JP2569941B2 - Biaxially oriented polyester film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film.

[Prior Art] As a biaxially oriented polyester film, a film in which a polyester contains substantially spherical silica particles caused by colloidal silica is known (for example, JP-A-59-171623).

[Problems to be Solved by the Invention] However, the above-mentioned conventional biaxially oriented polyester film is subjected to a film processing step, for example, a printing step in a packaging application, a magnetic layer coating / calendering step in a magnetic medium application, or a thermal transfer in a thermal transfer application. As the process speed of layer coating and the like increases, powder generated by shaving the film surface by a contacting roll has become a problem in process and product performance.

In addition, video tapes, which are the main applications of films, are often used for software (recorded video works fixed on a package medium, duplicated or expanded) in many cases. On videotape,
There is also a problem that the S / N (signal / noise ratio, image quality parameters) is greatly reduced when dubbing (recording and copying) from a master tape at high speed in the "video recording process", resulting in poor image quality. I have.

The present invention solves such a problem, and the surface is less likely to be scraped (hereinafter referred to as good scraping resistance), and the image quality (S / N) is less reduced by dubbing (hereinafter referred to as dubbing resistance).
The purpose is to provide a film.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an A layer made of polyester A containing 3 to 20% by weight of at least one kind of particles on at least one surface of a B layer made of polyester B. A biaxially oriented film obtained by laminating, wherein the ratio t / d of the thickness t of the A layer to the average particle diameter d of the particles contained in the A layer is 0.1.
~ 2.5, the number of coarse protrusions on the surface of the polyester A layer is 100
/ 100 cm ² or less, which is a biaxially oriented polyester film.

The polyester A constituting the layer A of the present invention is not particularly limited, but ethylene terephthalate, ethylene α, β-
When at least one structural unit selected from bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate, ethylene 2,6-naphthalate unit, or the like is used as a main component, abrasion resistance and dubbing resistance Is more preferable. Further, the polyester A constituting the present invention
Is extremely desirable because it is more excellent in abrasion resistance and dubbing resistance when it is crystalline. The crystallinity here means that it is not so-called amorphous, and quantitatively, the cold crystallization temperature Tcc is detected by the measurement of the differential scanning calorimeter, and the crystallization parameter ΔTcg is 150 ° C or less. Things. Further, when the heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter shows a crystallinity of 7.5 cal / g or more, the abrasion resistance and the dubbing 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.

Particles in the layer A of the present invention have a particle size ratio (particle major axis / minor axis).
In particular, particles having a particle size of 1.0 to 1.3, particularly spherical particles, are desirable because the abrasion resistance is further improved.

The particles in the layer A of the present invention are particularly desirable when the single particle index in the film is 0.7 or more, preferably 0.9 or more, because the abrasion resistance and the dubbing resistance are further improved.

When the relative standard deviation of the particles in the layer A of the present invention is 0.6 or less, preferably 0.5 or less, it is desirable because the abrasion resistance and the dubbing resistance are further improved.

The type of particles in the A layer is not particularly limited, but alumina silicate, silica in which primary particles are aggregated, internally precipitated particles, and the like are not preferable to satisfy the above preferable particle characteristics, and are caused by colloidal silica. Substantially spherical silica particles, particles of a crosslinked polymer (for example, crosslinked polystyrene and crosslinked divinylbenzene) and the like can be mentioned.

However, other particles, such as particles of calcium carbonate, titanium dioxide, alumina, etc., can be sufficiently used by appropriately controlling the film thickness and the average particle size.

The size of the particles is not particularly limited, but the average particle size in the polyester A layer is 0.03 to 1.5 μm, particularly 0.03 to 1 μm.
In the case of m, the abrasion resistance and the dubbing resistance are further improved, which is desirable.

The content of the particles in the layer A of the present invention must be 3 to 20% by weight, preferably 4 to 15% by weight, and more preferably 4 to 10% by weight. If the content of particles is less than the above range, the abrasion resistance becomes poor, and if the content is large, the abrasion resistance,
It is not preferable because the dubbing resistance becomes poor.

The A layer is mainly composed of a composition comprising polyester A and particles, but within a range not to impair the object of the present invention,
Other types of polymers may be blended, or an antistatic agent,
Organic additives such as a conductive agent, an antioxidant, a heat stabilizer, a lubricant, and an ultraviolet absorber may be added to the extent that they are usually added.

The film of the present invention is a biaxially oriented polyester film obtained by laminating the above-mentioned composition containing polyester A and particles as main components on at least one surface of the composition containing polyester B as main component. Uniaxial or non-oriented films are not preferred because the abrasion resistance becomes poor. While the extent of this orientation is not particularly limited, measure a is the Young's modulus in the longitudinal direction of the degree of molecular orientation of the polymer, since the chipping resistance is further improved when it is 350 kg / mm ² or more in both the width direction very desirable. The upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but usually about 1500 kg / mm ² is the manufacturing limit.

Further, the film of the present invention, even if the Young's modulus is within the above range, a part in the thickness direction of the film, for example, the orientation of the polymer molecules near the surface layer is non-oriented, or not uniaxially oriented, that is, It is particularly desirable that the molecular orientation of all portions in the thickness direction is biaxial orientation, because the abrasion resistance, the dubbing resistance, and the friction coefficient are further improved.

Abbe refractometer, refractometer using a laser, molecular orientation measured by total reflection laser Raman method, etc.
This is particularly desirable because the dubbing resistance is further improved.

Further, polyester A is a crystalline polyester,
When the total reflection Raman crystallization index of the surface is 20 cm ^-1 or less, preferably 18 cm ^-1 or less, and more preferably 17 cm ^-1 or less, it is very desirable because the abrasion resistance and the dubbing resistance are further improved.

Further, the ratio of the layer thickness t of the layer A of the film of the present invention to the average particle diameter d of the particles contained in the layer A, t / d is 0.1 to 2.5, preferably 0.2 to 2, more preferably 0.3 to 0.9. Must be in the range If t / d is larger than the above range, both the dubbing resistance and the abrasion resistance become poor, and if it is small, the abrasion resistance becomes poor, which is not preferable.

In the film of the present invention, the number H1 of coarse protrusions on the surface of the layer A obtained by the Newton's ring method utilizing light interference is 100/100 cm ^2.
Below, especially 50 pieces / 100 cm ² , more preferably 40 pieces / 100 cm ²
It must be: If the H1 number is larger than the above range, the abrasion resistance becomes poor, which is not preferable.

The film of the present invention has a layer A thickness of 0.01 to 2 μm, preferably 0.03 to 1.5 μm, more preferably 0.04 to 0.5 μm.
In the case of m, the abrasion resistance and the dubbing resistance are further improved, which is very desirable.

The film of the present invention has abrasion resistance and dubbing resistance when the surface protrusion height of the layer A is 1/3 or more, particularly 1 / (3.5) or more of the average particle diameter of the particles contained in the layer A. It is highly desirable because it is even better.

In the film of the present invention, the average height of the surface protrusions of the layer A is
When the thickness is in the range of 20 to 800 nm, particularly 30 to 600 nm, the abrasion resistance and the dubbing resistance are further improved, which is very desirable.

The surface layer particle concentration ratio measured by the secondary ion mass spectrum of the polyester A film of the present invention is not particularly limited, but the surface particle concentration ratio of the polyester A surface is 1 /
It is particularly desirable that the value be 10 or less, especially 1/50 or less, since the abrasion resistance will be further improved.

The film of the present invention is particularly preferable when the intrinsic viscosity of the layer A is 0.5 or more, preferably 0.55 or more, and more preferably 0.6 or more, because the abrasion resistance is further improved. Note that A
The measurement of the intrinsic viscosity of the layer was carried out on a sample from which the layer A was scraped off from the film surface. If the layer A was difficult to scrape off, the layer A was scraped off from the surface of the thick film before stretching sampled in the process. It may be performed on a sample (the intrinsic viscosity does not change by ordinary stretching or heat treatment).

In the film of the present invention, the ratio between the center line average roughness Ra and the maximum height Rt of the surface of the layer A, Rt / Ra is 9.0 or less, particularly when the film is 8.5 or less, the abrasion resistance and the dubbing resistance are further improved. Especially desirable.

The polyester B constituting the layer B of the film of the present invention may be the same or different from the polyester A, but it is desirable that the polyester B is also crystalline, especially when the crystallinity parameter ΔTcg is in the range of 20 to 100 ° C. This is desirable because the dubbing resistance is further improved. Specific examples include ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate,
When at least one structural unit selected from ethylene 2,6-naphthalate units is used as a main component, it is desirable because dubbing resistance is particularly improved. However, other components may be copolymerized within a range that does not impair the present invention and within a range that does not impair desired crystallinity, preferably within 5 mol%.

In the layer B of the present invention, other types of polymers may be blended, and organic additives such as an antioxidant, a heat stabilizer, a lubricant, and an ultraviolet absorber, as long as the object of the present invention is not impaired. May be added to the extent that is normally added.

It is not necessary for the layer B of the present invention to contain particles, but one or more particles having an average particle size of 0.03 to 1.5 μm are contained in an amount of 0.001 to 0.001 μm.
When it is contained in an amount of up to 0.4% by weight, not only the abrasion resistance is further improved, but also the roll shape of the film is improved, which is desirable. It is desirable to use the kind of the particles contained that is desirably used for the layer A. The types and sizes of the particles contained in the A layer and the B layer may be the same or different.

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

First, as a method of incorporating particles into the polyester A, a method of incorporating the particles in the polyester polymerization step, a polyester substantially containing no particles is preliminarily polymerized, and a vent-type biaxial kneader or the like is used there. The method of kneading the particles is not particularly limited, but before adding the particles, among the diol components of the polyester used, 0.1.
Boiling for about 5 to 1 hour is effective for obtaining the number of coarse projections in the range of the present invention, and for stably producing a t / d film in the range of the present invention without stretching.

Thus, the polyester pellets containing particles are diluted, if necessary, with a polyester substantially containing no particles, dried, and then supplied to a known melt extruder 1 (polyester A), and polyester B (A , B may be the same or different) to the extruder 2, and the polyester A is laminated on at least one side of the polyester B using a two- or three-layer manifold or a merging block. The three-layer sheet is extruded and cooled by a casting roll to make an unstretched film. In this case, the method of laminating using a merging block having a rectangular merging cross section makes the thickness of the polyester A layer uniform in the film width direction, and stably manufactures the t / d film within the scope of the present invention without stretching. It is effective to do.

In this case, the residence time A from the introduction of the polyester A pellets containing the particles into the extruder to the merging with the polyester B is set to 60 minutes or less, and the filtration of the polyester A containing the particles is performed by a leaf disk type filter. It is effective to use a stainless steel filter to obtain the number of coarse projections within the range 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, first use the sequential biaxial stretching method of stretching in the longitudinal direction, then in the width direction,
The longitudinal stretching is divided into three or more stages and the total longitudinal stretching ratio is
The method carried out at 3.5 to 6.5 times is effective for obtaining a film having a relationship between the thickness and the average particle size, the content, the orientation state within a desirable range, and the surface particle concentration ratio within the range of the present invention without stretching.
The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be unambiguously determined, but it is usually that the first stage is in the range of 50 to 130 ° C., the relationship between the thickness and the average particle size in the range of the present invention, the content, Desirable state of orientation state, average protrusion height,
This is effective for obtaining a film having a surface layer particle concentration ratio. The longitudinal stretching speed is 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 generally used. The stretching ratio is suitably in the range of 3.0 to 5.0 times. The stretching speed in the width direction is preferably from 1,000 to 20,000% / min, and the temperature is preferably from 80 to 160 ° C. Further, the film once biaxially stretched may be further stretched in at least one direction. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 200 ° C, especially 170 to 190 ° C, and the time is
A range from 0.5 to 60 seconds is preferred.

[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 polyester is removed from the film by a plasma low-temperature incineration method (for example, PR-503 manufactured by Yamato Scientific Co., Ltd.) to expose the particles. The processing conditions are selected such that the polyester is ashed but the particles are not damaged. This is observed with a scanning electron microscope (SEM), and the image of the particles (shading of light generated by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrument). Is performed, and the number average diameter D obtained thereby is defined as the average particle diameter.

D = ΣDi / N Here, Di is the equivalent circle diameter of the particle, and N is the number.

(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) Crystallization parameter ΔTcg, heat of fusion Measured using a DSC (differential scanning calorimeter) type II manufactured by PerkinElmer. The measurement conditions for DSC are as follows.
That is, 10 mg of a sample is set in a DSC device, dissolved at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected.
The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. The temperature was further increased, and the heat of fusion was determined from the melting peak. Here, the difference between Tcc and Tg (Tcc−Tg) is defined as a crystallization parameter ΔTcg.

(4) Surface Molecular Orientation (Refractive Index) Measured using an Abbe refractometer using sodium D line (589 nm) as a light source. The measurement was performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution. Biaxial orientation of the polymer in the longitudinal direction, a width direction, the refractive index in the thickness direction N _1, N _2, N ₃
When the absolute value of (N ₁ −N ₂ ) is 0.07 or less and N ₃ /
One criterion may be that [(N ₁ + N ₂ ) / 2] is 0.95 or less. Further, the refractive index may be measured using a laser refractometer. Further, when measurement is difficult by this method, a total reflection laser Raman method can be used. The total reflection Raman of the laser was measured by Ramanor manufactured by Jobin-Yvon.
The U-1000 Raman system measures the total reflection Raman spectrum, for example in the case of PET, the polarization measurement ratio of the band intensity ratio of 1615 cm ^-1 (skeletal vibration of benzene ring) and 1730 cm ^-1 (stretching vibration of carbonyl group) (YY / XX ratio, etc., where YY: Raman light detection parallel to Y with laser polarization direction Y, XX: Raman light detection parallel to X with laser polarization direction X) Correspondence with molecular orientation can be used. 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 (5145Å) 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 C1230) (supply 1600V) Measurement conditions SLIT 1000μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (5) Total reflection Raman crystal Total reflection Raman spectrum was measured with a Ramanor U-1000 Raman system manufactured by Jobin-Yvon, and the surface was defined as a total reflection Raman crystallization index with a half-value width of 1730 cm ⁻¹ , which is stretching vibration of a carbonyl group. The measurement conditions are as follows. The measurement depth is about 500 to 1000 angstroms from the surface.

Light source Argon ion laser (5145Å) Sample setting The film surface is pressed against a total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel to each other, and the angle of incidence of the laser on the prism (film thickness direction and Angle) was 60 °.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C1230) (supply 1600V) Measurement conditions SLIT 1000μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (6) Average surface protrusion Height Scanning with a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, manufactured by Elionix Inc.], setting the height of the flat surface of the film surface to 0. The measured height of the protrusions at this time is sent to an image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.], and the film surface protrusion image is reconstructed on the image processing device. Next, a circle-equivalent diameter is determined from the area of each projection obtained by binarizing the projection portion on the surface projection image, and this is defined as the average diameter of the projection. The highest value among the binarized individual projections is defined as the height of the projection, and this is determined for each individual projection. This measurement was repeated 500 times at different locations to determine the number of protrusions, and the average value of the heights of all the measured protrusions was defined as the average height. The standard deviation of the height distribution was determined based on the height data of each projection. The magnification of the scanning electron microscope is selected to be a value between 1000 and 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200
The height information obtained by using (2, the use of a high-resolution camera is effective) may be replaced with the value of the SEM and used.

(7) Center line average surface roughness Ra, maximum height Rt Measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value of 20 measurements.

・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm The definition of Ra and Rt is, for example, the method of measuring and evaluating surface roughness by Jiro Nara (Comprehensive Technology Center, 1983).

(8) Young's modulus According to the method specified in JIS-Z-1702, use an Instron type tensile tester at 25 ° C and 65%
Measured at RH.

(9) Surface layer particle concentration ratio Using secondary ion mass spectrum (SIMS), the concentration ratio of the highest concentration element among the elements caused by the particles in the film to the carbon element of the polyester is defined as the particle concentration, and the thickness is determined. Perform direction analysis. The ratio A / B between the particle concentration A at the outermost surface particle concentration (point at depth 0) measured by SIMS and the maximum concentration B obtained by further analyzing in the depth direction, A / B, was defined as the surface concentration ratio. The measuring device and conditions are as follows. The measuring device and conditions are as follows.

Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany 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 (10) Layer thickness of A layer Using a secondary ion mass spectrometer (SIMS), 3000 nm deep from the surface layer The concentration ratio (M ⁺ / C ⁺ ) of the element resulting from the highest concentration of particles in the film in the range and the carbon element of polyester is defined as the particle concentration, and the 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 which has once reached a maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration was 1/2 of the maximum value (this depth was deeper than the maximum value) was determined, and this was defined as the lamination thickness. The conditions are as follows.

(1) Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany (2) Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster region : 400μm □ Analysis area: Gate 30% Measurement vacuum degree: 5.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A When organic particles are the most abundant particles from the surface to the depth of 3000nm Is difficult to measure with SIMS, so it is possible to measure the same depth profile as above using XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy), etc. while etching from the surface to determine the layer thickness, ,
The lamination thickness can also be determined by recognizing the interface from a change in the particle concentration or a difference in contrast by cross-sectional observation using an electron microscope or the like.

(11) Particle size conversion It is the ratio of the average value of the major axis / the average value of the minor axis of the individual particles in the measurement of the above (1).

 That is, it is obtained by the following equation.

Major axis = ΣD1i / N Minor axis = ΣD2i / N D1i and D2i are the major axis (maximum diameter), minor axis (shortest axis) and N are the total number of the individual particles, respectively.

(12) Relative standard deviation of particle diameter Standard deviation calculated from individual projection diameter Di, average diameter D, and total number N of particles measured by the method of (1) above. Was divided by the average diameter D (σ / D).

(13) Number of rough surface protrusions H1 ^Two measurement surfaces (100 cm ² ) are overlapped with each other and adhered by electrostatic force (applied voltage: 5.4 kV).

The height of the coarse protrusions was determined from the Newton's ring generated by the interference of light at the coarse protrusions between the two films, and the number of coarse protrusions of a single ring or more was defined as H1. The unit of H1 is 200 pieces / 200 cm ² because two 100 cm ² sheets are overlapped. The light source used was a halogen lamp with a 564 nm band-pass filter.

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

(15) Shaving resistance A 270-mm-wide film was treated under the following conditions using a one-stage calender consisting of a metal roll and an elastic roll, and the shaved material attached to the elastic roll was washed with pure water, and then washed. The number of shavings having a size of 3 μm or more contained in the sample is counted (using a particle size distribution measuring device by He-Ne laser scattering).
When the number of shaving powders of 3 μm or more per 1 m ^{2 of the} passing film area was less than 100, the shaving resistance was judged to be good, and when the number was 100 or more, it was judged to be poor.

・ Total running length: 3000m ・ Running speed: 80m / min ・ Metal roll temperature: 95 ℃ ・ Line pressure: 200kg / cm (16) Dubbing resistance Magnetic film of the following composition is applied to the film by gravure roll and magnetically oriented. ,dry. Further, after calendering at a temperature of 70 ° C. and a linear pressure of 200 kg / cm using a small test calender (steel roll / nylon roll, 5 steps), curing is performed at 70 ° C. for 48 hours. The raw tape was slit into 1/2 inch to make a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to form a VTR cassette tape.

(Magnetic paint composition) ・ Co-containing iron oxide (BET value 50m ² / g): 100 parts by weight ・ Slec A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight. Nipporan 2304 (Nippon Polyurethane) Polyurethane elastomer): 10 parts by weight-Coronate L (Polyisocyanate manufactured by Nippon Polyurethane): 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 was recorded on this tape using a household VTR with a Shibasoku TV test waveform generator (TG7 / U706), and the reproduced signal was used to produce a Jibasoku color. The chroma S / N was measured with a video noise measuring instrument (925D / 1) and the result was designated as A. Also, the pancake on the master tape on which the same signal was recorded was used. Chroma S of the tape after dubbing to a pancake of the same sample tape (unrecorded) as in the case where A was measured using a video software high-speed printing system of a field transfer system (for example, a Sprinter manufactured by Sony Magnescale Corporation) /
N was measured in the same manner as above, and was set as B. When the decrease in chroma S / N (AB) due to the dubbing 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. Although excellent is desirable, even good is practically usable.

[Examples] The present invention will be described based on examples.

Examples 1 to 5 and Comparative Examples 1 to 5 Several kinds of particles having different particle diameters were dispersed in ethylene glycol in the form of a slurry, and after transesterification with dimethyl terephthalate, polycondensation was carried out. A chip of the contained polyethylene terephthalate (hereinafter abbreviated as PET) was prepared.

In addition, by a conventional method, PET substantially containing no particles
Was manufactured and it was set as polyester B.

Each of these polymers was dried at 180 ° C for 3 hours under reduced pressure (3
Torr), and each is fed to two extruders and melted at 290 ° C., and these polymers are combined and laminated in a rectangular or two-layer rectangular confluence block (feed block). The film was wound around a casting drum having a surface temperature of 30 ° C. and cooled and solidified to produce an unstretched film having a two- or three-layer structure. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the polyester A layer, and the tube diameter of the apparatus was changed to produce films having different residence times A. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed at a peripheral speed difference between two sets of rolls. This uniaxially stretched film is stretched 4.0 times in the width direction at 100 ° C. at a stretching speed of 2,000% / min using a stenter, heat-treated at 140 ° C. under a constant length for 5 seconds, and further stretched 1.6 times in the longitudinal direction. At 200 ° C. for 5 seconds to obtain a biaxially oriented laminated polyester film having a total thickness of 7.5 μm. The parameters of the present invention for these films are as shown in Table 1. When the parameters of the present invention are within the ranges, the films are excellent in both abrasion resistance and dubbing resistance. Can not be achieved.

[Effects of the Invention] In the present invention, since the relationship between the layer thickness and the average particle size of the polyester containing particles is in a specific range, and the number of coarse projections is reduced to a specific range by devising a manufacturing method,
The film has excellent abrasion resistance and dubbing resistance, and can cope with an increase in film processing speed in various applications. Although the use of the film of the present invention is not particularly limited, it is particularly useful as a base film for a magnetic recording medium in which shaving of the film surface in the processing step is particularly problematic in the processing step and in product performance. In the case of the film of the present invention having a two-layer structure, the surface of the polyester A layer has a running surface (a surface on which the magnetic layer is not coated for a magnetic recording medium, and printing and other coating materials are applied for other applications). It is preferable to use it as a surface that is not used.

Further, the present invention is a film made by direct composite lamination without an operation such as coating in a film forming process,
Compared to a laminated film produced by coating during or after the film forming process, the laminated film has a stronger projection structure, has much better abrasion resistance on the surface, and is advantageous in cost, quality stability, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B29L 7:00 9:00

Claims (4)

(57) [Claims] 1. A biaxially oriented film comprising an A layer made of polyester A containing 3 to 20% by weight of at least one kind of particles laminated on at least one surface of a B layer made of polyester B, The ratio t / d of the thickness t to the average particle diameter d of the particles contained in the layer A is 0.1 to 2.5, and the polyester A
A biaxially oriented polyester film, wherein the number of coarse projections on the surface of the layer is 100 or less per 100 cm ² . 2. The biaxially oriented polyester film according to claim 1, wherein the thickness of the layer A is in the range of 0.01 to 2 μm. 3. The polyester A is a crystalline polyester, and the surface of the layer A has a total reflection Raman crystallization index of 20 cm.
^The biaxially oriented polyester film according to (1) or (2), which is not more than ^-1 . 4. The biaxially oriented polyester film according to claim 1, wherein the intrinsic viscosity of the layer A is 0.5 or more.