JPS60177425A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance, etc. of the titled recording medium by forming on a nonmagnetic substrate a magnetic metallic layer wherein a magnetic metallic oxide crystal layer is formed from the surface of the magnetic thin film to the vicinity of the surface and the magnetic metallic oxide content is continuously decreased from said layer toward the substrate side with a specified content at a specified depth. CONSTITUTION:While a nonmagnetic substrate 3 of polyester, etc. is sent along a supporting drum 8 which revolves in the direction as indicated by the arrow, a magnetic metallic material 12 of Co or an Ni-Co alloy, etc. is evaporated by using an electron beam generator 10. An O2-contg. inert gas G is simultaneously spouted from a slit- shaped spout 14 of a hollow mask 13 at an angle of theta which is >=90 deg. to the line normal to the surface of the substrate 3, and the vapor deposition is carried out. By regulating the amt. of O2, a magnetic metallic oxide layer contg. a magnetic metallic oxide crystal phase is formed from the surface of the magnetic thin film to the vicinity of the surface, and the oxide cotent is gradually decreased from said layer toward the substrate. The ratio of the metallic atoms in the oxide to all metallic atoms is regulated to 50% at a position 170-400Angstrom off the surface by controlling the vapor deposition. The magnetic recording medium having excellent resistance to corrosion and abrasion and C/N can be obtained in this way.

Description

Detailed Description of the Invention (1) Background Technical Field of the Invention The present invention relates to a thin film magnetic recording medium, and more particularly to a thin film magnetic recording medium with improved wear resistance and corrosion resistance.

Prior Art and its Problems If the methods of manufacturing magnetic recording media are classified based on the method of forming the magnetic layer, they can be roughly divided into those using a coating method, those using a coating method, those using a flying method, or those using a plating method.

A magnetic recording medium obtained by a coating method (hereinafter, a magnetic recording medium obtained by this method is referred to as a coating type magnetic recording medium) is made of γ-Fe.
A magnetic coating obtained by mixing and dispersing ferromagnetic powder such as 2O3 and Fe with an appropriate binder resin is applied onto a non-magnetic substrate, and subjected to treatments such as magnetic field orientation, drying, and super calendering to form a magnetic recording medium. It has obtained the characteristics of

This coated magnetic recording medium is aimed at increasing coercive force, improving recording density, and making the magnetic layer thinner. However, with the method of coating a magnetic paint obtained by mixing ferromagnetic powder with a binder on a non-magnetic substrate, there is essentially a limit to the effective optical density of the ferromagnetic powder, and the aim is to achieve higher density and thinner films. has some difficult factors.

For these reasons, in order to achieve higher density and thinner films,
Usually, a method of forming a continuous thin film of magnetic material on a non-magnetic substrate by flying a magnetic material using methods such as vacuum evaporation, sputtering, or ion blating, and a method of forming a continuous thin film of magnetic material on a non-magnetic substrate by electrolytic or chemical methods (hereinafter referred to as , magnetic recording media obtained by these methods are referred to as thin-film magnetic recording media). This thin-film magnetic recording medium provides a magnetic recording medium that has high recording density characteristics in a short wavelength region, such as high density and thin film, which are not found in the above-mentioned coated magnetic recording media.

However, thin film magnetic recording media generally require improvements in physical, chemical, and electromagnetic properties such as corrosion resistance and abrasion resistance.

Various methods have been proposed for improving the physical and chemical properties of thin film magnetic recording media produced by the above-mentioned vacuum evaporation, sputtering, ion blating, and the like. For example, 1) the overcoat layer of wear-resistant metal is
No. 23704, No. 51-47401, No. 53-720
No. 5, No. 53-39708, No. 53-73108,
No. 54-141107, etc., 2) overcoat layers of metal oxides, nitrides, and carbides are disclosed in JP-A-52-480.
No. 5, No. 52-127204, No. 57-138054
3) An overcoat layer of an inorganic lubricant is disclosed in JP-A-50-146302, JP-A-53-57002, etc., and 4) An organic polymer film is formed in JP-A-52.
-153707, 56-153534, 57-
No. 8927, No. 58-130436, No. 58-150
No. 128, etc., respectively.

In addition, 5) products coated with or adsorbed with organic lubricants such as higher fatty acids and higher alcohol esters are available in Japanese Patent Application Laid-open No. 55
-93533, No. 58-19736, and 6) oxidation or nitridation of the surface of the magnetic layer to form an oxide film or a nitride film.
No. 3806, No. 52-153407, No. 54-143
No. 11, No. 56-15011, No. 58-26321, and the like.

However, in these conventional technologies, 1), 2), 3)
and 4), good effects on both corrosion resistance and abrasion resistance cannot be obtained unless the coating thickness is approximately 0.021 μm or more, and at that thickness, spacing loss occurs and the coating is insufficient for use as a high-density recording medium. performance cannot be obtained. However, since an additional film is formed, the adhesion between the magnetic layer and the coating is insufficient, and delamination is likely to occur, particularly in terms of wear resistance. Furthermore, in 5), the lubricant coating was easily peeled off and was easily worn out, so the properties such as methyl durability were not sufficient. In addition, 6) is a method in which oxidation and oxidation are carried out while applying heat or kinetic energy of particles, which increases the temperature during the manufacturing process and is not suitable for video magnetic recording media that use plastic substrates such as polyester. However, in a method using a solution reaction in a wet system, a film with poor practical characteristics is formed, but the film thickness becomes large and spacing loss occurs, and if the film thickness is made thinner, sufficient wear resistance cannot be obtained. Not only was it not effective, but it also caused secondary problems such as promoting corrosion.

■ Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and the first object of the present invention is to provide a magnetic recording medium with excellent physical and chemical properties such as corrosion resistance and abrasion resistance. It is to provide a medium.

A second object of the present invention is to provide a magnetic recording medium with a high output level, low noise level, and excellent Q-to-ratio.

■Specific structure of the invention The above object of the present invention is to provide a magnetic recording medium having a magnetic thin film on a non-magnetic substrate, in which an oxide crystal layer containing an oxide crystal phase of a magnetic metal is formed from the surface of the magnetic thin film in the vicinity thereof. The metal and the oxide of the metal are formed continuously in the thickness direction of the layer, and in the layer containing the metal and the metal oxide in a mixture, each A magnetic film in which the ratio α of oxide-forming metal atoms to all metal atoms forming metals and metal oxides decreases continuously from the surface of the magnetic thin film in the film thickness direction, and the α is 0.5. The depth position in the film thickness direction from the surface of the thin film is 170A to 4
In the magnetic recording medium of the present invention, which is achieved by a magnetic recording medium characterized in that the magnetic metal is In the case of a Co-Ni alloy, oxides satisfying the stoichiometry of Co01Co304, Ni01Ni304, etc. (which may also include oxides of other trace atoms) are mixed to form an oxide crystal phase. Similarly, when the magnetic metal is another alloy or a single metal, molecules that exist as a metal oxide that satisfies the stoichiometry exist at a density that forms a crystalline phase.This oxide crystalline phase As described later, ESCA (Ele
ctronSpectroscopyFor Chem
It is determined to be an oxide crystal phase by comparison with standard sample data using means such as ical analysis), X-ray diffraction, and electron beam diffraction.

This oxide crystal layer contains a physically and chemically stable oxide crystal phase, and since it exists near the surface, it has excellent wear resistance and corrosion resistance, and functions as an effective protective layer. Improve the abrasion resistance and corrosion resistance of recording media.

The layer containing a mixture of a magnetic metal and an oxide of the metal formed continuously in the film thickness direction of the oxide crystal layer has a stoichiometry similar to the metal oxide contained in the oxide crystal layer. A metal oxide that satisfies the above is mixed with a magnetic metal, and the ratio α of metal atoms forming the oxide to all metal atoms forming the metal and metal oxide at each film thickness depth is continuous from the surface of the magnetic thin film in the film thickness direction. This decreases significantly. In this mixed layer, the film thickness of the magnetic thin film in which the value of α is 0.5 is practically preferable, and 180A to 220A is more preferable.

Furthermore, the mixed layer in the present invention refers to an interdiffusion region formed at the boundary between a normal magnetic thin film and a metal oxide layer formed thereon by a separate method such as heat treatment or coating. Rather, the mixed composition of metal and metal oxide that satisfies the stoichiometry is arbitrarily controlled, and the thickness of the mixed layer is large (up to several hundred), and the composition changes continuously and slowly (for example, (about 30 cents per 100 people).

Since this mixed layer is continuous with the metal oxide crystal layer that functions as a protective layer, there is no problem of peeling of the surface metal oxide crystal layer at the interface, and wear resistance is improved.

Furthermore, the mixed composition near the interface with the metal oxide crystal layer of this mixed layer contains a large amount of metal oxide that satisfies the stoichiometry and strengthens the retention function. As time approaches, the proportion of metal oxides decreases, and the proportion occupied by magnetic metal increases, contributing to an increase in the output level of the magnetic recording medium. Furthermore, on the substrate side of the mixed layer, the growth of trace amounts of metal oxide layer particles in the magnetic metal is suppressed, contributing to the miniaturization of particles, and as a result, the C/H of the magnetic recording medium is dramatically improved. Realized.

The magnetic recording medium of the present invention specifies a mixed composition of a magnetic metal and a fully bent oxide in a depth of about 400 A in the film thickness direction from the surface of the magnetic thin film in this mixed layer. That is, it does not specify the structure of the magnetic layer in the film thickness direction, and does not exclude known structures such as stacked magnetic layers, stacked nonmagnetic layers, etc.

In the magnetic recording medium of the present invention, methods for forming a magnetic thin film on a nonmagnetic substrate include known vacuum evaporation (including reactive evaporation), sputtering, ion blating, C
VD (Chemical Vapor Deposit
ion) and the like. Here, electron beam reactive vapor deposition is preferred.

Examples of magnetic metal materials that can be used in the magnetic recording medium of the present invention include Fe, Co, Ni, and other magnetic metals.
e-Co, Fe-Ni5Co-Ni5Fe-3
i, FeRh, Fe-V-, ke-Cu5
Fe-Au 1Co-P% Co-V% Co-8
1, Co-Y, Co-La, Co-Ce, C
o-Pr, Co-5m.

Co-Mn% Co-Pt% Ni-Cu,,C
o-Ni-FeSCo-Ni-Ag.

Co-Ni-Zn, Co-8t-AI, Fe-8
t-AI,, Mn-B1, Mn-8b s Mn
-Al, etc. Here, preferably Co or Co-Ni alloy (Ni content 30
wt% or less). Note that other trace components may be included as necessary.

Examples of the nonmagnetic substrate include commonly used plastic substrates such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polycarbonate, polypropylene, cellulose triacetate, polyimide, aramid, etc., with polyethylene terephthalate being preferred.

In addition, the magnetic recording medium of the present invention may be coated on a substrate with the above-mentioned magnetic thin film after and/or before formation for the purpose of improving slipperiness, preventing static electricity, preventing transfer, improving storage stability, and improving wear resistance. Depending on the coating method, vapor deposition method, etc., an overcoat layer or a backcoat layer may be provided. These coating methods and vapor deposition methods are described, for example, in JP-A-54-123922.
No. 54-123923, No. 56-71284,
No. 56-71286, No. 56-71287, No. 56
-11626 and 57-135442.

Materials for these overcoat layers and backcoat layers include various polymers (for example, urethane resins, epoxy resins, vinyl chloride-vinyl acetate copolymers, etc.), organic oligomers and polymers such as silicone resins: carbon black,
Inorganic materials such as alumina: Various materials such as antioxidants such as phenol derivatives and low molecular weight organic compounds such as singlet oxygen quenchers such as amine derivatives can be used, as well as lubricants, abrasives, antistatic agents, and dispersants. It can be used by adding various components called.

FIG. 1 shows a sectional view of essential parts of an embodiment of an apparatus used in manufacturing the magnetic recording medium of the present invention.

The inside of this device is hermetically sealed from the outside air by a casing 1, and the inside of the casing 1 is divided by a separation wall 2 into a chamber for delivering and winding up a non-magnetic substrate 3 and a deposition chamber. An exhaust pipe 4 is provided at the bottom of the casing 1, and the exhaust pipe 4 is connected to a vacuum exhaust device 5. In the delivery/winding chamber, a delivery shaft 6.2 is provided as a substrate traveling system.
It has a free row 27, a substrate support 8, and a winding shaft 9. The vapor deposition chamber includes an electron beam generator 10 as a vapor deposition system.
, a melt 11, a magnetic material 1 to be coated placed in the crucible 11
2 is further provided with a mask 13 that protrudes into the flight space formed between the substrate support 8 and the substrate 11 to regulate the angle at which the flying vapor flow of the magnetic material 12 is incident on the substrate 3. It's starting to look like this. The mask 13 has a hollow structure, and is provided with a slit-shaped ejection port 14 having a long side in the width direction of the substrate 30 set on the substrate support 8 near the incident angle regulating tip. The gas G is introduced through the gas introduction pipe 15 and is ejected from the slit-shaped ejection port 14 toward the substrate 3 at a predetermined angle. As shown in FIG. 2, the direction in which the reactive gas is ejected is preferably such that the angle θ between the normal to the substrate surface at the position where the ejected gas collides with the substrate 3 and the gas ejection direction is 90 or more, and more preferably. Preferably it is 140-180. Furthermore, the distance between the jet nozzle 14 and the substrate surface is preferably 15 m or less,
y) preferably 3 to 10 III.

Appropriate values for the velocity and amount of the ejected gas and the width of the slit of the ejection port 14 are determined by correlation, but the width of the slit is preferably 5- or less, more preferably 0.5 to 24, and The speed and amount are 2 x 10 to 0 per 10 m slit width.
．． 5 Pa□S, more preferably 0.1 to 0.3 PacM'B per slit width 106n. At this time, in order to increase the uniformity of the speed and amount of ejected gas,
A tank may also be provided between the introduction pipe 15 and the introduction port.

In addition, although cooling mechanisms for the substrate support, mask, etc. are omitted, techniques known in the art can be used selectively as desired.

Furthermore, although an electron beam heating method is used in the embodiment, methods such as resistance heating, laser beam heating, etc. may also be used.

The reactive gas used in the present invention may be any gas containing at least one selected from oxygen, allotropes of oxygen, and active species of oxygen. Other gases that can be used in combination with the gas include nitrogen (N2), for example. gas, helium gas (He
)', xenon gas (Xe), radon gas (Rn),
Inert gases such as argon (Ar) and neon (Ne), carbon oxide (CO), carbon dioxide (CO, ), hydrogen (N
2) Water vapor (N20) can be used alone or in combination of two or more types.

Generally, methods such as Osier vector analysis, ESCA, and X-ray diffraction are used to analyze the composition of magnetic thin films.
In Auger spectroscopy, although the composition of atoms forming a thin film can be analyzed, the bonding state of the atoms is unknown. For example, whether oxygen atoms exist as metal oxide molecules or free oxygen molecules. The current state of the technology is that it is not possible to distinguish whether the material is incorporated into a thin film or not. In the magnetic recording medium of the present invention, the composition of the magnetic metal and the oxide of the metal (satisfying stoichiometry) is determined at the depth in the film thickness direction of each sample by ESCA. The outline will be explained below.

ESCA provides information about the oxidation state of metals, etc. For example, with regard to Co, by measuring the signal derived from 2p photoelectrons, it is possible to find out whether Co is in a metallic state or an oxidized state. In the sixth step of analyzing the film thickness direction of the sample, etching is performed using an argon ion gun or the like, and measurement is performed using ESCA at each film thickness direction. Etching conditions include, for example, 5kV, 2
5 mA s 8 mu raster with known thickness Co
-Ni alloy, the etching rate is about 12 people/min. Taking as an example the case where metal Copal 1 is used as the magnetic metal, the composition ratio of metal and metal oxide in the magnetic thin film of the obtained magnetic recording medium sample is determined as follows.

First, calculate the ESCA spectrum of the standard sample. Specifically, after thoroughly etching a cobalt pure metal standard sample to clean the surface, a standard spectrum of metal cobalt (shown in FIG. 3) is obtained by ESCA measurement. Next, for cobalt oxide (Coo), the standard spectrum (
(shown in FIG. 4) is obtained. (The spectrum shown in Figure 3.4 is the spectrum of Co2p after baseline correction.) According to the comparison in Figure 3.4, the shift in the peak position (
Differences in chemical shift) and peak shapes are clearly recognized. It is assumed that the sensitivities c (counts of photoelectron signals per unit number of atoms) of metallic cobalt and cobalt oxide are approximately equal, and that the spectrum of the mixture of metallic cobalt and cobalt oxide is similar to that of metallic cobalt and cobalt oxide. ) It is considered to be equal to the product of each standard spectrum of M compound multiplied by each mixing ratio and then added. At this time, each standard spectrum of metallic cobalt and cobalt oxide can be multiplied by an appropriate constant corresponding to each mixing ratio and then added to form the standard spectrum at each mixing ratio. The mixing ratio of metallic cobalt and cobalt oxide can be estimated by comparing the spectrum with that of . Although only Coo is shown as the standard spectrum of cobalt oxide,
In the following examples as well, considering that Co2O3, which is another component as cobalt oxide, can be almost ignored based on the analysis results of X-ray diffraction and ESCA spectrum, the cobalt oxide was considered as a single compound of CoO.

In addition, when using Co-Ni alloy as a magnetic metal,
In the same way as for the simple substance of Co metal mentioned above, a standard spectrum was created for Ni metal, and c.

By comprehensively evaluating Ni and Ni, the mixing ratio of metal and metal oxide can be estimated. Similar methods can be applied to other metals,
It can also be applied to alloys and the like.

(2) Specific Examples of the Invention The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Using the apparatus shown in FIG. 1, a slit-shaped oxygen gas outlet was provided near the tip of a mask for controlling the air inlet angle, and a magnetic recording medium was manufactured under the following conditions.

Oxygen gas injection amount 2.5 ky/crl, 1.5 t
/=Gas ejection angle θ=170 Distance between the ejection port and the substrate 7.0 At a regulating pressure of xlOPa, a 12.5 μm thick polyethylene terephthalate substrate “FC50m7-” was applied to Co-Ni (80: The magnetic material No. 20) was evaporated by electron beam heating, and oxygen gas was ejected from the ejection port to form a magnetic thin film with a thickness of 1500 A.

After forming the magnetic thin film, the original magnetic recording medium was cut into tapes with a width of 12.65 m to obtain Example Tape 1.

The ratio α of oxide-forming metal atoms to all metal atoms forming metal and metal oxide in each thickness direction of Example Tape 1 was determined by ESCA measurement. The equipment used for E8CA measurement was Perkin-E1mer, PHI
Model 560 type ESCA/SAM) using an At anode under the conditions of 15 kV and 300 W.

For energy resolution, a path energy of 25 eV was used. In addition, etching is performed using an argon ion gun.
The etching rate was about 12 A/min fc for the Co--Ni alloy, and the results of the ESCA measurements are shown in FIG. It can be seen that the amount of oxide decreases as you move away from the surface (all oxide). Also, after forming the magnetic thin film? 11
X#i of magnetic tape before applying lubricant! The diffraction spectrum pattern is shown in FIG.

Furthermore, under the above conditions, the amount of oxygen gas ejected was increased to 2,5
Example tapes 2 to 4 were obtained in the same manner except that kv/6i was changed from 1.2/- to 2.0-.

ESCA measurements were performed on Example Tapes 2 to 4 in the same manner as Example Tape 1, and the film thickness depth of α=0.5 was determined. The methyl durability of each of the obtained tape samples 1 to 4 was measured using a commercially available VTR deck. Still durability was determined by measuring the time required for the output to drop by 3 dB at a pack tension of 12 Pt in minutes. The obtained result is expressed as α is 0.
．． FIG. 7 shows the values determined for each tape sample using the depth position in the film thickness direction from the magnetic surface as an index as the horizontal axis, and the corresponding methyl durability as the vertical axis. In addition, the C/N characteristics at 5MHz of the tape samples 1 to 4 were measured,
The results are shown in the figure. As shown in Figure 7, from the practical range of still durability, it is preferable that the film thickness direction depth & [ at α = 0.5 is 170A or more, and the C/N ratio In addition, 22
It is preferable that it is 0X or less.

■Specific effects of the invention As explained above, the magnetic recording medium of the invention has wear resistance,
It showed good results in terms of corrosion resistance and also gave good results in terms of public properties.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a cross-sectional view of the main part of an apparatus used for manufacturing the magnetic recording medium of the invention, FIG. 2 is an enlarged view of the main part of the apparatus shown in FIG. 1, and FIG. Figure 3 is an ESCA spectrum of a standard metal cobalt sample, Figure 4 is an ESCA spectrum of a standard cobalt oxide Co., Ltd. sample, and Figure 5 is a composition analysis diagram at each thickness direction depth of the magnetic thin film obtained in Example 1. , FIG. 6 is the X-ray diffraction spectrum pattern of the magnetic thin film obtained in Example 1, and FIG. 7 is the α= obtained in Example 1.
FIG. 3 is a diagram showing still durability and C/N characteristics of tape samples having different depth positions in the film thickness direction of 0.5. Patent Applicant: Roku Konishi Photo Industry Co., Ltd. Figure 1: Figure 1.
＞Figure 6 2θζ Hire 2 Figure 7

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic thin film on a non-magnetic substrate, an oxide crystal layer containing an oxide crystal phase of a magnetic metal is formed from the surface of the magnetic thin film to its vicinity, and in the thickness direction of the layer. A layer containing a mixture of the metal and an oxide of the metal is successively formed, and in the layer containing a mixture of the metal and the metal oxide, the metal and the metal oxide are mixed at each film thickness. The ratio α of oxide-forming metal atoms to all metal atoms forming the magnetic thin film decreases continuously from the surface of the magnetic thin film in the film thickness direction, and the depth in the film thickness direction from the surface of the magnetic thin film where α is 0.5. A magnetic recording medium characterized in that the position is 170A to 400A. (2) The magnetic metal is Co or Co-N1 alloy (N
A magnetic recording medium according to claim (1), characterized in that the i content is 30 wt% or less.