JP2528960B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

The present invention relates to a polyethylene-2,6-naphthalate film for a magnetic recording medium, and more specifically to the production of a high quality magnetic recording medium capable of recording for a long time. And a useful polyethylene-2,6-naphthalate film.

[Prior Art] Magnetic recording tape has recently been extended in recording time (longer time).
In order to increase the recording time, it is necessary to reduce the total thickness of the magnetic recording tape and store it in the supply reel longer. However, in order to reduce the total thickness of the tape, it is necessary to reduce the thickness of the base film. Therefore, the stiffness of the tape actually decreases and the edges of the tape are easily scratched during loading and unloading. In some cases, when a high tensile force was applied momentarily, the tape was deformed and the recording was distorted.

Therefore, a high Young's modulus is required for the film which is the base of the magnetic medium for long-term recording.

In addition, with the recent widespread use of VTRs with built-in cameras, the tape is often exposed to severe temperature conditions such as taking it out of the door or bringing it into the car, and the dimensional stability of the tape does not cause skew distortion. As a result, the demand for dimensional stability of the base film is increasing.

Biaxially oriented polyethylene terephthalate film has been conventionally used as a base film of a magnetic recording tape, and a so-called super tension film having a high Young's modulus in the longitudinal direction is used particularly for long-time recording. In the polyethylene terephthalate film, however, the longitudinal Young's modulus is at most 850 kg / mm ^2, transverse Young's modulus case is at most 450 kg / mm ² is a limit. On the other hand, when the Young's modulus in the longitudinal direction is increased, the Young's modulus in the lateral direction is inevitably lowered, so that the tape is easily damaged at the edge portion during running. On the other hand, if an attempt is made to increase the width (lateral) direction Young's modulus in the production of the film, a sufficient vertical direction Young's modulus is not necessarily obtained in this case as well, and the touch with the magnetic head becomes poor, resulting in output fluctuation. Further, the base film having a high Young's modulus stretched by high-strength stretching has a problem that the strain generated at the time of molding remains and the dimensional stability is low. In addition, the high-magnification stretching process has another problem that the product yield is reduced.

On the other hand, in the field of magnetic recording applications, the demand for higher image quality and higher density recording has increased in recent years, and along with this, the base film is required to have a flat surface and excellent slidability and handleability. It is increasing.

Conventionally, a method of adding inorganic particles such as silicon oxide and calcium carbonate to polyester as a method for improving slipperiness, or a method of precipitating fine particles containing calcium, lithium or phosphorus in the polymerization system during the synthesis of polyester has been adopted. ing. In any of these methods, when a polyester film is formed, projections are formed on the film surface due to fine particles to improve the film's slipperiness.

However, in the method of improving the slipperiness of the film by the projections by the fine particles as described above, the slipperiness is usually improved as the surface of the film is roughened, but due to the roughening, the film after coating the magnetic paint is caused. The surface is rough and the electromagnetic conversion characteristics tend to deteriorate.

The present inventors have solved the above-mentioned problems and succeeded in developing a base film having flatness, slipperiness, and durability that can be applied to high-quality magnetic recording application fields.

[Object of the Invention] The object of the present invention is to combine flatness, slipperiness and durability,
A polyethylene-2,6-naphthalate film, which is useful for the production of high-quality magnetic recording media capable of high-density recording, is provided, and further, (1) it is sufficient for thinning magnetic tapes. It has vertical and horizontal strength, (2) the magnetic recording medium obtained through the processing step has excellent dimensional stability, and (3) the surface is flat, there are no large protrusions, and the friction coefficient is Low biaxially oriented polyethylene with excellent winding properties-2,6-
It is to provide a naphthalate film.

[Structure of the Invention] In the present invention, both Young's modulus (My) in the longitudinal direction and Young's modulus (Ty) in the lateral direction are 650 kg / mm ² or more and the difference | My-Ty
Is less than 200 kg / mm ² and surface roughness Ra is more than 0.003 μm
It is less than 0.010 μm, and the number of protrusions on the surface is 30 /
In the distribution curve showing the relationship between the number of protrusions (y: ke / mm ² ) and the height of protrusions (x: μm) obtained in the region of mm ² or more, the curve of the portion larger than the maximum value of the protrusion distribution curve is log ₁₀ y = -12x
It is a biaxially oriented polyethylene-2,6-naphthalate film for magnetic recording media, which is characterized by intersecting +3.7 and having no protrusion of 0.2 μm or more in this region.

The polyethylene-2,6-naphthalate referred to in the present invention may be any one whose repeating structural unit is substantially composed of ethylene-2,6-naphthalenedicarboxylate units, and polyethylene-2 which is not copolymerized. , 6-
Not only naphthalene dicarboxylate but also copolymers in which 10% or less, preferably 5% or less, of the number of repeating structural units are modified with other components, and mixtures and compositions with other polymers are included. .

That is, polyethylene-2,6-naphthalate is synthesized by combining naphthalene-2,6-dicarboxylic acid or a functional derivative thereof and ethylene glycol or a functional derivative thereof in the presence of a catalyst under appropriate reaction conditions. However, to the polyethylene-2,6-naphthalate according to the present invention, one or more appropriate third component (modifying agent) is added before the completion of the polymerization of the polyethylene-2,6-naphthalate, It may be a copolymerized or mixed polyester. Suitable third components include compounds having divalent ester-forming functional groups, such as oxalic acid,
Adipic acid, phthalic acid, isophthalic acid, terephthalic acid,
Dicarboxylic acids such as naphthalene-2,7-dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid, or lower alkyl esters thereof, oxycarboxylic acids such as P-oxybenzoic acid, P-oxyethoxybenzoic acid, or lower alkyl esters thereof, Or propylene glycol,
Examples include compounds such as dihydric alcohols such as trimethylene glycol. Polyethylene-2,6-naphthalate or a modified polymer thereof is obtained by blocking the terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid or methoxypolyalkylene glycol. Or a compound modified with a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol in an extremely small amount within a range where a substantially cotton-like copolymer is obtained.

Its intrinsic viscosity is preferably in the range of 0.4 to 0.9 as measured by a mixed solution of 60% phenol and 40% 1,1,2,2-tetrachloroethane at 35 ° C.

The polyethylene-2,6-naphthalate film of the present invention has a Young's modulus in both the longitudinal and lateral directions of 650 kg / mm ²
The above is necessary, preferably 680 kg / mm ² or more, more preferably 700 kg / mm ² or more. Young's modulus in the vertical direction is 650 Kg / m
If it is less than m ² , the thin tape for recording and reproducing for a long time stretches in the vertical direction when repeatedly used, and the screen and sound are distorted. If the Young's modulus in the lateral direction is less than 650 kg / mm ² , edge damage will occur due to weak lateral force of the tape when used in the same manner as above, which is not preferable.

The Young's modulus in the vertical direction (My) and the Young's modulus in the horizontal direction (T
y)) | My−Ty | needs to be 200 kg / mm ² or less, preferably 150 Kg / mm ² or less, and more preferably 100 Kg
/ mm ² or less. If | My−Ty | exceeds 200 kg / mm ² , there is a problem in that the tape and the head of the video tape recorder do not fit well and the output is not sufficient when the recorded signal is reproduced, which is not preferable.

The surface roughness of the polyethylene-2,6-naphthalate film of the present invention Ra is less than 0.010μm above 0.003 .mu.m, moreover number of protrusions determined by projecting the number 30 Quai / mm ² or more regions (y: Ke / mm ² ) and the height of the protrusion (x: μm), the curve of the portion larger than the maximum value of the protrusion distribution intersects with log ₁₀ y = −12x + 3.7, preferably log ₁₀ y =
It is necessary that it intersects with −18x + 3.7 and that there is no protrusion of 0.2 μm or more in the same region.

When Ra is less than 0.003 μm, the film surface becomes too flat, and the film winding property is industrially difficult. When Ra is greater than 0.010 μm, log ₁₀ y = − in the above definition. If 12x + 3.7 and the surface roughness distribution curve do not intersect, or if there is a protrusion of 0.2 μm or more in the same area, that is, if a large protrusion is present on the surface of the film, a high-quality video tape with poor electromagnetic conversion characteristics. As such, it will not be usable.

When these films are heat-treated at 70 ° C. for 1 hour under no load, the heat shrinkage in the longitudinal direction is preferably 0.15% or less, more preferably 0.10% or less, and particularly preferably 0.06% or less. . In the tape processing process, the heat shrinkage is generally low, but when the heat shrinkage of the base film is high, the heat shrinkage of the tape is correspondingly high. Then, another new problem arises in that the skew of the tape increases.

Next, the surface formation of the film in the present invention will be described.

The polyethylene-2,6-naphthalate of the present invention has a large number of fine projections on the film surface. According to the invention, a large number of these fine projections are polyethylene-2,6.
-From a large number of substantially inert solid microparticles contained dispersed in naphthalate.

Polyethylene-2 containing a large number of inert solid microparticles,
6-naphthalate is generally used at any time during the reaction for forming polyethylene-2,6-naphthalate, for example, during the transesterification reaction or the polycondensation reaction in the case of the transesterification method or in the direct polymerization method. It can be prepared by adding inert solid fine particles (preferably as a slurry in glycol) to the reaction system during the period. Preferably, the inert solid fine particles are added to the reaction system at the initial stage of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

In the present invention, as the inert solid fine particles, so-called externally added particles exemplified below are preferable. Silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.); Organic matter (silicone, crosslinked polystyrene, etc.) Alumina; Silicates containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.) ; Oxides of Mg, Zn, Zr and Ti: Ca and Ba
Sulfates; Li, Ba and Ca phosphates (including monohydrogen and dihydrogen salts); Li, Na and K benzoates; Ca, Ba, Z
N and Mn terephthalates; Mg, Ca, Ba, Zn, Cd, Pb, Sr, M
Titanate of n, Fe, Co and Ni; Chromate of Ba and Pb; Carbon (eg carbon black, graphite etc.); Glass (eg glass powder, glass beads etc.);
Examples include carbonates of Ca and Mg; fluorspar and ZnS, and may be so-called internally precipitated particles produced and precipitated from a catalyst residue or the like during production of the polymer. Of course, these particles may be mixed (used together).

More preferably, the particle size ratio (major axis / minor axis) of the particles is 1.0 to
It is preferable to use silica, silicone resin particles or crosslinked polystyrene particles having a spherical shape with a relative standard deviation of 1.2 and a relative standard deviation of 0.5 or less as defined by the following formula and having a uniform viscosity distribution.

In the above definition of particle size ratio, the major axis of a particle should be understood to mean the distance having the maximum length of the distance between two points where an arbitrary straight line crossing the particle intersects with the circumference of the particle.

In the present invention, the spherical particles dispersedly contained in polyethylene-2,6-naphthalate have a particle size ratio (major axis / minor axis) of 1.
0 to 1.2, preferably 1.0 to 1.15, more preferably 1.0 to 1.
The shape is 1, and each shape is extremely close to a true sphere.

The spherical particles have an average particle size of 0.005 to 0.6 μm,
Preferably 0.01-0.4 μm, more preferably 0.01-0.3 μm
m. Such granular particles are remarkably different from the particles conventionally known as lubricants which are ultrafine aggregate particles of about 10 nm or which are aggregated to form aggregates (aggregated particles) of about 0.5 μm. The point is characteristic.

If the average particle size of the spherical particles is less than 0.005 μm, sufficient slipperiness of the film cannot be obtained, which is not preferable. On the other hand, if the average particle size exceeds 0.6 μm, the projections on the film surface become high and sufficient electromagnetic conversion characteristics cannot be obtained, which is not preferable.

Here, the major axis, the minor axis, and the area equivalent circle diameter of the spherical particles are, for example, 10,000 to 100
Obtained from an image magnified 30,000 times, the average grain size and the grain size ratio are obtained by the following formulas.

Average particle size = sum of area circle equivalent diameters of measured particles / number of measured particles Particle size ratio = average major axis of particles / average minor axis of the particles Further, it is preferable that these spherical particles have a sharp particle size distribution, The relative standard deviation that indicates the steepness of the distribution is 0.
It is preferably 5 or less, more preferably 0.4 or less, and particularly preferably 0.3 or less.

When a relative standard deviation of 0.5 or less is used, since the particles are spherical and the particle size distribution is extremely steep, the distribution of the projections formed on the surface of the film is extremely uniform and the projection height is high. A polyethylene-2,6-naphthalate film having a uniform smoothness is obtained.

The amount of granular particles added is 0.005 to 3% by weight, preferably 0.05 to 2% by weight, more preferably 0.1 to 3% by weight, based on the polymer.
It is 1.5% by weight.

The spherical silica particles are not limited to the manufacturing method as long as the above-mentioned conditions are satisfied, but those obtained by hydrolyzing an organometallic compound in an alcoholic solution are preferable because a more spherical and uniform distribution can be obtained. . For example, spherical silica particles are produced by hydrolyzing ethyl orthosilicate [Si (OC ₂ H ₅ ) ₄ ] into hydrous silica [Si (OH) ₄ ] monodisperse spheres, which are then dehydrated. Then, it can be produced by three-dimensionally growing a silica bond [≡Si-O-Si≡] (Journal of the Science Society of Japan '81, No. 9, P1503).

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH ≡Si-OH + HO-Si≡ → ≡Si-O-Si≡ + H ₂ O The spherical silicone resin fine particles are represented by the following formula (A ) Having a composition represented by

R in the above (A) is a hydrocarbon group having 1 to 7 carbon atoms, and for example, an alkyl group having 1 to 7 carbon atoms, a phenyl group or a tolyl group is preferable. The alkyl group having 1 to 7 carbon atoms may be linear or branched, and examples thereof include methyl, ethyl, n-propyl, iso-propyl, n-butyl and iso.
-Butyl, tert-butyl, n-pentyl, n-heptyl and the like can be mentioned.

Among these, methyl and phenyl are preferable as R, and methyl is particularly preferable.

X in the above formula (A) is a number of 1 to 1.2. When x is 1 in the above formula (A), the above formula (A) is
Formula (A) -1 RSiO _1.5 (A) -1 [wherein the definition of R is the same as above. ] Can be represented by

The composition of the above formula (A) -1 has the following structural portion in the three-dimensional polymer chain structure of the silicone resin; It is derived from.

When x is 1.2 in the above formula (A), the above formula (A) is represented by the following formula (A) -2 R _1.2 SiO _1.4 (A) -2 [where R is the same as above]. Is. ] It can be understood that the structure is represented by 0.2 mol.

The above formula (A) -2 is the following structural portion in the three-dimensional polymer chain of the silicone resin; Derived from

As will be understood from the above description, the composition of the above formula (A) of the present invention consists essentially of, for example, only the structure of the above formula (A) -1, or the structure of the above formula (A) -1. It can be seen that and the structure of the above formula (A) -2 is a structure that coexists in a state in which they are randomly bonded at an appropriate ratio.

The spherical silicone resin fine particles preferably have a value of x between 1 and 1.1 in the above formula (A).

The silicone resin fine particles have, for example, the following formula RSi (OR ′) ₃ Can be produced by hydrolyzing and condensing a trialkoxysilane represented by or a partial hydrolysis-condensation product thereof in the presence of ammonia or an amine such as methylamine, dimethylamine, ethylenediamine or the like with stirring. According to the above-mentioned method using the above-mentioned starting materials, silicone resin fine particles having a composition represented by the above formula (A) -1 can be produced.

In the above method, for example, the following formula R ₂ Si (OR ′) ₂ [wherein R and R ′ are the same as defined above. ] By using the dialkoxysilane represented by the following together with the above trialkoxysilane and following the above method, the silicone resin fine particles having the composition represented by the above formula (A) -2 can be produced.

The spherical crosslinked polystyrene particles include, for example, a styrene derivative monomer such as a styrene monomer, a methylstyrene monomer, an α-methylstyrene monomer, a dichlorostyrene monomer, and a butadiene conjugated diene monomer,
Of unsaturated nitrile monomers such as acrylonitrile, monomers such as methacrylic acid esters such as methylmethacrylate, functional monomers such as unsaturated carboxylic acids, monomers having hydroxyls such as hydroxyethylmethacrylate, glycidylmethacrylate Such a monomer having an epoxide group, one or more kinds of monomers selected from unsaturated sulfonic acids, and a polyfunctional vinyl compound such as divinylbenzene as a cross-linking agent for forming a three-dimensional structure of polymer particles, Ethylene glycol dimethacrylate, trimethylolpropane triacrylate, diallyl phthalate, etc.,
An emulsion of polymer particles is prepared by emulsion polymerization in an aqueous medium in which a water-soluble polymer is dissolved as a protective colloid,
It is obtained by recovering polymer particles from this emulsion, drying them, and then crushing them with a jet mill and then classifying them.

The spherical crosslinked polystyrene particles are polyethylene-2,
It does not melt or melt during the polymerization of 6-naphthalate, and it does not melt during melting of the polymer during film molding.

When producing the biaxially oriented film of the present invention, spherical particles, or it and inert particles or internally deposited particles are pelletized before or after the polymerization of polyethylene-2,6-naphthalate in a polymerization kettle, after the completion of the polymerization. At this time, the polyethylene-2,6-naphthalate may be sufficiently kneaded in the extruder or in the case of melt extrusion into a sheet.

The polyethylene-2,6-naphthalate film of the present invention is obtained by melt-extruding polyethylene-2,6-naphthalate at a temperature of, for example, a melting point (Tm: ° C.) to (Tm + 70) ° C. and an intrinsic viscosity of 0.35 to 0.9 dl / g. A stretched film is obtained, and the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to
Stretching at a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polyethylene-2,6-naphthalate) at a draw ratio of 2.5 to 5.0, and then in the direction perpendicular to the stretching direction (when the first stage stretching is in the longitudinal direction). The second stage drawing is in the transverse direction)
Stretching is performed at a temperature of (° C) to (Tg + 70) ° C at a draw ratio of 2.5 to 5.0 times.

Then, the obtained biaxially stretched film (Tg + 20) ° C.
Heat set at a temperature of (Tg + 70) ° C, then stretch in the machine direction or transverse direction at a temperature 10 to 40 ° C higher than this heat setting temperature, and then stretch further in the transverse or longitudinal direction at a temperature 20 to 50 ° C higher than this temperature. , Draw ratio of 5.0-6.9 times in the longitudinal direction, total draw ratio in the transverse direction
It is obtained by setting it to 5.0 to 6.9 times.

The stretching method may be sequential biaxial stretching or simultaneous biaxial stretching, and the number of stretching in the machine direction and the transverse direction is not limited to this, and it can be obtained by several stretchings in the machine direction and the transverse direction. However, the number of times is not limited.

In any of the methods, finally, the biaxially oriented film is preferably heat set at a temperature of (Tg + 70) ° C. to Tm ° C., and further at 190 to 240 ° C., and the heat setting time is, for example, 1 to 60 seconds.

The polyethylene-2,6-naphthalate film of the present invention has a heat shrinkage of 0.15 or less, preferably 0.10 or less, more preferably 0.06 or less when the base film is heat-treated at 70 ° C. for 1 hour under no load. Is desirable. When this heat shrinkage ratio is larger than 0.15%, the skew of the magnetic tape also becomes large, and the distortion appears on the screen depending on the receiver.
It is not preferable because valuable records may be ruined.

In order to reduce the heat shrinkage rate of the high Young's modulus film in this way, the film after heat treatment is heated under low tension,
This can be done by relaxing in the longitudinal direction. As a method of relaxing in the longitudinal direction, for example, a method of relaxing in a non-contact state under heating and low tension by a floating treatment method by aerodynamic force; a method of relaxing by giving a speed difference between a heating roll and a cooling roll each having a nip roll. Alternatively, there is a method of loosening in the vertical direction by gradually slowing down the moving speed of the clip holding the film in the tenter, but any method can be used as long as it can loosen in the vertical direction.

The thickness of the polyethylene-2,6-naphthalate film is preferably 1 to 50 μm, more preferably 1 to 25 μm, and particularly preferably 1 to 15 μm.

The polyethylene-2,6-naphthalate film of the present invention has a small coefficient of friction during running and has very good operability. When this film is used as the base of a magnetic tape, the base film is scarcely scraped off due to contact friction with the running portion of the magnetic recording / reproducing apparatus (hardware), and the durability is good and high electromagnetic conversion is obtained.

Further, the biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a good winding property during film formation, is less likely to cause wrinkles, and is dimensionally stable and sharply cut in the slit stage. It has the advantage of being

By the combination of the above advantages as a film product and the advantages at the time of film formation, the polyethylene-2 of the present invention,
6-naphthalate film is particularly useful as a base film for high-grade magnetic fields.
Also, the product has an advantage that it can be easily and stably produced.

The polyethylene-2,6-naphthalate film of the present invention is a high-grade magnetic recording medium, for example, an ultra-thin film for long-time recording of audio and video, a high-density recording magnetic film, and a magnetic recording film for recording and reproducing high-quality images. For example, it is suitable as a metal or vapor deposited magnetic recording material.

The magnetic layer and the method for providing the magnetic layer on one side or both sides of the film are known per se, and the known magnetic layer and the method for providing the magnetic layer can be adopted in the invention.

For example, when the magnetic layer is provided by a method of applying a magnetic coating material on polyethylene-2,6-naphthalate film, the ferromagnetic powder used for the magnetic layer is γ-Fe ₂ O
Known ferromagnets such as ₃ and Co-containing γ-Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , CrO ₂ and barium ferrite can be used.

The binder used together with the magnetic powder is a known thermoplastic resin, thermosetting resin, reactive resin, or a mixture thereof. Examples of these resins include vinyl chloride-vinyl acetate copolymers and polyurethane elastomers.

The magnetic coating material further includes an abrasive (eg α-Al ₂ O ₃ etc.), a conductive agent (eg carbon black etc.), a dispersant (eg lecithin etc.), a lubricant (eg n-butyl stearate,
Lecithin acid, etc.), a curing agent (eg epoxy resin etc.) and a solvent (eg methyl ethyl ketone, methyl isobutyl ketone, toluene etc.) and the like.

[Effects of the Invention] The polyethylene-2,6-naphthalate film of the present invention has a flat surface, has no high protrusions, has a high Young's modulus and is excellent in dimensional stability, and is a high-quality base film for magnetic tape. Is extremely excellent as

[Examples] Hereinafter, the present invention will be further described with reference to Examples. In addition,
Various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Film surface roughness (Ra) It was measured according to JIS B 0601. Tokyo Seimitsu Co., Ltd.
Using a stylus surface roughness meter (SURFCOM 3B) manufactured by K.K., a chart (film surface roughness curve) was placed under the conditions of a needle radius of 2 μm and a weight of 0.07 g. A portion of the measurement length L is extracted from the film surface roughness curve in the direction of the center line, and the center line of the extracted portion is taken as the X axis and the longitudinal magnification direction is taken as the Y axis, and the roughness curve is taken as Y = f (x). When expressed by, the value (Ra: μm) given by the following equation is defined as the film surface roughness.

In the present invention, 8 pieces were measured with a reference length of 0.25 mm, and Ra was expressed as an average value of 5 pieces excluding 3 pieces having the larger values.

(2) Protrusion distribution Using a three-dimensional roughness meter (SE-3CK) manufactured by Kosaka Laboratory, needle diameter 2 μm, R needle pressure 30 mg, measurement length 1 mm, sampling pitch 2 μ
m, cut-off 0.25 mm, vertical magnification 20,000 times, horizontal magnification 200 times, the number of scanning lines is 150, and the protrusion distribution is measured. The protrusion height (x axis) is the area ratio from the reference level. Is 70
The protrusion height (z level) at the point of% was defined as the O level, and the difference from the height was defined as the protrusion height, and the number of protrusions corresponding thereto was plotted on the y-axis.

(3) Young's modulus The film is cut into a sample width of 10 mm and a length of 15 cm, and the gap between chucks is 1
The tensile strength was set to 00 mm and the tensile speed was 10 mm / min and the chart speed was 500 mm / min. The Young's modulus was calculated from the tangent line of the rising portion of the obtained load-elongation curve.

(4) Skew For skew characteristics, a videotape recorded at room temperature (20 ° C) and normal humidity is heat-treated at 70 ° C for 1 hour and then reproduced again at room temperature and normal humidity to read the deviation amount at the head switching point.

(5) Electromagnetic conversion characteristics of magnetic coating film α-Fe ₂ O ₃ obtained by thermal decomposition of needle-shaped α-FeOOH containing 5% of cobalt was hydrogen-reduced to obtain black ferromagnetic metal powder. . The specific surface area of this ferromagnetic metal powder was 44 m ² / gr as measured by the BET method by the N ₂ gas adsorption method.

100 parts by weight of the above-mentioned ferromagnetic metal powder (hereinafter simply referred to as "part") and the following composition were kneaded and dispersed in a ball mill for 12 hours.

Polyester polyurethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black 1 part Butyl acetate 70 parts Methyl ethyl ketone 35 parts Cyclohexanone 100 parts Further after dispersion Add 1 part of fatty acid ester (amyl stearate) and knead for 15-30 minutes. Further, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added, and the mixture was subjected to high-speed shear dispersion for 1 hour to prepare a magnetic coating solution. Thickness of the obtained coating liquid
3.0μ dry film thickness on 10.0μm polyester film
It was applied so that it would become m.

Then, after orientation treatment in a direct current magnetic field, it was dried at 100 ° C. After drying, calendering treatment was applied and slit to a 1/2 inch width to obtain a magnetic tape for video.

The video characteristics are the values obtained by measuring the playback output at 4 MHz using a VHS system VTR (product name "HR 7300" manufactured by Victor Company of Japan, Ltd.) in which the recording / playback head was modified to Sendust alloy. The standard tape is a commercially available γ-Fe ₂ O ₃ layer coating type 1/2 inch VHS tape.

The CN ratio is a CN ratio when a carrier signal of 4 MHz is recorded and the level of the reproduced amplitude-modulated signal at 3.0 MHz is taken as a noise level.

(6) Coefficient of friction A fixed glass plate is placed under the two stacked films, and the film under the stacked films (the film in contact with the glass plates) is taken by a constant speed roll ( about
(10 to 15 cm / min) A detector is fixed to one end of the upper film (the end opposite to the take-up direction of the lower film) and the tensile force between the films is detected. The thread used at that time has a weight of 1 to 5 kg and a lower area of 10 to 100 cm ² .

(7) Heat shrinkage rate First, measure the length of the sample, and then heat the sample by leaving it in an air thermostat held at 70 ° C for 1 hour in a tension-free state for heat treatment, and then measuring the length after cooling. Is measured at room temperature. Then, the heat shrinkage is determined from each length before and after the heat treatment.

(8) Particle size of spherical particles, etc. (8-1) Spherical particles, for example, spherical silica particles, spherical silicone particles, and spherical crosslinked polystyrene particles, have the following states for particle size measurement.

B) When obtaining the average particle size, particle size ratio, etc. from fine powder.

B) When obtaining the average particle size, particle size ratio, etc. of the fine powder particles in the film.

B) From fine powder: Scatter spherical fine particles on the electron microscope sample stand so that individual particles do not overlap as much as possible, and form a gold thin film vapor deposition layer with a thickness of 200 to 300Å on this surface with a gold sputtering device. , Observing with a scanning electron microscope at 10000-30000 times,
Determine the major axis (maximum diameter: Dli), the minor axis (minimum diameter: Dsi) and the equivalent circle diameter (Di) of at least 100 particles with Luzex 500 manufactured by Nippon Regulator Co., Ltd. The major axis (maximum diameter: Dl), minor axis (minimum diameter: Ds), and average particle diameter () of the spherical particles are represented by the number average values represented by the following equations.

B) In case of spherical fine particles in the film: A small piece of the sample film is fixed on the sample stage for a scanning electron microscope, and the sputtering device manufactured by JEOL Ltd.) JFC-110.
The film surface is subjected to ion etching under the following conditions using a 0-type ion sputtering device). The condition is that the sample is grounded in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, and ion etching is performed for about 10 minutes at a voltage of 0.25 KV and a current of 12.5 mA. Further, gold spatter is applied to the film surface with the same device, and 1000 is taken with a scanning electron microscope.
Observed at 0 to 30,000 times, and use Luzex 500 manufactured by Nippon Regulator Co., Ltd. to obtain at least 100 particles with the longest diameter (maximum diameter: D
li), minor axis (minimum diameter: Dsi), and area equivalent circle diameter (Di). Hereafter, the same procedure as the above (a) is performed.

(8-2) Other inert particles Average particle size (DP) Shimadzu CP-50 type Centrifugal particle size analyzer (Centrifugal Particle Siz
e Analyser). From the integrated curve of particles of each particle size calculated based on the obtained centrifugal sedimentation curve and its abundance, read the particle size corresponding to 50 mass%,
This value is defined as the above average particle size (see Book "Particle Size Measurement Technology", Nikkan Kogyo Shimbun, 1975, pp. 242-247).

(8-3) Relative standard deviation a) Relative standard deviation of spherical particles The relative standard deviation is calculated from the area circle equivalent diameter (Di) in the above item (8-1) based on the following formula.

Here, Di: area circle equivalent diameter of individual particles (μm) n: represents the number of particles.

B) Relative standard deviation of other inert particles The difference particle size distribution is obtained from the integrated curve in the above item (8-2), and the relative standard deviation is calculated based on the following definition formula of relative standard deviation.

Here, Di; each particle diameter obtained in the item (8-2); average diameter n obtained in the item (8-2) n; number of divisions when the integrated curve in the item (8-2) is obtained φi; It represents the existence probability (mass percent) of particles of each particle size.

(9) Edge damage Using a commercially available VHS VTR, winding the T-120 cassette for the first 3 minutes and running it 30 times in the replay mode, then taking out the cassette and visually inspecting the loading / unloading section and the running section. Then, it was investigated whether or not the edge portion of the tape had a scratch. The edge damage was determined by examining 30 volumes and displayed as follows.

○: Scratched tape 2 rolls or less / 30 rolls △: 〃 3 to 4 rolls / 〃 ×: 〃 5 rolls or more / 〃 Examples 1 to 3, 5, 6, Comparative Examples 3, 4, 6 Shown in Table 1 Pellets of polyethylene-2,6-naphthalate (homopolymer) having an intrinsic viscosity of 0.60 containing the added particles were dried at 170 ° C. for 4 hours. The pellets were melt-extruded by a usual method to obtain an unstretched film having a thickness of 355 μm. The unstretched film was formed into a film as shown in Table 1 and the evaluation results were obtained.

Example 4 An unstretched film having a thickness of 375 μm was produced in the same manner as in Example 1. The unstretched film was formed into a film as shown in Table 1 and the evaluation results were obtained.

Comparative Example 1 An unstretched film having a thickness of 255 μm was produced in the same manner as in Example 1, and the unstretched film was formed into a film as shown in Table 1
Was obtained.

Comparative Example 2 An unstretched film having a thickness of 215 μm was produced in the same manner as in Example 1, and the unstretched film was formed into a film as shown in Table 1. When this was evaluated, the results shown in Table 1 were obtained.

Comparative Example 5 Pellets of polyethylene terephthalate (homopolymer) having an intrinsic viscosity of 0.62 containing the additive particles shown in Table 1 were prepared.
It was dried at 160 ° C. for 4 hours. This polyethylene terephthalate was extruded by a usual method to obtain an unstretched film of 265 μm. The unstretched film was formed into a film as shown in Table 1 and the evaluation results were obtained.

As can be seen from the evaluation results in Table 1, Examples 1 to 4 have extremely good edge damage, electromagnetic conversion characteristics, and skew as a thin high-quality video tape, and have a low coefficient of friction between films and a good film winding property. It was

In Example 5, the particle size distribution of the mixed titanium oxide particles is slightly larger than that of the added particles of Examples 1 to 4, so that the electromagnetic conversion characteristics are slightly inferior and the friction coefficient between the films is slightly higher. However, the requirements of the present invention were satisfied.

In Example 6, the shape of the particles was slightly uneven as compared with Example 5, the electromagnetic conversion characteristics were slightly inferior, and the friction coefficient between the films was slightly higher. However, it satisfies the requirements of the present invention.

In Comparative Example 1 or 2, the Young's modulus was deviated in the vertical direction, was low in the horizontal direction, and the difference was too large, the head touch was poor, the electromagnetic conversion characteristics were poor, and the edge damage was also poor.

In Comparative Examples 3 and 4, the added particles were large in particle size, the relative standard deviation was large, and the projection distribution graph was not satisfied, so that the electromagnetic conversion characteristics were unsatisfactory. Further, in Comparative Example 4, since the heat treatment temperature in the film forming step was low and the heat relaxation treatment was not performed, the heat shrinkage rate of the film at 70 ° C. × 1 hour was too large and the skew of the tape was unsatisfactory. .

In Comparative Example 5, since polyethylene terephthalate was used, the Young's modulus in the machine direction and the transverse direction were both low, and the electrical conversion characteristics and edge damage were both unsatisfactory.

In Comparative Example 6, the electromagnetic conversion characteristics were unsatisfactory because the projection distribution graph was not satisfied.

[Brief description of drawings]

Figure 1 shows the height of protrusions (μm) on the film surface and the number of protrusions (k / m).
is a graph showing the relation between m ^2).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08L 67:00 C08L 67:00 (72) Inventor Tatsuya Ogawa 3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture Issue: Teijin Ltd. Plastics Research Laboratory (56) Reference JP-A-63-135339 (JP, A) JP-A-63-289029 (JP, A)

Claims (5)

(57) [Claims] 1. The longitudinal Young's modulus (My) and the lateral Young's modulus (Ty) are both 650 kg / mm ² or more and the difference | My−Ty
Is less than 200 kg / mm ² and surface roughness Ra is more than 0.003 μm
It is less than 0.010 μm, and the number of protrusions on the surface is 30 /
In the distribution curve showing the relationship between the number of protrusions (y: ke / mm ² ) and the height of protrusions (x: μm) obtained in the region of mm ² or more, the curve of the portion larger than the maximum value of the protrusion distribution curve is log ₁₀ y = -12x
A biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium, which is characterized by intersecting +3.7 and having no protrusion of 0.2 μm or more in this region. 2. The biaxially oriented polyethylene-2,6- for magnetic recording media according to claim 1, wherein the heat shrinkage in the longitudinal direction of the film when heat-treated at 70 ° C. for 1 hour under no load is 0.15% or less.
Naphthalate film. 3. Silica having a particle size ratio (major axis / minor axis) of 1.0 to 1.2, a relative standard deviation of particles defined by the following formula of 0.5 or less, and an average particle size of 0.005 to 0.6 μm. Biaxially oriented polyethylene-2,6 for magnetic recording media according to claim 1 or 2, containing 0.005 to 3 wt% of one or more kinds of spherical fine particles selected from silicone resin particles and crosslinked polystyrene particles.
-Naphthalate film. Here, Di: area circle equivalent diameter of individual particles (μm) n: represents the number of particles. 4. The biaxially oriented polyethylene-2,6-naphthalate film for magnetic recording media according to claim 3, wherein the silica particles are obtained by hydrolyzing an organometallic compound in an alcoholic solution. 5. The biaxially oriented polyethylene for a magnetic recording medium according to claim 3, comprising spherical fine particles and particles of other inert inorganic or organic additive particles and / or particles containing a catalyst residue or the like deposited in the polymer. -2,6-naphthalate film.