JP3292333B2 - Biaxially oriented 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 biaxially oriented polyester film containing specific silicone particles.

[0002]

2. Description of the Related Art As a biaxially oriented film, for example, a biaxially oriented polyester film, a film in which monodispersed organic particles are contained in polyester is known (for example, JP-A-59-217755).

[0003] However, in the above-mentioned conventional biaxially oriented polyester film, for example, a process of applying a magnetic layer for a magnetic medium, a calendering process, or a process of dubbing a produced video tape or the like to produce a soft tape or the like. However, there is a disadvantage that the film surface is scratched by a contacting roll or guide as the process speed increases. Further, the conventional one has a drawback that the image quality on a video tape, that is, the S / N (signal / noise ratio) is insufficient due to the deterioration of the image quality during dubbing.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. In particular, the film is less likely to be damaged in a high-speed process (hereinafter referred to as "scratch resistance"), and the image quality during dubbing is small (hereinafter referred to as "dubbing resistance"). It is an object of the present invention to provide a biaxially oriented polyester film (having excellent properties).

[0005]

According to the present invention, there is provided a biaxially oriented polyester film having an average particle size defined by the formula (3) of 0.01 to 2 μm and a composition substantially represented by the formula (1). ), Wherein the number of projections on at least one side is 2 × 10 ^{3 to} 5 × 1.
0 ⁵ / mm ² . (R1) _l (R2) _m (R3) _n SiO _1.5 (1)

Here, R1 is a methyl group, R2 is an amino group, an acryloyloxy group, a methacryloyloxy group, an epoxy group, a mercapto group, a chlorine atom or a monovalent organic group having at least one functional group thereof. A group selected from the group consisting of R3 represents an alkyl group having 2 or more carbon atoms, an alkenyl group, a phenyl group, a benzyl group, a phenethyl group, a fluoroalkyl group, or a monovalent group having at least one of these organic groups. A group selected from the group consisting of organic groups represented by the following formulas:
Satisfies (3) and (4). l + m + n = 1.0 (2) 0 ≦ l, m, n (3) 0.01 ≦ m + n (4)

[0007]

(Equation 3)

Here, Dave: average particle diameter, Di: circle equivalent diameter (μm) of each particle, n: number of particles.

The polymer constituting the biaxially oriented polyester film of the present invention is a polyester. Examples of the polyester include, but are not particularly limited to, ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, and ethylene 2,6.
-When at least one structural unit selected from naphthalate units is used as a main component, the scratch resistance and the dubbing resistance are further improved, which is preferable. Among them, a polyester containing ethylene terephthalate as a main component is particularly preferable because the dubbing resistance and the scratch resistance are further improved. In addition, two or more types of polyesters may be mixed or a copolymer may be used within a range not to impair the present invention.

The silicone particles in the present invention are composed of a polysiloxane having a siloxane component having an organic group other than a methyl group. In addition, the silicone particles may contain a small amount of other organic polymer or inorganic component in addition to the polysiloxane within a range that does not impair the effects of the present invention. For example, a small amount of an organic polymer such as polyamide, polyester, polystyrene, polyacrylic acid, epoxy resin, and phenol resin may be copolymerized or physically mixed. In addition, inorganic components such as silica, alumina, titanium oxide, calcium carbonate, and carbon, and components added to ordinary polymers such as pigments, dyes, and antioxidants may be mixed within a usual range.

In the above equation (1), R1, R2, R
3 is an organic group bonded to a Si atom,
l, m, and n each indicate the number of each organic group bonded to one Si atom. R2 and R3 each represent a siloxane component having an organic group other than a methyl group, at least one of which is contained in the silicone particles, and R2 represents an amino group, an acryloyloxy group, a methacryloyloxy group, an epoxy group, a mercapto group, and a chlorine atom. Or a group selected from monovalent organic groups having at least one of those functional groups, R3 is an alkyl group having 2 or more carbon atoms, an alkenyl group, a phenyl group, a benzyl group, a phenethyl group, a fluoroalkyl group, Or a group selected from monovalent organic groups having at least one of these groups. And
As shown in the above formula (4), R bonded to one Si atom
The total number of organic groups 2 and R3 needs to be 0.01 or more.

In the above formula (1), R2 is more preferably as follows. That, R2 is Z (CH ₂₎ p, Z is a group selected from the formula 2,

[0013]

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R4 in the above formula (2) is -H, -CH ₂
CH ₂ NH ₂ or a phenyl group,
R5 is -H, selected from -CH ₂ group, p is
2 or 3.

Specific examples of R2 include Chemical Formula 3 and the like.

[0016]

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A specific example of R3 is shown in Chemical Formula 4.

[0018]

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Each of R2 and R3 may be composed of only the same kind of organic group, or may contain a plurality of different components. Further, all organic groups of R2 and R3,
That is, the molar ratio to R1, R2, and R3, that is, (m + n) / (l + m + n) is preferably larger than 0.05, particularly preferably larger than 0.20.

Specific examples of the composition of the silicone particles in the present invention are shown in the following Chemical Formula 5, but the silicone particles of the present invention are not limited to these.

[0021]

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In the present invention, when a plurality of types of siloxane components are contained, it is preferable that the components are substantially uniformly distributed. Substantially uniform means that each siloxane component is distributed in approximately equal amounts throughout the particle. For example, only the center portion of the particles (R1SiO _1.5), the outer shell portion and (R2SiO _1.5) (R3Si
Compared to particles composed only of O _1.5 ), the substantially uniform particles can further exert the effects aimed at by the present invention. However, it is not necessary to be a completely random copolymer at the molecular level, and even a block copolymer is substantially uniform. The method for confirming that the particles are substantially uniform includes the following method. That is, the particles are treated with an aqueous alkaline solution and gradually dissolved from the surface. If a plurality of solutions having different dissolution amounts are collected while changing the dissolution time, and the composition of each solution is analyzed, the distribution state of the organic groups in each particle layer can be known.

The method for obtaining the silicone particles in the present invention is not particularly limited, and examples thereof include the following methods. As a raw material, a silane compound having an organic group represented by the formula (1) is used. As a specific example,
Examples of compounds corresponding to R1 include methyltrimethoxysilane, methyldimethoxyethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltryptoxysilane, and methylmethoxydipoxysilane. Examples of compounds corresponding to R2 include 8-aminopropyl. Triethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, 3-anilinopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane,
3-mercaptopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexylethyl) trimethoxysilane For example, n-hexyltrimethoxysilane, cyclohexyltriethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, benzyltrimethoxysilane, phenethyltrimethoxysilane,
3,3,3-trifluoropropyltrimethoxysilane and the like can be mentioned.

The silicone fine particles of the present invention can be obtained by combining the above silane compound or its partially hydrolyzed product in an amount suitable for the desired composition under specific conditions.

Usually, heating is carried out in the presence of a siloxane-bonded catalyst using water or a lower alcohol as a solvent. Although the amount of the solvent can be arbitrarily selected, it is usually used in an amount of 0.5 to 100 times the weight of the silane compound. The siloxane bonding catalyst is selected from various kinds such as an acid, an alkali and a metal compound. In general, an inorganic alkali compound such as an alkali metal hydroxide is preferably used because of its easy handling and availability. The heating temperature and the heating time can be selected from a wide range of conditions, but usually 30 ° C. to 100 ° C. and several minutes to 10 hours are appropriate. The obtained slurry containing particles is subjected to solid-liquid separation by filtration, decanter, or the like, and then, if necessary, washed and dried to obtain desired silicone particles.

The particles thus obtained are silicone particles containing organic groups other than methyl groups uniformly dispersed throughout the particles. In general, when various kinds of fine particles are used, their surface properties and interaction with other substances are very important.

The particles obtained by such a method are:
Surface properties and interactivity with other substances are always stable, and the surface is constantly renewed due to dissolution, abrasion, destruction, etc. of fine particles during reaction or mixing with other substances, and during use. It is considered that particles having more preferable abrasion resistance can be obtained as compared with those obtained by simply surface-treating with a silane compound having another organic group because of having certain physical properties.

The average particle size of the silicone particles according to the present invention defined by the above-mentioned formula 3 is 0.01 to 2 μm,
Preferably it is 0.05-1 μm. Average particle size 0.0
If it is less than 1 μm, the lubricity when formed into a film becomes insufficient, while if it exceeds 2 μm, the flatness of the surface deteriorates, which is not preferable. Therefore, if it is out of this range, the scratch resistance deteriorates as a result. By setting the average particle size in this range, good scratch resistance and dubbing resistance can be obtained.

The content of the silicone particles in the present invention with respect to the resin constituting the film, for example, the polyester, is preferably 0.01 to 5% by weight, more preferably 0.02 to 1% by weight. If the content is less than 0.01% by weight, scratch resistance and dubbing resistance become insufficient,
On the other hand, if it exceeds 5% by weight, the flatness of the surface deteriorates,
It is not preferable because it becomes brittle and the scratch resistance deteriorates.

Further, in the silicone particles of the present invention, the relative standard deviation of the particle diameter defined by the equation (4) is 0.5 or less. This is preferable because coarse projections are not formed on the surface and dropout hardly occurs and scratch resistance is further improved. The relative standard deviation is more preferably 0.3 or less, particularly preferably 0.2 or less.

[0031]

(Equation 4)

The method and timing for adding the silicone particles to the polyester can be determined by a conventionally known method, for example, a method of adding a powder or a glycol slurry to a polyester reaction system, or a method of adding a powder or a slurry. It is possible to take the method of kneading with polyester by using.

When silicone particles are added as a slurry to a reaction system or a polymer, the slurry is mixed with an anion such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate in order to improve the dispersibility of the particles in the slurry and the polymer. Nonionic surfactants such as polysurfactants, polyoxyethylene nonylphenyl ether and polyethylylene glycol monostearate, or water-soluble polymers such as polyvinylpyrrolidone, polyvinyl alcohol and carboxymethyl cellulose may be added.

With respect to the heat resistance of the silicone particles in the present invention, the particles having a heat decomposition temperature of 350 ° C. or higher in an inert gas stream by a thermobalance at a temperature of 350 ° C. or more are used for producing the polyester composition. It is preferable because there is no problem such as agglomeration at the time of melt molding or at the time of collecting and reusing the molded product, thereby impairing the surface uniformity and abrasion resistance of the film.

The biaxially oriented polyester film of the present invention may further contain other particles in addition to the above silicone particles from the viewpoint of scratch resistance and dubbing resistance. Examples of other particles include, but are not particularly limited to, aggregated particles such as alumina, zirconia, and silica having a crystal form of δ, θ, η, and γ, or calcium carbonate particles, colloidal silica particles, and titanium particles. It is preferably exemplified.
A plurality of these particles may be used in combination.

The biaxially oriented polyester film of the present invention comprises the above-mentioned polymer and silicone particles as main components. Other types of polymers may be blended as long as the object of the present invention is not impaired. Organic additives such as additives, heat stabilizers, lubricants and ultraviolet absorbers may be added to the extent that they are usually added.

The biaxially oriented polyester film of the present invention is a film in which the above composition is biaxially oriented. Uniaxial or non-oriented films are not preferred because scratch resistance is poor. Although the degree of this orientation is not particularly limited, the scratch resistance is further improved when the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg / mm ² or more in both the longitudinal direction and the width direction. preferable. The production limit of the Young's modulus, which is a measure of the degree of molecular orientation, is usually about 1500 kg / mm ² .

Further, even when the Young's modulus is within the above range, the orientation of the polymer molecules in a part of the film in the thickness direction, for example, near the surface layer, is not non-oriented or uniaxial. When the molecular orientation of all parts in the thickness direction is biaxial orientation, scratch resistance and dubbing resistance are further improved. Especially when the molecular orientation measured by Abbe refractometer, refractometer using laser, total reflection laser Raman method etc. is biaxial orientation on both the front and back surfaces, scratch resistance and dubbing resistance are even better. Becomes

The biaxially oriented polyester film of the present invention may be in the form of a single-layer film. However, two or three or more layers of at least one film of the present invention and another film are laminated. May be in the state of a laminated film.

In the case of a laminated film, from the viewpoint of scratch resistance and dubbing resistance, the film containing at least the organic particles is preferably one outermost layer of the laminated film having at least a two-layer structure. .

In the case of a laminated structure of three or more layers,
From the viewpoint of scratch resistance and dubbing resistance, the film containing at least the organic particles is preferably one outermost layer of a laminated film having at least a three-layer structure.

The thickness of the film layer containing the organic particles is not particularly limited, but is preferably 0.005 to 3 μm, and more preferably 0.01 to 3 μm, from the viewpoint of scratch resistance and dubbing resistance.
To 2 μm, more preferably 0.02 to 1 μm.

The relationship between the particle size d of the silicone particles and the thickness t of the film layer containing the silicone particles is 0.2d ≦
When t ≦ 10d, preferably 0.5d ≦ t ≦ 5d, and more preferably 0.5d ≦ t ≦ 3d, the scratch resistance and the dubbing resistance are particularly good, which is desirable.

The polymer constituting the layer other than the film layer containing the silicone particles in the laminated structure is not particularly limited, but polyester is preferred. The polyester is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-
It is preferable to use at least one structural unit selected from 4,4'-dicarboxylate and ethylene 2,6-naphthalate units as a main constituent component because scratch resistance and dubbing resistance are further improved. Among them, a polyester containing ethylene terephthalate as a main component is particularly preferable because the dubbing resistance and the scratch resistance are further improved.

Particles may be contained in the polymer constituting the layer other than the film layer containing the silicone particles in the laminated structure. In this case, calcium carbonate, alumina, silica, titanium, carbon black and the like are exemplified.

In the biaxially oriented polyester film of the present invention, the number of projections on at least one side is 2 × 10 ^{3 to} 5 × 10 ³
It is necessary to be ⁵ pieces / mm ² . Even if the number of projections on at least one side is smaller or larger than the above range, the dubbing resistance and the scratch resistance deteriorate. The number of protrusions on at least one side is preferably 3 × 10 ³ to 4 × 10 ⁵ / mm ² , more preferably 5 × 10 ^{3 to} 3 × 10 ⁵ / mm.
mm ² .

Next, the method for producing the film of the present invention will be described for the case of a laminated polyester film.

First, as a method for incorporating silicone particles into the polyester, it is preferable to disperse in a form of slurry in ethylene glycol which is a diol component, and to polymerize the ethylene glycol with a predetermined dicarboxylic acid component. Further, a method of directly mixing a water slurry of particles with a predetermined polyester tel pellet and kneading the mixture with a polyester using a vented twin-screw kneading extruder is very effective for further improving the effect of the present invention. is there.

As a method of adjusting the content of particles, a method of preparing a high-concentration master by the above method and diluting it with a polyester substantially free of particles at the time of forming a film to adjust the content of particles. Is valid.

Next, a pellet containing a predetermined amount of particles is dried as required, and then supplied to a known extruder for melt lamination, extruded into a sheet shape from a slit die, and cooled and solidified on a casting roll. To make an unstretched film. That is, two or three extruders, two or three
The molten polyester is laminated using a layer manifold or a merging block. In this case, a method of installing a static mixer and a gear pump in the polymer flow path containing the aggregated particles is effective for further improving the effect of the present invention.

Next, the unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, it is preferable to use a sequential biaxial stretching method in which stretching is performed first in the longitudinal direction and then in the width direction. The longitudinal stretching is divided into three or more stages, the total longitudinal stretching ratio is 3.0 to 6.5 times, and the temperature is 80 to
It is effective to carry out the method at 150 ° C. and a stretching speed of 5,000 to 50,000% / min. Examples of the stretching method in the width direction include a method using a stenter. The stretching ratio in the width direction is 3.0 to 5.0 times, and the stretching speed is 1,000 to 1,000.
20,000% / min, 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 170 to 2 ° C.
The temperature is preferably in the range of 0.5 to 60 seconds at 10 ° C.

[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) Average particle size of particles The polymer is removed from the film by a plasma low-temperature incineration 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 SEM is about 2000 to 10000 times, and the visual field in one measurement is appropriately selected from about 10 to 50 μm on one side. The number of particles is determined to be 5000 or more by changing the observation position according to the following Expression 5.

[0055]

(Equation 5)

Here, Dave: average particle diameter, Di: circle equivalent diameter (μm) of each particle, n: number of particles.

When the particles are significantly damaged by the plasma low-temperature incineration treatment, the following method may be used.
Using a transmission electron microscope (TEM), 3
Observe at 000-100,000 times. The TEM section thickness is about 1000 Å, and
It measures from 0 or more visual fields and calculates | requires from said formula.

(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 polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Film Lamination Thickness The depth profile of the particle concentration is measured by XPS (X-ray photoelectron light method), IR (infrared spectroscopy) or a confocal microscope while etching from the surface. In the surface layer of the film laminated on one side, 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 laminated on one side according to the present invention, the particle concentration which has once reached the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, a depth [II] (here, に な る of the maximum particle concentration) (where,
II> I) was taken as the lamination thickness. Further, when inorganic particles and the like are contained, a secondary ion mass spectrometer (S
IMS), the particle concentration is defined as the concentration ratio (M ⁺ / C ⁺ ) of the element resulting from the highest concentration of the particles in the film to the carbon element of the polyester, and the depth from the surface of the polyester A layer. The analysis in the (thickness) direction is performed. Then, the lamination thickness is obtained from the same method as described above. In addition, it can also be obtained by observing a film cross section or a thin film step measuring device.

(4) Molecular Orientation of Film Surface Using a sodium D line (589 nm) as a light source, the molecular orientation was measured using an Abbe refractometer. The measurement was performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution. The biaxial orientation of the polymer is determined by setting the refractive index in the longitudinal, width, and thickness directions to N.
Assuming that 1, N2 and N3 are the absolute values of (N1−N2) are 0.07 or less, and N3 / [(N1 + N2) / 2] is 0.95 or less. Further, the refractive index may be measured using a laser refractometer. Furthermore, if measurement is difficult with this method,
By Yvon Ramanor U-1000 Raman system,
The total reflection Raman spectrum was measured. For example, in the case of PET, 1615 cm ^-1 (skeleton vibration of the benzene ring) and 17
Polarization measurement ratio (YX / XX ratio, etc.) of the band intensity ratio of 30 cm ^-1 (stretching vibration of carbonyl group), where YY: Raman light detection parallel to Y with laser polarization method set to Y, XX: laser It is possible to utilize the fact that the polarization direction of X is Raman light detection parallel to X) corresponding to the molecular orientation. The biaxial orientation of the polymer can be determined by converting the parameters obtained from the Raman measurement into the refractive index in the longitudinal direction and the width direction, and from the absolute value, difference, and the like. The measurement conditions in this case are as follows. Light source Argon ion laser (5145A) Sample setting The film surface is pressed against a total reflection prism, and the angle of incidence of the laser on the prism (the angle with the film thickness direction) is 60.
°. Detector PM: RCA31034 / Photon Counting System (Hamamatsu C1
230) (supply 1600V) Measurement conditions SLIT: 1000 μm LASER: 100 mW GATE TIME: 1.0 sec SCAN SPEED: 12 cm ^-1 / min SAMPLING INTERVAL: 0.2 cm ^-1 REPEAT TIME: 6

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

(6) Number of protrusions on the film surface A two-detector scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and a cross section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the flat portion of the film surface was set to 0, and the height measurement value of the projection when scanning was performed using an image analyzer [IBAS2000, Carl Zeiss Co., Ltd.]
And reconstruct a film surface projection image. Next, with respect to each projection obtained by binarizing the projection portion with this surface projection image, the location is changed and repeated 500 times.
The number of protrusions was determined. The magnification of the scanning electron microscope (SEM) is selected to a value between 1000 and 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40 to 200
The normal height method obtained by using the above-mentioned method can be used instead of the SEM value.

(7) Scratch resistance A film obtained by slitting the film into a tape having a width of 1/2 inch is run on guide pins (surface roughness: 100 nm in Ra) using a tape running tester ( Travel speed 2
(50 m / min, running frequency 1 pass, winding angle: 60 °, running tension: 90 g). At this time, the scratches in the film were observed with a microscope, and when the number of scratches with a width of 1 μm or more was less than 2 per tape width, it was judged as excellent. Although excellent is desirable, even good is practically usable.

(8) Dubbing Resistance A magnetic paint having the following composition is applied to the film by using a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
After performing a calendering process at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing is performed at 70 ° C. for 48 hours. The raw tape was slit into 1/2 inch to prepare a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to form a VTR cassette tape. (Composition of magnetic paint) Co-containing iron oxide: 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 A 100% chroma signal is recorded on this tape by a TV test waveform generator using a home VTR, and a reproduced signal thereof. Chroma S / N is measured with a color video noise meter from
And After dubbing the pancake of the master tape on which the same signal as described above was recorded to the pancake of the same sample tape (unrecorded) as in the measurement of A using a magnetic field transfer type video software high-speed printing system (sprinter) The chroma S / N of the tape was measured in the same manner as above.
And Reduction of chroma S / N by this dubbing (A-
When B) was less than 3 dB, the anti-dubbing property was excellent. When it was 3 dB or more and less than 5 dB, it was judged as good, and when 5 dB or more was bad. Although excellent is desirable, even good is practically usable.

[0065]

Next, embodiments of the present invention will be described based on examples. Example 1 (Table 1) Silicone particles having the composition shown in Table 1 (average particle size: 0.5
μm) of water slurry was directly mixed with polyethylene terephthalate pellets and kneaded using a vented twin-screw extruder to obtain polyethylene terephthalate master pellets. Further, a master pellet of polyethylene terephthalate containing no particles was obtained.

These polymers were mixed so that the content of silicone particles became 0.6% by weight, and dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then supplied to extruder 1 and extruder 2, respectively. 280 ° C. After high-precision filtration of these polymers, three layers were laminated at the rectangular junction (A / B / A).

This was wound around a casting drum having a surface temperature of 25 ° C. using an electrostatic application casting method and cooled and solidified to prepare an unstretched film. At this time, the ratio of die slit gap / unstretched film thickness was set to 10. Further, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the thermoplastic resin A layer.

This unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 85 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film is stretched at a stretching speed of 2,000% / min.
The film was stretched 4.0 times in the width direction at 100 ° C., and was heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a total thickness of 14 μm and a thickness of the laminated portion of 1.0 μ
m biaxially oriented laminated film was obtained. The characteristics of this film were as shown in Table 1, and the scratch resistance and the dubbing resistance were good.

Examples 2 and 3 and Comparative Examples 1 and 2 (Table 1) In the same manner as in Example 1, films were obtained in which the kind of particles, the particle diameter, the composition of the dicorn particles, the number of surface protrusions, etc. were changed. As shown in Table 1, the film in the range of the present invention has good scratch resistance and dubbing resistance, but if it is not, the film cannot satisfy both scratch resistance and dubbing resistance.

[0070]

[Table 1]

[0071]

According to the biaxially oriented polyester film of the present invention, since silicone particles having a specific composition are used and the number of projections on the film surface is in a specific range, the film surface is hardly damaged, and when used for magnetic media. , Excellent image quality,
Dropout characteristics can be obtained.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 83:04) C08L 83:04) B29K 9:00 B29K 9:00 67:00 67:00 B29L 7:00 B29L 7:00 C08L 67: 00 C08L 67:00 (56) References JP-A-50-139896 (JP, A) JP-A-3-207725 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J5 / 18 B29C 55/12-55/16 B32B 27/36 C08L 67/00-67/08 C08L 83/04-83/08

Claims (6)

(57) [Claims] 1. The method according to claim 1, wherein the average particle size defined by the expression 1 is 0.01 to
2 μm, the composition substantially contains silicone particles represented by the polysiloxane of the formula (1), and the number of protrusions on at least one side is 2 × 10 ^{3 to} 5 × 10 ⁵ / mm ^2. Characteristic biaxially oriented polyester film. (R1) _l (R2) _m (R3) _n SiO _1.5 (1) (where R1 is a methyl group, R2 is an amino group, an acryloyloxy group, a methacryloyloxy group, an epoxy group, a mercapto group, a chlorine atom or A group selected from the group consisting of monovalent organic groups having at least one of those functional groups, R3 is an alkyl group having 2 or more carbon atoms, an alkenyl group, a phenyl group, a benzyl group, a phenethyl group, a fluoro group; An alkyl group or a group selected from the group consisting of monovalent organic groups having at least one of these organic groups,
m and n satisfy the following expressions (2), (3) and (4). l + m + n = 1.0 (2) 0 ≦ l, m, n (3) 0.01 ≦ m + n (4)) Here, Dave: average particle diameter, Di: circle equivalent diameter (μm) of each particle, n: number of particles. 2. In the above formula (1), R2 is Z (CH ₂ ) p, and Z is a group selected from the formula (1). R4 in the chemical formula _{1, -H, -CH 2 CH 2 NH} 2
Or a group selected from a phenyl group, R5 is -H, a group selected from -CH _2, p is 2 or 3, according to claim 1, wherein the biaxially oriented polyester Film. 3. The biaxially oriented polyester film according to claim 1 or 2, comprising silicone particles having a relative standard deviation of a particle size defined by the formula (2) of 0.5 or less. . (Equation 2) 4. The method of claim 1 to biaxially oriented polyester film according to any one of 3, biaxially oriented polyester, characterized in that the laminated comprising as one of the outermost layer of the laminated film composed of at least two-layer structure Film. 5. A biaxially oriented polyester film according to any one of claims 1 to 3, at least three layers of a laminated film consisting of the structure one biaxially oriented polyester, characterized in that the laminated comprising as an outermost layer Film. 6. The biaxially oriented polyester film according to claim 4, wherein the relationship between the average particle size d of the silicone particles and the thickness t of the outermost layer is 0.2d ≦ t ≦ 10d. M