JPH033118A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics and durability by forming a vapor deposition layer by an oblique deposition method in an oxygen-contg. atomsphere while the minimum incident angle of deposition is regulated by a mask edge, and then forming another deposition layer in an oxygen atomsphere with using a slit provided at a position downstream in the production line. CONSTITUTION:A mask 3 is provided between a magnetic material 6 as a vapor source and a nonmagnetic supporting body 2 which runs on a can 1. The mask has a slit 4 at the position downstream along the running direction of the nonmagnetic supporting body 2. The distance l1 between the nonmagnetic supporting body 2 and the oxygen feeding nozzle 5a, and the distance l2 between the nozzle 5a and the vapor source 6 are determined to satisfy l1/l2>=1/20. Oxygen and vapor flow S from the magnetic material 6 produced by heating with an electron gun 8 are mixed and made to deposite on the surface of the nonmagnetic supporting body 2 which continuously runs. Thus, the first vapor deposition layer is formed. Then vapor flow S and oxygen feeding nozzle 5b and mixed and deposited to form the second layer on the first deposition layer.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a method for depositing on a non-magnetic support by performing oblique evaporation in an oxygen-containing atmosphere through a mask between an evaporation source and a non-magnetic support. The present invention relates to a method of manufacturing a magnetic recording medium in which a magnetic thin film is formed, and particularly to a method of improving both electromagnetic conversion characteristics and durability.

[Summary of the invention]

The present invention is a magnetic thin film that forms a two-layered magnetic thin film on a non-magnetic support by performing oblique evaporation in an oxygen-containing atmosphere through a mask between an evaporation source and a continuously running non-magnetic support. A method for manufacturing a recording medium, which provides good electromagnetic conversion characteristics by regulating the oxygen introduction position when forming a first magnetic layer and adjusting the mixing ratio of steam generated from an evaporation source and oxygen to an appropriate level. Good durability is achieved by ensuring that the angle of incidence of vapor when forming the second magnetic layer is smaller than when forming the first magnetic layer, and setting the oxygen concentration sufficiently high. This is what I am trying to do.

[Conventional technology]

In recent years, in response to the demand for high-density recording and high-speed recording, Co
- Plating and vacuum thin film formation technology (vacuum evaporation, sputtering) of ferromagnetic metal materials such as Ni alloys.

A so-called metal thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as polyester or polyethylene terephthalate (PET) by ion blating, etc., has been proposed and put into practical use.

Metal thin film type magnetic recording media have high coercive force and squareness ratio,
It has excellent electromagnetic conversion characteristics in the short wavelength range, and since the magnetic layer can be formed thin, recording demagnetization and thickness loss during reproduction can be effectively reduced, and since the magnetic layer does not contain an organic binder, it can be used as a magnetic material. It has a number of advantages, such as being able to increase the packing density. In particular, when forming the magnetic layer, so-called oblique deposition, in which the magnetic material is deposited at a predetermined angle with respect to the surface of the non-magnetic support, grows a metal structure with a high acicular ratio, resulting in excellent electromagnetic properties. It is known that conversion properties can be achieved.

However, since the magnetic layer of metal thin film magnetic recording media is mainly composed of metal materials, cracks occur in the magnetic layer under high temperature, high humidity, or corrosive environments, causing problems such as saturation magnetization and coercive force. There are problems in that durability tends to deteriorate, such as deterioration over time or deterioration of the mechanical strength of the magnetic layer. Furthermore, when the magnetic layer is formed by oblique vapor deposition, the formed metal structure has a column shape grown in an oblique direction, which also causes a decrease in durability.

The easiest way to prevent a decrease in durability is to form a protective film on the surface of the magnetic layer by applying a rust preventive agent or the like. However, in this method, the magnetic layer comes into sliding contact with the magnetic head through the nonmagnetic protective film, so there is a risk that the electromagnetic conversion characteristics will deteriorate due to so-called spacing loss.

In order to avoid such problems, attempts have been made to make the magnetic layer have a multilayer structure, or to form a thin surface oxide film on the surface of the magnetic layer by forming the magnetic layer in an oxygen-containing atmosphere. For example, the applicant of this application previously
In Japanese Patent No. 9-107429, a non-magnetic support is wound around two cans arranged close to each other, and the modification is carried out by performing oblique evaporation on each can while performing ion bombardment with oxygen ions. This disclosure discloses a method for manufacturing a magnetic recording medium in which two magnetic layers are stacked.

(Problems to be Solved by the Invention) The above-mentioned manufacturing method is expected to have a corrosion-resistant effect on the second magnetic layer formed on the surface side, but even with this technique, the metal structure grows in a diagonal direction. Since it is still column-shaped, it is difficult to say that sufficient corrosion resistance has been achieved.'Also, when forming a magnetic layer in an oxygen-containing atmosphere, it is difficult to control the oxygen concentration. If the oxygen concentration is too high, the entire magnetic layer will be oxidized and the electromagnetic conversion characteristics will deteriorate, while if the oxygen concentration is too low, the thickness of the surface oxide film will be insufficient and the desired durability will not be achieved.

Furthermore, there are other problems such as the need for multiple cans and means for supplying oxygen ions, making the device larger and more complex.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a magnetic recording medium having excellent electromagnetic conversion characteristics and durability using a simple apparatus.

[Means for Solving the Problems] The present invention is proposed to achieve the above-mentioned objects. That is, in the method for manufacturing a magnetic recording medium according to the present invention, a mask is provided between an evaporation source and a continuously running non-magnetic support, in which a slit is formed midway on the downstream side of the non-magnetic support in the running direction. , the distance 1° from the non-magnetic support to the oxygen inlet and the distance 12 from the oxygen inlet to the evaporation source are l l/j! By setting the relationship t≧1/20 and performing oblique deposition in an oxygen-containing atmosphere while defining the minimum incident angle using the tip of the mask, the first
After the vapor deposition layer is formed, a second vapor deposition layer is formed on the first vapor deposition layer while introducing oxygen through the slit.

[Function] In the present invention, the first vapor deposition layer is formed mainly of the component protruding from the tip of the mask among the vapor of the magnetic material generated from the vaporization source, and A second vapor deposited layer is formed mainly from components that enter from the substrate.

Both of these vapor deposited layers are formed in an atmosphere containing oxygen, but in particular, when forming the first vapor deposition layer, by separating the opening position of the oxygen inlet by a certain distance or more from the surface of the non-magnetic support, the magnetic material can be formed. It becomes possible to appropriately control the mixing ratio of steam and oxygen and prevent the oxygen concentration from increasing beyond a certain level. Therefore, the first deposited layer is not excessively oxidized and the electromagnetic conversion characteristics are not impaired. On the other hand, when forming the second vapor deposited layer, the minimum incident angle of vapor becomes smaller than when forming the first vapor deposited layer, and oxygen is introduced near the surface of the nonmagnetic support, so that the atmosphere Oxygen concentration becomes relatively high. Therefore, the second vapor deposited layer has a structure whose growth direction is closer to perpendicular to the layer thickness direction than that of the first vapor deposited layer, and is a dense oxide film with high corrosion resistance.

In the present invention, since oblique deposition is performed through a mask having a slit in the middle of the downstream side in the direction of movement of the nonmagnetic support, the first deposited layer has excellent electromagnetic conversion characteristics, and the second deposited layer has excellent durability. evaporated layers of the same magnetic material can be successively formed in a single process.

[Examples] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First, a part of the vacuum evaporation apparatus used in this example is shown in FIG.

The vacuum evaporation apparatus includes a can (1) whose temperature is controlled near 0° for winding and running a non-magnetic support (2), a can (1) disposed along a part of the outer periphery of the can (1), and By providing a slit (4) in the middle, vapor flows St, St are generated from the magnetic material (6) at a predetermined angle of incidence.
(Actually, the mask (3) is used to make the mixed airflow with oxygen reach the surface of the non-magnetic support (2), and the oxygen introduction to introduce the oxygen gas mixed into the steam fis+ and sg. It consists of tubes (5a), (5b), a crucible (7) containing a magnetic material (6), an electron gun (8) for heating the magnetic material (6), and other components for cooling the can. cooling system, supply roller, take-up roller, chamber, oxygen supply source.

It is equipped with an exhaust system, etc. (none of which are shown).

The arrangement position of the oxygen introduction pipe (5a) is as follows:
The distance from the center of the opening in 5a) to the surface of the non-magnetic support (2) is f+, and the distance to the surface of the magnetic material (6) is 1.
1, i, /ffi! It is selected so that ≧1720. Although the oxygen introduction tube (5a) is formed integrally with the mask (3) in FIG. 1, it may be an independent member from the mask (3) as long as the above conditions are met. On the other hand, the oxygen introduction pipe (5b)
It is desirable that the opening be provided sufficiently close to the surface of the non-magnetic support (2).

The process of forming the first vapor deposited layer and the second vapor deposited layer using such an apparatus is as follows.

First, a 6n material (
The steam flow S1 generated from 6) rises and passes through the oxygen introduction pipe (
When the oxygen introduction pipe (5a) reaches the vicinity of the opening of the oxygen introduction pipe (5a),
a) mixed air flow M mixed with oxygen gas released from
becomes. This mixed air flow M reaches at a predetermined angle of incidence the surface of the non-magnetic support (2) that is continuously traveling while being wound around the can (1) rotating in the direction shown by T in the figure, and is cooled here. The first vapor deposited layer [see Fig. 2 (
10) See. ] to form.

However, all incidence angles mentioned in this specification refer to inclinations from the normal line of the nonmagnetic support (2). Furthermore, in such oblique deposition, since the incident angle differs depending on the incident position, the angle when the mixed air flow M1 is incident on the most upstream side when viewed from the running direction of the non-magnetic support (2) is defined as the maximum incident angle θlLl+ The angle at which the light enters the downstream side is defined as the minimum incident angle θ,L. Furthermore, the maximum incident angle θ2u and the minimum incident angle θ1 are similarly defined for the mixed gas flow Mt of the vapor flow S2 and oxygen.

In this way, the above-mentioned air mixture flow M has a predetermined incident angle θ1. Because of the contact at ~θII+, the formed first vapor deposited layer has a directionality that is continuously tilted with respect to the layer thickness direction, and this also determines the electromagnetic conversion characteristics. In order to optimize the electromagnetic conversion characteristics, the maximum incident angle θ1u of the air mixture M is 70 to 90
°, and the minimum incident angle θ, L regulated by the tip (3a) of the mask (3) is preferably selected to be 30 to 80'.

By the way, the mask (3) has a non-magnetic support (2).
There is a pickpocket (4) midway on the downstream side of the running direction.
is provided. Therefore, the vapor flow S2 generated from the magnetic material (6) rises and passes through the pipe (4), and when it reaches the vicinity of the opening of the oxygen introduction pipe (5b), the oxygen introduction pipe (5b) The gas is mixed with oxygen gas released from the air to form a mixed gas flow M2. Since the oxygen inlet (5b) is located closer to the surface of the non-magnetic support than the oxygen inlet pipe (5a), this mixed air flow M,
The oxygen concentration therein is higher than in the case of the above-mentioned mixed air flow M+. When the non-magnetic support (2) on which the first vapor deposited layer is formed runs into such an atmosphere, a mixed air flow M! is the given angle of incidence θ! , with ~θ211 the first
reaches the surface of the vapor deposited layer, precipitates and forms the second vapor deposited layer [second
See (11) in the figure. Since this second vapor deposited layer is provided for the purpose of rustproofing the first vapor deposited layer, it is necessary to form a dense structure in which the growth direction is as close to perpendicular to the in-plane direction as possible. Therefore, the maximum angle of incidence θ2. of the air mixture M2. is preferably 60° or less, and the minimum incident angle θ2L is preferably selected in the range of -30 to 60''.

These incident angles can be adjusted by changing the formation position and width of the slit (4).

As shown in FIG. 2, the magnetic recording medium manufactured in this way has a first vapor deposition layer (10
) and the second vapor deposition 1 (11) are stacked in this order. Since these vapor deposited layers are formed by oblique vapor deposition, the growth direction of the composite fibers is all continuously inclined with respect to the layer thickness direction. The layer is dense and has high vertical alignment.

The vacuum evaporation method applied in this example is electron beam evaporation in which the evaporation source is heated by an electron beam generated from the electron gun (8) as described above. This method is excellent in operability, has a high deposition rate, and is practically suitable in that it can improve the magnetic properties of the magnetic layer, such as coercive force and anisotropic magnetic field. However, the vapor deposition method applied to the present invention may be other conventionally known methods such as resistance heating vapor deposition, induction heating vapor deposition, ion beam vapor deposition, ion blating, laser beam vapor deposition, arc discharge vapor deposition, etc.

Furthermore, as the material for the non-magnetic support used in the present invention, any material that is normally used for this type of magnetic recording medium can be used, and it can also be used to improve adhesion and flatness. 1. Surface treatment or pretreatment may be appropriately performed for the purpose of coloration, antistatic properties, and improvement of abrasion resistance.

Furthermore, as a magnetic material used in the present invention,
Materials normally used for this type of magnetic recording medium can be used. In any case, in the present invention, since the first vapor deposited layer and the second vapor deposited layer are formed continuously in a single process and from the same magnetic material, the adhesion between the eyebrows is extremely high. Become.

Using the method described above, a sample tape was actually prepared according to the following procedure.

Examples 1 to 3 As shown in Table 1 below, the oxygen inlet (5a), (
While changing the oxygen flow rate introduced from 5b) and the value of Il,/i□, the maximum incident angle θIkl of the mixed vapor M, is set to 9
0' The first vapor deposition layer with a layer thickness of 2000 is formed with the minimum incidence angle θ and L as 45°, and then the maximum incidence angle θtl of the mixed vapor M2 is set as 2003. Similarly, the minimum incidence angle θ2L is set as lO
A second vapor-deposited layer having a thickness of 200 layers was sequentially formed as sample tape.

Comparative Example 1 For comparison, a sample tape without the second vapor deposition layer was prepared.The slit (4) was closed and the vapor flow S! was blocked.

Comparative Example 2 For comparison, the second vapor deposition layer was not formed, and 2. A sample tape was prepared by selecting a value of /12 outside the range specified in the present invention.

Expressed as main output attenuation (dB).

The results are shown in Table 1.

(The following is a blank space) Regarding each sample tape created in the above examples and comparative examples, electromagnetic conversion characteristics and durability were examined.

The electromagnetic conversion characteristics are the playback output (dB) and S/
The N ratio was measured and expressed as a relative value when compared with the coated metal tape.

As for durability, still durability and shuttle durability were measured. Still durability is expressed as the time (minutes) until the playback output decreases by 3 dB when the sample tape is held in a paused state. In Examples 1 to 3, good values were achieved for both electromagnetic conversion characteristic durability. These sample tapes have no major difference in durability because the second vapor deposition layer is all formed under the same conditions, but the first
Due to the difference in oxygen concentration during the formation of the deposited layer, there are slight differences in electromagnetic conversion characteristics. That is, between Example 1 and Example 2, the latter has a lower oxygen concentration due to the selection of the oxygen flow rate, and between Example 1 and Example 3! ,
Depending on how the value of /2□ is selected, the latter has a lower oxygen concentration, and better characteristics are obtained in each of the latter. This suggests that it is necessary to appropriately control the oxygen concentration in order to obtain good electromagnetic conversion characteristics.

On the other hand, in Comparative Example 1 and Comparative Example 2, the oxygen concentration was set high when forming the first vapor deposition layer instead of providing the second vapor deposition layer, but this deteriorated the im conversion characteristics. Moreover, the durability (especially still durability) is also insufficient. especially! l/l! Comparative example 2 with the value of l/25
It is clear that the electromagnetic conversion characteristics deteriorate significantly as the oxygen concentration increases.

(Effects of the Invention) As is clear from the above explanation, by applying the present invention, it is possible to create a magnetic recording medium that is excellent in both electromagnetic conversion efficiency and durability, and can meet the demands for high-speed recording and high-density recording. It becomes possible to manufacture with high productivity and economy.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a vacuum evaporation apparatus used when applying the method of manufacturing a magnetic recording medium according to the present invention. FIG. 2 is an enlarged sectional view of a main part showing the structure of a magnetic recording medium manufactured by applying the present invention. 1... Can 2... Non-magnetic support... Mask Figure 1 Slit oxygen introduction tube First vapor deposited layer Second vapor deposited layer

Claims (1)

[Claims] A mask having a slit formed midway on the downstream side in the running direction of the non-magnetic support is provided between the evaporation source and the continuously running non-magnetic support, and oxygen is introduced from the non-magnetic support. Distance l_1 to the mouth and distance l_1 from the oxygen inlet to the evaporation source
The first vapor deposition layer was formed by performing oblique vapor deposition in an oxygen-containing atmosphere while setting l_1/l_2 ≧ 1/20 and defining the minimum incident angle by the tip of the mask. A method for manufacturing a magnetic recording medium, further comprising: forming a second vapor deposition layer on the first vapor deposition layer while introducing oxygen through the slit.