manufactured by a method divided into two steps of moving to the position of the oxygen introducing nozzle to form a Co—O layer. The feeding speed of the polymer substrate and the amount of oxygen introduced from the oxygen introducing nozzle for forming the Co—O layer are about 200 nm when the film is produced by a method divided into two steps, and the saturation magnetization is 450e
It was set to be mu / cc.

FIG. 2 shows the in-plane squareness ratio normalized by the values of the above-mentioned magnetic tape for comparison, which was prepared by dividing the oxygen introduction nozzle for forming the CoO underlayer into the same position twice.
It shows the relationship between the vapor flow density at the position of the oxygen introduction nozzle for forming the CoO underlayer during vapor deposition and the value normalized by the highest value. In the area on the inlet side where the vapor flow density standardized from (FIG. 2) is 2/3 or less, the in-plane squareness ratio is within 4%. However, it can be seen that the in-plane squareness ratio is remarkably deteriorated in the region on the output side. When the in-plane squareness ratio was deteriorated, the saturation magnetization of the entire tape was significantly reduced, and it was estimated that oxygen for forming the CoO underlayer was diffused to the outlet side. Further, even when the position of the oxygen introducing nozzle for forming the CoO underlayer is in the inlet side region where the standardized vapor flow density is 2/3 or less, the saturation magnetization was slightly decreased. It was possible to obtain the same saturation magnetization as that of the above-mentioned magnetic tape for comparison by readjusting the amount introduced from the oxygen introducing nozzle for forming the Co—O magnetic layer. At that time, the value of the in-plane squareness ratio reproduced the value of the comparative magnetic tape.

FIG. 3 shows the reproduction output of the magnetic tape whose magnetic characteristics are reproduced as described above, normalized by the value of the above-mentioned magnetic tape for comparison. A drum tester was used for the measurement. As shown in (Fig. 3), the reproduction output was almost reproduced.

Table 1 shows the results of measuring the dropout with a dropout counter by applying a commercially available VTR to a magnetic tape whose recording / reproducing characteristics are reproduced. As a dropout, output drop of -16 dB or more is 15μ
It was counted when it continued for more than sec. The magnetic tape manufactured once by the method of the present invention had a dropout of 40% or more less than the magnetic tape manufactured twice. This is because scratches and stains on the tape surface were reduced by simplifying the process.

[0017]

[Table 1]

Incidentally, such a result was similarly obtained when the incident angle was different, for example, when the incident angle was nearly vertical. However, when the incident angle was close to vertical, the squareness ratio was compared by demagnetizing the magnetization curve in the vertical direction.

Generally, when a magnetic layer is vapor-deposited, the magnetic characteristics and recording / reproducing characteristics of the magnetic layer change depending on the incident angle of vapor-deposited atoms. In the vapor deposition apparatus shown in FIG. 1, the initial incidence of the magnetic layer. The angle is defined by the position of the oxygen introduction nozzle for forming the non-magnetic CoO underlayer, and the intermediate incident angle R3 in FIG.
Becomes In this case, the following procedure may be performed to obtain the desired intermediate incident angle R3. (1) An interval between shields is set sufficiently wider than a desired vapor deposition range centering right above an evaporation source, and vapor deposition is performed with a polymer substrate stopped on a can. (2) The volume of the deposit per unit area of the substrate is standardized to a value per unit area of the horizontal plane, the distribution in the substrate running direction is obtained, and this is used as the vapor flow density distribution. (3) 2/3 of the highest value of vapor flow density found in (2)
An initial incident position for forming a Co—O layer is defined in the area on the entry side of the polymer substrate below, and an oxygen introduction nozzle for forming a CoO underlayer is arranged. (4) If the desired initial incident angle cannot be obtained in (3), the evaporation source is moved.

The method for obtaining a desired initial incident angle for forming the Co-O layer has been described above. The final incident angle for forming the Co-O layer may be determined by the position of the shield on the output side.

Further, in our study, the incident angle at the time of forming the CoO underlayer did not significantly affect the magnetic characteristics of the upper Co--O layer, so that the ratio of the film thickness of the CoO underlayer and the Co--O layer is desired. It suffices to adjust the distance between the shield on the outlet side and the oxygen introducing nozzle for forming the CoO underlayer so that

[0022]

According to the manufacturing method of the present invention, magnetic characteristics and recording / reproducing equivalent to those of a magnetic tape having a non-magnetic CoO layer as a base and a Co-O layer as an upper layer, which are separately manufactured, are provided. 1 magnetic tape with characteristics and low dropout
It can be manufactured with good mass productivity in a single process.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a magnetic recording medium manufacturing apparatus capable of carrying out the manufacturing method of the present invention.

FIG. 2 is a graph showing the relationship between the in-plane squareness ratio and the vapor flow density at the position of the oxygen introduction nozzle for forming the CoO underlayer during vapor deposition.

FIG. 3 is a graph showing evaluation results of reproduction output of a magnetic tape manufactured by the method of the present invention.

FIG. 4 is a schematic view of an apparatus for manufacturing a magnetic recording medium used for manufacturing a conventional method.

[Explanation of symbols]

 1 Polymer Substrate 2 Supply Roll 3 Winding Roll 4 Cylindrical Can 5 Rotational Direction of Cylindrical Can 6 Entry Side Shield 7 Egress Side Shield 8 Evaporation Source 9, 10 Oxygen Introduction Nozzle 11 Oxygen Introduction Direction R1 Initial Incident Angle R2 Final Incident Angle R3 Intermediate incidence angle

Claims (3)

[Claims] 1. When a magnetic layer containing Co and O as main components is formed on a long polymer substrate by continuous vacuum deposition, C is used.
o A method of manufacturing a magnetic recording medium, wherein oxygen is introduced into the initial incidence region of vapor to form a non-magnetic CoO underlayer, and then oxygen is introduced into the final incidence region to form the magnetic layer. 2. Oxygen for forming a non-magnetic CoO underlayer is directed toward the running side of the polymer substrate from a nozzle arranged in the vapor incident amount region and close to the polymer substrate. The method for producing a magnetic recording medium according to claim 1, which is introduced as a method. 3. An oxygen introduction nozzle for forming a non-magnetic CoO underlayer has a vapor flow density of ⅔ of its highest value.
The method of manufacturing a magnetic recording medium according to claim 2, wherein the magnetic recording medium is arranged in the following region.