JPH10214415A - Biaxially oriented polyethylene terephthalate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of high edges when a film is cut into a tape in the longitudinal direction and to obtain a tape suitable for a magnetic recording medium by increasing the elastic modulus in the width direction and controlling the surface roughness, surface waviness and high edge index to specified ranges. SOLUTION: In this biaxially oriented polyethylene terephthalate film produced by laminating two or more layers, the elastic modules ETD in the width direction is controlled to >=6GPa so as to improve the head touch when the film is used for a magnetic tape and to avoid edge damages. The elastic modulus EMD in the longitudinal direction is controlled to >=4GPa to prevent elongation of the tape during rapid travelling and rewinding and to prevent etching damages. Moreover, the high edge index is controlled to <=20% so as to prevent production of high edges when the film is cut into a tape. The outermost layer of the film is formed to have <=20% thickness of the whole thickness, and the intrinsic viscosity of the coating material is controlled to <=0.55dl/g so as to make the film forming process easy and to suppress the waviness index of the film surface to a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biaxially oriented polyethylene terephthalate film.

[0002]

2. Description of the Related Art Polyethylene terephthalate film is used for magnetic recording media by utilizing its excellent mechanical properties, thermal properties, electrical properties, surface properties, optical properties, heat resistance, chemical resistance and the like. Widely used for various applications such as, for condensers and packaging.

[0003] Films used in these applications are usually cut into widths according to the applications. Japanese Patent Application Laid-Open No. 63-25 / 1988 discloses a technique for preventing chips from being generated during cutting.
1221 and the like are known. As a technique for solving the problem at the time of cutting, techniques such as Japanese Patent Application Laid-Open No. 63-95933 are known. Further, when cutting the film, the temperature around the cutter is set to a low temperature of 20 ° C. or less, and the film is cut.

[0004]

In accordance with the needs for high quality and compactness of these products, the required characteristics of polyethylene terephthalate films are becoming more and more severe. Among the above applications, especially for magnetic recording media, the base film has been thinned to a thickness of 10 μm or less with high quality, long-time recording, and compactness.

In magnetic recording media, a base film of a magnetic tape for a recorder equipped with a rotary head typified by a VHS is generally improved in head touch by increasing rigidity in a width direction rather than a longitudinal direction. It is a target. A film in which the rigidity in the width direction is increased by stretching is called a horizontal ten (horizontal tensioned) base film.

[0006] Such a horizontal ten base film is liable to cause a phenomenon called "high edge" in which a film edge is cut along a cut surface when the film is cut using a shear cutter or the like and rolled up. When the film is wound up with the high edge generated, only the edge portion of the film is elongated. For example, when a magnetic layer is provided on the surface to form a magnetic tape, the flatness is impaired, and the RF There is a problem that the output waveform is disturbed. As described above, since the influence of the high edge tends to be remarkable in recent years in which the film is becoming thinner, the conventional technology cannot sufficiently solve this problem.

An object of the present invention is to reduce the mechanical properties such as the modulus of elasticity of a thinned film without reducing it.
An object of the present invention is to provide a biaxially oriented polyethylene terephthalate film which does not cause a problem such as a high edge.

[0008]

The biaxially oriented polyethylene terephthalate film of the present invention for this purpose has a high edge index of 20% or less when cut in the longitudinal direction and an elastic modulus in the width direction. ETD (GP
a) is 6.0 or more, and the elastic modulus in the longitudinal direction EMD (GPa)
Is 4.0 GPa or more, the center line surface roughness of at least one film surface is 10 nm or less, and the undulation index is 1
0 or less.

In the biaxially oriented polyethylene terephthalate film of the present invention, the high edge index defined below when cut in the longitudinal direction is 20% or less, and the elastic modulus ETD (GPa) in the width direction is 6.0 or more. The elastic modulus EMD (GPa) in the longitudinal direction is 4.0 GPa or more, and the center line surface roughness of at least one film surface is 10 n.
m or less, and a undulation index of 10 or less, a thin film having a film thickness of 10 μm or less hardly causes a high edge during cutting, and excellent head touch when used as a base film for a magnetic medium ( That is, it is intended to obtain a magnetic medium having excellent electromagnetic conversion characteristics.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The biaxially oriented polyethylene terephthalate film of the present invention has an elastic modulus ETD (GP
a) is 6.0 or more, more preferably 6.5 or more, and still more preferably 7.0 or more. If the elastic modulus ETD (GPa) in the width direction is not less than 6.0, the thickness is particularly 10
In the case of a thin film of less than μm, when used as a base film for a magnetic medium (especially in the case of a system equipped with a rotating head), good head touch cannot be obtained, and when the tape runs, Edge damage is likely to occur near the position control post and near the cassette entrance.

The biaxially oriented polyethylene terephthalate film of the present invention needs to have a longitudinal elastic modulus EMD (GPa) of 4 GPa or more, and preferably 4.
It is 5 GPa or more, more preferably 5.0 GPa or more. If the elastic modulus in the longitudinal direction is less than this, when the magnetic tape is used, the tape will stretch when the tension applied to the tape suddenly changes, such as fast-forward or rewind, or the tape edge will be damaged in a wakame shape. The adverse effects such as becoming easy to occur occur.

The upper limit of the elastic modulus in the longitudinal direction and the width direction is not particularly limited, but about 12 GPa is the limit at which industrial production is possible.

The biaxially oriented polyethylene terephthalate film of the present invention has a high edge index of 20 which indicates the difficulty of plastic deformation near the surface of the cut when cutting the film.
% Or less. When the high edge index is larger than this value, when a magnetic layer is provided on the surface of the base film and the tape is cut into a tape width, there is a high possibility that a so-called high edge in which the edge portion rises after winding up. The high edge index is preferably 18% or less, more preferably 16% or less.

The polyethylene terephthalate constituting the biaxially oriented film of the present invention comprises polyethylene terephthalate containing 85 mol% or more of ethylene terephthalate in a repeating unit. However, two or more kinds of polyethylene terephthalates may be mixed or a copolymer may be used as long as the above-mentioned condition of the ethylene terephthalate content is satisfied, as long as the object of the present invention is not impaired. Further, within the range not hindering the present invention, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment,
Organic lubricants such as dyes, fatty acid esters, and waxes may be added to the extent that they are usually added.

The biaxially oriented polyethylene terephthalate film of the present invention is not particularly limited, but preferably has a laminated structure of at least two layers. If it is a single layer,
For example, when used for a magnetic recording medium, if particles are added, projections on the surface may not be aligned, and output characteristics and running properties may be deteriorated. The number of layers is preferably two or more, but the case of three layers is preferable because the effect of the present invention is further improved.

The outermost layer on at least one side of the biaxially oriented polyethylene terephthalate film of the present invention, which has a laminated structure of at least two layers or more, is not particularly limited.
Preferably, the particles contain particles, and the relationship between the average particle size d (nm) of the particles and the thickness t (nm) of the outermost layer is 0.1 ≦ t / d ≦ 10. For example, when used for a magnetic recording medium, if t / d is smaller than 0.1, the output characteristics deteriorate, and
When / d is larger than 10, the tape running property deteriorates.

The type of particles may be either inorganic particles or organic particles. The organic particles are not particularly limited, but are preferably crosslinked organic particles, particularly polydivinylbenzene particles, from the viewpoint of output characteristics. The polydivinylbenzene particles mean particles mainly composed of divinylbenzene as a crosslinking component. Among them, those in which divinylbenzene accounts for 51% or more, preferably 60% or more, more preferably 75% or more of the particle component are preferable. Other ingredients include
Although not particularly limited, for example, ethyl vinyl benzene,
Non-crosslinking components such as diethylbenzene are exemplified.
Further, silicone particles are also preferably exemplified. The silicone particles preferably include two-dimensionally crosslinked organopolysiloxane as a main component. As other particles, aggregated particles such as alumina, zirconia, silica and titanium oxide, or monodispersed particles such as calcium carbonate, colloidal silica and titanium oxide can also be used by appropriate particle dispersion in the polymer. A plurality of these particles may be used in combination.

When the biaxially oriented polyethylene terephthalate film of the present invention has a laminated structure of three or more layers, the intermediate layer (the layer other than the outermost layer) is not particularly limited, but may contain particles. The type of particles may be either inorganic particles or organic particles.

One preferred embodiment (form 1) of the biaxially oriented polyethylene terephthalate film of the present invention has a laminated structure having at least a two-layer structure or more, and the laminated thickness of at least one outermost layer is 20% or less of the whole film. Wherein the intrinsic viscosity (IV) of polyethylene terephthalate constituting the outermost layer is 0.55 (dl / g) or less. When the intrinsic viscosity of the outermost layer is 0.55 (dl /
g) or less, more preferably 0.50 (dl / g) or less, because the effects of the present invention are further enhanced. On the other hand, if the intrinsic viscosity is less than 0.40 (dl / g), the melt viscosity is too small, and it is difficult to extrude the film stably to form a film.
(Dl / g) or more, but is not particularly limited.

On the other hand, when the lamination thickness is larger than the above range, the possibility that the undulation index of the film surface deviates from a required range increases, which is not preferable.

In this case, it is preferable that the outermost layer contains no particles, or at least contains 0.3% by weight of inert particles having an average particle size of 0.3 μm or less even if contained. When the average particle diameter of the contained particles exceeds 0.3 μm, the possibility that the undulation index of the film surface deviates from a required range increases, or dust is generated from the film edge when the film is cut. It is not preferable because it becomes easier. On the other hand, if the content of the particles exceeds 0.3% by weight, the particles are likely to aggregate, and the aggregation of the particles undesirably results in dropout or an increase in the error rate when formed into a magnetic tape. here,
As the particles, the above-mentioned particles are preferably used. Also,
The average particle diameter d (nm) of the particles and the thickness t (n) of the outermost layer
It is preferable that the relationship m) satisfies the above condition.

Another preferred embodiment (form 2) of the biaxially oriented polyethylene terephthalate film of the present invention is:
The tear propagation resistance in the longitudinal direction is 1000 N / m or more and 5000
N / m or less, and the viscoelastic parameter tanδ in the width direction
Is set to 0.010 or less. When the tear resistance in the longitudinal direction of the entire film is lower than 5000 N / m, high edges are less likely to occur, but when it is lower than 1000 N / m, adverse effects such as breakage of the film during film formation or magnetic tape production occur. Further, the value of the viscoelastic parameter tan δ in the width direction of the film is set to 0.0
When the thickness is set to 10 or less, when the film is cut, the swelling due to the plastic deformation of the cut surface is reduced, thereby further suppressing the high edge. In the case of a thin film having a film thickness of 10 μm or less, it is not sufficient to set the tear resistance within the above range, and the viscoelastic parameter ta is not sufficient.
It is particularly preferred that the value of nδ be 0.010 or less.

In each of the first and second embodiments, the center line surface roughness (Ra) of at least one film surface
Must be 10 nm or less and the Unelli index is 10 or less. If Ra is larger than 10 nm or the undulation index is larger than 10, even if the above-described first and second embodiments are devised, not only the high edge reduction effect is small but also
When a magnetic tape is used, satisfactory electromagnetic conversion characteristics are hardly obtained.

The thickness of the biaxially oriented polyethylene terephthalate film of the present invention is not particularly limited.
0 μm, preferably 3 to 10 μm, more preferably 4 μm
〜7 μm is used.

The biaxially oriented polyethylene terephthalate film of the present invention is suitably used for digital magnetic recording tapes and magnetic recording media such as data storage for computers and the like. It can also be used for other purposes.

The method for producing the biaxially oriented polyethylene terephthalate film of the present invention will be described, but is not limited thereto.

First, as a method for containing particles in polyethylene terephthalate constituting a film, particles are dispersed in a predetermined ratio in the form of a slurry in ethylene glycol as a diol component, and the ethylene glycol is mixed with a predetermined dicarboxylic acid component. The method of polymerizing is preferred. When the particles are added, for example, if a water sol or an alcohol sol obtained during the synthesis of the particles is once added without being dried, the dispersibility of the particles is good, and the output characteristics can be improved. It is also effective to directly mix a water slurry of the particles with predetermined polyethylene terephthalate pellets and knead the mixture into a polyethylene terephthalate using a vented twin-screw extruder. As a method of adjusting the content and number of particles, a master of high concentration particles is prepared by the above method, and the master is diluted with polyethylene terephthalate which is not substantially contained in the particles at the time of film formation to reduce the content of the particles. The method of adjusting is effective.

Next, the polyethylene terephthalate pellets obtained by the above method are mixed at a predetermined ratio, dried, fed to a known melt extruder, extruded from a slit die into a sheet, and cast on a casting roll. The above is cooled and solidified to form an unstretched film. Further, in the case of a laminated film of at least two layers, two or three or more extruders, using two or three layers of a manifold or a confluence block, the polyethylene terephthalate in a molten state to form a film layer constituting a laminated portion, The sheet is laminated on a film layer constituting a base layer portion, and two or more sheets are extruded from a die and cooled on a casting roll to form an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer channel is effective. Also, 3
In the case of forming a laminated film having two or more layers, when a polymer having an intrinsic viscosity of 0.55 or less is used for the intermediate layer, and the thickness of the intermediate layer is 40% or more of the whole film, the tear resistance and tan δ of the preferred embodiment 2 of the present invention are reduced It is very effective to set the value in a preferable range.

Next, the unstretched film is biaxially stretched,
Biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, stretching in the longitudinal direction is divided into three or more stages, and the total longitudinal stretching ratio is 3.0 to 6.5 times. The method is particularly preferred.
Although the stretching temperature in the longitudinal direction cannot be unconditionally determined, usually, the first stage is performed at 50 to 150 ° C., preferably 100 to 130 ° C.
It is effective to set the temperature to ° C. and to lower the temperature after the second stage. In this case, maintaining the temperature at 100 ° C. or more for 3 seconds or more before stretching in the first stage of stretching is extremely effective for setting the value of the tear resistance of the preferred embodiment 2 of the present invention to a preferred range. . The longitudinal stretching speed is 5,000 to
It is preferable to carry out in the range of 50,000% / min. As a stretching method in the width direction, for example, a method using a stenter is generally used. The stretching ratio in the width direction is 3.0 to 7.0 times, the stretching speed is 1000 to 20000% / min, and the temperature is 80 to 1.
It is preferable to carry out in the range of 60 ° C. Further, if necessary, re-longitudinal stretching and re-lateral stretching are performed. As the stretching conditions in this case, the stretching in the longitudinal direction is preferably performed at a temperature of 90 to 180 ° C., the stretching ratio is 1.1 to 2.0 times, and the stretching method in the width direction is preferably a method using a stenter. The stretching ratio is preferably 1.1 to 2.0 times.

Next, the stretched film is heat-treated. The heat treatment temperature in this case differs depending on the type of polyethylene terephthalate and cannot be unconditionally determined.
0 ° C., preferably 180-220 ° C., time 0.2-
It is preferable to carry out within 30 seconds. In particular, it is performed at a temperature of 200 ° C. or more for 2 seconds or more, and at this time, the film width is 2 to 2.
Heat treatment with relaxation of about 5% is extremely effective for adjusting the value of tan δ in the preferred embodiment 2 of the present invention to a preferred range.

[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) Modulus of elasticity According to the method specified in JIS K-7127,
Using a tensile tester manufactured by Toyo Sokki, 25 ° C, 65% RH
Was measured. The sample was cut out into a strip having a width of 10 mm and a length of 200 mm in the measurement direction. The initial distance between the tension chucks was 100 mm, and the tension speed was 300 mm / min.

(2) Heat shrinkage rate Measured according to the method specified in JIS C-2318. However, the temperature of the oven was 80 ° C., and the holding time was 30 minutes.

(3) Intrinsic viscosity [η] (unit: dl / g) A value calculated from the following formula from the solution viscosity measured at 25 ° C. in o-chlorophenol is used. That is, ηsp / C = [η] + K [η] ² · C, where ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of the dissolved polymer per 100 ml of solvent (g / 100 m
1, usually 1.2), and K is a Haggins constant (assumed to be 0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(4) Average particle size of particles The polymer is removed from the film by a plasma low-temperature incineration method to expose the particles. Processing conditions are selected such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. SEM magnification is about 2
000 to 10000 times, and the field of view in one measurement is 1
The side is selected from a range of about 10 to 50 μm. By changing the observation point, the volume average diameter d is obtained from the particle diameter and the volume fraction thereof using the following equation when the number of particles is 5000 or more.

D = Σd _i · Nv _i where d _i is the particle size and Nv _i is its volume fraction. If the particles are significantly damaged by the plasma low-temperature ashing process due to organic particles or the like, the following method may be used. The cross section of the film is observed at a magnification of 10,000 times or more using a transmission electron microscope (TEM). TEM section thickness is about 100n
m, measurement is performed at 100 places or more at different locations, and the volume average diameter d is determined from the above equation.

(5) Thickness of Film Lamination (Thickness of Outermost Layer) When particles are contained in the lamination part, a depth of 300 m from the surface is measured using a secondary ion mass spectrometer (SIMS).
Among the particles in the film in the range of 0 nm, the concentration ratio (M ⁺ / C ⁺ ) of the element resulting from the particles having the highest concentration and the carbon element of polyethylene terephthalate is defined as the particle concentration, and the thickness direction from the surface to the depth of 3000 nm. Perform an analysis. 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, when particles are contained in the laminated portion, the particle concentration once having a maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration was の of the local maximum value (this depth was deeper than the local maximum value) was determined, and this was defined as the lamination thickness. The conditions are as follows.

Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by Atomika, Germany Measurement conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 kV Primary ion current: 200 nA Raster area: 400 μm □ analysis area: gate 30% measurement vacuum degree: 8.0 × 10 ^over 7 Pa E-GUN: 0.5kV- 3.0A

In the case where the particles most contained in the range from the surface layer to the depth of 3000 nm are organic polymer particles, it is difficult to measure by SIMS. Therefore, XPS (X-ray photoelectron spectroscopy) and IR ( A depth profile similar to the above may be measured by infrared spectroscopy or the like to determine the lamination thickness. In particular, when no particles are contained, the interface can be recognized from a difference in contrast due to a difference in polymer in cross-sectional observation using an electron microscope or the like, and the lamination thickness can be determined. Further, after the laminated polymer is peeled off, the laminated thickness can be determined using a thin film step measuring device.

(6) High edge index A carbide blade cutter is attached to the press cutting, and an approximately 10 cm square film attached to the stage is cut. The sliced film is sliced at right angles to the cut surface with a razor blade, and the sliced surface is observed with an optical microscope. At this time, with respect to the film thickness, it was measured how much the area near the surface cut by the carbide blade cutter was raised, and the percentage of the raised area with respect to the film thickness was defined as a high edge index.

(7) Tear Propagation Resistance Using a light load type tear tester (Toyo Seiki Co., Ltd.), the ASTM-
Measured according to D-1922. The sample size is 51 x 54mm
Insert a 13mm cut in the longitudinal direction of the film, leaving 51mm
The reading at the time of tearing was read.

The tearing resistance is reduced by strengthening the orientation by strengthening the stretching in the longitudinal direction or the like. If the orientation is the same, the intrinsic viscosity of the polymer tends to decrease as the intrinsic viscosity decreases.

(8) Viscoelastic parameter tan δ Using a dynamic viscoelasticity meter Leo Vibron DDV-II-EA manufactured by Toyo Bold-in Co., Ltd.
At 1 Hz, viscoelasticity was measured in the range of 0 ° C to 150 ° C,
The value of tan δ (ratio of storage elastic modulus to loss elastic modulus) at 50 ° C. was used as an index.

(9) Output Characteristics (C / N) On the surface of the film of the present invention, a magnetic paint and a non-magnetic paint having the following compositions are applied in multiple layers by means of an extrusion coater (the upper layer is made of a magnetic paint and has a coating thickness of 0.1 μm. The thickness of the magnetic lower layer was appropriately changed), magnetically oriented, and dried. Then, a back coat layer having the following composition is formed on the opposite surface by a known means, and then, with a small test calender (steel / steel, 5 steps), temperature: 85 ° C., linear pressure: 20
After calendering at 0 kg / cm, it is cured at 60 ° C. for 48 hours. The raw tape was slit into a width of 8 mm to prepare a pancake. Next, a length of 200 m from this pancake was incorporated into a cassette to form a cassette tape.

This tape is provided with a commercially available VTR for Hi8 (S
7MHz using ONY EV-BS3000)
C / N at ± 1 MHz was measured.

(Composition of magnetic paint) Ferromagnetic metal powder: 100 parts by weight Modified sodium sulfonate vinyl chloride copolymer: 10 parts by weight Modified sodium sulfonate modified polyurethane: 10 parts by weight Polyisocyanate: 5 parts by weight Stearic acid: 1.5 parts by weight-Oleic acid: 1 part by weight-Carbon black: 1 part by weight-Alumina: 10 parts by weight-Methyl ethyl ketone: 75 parts by weight-Cyclohexanone: 75 parts by weight-Toluene: 75 parts by weight (nonmagnetic lower layer) Composition of paint) ・ Titanium oxide: 100 parts by weight ・ Carbon black: 10 parts by weight ・ Na sulfonic acid modified vinyl chloride copolymer: 10 parts by weight ・ Na sulfonic acid modified polyurethane: 10 parts by weight ・ Methyl ethyl ketone: 30 parts by weight ・ Methyl Isobutyl ketone: 30 parts by weight Toluene: 30 parts by weight・ Carbon black (average particle size 20 nm): 95 parts by weight ・ Carbon black (average particle size 280 nm): 5 parts by weight ・ α-alumina: 0.1 parts by weight ・ Zinc oxide: 0.3 parts by weight ・ Sulfone Na-modified acid polyurethane: 20 parts by weight-Na-modified sulfonated vinyl chloride copolymer: 30 parts by weight-Cyclohexanone: 200 parts by weight-Methyl ethyl ketone: 300 parts by weight-Toluene: 100 parts by weight

(10) Slit Property of Magnetic Tape With respect to the tapes whose output characteristics were measured, when slitting, some pancakes were found to have high edges (visual judgment) at poor (×) and high edges Those that were not obtained were rated as excellent (O). Further, for these tapes, a cross section perpendicular to the longitudinal direction was observed in the same manner as the high edge index of the film, and the high edge index of the magnetic tape was determined.

(11) Center Line Average Roughness Ra The center line average roughness Ra, the maximum height Rt (peak to valley), and the protrusion interval Sm were measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. Was measured. The conditions were as follows, and the value was determined as the 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 definitions of Ra, Sm, Rt, and the like are, for example, those shown in Jiro Nara, "Method of Measuring and Evaluating Surface Roughness" (General Technology Center, 1983).

(12) Unelli Index The above Ra measurement was performed on the same sample in addition to the cutoff value of 0.08 mm, 0.008 mm and 0.25 mm.
Set to. At this time, the values of the respective measured values are plotted with the cutoff value on the horizontal axis (log scale) and the value of Ra on the vertical axis, and the slope of the straight line is obtained by the least square method. The value of this slope was defined as the Unelli index.

[0052]

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

Example 1, Comparative Example 1 A PET raw material containing predetermined particles was prepared by the following method.

Raw Materials 1 and 2 In an ethylene glycol slurry containing (or not containing) a predetermined amount of polydivinylbenzene particles having a predetermined average particle diameter, glass beads having a diameter of 50 μm are dispersed as a medium, and the glass beads are dispersed. After the removal, it was subjected to an exchange reaction with dimethyl terephthalate to carry out polycondensation (polymerization catalyst: magnesium acetate 0.10% by weight, germanium oxide 0.03% by weight, trimethyl phosphate 0.026% by weight). The particles were prepared as follows by changing the particle formulation. The intrinsic viscosity (IV) of each raw material was set to a predetermined value by adjusting the polymerization time.

Material 1: No particles Material 2: 1.0% polydivinylbenzene particles having an average particle size of 0.2 μm

The master pellet of the raw material 2 was diluted with a master pellet of the raw material 1 containing no particles at a predetermined ratio, and each was adjusted to a predetermined particle concentration.
After drying under reduced pressure (400 Pa) at 80 ° C. for 8 hours, it was supplied to an extruder and melted at 280 ° C. After filtering this polymer using a high-precision filter, a molten sheet is extruded from a T-die die, and a surface temperature of 2 is applied using an electrostatic application casting method.
The film was wound around a casting drum at 5 ° C., cooled and solidified to form an unstretched film. At this time, the ratio of the die slit gap / the thickness of the unstretched film was set to 10. The discharge amount of the extruder was adjusted to adjust the total thickness.

This unstretched film was stretched 3.4 times in the longitudinal direction at a temperature of 110 ° C. This stretching was performed in two stages. Immediately before this first-stage stretching, 120
Preheating was performed at 3 ° C. for 3 seconds (this operation was not performed in Comparative Example 1). This uniaxially stretched film was stretched 4.0 times in the width direction at 100 ° C. using a stenter (the same as in Example 1 and Comparative Example 1). This film was heat-treated at 140 ° C. for 5 seconds under a constant length. Further, the film was stretched 1.3 times in the transverse direction at 120 ° C. using a stenter.
Heat treatment was performed at 30 ° C. for 2 seconds, and the heat treatment was performed while relaxing 5% in the width direction (120 in Comparative Example 1).
The film was stretched 1.25 times in the transverse direction at a temperature of 190 ° C., heat-treated at 190 ° C. for 2 seconds, and did not relax in the width direction.) Through these operations, films having the physical properties shown in Tables 1 and 2 were obtained.

Examples 2 to 4, Comparative Example 2 (Laminated film) The intrinsic viscosities of the polymers of the raw materials 1 and 2 were adjusted to predetermined values, and the concentration of particles contained in each layer was adjusted to a predetermined value. Raw materials for the laminated portion (A layer) and the base layer portion (B layer) were prepared. For the layer B, it was standard to use the raw material 1 in which only the intrinsic viscosity was adjusted, but in Example 2, the raw material 2 was added so that the particle concentration became 0.05% by weight.

These master pellets are each adjusted to a predetermined viscosity, dried under reduced pressure (400 Pa) at 180 ° C. for 8 hours, and then the extruder 1 is supplied with a raw material for layer A. The raw material particles for layer B were supplied to No. 2 and melted at 280 ° C. respectively. After filtering this polymer using a high-precision filter, it is laminated by a two-layer or three-layer merging block having a rectangular laminated portion, a molten sheet is extruded from a T-die die, and the surface is applied using an electrostatic application casting method. Temperature 2
The film was wound around a casting drum at 5 ° C., cooled and solidified to form an unstretched film. At this time, the ratio of the die slit gap / the thickness of the unstretched film was set to 10. The discharge amount of the extruder was adjusted to adjust the total thickness and the thickness of the laminated portion.

Thereafter, a film was formed in the same manner as in Comparative Example 1.

The properties of the biaxially oriented polyethylene terephthalate film and the magnetic tape using the film are as shown in Table 2, and the films belonging to the scope of the present invention are compared with the films outside the scope of the present invention. The magnetic tape had good slit properties and output characteristics.

[0062]

[Table 1]

[Table 2]

In Table 2, the A-layer surface undulation index was measured on the side on which the magnetic layer was applied.

[0064]

The biaxially oriented polyethylene terephthalate film of the present invention has an increased elastic modulus in the width direction, and has a surface roughness,
Since the surface undulation and high edge index were within the appropriate range,
It was possible to provide a polyethylene terephthalate film capable of obtaining a high output as a magnetic tape without causing a high edge when cutting the tape.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 9:00

Claims (6)

[Claims] 1. A high edge index when cut in the longitudinal direction is 20% or less, and an elastic modulus ETD (G
Pa) is 6.0 or more and the elastic modulus EMD (GP
a) is 4.0 GPa or more, the center line surface roughness of at least one film surface is 10 nm or less, and the undulation index is 10 or less, a biaxially oriented polyethylene terephthalate film. 2. A laminated film of at least two layers, wherein the laminated thickness of the outermost layer on at least one side is 20% or less of the whole film, and the intrinsic viscosity (IV) of polyethylene terephthalate constituting the outermost layer is 0.55dl
/ G or less, the outermost layer contains no particles,
2. The biaxially oriented polyethylene terephthalate film according to claim 1, wherein at least 0.3% by weight of inert particles having an average particle size of 0.3 μm or less is contained. 3. The tear propagation resistance in the longitudinal direction is 1000 N /
2. The biaxially oriented polyethylene terephthalate film according to claim 1, wherein tan δ in the width direction is 0.010 or less. 4. The biaxially oriented polyethylene terephthalate film according to claim 1, wherein the thickness of the entire film is 10 μm or less. 5. The thickness of the entire film is 4 μm or more and 7 μm.
The biaxially oriented polyethylene terephthalate film according to any one of claims 1 to 3, wherein: 6. The biaxially oriented polyethylene terephthalate film according to claim 1, which is used for a magnetic recording medium.