JP3257242B2 - Biaxially oriented laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film.

[0002]

2. Description of the Related Art As a polyester film, a film containing inert particles such as calcium carbonate and colloidal silica for forming projections on the film surface in order to improve film processability and running properties is known. (For example, JP-A-59-171623).

[0003]

However, especially when a polyester film is used for a magnetic recording medium,
The drawback that the polyester film surface, especially the film surface with fine projections, is scraped or scratched by the contacting rolls, etc. due to the increase of the process speed in the magnetic material coating / calendering process etc. in the magnetic recording medium manufacturing process Has recently become a problem. Further, at the stage of slitting and processing into a video tape after applying the magnetic material, there is a problem that chips are generated on the cut surface of the film and adhere to the magnetic surface to deteriorate the image. Also, in the conventional one,
With the increase in dubbing speed such as high-speed magnetic transfer, the image quality, that is, the S / N (signal / noise ratio) is insufficient due to the decrease in image quality during dubbing. In order to solve these drawbacks, for example, a method of controlling the variation in the shape and particle size of the particles to be contained (for example, JP-A No.
No. 9033) has been tried, but the effect is insufficient, and it has not been able to satisfy recent quality requirements.

Further, an example of a monolayer film containing a germanium catalyst (for example, JP-A-60-85925) is disclosed, but sufficient quality has not been obtained.

The present invention solves such a problem, and in particular, in a high-speed process, the film surface is hardly scraped or scratched (hereinafter referred to as scratch resistance), and when the film is cut and processed, Magnets with excellent surface characteristics with less generation of cuttings on the cut surface (hereinafter referred to as slit characteristics) and less deterioration in image quality during high-speed dubbing, that is, good electromagnetic conversion characteristics (hereinafter referred to as excellent electromagnetic conversion characteristics) An object of the present invention is to provide a polyester film for a recording medium.

[0006]

That is, according to the present invention, at least one layer contains antimony (Sb) and germanium (Ge), and the content (Sb + Ge) is 1%.
It consists of a biaxially oriented laminated polyester film having a content ratio (Ge / Sb) in the range of 0.001 to 0.5 at 0 to 400 ppm.

The polyester constituting the present invention is polyethylene terephthalate, polyethylene 2,6-naphthalate or the like, and the polyester may be a homopolyester or a copolyester. Examples of the copolymerization component include adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, a polycarboxylic acid component such as trimellitic acid, or diethylene glycol, tetramethylene glycol, hexamethylene glycol, Propylene glycol, neopentyl glycol, polyoxyalkyl glycol, p-
Examples include polyhydric alcohol components such as kylene glycol and 1,4-cyclohexyldimethanol. Also,
Any heat stabilizer, modifier, antioxidant, etc. may be included.

Further, its intrinsic viscosity is 0.5 or more, preferably 0.55 or more.

The film of the present invention preferably has a laminated structure of at least three layers. Four or five layers may be used, but a three-layer structure is particularly preferable since the effect of the present invention is further improved. It is effective to improve the slit characteristics by containing substantially a large amount of inert particles in the surface portion. In the case of a single layer, this effect is unfavorably small.

In the film of the present invention, it is necessary that at least one of the layers constituting the film is biaxially oriented. It is particularly preferable that all the layers in the three or more layered structure are biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the effects of the present invention cannot be obtained.

Conventionally, in a method for producing a polyester raw material to be used for a polyester film, antimony oxide, an organotitanium compound and the like, and more particularly germanium oxide and the like for super transparent and particle-free polymer have been used as a polymerization catalyst. As a result of a more detailed analysis of these catalyst-containing elements, a specific amount of both antimony and germanium was contained, and by setting the content ratio of both to a specific range, the film was cut particularly at the cut surface when cutting the film. It has been found that the generation of powder can be suppressed and a polyester film having excellent slit characteristics can be obtained, and the present invention has been accomplished.

In the laminated polyester film of the present invention, at least one layer contains an antimony element (Sb) and a germanium element (Ge) in a total amount of 10 to 400 pp.
m, preferably 20 to 300
ppm, more preferably 30 to 100 ppm. If it is less than 10 ppm, there is no effect of improving the slit characteristics, and if it exceeds 400 ppm, the amount of thermal decomposition due to the contained metal becomes large, which may cause problems such as color tone in the film production process. Further, the content ratio (Ge / Sb)
Is 0.001 to 0.5, preferably 0.002 to
0.3, more preferably 0.005 to 0.2. 0.0
If it is less than 01, the effect of improving the slit characteristics is insufficient, and
If the ratio exceeds the above range, the amount of thermal decomposition of the polymer by germanium increases, and a problem such as white streaks may occur in the film in the film forming process.

Antimony needs to be dissolved or substantially dispersed as fine particles in the polyester. It may be a carboxylate constituting polyester such as antimony oxide, metal antimony, antimony phosphate, terephthalic acid, or the like, or may be residual antimony caused by an antimony compound added as a polymerization catalyst. Furthermore, a method in which antimony oxide, antimony acetate, or the like is added at any stage during the polymerization of the polyester can be preferably employed.

Germanium must be dissolved or contained as fine particles in the polyester. Furthermore, a method of adding germanium oxide, germanium acetate, or the like at an arbitrary stage during the polymerization of the polyester can be preferably employed.

The laminated film of the present invention has a laminated structure of at least three layers, at least one outermost layer containing 0.1 to 1.5% by weight of inert particles, and the average particle size of the particles. The relation between d (μm) and the thickness t (μm) of the outermost layer is 0.2d ≦ t ≦ 10d, and any layer other than the outermost layer contains antimony (Sb) and germanium (Ge). And its content (Sb + Ge) is 10
And the content ratio (Ge / Sb) is 0.1 to 400 ppm.
It is preferably in the range of 001 to 0.5.

The average particle size of the inert particles is preferably 0.1 to 2 μm, and more preferably 0.2 to 1.2% by weight of the inert particles having an average particle size of 0.2 to 1 μm. When the average particle size is 0.1 μm or less and the content is 0.1% by weight or less, it is insufficient to obtain sufficient running characteristics, and when the average particle size is 2 μm or more and the content is 1.5% by weight or more, it is good. In some cases, it may not be possible to obtain excellent electromagnetic conversion characteristics. Furthermore, t is 0.2
If it is smaller than d, the runnability deteriorates, and if t is larger than 10d, the electromagnetic conversion characteristics of a magnetic tape may be reduced.

Here, the inert particles need not be one kind, and may be a mixed system of two or more kinds of inert particles.
Further, it is preferable that the inert particles contained have a uniform particle size, and it is particularly preferable not to include coarse particles because the electromagnetic conversion characteristics and scratch resistance are further improved. If necessary, a method such as a dispersion treatment using a sand grinder, a classification treatment such as a centrifugal sedimentation treatment, and a filtration method are used. The type of the inert particles is not particularly limited, but in order to satisfy the above preferable particle characteristics,
Particles such as calcium carbonate, colloidal silica, fine organic polymer particles, alumina, and titanium oxide are used. Calcium carbonate is preferably produced by a synthesis method and has a uniform particle size distribution, and colloidal silica is preferably spherical silica particles produced by an alkoxide method, a water glass method or the like, having a uniform particle size distribution. Examples of the organic polymer fine particles include particles insoluble in polyester such as polystyrene, crosslinked polystyrene, styrene / acrylic crosslinked particles, and silicone particles. Preferably, crosslinked fine particles such as butyl acrylate-divinylbenzene copolymer, ethylbenzene-divinylbenzene copolymer, 2-ethylhexyl acrylate-ethylene glycol dimethacrylate copolymer, and the like, and copolymers of further components It may be. Further, as for the heat resistance, it is preferable that the thermal decomposition temperature (10% weight loss) by a thermobalance is 350 ° C. or more.

Particularly, when these organic polymer fine particles and calcium carbonate are contained alone or in combination, a good effect can be obtained. Although the effects of the present invention can be exhibited, when calcium carbonate or organic polymer fine particles are used as at least a part of the inactive particles, a favorable effect is particularly obtained on the slit characteristics.

These inert particles can be used by treating or coating the surface of the particles with a surfactant, a polymer compound, or the like. In particular, it is preferably employed for improving the dispersibility in the polymerization process and for improving the affinity with the polyester in the film.

In addition, as long as the effects of the present invention are not impaired, there is no problem even if precipitated internal particles containing calcium and lithium elements are used in combination.

In the laminated film of the present invention, a coating layer of an antistatic agent or the like may be provided on at least one surface for improving adhesion to a magnetic agent and preventing static charge.

The center line average surface roughness Ra of the film surface is preferably 5 to 50 nm in order to make the film surface roughness appropriate for obtaining sufficient running properties as a magnetic recording medium. More preferably 8 to 30 nm, even more preferably 1 to 30 nm.
0 to 25 nm.

Further, the polyester of the base layer portion may be a polyester substantially containing no particles, or may contain particles. The particle type is not particularly limited.For example, fine particles insoluble in polyester such as calcium carbonate, silica, kaolin, alumina, barium sulfate, and titanium oxide may be used as inorganic particles, or organic particles such as cross-linked polystyrene. May be contained, or internal particles containing calcium or lithium may be contained.

Further, it is desirable that the particles contained in the base layer polyester do not substantially hinder the formation of the surface formed by the laminated portion, and the maximum particle size of the contained particles is at least 2 times the maximum particle size contained in the laminated portion. It is preferably at most 0 times, more preferably at most 1.5 times. If it exceeds 2.0 times, the influence of the particles in the base layer cannot be concealed by the laminated portion, which may cause the formation of coarse projections. Further, the base layer polyester may contain a recovered raw material mainly composed of a non-product portion generated in the production stage of the laminated film or another type.

Next, a method for producing the film of the present invention will be described. First, as a method for incorporating particles into the polyester, for example, particles are dispersed in a predetermined ratio in the form of a slurry in ethylene glycol, which is a diol component, and if necessary, dispersion treatment using a sand grinder or the like, classification treatment such as centrifugal sedimentation treatment, or the like. , And a treatment such as filtration. A method of polymerizing the slurry and ethylene glycol with a predetermined dicarboxylic acid component is preferable. Also, a method of directly mixing a water slurry of particles with predetermined polyester pellets, supplying the mixture to a vent-type twin-screw extruder, and kneading the polyester into a polyester is very effective in further improving the effects of the present invention. It is effective to prepare a high-concentration particle master by the above method and dilute it with a polyester substantially free of particles during film formation to adjust the content of the particles.

Next, using the polyester pellets, a polyester film having a laminated structure of three or more layers is formed. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, fed to a known extruder for melt lamination, extruded from a slit die into a sheet, and cooled and solidified on a casting roll. At least make an unstretched film. That is, using two or three or more extruders, three or more manifolds or a merging block (for example, a merging block having a square merging portion), a film layer constituting each outermost layer and a film layer constituting an intermediate layer And extruding two or more sheets from a die and cooling on a casting roll to produce an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer flow path is effective. Further, the melting temperature of the extruder for extruding the polymer on the outermost layer lamination side is 5 to 10 from the base layer.
It is effective to lower the temperature by ° C. to stably laminate.

Next, the unstretched film is biaxially stretched,
Make it biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However,
First, a longitudinal biaxial stretching method in which stretching is performed in the longitudinal direction and then in the width direction is used, the longitudinal stretching is divided into three or more stages, and a total longitudinal stretching ratio of 3.5 to 6.5 times is performed. Particularly preferred. In the longitudinal direction, the stretching temperature varies depending on the type of polyester and cannot be described unconditionally.
It is effective to set the temperature to 30 ° C. and to increase the temperature after the second stage. The longitudinal stretching speed is 5,000 to 50,000% /
A range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The stretching ratio is 3.0 to 3.0.
A range of 5.0 times is appropriate. The stretching speed in the width direction is 1
2,000 to 20,000% / min, and the temperature is preferably in the range of 80 to 160 ° C. Next, this stretched film is heat-treated.
The heat treatment temperature in this case is 170 to 220 ° C., particularly 180
The temperature is preferably in the range of 0.2 to 20 seconds.

The method of measuring and evaluating the characteristic values in the present invention are as follows.

(1) Average particle size of particles The polymer is removed from the film by a plasma low-temperature ashing method to expose the particles. The processing conditions are selected so that the polymer is ashed 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. The magnification of the SEM is about 2000 to 10000 times, and the field of view in one measurement is appropriately selected from about 10 to 50 μm. The volume average diameter d is obtained by the following equation from the particle diameter and its volume fraction when the number of particles is 1000 or more at different observation points. d = Σdi · Nvi where di is the particle diameter and Nvi is its volume fraction. When the particles are organic particles or the like and are significantly damaged by the plasma low-temperature incineration method, the following method may be used.
Using a transmission electron microscope (TEM) on the cross section of the film,
Observe at 000-100,000 times. The thickness of the TEM section is about 1000 Angstroms,
The measurement is performed for zero or more visual fields, and the volume average diameter d is obtained from the above equation.

If necessary, for example, measurement by a scanning microscope for particles before addition at the time of polymerization can also be adopted,
A value measured by a centrifugal sedimentation type particle size distribution analyzer can also be used.

(2) Content of Particles A solvent in which the polyester is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the solvent, and the ratio of the amount of the particles to the total weight (% by weight) is defined as the particle content. . In some cases, combined use of infrared spectroscopy, X-ray fluorescence analysis, etc. is also effective. Further, if necessary, the film is cut with a microtome, measured by a transmission electron microscope, and the ratio of the particle image per unit area is determined, whereby the amount of particles added to the polyester can be calculated.

(3) Lamination Polyester Thickness (Thickness of Outer Layer: t) Using a secondary ion mass spectrometer (SIMS), the particle farm land having the highest concentration in the film ranging from the surface layer to a depth of 3000 nm is used. The concentration ratio (M ⁺ / C ⁺ ) between the element resulting from the particles and the carbon element of the polyester is defined as the particle concentration, and the analysis in the thickness direction is performed from the surface 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 which has once reached the maximum value starts to decrease again.
Based on this concentration distribution curve, the surface particle concentration is 1/1 of the maximum value.
Find the depth that is 2 (this depth is deeper than the maximum value). This was defined as the lamination thickness.

Measurement device Secondary ion mass spectrometer (SIMS) ATOMIK, Germany
A-DIDA3000 manufactured by Company A Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ^{− 9} Torr E-Gun: 0.5 KV-3.0 A In addition, when the particles most contained in the range of 3000 nm in depth from the surface layer are organic polymer particles, it is difficult to measure by SIMS. (X
Line photoelectron spectroscopy), IR (infrared spectroscopy), etc., the same depth profile as above may be measured to determine the lamination thickness, or the change in particle concentration and polymer It is also possible to recognize the interface from the difference in the cotrust due to the difference and determine the lamination thickness. Further, after the laminated polymer is peeled off, the laminated thickness can be obtained by using a thin film step measuring device.

(4) Germanium and antimony contents Measured by atomic absorption spectrometry.

(5) Center line average surface roughness (R)
a) According to JIS-B-0601, the center line average surface roughness (Ra) was measured at a cutoff of 0.25 mm and a measurement length of 4 mm using a stylus type surface roughness meter BE-3E manufactured by Kosaka Laboratory.

(6) Intrinsic viscosity [η] (unit: dl / g) The value calculated from the following formula based on the solution viscosity measured in orthochlorophenol at 25 ° C. is used. 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 (0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(7) Scratch resistance Under an atmosphere of 25 ° C. and a relative humidity of 60%, a tape-shaped film having a 1/2 inch width is fixed on a fixed shaft (external surface roughness: 0.2 S) having an outer diameter of 6 mm at an angle θ = π / 3 rad. 250m /
Drive in minutes. The entrance tension T ₁ 90g
After running for 100 m, the film was subjected to aluminum evaporation, and the number of scratches, the size of the width, and the state of generation of white powder were observed with a differential interference microscope. Those having no scratches and no generation of white powder were evaluated for scratch resistance: 5,
Those having less than 3 scratches / mm and little generation of white powder were evaluated as having scratch resistance of 4, and having 3 to 10 scratches.
Some of them have a large width at a number of lines / mm, and those having a large amount of white powder are evaluated as having a scratch resistance of 3, and those having a large scratch width of 10 lines / mm or more and having a large amount of white powder. Scratch resistance: 2 and more were judged as scratch resistance: 1. If the scratch resistance is 5 or 4, it can be used without practical problems.

(8) Electromagnetic conversion characteristics and slit characteristics A magnetic paint having the following composition is applied to a film by a gravure roll, magnetically oriented, and dried. Furthermore, a small calender (styrene roll / nylon roll, 5
After performing a calendering process at a temperature of 70 ° C. and a linear pressure of 200 kg / cm in (stage), curing is performed at 70 ° C. for 48 hours. The raw material was cut into slits at a speed of 50 m / min to a width of 1/2 inch to prepare a pancake.

(Composition of Magnetic Coating) Co-containing iron oxide (BET value 50 m ² / g): 100 parts by weight Vinyl chloride / vinyl acetate copolymer: 10 parts by weight Polyurethane elastomer: 10 parts by weight Polyisocyanate: 5 parts by weight-Lecithin: 1 part by weight-Methyl ethyl ketone: 75 parts by weight-Methyl isobutyl ketone: 75 parts by weight-Toluene: 75 parts by weight-Carbon black: 2 parts by weight-Lauric acid: 1.5 parts by weight 1 m is collected, wound in a coil form and placed in a clean beaker.
The mixture was treated with 0 KHZ ultrasonic waves for 2 minutes, and the cuttings caused by the cut surface were washed off in pure water. The number of particles having a size of 3 to 20 μm was measured for this pure water using a particle counter (HIAC CL-5, Nozaki Sangyo), and the result was regarded as the number of chips. The number of chips is preferably as small as possible, but if it is 50 pieces / m or less, it can be used without practical problems, and if it is 20 pieces / m or less, it is more preferable, and particularly good dubbing characteristics can be obtained.

Further, the above pancake was used for a length of 250
m was incorporated into a VTR cassette to form a VTR cassette tape. This tape was used for 1 V by a TV test waveform generator (TG7 / U706) made by Shibasoku using a home VTR.
00% chroma signal was recorded, and the reproduced signal was subjected to chroma S / N with a Shibasoku color noise measuring instrument (925D / 1).
Was measured to determine the image quality.

[0041]

【Example】

(1) Production of calcium carbonate-containing master polymer Synthetic calcium carbonates having different average particle diameters were each made into a slurry of 10% by weight of ethylene glycol, subjected to a dispersion treatment for 2 hours by a sand grinder, and further subjected to a centrifugal classification treatment with a super decanter to obtain coarse particles. Was removed. This slurry was subjected to microfiltration using a 2 μm filter to prepare an ethylene glycol slurry of calcium carbonate having few coarse particles and different average particle sizes.

100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.04 of magnesium acetate tetrahydrate
Parts and 0.04 part of antimony oxide were charged into a reactor,
The transesterification was performed while gradually increasing the internal temperature from 145 ° C. When the transesterification rate reached 97%, trimethyl phosphate 0.04 was used as a stabilizer.
Parts and 20 parts of the previously prepared calcium carbonate ethylene glycol slurry were added. Next, the reaction product was transferred to a polymerization reactor, and was heated under a high temperature vacuum (final internal temperature 290).
℃) according to a conventional method to carry out a polycondensation reaction, an intrinsic viscosity of 0.6
2. Polyethylene terephthalate containing 2% by weight of calcium carbonate particles was obtained. In a similar manner, polyethylene terephthalate containing calcium carbonate having different average particle sizes was obtained.

(2) Production of Antimony-Free Particles In the above polymerization method, a transesterification reaction and a polycondensation reaction are carried out without adding an ethylene glycol slurry of the particles, and an intrinsic viscosity substantially containing no inert particles is obtained. 0.62 particle-free polyethylene terephthalate was obtained. The antimony content in this polymer was 310 ppm.

(3) Production of Master Polymer Containing Organic Particles Using a vent type twin screw extruder, the antimony-containing particle-free polyethylene terephthalate was melted,
Divinylbenzene copolymer particles (divinylbenzene 55%, so that the content in the final polymer is 1% by weight)
A water slurry of ethylvinylbenzene (45% copolymer) was added, the vent was maintained at a vacuum of 10 Torr, and the mixture was melt-kneaded and extruded at a polymer temperature of 280 ° C. to obtain polyethylene terephthalate containing divinylbenzene copolymer particles (intrinsic viscosity). 0.615).

(4) Production of particle-free polymer containing germanium 100 parts of dimethyl terephthalate, ethylene glycol 7
0 parts and 0.04 parts of magnesium acetate tetrahydrate were charged into a reactor, and transesterification was carried out while gradually increasing the internal temperature from 145 ° C. When the transesterification rate reached 98%, 0.10 parts of germanium oxide and 0.08 parts of trimethyl phosphate were added. Next, the reaction product was transferred to a polymerization reactor, and was heated under a high temperature vacuum (final internal temperature 2).
A polycondensation reaction was performed at 90 ° C.) according to a conventional method to obtain polyethylene terephthalate containing germanium having an intrinsic viscosity of 0.62. The germanium content in this polymer is 40
It was 3 ppm.

Example 1 The above-prepared char-containing master polymer (0.40 μm) was prepared.
m) and antimony-containing non-particle-containing polymer are mixed to form a raw material for a laminated portion, and further, an antimony-containing non-particle-containing polymer, a germanium-free particle-containing polymer and a recovered polyester raw material resulting from a non-product portion generated in a film manufacturing process are mixed, and a base layer portion is formed. Each of the raw materials was dried at 180 ° C. for 3 hours under reduced pressure (3 Torr).

The base material is supplied to the extruder 1 at 310 ° C.
Further, the raw material for the laminated portion was supplied to the extruder 2 and melted at 280 ° C. These polymers are merged and laminated by a merging block provided with a rectangular laminating section before entering the die, wrapped around a casting drum having a surface temperature of 45 ° C. using an electrostatic application casting method, and cooled and solidified. To form a three-layer unstretched film in which a laminated polyester was laminated. At this time, the discharge amount of each extruder was adjusted, and the total thickness and the lamination thickness were adjusted. 80 ° C.
And stretched 4.5 times in the longitudinal direction. This stretching was performed in two stages with a peripheral speed difference between two sets of rolls. The uniaxially stretched film is stretched using a stenter at a stretching speed of 2,000% / min.
The film was stretched 4.0 times in the width direction at 00 ° C. and heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a laminated biaxially oriented polyethylene terephthalate film. This film had a base layer thickness of 12.0 μm and a lamination of 1.0 μm on both sides thereof by adjusting the discharge rate of each extruder.

As a result of evaluating various physical properties of the film, the film surface roughness was 16 nm. Further, the scratch resistance was 5, the slit characteristic was 22 / m, and the electromagnetic change characteristic was +1.3 dB, which was an extremely good film characteristic.

Examples 2 to 4, Comparative Examples 1 to 3 The master polymer containing calcium carbonate, the master polymer containing organic particles, and the particle-free polymer containing antimony were mixed by changing the type and amount as shown in Table 1, respectively. As shown in Table 1, the particle polymer, the polymer containing no germanium particles, and the recovered polyester raw material resulting from the non-product portion generated in the film manufacturing process were mixed in different types and amounts as shown in Table 1 to obtain a base layer raw material. Table 1 shows each parameter and film quality of the film obtained in the same manner as in Example 1.
As shown in the above, when these are within the range specified in the present invention, good scratch resistance, slit characteristics, electromagnetic conversion characteristics are obtained, otherwise the desired effect is obtained. Did not.

[0050]

[Table 1]

[0051]

Industrial Applicability The biaxially oriented polyester film of the present invention has excellent scratch resistance and slit characteristics, and can provide a biaxially stretched laminated polyester film most suitable for magnetic media, particularly for video tape, and has high quality video. It is possible to provide a tape.

Claims (2)

(57) [Claims] At least one layer is made of antimony (S)
b) and germanium (Ge), the content (Sb + Ge) is 10 to 400 ppm, and the content ratio (Ge / Sb) is in the range of 0.001 to 0.5. Axis oriented laminated polyester film. 2. A layered structure having at least three layers or more, wherein at least one outermost layer on one side contains inert particles in an amount of 0.1 to 2 μm.
1 to 1.5% by weight, and the average particle diameter d (μm) of the particles
And the thickness t (μm) of the outermost layer is 0.2d ≦ t
≦ 10d, and at least one layer other than the outermost layer contains antimony (Sb) and germanium (Ge), and the content (Sb + Ge) is 10 to 400 ppm.
And the content ratio (Ge / Sb) is 0.001 to 0.5
A biaxially oriented laminated polyester film for a magnetic recording medium, wherein