JPS60191430A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a metallic thin film magnetic recording medium which has superior strength, size stability, and heat resistance, less dropouts after being made into a magnetic tape, and superior run performance and electric characteristics by specifying the properties of a film or sheet type nonmagnetic base made of a crystalline high polymer material. CONSTITUTION:The nonmagnetic base uses a film obtained by drawing the film made of the crystalline high polymer material which has a >=120 deg.C secondary dislocation point and a >=280 deg.C fusion point. For example, the mean surface roughness (CLA) of the surface of the base is <=0.08mum, maximum projection height (PV) is <=0.5mum, and the numbers of projections which are 0.27-0.54mum high is 0.2/mm.<2>. In this case, noises after the film is made into the metallic thin film magnetic recording medium are reduced greatly and the noise level is very superior. Further, a solution obtained by dispersing a lubricant in water or a solvent is applied to form a lubricant layer so as to give slidability to the reverse surface of the surface where a ferromagnetic metallic film is formed.

Description

[Detailed description of the invention] The present invention relates to magnetic recording media.

Specifically, a ferromagnetic metal film is formed on a molded product made of a polymer material, particularly a film or sheet made of a polymer material (hereinafter sometimes abbreviated as "film, etc.") by vacuum evaporation, sputtering, plating, etc. The present invention relates to a magnetic recording medium that has a low noise level and a good S/N ratio when reading data, and particularly has a low noise level when reproducing high-density recording.

In recent years, increasing the density of magnetic recording has attracted attention as a requirement of the times. In other words, conventional oxide magnetic powder such as γ-Fe, O, etc. or alloy magnetic powder such as C01N1 is mixed uniformly into a suitable organic polymeric binder and applied to the so-called coating type magnetic recording medium. On the other hand, magnetic recording involves forming a ferromagnetic layer made of a ferromagnetic metal thin film that does not contain a polymeric binder such as cobalt directly on the substrate using techniques such as vacuum evaporation, sputtering, or plating. The medium is attracting attention as a high-density magnetic recording medium.

However, attempts have been made to use polyethylene terephthalate film, which has been conventionally used in magnetic tapes, as a base film or sheet for such high-density magnetic recording media, but it is still insufficient in various properties. Furthermore, it is hoped that a base film with excellent properties as described below will emerge. (1) Films with higher mechanical properties, i.e., higher tensile modulus as well as strength and elongation, (2) Films with excellent dimensional stability at high temperatures, (3) Temperature changes, humidity changes, etc. These are films with even better dimensional stability against environmental changes. In particular, the above-mentioned modification (2) can increase the temperature of the film when forming the ferromagnetic metal by vapor deposition, plating, etc., so it can improve the adhesion between the film and the magnetic layer. In view of the above points, the inventors of the present invention have conducted intensive studies and found that a film made of a specific polymer, that is, a crystalline polymer with a high secondary transition point and a high melting point, is used as a base film. It has been found that a magnetic recording medium made of a polyethylene terephthalate base film has significantly superior properties in terms of the above-mentioned required characteristics, compared to a magnetic recording medium made of polyethylene terephthalate as a base film.

However, when such a film is simply melt-extruded, molded, and then stretched to produce a base film for a magnetic recording medium, it has excellent properties as described above, but it is difficult to industrially produce a film for vapor deposition. turned out to be impossible. In other words, if such a film or the like is simply melt-extruded and stretched, no protrusions will be present on the surface and the surface of the film or the like will be too smooth. Therefore, when handling films, etc., such as winding and unwinding, the slippage between the films, etc. is poor, and a blocking phenomenon occurs, causing the films, etc. to stick to each other, and if you try to forcefully peel them off. It was found that the surface of the film etc. was damaged and could not be used as a product. As a result of intensive studies, the present inventors 3- et al. found that a solution to this problem could be achieved by adding inorganic fine particles to such films, etc., in order to improve handling properties. If too many fine particles are added, when a high-density magnetic recording medium is created, the metal thin film is thin and the surface condition (surface unevenness) of the non-magnetic support directly appears as unevenness of the magnetic layer. It was also found that this caused noise. As described above, it has been found that while the surface of the non-magnetic support is required to be smooth from the standpoint of electromagnetic conversion characteristics, it is necessary for the surface to have irregularities from the standpoint of non-linking properties. However, the present invention has been arrived at through extensive research in order to satisfy both of these contradictory properties at the same time.

That is, the gist of the present invention is a magnetic recording medium in which a ferromagnetic metal film is formed on one side of a film or sheet-like nonmagnetic support made of a crystalline polymer, the nonmagnetic support having a secondary transition point. /, a crystalline polymer with a melting point of 2gθ°C or higher at 10°C or higher 4- A film or sheet obtained by stretching a large unstretched film or sheet in at least one direction Surface roughness 0LA) is 0.0θgμm or less, maximum protrusion height P■) is 0.05μm or less, height is O, body μm or less (0,!rQ11m or less protrusions θ1.2 pieces/throat) 2 or less, a ferromagnetic metal film is formed thereon, and a lubricant layer is formed on the other surface of the film or sheet.

The present invention will be explained below.

The non-magnetic support of the present invention has a secondary transition point of /20°C.
It is a film, etc., drawn in at least one direction from an unstretched film made of a crystalline polymer having a melting point of 2 tO ℃ or higher.The polymer is not particularly limited as long as it satisfies the above requirements, but In view of ease of extrusion molding, polyetherketone, polyetheretherketone and their respective copolymers, and benzene rings with side chains are preferred.

In other words, for example, polyetherketone etc. is represented by the general formula,
It is also suitable to copolymerize components represented by the general formula according to the father's formula.

On the other hand, for example, polyether ether ketone is represented by the general formula, and it is also possible to copolymerize the formula (2) in the same way.

In the formula, ~R8 may be any substituent such as a hydrogen atom, a halogen atom, or a hydrocarbon group such as an alkyl group.

As for the method of forming films, unstretched films are obtained by melt extrusion using ordinary single layer extrusion, coextrusion, etc. by selecting a filter as necessary and using electrostatic adhesion. etc. above the secondary transition point of the polymer, 270
It is preferable to stretch in the −axis or biaxially at a temperature of ˚C or lower. It is also preferable to carry out heat treatment if necessary.

The stretching ratio is 3.0 times or more g, θ for uniaxially stretched films, etc.
About double or less, for biaxially stretched films, etc., both are the same, respectively.
It is preferably about 5.0 times or more.

The method of biaxial stretching is sequential biaxial stretching or simultaneous biaxial stretching. It is also preferable to perform vertical stretching again in order to increase the longitudinal strength, or to perform vertical and horizontal stretching again in order to increase the strength in both the vertical and horizontal directions. The film or the like made of the polymer of the present invention has a film or sheet shape and a thickness of /micron or more / millimeter or less, preferably 3 microns or more and 200 microns or less. It is desirable that this polymer molded product has a heat shrinkage rate of 7g at 0° C. for 10 minutes under substantially no-load conditions of 70% or less, preferably 1I% or less. In addition, since this field is aiming for unprecedented high-density recording, for longitudinal recording of audio, video, computers, etc., the tensile modulus in the longitudinal direction is 1 Ioo/0000 My/m or more. Below, preferably! It is preferable that it is not less than roo and not more than k 000 Kq/-. Also, for disk-shaped recording such as floppy disks, the tensile modulus in both directions is SOO or more 1.
0000 Kf/- or less is preferable.

All conventionally known methods can be used to form a ferromagnetic metal film, but vacuum evaporation, ion blating, sputtering, vapor growth, and electroless plating are particularly preferred.0 Vacuum evaporation In the case of the method, the vapor-deposited metal in a tungsten board or alumina hearth is vapor-deposited on the support by resistance heating, high-frequency heating, electron beam heating, etc. under a vacuum of 10-4 to 10-6 Torr. As the deposited metal, Pa, Ni, Oo, and alloys thereof are usually used. Further, the present invention can also be applied to a reactive vapor deposition method in which Fe is vapor-deposited in an atmosphere to obtain an iron oxide thin film. In the ion blating method, 10-4~/θ-” To
DC glow discharge and PF glow discharge are performed in an atmosphere mainly consisting of an inert gas of 8- rr, and metal is evaporated during the discharge. Ar is usually used as the inert gas. In the sputtering method, a glow discharge is generated in an atmosphere containing Ar as a main component at log~/O-' Torr, and the generated Ar ions knock out atoms on the target surface. Methods for generating glow discharge include direct current-pole/three-pole sputtering and high-frequency sputtering. There is also a magnetron sputtering method that uses magnetron discharge. In electroless plating method, Co-P
, Co-N1-P plating film.

The thickness of the ferromagnetic metal film according to the present invention must be such that it can provide sufficient signal output as a high-density magnetic recording medium, so the thickness of the ferromagnetic metal film varies depending on the thin film formation method and application. , generally 0.0.1-1. ! iJim C
200~/3000k).

In this way, by means of vapor deposition, sputtering, plating, etc.
Since the surface condition of the formed metal thin film is directly caused by the surface condition of the nonmagnetic support as irregularities, it is necessary to design the surface roughness of the nonmagnetic support.

If the average surface roughness of the surface of the nonmagnetic support is 0LA) or less, the noise when used as a metal thin film magnetic recording medium will be dramatically reduced, and the noise level will be significantly superior. Preferably,
Average surface roughness 0LA (o, number of objects in the range of 9 (N
1) is substantially O/-. The lower limits of OLA and pv are not particularly limited, but are about 0.00.7 μm and θ, 0/μm, respectively. The surface characteristics of the film, etc. on both sides of the film, etc., cause blocking phenomena, etc., and cannot be commercialized. Therefore, in order to impart slipperiness to the back side of the surface on which the ferromagnetic metal film, such as a film, is provided, a lubricant layer is formed by applying a solution of a lubricant dispersed in water or a solvent. The lubricant layer can be formed by coating in-line or outline after or before heat-setting, but it is particularly preferable to coat in-line before transverse stretching. Also, when applying lubricants, etc., inorganic fine particles are added to the coating solution, etc. After lateral stretching and heat setting, it is also possible to make it easier to slip by forming particulate, wavy, or mountain-like protrusions. suitable.

When forming particulate, mountain-like, wavy, etc. protrusions other than the lubricant layer, the surface characteristics should be 0.010≦OLA≦0.
020. It is preferable that θ, OA≦PV≦0.2. Normally, with a polyester film, if one side is roughened and the other side is flattened, set-off occurs during winding and the flat side becomes roughened, making it unsuitable as a deposition film. Perhaps because the surface is hard, there is no set-off like you see with polyester.

A method of easily forming the surface condition of the surface of the nonmagnetic support on which the ferromagnetic metal film is to be formed is to add inorganic fine particles to the polymer.

11- As the inorganic fine particles, an inert substance that is insoluble and does not react with the thermoplastic resin is used.

Examples of the substances used include MgO and ZnO.

Mg0O,,0aCO8,C! aso4. BaSO4
, At20. , 5in2°Tie, kaolin, diatomaceous earth, aluminosilicates and their hydrates, and other materials such as carbon black and calcium phosphate.

The desired surface quality can be obtained by combining the particle size, amount, etc. of the inorganic particles added. The particle size varies depending on the type of inorganic particle and purpose, but is usually 0. ! r~
A material with a diameter of about 10μ is used. The amount added depends on the particle size distribution and cannot be determined in general, but it is usually 0.07 to 2wt.
% is preferably 0. As a method for forming the surface of the nonmagnetic support on which the lubricant layer is provided, in addition to the coating method described above, it is also preferable to form it by lamination or the like.

Examples of the lubricant include organic lubricants such as sorbitan, organic polymer lubricants such as tetrafluoroethylene, and inorganic lubricants such as alumina, kaolin, silica, and molybdenum sulfide.

It is also a preferable method to mix a polymeric binder and a surfactant with the above-mentioned lubricant for the purpose of improving coating properties.

Unlike a polyester film, the film made of the polymer of the present invention does not involve precipitation of low molecular weight substances such as oligomers, and therefore there is no dropout caused by low molecular weight substances.

As described above, the present invention provides a film as a metal thin film magnetic recording medium that has excellent strength, dimensional stability, and heat resistance, has less dropout after being made into a -l/φ magnetic tape, and has excellent running properties and electrical properties. I can do it.

The present invention will be explained below with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof. The methods for measuring various properties of the film are as follows.

(1) Center line average roughness (OLA) Measured according to JIS BOAO/.

It was measured as follows using a surface roughness measuring device (SBj-3PK) manufactured by Koita Research Institute. The tip radius of the stylus is 1 μm and the load is 30 μm. A part with a reference length L (2,5 mm) is extracted from the film cross-sectional curve in the direction of its center line, and the center line of this extracted part is the Y axis, and the direction of vertical magnification is the Y axis, and the roughness curve y = f When expressed as (x), the value given by the following formula is expressed in μm. However, the cutoff value is 30 μm. For Ra, the average value of a total of 10 points, 5 points in the vertical direction and 5 points in the horizontal direction, was determined.

(2) Surface roughness The protrusions on the surface of the aluminum-deposited film were measured using a Nippon Kogaku surface finishing microscope using multiple interferometry (measurement wavelength O, Saμ). , quantified as the number of seventh-order and second-order interference fringes, and expressed as the number per -.

N,: Number of protrusions observed as interference fringes with 0.27≦h≦OJ'111m (3) Friction coefficient bowl (s) On a fixed hard chrome-plated metal roll (diameter 6 questions),
Wind the film and contact it at an angle of 35 degrees (θ), &,?
I! Applying a load of (T2) on one end and running it at a speed of /ln/m+, the resistance force on the other end (T, (,9))
was measured, and the coefficient of friction during running was calculated using the following formula.

(4)? , value 772 inches wide, between chucks! Sample film of θ ■ length manufactured by Toyo Baldwin Co., Ltd. (UTM-II+
) at 20℃ and 63%RH! ;Own/m
The load at the time of tension and S% extension was divided by the initial cross-sectional area and expressed in units of K97m1.

Example/Composition I has a particle size composition ratio of /, 5≧d,> when melting polyetherketone powder obtained by a conventional method.
0. ! (Unit/μm) 3.0% θ, S≧d〉θ
1.2 33.7% 0.2≧d 15- A3.3% calcium phosphate additive particles O1 left wt
% and pelletized.

On the other hand, composition (2) has a particle size composition ratio/S≧a > O, S 1g% o, h≧d > 0. Yu's thing'l 3.
/, %0.2≧d S/, 3% kaolin 0. !
r wt% was mixed and pelletized.

The thickness composition ratio of each layer of the laminate of composition I and composition H is /:/
An unstretched film with a thickness of 1 gS .mu.m was prepared by coextrusion so as to have the following properties. Their secondary transition point was /jlI'c, and their melting point was 367°C. This unstretched film was first heated at 0°C 3.6 times in the machine direction and 7 gθ°C in the transverse direction. Sequential biaxial stretching was carried out twice as much, and heat setting was carried out at 3 °C./! f
A μm film was produced.

16-0 polyethylene glycol (8 screw type) [, ff1) f
/9ρρρ) 2wt% solution... 5Kf O polyethylene glycol diglycidyl ether (Nagaushi Sangyo NBRO/0■) 2wt% solution..., 2K
yO polyoxy-engineered tyrene nonyl phenyl ether wt
Solution.../9 to 9 The amount applied is approximately 2. ．． 2g/lrI′,
The solid content is approximately θ, 0/, 2AI//rr? It is.

The film thus obtained had good slipperiness, no blocking occurred, and could be wound up well. The stress of this film when stretched by S% in the longitudinal direction is i6. oKyAJ, and the initial elastic modulus in the longitudinal direction was 4/Mo'' at 7θθ.The heat shrinkage rate at igo℃ for 10 minutes was extremely low at 85%.
It turned out to be a high strength, heat resistant film. The temperature expansion coefficient near the room temperature is 5 x / θ-6 / gate / °C, and the humidity expansion coefficient is also Q, g x / 0-'mn + / mm / RH.
% and excellent environmental stability) Nl is 0.37/- and /3. θ pieces/kaku 2 □Tatsuta.

This film was loaded into a vacuum chamber and subjected to ion bombardment under an Ar gas atmosphere of /f)-''Torr.

Next, the vacuum chamber is evacuated to the io-'toll level, and while the film is running, it is evacuated to 0o-N by electron beam evaporation.
i-alloy (Co?s wt%, Ni Miko wt%)
θ, /j−μ using an oblique evaporation method with an incident angle of 70°C or more.
A magnetic tape having a thin ferromagnetic metal layer was prepared by vapor deposition to a film thickness of .

We ran this magnetic tape on a commercially available home video camera "Betamax" and ran it 100 times and ran a methyl test, and found that it had excellent electrical properties and runnability, and the adhesion between the magnetic layer and the film was extremely strong, resulting in a low coefficient of friction. there were.

A magnetic layer was formed in Comparative Example/. As a result, the unevenness of the magnetic surface was too large, resulting in an extremely low output, making it unsuitable for use as a magnetic tape.

Comparative Example Particles similar to those in Example were added to copolyethylene terephthalate, and a film of /Sμ was prepared by coextrusion. In the case of this film, the phenomenon of perforation due to heat frequently occurred during ion bombardment treatment and vapor deposition treatment, making it impossible to produce a long tape. Furthermore, as a result of running this at a speed of 1 beta max, it was found that the adhesion between the polyethylene terephthalate and the metal layer was insufficient, as the magnetic layer was partially destroyed or fell off due to multi-stage running and stealth running. Ta.

Example Ko O0 left≧d>(1), Ko thing 3S, /chi Oo, 2≧
Chips were formed by adding 0.3 wt % of 1.7% kaolin containing d. This was melt-extruded to create an unstretched film of igrμm. Their secondary transition point 19- was 733°C, and their melting point was 3°C. This film with a thickness of 75 μm was obtained. A coating agent was applied to one side of this coaxially stretched film in the same manner as in Example 1.

The stress of this film when elongated by 3% in the longitudinal direction is / g,
! r Kg/lrrm" and the elastic modulus was gθθ12.

In addition, the heat shrinkage rate in the longitudinal direction was a little high at 0%, but no problem, and it was found to be a highly strong and heat-resistant film. The CLA value at this time is o, oogμm, and the PV value is 0.
0 A μ, N1 is 0. , 10 pieces/- were deposited on this film using a magnetron WRF sputtering device. ? A magnetic thin film of f-gold alloy υ was formed on the opposite surface to the coated surface.

First, a film is loaded into a vacuum chamber, and after the vacuum chamber is evacuated to 10-6 Torr, Ar gas is introduced to maintain the pressure at Co.times./.theta.-2 Torr. Then a Co-Or alloy target (Oog/wt%, Or/?wt) with a diameter of ISO/
,? A high frequency voltage of JAμHz was applied, and sputtering was performed for 30 minutes with an input power of 20 - θOW to a thickness of O,...
! A magnetic thin film of rμ was obtained. The coercive forces of this Co-0r film in the directions perpendicular and parallel to the film surface were /1000e and AOOOe, respectively. In addition, this magnetic thin film has characteristics that make it suitable for use 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. The μd of the coated surface at this time is 0. / It was 0.

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.

Applicant: Diafoil Co., Ltd. (7 others) Representative Patent Attorney Naga Kagawa - (7 others)

Claims (2)

[Claims] (1) A magnetic recording medium in which a ferromagnetic metal film is formed on one side of a film or sheet-like nonmagnetic support made of a crystalline polymer, the nonmagnetic support having a secondary transition point of 720°C or higher, It consists of a film or sheet made by stretching in at least one direction an unstretched film or sheet made of a crystalline polymer having a melting point of 230°C or higher, and one side of the film or sheet has a surface roughness of o, o o μm. Hereinafter, the maximum protrusion height (pv) is o, o sμm or less, the height is 0.2
θ higher than 7 μm! The film or sheet is characterized in that the number of protrusions of r+μm or less is 0.1/m2 or less, a ferromagnetic metal film is formed, and a lubricant layer is formed on the other surface of the film or sheet. magnetic recording medium. (2) The magnetic recording medium according to claim 1, wherein the crystalline polymer is polyetherketone or polyetheretherketone.