JPH07331041A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a polyester film excellent in surface evenness, sliding property, abrasion resistance and rolling characteristic and suitably usable for magnetic recording mediums. CONSTITUTION:This polyester film contains 0.01-2.0wt.% of organic polymer particles A having >=0.01mum, <0.6mum average particle diameter and 1.0-1.5 particle diameter ratio (long diameter/short diameter) and 0.005-2.0 pts.wt. of organic polymer particles B having a particle diameter which is >=0.05mum larger than that of the organic polymer particle A, >=0.1mum and having <0.6mum average particle diameter and 1.0-1.5 particle diameter ratio and existing in an amount equivalent to or not larger than that of the organic polymer particles A.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film. More specifically, the present invention relates to a polyester film containing two types of organic polymer particles having different average particle diameters and having excellent flatness, slipperiness, abrasion resistance and winding properties.

[0002]

2. Description of the Related Art Due to its excellent properties, polyester film is widely used in many applications such as magnetic tape, electrical insulation, photography, metallization, and packaging. . Especially, polyethylene terephthalate film and polyethylene-2,6-naphthalate film have flatness,
It has excellent mechanical strength, chemical properties, dimensional stability, etc.,
It is preferably used as a base film for magnetic recording media.

On the other hand, with the recent development of magnetic recording media, the characteristics required for the base film have become increasingly severe.

For example, in order to increase the density of a video tape, the flatness of the surface of the base film is required. However, when the surface becomes flat, friction and wear on the surface increase, which causes many problems such as scratches on the film surface and generation of shavings. Here, if the base film has low abrasion resistance, a large amount of film abrasion powder is generated during the magnetic tape manufacturing process, resulting in coating omission during the magnetic layer application process, resulting in magnetic recording omission (dropout). . In addition, when using a magnetic tape, in most cases, it travels while contacting the recording / playback area, so the shavings generated during contact adhere to the magnetic material, resulting in dropout of magnetic recording during recording / playback. Cause

That is, the base film is required to have slipperiness and abrasion resistance both during the magnetic tape manufacturing process and when used as a magnetic tape.

As a method for improving the abrasion resistance, a so-called back coat method, in which an appropriate coating is provided on the side opposite to the magnetic layer, is effective, but there is a problem that the cost is remarkably increased.

Regarding the improvement of wear resistance, JP-A-63-2
No. 35340 and the like propose a method of using spherical silica particles in combination, and JP-A No. 61-177227 and the like propose a method of using silica or titanium oxide particles and calcium carbonate particles in combination. Even if a plurality of the above are combined, there are problems that the affinity between the particles and the polyester is insufficient, and that the particles are so hard that a slight abrasion powder significantly damages the film surface. With respect to the problems of these inorganic particles, JP-A-1-306459 and JP-A-3-221556 have proposed a method of using two kinds of crosslinked polymer particles in combination. Although abrasion resistance is somewhat improved by using particles as compared with inorganic particles, it was insufficient for the high abrasion resistance demanded in recent years.

In addition to the slipperiness, the flatness of the surface, and the abrasion resistance, the base film is required to have excellent so-called winding characteristics (small deviation of the end face of the film roll) suitable for handling in the manufacturing process. Furthermore, as typified by the higher density of magnetic recording media, it has been considered to make the base film thinner, and as a result, there is an increasing demand for a higher elastic modulus that can maintain sufficient stiffness even when the film becomes thinner. ing.

[0009]

[Problems to be Solved by the Invention]
By carefully studying the problems and using two types of organic polymer particles having different average particle sizes together and specifying the difference in particle size and content difference between them, slipperiness, flatness, wear resistance and It has been found that a polyester film is obtained which exhibits good winding properties. The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art.

[0010]

The object of the present invention is that "an organic compound having an average particle size of 0.01 μm or more and less than 0.6 μm and a particle size ratio (major axis / minor axis) of 1.0 to 1.5. The polymer particles A are contained in an amount of 0.01 to 2.0% by weight, and the average particle diameter is 0.05 μm or more larger than that of the organic polymer particles A, the average particle diameter is 0.1 μm or more and less than 0.6 μm, and the particle diameter ratio. Is 1.0
The organic polymer particles B having a particle size of about 1.5 to 0.005 to 2.0
It is achieved by the "polyester film" characterized in that it is contained in an amount of the same as or smaller than the organic polymer particle A within the range of wt%.

The polyester in the present invention may be any one as long as it can form a film, for example, polyethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-1. , 2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and the like,
Polyethylene terephthalate or polyethylene-
2,6-naphthalate is preferable, and polyethylene-2,6-naphthalate is particularly preferable when high elastic modulus is required.

These polyesters include dicarboxylic acids such as adipic acid, isophthalic acid, sebacic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid and their ester-forming derivatives, polyethylene glycol, diethylene glycol, and hexa as copolymerization components. Dioxy compounds such as methylene glycol, neopentyl glycol and polypropylene glycol, oxycarboxylic acids such as p- (β-oxyethoxy) benzoic acid and ester-forming derivatives thereof may be copolymerized.

The organic polymer particles in the present invention are not particularly limited, and any particles may be used as long as at least a part thereof is insoluble in polyester. As materials for such particles, various materials such as polyimide, polyamideimide, polymethylmethacrylate, formaldehyde resin, phenol resin, polystyrene, and polysilsesquioxane so-called silicone resin can be used, but they have high heat resistance. In addition, vinyl-based crosslinked polymer particles are particularly preferred because particles having a uniform particle size distribution can be easily obtained.

The vinyl-based crosslinked polymer particles are monovinyl compounds (A) having only one aliphatic unsaturated bond in the molecule.
And a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking component.

Examples of the compound (A) in the above copolymer include aromatic monovinyl compounds such as styrene, α-methylstyrene, fluorostyrene, vinylpyrine and ethylvinylbenzene, and vinyl cyanide compounds such as acrylonitrile and methacrylonitrile. Acrylic ester monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, hexadecyl acrylate, octyl acrylate, dodecyl acrylate, hexadecyl acrylate, glycidyl acrylate, N, N′-dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate , Isopropyl methacrylate, butyl methacrylate, sec-butyl methacrylate, acrylic methacrylate, phenyl Methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-
Methacrylic ester monomers such as hydroxyethyl methacrylate, glycyl methacrylate, N, N'-dimethylaminoethyl methacrylate, etc., acid anhydrides of mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc. Amide-based monomers such as acrylamide, acrylamide and methacrylamide can be used.

As the compound (A), styrene, ethylvinylbenzene, methylmethacrylate, etc. are preferably used.

Examples of the compound (B) include a divinylbenzene compound, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
Alternatively, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol diacrylate,
Included are polyvalent acrylates and methacrylates such as 1,3-butylene glycol dimethacrylate.

Of the compounds (B), divinylbenzene, ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate is particularly preferably used.

Preferred examples of the composition of the vinyl crosslinked polymer particles include divinylbenzene polymer, ethylvinylbenzene-divinylbenzene copolymer, styrene-divinylbenzene copolymer, styrene-ethylvinylbenzene-divinylbenzene copolymer. Examples thereof include polymers, ethylene glycol dimethacrylate polymers, styrene-ethylene glycol dimethacrylate copolymers, methyl methacrylate-divinylbenzene copolymers and the like. However, the present invention is not limited to these examples, and for example, 3
It may be a copolymer system of more than components.

Such vinyl polymer particles can be produced, for example, by mixing the compounds (A) and (B) and subjecting them to emulsion polymerization as follows. (A) Soap-free polymerization method, that is, a method in which an emulsifier is not used or an extremely small amount of emulsifier is used for polymerization. (B) A seed polymerization method in which polymer particles are added to the polymerization system prior to emulsion polymerization and emulsion polymerization is performed. (C) A core-shell polymerization method in which a part of the monomer components is emulsion-polymerized and the remaining monomers are polymerized in the polymerization system. (D) A polymerization method using Eugelstat or the like disclosed in JP-A-54-97582. (E) A polymerization method in which a swelling aid is not used in the method (d).

The organic polymer particles of the present invention have a thermal decomposition temperature measured by a thermobalance (10% reduction temperature, nitrogen flow, temperature rising rate 1).
Particles having a heat resistance of 0 ° C / min) of 350 ° C or higher are agglomerated during production of the polyester composition, melt molding, or recovery / reuse of the molded product, and the film surface uniformity and abrasion resistance are excluded. It is preferable in that it does not
More preferably 360 ° C. or higher, and particularly preferably 370
℃ or above.

The organic polymer particles according to the present invention have a degree of cross-linking defined by the formula (1) of 10% by weight or more based on the total organic components constituting the particles. Is preferable, and more preferably 40% by weight or more, and particularly preferably 50% by weight or more.

Degree of cross-linking = (weight of cross-linking component in raw material monomer) / (total weight of raw material monomer) × 100 (%) (1) When the organic polymer particles of the present invention are deformed by 10% Strength (hereinafter referred to as S ₁₀ ) is 1 kgf / mm ² or more 15
When it is not more than kgf / mm ² , abrasion resistance is better and it is preferable. Furthermore, 2 kgf / mm ² or more 10 kgf /
mm ² or less, particularly 3 kgf / mm ² or more and 10 kgf /
mm ² or less is preferable.

The organic polymer particles in the present invention are required to have a particle size ratio R (major axis / minor axis) of 1.0 to 1.5 from the viewpoint of slipperiness when formed into a film. The particle size ratio R is preferably 1.0 to 1.3, more preferably 1.0 to 1.1.

In the present invention, it is necessary to use two kinds of organic polymer particles having different average particle diameters. Good slidability can be obtained with only one of the particles, but good film winding characteristics cannot be obtained. However, if particles with different particle diameters are used together here, although the reason is not clear, a slightly large protrusion is formed on a part of the film surface protrusions, and it becomes easy to eliminate air between the films when the films are stacked. Therefore, it is considered that the film winding is stable.

In the present invention, the organic polymer particles B must be larger than the average particle diameter of the organic polymer particles A by 0.05 μm or more. If the difference in particle size is less than 0.05 μm, the end faces of the film tend to be misaligned when the film is wound, and the film winding appearance is deteriorated. Organic polymer particles B
Is 0.1 μm or more than the average particle diameter of the organic polymer particles A,
In particular, it is preferably 0.15 μm or more.

The average particle size of the organic polymer particles A in the present invention is 0.01 μm or more and less than 0.6 μm. It is more preferably 0.05 μm or more and less than 0.5 μm, and particularly preferably 0.1 μm or more and less than 0.5 μm. If the average particle size of the organic polymer particles A is less than 0.01 μm, the slipperiness of the film is insufficient, and if it is 0.6 μm or more, the abrasion resistance is insufficient.

The average particle size of the organic polymer particles B in the present invention is 0.1 μm or more and less than 0.6 μm. More preferably 0.2 μm or more and less than 0.6 μm, especially 0.3 μm
m or more and less than 0.6 μm. If the average particle size of the organic polymer particles B is less than 0.1 μm, the slipperiness of the film becomes insufficient, and if it is 0.6 μm or more, the abrasion resistance becomes insufficient.

If the organic polymer particles in the present invention have a uniform particle size distribution, projections are formed more uniformly on the film surface and less coarse particles are mixed in, so that the slipperiness and abrasion resistance are better. Become. Specifically, the relative standard deviation of the particle size distribution of the organic polymer particles A and / or B is preferably 0.5 or less, more preferably 0.
It is preferably 3 or less, and particularly preferably 0.15 or less.

The content of the organic polymer particles A in the present invention is 0.01 to 2.0% by weight, preferably 0.05 to 2.0% by weight, and particularly 0.1% by weight based on the polyester film. ~ 0.5% by weight. If the content is less than 0.01% by weight, the slipperiness of the film is insufficient, and if it exceeds 2.0% by weight, the abrasion resistance becomes insufficient, which is not preferable.

The amount of the organic polymer particles B used in the present invention is 0.005 to 2.0 with respect to the polyester film.
% By weight, preferably 0.01 to 1.5% by weight, in particular 0.02 to 0.5% by weight. 0.00 0.00
If it is less than 5% by weight, the slipperiness of the film is not sufficient.
If it exceeds 0% by weight, abrasion resistance becomes insufficient, which is not preferable.

The amount of the organic polymer particles B added is not more than the amount of the organic polymer particles A added. Above all, the addition amount of the organic polymer particles A is preferably 0.01% by weight or more, and more preferably 0.03% by weight or more.

The polyester film of the present invention can be produced from the polyester containing the organic polymer particles of the present invention. The polyester containing the organic polymer particles can be produced by a conventional polyester production method such as a transesterification method. The method of adding organic polymer particles in the form of powder or glycol slurry at any time during the transesterification reaction or the polymerization reaction in the case of, or in the case of the direct polymerization method, the powder or low It is possible to employ a method in which the polyester is kneaded in the form of a slurry using a boiling solvent. Especially water of particles and /
Alternatively, a method of kneading into the polyester in the form of an organic compound slurry having a boiling point of 200 ° C. or lower is preferable because the dispersibility of particles is good. In this case, it is more preferable to use a vent type molding machine for degassing.

At this time, it is preferable to add a known surfactant or water-soluble polymer to the organic polymer particle slurry, because the particle dispersibility in the slurry and the particle dispersibility in a polyester film are improved.

In the polyester film of the present invention, in addition to organic polymer particles, inorganic particles such as silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, zirconium oxide, etc., or alkali metal It may contain particles precipitated in a polyester polymerization reaction system containing at least one alkaline earth metal and phosphorus as a part of its constituents, that is, particles such as internal particles.

As a method for producing a polyester film containing inorganic particles or internal particles and the organic polymer particles of the present invention at the same time, for example, a polyester composition obtained by adding both of them to a polyester reaction system is formed into a film. Alternatively, master chips separately blended with the polymer may be blended before or during film formation and melt-kneaded.

The polyester film of the present invention comprises a single layer,
Although it can be applied to both laminated films, a film obtained by laminating at least one layer of the polyester film of the present invention is preferable from the viewpoint of surface flatness. It is more preferable that the laminated film has a structure of three or more layers, and it is particularly preferable that the polyester film of the present invention is at least one outermost layer of the laminated film having a three-layer structure.

From the viewpoint of abrasion resistance, it is particularly preferable that the polyester film of the present invention is arranged in the outermost layer, and the relationship between the film layer thickness t and the average particle diameter DA of the organic polymer particles A is 0.2DA ≦ t ≦ 10DA, preferably 0.5DA ≦ t ≦ 5DA, particularly preferably 0.5
In the case of DA ≦ t ≦ 3DA, the thickness of the outermost layer is preferably 0.005 to 1 μm, more preferably 0.01 to 0.5 μm, and particularly 0.02 to 0.3 μm.
m is preferred.

Further, from the viewpoint of abrasion resistance, this polyester film has a number of projections on at least one side of 2 × 10 ³ to.
It is preferably 5 × 10 ⁵ pieces / mm ² . 3 × 10 ³ to 4 × 10 ⁵ pieces / mm ² , preferably 5 × 10 3
^{3 to} 3 × 10 ⁵ pieces / mm ² is preferable.

Next, the method for producing the polyester film of the present invention will be described by taking the case of a laminated film as an example.

The organic polymer particles in the present invention and, if necessary, pellets containing a predetermined amount of other particles are dried and then fed to a known melt extruder, extruded into a sheet form from a slit die, and a casting roll. The above film is cooled and solidified to prepare an unstretched film. In the case of a laminated film, two or more extruders, two or more layers of manifolds or merging blocks are used to laminate polyester in a molten state. In this case, a method of installing a static mixer or a gear pump in the flow path containing the particles may be used.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a 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 is first performed in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more steps, and the longitudinal stretching temperature is 80 ° C to 160 ° C and the total longitudinal stretching ratio is 3. 0-7.0
The double and longitudinal stretching speeds are preferably in the range of 5,000 to 50,000% / min. As a stretching method in the width direction, a method using a stenter is preferable, the stretching temperature is 80 to 160 ° C., the stretching ratio in the width direction is 3.0 to 7.0 times larger than the longitudinal ratio, and the stretching speed in the width direction is 1000 to 20000%. The range of / minute is preferred.

Next, this stretched film is heat-treated. In this case, the heat treatment temperature is 170 to 220 ° C. and the time is 0.5 to
A range of 60 seconds is preferred.

[0044]

EXAMPLES The present invention will be described in detail below with reference to examples. The characteristic values of the obtained film were determined according to the following methods.

(1) Average particle size Basically, particles in a polyester film are directly measured, but when the refractive index of the particles and the polymer are close to each other and it is difficult to observe, or when inorganic particles are used in combination and discrimination becomes complicated. For example, it was determined from powder or slurry before being added to polyester.

(A) When measuring from powder or slurry Place the particles on the sample stage of an electron microscope so that the particles do not overlap each other, and use a scanning electron microscope or a transmission electron microscope to
The particles were observed at a magnification of 10,000 to 100,000 times. In the case of a scanning electron microscope, a platinum vapor deposition film having a layer thickness of about 200 angstrom was previously formed on the sample surface by a sputtering device. The major axis, minor axis, and area equivalent diameter of at least 200 particles are measured from a screen or a photographic image, and based on the volume of each particle calculated from the number average value of the particle size ratio and the area equivalent diameter, a volume-based The average particle size was calculated.

(B) When measuring from the film The film is cut in the longitudinal direction (MD direction) at the time of film formation to prepare an ultrathin section having a thickness of about 0.1 μm, and the TD direction (perpendicular to MD in the film plane) Section) was observed with a transmission electron microscope at a magnification of 10,000 to 100,000 times. From the screen or photographic image, the major axis of at least 200 particles,
The minor axis and the area-equivalent diameter were measured, and the volume-based average particle diameter was calculated based on the volume of individual particles calculated from the number average value of particle diameter ratios and the area-equivalent diameter.

(2) Content of particles Particles obtained by calculating from the content of particles in polyester as a film raw material, or by dissolving the obtained film in a solvent in which the particles are insoluble and centrifuging from a polymer. The ratio (% by weight) to the total film weight was defined as the particle content.

(3) Lamination Thickness of Laminated Film Using a secondary ion mass spectrometer (SIMS), the element and the polyester derived from the highest concentration of particles in the film in the depth range of 3000 nm from the surface layer The concentration ratio (M ⁺ / C ⁻ ) of the carbon element is used as the particle concentration, and analysis is performed in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration becomes ½ of the maximum value (this depth is deeper than the maximum value) was determined and used as the laminated thickness. The conditions are as follows.

Measuring device Secondary ion quality analyzer (SIMS) Germany, ATOMIKA
Co., Ltd. A-DIDA3000 measurement conditions primary ion species O ₂ ⁺ primary ion acceleration voltage 12 kV primary ion current 200 nA raster region 400 μm □ analysis region gate 30% measurement vacuum level 6.0 × 10 ⁻⁹ Torr E-GUN 0. 5kV-3.0A In addition, when the particles contained most in the depth range of 3000 nm from the surface layer are organic polymer particles, it is difficult to measure by SIMS, so XPS (X
The depth profile may be measured by line photoelectron spectroscopy, IR (infrared spectroscopy), etc. to determine the layer thickness, or the cross-sectional observation with an electron microscope or the like may reveal changes in particle concentration or differences in polymers. It is also possible to recognize the interface from the difference in contrast due to and obtain the laminated thickness. Further, after peeling the laminated polymer, the laminated thickness can be obtained by using a thin film step measuring device.

(4) Flatness of film surface The film was measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The center line average roughness (Ra) and the maximum height (Rt; the distance between the maximum peak and the deepest valley of the roughness curve) were measured. The measurement conditions are as follows, and the average value of 20 measurements was taken as the value. Rt / Ra is an index of the flatness of the film surface, and Rt / Ra of 15 or less indicates good surface flatness.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cut-off value: 0.08 mm For details of the definition of each parameter, see Jiro Nara "Measurement of surface roughness- Evaluation method "(General Technology Center, 1
983).

(5) Sliding property of film Slitted film having a width of 1/2 inch, tape running tester TBT-300 type [manufactured by Yokohama System Laboratory Co., Ltd.]
Was run at 20 ° C. and 60% RH, and the initial friction coefficient μk was determined by the following formula. The guide diameter is 6
mmφ, the guide material is SUS27 (surface roughness 0.
2S), winding angle is 180 °, traveling speed is 3.3 cm
/ Sec. μk = 0.733 × log (T ₁ / T ₂ ) T ₁ : Outlet tension T ₂ : Inlet tension The above μk is 0.35 or less has good slipperiness.

(6) Abrasion resistance of film A tape-shaped roll obtained by slitting the film into 1/2 inch is wound around a guide roll made of stainless steel SUS-304 at an angle of 60 °, a speed of 250 m / min, and a tension of 95 g.
It was rubbed over 00 m and ranked as follows according to the amount of white powder generated on the surface of the guide roll. Grades A and B were accepted. Class A: No white powder is generated B Class: White powder is slightly generated C Class: White powder is slightly large D Class: White powder is large

(7) Winding characteristics The film was wound around a roll having a width of 1000 mm and a length of 18000 m at a winding speed of 300 m / min, and an end surface deviation (a deviation distance in the width direction) and vertical wrinkles of the wound roll were generated. The condition was inspected and judged as follows. Class A: End surface misalignment of less than 0.5 mm, no vertical wrinkles Class B: End surface misalignment of less than 0.5 mm immediately after winding the roll, no vertical wrinkles, but with visible vertical wrinkles after standing for 24 hours C Grade: The end face shift was 0.5 mm or more, or vertical wrinkles were visually observed immediately after winding the roll. Grades A and B were accepted.

Example 1 Polyethylene terephthalate chips having an intrinsic viscosity of 0.65 were melted using a vent type twin-screw extruder, and ethyl vinylbenzene-divinylbenzene copolymer particles were used as organic polymer particles A. , Average particle size 0.4 μm, relative standard deviation 0.12 of particle size distribution, particle size ratio 1.0, water slurry having a thermal decomposition temperature of 380 ° C. and ethyl vinylbenzene-divinylbenzene copolymer as organic polymer particles B Particles, average particle size 0.5 μm, relative standard deviation of particle size distribution 0.15, particle size ratio 1.0, thermal decomposition temperature 37
A 0 ° C. water slurry was added to obtain polyethylene terephthalate (I) containing two kinds of organic polymer particles. on the other hand,
Polyethylene terephthalate (II) containing no particles and having an intrinsic viscosity of 0.65 was obtained by a known method.

After drying the two polymers (I) and (II) under reduced pressure, the polymer (I) was added to the extruder 1 and the extruder 2.
After supplying (II), melting and high-precision filtration,
Three layers were laminated at the rectangular confluence (lamination structure: polymer (I) / polymer (II) / polymer (I)).

This was wound around a casting drum by an electrostatically applied casting method and cooled and solidified to prepare an unstretched film. This unstretched film is lengthwise 3.5.
Stretched 5.5 times in the width direction, heat treated, total thickness 15 μm
A biaxially oriented laminated film of was obtained.

From the particle concentration of the pellets used for film formation, the organic polymer particles contained in the laminated portion of the obtained film were 0.3% by weight of particle A and 0.05% by weight of particle B. It was The particles observed by using the obtained section of the film maintained the spherical shape, and no change was observed in the particle size ratio.
The laminated thickness was 1 μm in both laminated parts.

This film has Rt / Ra of 8, μk of 0.30, wear resistance of A class, and winding property of A class, and has good surface flatness, slipperiness, wear resistance and winding property. Various characteristics were obtained.

Examples 2 to 4 and Comparative Examples 1 to 4 In the same manner as in Example 1, the composition of the organic polymer particles contained, the particle size, the content, the laminating conditions or the matrix polymer was polyethylene-2,6-. A film was prepared in the same manner except that it was changed to naphthalate. As shown in Table 1, the polyester film in the range specified in the present invention has good surface flatness, slipperiness, abrasion resistance, and winding property. It was insufficient.

[0061]

[Table 1]

[0062]

The polyester film of the present invention contains two kinds of crosslinked organic polymer particles, is excellent in surface flatness, slipperiness, abrasion resistance and winding property, and can be suitably used for magnetic recording medium applications and the like. .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 67:00 B29L 9:00

Claims (4)

[Claims] 1. An average particle diameter of 0.01 μm or more and 0.6 μm
and the particle size ratio (major axis / minor axis) is 1.0 to 1.5.
0.01 to 2.0% by weight of the organic polymer particles A having an average particle diameter of 0.05 μm from the organic polymer particles A.
m or more, average particle size is 0.1 μm or more and 0.6 μm
Polymer particles B having a particle size ratio of less than 1.0
In the range of 0.005 to 2.0% by weight and the same as or smaller than the amount of the organic polymer particles A. 2. The polyester film according to claim 1, wherein the relative standard deviation of the average particle diameters of the organic polymer particles A and / or the organic polymer particles B is 0.5 or less. 3. A laminated polyester film comprising at least one layer of the polyester film according to claim 1 or 2. 4. The polyester is polyethylene-2,6-
It is a naphthalate, The polyester film of any one of Claims 1-3 characterized by the above-mentioned.