JPS6313117A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve runnability, durability and electromagnetic conversion characteristic by forming a thin ferromagnetic metallic film layer into multi- layered structure and specifying the oxygen concn. near the boundary face between the layer adjacent to the uppermost layer and the uppermost layer. CONSTITUTION:This recording medium 1 is formed of a substrate 2, the lower layer part 3 of the thin ferromagnetic metallic film layer, and the upper layer part 4 of the thin ferromagnetic metallic film layer. These thin films consist essentially of preferably Co or Co-Ni or Co+Ni+Cr and further, O is incorporated therein. The ratio C2/C1 between the oxygen concn. C2 near the boundary face of the lower layer part 3 with the upper layer part 4 and the oxygen concn. C1 near the surface of the upper layer part 4 is formed to 0.1-3.0. The film strength is increased according to the above-mentioned constitution; therefore, the running stability is high, and the chipping and cracking of the magnetic layer are obviated. The medium which decreases the abrasion loss of the head and has the good electromagnetic conversion characteristic is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to a magnetic recording medium, particularly a metal thin film type magnetic recording medium.

Prior art and its problems As magnetic recording media for video, audio, etc., media having a metal thin film type magnetic layer are being actively developed because of their compactness when wound into tapes.

Due to its characteristics, the magnetic layer of such a metal thin film type medium is made of a Co-based, Co-Ni-based, etc. material formed by a so-called oblique evaporation method, in which the evaporation is performed at a predetermined angle to the normal to the substrate. Membranes are preferred.

For such media, research is progressing on media using thinner films for miniaturization and long-term recording, but there are problems with running performance, durability, strength of the ferromagnetic metal thin film, etc. arise.

Therefore, in order to eliminate these inconveniences, a proposal was made to provide a metal thin film reinforcing layer on the back side of the film (Japanese Patent Laid-Open No. 56-16
No. 939, No. 58-97131, No. 57-78627
No. 57-37737) or a proposal to improve the head touch and running surface by disposing fine particles on the film surface (Japanese Unexamined Patent Publications Nos. 58-68227 and 58-10022).
No. 1 etc.) have been carried out.

In addition, in order to improve durability and electromagnetic conversion characteristics, various proposals have been made to make the ferromagnetic metal 7ij film layer have a multilayer structure of two or more layers (Japanese Unexamined Patent Application Publication No. 141608/1982, Japanese Patent Publication No. 56/1983). -26892, JP-A-57-130228, etc.).

However, at present, a technology that has good runnability, durability, and strength of the ferromagnetic thin film and does not cause any problems in terms of electromagnetic conversion characteristics has not yet been realized.

■ Purpose of the Invention The purpose of the present invention is to provide a metal thin film type magnetic material that has good running properties of the medium, less cracks and scratches in the magnetic layer due to running, less head wear and dropouts, and good electromagnetic conversion characteristics. The goal is to provide recording media.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the present invention provides C on a plastic film substrate.
It has a ferromagnetic metal thin film layer whose main component is A magnetic recording medium characterized in that the value obtained by dividing the oxygen concentration C2 at the top layer by the oxygen concentration C1 near the surface opposite to the substrate of the uppermost layer is 0.1 to 3.0.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The ferromagnetic metal thin film layer as the magnetic layer in the present invention has a multilayer structure consisting of at least two layers. The ferromagnetic metal thin film layer used in the present invention has a composition mainly composed of Co, containing 0, and further containing 11 and/or Cr as necessary.

That is, in a preferred embodiment, it may be made of Co alone, or it may be made of Co and Ni. When Ni is included, the weight ratio of Co/Ni is preferably 1.5 or more.

Furthermore, Cr may be contained in the ferromagnetic metal thin film layer.

In such cases, Cr/Co or Cr/(Co
+Ni) weight ratio is 0.1 or less, especially 0.001 to 0.
1, more preferably 0.005 to 0.05.

Furthermore, the ferromagnetic metal thin film of the present invention contains O.

The average oxygen content of the entire layer in the ferromagnetic metal thin film is an atomic ratio, particularly an atomic ratio of 0/(Co or Co+N i ), and the average oxygen content CI in the top layer is about 0.1 to 0.5, preferably It is about 0.1 to 0.4.

If the average oxygen content C is less than 0.1, corrosion resistance, running properties, cranking of the magnetic layer, scratching, etc. are insufficient;
If it exceeds this, the surface oxide layer will increase, causing problems such as a decrease in output due to head spacing.

Then, the oxygen concentration C2 near the interface between the top layer and the top layer of the adjacent layer, especially 0/(Co or Co+N1) Jji
The oxygen concentration C1 near the surface opposite to the top layer plastic film, especially O/(Co or Co+Ni
) The value C2/Cr divided by the atomic ratio is preferably 0.1 to 3.0, more preferably 0.2 to 2.0.

In this case, these oxygen concentrations are
Auger spectroscopy, SIMS (secondary ion mass spectrometry) while ion milling or ion etching
etc., and can be measured.

That is, while performing ion etching, 0, Co,
Ni, etc. are counted and their profiles in the film thickness direction are compared.

Then, O/(Co or Co+Ni) on the surface of the ferromagnetic metal thin film on the opposite side to the plastic film is assumed to be C.

Regarding C2 of the layer adjacent to the top layer, O/(Co
Alternatively, Co+Ni) may be calculated, and the second value may be set as C2. However, in each layer, under normal film forming conditions, the oxygen concentration is highest on the opposite side of the film substrate. Therefore, when 0 is counted during ion etching, the maximum value within the film is usually taken as C2.

Ion etching and Auger spectroscopy or SIM
S may be measured by a conventional method.

By relatively increasing the oxygen concentration C3 on the surface of the top layer in this way, the coercive force Hc increases, and the oxygen concentration in the area below the surface of the top layer to the vicinity of the layer adjacent to the top layer is also increased. By making it relatively lower than the above C3, the maximum residual magnetic flux φ and the squareness ratio S0 become high, resulting in a magnetic layer with extremely good electromagnetic conversion characteristics. I wanted to,
A signal with a relatively shallow magnetic field having a center frequency of about 5 MHz is effectively held in the uppermost layer.

In addition, the oxygen concentration C2 near the interface with the top layer of the layer adjacent to the top layer has a relationship with the above c1 of C2/
By making the CI relatively high in the range of 0.1 to 3.0, the coercive force Hc in this area increases,
In addition, by making the oxygen concentration of the layer adjacent to the top layer from the vicinity of the interface with the top layer to the lower part relatively lower than the above C2, the maximum residual magnetic flux φr and each diameter ratio S0 are increased, and the electromagnetic conversion characteristics This results in an extremely good magnetic layer. Therefore, a relatively deep magnetic field (No. 3) with a center frequency of about 0.7 MHz is effectively held below the layer adjacent to the top layer.

Then, as mentioned above, the relationship between C1 and 02 is C2/
When CI is 0.1 to 3.0, the magnetic layer has an excellent magnetic layer with the best balance in electromagnetic conversion characteristics, corrosion resistance, etc.

Note that O/(Co or Co+N1)C near the surface is generally 0.2 to 0.7, preferably 0.3 to 0.6.

Therefore, 0/(Co
or Co+N1)C2 is 0.07 to 0.6, preferably 0.1 to 0.5.

Furthermore, O/(Co or Co+N
1) C pi is 0.1 to 0.5, more preferably 0.1 to 0.5
Preferably it is 0.4. Also, 0/(Co or Co+N1)C2'' in the entire layer of the layer adjacent to the top layer
is preferably 0.5 or less, more preferably 0.3 or less.

At this time, electromagnetic conversion characteristics, corrosion resistance, running durability, magnetic film strength, etc. become extremely good.

In this case, in the case of a multilayer structure with three or more layers, O/(Co or Co+Ni) in each layer as a whole is generally
It is 0.5 or less, preferably 0.3 or less.

In this case, on the surface of each layer of the ferromagnetic metal thin film layer,
Oxygen forms an oxide with ferromagnetic metals (Co, Ni).

That is, 1ooλ~ from the surface of each layer 2000 people, more preferably 500 to 2000 people.

In the range of human thickness, a peak indicating oxide is observed by Auger spectroscopy.

In the present invention, the oxygen concentration on the surface of the ferromagnetic metal thin film layer and in the vicinity of the top layer of the layer adjacent to the top layer is regulated,
At that time, the effects specified by the present invention are realized.

Therefore, as described above, in the oxygen concentration profile in the thickness direction of a ferromagnetic metal thin film, there is usually a peak in oxygen distribution at least at the interface between the top layer and a layer adjacent to the top layer.

The ferromagnetic metal thin film usually has two layers, but it can also have three or more layers, especially 3 to 5 layers, if necessary.

In addition, such a ferromagnetic metal thin film may further contain other trace components, especially transition elements such as Fe, Mn, V, Zr,
Nb, Ta, Ti.

Zn, Mo, W, Cu, etc. may be included.

In a preferred embodiment, such a ferromagnetic metal thin film layer is composed of an aggregate of columnar crystal grains mainly composed of Co as described above.

In this case, the total thickness of the ferromagnetic metal thin film layer is 0.05
~0.5 μm, preferably 0.07 to 0.3 μm.

The ratio of the thickness of each layer of such a ferromagnetic metal thin film layer is not particularly limited, but for example, in the case of a two-layer structure, the ratio of the thickness of the upper layer and the lower layer is preferably about 0.1 to 10. .

The columnar crystal grains have a length spanning almost the entire thickness direction of each layer, and there is no particular restriction on the angle at which the longitudinal direction thereof is inclined with respect to the normal to the principal surface of the substrate.

In each intermediate layer in a structure of three or more layers, the inclination angle of the columnar crystal grains with respect to the normal to the main surface of the substrate is generally not limited as long as it is within the inclination angle range of the uppermost layer and the lowermost layer.

In this case, the directions of inclination of the crystal grains of each adjacent magnetic layer with respect to the normal to the main surface of the substrate may be in the same direction in the length direction of the medium, but preferably they are in opposite directions. preferable.

The direction of the inclination of the crystal grains is schematically illustrated using a two-layer structure as shown in FIGS. 1 and 2.

In FIGS. 1 and 2, a magnetic recording medium 1 has a ferromagnetic metal GI film lower layer 3 and a ferromagnetic metal thin film upper layer 4 on a base 2. As shown in FIGS. The direction of inclination of the lower layer crystal grains 5 in the lower layer part 3 of the ferromagnetic metal thin film and the direction of the inclination of the upper layer crystal grains 6 in the upper layer part 4 of the ferromagnetic metal thin film are in the longitudinal direction a of the medium in FIG. They face each other, and in FIG. 2 they are in the same direction in the length direction a of the medium.

In the present invention, the crystal grains may have either the crystal grain inclination shown in FIG. 1 or FIG. 2, but those having the crystal grain inclination shown in FIG. 1 are preferable.

As described above, since the ferromagnetic metal thin film layer has a multilayer structure consisting of at least two or more layers, the length of the columnar crystal grains becomes small, so that the film strength of the ferromagnetic metal thin film layer is improved.

Furthermore, by increasing the oxygen concentration in the top layer, oxides such as Co and Ni, which have excellent wear resistance, are formed in the top layer. The film strength becomes higher.

The material of the substrate used in the magnetic recording medium of the present invention is not particularly limited as long as it is a non-magnetic plastic, but usually polyethylene terephthalate, polyethylene 2,6
- Polyester such as naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone,
Fully aromatic polyester, polyetheretherketone,
Polyether sulfone, polyetherimide, etc. are used. In addition, there are no restrictions on its shape, dimensions, or thickness.
It may be selected according to the purpose.

A backing layer may be provided on the other side of the plastic film on which the magnetic layer is not provided.

When a lining layer is provided, the lining layer is Al1. Cu.

It is preferable to use a thin film of a single metal such as W, Mo, Cr, or Ti, an alloy containing these metals, or an oxide thereof.

Among the above-mentioned metals, it is particularly preferable to use non-magnetic ones. The reason for this is, for example, when the lining layer is made of a magnetic metal, if it is wound up with the magnetic surface magnetized, the lining layer may become magnetized by the leakage magnetic flux of the magnetic layer, or the lining layer may become magnetized. This is because when the magnetic surface is re-recorded and wound again, the magnetization state of the magnetic surface is disturbed due to the influence of the magnetism of the underlayer, which may cause problems such as increased noise.

The forming method of the backing layer includes, for example, vacuum thin film forming methods such as vapor deposition, sputtering, and ion blating, and various CVD methods.
A vapor phase growth method such as D, a plating method, or the like may be used.

The film thickness of the lining layer formed in this way is 0.05 to 1.
The thickness is preferably 5 μm, more preferably 0.07 to 0.9 μm, and even more preferably 0.07 to 0.7 μm.

If the film thickness exceeds 1.5 μm, cracks in the magnetic layer and deterioration of the magnetic properties and surface may occur due to running. Further, the amount of head wear increases. And dropouts increase. Furthermore, if the film thickness is less than 0.05 μm, running stability will decrease, head touch failure will occur, output will decrease, and envelope failure will occur.

Fine protrusions may be provided at a predetermined density on the surface of the magnetic recording medium of the present invention.

The fine protrusions are 30 to 300 people, more preferably 50 to 300 people.
It has a height of 250 people.

That is, the protrusions of the present invention cannot be observed with an optical microscope and measured with a stylus type surface roughness meter, but can be observed with a scanning electron microscope.

If the height of the protrusions exceeds 300 and becomes observable with an optical microscope, the electromagnetic conversion characteristics deteriorate and the running stability deteriorates.

Furthermore, if the number of participants is less than 50, there is no effective improvement in physical properties.

And the density is more than 105 pieces per 1 mm on average.
More preferably 105 to 109, especially 106 to 108
It is individual.

When the protrusion density is less than 10 5 /mm 2 , noise increases, still characteristics deteriorate, and other physical properties deteriorate, making it unsuitable for practical use.

Moreover, if the number exceeds 109 pieces/m2, the effect on physical properties will decrease.

Note that the diameter of the protrusion is generally about 200 to 1000λ.

In order to provide such protrusions, it is usually sufficient to arrange fine particles on the substrate. The diameter of the fine particles may be 30 to 1000, thereby forming fine protrusions corresponding to the diameter of the fine particles.

The fine particles used are usually those known as colloid particles, such as 5i02 (colloid).
L/Silica), AJ! 203 (alumina sol), M
gO, T i 02, ZnO, Fe2O3, zirconia, Cd01NiO1CaWo4. CaCo5, BaC0,, CoCo3, BaTiO3, Ti (titanium black), Au, Ag, Cu.

Ni, Fe, various hydrosils, resin particles, etc. can be used. In this case, it is particularly preferable to use inorganic substances.

Such fine particles may be prepared by forming a coating liquid using various solvents, applying this onto a substrate, and drying it, or by applying a coating liquid containing a resin component such as various aqueous emulsions and drying it. Good too.

Note that, in some cases, these coating liquids may be provided as a top coat layer on the magnetic thin film layer instead of being provided on the substrate E.

Further, when a resin component is used, it is possible to provide these fine particles with gentle protrusions that overlap the fine protrusions, but it is usually not necessary to do so.

If necessary, a non-magnetic metal thin film layer may be interposed between the top and bottom ferromagnetic metal thin film layers.

In the present invention, the magnetic layer is preferably formed by a so-called oblique evaporation method.

In this case, there is no particular restriction on the minimum incident angle of the vapor deposition substance with respect to the normal to the substrate.

Further, although two or more magnetic layers may be successively formed in one step, it is usually preferable to perform each layer in a vapor deposition step.

In this way, by dividing the magnetic layer into each layer, the direction of inclination of the magnetic columnar crystal grains with respect to the normal to the substrate can be made to face each other in the length direction of the medium between adjacent layers, as described above. direction.

With such a magnetic layer configuration, the electromagnetic conversion characteristics are extremely good.

The vapor deposition atmosphere is usually an inert atmosphere such as argon, helium, or vacuum, and an atmosphere containing oxygen gas.
The pressure may be approximately -5 to 10[deg.] Pa, and the deposition distance, substrate conveyance direction, structure and arrangement of cans and masks, etc. may be the same as known conditions.

Then, a metal oxide film is formed on the surface by vapor deposition in an oxygen atmosphere. Note that the oxygen gas partial pressure at which metal oxides are formed can be easily determined through experiments.

Note that in order to form a metal oxide film on the surface, various oxidation treatments are possible.

Applicable oxidation treatments include the following.

l) Dry process a, energetic particle process As described in Japanese Patent Application No. 76,640/1982, oxygen is applied to the magnetic layer as energetic particles using an ion gun or a neutral gun in the latter stage of vapor deposition.

b. Glow treatment 02, N20, 02+) 120, etc. and Ar.

An inert gas such as N2 is used to generate plasma by glow discharge, and the surface of the magnetic film is exposed to this plasma.

C9 oxidizing gas Items that spray oxidizing gas such as ozone or heated steam.

d. Heat treatment: Oxidation is performed by heating. Heating temperature is 60-1
About 50℃.

2) Wet treatment a, anodization, alkali treatment, C9 acid treatment, chromate treatment, permanganate treatment, phosphate treatment, etc. are used.

d. Oxidizing agent treatment ) (Use 202 etc.

The organic top coat layer of the present invention contains a radiation-curable compound, that is, one or more of radiation-curable polymers, monomers, and oligomers, an antioxidant, and, if necessary, a lubricant, and has a predetermined density. This is a layer formed on a ferromagnetic metal thin film having protrusions of the size of .

Furthermore, the running properties of the medium of the present invention can be further improved by providing a surface layer on the magnetic layer.

As the surface layer, various known materials can be applied, such as various polymeric substance coatings or coatings containing lubricants, antioxidants, surfactants, inorganic fine particles, etc.
There are various types of lubricant coatings or vapor phase deposits.

The thickness of the surface layer is approximately 5 to 300 people.

(2) Specific Effects of the Invention According to the present invention, since the magnetic layer has a layer structure of two or more layers, the length of the magnetic columnar crystal grains becomes small, so that the film strength of the magnetic layer is improved. Therefore, the running stability is extremely high, the occurrence of cracks in the magnetic layer or scratching of the magnetic layer due to running is extremely small, and the amount of wear on the head is also extremely small.

Furthermore, the ratio C2/CI between the oxygen concentration C2 on the surface of the layer adjacent to the top layer and the oxygen concentration C1 on the top layer surface is 0.1 to
3.0, the coercive force Hc becomes relatively high in the top layer, and the center frequency with a relatively shallow magnetic field becomes 5.
Signals of about M1lz can be effectively held and the resolution can be improved. In addition, in the layers adjacent to the top layer and below, the maximum residual magnetic flux φ' and the squareness ratio are high, and a signal with a center frequency of about 0.75 MHz with a relatively deep gate field can be effectively retained. be.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example 1 A polyester (PET) film having the thickness shown in Table 1 below was moved along the circumferential surface of a cylindrical cooling can.
+Ar (volume ratio 1:1) was flowed at a rate of 800 cc/min and the degree of vacuum was set to 1. c. in a chamber at 10-'Torr of Ox.

80, Ni20 (weight ratio) alloy was melted and the incident angle was determined in Table 1.
A two-layer thin film of Co-Ni-0 as shown in FIG. 1 was formed by oblique vapor deposition with the incident angle shown in FIG.

For comparison, a Co-Ni-0 single-layer thin film having a thickness of 0.15 μm was formed by obliquely depositing only the portion at an incident angle of 30° to 90°.

A large amount of oxygen was unevenly distributed at the interface between the lower layer and the upper layer and on the surface opposite to the pace. Furthermore, the surface opposite to the pace was covered almost exclusively with oxides.

Hc = 1000 0s, the average amount of oxygen in the film is Co and N
The atomic ratio (, xloo) oN 1 to i was 40%.

Table 1 shows the 0/(Co or Co+
Ni) Among the atomic ratios, C, (surface), CI (upper layer average)
, C2 (near the interface between the lower layer and the upper layer), and C2'' (lower layer average) are also written.

The following measurements were performed on each of the samples shown in Table 1 below formed in this manner. Note that the medium running direction and the direction of inclination of the lower layer with respect to the normal to the substrate were made to be the same direction.

1) Durability under conditions of temperature 20℃, humidity 60%RH, and temperature 40℃
A continuous running test was conducted under conditions of 80% RH and 80% humidity, and the number of passes until the output decreased by 2 dB was determined.

Deck used: 5ONY A-300 Head: Sputter Sendust 2) Tt, electrical conversion characteristics The output at the center frequency of 0.75 Mtlz and 5 MHz was measured, and the value when the output of sample No. 8 was expressed as OdB was determined.

Deck used: 5ONY A-300 Head: Sputter Sendust Mode: SP mode The effects of the present invention are clear from the results shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a cross section parallel to the medium direction of one embodiment of the magnetic recording medium of the present invention. FIG. 2 is a schematic diagram of a cross section parallel to the medium direction of another embodiment of the magnetic recording medium of the present invention. Explanation of symbols 1...Magnetic recording medium, 2...Substrate, 3...
Ferromagnetic metal thin film lower layer part, 4... ferromagnetic metal thin film upper layer part, 5... lower layer crystal grain, 6... upper layer crystal grain, arrow a
...Medium length direction FIG, I FIG, 2a) -TosotaneslT'tE? LP (voluntary)
6 August 27, 1988 Patent Application No. 156878 2 Name of the invention Magnetic recording medium 3 Person making the amendment Relationship to the IC matter Patent applicant Location No. 13, Nihonbashi, Chuo-ku, Tokyo F Name (306) TDC Co., Ltd. Representative Hiroshi Otoshi 4, Agent 101 Address 4th floor, Chiyoda Iwaki Building, 3-2-2 Iwamoto-cho, Chiyo III-ku, Tokyo ff1864-4498 Fax, 864- 6280
(2) Contents of amendments to the column “3. Detailed description of the invention” in the specification (1) Letter of appointment shall be amended as shown in the attached sheet. (2) “3. Detailed description of the invention” in the description The column “Explanation” will be corrected as follows: (i) Line 3 of page 14 of the specification to page 6 of page 15
The line ``The magnetic layer of such a plastic film...''
...0.07 to 0.7 μm. ”,
"It is preferable to provide a known backing layer on the other side of the plastic film on which the magnetic layer is not provided. There are no particular restrictions on the material of the backing layer, but pigments and radiation The thickness of the backing layer is preferably 0.05 to 1.5 μm, more preferably 0.05 μm to 1.5 μm.
．． 07 to 1.0μ. ” he corrected. (ii) After the ``described.'' on the 14th line of page 14 of the specification, insert a new line and add ``In addition, on the magnetic layer thin film, a surface layer of isopropyl myristate was applied by IN5!W25 person. In addition, a backing layer containing carphone, silica, and radiation-cured resin was provided on the back side of the base with a thickness of 0.5 μm.'' is added.

Claims (1)

[Claims] A ferromagnetic metal thin film layer mainly composed of Co is provided on a plastic film substrate, and this ferromagnetic metal thin film layer has a multilayer structure consisting of two or more layers, and the uppermost layer of the layer adjacent to the uppermost layer A magnetic recording medium characterized in that the value obtained by dividing the oxygen concentration C_2 near the interface with the uppermost layer by the oxygen concentration C_1 near the surface opposite to the substrate is 0.1 to 3.0.