JPS61278033A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce the title magnetic recording medium having uniform magnetic characteristics with large capacity and at high speed by using a material consisting essentially of boron nitride for a vaporization source crucible contg. a ferromagnetic metal or a alloy. CONSTITUTION:A ferromagnetic material 12 for vapor deposition set in a crucible 1 consisting essentially of boron nitride is heated by an electron beam emitted from an electron beam generator 10 and vaporized to form a thin film of the ferromagnetic material 12 on a substrate 3 traveling along a substrate carrier 8 on a cylinder. Since boron nitride is a material resist and to the high temps. of about 3000 deg.C and having an extremely small thermal expansion coefficient and excellent stability to thermal shock which is suitable as the material of the vaporization source crucible, the vaporization crucible is hardly broken by a thermal cycle and hence the stability of the magnetic recording medium production is improved. Since boron nitride is also chemically inactive, a metallic melt is practically uncontaminated by the reaction of the nitride with the molten metal and the stability of the production is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a magnetic recording medium having a magnetic thin film, and more specifically, a method for manufacturing a magnetic recording medium that enables large-capacity, high-speed deposition and is suitable for mass production. Regarding.

"Prior Art" Magnetic recording media such as magnetic tapes and magnetic sheets are widely used in the audio and video fields. For example, magnetic tapes of this type are coated with ferromagnetic powder dispersed in a binder, but as the demand for island density recording has recently increased, the recording density has become smaller by the amount of binder. It has thicker saturation magnetization than the molded one (and it can be used directly without the need for a binder).
BACKGROUND ART Magnetic recording media in which a ferromagnetic metal thin film can be formed on a support by vapor deposition, sputtering, ion blating, etc. have come into widespread use.

One of the methods suitable for producing magnetic thin films on an industrial scale is the open air deposition method using electron beam heating. Conventionally, in this vapor deposition method using electron beam heating, a water-cooled copper hearth has been used as a crucible for the evaporation source, mainly in the semiconductor industry. However, when using a water-cooled copper hearth, although it has an excellent evaporation rate of Ill III of the evaporation material, it is not suitable for high-volume, high-speed evaporation of high-melting point metals used in the manufacture of magnetic recording media. .

Also, for manufacturing magnetic recording media, JP-A-58-18
No. 8335 proposes a crucible for an evaporation source containing zirconium oxide as a main component, but there are problems such as a reaction between the so-called stabilizer used together with zirconium oxide to stabilize sintering and the molten metal. It had the disadvantage of not being able to withstand repeated use.

Furthermore, in JP-A-58-1811, a crucible for evaporation source using a whisker-reinforced ceramic whose strength is increased by adding silicon nitride whiskers or silicon carbide whiskers to magnesium oxide or zirconium oxide is also being considered. Although there are some products with improved characteristics, they are not sufficient.

Furthermore, a crucible for evaporation source made of magnesium oxide is widely used as a crucible for high-speed deposition of ferromagnetic materials. Although magnesium oxide has a high melting point and is a crucible material with good heat resistance, it has a thermal expansion coefficient of 13,
Since it is relatively large at about 5×10° C., it has the disadvantage that it does not have sufficient durability and properties from the viewpoint of so-called thermal shock resistance, which is accompanied by rapid temperature compensation changes. This has caused a problem in that the evaporation source crucible is likely to be destroyed due to thermal cycles in the production process of magnetic recording media, resulting in poor production stability of magnetic recording media.

As mentioned above, none of the conventional crucibles for evaporation sources are satisfactory for high-speed deposition of magnetic recording media on an industrial scale, and it is desired to develop a crucible for evaporation sources that can withstand high-speed deposition of large mackerel. was.

[Objective of the Invention 1] The present invention has been made in view of the above circumstances, and the first object of the present invention is to perform C! ! It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that makes it possible to efficiently produce thin-film magnetic recording media on an industrial scale.

A second object of the present invention is to provide a method for manufacturing a magnetic recording medium that enables high-capacity, high-speed deposition.

The third object of the present invention is that even in long-term evaporation operations,
It is an object of the present invention to provide a method for manufacturing a magnetic recording medium having stable characteristics as an evaporation source.

A fourth object of the present invention is to provide a method for manufacturing a magnetic recording medium with excellent durability for repeated use of an evaporation source crucible.

[Structure of the Invention] The above object of the present invention is to provide a method for manufacturing a magnetic recording medium by evaporating a ferromagnetic metal or alloy by electron beam heating and forming a magnetic thin film on a substrate. Alternatively, the evaporation source crucible holding the alloy can be achieved by a method of manufacturing a magnetic recording medium containing II nitride as a main component.

[Specific Structure of the Invention] The composition of the evaporation source crucible containing boron nitride as a main component used in the production method of the present invention does not require that boron nitride be pure;
) Calcium II oxide (CaO), aluminum oxide (
A′)xO3) or the like may be added as appropriate. In the evaporation source crucible used in the present invention, boron nitride may be the main component as described above, but from the viewpoint of thermal shock resistance, boron nitride is preferably 85% to 100% by weight, and more preferably It is preferably 90% to 99% by weight.

Some of the nitride nitrides used in the evaporation source crucible used in the present invention have hexagonal and rhombohedral crystal structures.
There are no particular restrictions on the composition of these crystal structures.

The illumination nitride used in the present invention is a heat-resistant material that can withstand high temperatures of nearly 3000°C, and has a coefficient of thermal expansion of 4.
, 7 x 10 ℃, and has excellent thermal shock stability as an evaporation source crucible material, preventing the evaporation source crucible from breaking due to thermal cycles, resulting in improved stability in magnetic recording media production. It is something to do. In general, since boron nitride is scientifically inert, it is less likely to react with molten metal and cause contamination of the metal melt, contributing to the above-mentioned production stability.

As a method for manufacturing an evaporation source crucible containing boron nitride as the main component, boron nitride powder is molded by pressure molding using hydrostatic pressure.
A dry pressure molding method in which firing is performed in a nitrogen atmosphere up to 800°C is common, but 5% oxidized I obtained by reaction at 900°C is
#Nitride m* powder containing cords is heated at a pressure of 35 to 70 kg/
It can also be obtained by a so-called hot press method in which the temperature is kept at 11110°C to 190°C for 10 minutes.

FIG. 1 is a sectional view of essential parts of an example of an apparatus for carrying out the manufacturing method of the present invention. In the same figure, the inside of this li[ is hermetically sealed from the outside air by a vacuum chamber indicated by the symbol 1, and the inside of the vacuum chamber 1 is divided into a chamber for sending out and winding a non-magnetic substrate 3 by a counter spacer 12, and a chamber for feeding and winding a non-magnetic substrate 3, and a chamber for vapor deposition. Divided into chambers, vacuum chamber 1
An exhaust pipe 4 is provided at the bottom of the
Connected to AM5.

In the delivery/winding chamber, there is a delivery shaft 6.2 as a board running system.
It has two free rollers 7, a substrate support 8, and a winding shaft 9. The deposition chamber is equipped with an electron beam generator [1] as a deposition system.
The ferromagnetic material F412 for deposition set in 0, Ruppo 11, and Ruppo 11 are each affected, and an inlet 13 for introducing a reactive gas (for example, oxygen gas, etc.) is provided. There is.

In the above apparatus, the ferromagnetic material 12 for deposition set in the crucible 11 is heated and evaporated by the electron beam emitted from the electron beam generator 10.

The vapor stream is moved along a cylindrical substrate support 8 to form a film of ferromagnetic material 12 on the substrate 3-t.

It should be noted that it is optional to provide the apparatus shown in FIG. 1 with a mask plate (not shown) between the substrate support 8 and the crucible 11 so as to block a part of the vapor flow. It is also optional to introduce a reactive gas (for example, a rare gas such as argon, oxygen, nitrogen, carbon oxide, hydrogen, methane gas, etc.) into the reactor.

Examples of ferromagnetic metals, metals, or alloys used in the present invention include metals such as Fe, Qo, and Ni, Fe-Go,
Fe-Ni, Co-Ni, Fe-Go-N
i, Co-Cu, Co-Y, Co-Pr.

Go-8s, Go-Pt, Co-Cr
, Fe-8l, Co-8l, C,o-PlC
o -B, Go -V, CO-Ce, Co-W%CO
-Mn, CO-AQ, Co-Ni-PlCo-
Ni-B, Co-Ni-V, Co-Ni-8L
l11Co-Ni-Cr.

Co-Nl-Cu, Co-Ni
-Zn, Co-Nl-W, Co-8s-Cu
Examples include alloys such as

The substrate on which the thin film of the ferromagnetic material is formed is preferably a flexible substrate made of non-magnetic metal, paper, plastic, etc.
Examples of non-magnetic metals include aluminum, aluminum alloys, copper, zinc, tin, stainless steel, and titanium. Examples of plastics include cellulose acetate,
Cellulose nitrate, methylcelluloseamide, polymethyl methacrylate, polyparabanic acid,
polyetherimide, polyethersulfone, polyetheretherketone, polytetrafluoroethylene,
Polymers or copolymers of α-olefins such as polytrifluoroethylene, ethylene or propylene, polymers or copolymers of vinyl chloride, polyvinylidene chloride, polycarbonates, polyimides, polyesters such as polyethylene terephthalate, etc. .

[Specific Effects of the Invention] As explained above, in the manufacturing method of the present invention, by using an evaporation source crucible containing boron nitride as a main component that holds a ferromagnetic metal or alloy, the heat of the evaporation source crucible is reduced. It enables high-capacity, high-speed production of magnetic recording media with excellent impact stability and repeated use durability, small coercive force and output fluctuations, and uniform magnetic properties, and efficiency on an industrial scale. Production has become possible.

[Example 1] Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 Using the FISH@ apparatus shown in FIG.
(80:20) magnetic material is heated to 1600°C by electron beam heating to evaporate it, and at the same time oxygen gas is added to 1.
While introducing into the vacuum chamber with ON・i/■1n, the pressure is 6,
A thin film was formed at 5×10 Pa to a thickness of 1,500 layers. The materials constituting the evaporation source crucible used at this time were boron nitride 97.5% by weight, boron oxide <Fi20a
)' 2. ! i% by weight.

After 1 hour of vapor deposition, the tank was returned to the atmosphere.

The above vapor deposition operation was repeated 10 times, and the magnetic tape samples obtained each time were designated as A-1 to A-10, respectively.

Comparative Example 1 The evaporation source crucible used in Example 1 was
A magnetic tape sample was prepared under the same conditions as in Example 1 except that a saponified magnesium crucible (Mg098, 5i mass %) was used. Here, the evaporation source crucible cracked during the 5th evaporation operation, and it became unusable after the 7th evaporation operation. The magnetic tape samples obtained in each case were designated as B-1 to B-7, respectively.

The coercive force was measured on the magnetic tape samples A-1 to A-10, B-1 to B-7 obtained in Example 1 and Comparative Example 1'c above, and the results are shown in Figure 2. It is expressed as the rate of change (%).

Here, the rate of change in coercive force is a value expressed as the rate of change C per 1000 m of deposition length.

In addition, 172 magnetic tape samples were prepared for each
Slit to inch width and 4M H with VH'S type VTR
We investigated the Z output fluctuation. The results are shown in Figure 3.

As is clear from the above Examples and Comparative Examples, according to the method for manufacturing a magnetic recording medium of the present invention, the evaporation source crucible has excellent durability in repeated use, and the coercive force of the obtained magnetic recording medium is
The output fluctuation was also small.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view of the manufacturing device #1 used for carrying out the 111 manufacturing method of the magnetic recording medium of the present invention, and the Mg diagram shows an example of the manufacturing method of the present invention. Figure 3 shows the rate of change in coercive force of the magnetic sample tape obtained by the manufacturing method (represented by A) and the magnetic sample tape obtained by the comparative manufacturing method (represented by B). Figure 3 shows the same output as Figure 2. It is a diagram showing fluctuations. 1... Vacuum chamber, 3... Substrate, 10.
...Electron beam generator 7+ device 11...Evaporation source crucible 1
2...Ferromagnetic 44 Sum 113...Reactive gas inlet Figure 1 (No.

Claims (1)

[Claims] In a method for manufacturing a magnetic recording medium by evaporating a ferromagnetic metal or alloy by electron beam heating to form a magnetic thin film on a substrate, the evaporation source crucible holding the ferromagnetic metal or alloy is made of boron nitride. A method for manufacturing a magnetic recording medium, characterized in that the main component is.