JPH07296374A - Magnetic tape - Google Patents

Abstract

PURPOSE:To prepere a magnetic tape having excellent output characteristics by providing a magnetic layer on one side and a back coat layer on the other side and specifying the surface roughness on the magnetic surface and the back coat surface as well as the strength of the tape in the longitudinal and lateral directions. CONSTITUTION:The magnetic tape is made of a biaxially oriented polymer film principally comprising polyethylene-2,6-naphthalene dicarboxylate having a magnetic layer and a back coat layer, respectively, on the opposite sides thereof. The surface roughness is set at 5nm or less for the magnetic layer and in the range of 15-60nm for the back coat layer, Young's modulus is set at 500kg/mm<2> or above and 800kg/mm<2> or above, respectively, in the longitudinal and lateral direction of the tape having thickness and width being set, respectively, at 10mum or less and 8mm or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic tape.

[0002]

2. Description of the Related Art As a magnetic tape, there is known a magnetic recording medium in which the surface waviness of the surface on which a magnetic layer is formed is defined (for example, Japanese Patent Laid-Open No. 3-176807). As a film for a magnetic recording medium, a film is known in which the relationship between the laminated thickness and the particle diameter of contained particles is defined (for example, Japanese Patent Laid-Open No. 2-7
7431).

However, in the above-mentioned conventional magnetic recording media, particularly films for magnetic recording media, the relationship between the laminated thickness and the particle size of the contained particles is defined to make the height of protrusions on the film uniform, and electromagnetic conversion characteristics as a magnetic recording medium are obtained. Although the wear resistance of the base film surface is improved, there is a demand for smoothing of the surface roughness of the magnetic surface and the surface roughness of the back surface when a higher density magnetic recording medium is used. Higher strength has been required for the strength in the longitudinal direction and the strength in the lateral direction after the conversion, and the problem of insufficient output characteristics has arisen in this application. An object of the present invention is to solve such problems and to provide a magnetic tape having excellent output characteristics.

[0004]

The magnetic tape of the present invention for this purpose has a biaxially oriented film formed on a single side of a polymer containing polyethylene-2,6-naphthalenedicarboxylate as a main component (hereinafter referred to as PEN). A magnetic layer on
A magnetic tape having a back coat layer on the opposite side,
The surface roughness of the magnetic surface is 5 nm or less, the surface roughness of the back coat surface is 15 to 60 nm, the Young's modulus in the tape longitudinal direction is 500 kg / mm ² or more, and the Young's modulus in the lateral direction is 800 k.
g / mm ² or more, the tape thickness is 10 μm or less, and the tape width is 8 mm or less.

The biaxially oriented film used for the magnetic tape of the present invention is not particularly limited, but preferably has at least a two-layer structure of A layer / B layer from the viewpoint of output characteristics. A
The layer thickness is not particularly limited, but is 0.0 from the viewpoint of output characteristics.
It is 3 to 1.0 μm, preferably 0.05 to 0.5 μm, and more preferably 0.05 to 0.3 μm.

The polymer constituting the biaxially oriented film of the magnetic tape of the present invention is preferably PEN from the viewpoint of output characteristics.
In the case of a laminated structure, the main component of at least one layer is PEN
The other layers are not particularly limited, but polyester is preferably exemplified. The polyester is not particularly limited, but a polymer containing polyethylene terephthalate as a main component (hereinafter referred to as PET) or PEN is preferable.

A of the laminated constitution which constitutes the film of the present invention
Layer / B layer are PEN / PET and PEN / PE, respectively
Either N or PET / PEN can be used.

Two or more kinds of polymers may be mixed, or a copolymerized polymer may be used, as long as the object of the present invention is not impaired. Further, other polymers may be blended within a range that does not impair the object of the present invention, and additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers are added to such an extent that they are usually added. May be.

The layer A of the biaxially oriented film used for the magnetic tape of the present invention is not particularly limited, but from the viewpoint of output characteristics, it is 0.02 to 1.0 μm, preferably 0.05 to 0.
Particles having a particle size of 5 μm, more preferably 0.1 to 0.3 μm, are contained in an amount of 0.01 to 3.0% by weight, preferably 0.02.
It is preferable that the content is up to 2.0% by weight.

The particles contained in the biaxially oriented film used in the magnetic tape of the present invention are not particularly limited, but organic particles, particularly crosslinked organic particles, and particularly divinylbenzene particles are preferable from the viewpoint of output characteristics. The divinylbenzene particles are particles mainly composed of divinylbenzene as a crosslinking component. Among them, divinylbenzene is preferably at least 51%, preferably at least 60%, more preferably at least 75% of the particle component. Other components are not particularly limited, and examples thereof include non-crosslinking components such as ethylvinylbenzene and diethylbenzene. Further, silcon particles are also preferably exemplified. The silicone particles are preferably those containing a three-dimensionally cross-linked organopolysiloxane (CH ₃ Si O _3/2 ) as a main component. In addition, the crystal form is α type, γ type, δ type,
Aggregate particles of θ-type or η-type alumina, zirconia, silica, titanium or the like, or inorganic particles of calcium carbonate, colloidal silica, titanium or the like can also be used by particle dispersion in a suitable polymer. A plurality of these particles may be used in combination.

The relationship between the thickness t of the A layer and the particle diameter d of the particles contained in the A layer is not particularly limited, but 0.2 ≦ t / d ≦ 10, preferably 0.5 ≦ t / d ≦ 5, and further preferably. 0.5
When ≦ t / d ≦ 3, the output characteristics are particularly good.

Biaxially oriented film layers other than A layer, ie B
Particles may be contained in the polymer constituting the layer or the like. In this case, the particle size is 0.05 to 1.0 μm, preferably 0.1 to 0.5 μm, and the content is 0.05 to 1.0 wt% calcium carbonate, alumina, silica, titanium, organic particles, It is preferable to contain particles selected from carbon black and the like.

The biaxially oriented film used in the magnetic tape of the present invention is a film in which the above composition is biaxially oriented. A uniaxial or non-oriented film is not preferable because it lacks strength in the width direction.

The biaxially oriented film used for the magnetic tape of the present invention has a non-orientated or uniaxial orientation of polymer molecules in a part in the thickness direction of the film, for example, near the surface layer. The output characteristics are further improved when the molecular orientations of all parts in the direction are biaxial orientations. In particular, when the molecular orientation measured by an Abbe refractometer, a refractometer using a laser, a total reflection laser Raman method or the like is biaxial orientation on both the front surface and the back surface, the output characteristics are further improved.

Although the Young's modulus in the width direction of the biaxially oriented film used for the magnetic tape of the present invention is not particularly limited, it is 600 kg / mm ² or more, preferably 8 from the viewpoint of output characteristics.
It is at least 00 kg / mm ² .

The magnetic tape of the present invention has a magnetic layer on one side of the biaxially oriented film and a back coat layer on the opposite side.

As the magnetic layer, either a metal coating type magnetic layer or a metal thin film type magnetic layer may be provided on at least one surface of the above biaxially oriented film. The magnetic powder used in the metal-coated magnetic layer is not particularly limited, but is a ferromagnetic powder, among which Fe, Co, Fe-Co, Fe-Co-Ni, and C.
Metals or alloys such as o-Ni, and Al, Cr, S
An alloy with i or the like is preferably used.

The magnetic powder can be made into a magnetic paint by using various binders, but in general, thermosetting resin type binders and radiation curing type binders are preferable, and other additives such as dispersants, lubricants and antistatic agents are used. You may use according to a conventional method. For example, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate can be used.

The thickness of the metal-coated magnetic layer is not particularly limited, but is preferably 0.1 to 5 μm.

The type of the metal thin film type magnetic layer is not particularly limited, but a ferromagnetic thin film of iron, cobalt, nickel, chromium or an alloy thereof, or a metal oxide thin film layer obtained by vapor deposition of a metal in an oxygen atmosphere, etc. Is preferably used.

The thickness of the metal thin film type magnetic layer is not particularly limited, but is preferably 0.01 to 1 μm.

As the back coat layer, ordinary carbon black, other non-magnetic inorganic powder, zinc oxide, silicon dioxide, graphite, iron oxide, aluminum silicate,
Talc, titanium oxide, kaolin, tungsten disulfide,
It is formed by applying a composition comprising calcium carbonate, tin oxide, magnesium oxide and the like and a binder (resin). The carbon black used is usually 0.5 μm or less.

Acrylic acid and methacrylic acid ester used as a dispersant are selected from those known per se and used, but particularly butyl acrylate, ethyl acrylate, methyl acrylate, butyl methacrylate, ethyl methacrylate. Those having an alkyl group having 1 to 10 carbon atoms in the ester portion such as methyl methacrylate are suitable. The copolymer is 70-98% acrylic acid ester, and /
Alternatively, it is composed of methacrylic acid ester and 2 to 30% of acrylic acid and / or methacrylic acid (both in molar ratio, the same applies hereinafter). As the mixer, known means such as a roll mill, a ball mill, a sand mill, an attritor, a kneader, a homogenizer and an ultrasonic disperser can be used. The back layer composition thus prepared is applied to the back surface of the non-magnetic support having a magnetic layer by a known method.

As the binder for the back layer, a binder conventionally known in the art, for example, a thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof is used.

The back layer of the present invention is selected so that the total thickness of the magnetic tape (magnetic layer + support + back layer) is made as thin as possible in order to increase the recording density per unit volume. The thickness of such a back layer is preferably 0.3-2 μm.
m, particularly preferably 0.5 to 1 μm.

The surface roughness of the magnetic surface of the magnetic tape of the present invention is 5 nm or less, preferably 3 nm or less from the viewpoint of output characteristics.

The surface roughness of the back coat surface of the magnetic tape of the present invention is 15 to 60 nm, preferably 15 to 50 nm or less from the viewpoint of output characteristics.

The Young's modulus in the longitudinal direction of the magnetic tape of the present invention is 500 kg / mm ² or more, preferably 600 kg / mm ² or more from the viewpoint of output characteristics.

The Young's modulus in the transverse direction of the magnetic tape of the present invention is 800 kg / mm ² or more, preferably 1000 kg / mm ² or more, and more preferably 1200 from the viewpoint of output characteristics.
It is at least kg / mm ² .

The total thickness of the magnetic tape of the present invention is 10 μm or less, preferably 8 μm or less, from the viewpoint of recording and reproducing time as a magnetic recording medium.

The magnetic tape of the present invention is preferably used as a magnetic tape for digital recording. Further, it is particularly preferably used as a magnetic tape for recording HDTV (high definition television, NHK high vision, etc.) which requires high output.

Next, a preferable method for producing the magnetic tape of the present invention will be shown and described below, but the present invention is not limited thereto.

First, as a preferred method for producing a biaxially oriented film constituting a magnetic tape, a method of incorporating particles into PEN is to disperse ethylene glycol, which is a diol component, in the form of slurry, and this ethylene glycol is predetermined. It is preferable to polymerize with the dicarboxylic acid component of.
Further, a method of directly mixing an aqueous slurry of particles with a predetermined PEN pellet and kneading the mixture into PEN using a vent type twin-screw kneading extruder is effective for further improving the effect of the present invention.

As a method for controlling the content of particles, a high-concentration master is prepared by the above-mentioned method and is diluted with a polymer which does not substantially contain particles at the time of film formation to control the content of particles. Is effective.

Next, pellets containing a predetermined amount of particles are dried, if necessary, and then fed to a known melt laminating extruder, extruded in a sheet form from a slit die, and cast on a casting roll. It is cooled and solidified with to make an unstretched film. That is, the polyester in a molten state is laminated using a plurality of extruders, a plurality of manifolds or a merging block. In this case, the method of installing the static mixer and the gear pump in the polymer channel containing the particles is effective for further improving the effect of the present invention.

Next, this unstretched film is biaxially stretched and biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, by using a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more stages, and the longitudinal stretching temperature is 80 to 180 ° C, preferably 85 to 150 ° C. Total longitudinal stretching ratio 3.0-6.0 times, longitudinal stretching speed 5,000-50,000
It is preferably carried out in the range of% / min. As a stretching method in the width direction, a method using a tenter is preferable, and a stretching temperature of 8
0 to 180 ° C., preferably 90 to 150 ° C., the transverse stretching ratio is 4.0 to 7.0 times, preferably 4.5 to 6.5 times larger than the longitudinal stretching ratio, and the transverse stretching speed is 1,000 to 20,000%.
It is preferably carried out in the range of / minute. Further, if necessary, longitudinal re-stretching and lateral re-stretching are performed.

Next, the biaxially oriented film of the stretched magnetic tape is heat treated. The heat treatment temperature in this case is 170 to 22.
It is preferable that the temperature is 0 ° C., particularly 170 to 210 ° C. and the time is 0.5 to 60 seconds.

Next, a back coat layer is provided on the biaxially oriented film, but the coating order with the magnetic layer does not matter.

Further, a magnetic layer is provided on the above film. The magnetic tape of the present invention can be obtained by either coating or vapor deposition as the magnetic layer.

The method of applying the magnetic layer can be carried out by a known method. In the drying process after coating, the temperature is 90 to 1
The temperature is preferably 20 ° C.

The calendering step is preferably carried out in a temperature range of 25 to 90 ° C., particularly 40 to 70 ° C., using polyamide or polyester for the elastic roll. Further, after curing the magnetic layer of this film, the original fabric (wide width) is slit to obtain the magnetic tape of the present invention.

In the case of the vapor deposition type, the method of vapor depositing the magnetic layer can be carried out by a known method, for example, iron,
A thin metal film of cobalt, nickel or its alloy is directly deposited on the base film by vacuum deposition, ion plating, sputtering, or aluminum, titanium,
It is preferably formed through a base thin film of chromium or the like.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows.

(1) Average Particle Size of Particles The cross section of the film was measured by using a transmission electron microscope (TEM).
Observe at a magnification of 0,000 times or more. Section thickness of TEM is about 1
It is set to 00 nm, and the location is changed to measure 100 fields or more.
The average diameter of the particles is calculated from the weight average diameter (equivalent circle diameter).

(2) Content of Particles A solvent that dissolves the polymer but not the particles is selected, the particles are centrifuged from the polymer, and the ratio (% by weight) to the total weight of the particles is taken as the particle content. In some cases, the combined use of infrared spectroscopy is also effective.

(3) Lamination Thickness of Laminated Film Using a secondary ion mass spectrometer (SIMS), the element derived from the highest concentration of the particles in the film in the depth range of 3000 nm from the surface layer and the polyester The concentration ratio (M ⁺ / C ⁺ ) of the carbon element is used as the particle concentration, and analysis is performed in the thickness direction from the surface layer to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again.
Based on this concentration distribution curve, the surface particle concentration is 1 / maximum
A depth of 2 (the depth is deeper than the maximum value) was obtained and used as the laminated thickness. The conditions are as follows.

Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 kV Primary ion current: 200 nA Raster region: 400 μm □ Analysis region: 30% gate Measurement degree of vacuum: 6.0 × 10 ^-9 Torr E-GUN: 0.5 kV-3.0 A In addition, the particles contained most in the range of the surface layer to the depth of 3000 nm are organic polymer particles. In this case, since it is difficult to measure with SIMS, XPS while etching from the surface
(X-ray photoelectron spectroscopy), IR (infrared spectroscopy), etc. may be used to measure the depth profile similar to the above to obtain the layer thickness, or the cross-sectional observation with an electron microscope or the like to determine the change in particle concentration It is also possible to recognize the interface from the difference in contrast due to the difference in polymer and obtain the laminated thickness. Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(4) Orientation of film surface It was measured using an Abbe refractometer with sodium D line (589 nm) as a light source. Methylene iodide was used as the mount solution, and measurement was performed at 25 ° C. and 65% RH. The biaxial orientation of the film is such that when the refractive indices in the longitudinal, width and thickness directions are N1, N2 and N3, the absolute value of (N1-N2) is 0.07 or less and N3 / [(N1 + N2 ) / 2] is less than 0.95 as one criterion. Further, the refractive index may be measured using a laser type refractometer. Further, when the measurement is difficult by this method, the total reflection laser Raman method can be used.

(5) Young's modulus According to the method specified in JIS-Z-1702,
25 using an Instron type tensile tester
It was measured at 65 ° C. and 65% RH.

(6) Surface roughness The surface roughness was measured using a surface roughness meter according to JIS B0601. The conditions are as follows, and the average value of 20 measurements was taken as the value.

・ Tactile tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm (7) Output characteristics Using a Hi8 system video tape recorder, a test tape of 7 MHz ± The C / N of 1 MHz was measured. Output characteristics equivalent to those of Hi8ME video tapes on the market (with a difference of +0 dB or less) Output characteristics: Poor, output with a difference of +3 dB or less Output characteristics: Good, Output characteristics with a difference of +3 dB or more: I was kind

[0052]

The present invention will be described in more detail based on the following examples.

Example 1 (Table 1) An aqueous slurry of polydivinylbenzene particles having a particle composition of 81% divinylbenzene was directly treated with polyethylene-2,6.
-Mixed with naphthalene dicarboxylate pellets and kneaded using a vent type twin-screw kneading extruder to obtain PEN particle pellets.

This particle pellet and a PEN polymer pellet containing substantially no particles were mixed in an appropriate amount and dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then polymer A: 0.45.
A polymer containing 0.5% by weight of divinylbenzene particles having a diameter of μm,
Polymer B: 0.2 μm diameter polydivinylbenzene particles 0.
The polymer containing 2% by weight was supplied to the extruder 1 and the extruder 2, respectively, and melted at 290 ° C and 295 ° C. After high-precision filtration of these polymers, two layers were laminated at the rectangular junction (A
/ B).

This was wound around a casting drum having a surface temperature of 25 ° C. by an electrostatically applied cast method and cooled and solidified to prepare an unstretched film. At this time, the ratio of the die slit gap / the thickness of the biaxially oriented film of the unstretched magnetic tape was set to 10. Further, the total thickness and the thickness of the A layer were adjusted by adjusting the discharge amount of each extruder.

This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 135 ° C. This stretching is done with two pairs of rolls.
It was carried out in four stages with the peripheral speed difference of Le. This uniaxially stretched film was stretched 6.0 times in the width direction at 130 ° C. using a tenter. Further, it was stretched 1.4 times in the width direction at 160 ° C. using a tenter. This film was heat-treated at 210 ° C. for 3 seconds under a fixed length to give a total thickness of 6.3 μm and an A layer thickness of 0.4.
A biaxially oriented film of μm was obtained.

Next, a back coat layer is applied to this biaxially oriented film.

Carbon black (average particle size 0.05 μ
m) 50 parts and CaCO ₃ (average particle size 0.08 μm) 50
Butyl acrylate-acrylic acid type oligomer (molar ratio 83:17, average molecular weight 1500, C
0.5 parts by weight of OOH group (500) and 500 parts of MEK solution were added, and the mixture was uniformly stirred.
_Three powders were coated with the oligomer. After that, it was transferred to a ball mill disperser and nitrosesulose 30 parts polyurethane 20 parts polyester 5 parts binder was added and dispersed for 24 hours MEK solution 100 parts isocyanate 30 parts (Nippon Polyurethane Coronate L) was added as a coating liquid, which was applied to the back side. 0.8 ~ after coating and drying
A 1.2 μ thick back layer was formed.

Further, a magnetic layer was applied to this film.

The magnetic paint is applied to the film using a gravure roll. The magnetic paint was prepared as follows.

Fe 100 parts Average particle size Length: 0.3 μm Needle ratio: 10/1 Coercive force: 2000 Oe Polyurethane resin 15 parts Vinyl chloride / vinyl acetate copolymer 5 parts Nitrocellulose resin 5 parts Aluminum oxide powder (average particle size: 0.3 μm) 3 parts ・ Carbon black 1 part ・ Lecithin 2 parts ・ Methyl ethyl ketone 100 parts ・ Methyl isobutyl ketone 100 parts ・ Toluene 100 parts ・ Stearic acid 2 parts The above composition was ball milled for 48 hours. After mixing and dispersing, a kneaded product obtained by adding 6 parts of a curing agent is filtered with a filter to prepare a magnetic coating liquid, coated on the above film, magnetically oriented, dried at 110 ° C., and further subjected to a small test. Calendar device (steel roll / nylon roll, 5 steps)
Then, after calendering at 70 ° C. and linear pressure of 200 kg / cm, curing was carried out at 70 ° C. for 48 hours to obtain a metal-coated magnetic recording medium.

The characteristics of this magnetic tape are as shown in Table 1, and the output characteristics were good.

Example 2 (Table 1) In the same manner as in Example 1, a backcoat layer was applied to the obtained biaxially oriented film.

Further, a magnetic layer was vapor-deposited on this film.

On one surface of the film, a cobalt-nickel alloy (Ni 20% by weight) was obliquely vapor-deposited by a high frequency sputtering method in the presence of a slight amount of oxygen in a vacuum vapor deposition machine to form a ferromagnetic thin film layer having a thickness of 0.2 μm. Subsequently, a slit metal thin film magnetic recording medium having a tape width was obtained. The characteristics of this magnetic tape are as shown in Table 1, and the output characteristics were good.

Examples 3 to 4 and Comparative Examples 1 to 4 (Table 1) In the same manner as in Example 1, magnetic tapes having different kinds of particles, particle sizes, contents, laminated thickness and the like were obtained. As shown in Table 1, the magnetic tapes of the present invention have good output characteristics,
It can be seen that the output characteristics are not good for those not.

[0067]

[Table 1]

[0068]

The magnetic tape of the present invention has a magnetic layer on one side.
Since the back coat layer was provided on the opposite surface, the surface roughness of the magnetic surface and the back coat surface was specified, and the strengths in the longitudinal and transverse directions of the tape were specified, excellent output characteristics could be obtained. Moreover, since the thickness of the magnetic tape is reduced, it is possible to sufficiently withstand long-term recording in the future.

Claims (8)

[Claims] 1. A magnetic tape comprising a biaxially oriented film made of a polymer containing polyethylene-2,6-naphthalenedicarboxylate as a main component and having a magnetic layer on one side and a back coat layer on the other side. The surface roughness of the surface is 5 nm or less, and the surface roughness of the back coat surface is 15 to 60.
nm, the Young's modulus in the tape longitudinal direction is 500 kg / mm ² or more, the Young's modulus in the lateral direction is 800 kg / mm ² or more, the tape thickness is 10 μm or less, and the tape width is 8 mm or less. 2. The magnetic tape according to claim 1, which has at least a two-layer structure having an A layer and a B layer, and has an A layer thickness of 0.03 to 1.0 μm. 3. The magnetic tape according to claim 2, wherein the A layer is made of a polymer containing polyethylene-2,6-naphthalenedicarboxylate as a main component. 4. The magnetic tape according to claim 2, wherein the layer B is made of a polymer containing polyethylene-2,6-naphthalenedicarboxylate as a main component. 5. The magnetic tape according to claim 2, wherein the A layer contains 0.01 to 3.0% by weight of particles having an average particle diameter of 0.02 to 1.0 μm. 6. The average particle diameter d (nm) of the A layer-containing particles and A
The relation with the layer thickness t (nm) of the layer is 0.2 ≦ t / d ≦ 10.
6. The magnetic tape according to claim 5. 7. The magnetic tape according to claim 1, which is used in a digital recording type. 8. The magnetic tape according to claim 1, which is used in an HDTV recording type.