JP2887326B2 - Support for ferromagnetic metal thin film - Google Patents

Description

The present invention relates to a support for a ferromagnetic metal thin film. More specifically, the present invention relates to a support for a ferromagnetic metal thin film having good handling characteristics when a ferromagnetic metal thin film is formed on the support and used as a high-density magnetic recording medium.

[Background Art] A support for a ferromagnetic metal thin film has a ferromagnetic metal thin film formed thereon by a method such as vacuum evaporation, and is mainly used as a high-density magnetic recording medium. At this time, the function required for the support is the same as in the case of the coating type high density magnetic recording medium,
Not only the mechanical properties that support the magnetic layer, but also the surface shape that smoothly supports the extremely thin magnetic layer and imparts the desired electromagnetic conversion properties, and that the support itself has good handling properties, that is, slipperiness, etc. Has been requested.

Conventionally, biaxially oriented polyester films have been mainly used as a material for a support for a high-density magnetic recording medium, but attempts have been made to specialize the front and back of the film in order to satisfy the above requirements ( JP-A-49-74910, JP-A-51-149006, and JP-A-52-84264. That is, in order to satisfy good electromagnetic conversion characteristics, a surface (hereinafter, referred to as a magnetic surface) in contact with the ferromagnetic metal of the film is formed smoothly, and the opposite surface (hereinafter, referred to as a running surface) is roughened to facilitate smoothing. This ensures handling characteristics.

With this technology, the function of the support has been separated into a magnetic surface and a running surface, and development has proceeded. The magnetic surface is not only smooth, but is provided with a film having granular or earth-like projections on its surface to improve the head touch, abrasion resistance and durability of the ferromagnetic metal thin film (Japanese Patent Application Laid-Open No. 56-56). No. 16937, JP-A-58-68223, etc., and those having a head cleaning effect by surface protrusions based on residues of polymerization catalyst in films and added fine particles (JP-A-58-68225).
Japanese Patent Application Laid-Open No. 59-84927, etc.) and those in which fine particles are present in a film to improve durability under high temperature and high humidity. However, the running surface is not merely a matter of simply smoothing the rough surface, but it is not limited to transfer to the ferromagnetic metal thin film on the magnetic surface when wound up, and its smoothness and fine shape must not be impaired. There was an upper limit on the surface roughness, and it was necessary to combine with a slippery film (Japanese Patent Laid-Open No. 58-153639).

[Problems to be Solved by the Invention] In recent years, the progress of metal thin-film magnetic recording media has been remarkable, and high-quality vapor-deposited video tapes utilizing their suitability for high-density recording have been put on the market for consumer use. With the industrialization of vapor deposition tapes, the demand for improved handling properties for ferromagnetic metal thin film supports has become more stringent.

However, in the prior art, the improvement of the running surface is limited due to the above-described transfer limitation, and the handling characteristics have reached the limit. If the running surface is further smoothed to improve the handling characteristics, the surface shape is transferred to the ferromagnetic metal thin film as the magnetic layer, and the electromagnetic conversion characteristics are deteriorated.

An object of the present invention is to provide a support for a ferromagnetic metal thin film having extremely excellent electromagnetic conversion characteristics when formed into a ferromagnetic metal thin film type magnetic recording medium and having excellent handling characteristics at the same time. I do.

[Means for Solving the Problems] The present invention provides: (1) a biaxial composition comprising a thermoplastic resin and inert particles (A) contained in the resin as main components on a surface not in contact with the ferromagnetic metal thin film; It is made of a laminated film having a layer made of an oriented film, and has a surface projection having nuclei of inert particles (A) contained in the resin on a surface not in contact with the ferromagnetic metal thin film. The average height of the protrusions is 1/4 or more of the average particle size of the inert particles (A), and the thickness t of the biaxially oriented film layer containing the inert particles (A) and the inertness The ratio (t / D) of the particles (A) to the average particle diameter D is 2
A support for a ferromagnetic metal thin film, characterized in that: (2) a slippery coating on a surface of the support for a ferromagnetic metal thin film according to claim 1 which is not in contact with the ferromagnetic metal thin film. A support for a ferromagnetic metal thin film on which is formed.

The thermoplastic resin constituting the present invention is not particularly limited, but crystalline thermoplastic resins such as polyester, polyolefin, polyamide, and polyphenylene sulfide, among which polyester, polyphenylene sulfide, and particularly polyester are preferably used. Further, among polyesters, at least one structural unit selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and ethylene 2,6-naphthalate units is mainly used. The constituents are desirable for obtaining the surface morphology within the scope of the present invention. The term “crystalline” as used herein indicates that the material is not amorphous, and the melting point is quantitatively detected by thermal analysis using a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min. The crystallization parameter ΔTcg is 150 ° C. or less.

The inert particles constituting the present invention are not particularly limited. However, in the case of spherical particles having a particle diameter ratio (particle major axis / minor axis) of 1.0 to 1.3, it is preferable because the surface morphology within the range of the present invention is easily obtained. .

The inert particles constituting the present invention are not particularly limited, but the relative standard deviation of the particle size distribution is 0.6 or less, preferably
A value of 0.5 or less is desirable because a surface morphology within the scope of the present invention is easily obtained.

The types of inert particles include, but are not limited to, substantially spherical silica particles due to colloidal silica, particles of a crosslinked polymer (eg, crosslinked polystyrene), and the like, in order to satisfy the above-mentioned desirable properties. Instead, other particles, for example, titanium dioxide, alumina, calcium carbonate, etc. can be used properly by devising a film forming method.

The size of the inert particles (A) is not particularly limited, but the average particle size (diameter) is 5 to 2000 nm, particularly 10 to 1500 nm, and furthermore
When the thickness is 10 to 300 nm, the friction coefficient and output characteristics are further improved, which is particularly desirable.

The total content of the inert particles (A) and (B) in the present invention is not particularly limited, but the content of the entire film is 0.0005 to 0.0005.
When the content is 0.5% by weight, preferably 0.001 to 0.3% by weight, and more preferably 0.001 to 0.15% by weight, the handling characteristics and the output characteristics are further improved, which is particularly desirable.

The support of the present invention comprises a composition comprising the above thermoplastic resin and inert particles as a main component, but may be blended with other kinds of polymers as long as the object of the present invention is not impaired, or may be antioxidant. Organic additives such as additives, heat stabilizers, lubricants and ultraviolet absorbers may be added to the extent that they are usually added.
Further, a lubricious film, a non-smooth film, and a film containing fine particles may be formed on the surface. Further, organic particles may be closely attached to the magnetic surface side to form projections. The materials of these films and organic particles are not particularly limited, but known materials in the fields of magnetic recording and metal corrosion protection can be used. The method of forming the material is not particularly limited, but a method of diluting the material with water or a solvent, coating and drying the material is desirable.

The support of the present invention is a biaxially oriented film of the above composition. Uniaxial or non-oriented films are not preferred because the handling characteristics are poor. Although the degree of this orientation is not particularly limited, it is extremely desirable because the handling characteristics are further improved when the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 200 kg / mm ² or more in both the longitudinal direction and the width direction. . Although the upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, differs depending on the type of the thermoplastic resin and cannot be unconditionally determined, usually, about 5000 kg / mm ² is the manufacturing limit.

Abbe refractometer, refractometer using laser, total reflection laser Raman method, etc., from the surface excluding the coating on the running surface of the present invention to a depth of 1 μm (when the film thickness is 1 μm or less, When the molecular orientation (up to the opposite surface) is biaxial, it is particularly desirable because output characteristics and handling characteristics are further improved. Further, when the thermoplastic resin in this portion is crystalline, handling characteristics and output characteristics are further improved, which is particularly desirable.

In the support of the present invention, the average height of the surface projections on the surface of the running surface excluding the film is the inert particles (A) serving as nuclei of the projections.
1/4 or more, preferably 1 / 3.5 or more of the average particle size (diameter) of
More preferably, it is necessary to be 1/3 or more. If the average protrusion height of the running surface is less than 1/4 of the average particle size, it is not preferable because a film that achieves both output characteristics and handling characteristics cannot be obtained. The upper limit of the average projection height is not particularly limited, but the production limit is about 1.5 to 2 times the average particle size.

The surface protrusion height of the surface excluding the film from the running surface of the support of the present invention is not particularly limited, but the average height is 3 to 500 nm,
In particular, when the thickness is 10 to 250 nm, the output characteristics when formed into a magnetic tape and the film handling characteristics are further improved, which is particularly preferable.

The density of protrusions on the surface of the support of the present invention excluding the film from the running surface is not particularly limited, but the total number of protrusions on the surface satisfying the surface morphology defined in claim 1 is N (pieces / mm ² ). When the content Φ (% by weight) of the inert particles (A) and the average particle diameter D (nm) of the particles satisfy the following formula (1), preferably (2), more preferably (3): This is particularly desirable because the output characteristics and the film handling characteristics when formed into a magnetic tape are further improved.

N / (Φ / D ³ ) ≧ 5 × 10 ¹³ … (1) N / (Φ / D ³ ) ≧ 7 × 10 ¹³ … (2) N / (Φ / D ³ ) ≧ 10 × 10 ¹³ … (3 The support of the present invention has a ratio of the center line average roughness Ra to the maximum height Rt of the surface excluding the film from the running surface, and the handling characteristics and the output characteristics when Rt / Ra is 8.5 or less, particularly 8.0 or less. It is particularly desirable because it is even better.

As described above, the support of the present invention is desirably composed of a thermoplastic resin having a crystalline property. In particular, a surface layer portion excluding the film, particularly a polymer having a depth of 1 μm from the surface excluding the film from the running surface is preferred. It is particularly desirable that the crystallization parameter ΔTcg is 10 to 100 ° C., because the handling characteristics are further improved.

The support of the present invention is particularly desirable when the center line average roughness Ra of the surface excluding the film from the running surface is 1 to 100 nm, because the handling characteristics and the output characteristics are further improved.

The support of the present invention can be handled when the relative standard deviation (standard deviation of height distribution / average height) of surface projections on the surface excluding the film from the running surface is 0.5 or less, particularly 0.4 or less, and even 0.35 or less. The support of the present invention is particularly preferable because the properties and output characteristics are further improved.
It is particularly desirable that the surface particle concentration ratio measured by the secondary ion mass spectrum is 1/10 or less, particularly 1/50 or less, because the handling characteristics and output characteristics are further improved.

 Next, a method for producing a support of the present invention will be described.

First, as a method for incorporating the inert particles (A) into the thermoplastic resin, any method may be used after polymerization, during polymerization, or before polymerization, but a method in which the polymer is kneaded using a vented twin-screw extruder according to the present invention. It is effective to obtain a film having a range of surface morphologies. In addition, as a method of adjusting the content of the inert particles (A), a high-concentration master is prepared by the above method, and the master is diluted with a thermoplastic resin substantially containing no inert particles at the time of film formation. The method of adjusting the content of the particles is effective for obtaining the film having the surface morphology of the present invention. Further, the method of adjusting the melt viscosity of the high concentration master polymer of the inert particles (A), the copolymerization component, and the like to keep the crystallization parameter ΔTcg in the range of 30 to 80 ° C. does not cause stretching breakage, and is within the scope of the present invention. It is effective for obtaining a film in surface form.

Thus, after the pellet A containing the inert particles (A) is sufficiently dried, the pellet A is supplied to a known melt extruder, melted at a temperature not lower than the melting point of the thermoplastic resin and lower than the decomposition point, and the other is melted at a temperature of 150 nm or less. The thermoplastic resin B containing the active particles (B) or the thermoplastic resin C containing substantially no inert particles is supplied to a known laminating apparatus, extruded from a slit-shaped die into a sheet, and cast on a casting roll. And solidify by cooling to make an unstretched film. That is, these thermoplastic resins are laminated using two or three extruders, a merging block for two or three layers, or a die. In the case of using the merging block method, the present invention is to make the laminated portion rectangular, and to set the difference (absolute value) between the melt viscosities of both thermoplastic resins in the range of 0 to 2000 poise, preferably 0 to 1000 poise. This is effective for industrially producing a film having a range of surface morphologies stably and without unevenness in the width direction.

Further, in the state of the unstretched film, the ratio of the thickness t of the thermoplastic resin layer containing the inert particles (A) to the average particle diameter (diameter) D of the contained inert particles, t / D is 24 or less. It is very effective to produce a film having a surface morphology within the range of the present invention, preferably 12 or less, more preferably 8.5 or less.

The above is the case where the laminated structure is A / B, A / C, A / C / B, but it is needless to say that a multilayer structure of more than that may be used (here, A,
The types of thermoplastic resins B and C may be the same or different. The surface A is defined as the running surface of the present invention.

Next, this multilayer unstretched film is biaxially stretched and biaxially oriented. The method of biaxial stretching may be any of simultaneous biaxial stretching and sequential biaxial stretching, but in the case of sequential biaxial stretching in which the film is stretched in the longitudinal direction and width direction in order to stabilize the film of the surface form within the scope of the present invention. Therefore, it is effective for industrial production without unevenness in the width direction. In the case of sequential biaxial stretching, the stretching in the longitudinal direction is divided into three stages, especially four or more stages, in the range of 40 to 150 ° C., and at a stretching speed of 1000 to 50,000% / min.
The method performed three to six times is effective for obtaining a film having a surface morphology within the range of the present invention. The stretching temperature and speed in the width direction are preferably in the range of 80 to 170 ° C. and 1000 to 20000% / min. The stretching ratio is preferably 3 to 10 times. Further, if necessary, the film can be further stretched in at least one of the longitudinal direction and the width direction. In any case, the point of the present invention is to provide a very thin layer containing inert particles and then perform stretching of 9 times or more as an area stretching ratio (longitudinal ratio × width direction ratio). Next, this stretched film is heat-treated. The heat treatment conditions in this case are relaxation in the width direction, fine stretching, 140 to 280 ° C. in any state under constant length, and preferably 0.5 to 60 seconds in the range of 160 to 220 ° C. It is preferable that a film having a surface morphology within the range of the present invention can be easily obtained by using microwave heating together. When a film is to be formed on the film surface as required, a known coating step is provided immediately before the transverse stretching step or immediately before the heat treatment step, and when a material is applied, a drying step is not particularly required, which is desirable.

In the state of the product film, the ratio of the thickness t of the thermoplastic resin layer containing the inactive particles (A) to the average particle diameter (diameter) D of the inactive particles (A), t / D, is defined as It is extremely effective to produce a film having a surface morphology within the range of the present invention if it is 2 or less, preferably 1 or less, more preferably 0.7 or less. Therefore, the appropriate lamination thickness depends on the size of the inert particles (A) to be used and cannot be unconditionally determined, but is usually 5 to 1000 nm, preferably 10 to 500 n.
In the case of m, the surface morphology in the range of the present invention is easily obtained, so that it is particularly effective.

A feature of the production method of the present invention is that a film is biaxially stretched after a very thin layer containing inert particles (A) is provided using a high-concentration particle polymer prepared by a special method.

[Function] The present invention provides a running surface having a surface morphology that cannot be obtained by a conventional method, by laminating a thermoplastic resin containing inert particles (A) under a special condition with a high-concentration master polymer and then performing biaxial stretching. It is presumed that the effect of the present invention was obtained as a result of the remarkable improvement in the surface projection characteristics because the film had the following characteristics.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Average particle diameter of particles A thermoplastic low-temperature incineration method is applied to the thermoplastic resin from the running surface side of the ferromagnetic metal thin film support (for example, PR-
503) to expose the particles. The treatment condition is selected so that the film and the thermoplastic resin are ashed but the particles are not damaged. This is observed with a scanning electron microscope (SEM), and the image of the particles (shading of light produced by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrument).
The following numerical processing is performed on 10,000 or more pieces, and the number average diameter D obtained thereby is defined as the average particle diameter.

 D = ΣDi / N Here, Di is the equivalent circle diameter of the particle, and N is the number.

If there is a film containing inert particles on the running surface of the support for ferromagnetic metal thin film, remove this film in advance and perform incineration, or use the SEM image before incineration and the SEM image after incineration. The particle size distribution is determined and compared, and the effects of inert particles in the coating are eliminated by numerical processing. This is not necessary for inert particles of the same size.

(2) Content of Particles A solvent in which the thermoplastic resin is dissolved but inactive particles are not dissolved is selected, the particles are centrifuged from the thermoplastic resin, and the particle content is defined as a ratio (% by weight) to the total weight of the particles. . In some cases, the combined use of infrared spectroscopy is also effective.

If there is a coating containing an insoluble substance on the surface of the support for a ferromagnetic metal thin film, the coating is removed beforehand and then dissolved.

(3) Glass transition point Tg, cold crystallization temperature Tcc, crystallization parameter ΔTcg, melting point Measured using a Perkin Elmer DSC (differential scanning calorimeter) type II. The measurement conditions for DSC are as follows.
That is, 10 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected.
The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. The temperature was further raised, and the melting peak temperature was taken as the melting point. The difference between Tcc and Tg (Tcc−Tg) is defined as a crystallization parameter ΔTcg.

(4) Surface molecular orientation (refractive index) The running surface of the support for a ferromagnetic metal thin film is measured. If there is a film on this surface, the film is removed before measurement.

The measurement was performed using an Abbe refractometer with sodium D line (589 nm) as a light source. The measurement was performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution. The biaxial orientation of the polymer is determined by the refractive indices N1, N2, N3 in the longitudinal, width, and thickness directions.
When the absolute value of (N1-N2) is 0.07 or less, and N3 /
One criterion may be that [(N1 + N2) / 2] is 0.95 or less. Further, the refractive index may be measured using a laser refractometer. Further, when measurement is difficult by this method, a total reflection laser Raman method can be used. The total reflection Raman of the laser was measured by Ramanor manufactured by Jobin-Yvon.
The U-1000 Raman system measures the total reflection Raman spectrum, for example in the case of PET, the polarization measurement ratio of the band intensity ratio of 1615 cm ^-1 (skeletal vibration of benzene ring) and 1730 cm ^-1 (stretching vibration of carbonyl group) (YY / XX ratio, etc., where YY: Raman light detection parallel to Y with laser polarization direction Y, XX: Raman light detection parallel to X with laser polarization direction X) Correspondence with molecular orientation can be used. The biaxial orientation of the polymer can be determined by converting the parameters obtained from the Raman measurement into the refractive index in the longitudinal direction and the width direction, and from the absolute value, difference, and the like. The measurement conditions in this case are as follows.

Light source Argon ion laser (5145A) Sample setting The film surface is pressed against a total reflection prism, and the angle of incidence of the laser on the prism (the angle with the film thickness direction) is
60 mm.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C123
0) (supply 1600V) Measurement conditions SLIT 1000μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (5) Average height of surface projections Measure the surface. If there is a film on this surface, the film is removed before measurement.

When scanning with a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, manufactured by Elionix Inc.] with the height of the flat surface of the film surface set to 0. Is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct a film surface projection image on the image processing apparatus. Next, a circle-equivalent diameter is determined from the area of each projection obtained by binarizing the projection portion on the surface projection image, and this is defined as the average diameter of the projection. The highest value among the binarized individual projections is defined as the height of the projection, and this is determined for each individual projection. This measurement was repeated 500 times at different locations to determine the number of protrusions, and the average value of the heights of all the measured protrusions was defined as the average height. The standard deviation of the height distribution was determined based on the height data of each projection. The magnification of the scanning electron microscope is selected to be a value between 1000 and 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200
The height information obtained by using (2, the use of a high-resolution camera is effective) may be replaced with the value of the SEM and used.

(6) Center line average surface roughness Ra, maximum height Rt The running surface of the support for a ferromagnetic metal thin film is measured. If there is a film on this surface, the film is removed before measurement.

The measurement was carried out using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value of 20 measurements.

・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm The definition of Ra and Rt is, for example, the method of measuring and evaluating surface roughness by Jiro Nara (Comprehensive Technology Center, 1983).

(7) Young's modulus According to the method specified in JIS-Z-1702, use an Instron type tensile tester at 25 ° C and 65%
Measured at RH.

(8) Melt viscosity Using a Koka type flow tester, the melt viscosity was measured at a temperature of 290 ° C. and a shear rate of 200 cm ⁻¹ .

(9) Particle size ratio It is the ratio of the average value of the major axis / the average value of the minor axis in the measurement of the above (1).

 That is, it is obtained by the following equation.

Major axis = ΣD1i / N Minor axis = ΣD2i / N D1i and D2i are the major axis (maximum diameter), minor axis (shortest axis) and N are the total number of the individual particles, respectively.

(10) Relative standard deviation of particle diameter Standard deviation calculated from individual particle diameter Di, average diameter D, and total number N of particles measured by the method of (1) above. Was divided by the average diameter D (σ / D).

(11) Surface layer concentration ratio Measure the running surface side of the ferromagnetic metal thin film support. Using a secondary ion mass spectrometer (SIMS), the analysis is performed in the thickness direction with the concentration ratio of the highest concentration element among the elements originating from the particles in the film and the carbon element of the polyester as the particle concentration. The ratio A / B between the particle concentration A at the outermost surface particle concentration (point at depth 0) measured by SIMS and the maximum concentration B obtained by further analyzing in the depth direction, A / B, was defined as the surface concentration ratio. When there is a film on the surface to be measured, the film is removed beforehand, or the measurement is performed. When the interface between the film and the film can be detected by SIMS, the interface is set to the above-mentioned zero depth point. The measuring device and conditions are as follows.

Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration current: 12 kV Primary ion current: 200 nA Raster area: 400 μm Range: gate 30% Measurement vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5 kV-3.0 A In the case of particles difficult to measure by SIMS, total reflection infrared spectroscopy, confocal microscopy, etc. This is effective for measuring the depth profile.

(12) Coefficient of friction μk A film obtained by slitting a film into a 1 / 2-inch wide tape is used at 20 ° C and 60% RH using a tape running tester TBT-300 (Yokohama System Laboratory Co., Ltd.). After running in an atmosphere, the initial coefficient of friction was determined by the following equation (the film width was 1/2 inch).

μk = 0.733 log (T2 / T1) Here, T1 is the entrance tension and T2 is the exit tension. The guide diameter is 6mmφ, the guide material is SUS27 (surface viscosity 0.2S),
The winding angle is 180 ° and the running speed is 3.3cm / sec. When μk obtained by this measurement was 0.3 or less, the coefficient of friction was determined to be good, and when it exceeded 0.3, the coefficient of friction was determined to be poor. This μk converts the film to a magnetic recording medium, a capacitor,
It is a critical point that affects the handling characteristics when processing such as packaging.

(13) Handling characteristics The manufactured support for a ferromagnetic metal thin film is slit into a roll of 500 mm width x 5000 m length using a plastic core having an inner diameter of 6 inches so that the running surface is on the inside. The rolls thus formed are slit into 10 rolls, and the number of rolls that have been successfully wound without wrinkles is counted and displayed. Ten
If five or more of the books cannot be wound well, it is determined that the handling characteristics are poor.

(14) Output characteristics By continuous vacuum oblique deposition, Co, N
A ferromagnetic metal thin film (Ni = 20% by weight, film thickness 150 nm) is formed in the presence of a trace amount of oxygen. The oxygen concentration is adjusted so that the oxygen content of the ferromagnetic metal thin film is 5% in terms of the atomic ratio to the metal. Thereafter, the surface of the obtained ferromagnetic metal thin film is coated with stearic acid at a concentration of about 10 mg / m ² and slit into a width of 8 mm to form a magnetic tape. This tape 50m length is S
VTR cassette tape built into ONY high-grade cassette.

Using a Sony home-use VTR (EV-S900) on this tape, using a Shibasoku TV test waveform generator (TG7 / U706)
A 100% chroma signal was recorded, and the chroma S / N was measured from the reproduced signal using a color video noise meter (925D / 1) manufactured by Shibasoku.

[Examples] The present invention will be described based on examples.

Examples 1 to 4 and Comparative Examples 1 and 2 Water sols (particle concentration: 50%) containing silica particles derived from colloidal silica having different average particle diameters were respectively converted into polyethylene terephthalate using a vented twin-screw extruder. A predetermined amount was kneaded to prepare a 30 w% high concentration master pellet. The master pellet and polyethylene terephthalate pellet substantially containing no inert particles were mixed at a predetermined ratio. 180 ° C of these mixed pellets
After drying under reduced pressure for 3 hours (Torr), the mixture was supplied to the extruder 1. On the other hand, the polyethylene terephthalate pellets C containing substantially no inert particles are similarly dried, fed to the extruder 2 and melted at 300 ° C., respectively, and then melted using a rectangular feed block. (A /
C), extruded into a sheet shape from a die slit, wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to produce a two-layer unstretched film. At this time, the discharge amount of the extruder was adjusted to change the ratio t / D between the average particle diameter D of the inert particles and the thickness t on one side of the A layer. This unstretched film is heated at 80 ° C in the longitudinal direction for 3.
Stretched three times. This stretching was performed in three stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was heated and dried at 100 ° C. using a stenter and stretched 3.4 times in the width direction at a stretching speed of 2000% / min. This film under fixed length, 2
Heat treatment was performed at 00 ° C. for 5 seconds to obtain a biaxially oriented polyester film having a total thickness of 10 μm. The surface A (running surface) of these films had many surface protrusions based on the silica particles kneaded into the layer A, and no protrusions existed on the opposite surface (magnetic surface). The parameters of the present invention for these films are the first
As shown in the table, the handling characteristics and the output characteristics were extremely good as shown in Table 1 when within the parameter range of the present invention, but otherwise satisfied both the handling characteristics and the output characteristics. No film was obtained.

Comparative Example 3 Polyethylene terephthalate containing 2% by weight of silica particles having an average particle size of 150 nm was dried in the same manner as in Example 1, then melted at 300 ° C. and extruded in a single layer, and the surface temperature was measured using an electrostatic application casting method. The film was wound around a casting drum at 30 ° C., cooled and solidified to form a single-layer unstretched film. This unstretched film was stretched and heat-treated in the same manner as in Example 1 to obtain a biaxially oriented polyester film having a thickness of 10 μm. On both surfaces of this film, there were many surface protrusions based on silica particles contained therein. As shown in Table 1, the characteristics of this film were out of the range of the present invention, and the handling characteristics were good, but the output characteristics were poor.

Example 5 An aqueous dispersion coating solution having the following formulation was applied to the outer surface of layer A of a uniaxially stretched film uniaxially stretched in the longitudinal direction by a Mayer bar coater for 8 m.
After l / m ² application, the film was laterally stretched using a stenter. Otherwise in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 10 μm was obtained. On the A-side (running surface) of these films, there are a large number of surface projections based on silica particles kneaded into the A-layer, and on the surface thereof, it is easy to have an earthworm structure containing the silica particles contained in the coating liquid. A lubricious film was formed.
Also, no protrusion was present on the opposite surface (magnetic surface). The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Formulation) Water-soluble polyester 0.3% by weight Methylcellulose 0.2% by weight Colloidal silica (particle size 30nm) 0.03% by weight Example 6 A water-dispersed coating of the following formulation is applied to the outer surface of layer C of a uniaxially stretched film stretched uniaxially in the longitudinal direction. 6m liquid with Meyer bar coater
After l / m ² application, the film was laterally stretched using a stenter. Otherwise in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 10 μm was obtained. The surface A (running surface) of these films has many surface protrusions based on the silica particles kneaded into the layer A, and the opposite surface (magnetic surface) is in contact with the acrylic particles added to the coating solution and the protrusions. Had formed. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Formulation) Acrylic acid emulsion 0.2% by weight Methylcellulose 0.05% by weight Example 7 A water-dispersed coating solution of the following formulation was applied to the outer surface of layer C of a uniaxially stretched film stretched uniaxially in the longitudinal direction by a Meyer bar coater for 6 m.
After l / m ² application, the film was laterally stretched using a stenter. Otherwise in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 10 μm was obtained. The surface A (running surface) of these films had many surface protrusions based on the silica particles kneaded into the layer A, and the opposite surface (magnetic surface) had a film having an earthworm structure formed thereon. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Formulation) Methylcellulose 0.15% by weight Example 8 A water-dispersed coating solution of the following formulation was applied to the outer surface of layer C of a uniaxially stretched film stretched uniaxially in the longitudinal direction by a Mayer bar coater for 6 m.
After l / m ² application, the film was laterally stretched using a stenter. Otherwise in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 10 μm was obtained. The surface A (running surface) of these films has many surface protrusions based on the silica particles kneaded into the layer A, and the opposite surface (magnetic surface) has an earthworm structure containing the silica particles contained in the coating liquid. Was formed. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Formulation) Water-soluble polyester 0.3% by weight Methylcellulose 0.1% by weight Colloidal silica (particle size: 20 nm) 0.03% by weight Example 9 In Example 1, the average particle diameter was replaced with polyethylene terephthalate C containing substantially no inert particles. Ten
A biaxially oriented polyester film having a thickness of 10 μm was obtained in the same manner as in Example 1, except that polyethylene terephthalate B containing 0.05% by weight of 0 nm silica particles (B) was used.
On the surface A (running surface) of these films, there are a large number of surface projections based on silica particles kneaded into the layer A, and on the opposite surface (magnetic surface), projections based on silica particles contained in the layer B are formed. 20,000 pieces / mm ^{2 were} formed. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

Example 10 An aqueous dispersion coating solution having the following formulation was applied to the outer surface of layer B of a uniaxially stretched film stretched uniaxially in the longitudinal direction by a Mayer bar coater for 6 m.
After applying l / m ² , a biaxially oriented polyester film having a thickness of 10 μm was obtained in the same manner as in Example 9 except that the film was laterally stretched using a stenter. On the surface A (running surface) of these films, there are a large number of surface projections based on silica particles kneaded into the layer A, and on the opposite surface (magnetic surface), projections based on silica particles contained in the layer B are formed. 20,000 particles / mm ² were formed, and a film having an earthworm structure was formed thereon. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Formulation) Methylcellulose 0.15% by weight Example 11 A water-dispersed coating solution having the following formulation was applied to the outer surface of layer B of a uniaxially stretched film stretched uniaxially in the longitudinal direction by a Mayer bar coater for 6 m.
After applying l / m ² , a biaxially oriented polyester film having a thickness of 10 μm was obtained in the same manner as in Example 9 except that the film was laterally stretched using a stenter. On the surface A (running surface) of these films, there are a large number of surface projections based on silica particles kneaded into the layer A, and on the opposite surface (magnetic surface), projections based on silica particles contained in the layer B are formed. 20,000 particles / mm ² were formed, and a film having an earthworm structure containing silica particles contained in the coating liquid was formed thereon. The characteristics of this film are as shown in Table 1, and within the scope of the present invention, the film had high handling characteristics and output characteristics.

(Prescription) Water-soluble polyester 0.3% by weight Methylcellulose 0.1% by weight Colloidal silica (particle size 20nm) 0.03% by weight [Effects of the Invention] In the present invention, a film having a special surface morphology which has not been obtained conventionally can be obtained by devising a manufacturing method. Therefore, handling when this surface is used as a running surface for a ferromagnetic metal thin film type magnetic recording medium is used. A film that can achieve both characteristics and output characteristics at an extremely high level has been obtained, and is useful for improving the image quality of a ferromagnetic metal thin film type video tape in the future. Also,
Because of this unique surface, the film is excellent in wear resistance and can withstand severe use, and can cope with an increase in film processing speed in each application. The use of the film of the present invention is not particularly limited, but in addition to the magnetic recording medium described above, it is used for packaging utilizing the handling characteristics relating to the coefficient of friction and the good transparency caused by the special surface, and furthermore, due to the special surface. It can be applied to a wide range of elements such as capacitors for electric insulation. In the film of the present invention, the surface having a surface morphology within the scope of the present invention is a running surface (a surface on which a ferromagnetic metal thin film is not formed as a support for a ferromagnetic metal thin film, and printing and other coating materials are applied in other applications). It is desirable to use it as a surface that is not subjected to such processing.

Continuation of the front page (56) References JP-A-62-248131 (JP, A) JP-A-63-108038 (JP, A) JP-A-62-241123 (JP, A) JP-A-62-180520 (JP, A) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 5/00

Claims (4)

(57) [Claims] 1. A laminated film having a layer made of a biaxially oriented film mainly composed of a thermoplastic resin and inert particles (A) contained in the resin on a surface not in contact with the ferromagnetic metal thin film. On the surface that is not in contact with the ferromagnetic metal thin film, surface protrusions having nuclei of inert particles (A) contained in the resin are formed, and the average height of the surface protrusions is A) The average particle diameter of the biaxially oriented film layer containing the inert particles (A) is 1/4 or more of the average particle diameter of the inert particles (A). Ratio (t /
A support for a ferromagnetic metal thin film, wherein D) is 2 or less. 2. A ferromagnetic metal thin film support according to claim 1, wherein a slippery coating is formed on a surface of the support not in contact with the ferromagnetic metal thin film. 3. The method according to claim 1, wherein no protrusion having nuclei of inert particles contained in the thermoplastic resin substantially exists on the surface in contact with the ferromagnetic metal thin film. Support for ferromagnetic metal thin film. 4. A projection having nuclei of inert particles (B) having a particle diameter of 100 nm or less dispersed in a thermoplastic resin formed on a surface in contact with the ferromagnetic metal thin film, and having a projection density of 20,000. 3. The support for a ferromagnetic metal thin film according to claim 1, wherein the support is at least one piece / mm ² .