JPS58168655A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording material which has a high practical adhesion between a ferromagnetic layer and a substrate, and high overall endurance for use under severe conditions, by providing a ferromagnetic layer composed of metal (compd.) on a specified high-molecular material molding. CONSTITUTION:A polymer having an intrinsic viscosity of 0.5 or above and contg. at least 50mol% of a (chlorine-substd.) arom. polyamide of the formula (wherein m, n are each 0-3) is molded to obtain a high-molecular material molding in the form of film or sheet which has a thickness of 1mu-1mm. and tensile modulus is 400-10,000kg/mm.<2> and in which 10% heat shrinkage factor at 200 deg.C is 0-10% under no load conditions. Metal (compd.) such as Ni, Co, Cr or Fe is deposited in a thickness of 0.01-1mu on one side of the molding to form a ferromagnetic layer. EFFECT:A magnetic recording material which has excellent high strength, elongation and tensile modulus and good dimensional stability to changes in temperature and environment can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium in which a ferromagnetic layer is formed on a polymer molded product, particularly a polymer film, by vapor deposition, sputtering, or the like.

In recent years, increasing the density of magnetic recording has attracted attention as a requirement of the times, but the conventional γ-Fe20. An oxide magnetic powder such as oxide magnetic powder or an alloy magnetic powder such as cobalt or nickel is mixed uniformly into a suitable organic polymer binder and applied. In contrast to so-called coating type magnetic recording, a ferromagnetic layer consisting of a ferromagnetic metal thin film that does not contain a polymeric binder such as cobalt is directly formed on the substrate using methods such as vacuum evaporation or sputtering. Media have been developed in a form that is extremely advantageous for high-density recording.

The biggest problem when putting into practical use a magnetic recording medium provided with such a ferromagnetic layer is the adhesion strength between the base material and the ferromagnetic layer.

Such a ferromagnetic layer generally has a thickness of around 1,000 angstroms, and the surface smoothness of the base material is required to have conditions that are incomparably more severe than those of conventional coating types. Anchor effects cannot be expected at all. Furthermore, since the ferromagnetic layer is made of a single metal or metal compound, it itself has poor elongation, and unlike the coated type, it does not have the buffering effect of a binder, making it brittle against external forces. Furthermore, since the base material is generally made of organic polymers, conventional coating methods use an organic binder to improve compatibility with the base material, but this method has the inherent problem of adhesion between organic and inorganic materials. .

Various methods have been used to improve the adhesion of such ferromagnetic layers. For example, in the case of vapor deposition, the electron beam vapor deposition conditions may be varied to select the optimum conditions for adhesion, or the most commonly used base material, polyethylene terephthalate film, may be subjected to glow discharge treatment or puff treatment immediately before vapor deposition. Many efforts have been made to apply so-called surface treatments such as surface treatment. However, it is difficult to substantially improve adhesion using such methods. First of all, adhesion is not just a cellophane tape peel test, but also a magnetic recording medium, especially a magnetic tape, that comes into contact with a head or a roll in a running system, causing it to break off. There is a background in which adhesion in a broad sense, such as whether it is scratched or not, becomes a practical problem. For example, in video tapes, etc., there is contact with the head at high relative speed, and during stills, there is repeated contact at the same point.

Furthermore, they are exposed to extremely harsh conditions, including contact with posts. It is required that the adhesion is so excellent that there is almost no dropout even after running 50 or 100 times. Secondly, the rigidity and toughness of the ferromagnetic layer itself are important for adhesion in a practical sense, and even if the surface of the base material is sufficiently treated, it may affect the properties of the deposits. would be small. Third, physical surface treatment may have a fatal adverse effect on the surface smoothness of the base material, which is most important for magnetic recording media provided with a ferromagnetic layer, as described above.

In addition to this adhesion, the following durability is required in order to obtain a magnetic recording medium that is comprehensively excellent.

(1) High mechanical properties. In other words, it has excellent tensile modulus in addition to strength and elongation. (Dimensional stability against external forces) (2) Excellent dimensional stability at high temperatures.

(3) Excellent dimensional stability against environmental changes such as temperature and humidity.

The inventors of the present invention have conducted intensive studies to solve these various problems, and as a result, they have arrived at the present invention. That is, an object of the present invention is to provide a magnetic recording medium that has practical adhesion between a ferromagnetic layer and a base material and has high overall durability against severe use.

The present invention has the following configuration to achieve the above object.

That is, in a magnetic recording medium in which a polymer molding is provided with at least one ferromagnetic layer made of a metal or a metal compound, the polymer molding has a general formula (where m and n are 0 to 3).
The present invention is characterized by a magnetic recording medium having a structure containing 50 mol or more of the basic structural unit represented by (an integer of ).

The polymer molded article in the present invention is a wholly aromatic polyamide or chlorine-substituted material whose composition is as described above and whose bonds are para-para bonds, para-meta bonds, meta-para bonds, or meta-meta bonds. 50% fully aromatic polyamide
It is a film or sheet having a structure containing more than molti.

Examples of monomers constituting a base material mainly composed of a wholly aromatic polyamide or a chlorine-substituted wholly aromatic polyamide having this structure include terephthalic acid chloride, 2 2.5-dichloroterephthalic acid chloride, 2.6-Schiff.

Luterephthalic acid chloride, isophthalic acid chloride.

2-chloroisophthalic acid chloride, 2,6-dichloroisophthalic acid chloride, etc. and p-phenylenediamine, 2-
Chlor p-phenylenediamine, 2,5-dichloro-p-
Phenyl diamine, 2,6-dichloro-p-phenylenediamine, m-phenylenediamine, 2-chloro-m
-7 enylenediamine.

2,5-cyclo-m-7 enylenediamine natka.

It is essential that the basic structural unit represented by the above general formula is 50 mol or more of the base polymer used in the present invention.

It is more desirable that the basic structure is an aromatic polyamide, and more preferably that it has a chlorine substituent. If the basic structural unit is less than 50 molar grooves, the adhesion force of the ferromagnetic layer will decrease, and at the same time, the original properties as a support substrate for magnetic recording media, such as mechanical properties and moisture absorption dimensional stability, will deteriorate. Not satisfied with invention. Note that there are no particular limitations on the composition of less than 50 molti.

The following structural units can be cited as representative examples.

Here, X is 10H, -No2 or a halogen other than C1, and p and q are integers from 0 to 3, and cannot be 0 at the same time.

-CH2-, -0@-0-, -0°C-8O210-, and S is an integer from 0 to 3.

The polymer molded article of the present invention has a film or sheet shape and a thickness of 1 micron or more and 1 mm or less, preferably 3 microns or more.

It is 500 microns or less. This polymer molded product is 200
It is desirable that the thermal shrinkage rate at 10 inches at 10 degrees Celsius is 0 inches or more and 10% or less, preferably 0 inches or more and 296 or less, under substantially no-load conditions. Furthermore, since the ferromagnetic layer of the magnetic recording medium is a metal layer and has virtually no elongation, it is inconvenient that the base material is deformed by external force. Furthermore, since this field aims at unprecedented high-density recording, it is difficult to deform the tape body due to tension during tape running, for example. Therefore, the polymer molded article constituting the present invention has a tensile modulus of 400 or more and 10. OD'Okg/mm2 or less, preferably 50
It is desirable that it is 0 or more and 5,000 kg/mm2 or less. The characteristics of these substrates are in the state in which they constitute a magnetic medium, and can be measured by removing the ferromagnetic layer using an appropriate method, but the thickness of the magnetic layer is so thin that its influence can be ignored. Since it is small, it can be considered to be a characteristic of the entire magnetic recording medium. 1 Such a base material is manufactured as follows.

That is, the polymer is synthesized by low-temperature solution polymerization in an organic polar solvent such as N-methylpyrrolidone, dimethylacetamide, or γ-butyrolactone, or by interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride is produced as a by-product, so an inorganic neutralizing agent such as calcium hydroxide or an organic neutralizing agent such as ethylene oxide is added to neutralize this.

This polymer solution may be used as it is as a film-forming stock solution for forming a base material, that is, a film, or the polymer may be isolated once and then redissolved in the above-mentioned solvent to prepare a film-forming stock solution. In some cases, inorganic salts such as calcium chloride, magnesium chloride, etc. are added to the membrane forming stock solution as a solubilizing agent.
The amount of the nine types added varies depending on the amount of basic structural units, the type of copolymerized units, etc.

In order to obtain a film with practical strength, the intrinsic viscosity of the polymer must be 0.5 or more.

At that time, the polymer concentration in the membrane forming stock solution is preferably about 2 to 40 wt%. Here, the intrinsic viscosity of the polymer is 0.5
g to 100ml of N-methylpyrrolidone containing 2.5 wt% lithium bromide! Measured as a solution at 30°C and is representative.

The membrane forming stock solution prepared as described above is formed into a film by a so-called solution casting method. A thin film is formed by casting and extruding the film-forming stock solution from a die onto a drum or an endless belt, and after removing the solvent or solvent and inorganic salt by a dry, wet, dry-wet process, etc., it is heat-set to form the final film. Although a film is obtained, the process and manufacturing conditions should be determined based on the characteristics of the polymer and the desired physical properties of the film. For example, by simultaneously or sequentially stretching the film at an area magnification of 1.0 to 90 at an appropriate stage of the process, it is possible to not only improve the mechanical properties of the film but also to make the film uniform in its flatness and thickness. Contribute greatly.

Additionally, heat setting is generally preferred for the film's dimensional stability at high temperatures; however, caution should be taken as heat treatment temperatures that are too high can lead to polymer deterioration and relaxation of orientation, conversely deteriorating the mechanical and thermal properties of the final film. is necessary.

The ferromagnetic layer of the present invention refers to a so-called thin film magnetic layer,
A ferromagnetic layer made of metal or metal compound, specifically Ni, Co, Cr, Fe, 1-Fe2O3
The main component is a simple substance or an alloy such as.

Further, this ferromagnetic layer has a thickness of 0.01 to 1μ, preferably 0.001 to 0.5μ, more preferably 0.05 to 0.
．． It is desirable that the thickness be 20μ.

The method for forming the ferromagnetic layer is the vapor deposition method, in which metals and alloys are heated and evaporated in a vacuum and deposited on the substrate.

Furthermore, it is formed using well-known methods such as sputtering method, which uses ionized argon activated by electric discharge in a high vacuum to drive out molecules of the target metal or metal compound, and deposits them on the substrate, as well as other ion plating methods. You can do that.

In forming the ferromagnetic layer, cobalt is the single element with the best magnetic properties and good adhesion, and a small amount of nickel is added to improve the corrosion resistance, and chromium is added to improve the corrosion resistance in the vertical direction. It is possible to create a film that is easily magnetized. The vapor deposition method uses electron beam heating to generate a vapor flow of ferromagnetic material, and deposits it on a film in contact with a cooling drum or the like to a thickness of 0. It is desirable to form a controlled thin film of ~0.5μ, preferably 0.05-0.20μ. The degree of vacuum here is generally from 10-7 to 10-2r0-2rr, and in relation to the magnetic properties, external gases such as oxygen, nitrogen, and argon may be actively introduced into the deposition atmosphere. .

In the present invention, it is preferable to perform glow discharge treatment in an argon or oxygen atmosphere 1, for example, in a vacuum degree of 10-2 to several mmHg, as a pretreatment for vapor deposition, and the adhesive strength will be lower than in the case of no treatment. A clear significant difference is observed.

Furthermore, the magnetic recording medium of the present invention has good thermal stability at high temperatures because it is based on a polymer molded product containing 50 moles or more of 9% basic structural units.

It can withstand the heat generated during deposition and therefore
Numerous constraints during vapor deposition 1. For example, it is necessary to introduce a means to cool the substrate to 80°C or less, or to reduce thermal deformation 1 of the substrate, that is, without sacrificing magnetic properties or durability. Not just good.

Furthermore, heat treatment can be applied to the base material during or after vapor deposition, and the adhesion can be significantly improved by such treatment. This is considered to be because the cohesive force of the metal film increases and the molecular conformity of the interface with the base material is strengthened. In addition,
The treatment temperature is 100°C or higher and 400°C, preferably 12°C.
It is desirable that the temperature be within a range where the characteristics of the ferromagnetic layer do not deteriorate at temperatures above 0°C and 250°C. Furthermore, the effects of this method are further enhanced when heat treatment not only improves adhesion but also changes the chemical properties, crystal structure, and crystal morphology of the thin film and improves magnetic recording characteristics.

As described above, the magnetic recording medium of the present invention has superior performance compared to conventional coated magnetic recording media, thin film magnetic recording media based on polyester films, and existing heat-resistant films (for example, DuPont's "Kapton"). have Namely, high adhesion, dimensional stability at high temperatures, and dimensional stability against external forces.

Furthermore, it is a high-performance, high-density magnetic recording medium that has excellent overall characteristics such as dimensional stability under the environment in which it is used.

A specific application of the present invention is video tape.

It provides materials suitable for audio tapes and various floppy disks. Furthermore, the present invention can be applied to the field of all kinds of magnetic recording materials such as electronic cameras and video discs. Further, the magnetic recording method does not matter whether horizontal magnetization or perpendicular magnetization is used.

Note that a protective layer may be provided on the magnetic layer of the present invention.

It is often preferable to provide a back coat layer on the back surface of the film substrate for running properties, antistatic properties, and other purposes since this improves the performance of the magnetic recording material as a whole.

The magnetic recording medium of the present invention and the film as a base material were evaluated based on the following criteria.

(1) Intrinsic viscosity It was calculated using the following formula.

/n (ηrel) ηinh = Niko where ηrel is the relative viscosity measured at 25°C, C is 0°5
100 gr polymers! The value obtained when D/ was dissolved in a solution of N-methylpyrrolidone and 2.5 gr of lithium bromide was used.

(2) Strength and elongation, tensile modulus Measured at 20° C. and 75% RH using 1 tensilon” in accordance with J Engineering 5L-1073.

(3) A film with a heat shrinkage rate of about 25 (up to) was cut out to a width of 5 mm and marks were made at intervals of 20 cm, and a load of 5 gr was applied to the lower end of the cut film while it was being hung at a predetermined temperature. After 10 minutes, the sample was taken out, the distance between the marks was determined, and the heat shrinkage rate was calculated.

(4) Humidity expansion coefficient: A tape-shaped sample cut out to a width of 5 mm and a length of 20a11 was left at 20°C and 7096RH for 24 hours.

The conditions of the constant temperature and humidity chamber were changed to 904RH, the tape length was continuously measured, and the humidity expansion coefficient was calculated from the value after equilibrium was reached.

(5) Adhesion Although various methods were considered for testing the adhesion between the film substrate and the metal thin film, results with good reproducibility were mainly obtained using actual equipment testing using a video device. For the actual machine, a commercially available "Betamax" was used to cut the sample into tapes with a length of 1m to 10rn.

By repeatedly feeding the thin film, we observed how the thin film was damaged. Similar observations were also made after leaving the device in a still state for a long time.

Next, embodiments of the present invention will be described based on Examples.

Example 1 200 liters of dry N-methylpyrrolidone! Put 100% in a stirring tank and add 8% of lithium chloride to it. , 2-chlor p-phenylenediamine 2.42 yen, 4.4'-diaminodiphenyl ether 0.60 y were dissolved and kept at 0°C,
The whole thing was stirred. 4.07q of terephthalic acid chloride granulated for about 30 minutes with continuous stirring
was added. After stirring for 1 hour, a viscous polymer solution was obtained. A large amount of water was placed in a large mixer, the polymer solution was added thereto, and the mixture was re-precipitated to obtain a fibrous solid polymer. Wash this.

After drying, 2 bags of polymer, 1 kg of lithium bromide, 40 I of N-methylpyrrolidone! A homogeneous solution was prepared at room temperature. The intrinsic viscosity of this polymer was 4.57. This liquid was uniformly cast from a nozzle onto a stainless steel drum whose surface had been polished, and heated in an atmosphere of 120° C. for about 20 minutes.

- This film was peeled off from the drum and continuously immersed in a water tank for about 10 minutes.

This film was heated in a tenter at 300° C. for about 5 minutes at a constant length to obtain a transparent film with a thickness of 16 μm and a smooth surface.

This film has a strength of 40kg/mm2. Tensile modulus 1
500z/mm2, and the heat shrinkage rate at 250°C was only 0.3cm, making it an extremely strong and heat-resistant film. Also, the coefficient of thermal expansion near room temperature is 4 x
10-'mm/mm/'℃, humidity expansion coefficient 5 x 1
It was also found that it has excellent environmental stability with 0-'mm/mm/RH%.

This film was loaded into a vacuum chamber, and the A
Ion bombardment was performed in an r gas atmosphere. Next, the vacuum chamber was evacuated to the 10-') level, and while the film was running, Co was deposited by electron beam evaporation.
- Fabricate a magnetic tape having a thin ferromagnetic metal layer by depositing an inhibitory alloy (75% by weight of Co, 25% by weight of Ni) to a film thickness of 0.15 μm using an oblique evaporation method with an incident angle of 70° or more. did. The magnetic properties of the obtained film are such that the coercive force in the longitudinal direction is 7200θ1, the coercive force in the width direction is 4800e,
The squareness ratio is 0.92.

As a longitudinally oriented magnetic tape, it has performance suitable for audio tapes and video tapes.

We ran this magnetic tape on a commercially available home video system, Betamax, and ran it 100 times and subjected it to a chill test.The results showed that the adhesion of the magnetic layer was extremely good, and there was hardly any drop-off of the magnetic layer or deformation of the tape. It was confirmed that there was no increase in dropouts.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 using a polyethylene terephthalate film (1 Lumirror, manufactured by Toshi Corporation, 16 μm) and a polyimide film (Kapton, manufactured by DuPont, USA, 25 μm) as a base.

In the case of polyethylene terephthalate, there are frequent holes caused by heat during ion bombardment treatment and vapor deposition treatment.
It was impossible to make long tapes. In addition, as a result of running this with "Betamax", it was confirmed that the magnetic layer was partially destroyed or fell off due to multiple runs or still running, and the adhesion with the metal layer such as polyethylene terephthalate was insufficient. Ta.

In the case of ``Kapton,'' there was no heat loss during production, but it was not possible to obtain a tape with stable magnetic recording properties, perhaps due to poor surface smoothness. In addition, good tape properties could not be obtained due to the tape's stiffness and poor dimensional stability against humidity (humidity expansion coefficient: 52 x 10-' mm/mm/RH%).

Example 2 A magnetic thin film made of a Co--Cr alloy was formed on the 16 μm thick film obtained in Example 1 using a magnetron type RF sputtering device.

First, a film is loaded into a vacuum chamber and the vacuum chamber is evacuated to 10-'), and then Ar gas is introduced and 2×10-21-
− Maintain the pressure at Then, Co − with a diameter of 150 mm
Cr alloy target (Co81% by weight, Cr19% by weight
) was applied with a high frequency voltage of 13.56MHz.

Sputtered for 30 minutes with input power of 200W to a thickness of 05μ
A magnetic thin film was obtained. The coercive forces of this Co-Cr film in the directions perpendicular and parallel to the film surface were 11000θ and <SOO, Oe, respectively. In addition, this magnetic thin film has characteristics that make it suitable as a perpendicular recording medium, as the residual magnetization in the direction perpendicular to the film surface is larger than the residual magnetization in the direction parallel to the film surface, and it has an axis of easy magnetization in the perpendicular direction. There is.

As a result of testing the durability of this tape using a commercially available video device, it was found that the adhesion between the base film and the magnetic layer was sufficiently excellent.

Example 6 An iron oxide thin film was formed on the 16 μm film obtained in Example 1 using a magnetron type RF sputtering device using a sintered body of MaFθ304 as a target.

First, a film is loaded into a vacuum apparatus, and after the vacuum is evacuated to io-' Torr, Ar gas containing 6 volumes of oxygen gas is introduced to maintain the pressure at 5 x 10-5 Torr. Next, a high frequency voltage of 1!1.56 MH2 was applied to the target, and sputtering was performed for 15 minutes at an input power of 20 QW to form a Fe, 04 film with a thickness of 0.2 μm. continue,
This film was heated at 260°C in the atmosphere.

It was heated and oxidized for 60 minutes to convert it into a 1-Fe2O3 film.

The obtained γ-Fθ20. The film exhibited magnetic properties with a coercive force of 3500e, a residual magnetic flux density of 1500G, and a squareness ratio of 081.

Even after high temperature treatment, this tape achieves t1! Almost no deformation was observed, and it was confirmed that the durability of the magnetic layer was sufficiently practical as in Example 1.2.

Example 4 Lithium chloride 10q, 2-chlorop in 1001 N,N' dimethylacetamide dried as in Example 1
- 2.00 y of phenylene diamine and 1.19 y of 4.4'diaminodiphenylmethane were dissolved and kept at 0°C.

Next, 408 g of terephthalic acid chloride was added to obtain a solid polymer in the same manner as in Example 1. The intrinsic viscosity of this polymer was 2.89. 2 kg of polymer, 11 calcium chloride
1q (251!) of N-methylpyrrolidone was mixed to obtain a transparent film with a thickness of 16 μm and a smooth surface in the same manner as in Example 1.

This film has a strength of 32 kg/mm2. It showed a tensile modulus of elasticity of 950 kg/mm 2 and a heat shrinkage rate of 1.2% at 250° C., indicating that it was a high-strength, heat-resistant film. Also, the coefficient of thermal expansion is 6 x 10-' mm
/rmrr/ °C, humidity expansion coefficient is 11 x 10-'
mm/mm/RH%.

A magnetic tape was prepared using the base film of this example in the same manner as shown in Examples 1 to 3, and although it was somewhat inferior to the film of Example 1, it was confirmed that it exhibited sufficient practical performance.

Comparative Example 2 N,N' dimethylacetamide dried in the same manner as in the previous example
1001! 2-chloro-p-phenylenediamine 1 in
．． 14 positions, 4.4'diaminodiphenylmethane 2.3
8q was dissolved and kept at 0°C. Next, 4.07 kB of terephthalic acid chloride was added to obtain a solid polymer having an intrinsic viscosity of 252 in the same manner as in Example 1. 2 kg of polymer, 25 kg of N-methylpyrrolidone, and 0.5 z of calcium chloride were mixed and a smooth film with a thickness of 15 μm was obtained using the same process as in the previous example.

This film had a high moisture absorption rate of 6.8 inches and a humidity expansion coefficient of 20 x 10''mm/mm/RH%, making it unsuitable as a base film for magnetic tapes. It also had poor heat resistance, exhibiting a thermal shrinkage of about 5.3 inches at 200°C, and frequently suffered from heat loss during vapor deposition. Furthermore, the durability of the obtained magnetic tape was tested many times, and as a result, the magnetic layer often fell off, similar to the case with polyethylene terephthalate paste.

Patent Applicant: Toshi Co., Ltd. Company Procedures Amendment Letter: Kazuo Wakasugi, Commissioner of the Patent Office1, Indication of Case, Patent Application No. 51895 of 1982, Title of Invention: Magnetic Recording Medium, 3, Person Making Amendment Case Relationship with Patent Applicant Address 2-2-6 Nihonbashi Muromachi, Chuo-ku, Tokyo Contents of the amendment in Column 2 “Detailed Description of the Invention” of the specification to be amended (1) Specification Page 11, line 4 "The main component." should be changed to "The main component is the main component."

This layer is formed using a dry method. ” he corrected.

(2) Same page 11, line 14 "Well-known method" is corrected to "well-known dry method."

Claims (1)

[Scope of Claims] A magnetic recording medium in which a polymer molding is provided with at least one ferromagnetic layer made of a metal or a metal compound, wherein the polymer molding has a basic structural unit represented by an integer in the general formula. A magnetic recording medium characterized by having a structure containing 50 molti or more.