JPH09176525A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent magnetic recording medium effective for minimizing the generation of rust on the surface of a magnetic layer caused by a back-coating layer, enabling stable transportation and preservation characteristic of the back-coating layer and suitable for high-density magnetic recording. SOLUTION: The objective magnetic recording medium having a magnetic metal thin film is provided with a ferromagnetic metal thin film formed as a magnetic layer on one surface of a non-magnetic substrate and a back-coating layer consisting of a non-magnetic pigment dispersed in a binder and formed on the other surface of the substrate. A silicone oil is added to the coating material of the back-coating layer containing 1-20ppm of chlorine ion and sulfate ion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, particularly a metal thin film type magnetic recording medium.

[0002]

2. Description of the Related Art Iron, cobalt, nickel or an alloy containing them as a main component, or an oxide thin film is formed on one main surface of a non-magnetic support by a vacuum film forming method such as vacuum deposition, sputtering or ion plating. A ferromagnetic metal thin film type magnetic recording medium (hereinafter referred to as a vapor deposition tape) formed on a non-magnetic support has characteristics such as recording density which are higher than those of a conventional coating type magnetic recording medium. It has already been put to practical use as a magnetic recording medium for short-wavelength magnetic recording signals (high-density magnetic recording) such as 8 mm video tapes and digital VTRs.

In the above-described vapor-deposited tape, in order to improve the recording density, it is necessary to reduce the gap of the magnetic recording head and also to smooth the surface of the magnetic recording medium to reduce the spacing loss as much as possible. is there.

However, if the surface of the magnetic layer is excessively smoothed, the surface becomes close to a mirror-like state, and the substantial coefficient of friction increases, which hinders head touch and running performance. For this reason, a back coat layer having an appropriate roughness on its surface is formed on the side of the non-magnetic support on which the magnetic layer is not provided.

This back coat layer is indispensable for the purpose of suppressing the electrification of the magnetic recording medium, eliminating the influence of dust, etc., and stabilizing the running, and usually carbon etc. having an appropriate particle size. It is formed by dispersing and mixing the non-magnetic pigment of (1) with a binder, an organic solvent and the like, and applying this to one main surface of the non-magnetic support.

[0006]

The formation of the above-mentioned back coat layer has a great advantage in that the running property of the tape is improved. However, depending on the paint used for the back coat layer, rust may be induced in the magnetic layer, that is, the ferromagnetic metal thin film. It is presumed that this is because the back coat layer has some adverse effect on the surface of the magnetic layer.

Regarding this, when a large amount of chlorine ions and sulfate ions contained in the back coat layer are present,
For example, it is known that when the magnetic layer surface and the back coat layer surface are in contact with each other and stored in a high temperature and high humidity environment, rust occurs on the magnetic layer surface, the dropout characteristics deteriorate, and the durability also deteriorates. This will be described.

First, a sampling sample was used by the following extraction method to collect chlorine ions in the back coat layer,
The relationship between sulfate ions and rust generated on the surface of the magnetic layer was examined.

In the inspection in this case, as a sample, 5 g of a powder obtained by evaporating the coating material for the back coat layer to dryness at 60 ° C. and crushing the solvent-removed solid is prepared and mixed with 100 ml of pure water.

Then, the mixture is heated and extracted at 100 ° C. for 3 hours, and then 50 ml is filled up to obtain a sample liquid for extraction measurement, and the chlorine ion and the sulfate ion amount are measured by ion chromatography. Here, the heat extraction time is set to 3 hours, but the time is not limited as long as it is performed when extraction and saturation are performed.

Chloride ions contained in the back coat layer,
Since the amounts of sulphate and sulfate ion are influenced by the method of synthesizing the coating material for the back coat layer, materials, etc., the content thereof can be adjusted by selecting from commercially available materials.

The amount of chlorine ions and sulfate ions contained in the back coat layer, which was inspected by the above-mentioned method, was 3 p.
It was found that when it is pm or more, for example, when the magnetic layer surface and the surface of the back coat layer are in contact with each other and stored in a high temperature and high humidity environment, rust occurs, dropout characteristics deteriorate, and durability also deteriorates.

That is, in the conventional vapor-deposited tape having the back coat layer formed, there are some tape tapes which show a significant deterioration in the tape characteristics after long-term storage under high temperature and high humidity, and improvement thereof is demanded. Particularly in a home digital VTR or the like for recording digital image signals, it is necessary to improve the quality of the magnetic layer surface more than ever because of the necessity of high density magnetic recording.

Therefore, in view of the above conventional circumstances, the present invention suppresses the induction of rust on the surface of the magnetic layer due to the influence of the back coat layer as much as possible, and provides the stable running property and the storage property which are the original effects of the back coat layer. (EN) Provided is an excellent magnetic recording medium which can be secured and which is optimum for high density magnetic recording.

[0015]

According to the present invention, in a metal magnetic thin film type magnetic recording medium, a ferromagnetic metal thin film is provided as a magnetic layer on one main surface of a non-magnetic support, and another main surface is provided. A back coat layer formed by dispersing a non-magnetic pigment in a binder is provided on the top of the back coat layer.
A magnetic recording medium is characterized in that silicone oil is added to a back coat layer coating material containing 0 ppm.

As described above, in the present invention, the outermost surface of the back coat layer is covered with silicone oil by adding silicone oil to the coating material of the back coat layer containing 1 to 20 ppm of chlorine ion and sulfate ion. In such a form, the effect of reducing the area in contact with the surface of the magnetic layer was exhibited, and deterioration of the quality of the magnetic recording medium could be suppressed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic recording medium according to the present invention will be described below. First, a paint for a back coat layer was prepared and applied to a non-magnetic support, for example, a polyethylene terephthalate film to a thickness of, for example, 0.5 μm to form a back coat layer. The coating material for the back coat layer has a solid content of 15%, a pigment such as 100 parts by weight of carbon, a PB ratio (mixing ratio of non-magnetic pigment and binder) of 1.2, and a curing agent such as Coronate L.
-50 (product name of Nippon Polyurethane Company) 10 PHR
(Binders such as polycarbonate and polyurethane 1
10 parts by weight based on 00 parts by weight). Silicone oil is further added to this.

On the other hand, a ferromagnetic metal having a composition of, for example, Co80% -Ni20% is provided on the surface opposite to the back coat layer in an oxygen atmosphere, for example, an oxygen introduction amount of 3.3 × 10.
^-6 (m ³ / sec) was obliquely vapor-deposited at an incident angle of 45 to 90 ° to form a ferromagnetic metal thin film having a film thickness of 200 nm. Also, for example, perfluoropolyether is applied as a lubricant to the surface of this ferromagnetic metal thin film.

The structure of an example of the vapor deposition manufacturing apparatus used in this embodiment will be described below. As shown in FIG.
In this manufacturing apparatus, the unwinding roll 3 that rotates counterclockwise in the vacuum chamber 1 that has been evacuated from the exhaust ports 15 and 25 provided in the head and the bottom and has a vacuum inside, A winding roll 4 that rotates in a clockwise direction is provided, and from these unwinding rolls 3,
The tape-shaped non-magnetic support 2 is sequentially run on the winding roll 4.

A cooling can 5 is provided while the non-magnetic support 2 travels from the unwinding roll 3 to the winding roll 4. The cooling can 5 is configured to rotate clockwise. In addition, a cooling device (not shown) is provided in the cooling can 5 to suppress deformation and the like of the nonmagnetic support 2 due to temperature rise.

The non-magnetic support 2 is sequentially fed from the unwinding roll 3, passes through the peripheral surface of the cooling can 5, and is wound around the winding roll 4 at a constant linear velocity.

Guide rolls 6 and 7 are arranged between the unwinding roll 3 and the cooling can 5 and between the cooling can 5 and the winding roll 4, respectively. A predetermined tension of the non-magnetic support 2 traveling from the cooling can 5 to the winding roll 4 is applied so that the non-magnetic support 2 smoothly travels.

A crucible 8 is provided below the cooling can 5 in the vacuum chamber 1, and a metal magnetic material 9 is provided in the crucible 8.
Is filled.

On the other hand, an electron gun 10 for heating and evaporating the metallic magnetic material 9 filled in the crucible 8 is attached to the side wall of the vacuum chamber 1. The electron gun 10 is the electron gun 1
The electron beam B emitted from 0 is arranged at a position where the metal magnetic material 9 in the crucible 8 is irradiated. Then, the metal magnetic material 9 evaporated by being irradiated with the electron beam B
Is a non-magnetic support 2 running on the peripheral surface of the cooling can 5 at a constant speed.
Deposit on top to form a magnetic layer.

A shutter 13 is arranged between the cooling can 5 and the crucible 8 and near the cooling can 5. This is formed so as to cover a predetermined area of the non-magnetic support 2 running at a constant speed on the peripheral surface of the cooling can 5, and the evaporated metal magnetic material 9 is placed on the non-magnetic support 2 by a predetermined amount. It plays the role of oblique vapor deposition in the angle range.

Further, during such vapor deposition, oxygen gas is supplied to the surface of the non-magnetic support 2 through the oxygen gas introduction pipe 14 penetrating the side wall of the vacuum chamber 1 to provide magnetic characteristics and durability. , The weather resistance is improved.

Next, Examples 1 to 4 and Comparative Examples 1 and 2
Will be explained. The main manufacturing conditions of the sample tapes used in these examples and comparative examples are shown.

Non-magnetic support Polyethylene terephthalate (thickness 6 μm, width 150 mm) Deposition conditions Metal magnetic material Co 100 wt% Incident angle 45 ° to 90 ° Oxygen introduction amount 3.3 × 10 ⁻⁶ m ³ / sec Deposition vacuum degree 7 × 10 ^-2 Pa Back coat layer Thickness 0.5 μm Pigment Carbon 100 parts by weight Binder Polycarbonate and polyurethane 100 parts by weight Curing agent Coronate L-50 10 parts by weight Top coat Applying perfluoropolyether on magnetic surface Slit width 8 mm

Further, the respective amounts of chlorine ion and sulfate ion contained in the back coat layer are inspected by the same method as described above, that is, the ion chromatography (anion) inspection method.

By the above-mentioned method, various sample tapes shown below were prepared using paints for backcoat layers having different chlorine ion and sulfate ion contents, and 0.5PHR was applied to the paints for backcoat layers. The still characteristics and the decrease rate of magnetic flux (Δφr), which is an index of rust generation, were measured in the high temperature and high humidity environment (after storage at 60 ° C. and 95% for 10 days) with and without addition of silicone oil.
Dropout increase rate after storing at high humidity (4 at 80% at 45 ° C)
After storage for one day) was measured.

The dropout is measured by Sony E
A VS-900 modified machine was used. The recording signal was performed using 50% white. The still characteristics of each of these Examples 1 to 4 and Comparative Examples 1 and 2, the reduction rate of magnetic flux (Δφr),
Table 1 shows each measurement result of the dropout increase rate.

[0032]

[Table 1]

As is clear from Table 1, in Examples 1 to 4, the coating materials for the back coat layer were measured to contain chlorine ions and sulfate ions in an amount of 1 to 20 ppm, respectively. According to this, it can be seen that in the case of the present invention in which 0.5 PHR of silicone oil is added to the coating material for the back coat layer, a remarkable effect can be seen as compared with the case where it is not added.

Further, in Comparative Example 1, chlorine ions and sulfate ions were added to the back coat layer coating material in amounts of 2 and 2, respectively.
In the case where the content is 0 ppm or more, also in this case, when 0.5 PHR of silicone oil is added to the coating material for the back coat layer, the effect is seen as compared with the case where it is not added, but the dropout increase rate decreases. Can't get enough.

Comparative Example 2 is a case where chlorine ion and sulfate ion are as small as 1 ppm or less respectively in the coating material for the back coat layer, and in this case, 0.5 PHR of silicone oil is added to the coating material for the back coat layer. Has
Compared to the case where no addition is made, the still characteristics are more effective, but the decrease rate of the magnetic flux (Δφr) and the increase rate of the dropout are not so effective as the addition of silicone oil.

From the above, when the coating material for the back coat layer contains 1 to 20 ppm of chlorine ions and sulfate ions, the addition of silicone oil has a great influence on the occurrence of rust and durability. You can see that

In the above-mentioned constitution of the present invention, as the non-magnetic pigment dispersed in the coating material for the back coat layer, in addition to the carbon used in the above-mentioned examples, if necessary,
Hematite, mica, silica gel, magnesium oxide, zinc sulfide, tungsten carbide, boron nitride, starch, zinc oxide, kaolin, talc, clay, lead sulfate, barium carbonate, calcium carbonate, magnesium carbonate, boehmite (γ
_{-Al 2 O 3 · H 2 O} ), alumina, tungsten sulfide, titanium oxide, polytetrafluoroethylene powder, polyethylene powder, polyvinyl chloride powder may be used in combination with metal powders and the like.

The backcoat layer is prepared by kneading the above-mentioned non-magnetic pigment with a binder and an organic solvent to prepare a coating material for the back-coat layer, which is applied to the main surface of the non-magnetic support opposite to the magnetic layer. It is formed by
Any known binder and organic solvent can be used at this time.

As the binder, for example, in addition to the polycarbonate and polyurethane used in the above-mentioned examples,
As those conventionally used, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate-maleic acid copolymers, vinyl chloride-vinylidene chloride Copolymer,
Copolymer of vinyl chloride and acrylonitrile, copolymer of acrylate and acrylonitrile, copolymer of acrylate and vinylidene chloride, copolymer of methacrylate and styrene, thermoplastic polyurethane resin, phenoxy resin, polyfluorinated Vinyl, copolymer of vinylidene chloride and acrylonitrile, copolymer of butadiene and acrylonitrile, copolymer of butadiene and acrylonitrile and methacrylic acid, polyvinyl butyral, cellulose derivative, copolymer of styrene and butadiene, polyester resin, phenolic resin, Epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea and formaldehyde resins, or mixtures thereof, and the like can be given. These may use an isocyanate compound as a cross-linking agent to further improve durability or may have a suitable polar group introduced.

Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl acetate acetate, glycol dimethyl ether and glycol. Glycol ether solvents such as monoethyl ether and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, organic chlorine compound solvents such as methylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene. can give.

The magnetic layer is made of Co, Co-Ni, Co.
A ferromagnetic metal thin film such as -Fe-Ni is deposited by a vacuum thin film forming technique such as vapor deposition (oblique vapor deposition, vapor deposition in an atmosphere containing oxygen, and further a combination thereof), and a normal thin film. Any material may be used as long as it is used for a vapor deposition tape. For example, F
e, Co, Ni and other ferromagnetic metals, Fe-Co, Co-F
e-Ni, Fe-Cu, Co-Cu, Co-Au, Co
-Pt, Mn-Bi, Mn-Al, Fe-Cr, Co-
Cr, Ni-Cr, Fe-Co-Cr, Co-Ni-C
Examples include ferromagnetic alloys such as r and Fe-Co-Cr-Ni. These may be a single-layer film or a multilayer film.

Further, in the case of a non-magnetic support and a metal magnetic thin film or a multi-layer film, an underlayer or an intermediate layer may be provided in order to improve the adhesive force between the layers and control the coercive force. Further, for example, the vicinity of the surface of the magnetic layer may be made of an oxide for improving corrosion resistance and the like.

As a means for forming the metal magnetic thin film, a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under a vacuum and deposited on a non-magnetic support, or ion plating in which a ferromagnetic metal material is evaporated in a discharge is used. A so-called PVD technique such as a sputtering method or a sputtering method in which a glow discharge is generated in an atmosphere containing argon as a main component and atoms on the target surface are knocked out by the generated argon ions.

A protective film layer may be formed on the ferromagnetic metal material formed on the non-magnetic support, but this material is generally used as a protective film for ordinary metal magnetic thin films. Any material may be used as long as it allows it. For example, carbon, CrO ₂ , Al ₂ O ₃ , B
N, Co oxide, MgO, SiO ₂ , Si ₃ O ₄ , Si
_{N x -SiO 2, ZnO 2,} TiO 2 TiC and the like. These may be a single-layer film, a multilayer film, or a composite film.

As the non-magnetic support, any conventionally known one can be used. For example, polyesters such as polyethylene terephthalate, polyethylene, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate, cellulose derivatives such as cellulose acetate butyrate, polyvinyl chloride, vinyl resins such as polyvinylidene chloride, polycarbonate, polyimide, Plastics such as polyamide and polyamide-imide, paper, metals such as aluminum and copper,
Examples include light alloys such as aluminum alloys and titanium alloys, and ceramic single crystal silicon.

The form of the non-magnetic support is as follows.
It may be a film, tape, sheet, disk, card, drum, or the like.

[0047]

INDUSTRIAL APPLICABILITY In the present invention, chlorine ion and sulfate ion are added to the back coat layer coating material in an amount of 1 to 20 respectively
By adding silicone oil to the back coat layer paint when it contains ppm, the release effect can be exhibited, the dropout increase rate can be kept low, and stable running properties can be achieved without degrading the characteristics of the vapor deposition tape. As a result, the storage characteristics can be secured, and an excellent high density magnetic recording medium can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a continuous evaporation winding device.

[Explanation of symbols]

 1 vacuum chamber 2 non-magnetic support 3 unwinding roll 4 winding roll 5 cooling can 6 guide roll 7 guide roll 8 crucible 9 metal magnetic material 10 electron gun 13 shutter 15 exhaust port 25 exhaust port

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[Procedure amendment]

[Submission date] January 31, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

The formation of the above-mentioned back coat layer has a great advantage in that the running property of the tape is improved. However, magnetic magnetic layer or the ferromagnetic metal thin film by coating material used in the backcoat layer
It may cause deterioration of air quality . It is presumed that this is because the back coat layer has some adverse effect on the surface of the magnetic layer.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

Regarding this, when a large amount of chlorine ions and sulfate ions contained in the back coat layer are present,
For example, if the magnetic layer surface and the back coat layer surface are in contact with each other and stored in a high temperature and high humidity environment, the magnetic properties of the magnetic layer will be poor.
As a result, it is known that the dropout characteristics deteriorate and the durability also deteriorates. This will be described.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

First, a sampling sample was used by the following extraction method to collect chlorine ions in the back coat layer,
The relationship between the sulfate ion and the deterioration of the magnetic properties of the magnetic layer was examined.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

Any of the amounts of chlorine ions and sulfate ions contained in the back coat layer examined by the above-mentioned method
If it is 1 ppm or more, for example, when the magnetic layer surface and the surface of the back coat layer are in contact with each other and stored in a high temperature and high humidity environment, the magnetic characteristics deteriorate , the dropout characteristics deteriorate, and the durability also deteriorates. I understood.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

Therefore, in view of the above conventional circumstances, the present invention has an inferior magnetic property of the magnetic layer due to the influence of the back coat layer.
The present invention provides an excellent magnetic recording medium that is most suitable for high-density magnetic recording and that can suppress the formation of the back coat layer as much as possible and can secure the stable running property that is the original effect of the back coat layer and the storage property.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

By the above-mentioned method, various sample tapes shown below were prepared using paints for backcoat layers having different chlorine ion and sulfate ion contents, and 0.5PHR was applied to the paints for backcoat layers. The decrease rate of magnetic flux (Δφ, which is an index of deterioration of still characteristics and magnetic characteristics , with and without addition of silicone oil
The r) hot and humid environment (60 ° C., after storage for 10 days at 95%), the drop-out rate of increase after storage under high humidity environment (4
After storage at 5 ° C. and 80% for 4 days) was measured.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

Further, in Comparative Example 1, chlorine ions and sulfate ions were added to the back coat layer coating material in amounts of 2 and 2, respectively.
When the content is more than 0 ppm, in this case as well, the effect can be seen when 0.5 PHR of silicone oil is added to the coating material for the back coat layer, compared to the case where it is not added, but the dropout increase rate Is not sufficiently reduced.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

Further, Comparative Example 2, the paint chlorine ions and ions 1ppm Not respective sulfate for a back coat layer
When it is full , in this case 0.5 for the paint for the back coat layer.
When the PHR silicone oil is added, the still characteristics are more effective than when the silicone oil is not added, but the decrease rate of magnetic flux (Δφr) and the increase rate of dropout are not so effective as the addition of silicone oil. I can't.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

From the above, in the case where the coating material for the back coat layer contains 1 to 20 ppm of chlorine ions and sulfate ions, the addition of silicone oil has a great influence on the deterioration of magnetic properties and durability. You can see that By the way, chlorine ion is 1.0ppm, sulfur
For coating of back coat layer with acid ion of 0.8ppm
In addition, the still characteristics before adding silicone oil
Property, decrease rate of magnetic flux (Δφr), increase rate of dropout
Are 52 (min), 8 (%), and +200, respectively.
(%) And still after addition of silicone oil
Characteristics, magnetic flux decrease rate (Δφr), dropout increase
The rates are 120 or more (min), 8 (%), and +7, respectively.
(%)Met.

Claims (1)

[Claims] 1. In a magnetic recording medium, a ferromagnetic metal thin film is provided as a magnetic layer on one main surface of a non-magnetic support, and a non-magnetic pigment is dispersed in a binder on the other main surface. A magnetic recording medium comprising a back coat layer, wherein silicone oil is added to a paint for the back coat layer containing 1 to 20 ppm of chlorine ions and sulfate ions used for the back coat layer.