JPH04138251A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To upgrade resistance to shaving and resistance to dubbing by confining the relation between the layer thickness sand average particle diameter and the amount of content therein of polyester containing particles of two kinds or more in a specified range. CONSTITUTION:A layer (layer A) formed with a composition composed of polyester A containing particles of two kinds or more as a main component is laminated on a layer (layer B) composed of polyester B. In that case, the average diameter of particles contained in polyester A is made 0.4-10 times of the thickness of layer A, and the total amount of content of particles in the two layers in polyester A is made 3-50wt.%. The relative standard deviation of grain diameter distribution (standard deviation/average particle diameter) of the particles of two kinds or more in polyester A should be 0.6 or less respectively, particularly the deviation of 0.4 or less, and the particle diameter ratio (length/breadth of particle) should be 1.0-1.3 particles respectively, particularly globular particles are desired. Resistance to shaving and resistance to dubbing are upgraded by the above-mentioned arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to biaxially oriented polyester films.

[Prior Art] As a biaxially oriented polyester film, a film in which substantially spherical silica particles derived from colloidal silica are contained in polyester is known (for example, Japanese Patent Application Laid-Open No. 171623/1983). Public bulletin).

[Problem to be solved by the invention] However, the above conventional biaxially oriented polyester film has the following problems:
As process speeds increase in film processing processes, such as the printing process in packaging applications, the magnetic layer coating/calendering process in magnetic media applications, or the thermal transfer layer coating in thermal transfer applications, the film surface is scraped by the contacting rolls. The generated powder is becoming a problem in terms of process and product performance.

Furthermore, videotape, which is the main use of film,
Recently, there are many cases where it is used for software (recording, fixing, copying, and increasing the produced video work on package media), and in this case, the conventional videotape mentioned above is used in the "process of recording the video work". Another problem has arisen in that when dubbing (recording and copying) from a master tape at high speeds, the S/N (signal/noise ratio, image quality parameter) is greatly reduced, resulting in poor image quality.

The present invention improves this problem and prevents the surface from being scraped.
(hereinafter referred to as "good scratch resistance"), and there is little deterioration in image quality (S/N) due to dubbing (hereinafter referred to as "dubbing resistance")
The purpose is to provide film.

[Means for Solving the Problems] In order to achieve the above object, the present invention replaces a layer (A layer) made of a composition mainly composed of polyester A containing two or more types of particles with a layer made of polyester B. A film laminated on at least one side of (layer B), wherein the average particle diameter of the particles contained in polyester A is 0% of the thickness of layer A.
．． 4 to 10 times, and the total content of particles in layer A is 3 to 5
This is a biaxially oriented polyester film characterized in that the content is 0% by weight.

Polyester A constituting the present invention is not particularly limited, but includes ethylene terephthalate and ethylene α.

β-bis(2-chlorophenoxy)ethane-4,41-
It is preferable that at least one structural unit selected from dicarboxylate, ethylene 2,6-naphthalate units, etc. be used as the main constituent, since the abrasion resistance and dabbing resistance will be even better. Further, it is extremely desirable that the polyester A constituting the present invention is crystalline, since this provides even better abrasion resistance and dubbing resistance. Crystallinity here indicates that it is not so-called amorphous, and quantitatively it means that the cold crystallization temperature TCC is detected by measurement with a differential scanning calorimeter, and the crystallization parameter ΔTcg is 1.
The temperature is 50°C or less. Furthermore, the heat of fusion (change in enthalpy of fusion) measured with a differential scanning calorimeter was 7.5 ca.
When the crystallinity is 1/g or more, it is extremely desirable because the abrasion resistance and dubbing resistance become even better. In addition,
Two or more types of polyesters may be mixed or a copolymer may be used within a range that does not impede the present invention.

The polyester A layer of the present invention contains two or more different types of particles in a total amount of 3 to 50% by weight based on the total weight of the A layer.
Preferably 3-20% by weight, more preferably 3-15%
It is necessary that the content be % by weight. If there is only one type of particle, the abrasion resistance will be poor, which is not preferable. Furthermore, if the content of the particles is smaller than the above-mentioned range or conversely larger than the above range, the abrasion resistance and dubbing resistance will be poor, which is not preferable.

In addition, the average particle size of all particles contained in polyester A of the present invention is 0.0 mm of the thickness of layer A. It needs to be in the range of 4 to 10 times, preferably 0.5 to 9 times, more preferably 1.1 to 5 times. If the average particle size is smaller than the above range, the abrasion resistance and dubbing resistance will be poor, whereas if it is larger, the abrasion resistance will be poor, which is not preferable.

The two or more types of particles in the polyester A layer of the present invention have abrasion resistance and dubbing resistance when the relative standard deviation (standard deviation/average particle size) of the particle size distribution is 0.6 or less, particularly 0.4 or less. This is desirable because the properties are even better.

The two or more types of particles in the polyester A layer of the present invention each have a particle size ratio (longer axis/breadth axis) of 1°0 to 1.3, particularly spherical particles, which have good abrasion resistance. This is desirable because it provides even better results.

The type of particles in the polyester A layer of the present invention is not particularly limited, but in order to satisfy the above preferable particle characteristics, alumina silicate, silica in a state where primary particles are aggregated, internally precipitated particles, etc. are not preferable, and colloidal silica is not preferable. Particularly preferred are substantially spherical silica particles caused by silica particles, particles made of crosslinked polymers (for example, crosslinked divinylbenzene, crosslinked polystyrene), etc., but other particles such as calcium carbonate, titanium dioxide, alumina, etc. can also be used in the A layer. It can be fully used by properly controlling the thickness and average particle size.

Further, it is preferable that the difference in average particle size between the two or more types of particles in the polyester A layer is 062 μm or less, particularly 0.1 μm or less, since the abrasion resistance and dubbing resistance will be even better.

Furthermore, the average particle size of the two or more types of particles in the polyester A layer is not particularly limited, but any particle has an average particle size of 0.
A thickness of 0.02 to 1 .mu.m, particularly 0.03 to 0.8 .mu.m, is preferable because the abrasion resistance and dubbing resistance are even better.

The A layer of the film of the present invention has the above-mentioned polyester and particles as its main component, but other types of polymers may be blended within the range that does not impede the purpose of the present invention. Organic additives such as stabilizers, lubricants, ultraviolet absorbers, and antistatic agents may be added to the extent that they are normally added.

The polyester B constituting the B layer of the film of the present invention may be the same or different from the polyester A, but the polyester B
Crystalline polymers are also desirable, especially crystallinity parameter Δ
When Tcg is in the range of 20 to 100°C, it is desirable because the dubbing resistance becomes even better. As a specific example, at least one structural unit selected from ethylene terephthalate, ethylene α, β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate, and ethylene 2,6-naphthalate unit is the main constituent. This is desirable because it provides particularly good dubbing resistance. However, other components may be copolymerized within a range that does not impede the present invention, within a range that does not impair desirable crystallinity, and preferably within 5 mol%.

In the B layer of the present invention, other types of polymers may be blended within a range that does not impede the purpose of the present invention, and organic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added. It may also be added to the extent that it is normally added.

It is not necessary that the B layer of the present invention contains particles, or one or more particles having an average particle size of 0.02 to 1 μm are included.
It is desirable that the content of 1 to 0.5% by weight of 'OO not only improves the abrasion resistance but also improves the winding appearance of the film. It is desirable to use the types of particles that are preferably used in the A layer. A layer and B
The types and sizes of particles contained in the layer may be the same or different.

The film of the present invention is a film in which the above composition is biaxially oriented. - Axial or non-oriented films are not preferred because they have poor abrasion resistance. The degree of this orientation is not particularly limited, but the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg/mm2 in both the longitudinal direction and the width direction.
If it is above, the abrasion resistance will be even better, which is extremely desirable. The upper limit of Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but is usually 1500 kg/m
About m2 is the manufacturing limit.

In addition, even if the Young's modulus of the film of the present invention is within the above range, the orientation of the polymer molecules in a portion of the thickness direction of the film, for example, near the surface layer, is not oriented or is not oriented in the -axis direction, i.e. It is particularly desirable that the molecular orientation in all parts in the thickness direction be biaxial because the abrasion resistance, dubbing resistance, and coefficient of friction will be even better.

In particular, the abrasion resistance and dubbing resistance are even better when the molecular orientation is measured using an Atsube refractometer, a laser refractometer, a total internal reflection laser Raman method, or when both the front and back surfaces are biaxially oriented. This is particularly desirable.

Furthermore, polyester A is a crystalline polyester, and the total reflection Raman crystallization index of its surface is 20 cm-' or less,
Preferably, the thickness is 18 cm-' or less, and more preferably 17 cm-' or less, since the abrasion resistance and dubbing resistance are even better.

In the film of the present invention, the surface protrusion height of the polyester A layer is 1/3 or more of the average particle diameter of the particles contained in the A layer, particularly 1/3 or more,
/(3,5) or more is extremely desirable because the abrasion resistance and dubbing resistance become even better.

Further, in the film of the present invention, the average height of the surface projections of the polyester A layer is 20 to 800 nm, particularly 30 to 600 nm.
It is extremely desirable that the abrasion resistance is within this range because the abrasion resistance and dubbing resistance will be even better.

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 layer particle concentration ratio of the polyester A side is 1/
A value of 10 or less, particularly 1150 or less is particularly desirable because the abrasion resistance becomes even better.

The film of the present invention has excellent abrasion resistance and dubbing resistance when the ratio of the center line average roughness Ra to the maximum height Rt of the surface of the polyester A layer, Rt/Ra, is 9.0 or less, particularly 8.5 or less. This is particularly desirable because it provides even better results.

In the film of the present invention, the number H1 of coarse protrusions on the surface of the polyester A layer is 200 pieces/200 cm2 or less, particularly 100 pieces/200 cm2 or less.
A thickness of 200 cm 2 or less is particularly desirable because the abrasion resistance and dubbing resistance become even better.

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

First, methods for making polyester A contain two or more types of particles include a method in which two or more types of particles are made to be included in the polyester polymerization process, and a method in which polyester containing substantially no particles is polymerized in advance and particles are added thereto. There are no particular limitations, such as a method of kneading two or more types of particles using a vented twin-screw kneader or the like, or a method of preparing polyester containing particles separately by any of the above methods and then mixing them. A method of kneading two or more types of particles into the polyester using a vented twin-screw kneader or the like after incorporating the particles in the polymerization process is effective for making the abrasion resistance particularly good. be.

Thus, pellets of polyester A containing two or more types of particles are diluted with polyester A that does not contain substantially any particles as needed, dried, and then fed to a known melt extruder 1 to form polyester B. (A and B may be of the same type or different types) are supplied to the extruder 2, and using a two or three layer manifold or merging block, polyester A is laminated on at least one side of polyester B, and then the polyester A is laminated on at least one side of polyester B, and then Extrude 2 or 3 layers of sheet,
It is cooled with a casting roll to form an unstretched film. In this case, a method of stacking layers using merging blocks having a rectangular merging cross section is effective in obtaining the relationship between average grain size and thickness of the present invention.

Next, this 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, by using a sequential biaxial stretching method that first stretches in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more stages, and the total stretching ratio is 3.
．． A method performed at a stretching ratio of 5 to 6.5 times is effective for obtaining a film without tearing due to stretching and having a relationship between thickness and average grain size, a content, an orientation state within a desirable range, and a surface layer particle concentration ratio within the range of the present invention. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generalized, but usually the first stage is 50 to 1
The range of 30°C is the relationship between the thickness and average particle size within the range of the present invention,
It is effective in obtaining a film having a desired content, orientation state, average protrusion height, and surface layer particle concentration ratio. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000%/min. A common method for stretching in the width direction is to use a stenter. The appropriate stretching ratio is 3.0 to 5.0 times. The stretching speed in the width direction is 1000 to 200
00%/min and the temperature is preferably in the range of 80 to 160°C. Furthermore, the biaxially stretched film may be further stretched in at least one direction. Next, this stretched film is heat treated. The heat treatment temperature in this case is 170-200
C., particularly 170 to 190.degree. C., and a time period of 0.5 to 60 seconds is suitable.

[Function] The present invention contains two or more types of particles at a high concentration, and sets the relationship between the average particle diameter and layer thickness within a specific range, so that the protrusion height can be made uniform, and It is presumed that the effects of the present invention were obtained as a result of fewer coarse protrusions due to particle aggregation.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Polyester is removed from a film of average particle size by plasma low-temperature ashing process (
For example, the particles are removed using a printer (Model PR-503 manufactured by Yamato Kagaku Co., Ltd.) to expose the particles. The processing conditions are selected so that the polyester is incinerated but the particles are not damaged. This is an SEM
(scanning electron microscope) and connect the image of the particles (shading of light created by the particles) to an image analyzer (for example, Cambridge Instrument Acid QTM900), change the observation location, and perform the next numerical processing when the number of particles is 5000 or more. The number average diameter obtained thereby is taken as the average particle diameter.

D=ΣDi/N Here, Di is the circular radius of the particle, and N is the number of particles.

(2) Particle content A solvent is selected that dissolves the polyester but does not dissolve the particles, centrifuges the particles from the polyester, and defines the particle content as the ratio (% by weight) to the total weight of the particles. In some cases, infrared spectroscopy may also be effective.

(3) Crystallization parameter ΔTCg, heat of fusion was measured using a DSC (differential scanning calorimeter) type II manufactured by PerkinElmer. The DSC measurement conditions are as follows. That is,
10 mg of the sample is set in a DSC device, melted at a temperature of 300°C for 5 minutes, and then rapidly cooled in liquid nitrogen. This rapidly cooled 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 exothermic peak temperature of crystallization from the glass 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 TgO (Tcc-Tg) is defined as a crystallization parameter ΔTcg.

(4) Surface molecular orientation (refractive index) Measured using an Atsube refractometer using sodium D line (589 nm) as a light source. Methylene iodide was used as the mounting solution, and the measurement was performed at 25° C. and 65% RH. The biaxial orientation of the polymer has a refractive index of N in the longitudinal direction, width direction, and thickness direction.
When l , N2 and N3, the absolute value of (NI N2) is 0.07 or less, and N3 / [(Nl +N2
)/2] is 0.95 or less. Alternatively, the refractive index may be measured using a laser refractometer. Furthermore, if measurement is difficult with this method, total internal reflection laser Raman method can also be used.

Laser total internal reflection Raman measurement is performed by Jobin-Yvon
The total reflection Raman spectrum was measured using a Ramanor U-1000 Raman system manufactured by
In the case of , the polarization measurement ratio (YY/XX ratio, etc.) of the band intensity ratio of 1615 cm-' (skeletal vibration of benzene ring) and 1730 cm-' (stretching vibration of carbonyl group).

Here, YY: detection of Mann light parallel to Y with the polarization direction of the laser set to Y; xX: detection of Mann light parallel to X with the polarization direction of the laser set to X) corresponds to molecular orientation. Available. The biaxial orientation of a polymer can be determined by converting the parameters obtained from Raman measurement into refractive indices in the longitudinal direction and width direction, and based on their absolute values, differences, etc. The measurement conditions in this case are as follows.

■Light source Argon ion laser (5145 people) ■Setting the sample The surface of the film is pressed against a total reflection prism, and the incident angle of the laser to the prism (angle with the film thickness direction) is 60
°.

■Detector PM: RCA3]034/Photon Coun
ting 5ysle+n(Ha+namatsu C
l230) (supply 1600V) ■Measurement conditions 5LIT l000μm LASER,]
00rnW GATE TIME], 0secSCAN
5PEED 12cm-1/min SAMPL
ING INTERVAL 0.2cmREPEAT
TIME 6 (5) Total reflection Raman crystallization index Ramanor U-100 manufactured by Jobin-Yvon
The total reflection Raman spectrum was measured using a 0 Raman system, and 1 730 cm - which is the stretching vibration of the carbonyl group.
The half-value width of ' was taken as the total reflection Raman crystallization index of the surface. The measurement conditions are as follows. The measurement depth is about 500 to 1000 angstroms from the surface.

■Light source: Argon ion laser (5145A) ■Setting the sample Press the film surface onto a total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel. The angle with respect to the thickness direction) was 60°.

■Detector PM: RCA31034/Photon Coun
ting System C1
230) (supply 1600V) ■Measurement conditions 5LIT ] 000μm LASERl OmW GATE TIME 1.0secSC8N
5PEED 12cm-'/min
SAMPLING INTERVAL O, 2cm
-'REPEAT TIME 6 (6
) Average height of surface protrusions 2-detector power type scanning electron microscope [ESM~3200,
Co., Ltd. manufactured by Elionix Co., Ltd. and cross-section measuring device [PMS-1,
The measured height of the protrusions is sent to the image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] when the height of the flat surface of the film is set to 0. Reconstruct the film surface projection image. Next, the circular diameter is determined from the area of each protrusion obtained by binarizing the protrusion portion using this surface protrusion image, and this is taken as the average diameter of the protrusion. Also, the highest value among these binarized individual protrusions is the height of the protrusion,
This is determined for each protrusion. 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 taken as the average height. Furthermore, the standard deviation of the height distribution was determined based on the height data of each protrusion. Furthermore, the magnification of a scanning electron microscope is 1000 to 8
Select a value between 000 times. In addition, in some cases,
High-precision optical interference type three-dimensional surface analysis device (TO manufactured by WYKO)
The height information obtained using PO-3D, objective lens: 40 to 200 times, effective use of high resolution camera) is
It may be used instead of the value of M.

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

・Stylus tip radius: 0.5 μm ・Stylus load: 5 mg ・Measurement length: 1 mm ・Cutoff value: 0.08 mm The definitions of Ra and Rt can be found, for example, in “Measurement of Surface Roughness” by Jibu Nara. Evaluation Method” (General Technology Center 198
3).

(8) Young's modulus] According to the method specified in T5-Z-1702, using an Instron type tensile tester,
Measurement was performed at 5° C. and 65% RH.

(9) Surface layer particle concentration ratio Using secondary ion mass spectrometry (SIMS), the concentration ratio of the element with high concentration of elements caused by particles in the film and the carbon element of the polyester is defined as the particle concentration,
Perform analysis in the thickness direction.

Surface particle concentration measured by SIMS (depth 0
The ratio of the particle concentration A at point ) to the maximum concentration B obtained by further analysis in the depth direction, A/B, was defined as the surface layer concentration ratio. The measuring device and conditions are as follows. The measuring device and conditions are as follows.

■ Measuring device Secondary ion mass spectrometer (STMS) West Germany, ^TOM
DIDA3000 to A manufactured by IK Hachisha ■ Measurement conditions Primary ion species 2〇□ Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μm Mouth analysis area: Gate 30% Measurement vacuum degree: 6. OX 1 (I9TorrE
-GU N: 0.5KV-3,0A (10) Lamination thickness of polyester A layer Using a secondary ion mass spectrometer (SIMS), the particles in the film within a depth of 3000 nm from the surface layer were measured. The concentration ratio of the element originating from the particles with the highest concentration and the carbon element in the polyester (M9/C1 is defined 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 particles The particle concentration is low and increases as it moves away from the surface.In the case of the film of the present invention, once the particle concentration reaches a maximum value, it begins to decrease again.Based on this concentration distribution curve, the particle concentration in the surface layer is determined to be one of the maximum values. /2 (this depth is deeper than the depth at which the maximum value is reached) was determined, and this was determined as the lamination thickness.The conditions are as follows.

(1) Measuring device Secondary ion mass spectrometer (SIMS) Manufactured by ATOMIKA, West Germany ＾-DID＾3000 (2
) Measurement conditions Primary ion species: 02 Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μm Analysis area 2 gates 30% Measurement vacuum + 5. OX 10-9TorrE-G
UN: 0.5KV-3, OA Note that if the particles that are most abundant in the depth range of 3000 nm from the surface layer are organic polymer particles, it is difficult to measure with SIMS, so do not etch them from the surface.
(X-ray photoelectron spectroscopy), IR (infrared spectroscopy), etc. may be used to measure the depth profile similar to the above to determine the laminated thickness, or cross-sectional observation using an electron microscope etc. may be used to determine the state of change in particle concentration. It is also possible to recognize the interface from the difference in contrast and determine the laminated thickness.

(11) Particle size ratio In the measurement of (1) above, the average value of the long diameter of each particle /
It is the ratio of the average value of the short axis.

That is, it can be obtained using the following formula.

Major axis = ΣDli/N Minor axis = ΣD 2 i / N Dli, I)! i is the major axis (maximum diameter) and minor axis (shortest axis) of each individual particle, and N is the total number.

(12) Relative standard deviation of particle size The individual projection diameter Di1 average average diameter 0 preliminary deviation σ (=f(Σ(DI −D) 2/N) ') measured by the method in (1) above is the average diameter It is expressed as the value divided by (σ/D).

(13) Number of surface coarse protrusions H1 Two measurement surfaces (100 cm2) are stacked and brought into close contact with each other by electrostatic force (stiffening voltage 5.4 kV).

The height of the coarse protrusions was determined from the Newtonian rings produced by light interference of the coarse protrusions between the two films, and the number of coarse protrusions with a single ring or more was defined as Hl.

The unit of Hl is 2 sheets of 1000m2, so
It becomes 200cm2. The light source is a halogen lamp.
It was used with a 64 nm bandpass filter.

(14) Scraping resistance After processing a film with a width of 270 mm under the following conditions using a one-stage calender device consisting of a metal roll and an elastic roll, the scraped material adhering to the elastic roll was washed with pure water, and the The number of shavings of 3 μm or more contained in the sample was counted (using a particle size distribution measuring device using He-Ne laser scattering). 3 μ converted per 1 m2 of passing film area
When the number of scraping particles of m or more was less than 100 pieces, the scraping resistance was judged to be good, and when it was 100 pieces or more, it was judged as poor.

・Total running length: 3000 m ・Travel speed: 80 m/min ・Metal roll temperature: 95°C ・Linear pressure 2200 kg/cm (15) Magnetic paint with the following composition is applied to the dubbing-resistant film using a gravure roll and magnetically oriented. ,dry. In addition, a small test calender device (steel roll/nylon roll,
After calendering at a temperature of near 0°C and a linear pressure of 200 kg/cm, the product was cured at 70°C for 48 hours. The original tape was slit into 1/2 inch pieces to make pancakes. A length of 250 m from this pancake was assembled into a VTR cassette to make a VTR cassette tape.

(Composition of magnetic paint) - Co-containing iron oxide (BET value 50 m2/g): 100 parts by weight, S-LEC A (vinyl chloride/vinyl acetate copolymer manufactured by Tanesui Chemical): 100 parts by weight Niraporan 230 (polyurethane manufactured by Nippon Polyurethane) Elastomer): 10 parts by weight, Polyisocyanate manufactured by Coronate Nippon Polyurethane)
: 5 parts by weight lecithin =
1 part by weight Methyl ethyl ketone 5 parts by weight Methyl isobutyl ketone 5 parts by weight Toluene 5 parts by weight Carbon black: 2 parts by weight Lauric acid
: 1.5 parts by weight Add household VT to this tape
Using the Sibaku TV test waveform generator (TG7)
/U706) to record a 100% chroma signal, and from the playback signal, use a Sibaku color video noise measuring device (9).
25D/1), and the chroma S/N was measured as A. In addition, the same sample tape (unrecorded) on which A was measured using a magnetic field transfer type video software high-speed printing system (for example, Sony Magnescale's Sprinter) on the master tape pancake on which the same signal as above was recorded. The chroma S/N of the tape after dubbing it onto pancakes was measured in the same manner as above, and it was designated as B. If the chroma S/N reduction (A-B) due to dubbing is less than 3 dB, dubbing resistance is excellent; if it is 3 dB or more and less than 5 dB, it is good.
The above items were determined to be defective. Excellent is desirable, but good is still usable for practical purposes.

[Example] The present invention will be explained based on examples.

Examples 1 to 5, Comparative Examples 1 to 4 Several types of particles (particles 1.3) with different particle sizes were dispersed in ethylene glycol in the form of a slurry, and after transesterification with dimethyl terephthalate, polycondensation was performed. A chip of polyethylene terephthalate (hereinafter abbreviated as PET) containing a predetermined amount of the particles was made. The chips are fed to a vented twin-screw kneading extruder, where cross-linked divinylbenzene particles (particles 2) dispersed in water are added in the form of a slurry, and the particles are kneaded while draining the moisture out of the system through a vent. A PET chip in which silica particles and crosslinked divinylbenzene particles coexist was prepared (polyester A composition).

In addition, PET containing substantially no inert particles was produced using a conventional method to obtain polyester B.

These polymers were each dried under reduced pressure at 180°C for 3 hours (
3 Torr) L, each was fed to two extruders and 2
Melted at 90°C, these polymers were confluently laminated in rectangular confluent blocks (feedblocks) for two or three layers and wound onto a casting drum with a surface temperature of 30°C using electrostatic casting. The mixture was cooled and solidified to produce an unstretched film with a 2- to 3-layer structure. At this time, the total thickness and the thickness of the polyester A layer were adjusted by adjusting the discharge amount of each extruder. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80°C. This stretching was performed using a difference in peripheral speed between two sets of rolls. This -axially stretched film was stretched at a stretching rate of 2000%/min using a stenter at 100°C to a width of 4.0% in the width direction.
The film was stretched twice and heat treated at 200° C. for 5 seconds under constant length to obtain a biaxially oriented laminated polyester film with a total thickness of 15 μm. The parameters of the present invention for these films are shown in Table 1. If the parameters of the present invention are within the range, the film has excellent abrasion resistance and dubbing resistance. It turns out that this cannot be achieved.

Comparative Examples 5 to 6 Using the same particles and polyester as those used in Example 1, films containing only one type of particles were prepared in the same manner, but a film having both abrasion resistance and dubbing resistance was found. (Table 1).

[Effects of the Invention] The present invention sets the relationship between the layer thickness and the average particle size of polyester containing two or more types of particles and the content within a specific range, resulting in a film with excellent abrasion resistance and dubbing resistance. This can accommodate increased film processing speeds for 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 magnetic recording media, where abrasion of the film surface during processing is a particular problem in terms of processing and product performance. Among the films of the present invention, those with a two-layer structure have the surface of the polyester A layer as the running surface (for magnetic recording media, the surface is not coated with a magnetic layer, and for other uses, it is the surface that has been subjected to processing such as printing or the application of other coating materials). It is preferable to use it as a surface that is not exposed.

In addition, the present invention is a film made by direct composite lamination without any operations such as coating during the film-forming process, and has a stronger protrusion structure and surface than a laminated film made during the film-forming process or by subsequent coating. It also has far superior abrasion resistance, and is advantageous in terms of cost and quality stability.

Claims (4)

[Claims] (1) A layer (A layer) consisting of a composition mainly composed of polyester A containing two or more types of particles and polyester B
A film laminated on at least one side of a layer (B layer) consisting of polyester A, in which the average particle diameter of the particles contained in polyester A is 0.4 to 10 times the thickness of layer A, and A biaxially oriented polyester film characterized in that the total content of particles is 3 to 50% by weight. (2) The biaxially oriented polyester film according to claim (1), wherein the difference in average particle diameter of two or more types of particles contained in layer A is 0.2 μm or less. (3) The biaxially oriented polyester film according to claim (1) or (2), wherein the relative standard deviation of the particle diameters of two or more types of particles contained in polyester A is 0.6 or less. (4) Regarding the surface of layer A, the average height of the surface protrusions is 1/3 or more of the average particle diameter of the particles contained, according to any one of claims (1) to (3). Biaxially oriented polyester film.