JPS62103851A - Production of vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the cracking on the surface of a magnetic layer by specifying the ratio between gas having low chemical activity and gaseous oxygen to >=5vol% and <15vol% oxygen concn. and using Co as an essential component for a ferromagnetic material constituting an evaporation material. CONSTITUTION:The ratio between the gas having the low chemical activity and gaseous oxygen is specified to >=5vol% and <15vol% oxygen concn. and the Co is used as the essential component for the ferromagnetic material constituting the evaporation material in a process for producing the magnetic layer having magnetic anisotropy in the perpendicular direction on a substrate by simultaneously introducing the gas having the low chemical activity and gaseous oxygen into a vacuum atmosphere, using a ferromagnetic material as the evaporating material and executing vacuum deposition. The gas having the low chemical activity has preferably <=10kcal/mol heat of chemisorption of the evaporating material to the ferromagnetic material; more specifically, 1 or >=2 kinds of gases selected from N2, Ar, He, Ne, Xe, and Rn and used. The generation of the cracking in the surface of the magnetic layer is thereby eliminated and the excellent magnetic characteristics in the perpendicular direction are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of manufacturing a perpendicular magnetic recording medium by a vacuum evaporation method.

[Prior Art] A Co-based perpendicular magnetic recording medium consisting of a two-phase mixed state of Co particles and non-ferromagnetic Co particles has been proposed using CO in a vacuum atmosphere with oxygen gas introduced by an electron beam evaporation method. (Collection of Abstracts of the 7th Academic Lectures of the Japan Society of Applied Magnetics, 7
aA-9-7 aA-8, 1983, 11).

Since the above manufacturing method is a vacuum evaporation method, the film formation rate is fast, the composition can be easily controlled, and there is no need to heat the substrate during evaporation. However, there were drawbacks such as pressure fluctuations due to the getter action, variations in the magnetic properties and film thickness in the longitudinal direction of the film, and cracks in the magnetic layer.

In order to solve the drawbacks of the above manufacturing method, the present inventors used a gas with low chemical activity and oxygen gas, introduced both gases at the same time, and set the pressure at the time of gas introduction to 1 x 10
A method of vacuum deposition at -31'orr to 5 x 10-2 Torr was previously proposed (Japanese Patent Application No. 59-214412).

[Problems to be Solved by the Invention] However, even in the above-mentioned improved manufacturing method, there was a problem in that very fine continuous cracks were generated which could not be seen with a low-magnification microscope.

The above-mentioned fine cracks are not a problem when the recording density is low, but when the recording density becomes high, the
An error or a drop error occurs, and a solution to this problem has been long awaited.

The object of the present invention is to solve the above problems. That is, it is an object of the present invention to provide a method for manufacturing a perpendicular magnetic recording medium that is free from cracks on the surface of the magnetic layer and has excellent magnetic properties.

[Means for resolving problems using VE] The present invention has the following configuration. In other words, the present invention simultaneously introduces a gas with low chemical activity and oxygen gas into a vacuum atmosphere, uses a ferromagnetic material as an evaporation material, and forms a magnetic layer having vertical magnetic anisotropy on a substrate by vacuum evaporation. In the manufacturing method, the ratio of the less chemically active gas to oxygen gas is 5% by volume or more and less than 15% by volume in terms of oxygen concentration,
The main component of the ferromagnetic material that makes up the above evaporation family 4111 is Co.
A method for manufacturing a perpendicular magnetic recording medium, characterized in that:

In the present invention, the gas with low chemical activity refers to evaporation (A
It is a gas that is not adsorbed to the ferromagnetic material, or a gas that is adsorbed at a slow rate, and the heat of chemical adsorption to the ferromagnetic material, which is the evaporation vJ material, is 10 Kcal/m at the lowest temperature.
It is preferable to use a gas of less than o l, specifically, N2, Ar
, He, Ne, Xe, one or two types carried from Rn
It is desirable to use more than one species of gas. Furthermore, N2 and Ar are most suitable for use on an industrial scale because they are easily available and inexpensive. “In the present invention, the ratio of the less chemically active gas to the oxygen gas must be within the range of 5% by volume or more and 15% by volume of oxygen.If the oxygen concentration is less than 5% by volume, the coercive force in the vertical direction will decrease. At 15% by volume or more, fine cracks may occur in the magnetic layer.

The evaporation material used in the manufacturing method of the present invention is mainly composed of Co, which is a ferromagnetic material, but Fe or N is added to adjust the magnetic property values and improve wear resistance, corrosion resistance, etc.
1 etc. may be added.

However, vertical coercive force (Ho1), anisotropic magnetic field (HK)
And so on! Therefore, the proportion of Co in the evaporated material is desirably 80% or more, more desirably 90% or more.

Substrates that can be used in the present invention include, but are not particularly limited to, metals such as aluminum, copper, iron, and stainless steel, and organic polymer materials such as plastic films. In particular, when workability, moldability, and flexibility are important, PAff1 composite material 1 is suitable, and among them, polyethylene naphthalene 1~
, polyesters such as polyethylene naphthalene-1~, polyethylene dihydropoxylate, polyethylene α, B-his(2-chlorophenoxy)ethane-4,4-cycarboxylate 1~, polyolefins such as polyethylene, polypropylene, polybutene, polymethyl methane, etc. acrylic
To 1, polycarbonate, polysulfone, polyamide,
Aromatic polyamide, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyimide,
Alternatively, mixtures and copolymers of these are suitable.

In particular, biaxially stretched films and sheets are most suitable due to their excellent flatness and dimensional stability, and among them polyester,
Polyphenylene sulfide, aromatic polyamide, etc. are most suitable. The shape of the base body may be a drum shape, a disk shape, a sheet shape, a tape shape, a card shape, etc., and the thickness is not particularly limited. In the case of sheet shapes, tape shapes, card shapes, etc., the thickness is preferably in the range of 2 μ to 500 μ, particularly 4 μ to 200 μ, in terms of workability and dimensional stability.

Prior to the formation of the magnetic layer described below, the substrate used in the present invention is subjected to various surface treatments and pretreatments for the purpose of facilitating adhesion, improving flatness, coloring, preventing static electricity, imparting wear resistance, etc. It's okay.

The vacuum evaporation methods described in the present invention include resistance heating evaporation, induction heating evaporation, electron beam evaporation, ion blating,
Vacuum deposition methods such as ion beam evaporation, Rayleigh beam evaporation, and arc discharge evaporation can be used; Methods such as electron beam evaporation and ion blating are suitable in order to obtain a film forming rate, and electron beam evaporation is most suitable from an industrial viewpoint such as ease of operation and mass production.

Next, an example of the manufacturing method of the present invention will be explained based on the drawings. FIG. 1 shows an example of an electron beam evaporation apparatus for carrying out the manufacturing method of the present invention. In FIG. 1, an unwinding shaft 1, a nip roll 2, a main drum 3, a nip roll 4, and a take-up shaft 5 constitute a running system for a long film 6 made of an organic polymer. An organic polymer film 6 wound into a roll is disposed on an unwinding shaft 1. The film 6 passes through the nip roll 2, the main drum 3, and the nip roll 4, and is then wound onto a winding core disposed on a winding shaft 5. The main drum 3 has a cooling function (not shown), for example, by passing water to keep the back surface of the organic polymer film 6 at 50'C or less.
have. Reference numeral 14 denotes a partition wall, and the partition wall 14 divides the vacuum tank 10 into an upper tank 15 and a lower tank 16, each of which is evacuated through exhaust ports 11 and 12, respectively. 7 is a shielding plate for limiting the angle of incidence of the evaporative vapor flow. The angle of incidence is the angle θ between the evaporated vapor flow A incident on the substrate surface C and the normal line B to the substrate surface C in FIG. The shielding plate 7 in FIG. 1 has an opening 17 to prevent the evaporated vapor flow from entering the substrate surface beyond a selected angle of incidence of 45 degrees or less. 8 is an electron beam evaporator having a recessed portion.

Although the above apparatus is used to form a perpendicular magnetic recording medium by the manufacturing method of the present invention, it is not limited to the above apparatus.

A long film made of an organic polymer material, such as a polyethylene terephthalate film, is disposed in the long film running system of the vapor deposition apparatus shown in FIG. The vacuum chambers 10 are evacuated through exhaust ports 11 and 12, respectively. Upper tank 15 has a pressure of 5 x
The pressure near the base of the lower tank is 5X10-5T until it becomes 10'Torr or less.

Each is evacuated until it becomes below rr.

Next, a gas with low chemical activity and oxygen gas are pumped through the barrier pull leak valve 13 until the pressure near the substrate is 1 x 10.
It is introduced into the vicinity of the substrate through the introduction pipe 18 so as to achieve a predetermined pressure within the range of 'Torr to 5 x 10-'' Torr. For example, Co is melted and evaporated thereon by electron beam evaporation to continuously form a magnetic layer having magnetic anisotropy in the perpendicular direction.

Gases with low chemical activity and oxygen gas introduced into the vacuum layer have a pressure near the substrate of 1X10-3 at the time of introduction.
When outside the range of x 10-2 Torr, the anisotropic magnetic field decreases on the low pressure side, the evaporation rate decreases on the high pressure side, and the vertical coercive force also decreases.

In order to further improve the magnetic properties and obtain a high deposition rate, the pressure near the substrate must be between 2 x 10-3 Torr and 2 x 1
A range of 0-2 Torr is desirable.

The thickness of the magnetic layer obtained by the manufacturing method of the present invention is:
Although not particularly limited, practically 0.03 μm or more
The range is 5 μm, and when considering flexibility, contact with the magnetic head, and film formation speed of the magnetic layer, it is 0.05 μm.
A range of ~2.0 μm is desirable.

[Function of the invention] FIGS. 3 and 4 are surface electron micrographs (magnification: 5000 times) of a magnetic layer not according to the present invention, and FIG. 5 is a surface electron micrograph (magnification: 5000 times) of a magnetic layer according to the present invention. times).

Although the cracks that occur in the magnetic layer have not been fully elucidated, the following points have become clear as a result of intensive study by the inventors.

In other words, when a ferromagnetic material is vacuum-deposited without introducing gas, or when a ferromagnetic material is vacuum-deposited by introducing only oxygen gas, wide macroscopic cracks as shown in Figure 3 occur. . On the other hand, when a ferromagnetic material is vacuum-deposited by introducing only a gas with low chemical activity such as nitrogen gas or Ar gas, no cracks occur at all. However, in this case, the perpendicular coercive force and anisotropy field of the obtained magnetic layer are significantly reduced, making it impossible to form a so-called perpendicularly magnetized film. In addition, when a ferromagnetic material is vacuum-deposited by simultaneously introducing the same amount of a gas with low chemical activity such as nitrogen gas and oxygen gas,
A perpendicularly magnetized film can be formed, and macroscopic cracks do not occur. However, as shown in FIG. 4, narrow, fine and continuous cracks occur. The degree and occurrence tendency of fine and continuous cracks are correlated with the ratio of chemically active gas to oxygen gas and the supply amount, and as shown in the production method of the present invention, when the oxygen concentration is 5% by volume or more If the gas composition is within a range of less than vol. %, a perpendicular magnetic recording medium with no cracking at all and sufficient perpendicular coercive force and magnetic anisotropy can be obtained, as shown in FIG. The crack-free magnetic layer was examined using a cross-sectional transmission electron microscope (B!). The observed results show that the columnar structure becomes finer at a rate of /v, and it is presumed that the internal stress of the magnetic layer is alleviated by this finer columnar structure, thereby suppressing the occurrence of cracks.

[Method for measuring characteristics/Evaluation basis Q=] ■ Method for confirming the occurrence of cracks in the magnetic layer Confirm the presence or absence of cracks in the magnetic layer using a scanning electron microscope (manufactured by Akashi Seisakusho Co., Ltd., 15I-DS130, scanning electron microscope)
The photograph of the surface of the magnetic layer is taken by
0000 times) to confirm the presence or absence of cracks.

■ Method for measuring coercive force and anisotropic magnetic field The magnetic properties of the magnetic layer can be measured by the vibrating sample magnetometer method specified in JIS (, -2561) or the self-recording magnetic flux h4 method. was measured using a moving sample magnetometer (manufactured by Riken Denshi Co., Ltd., BHV-30).

(2) Control of inlet gas flow port and measurement of flow rate The flow rate of gas introduced into the vacuum chamber was controlled by a combination U of a mass flow control valve and a gas flow rate control valve. Specifically, a "mass flow controller" (SEC series) manufactured by Estech Co., Ltd. was used.

[Example] An embodiment of the manufacturing method of the present invention will be described below based on an example.

Examples 1 to 4, Comparative Examples 1 to 4 Upper tank pressure and lower II of the electron beam evaporation apparatus shown in FIG.
The pressure near the base is 5 x 10-4 Torr or less, 1
x 10-5 Torr or less, then a mixed gas of nitrogen and oxygen was introduced into the lower tank through the barrier pull leak valve, and a biaxially stretched polyethylene terephthalate film with a thickness of 50μ was run at a predetermined running speed. The magnetic recording layer is continuously formed on the film by melting and evaporating Go by electron beam evaporation. A shielding plate having a frontage such that the incident angle of the evaporated vapor flow is 26 degrees or less is disposed inside the electron beam evaporation apparatus, and the back surfaces of the polyethylene terephthalate films 1 to 5
It was cooled by the main drum to below °C. The electron beam evaporator is EGL-110 manufactured by Japan Vacuum Technology Co., Ltd.
HP-1610F manufactured by Japan Vacuum Technology Co., Ltd. was used as a power source for the electron beam evaporator. C○ with a purity of 99.9% or more was used for the electron beam evaporation type recess.

Example 1 shows an example in which a magnetic layer was formed by the above-mentioned manufacturing method by changing the composition of the introduced gas, a mixed gas of nitrogen and acid N or argon and oxygen, so that the oxygen concentration was in the range of 5% or more and less than 15%. ~4. Comparative Examples 1 to 4 are examples in which magnetic layers were formed in the same manner except that the gas composition was outside the range shown above.

The pressure near the substrate in Examples 1 to 4 and Comparative Examples 1 to 4 was 1x 1
It was within the range of 0 Torr to 5 x 10' Torr, and each example used the amount of gas introduced as a parameter.

The thickness of the magnetic layer was adjusted by changing the running speed of the polyethylene terephthalate film, which is a sea urchin substrate. In addition, Examples 1 to 4, Comparative Example 1
The power input to the electron beam evaporator in steps 4 to 4 was constant at W.

Tables 1 to 4 regarding the type of gas introduced in Examples 1 to 4, oxygen concentration, perpendicular coercive force and anisotropic magnetic field of the magnetic layer 1q with the gas introduction group, and the presence or absence of cracks on the surface of the magnetic layer. Shown below. Comparative Examples 1 to 4 are also shown in Tables 5 to 8.

As is clear from Tables 1 to 4, according to the 3h method of the present invention, there are no minute cracks on the surface of the magnetic layer, and the magnetic properties have magnetic anisotropy in the perpendicular direction, making it possible to record perpendicular magnetic recording. A magnetic recording medium suitable for high-density recording, which is the objective of this method, was obtained.

On the other hand, as is clear from Tables 5 and 6, Comparative Examples 1 and 2
Although the magnetic properties in the perpendicular direction are excellent, there are continuous fine cracks on the surface of the magnetic layer, and in Comparative Example 3 where only oxygen gas is introduced, there are macroscopic cracks on the surface of the magnetic layer as shown in Table 7. There was an occurrence of As shown in Table 8, in Example 4 with a low oxygen concentration, no cracks occurred on the surface of the magnetic layer, but the magnetic properties were poor, and Comparative Examples 1 to 4 were not put to practical use as perpendicular magnetic recording media for the purpose of high-density recording. It was difficult to serve.

Table 1: Example 1 Introduced gas: N2102, oxygen concentration 14% Table 2: Example 2 Introduced gas: N2102, oxygen m1 degree 10% Table 3: Example 3 Introduced gas: Ar102, oxygen) Opening degree 5 % Table 4: Example 4 Introduced gas: Ar102, oxygen concentration 10% Table 5: Comparative example] Introduced gas: N2102, oxygen concentration 20% Table 6: Comparative example 2 Introduced gas: N2102, oxygen concentration 70% Table 7: Comparative Example 3 Introduced gas: 02, oxygen concentration 100% Table 8: Comparative Example 4 Introduced gas: N2102, oxygen concentration 2% [Effects of the Invention] As described above, the perpendicular magnetic recording medium of the present invention I! A
Based on the manufacturing method, it was possible to produce 1q of perpendicular magnetic recording media with no cracks on the surface of the magnetic layer and excellent magnetic properties in the perpendicular direction.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an electron beam evaporation apparatus and apparatus for carrying out the manufacturing method of the present invention, and FIG. 2 is an explanatory diagram of the incident angle of the evaporated vapor flow. 3 and 4 are electron micrographs showing the grain structure on the surface of the magnetic layer not according to the present invention, and FIG. 5 is an electron micrograph showing the grain structure on the surface of the magnetic layer according to the manufacturing method of the present invention. 1: Unwinding shaft 3: Main drum 5: Winding shaft 6: Organic polymer film 7: Shielding plate 8: Electron beam evaporator 9: Evaporation vJ profit 10
: Vacuum chamber 11: Exhaust port 12: Exhaust port 13: Barrier pull leak valve 17: Opening A: Evaporated vapor flow B; Normal line on the body surface C: Base surface O: Entry angle 14 Applicant East Co., Ltd. g< 2 In No.:, p', 'yp, b'j・ε・,″i

Claims (2)

[Claims] (1) Production in which a gas with low chemical activity and oxygen gas are simultaneously introduced into a vacuum atmosphere, a ferromagnetic material is used as the evaporation material, and a magnetic layer having vertical magnetic anisotropy is formed on the substrate by vacuum evaporation. The method is characterized in that the ratio of the gas with low chemical activity to the oxygen gas is 5% by volume or more and less than 15% by volume in terms of oxygen concentration, and the main component of the ferromagnetic material constituting the evaporation material is Co. A method for manufacturing a perpendicular magnetic recording medium. (2) The pressure near the substrate when gas is introduced is 1×10^-^3
The method for manufacturing a perpendicular magnetic recording medium according to claim (1), wherein Torr to 5×10^-^2 Torr.