JPH03207651A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To improve the shaving resistance of the surface of the film concerned by a method wherein the intrinsic viscosity of laminated film layer composition of polyester A is set to be larger than that of base layer film layer composition of polyester B. CONSTITUTION:Film mainly made of polyester A and particles is laminated at least on one side of film mainly made of polyester B. The thickness of laminated film of the polyester A is set to be 0.005-3mum, the mean particle diameter of particles containing in the laminated film is set to be 0.1-10 times as large as the thickness of the laminated film, the particle content in the laminated film and the intrinsic viscosity of the laminated film layer composition of the polyester A is set to be large than that of base layer film layer composition of polyester B and preferably the difference between the intrinsic viscosities is set to be 0.05dl/g or more. By varying in the magnitudes of viscosities as mentioned above, the particle retaining strength of the polyester A layer is kept at high level and the polyester A layer is prevented from becoming brittle due to the interposition of particles, which are concentrated locally in the polyester A layer, by heightening the intrinsic viscosity of the layer, resulting in allowing to keep the shaving resistance and scratch resistance of the film concerned at high level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a biaxially oriented polyester film, particularly a biaxially oriented polyester film having a laminated film/l/me structure suitable as a film for magnetic recording media.

[Prior Art] As a biaxially oriented polyester film with improved surface properties, a film in which substantially spherical silica particles derived from colloidal silica are contained in polyester is known (for example, in JP-A-Sho 59-1 71 623@publication>.

In such a biaxially oriented polyester film,
The contained silica particles form protrusions on the film surface, lowering the coefficient of friction on the surface and improving handling and running properties, as well as improving the adhesion of the magnetic layer in magnetic recording media applications. It is possible.

[Problems to be Solved by the Invention] However, in the above conventional biaxially oriented polyester film, the contained silica particles are randomly distributed throughout the thickness direction of the film, so the density of protrusions due to the contained particles on the film surface is low. There is a limit to the increase, and furthermore, the height of the protrusion will vary considerably at random. Recently, problems have started to be pointed out due to the non-uniform height of the protrusions and the low density of the protrusions.

If the height of the protrusions on the film surface is uneven, the high protrusions are likely to be scraped, and as the processing speed of the film increases, such as the magnetic layer coating and calendering process in magnetic recording media applications, Recently, problems have arisen in which protrusions on the film surface are scraped off and the film surface is scratched by the contacting rolls. In particular, if film powder or particles scraped off from the film surface are mixed in, the quality of the product will be greatly reduced.

In addition, recently, magnetic recording media, especially video tapes, are often used for software (recording and fixing produced video works on package media, copying and increasing them), but in this case, the above-mentioned conventional With film-based video tapes, the S/N ratio is high when dubbing (copying) from a master tape at high speed during the recording process of a video work.
The problem has also arisen that the signal/noise ratio (signal/noise ratio, image quality parameters) is greatly reduced and the image quality is deteriorated.

On the other hand, when the protrusion density on the film surface is low, the effect of improving the slipperiness of the film surface is low, and the handling property is
The effect of improving running performance is not as much as expected.

The present invention forms protrusions of high density and uniform height on the surface of a biaxially oriented polyester film to improve surface scratch resistance (hereinafter referred to as scratch resistance) and to improve dubbing in magnetic tape applications. The purpose is to prevent deterioration of image quality (S/N) (hereinafter referred to as dubbing resistance) and to improve the abrasion resistance of the film surface.

[Means for Solving the Problems] The biaxially oriented polyester film of the present invention that meets this objective is a biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B. An axially oriented polyester film,
The thickness of the polyester A laminated film is o. oo
s~3μ, the average particle size of the particles contained in the laminated film is 0.1 to 10 times the thickness of the laminated film, and the content of the particles in the laminated film is 0.5 to 50% by weight. and the intrinsic viscosity of the polyester A laminated film layer composition is greater than the intrinsic viscosity of the polyester B base film layer composition.

In addition, the above object is achieved by the following (2>(3)(4)
) is also achieved by biaxially oriented polyester films.

(2> A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B, the surface of the laminated film of polyester A formed by the particles The average height of the protrusions is 1/3 of the average particle size of the particles.
．． 5 or more, and the intrinsic viscosity of the laminated film layer set of polyester A is larger than the intrinsic viscosity of the base film layer set of polyester B.

(3) A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B, the surface of the laminated film of polyester A formed by the particles. Regarding the protrusions, the number of protrusions having a height of 1/3 or less of the average particle diameter of the particles is 70% or less of the total number of protrusions, and the intrinsic viscosity of the polyester A laminated film layer composition is lower than that of the polyester B base layer. A biaxially oriented polyester film characterized by having an intrinsic viscosity greater than that of a film layer set.

(4) A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B, the surface of the polyester A laminated film formed by the particles. The relative standard deviation of the height distribution of the protrusions is 0.6 or less, and the intrinsic viscosity of the laminated film layer set of polyester A is greater than the intrinsic viscosity of the base film layer set of polyester B. Characteristic biaxially oriented polyester film.

In these biaxially oriented polyester films, the particles containing the eight layers of polyester film form protrusions with high density and uniform height on the surface, resulting in scratch resistance and
Also, dubbing resistance in magnetic tape applications is improved. As will be described later, particles are concentrated in this polyester A layer to form surface protrusions with high density and uniform height. By making the viscosity higher than the intrinsic viscosity,
Even if particles are concentrated and interposed, this film layer itself can be prevented from becoming brittle. Therefore, while maintaining high abrasion resistance,
Desired film surface protrusions as described above can be formed. In other words, it is possible to achieve both the scratch resistance of the film surface and the dubbing resistance in magnetic tape applications, and the abrasion resistance of the film surface.

Polyester A in the present invention is not particularly limited, but particularly ethylene terephthalate, ethylene α
, β-bis(2-chlorophenoxy)ethane-4,4°-dicarboxylene-1-, ethylene2,6-naphthalene
When the main structure is at least one type of structural unit selected from 1. units, the shape of the surface protrusions, scratch resistance, and dubbing resistance in magnetic tape applications are even better, which is desirable. stomach. In addition, it is extremely desirable that the polyester used in the present invention be crystalline, since this provides even better scratch resistance, dubbing resistance, and abrasion resistance. Crystallinity here indicates that it is not so-called amorphous, and quantitatively, the cold crystallization temperature TCC in the crystallization parameter is detected, and the crystallization parameter ΔTCg is 150°C or less. be. Furthermore, the heat of fusion (enthalpy change of fusion) measured with a differential scanning calorimeter was 7.5c.
It is extremely desirable to exhibit crystallinity of al/9 or higher because transparency and scratch resistance will be even better.

Further, polyester containing ethylene terephthalate as a main constituent is particularly desirable because it provides better scratch resistance on the film surface and better dubbing resistance in magnetic tape applications. Note that two or more types of polyesters may be mixed or a copolymer polymer may be used within a range that does not impede the present invention.

The shape of the particles in the polyester A of the present invention is not particularly limited, but particles having a particle size ratio (length/breadth diameter of particles 10) of 1.0 to 1.3 in the film, particularly spherical particles. In this case, the height of the protrusions formed on the surface can be easily made uniform and the density can be increased easily, so that scratch resistance and dubbing resistance can be greatly improved.

In addition, when the particles in the polyester A of the present invention have a single particle index in the film of 0.7 or more, preferably 0.9 or more, protrusions of uniform height are likely to be formed, and the film surface becomes resistant. This is particularly desirable since scratch resistance and dubbing resistance become even better.

The type of particles in the polyester A of the present invention is not particularly limited, but in order to satisfy the above-mentioned preferable particle properties, preferred particles include] substantially spherical silica particles caused by loidal silica force, particles made of crosslinked polymers ( For example, cross-linked polystyrene). In particular, crosslinked polymer particles with a high degree of crosslinking until the temperature at 10% weight loss (measured in nitrogen using a thermogravimetric analyzer Shimadzu TG-30M, heating rate 20°C/min) is 380°C or higher. Particularly desirable.In the case of spherical silica resulting from colloidal silica forces, substantially spherical silica produced by the alkoxide method and having a low sodium content is particularly desirable.However, other particles, such as calcium carbonate Particles such as titanium dioxide, alumina, etc. can also be used satisfactorily by properly controlling the film thickness and average particle size.

The thickness of the film layer mainly composed of polyester A of the present invention is 0. 005~3μ range, preferably 0.01~1μ
The length is more preferably 0.03 to 0.8 m.

If the film thickness is smaller than the above range, it will not be possible to ensure the abrasion resistance and scratch resistance of the laminated film layer, while if it is larger, surface protrusions of uniform height will be formed at a high density due to the relationship with the contained particles. This results in poor dubbing resistance and scratch resistance.

Furthermore, regarding the size of the particles in the present invention, the average particle size in the laminated film containing the particles is 0.1 to 10 times, preferably 0.5 to 5 times, more preferably 0.5 to 5 times the thickness of the laminated film. The range is 1.1 to 3 times.

If the average particle diameter/laminated film thickness ratio is 12% smaller than the above range, the height of the protrusions formed on the surface will be uneven;
Scratch resistance and dubbing resistance become poor, and conversely, even if the particles are large, the surface protrusions formed by the particles are likely to be scraped off, resulting in poor abrasion resistance, scratch resistance, and dubbing resistance, which is not preferable.

In addition, the average particle diameter (diameter) of the particles in polyester A in the film is from o.oos to 3 μm, preferably 0.02 μm.
-0.45μ general range, scratch resistance,
This is desirable because it provides better dubbing resistance.

Such particles are contained in the polyester A film in an amount of 0.5 to 50% by weight, preferably 2 to 40% by weight, and more preferably 3 to 20% by weight. If it is smaller than this, the film surface protrusion formation density will be too low, making it impossible to obtain good scratch resistance and dubbing resistance.On the other hand, if it is too high, the proportion of particles will be too high, and the laminated film layer itself will become brittle. This is not preferable because it becomes difficult to ensure scratch resistance, scratch resistance, and dubbing resistance.

Further, the average height of the protrusions on the surface of the polyester 13 A laminated film layer formed by the particles is 1/3.5 or more, preferably 1/3 or more of the average particle diameter of the particles. Surface protrusions having such an average height can be obtained by appropriately selecting and setting the average particle size of the contained particles with respect to the thickness of the laminated film from the above-mentioned range.

Alternatively, regarding the protrusions on the surface of the polyester A laminated film formed by the particles, the number of protrusions having a height of 1/3 or less of the average particle diameter of the particles is suppressed to 70% or less of the total number of protrusions. In other words, the number of protrusions that are too low in height, in other words, protrusions that have a low effect of improving scratch resistance and dubbing resistance, can be prevented from becoming too large.

Furthermore, the relative standard deviation of the height distribution of the protrusions on the surface of the polyester A laminated film shaped tC by the particles is 0.6 or less. In other words, by forming protrusions of uniform height, scratch resistance and dubbing resistance are effectively improved.

That is, in the laminated film layer of the biaxially oriented polyester film of the present invention, particles having an average particle size around or larger than the thickness of the film layer are concentrated in this layer. In other words, the ultrathin laminated film contains microparticles with an average particle size near or larger than the thickness of the film. Therefore, the particles can be distributed in the thickness direction of the entire biaxially oriented polyester film, concentrating substantially only on the decoy film layer. As a result, [
The density of particles formed by the particles can be easily increased, and the density of protrusions on the surface of the film formed by the particles can also be easily increased. Furthermore, by containing the particles in the laminated film, the positions of the particles are regulated in the thickness direction of the entire biaxially oriented polyester film, and the thickness and average particle diameter of the laminated film are different from those mentioned above. Since the relationship is as follows, the height of the surface protrusion formed by the particle is
Becomes extremely uniform. Therefore, the scratch resistance of the surface of this laminated film is maintained high, and the dubbing resistance in magnetic tape applications is improved.

A film containing polyester A and particles as main components is laminated on a film containing polyester B as main components.

Polyester B is made of the same material as the above-mentioned polyester 8, and polyester B and polyester A may be of the same type or different.

The polyester A film layer is laminated on both sides or one side of the polyester B film layer. In other words,
This is the case when the laminated structure is A/B/A or A/B, but of course it can also be A/B/C where a C layer with a different surface state from A is provided on the opposite side, or a multilayer structure with more layers. It can also be a structure. (Here, the types of resins A, B, and C may be the same or different. Also, at least one surface must be the A layer.
It is preferable to provide it on the B layer in case of A/B structure, and on the smooth side in case of A/B/C structure. > Polyester B is also preferably a crystalline polymer, and in particular, when the crystallinity parameter ΔTC (+) is in the range of 20 to 100°C, the scratch resistance etc. of the film surface of the polyester B will be even better. 16 is preferable.As a specific example, ethylene terephthalate 1 to
, ethylene α,β-bis〈2-chlorophenoxy〉” nitane-4,4゜-dicanoleboxylene 1., ethylene 2
, 6-naphthalate units as the main structure, it is desirable because the scratch resistance is particularly good. However, some other amount may be copolymerized as long as it does not interfere with the present invention, does not impair desirable crystallinity, and is preferably within 5 mol %.

Polyester B of the present invention may also be blended with other types of volima as long as it 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 be added to the extent that it is normally added.

There is no particular need for particles to be contained in a film containing polyester B as a main component, but particles with an average particle size of 0. 007
~2μm, especially 0.02-0.45μm particles, in very small quantities, e.g. 001-0.7% by weight, especially 0.0
05 to 0.20% by weight, and even 0.05% to 0.20% by weight. 005~0.1
A content of 5% by weight is extremely desirable because it not only improves the coefficient of friction and scratch resistance during processing and use, but also improves the winding appearance of the film. As for the types of particles contained, it is desirable to use those preferably used for polyester A. The types and sizes of particles contained in polyesters A and B may be the same or different.

Polyester A containing the above particles and polyester B are laminated by coextrusion, shaped into a sheet, and then biaxially stretched to form a biaxially oriented polyester film. Lamination by coextrusion in the present invention refers to extruding polyester A containing particles and polyester B using different extrusion devices, and then laminating them before discharging the laminated sheet from a die. This lamination may be performed in the nozzle (for example, a manifold) for forming and dispensing into a sheet shape, but since the laminated film layer is extremely thin as described above, it is performed within the polymer tube before introducing it into the nozzle. It is particularly preferable to form the laminated portion inside the polymer tube in a rectangular shape, since this allows uniform lamination in the width direction.The molten polymer laminated in the rectangular laminated portion inside the polymer tube is formed in the manifold in the mouthpiece. The sheet is widened to a predetermined width in the sheet width direction, discharged from the nozzle in the shape of a sheet, and then stretched biaxially. Therefore, even if the laminated film layer after biaxial orientation is extremely thin, In the rectangular laminated portion, since the particle-containing polyester polymer is laminated to a considerable thickness, the lamination can be easily and accurately performed.

In the biaxially oriented polyester film of the present invention having a laminated structure as described above, the intrinsic viscosity of the laminated film layer set of polyester A is higher than the intrinsic viscosity of the base film layer set of polyester B. is also set large.

Preferably, the difference in intrinsic viscosity is 0.05 (jQ/g or more,
More preferably, it is 0.07 (jQ/g or more).

By creating a size relationship in the intrinsic viscosity in this way,
Even if the particle retention strength of the polyester A layer is maintained high and the particles are concentrated in the polyester A layer, by increasing the intrinsic viscosity of this layer, it is possible to prevent this layer from becoming brittle due to particle intervening. As described above, protrusions of high density and uniform height can be efficiently formed on the film surface while maintaining high abrasion resistance and scratch resistance.

In the biaxially oriented polyester film of the present invention having such a laminated film structure, the difference between the crystallization parameter of the laminated film layer of polyester A and the crystallization parameter of the base film layer of polyester B (the former is different from the crystallization parameter of the latter) is preferably 10° C. or higher, preferably 15° C. or higher.By doing so, it is possible to further improve the abrasion resistance, and to form desired surface protrusions in the polyester A layer. Forming becomes easier.

Further, in the biaxially oriented polyester film of the present invention, it is preferable that the particle concentration ratio of the particles in the surface layer on the laminated film side containing particles is 0.1 or less. As shown in the measurement method described below, this surface layer particle concentration ratio indicates how much the particles forming the film surface protrusions are covered with a thin film of polyester A on the film surface. The higher the degree of substantially direct exposure, the higher the surface layer particle concentration ratio, and the higher the degree of being covered with a thin film of polyester A, although surface protrusions are formed, the lower the surface layer particle concentration ratio.

Because the particles forming the protrusions are covered with a thin film of polyester A, even if the particles are distributed at a high density in the ultra-thin laminated film layer, the particles will be covered with a thin film of polyester B. It will be firmly held by the base film layer. Therefore, by setting the surface layer particle concentration ratio to the above value or less, drop-off of particles, etc. is prevented, and the scratch resistance and further abrasion resistance of the film surface are maintained high.

Such surface layer particle concentration ratio can be achieved by laminating by coextrusion. Incidentally, depending on the coating method, it is possible to coat a film having surface protrusions with a density similar to that of the present invention, that is, a polyester B film layer, with an extremely thin resin layer and to incorporate particles into the resin layer. Although this is possible, the surface layer particle concentration ratio is significantly 21 higher (that is, the degree to which the particles are substantially directly exposed to the surface is significantly higher), and the resulting film has an extremely brittle surface compared to the film of the present invention.

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

First, the particles may be incorporated into polyester A either after, during, or before polymerization, but the method of kneading them into a polymer using a vented twin-screw extruder is a method that achieves the surface morphology within the scope of the present invention. Effective for obtaining film.

In addition, a method for adjusting the particle content is to prepare a high-concentration master using the above method, and then dilute it with polyester that does not substantially contain particles during film formation to adjust the particle content. This is effective in obtaining a film having a surface morphology within the range of the present invention. Furthermore, a method in which the melt viscosity, copolymerization content, etc. of this particle-high concentration master polymer are adjusted so that its crystallization parameter ΔTcg is in the range of 30 to 80°C does not cause stretching breakage and has a surface morphology within the range of the present invention. Effective for obtaining film.

22 Thus, after sufficiently drying the pellets I-A containing particles, they are fed to a known melt extruder and melted at a temperature above the melting point of the polyester and below the decomposition point, and the other polyester containing substantially no particles is melted. B (the type may be the same as or different from the polyester containing the particles) is fed to the laminating device as described above, extruded through a slit-shaped die into a sheet-shaped die, and then placed on a casting roll. Cool and solidify to make an unstretched film. That is, these polyester polymers are laminated using two or three extruders, two or three layer merging blocks or spindles. When using the merging block method, it is effective to make the laminated portion rectangular as described above in order to stably produce a film having a surface morphology within the range of the present invention without unevenness in the width direction on an industrial scale.

Next, this multilayer unstretched film is biaxially stretched and biaxially oriented. The biaxial stretching method may be either a simultaneous biaxial stretching method or a sequential biaxial stretching method, but in the case of a sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then in the width direction, the film having the surface morphology within the range of the present invention is stabilized to 23. Therefore, it is effective for industrial production without unevenness in the width direction. In the case of sequential biaxial stretching, the stretching in the longitudinal direction is divided into two stages, especially three or more stages, at a temperature of 40 to 150°C, and at a temperature of 1000°C.
A method of stretching 3 to 6 times at a stretching speed of ~50,000%/min is effective for obtaining a film having a surface morphology within the range of the present invention. The stretching temperature and speed in the width direction are 80 to 170°C.
, a range of 1,000 to 20,000%/min is suitable. The stretching ratio is preferably 3 to 10 times. Further, if necessary, it can be further stretched again in at least one of the longitudinal direction and the width direction. In any case, the key point of the present invention is to provide an extremely thin layer containing particles and then stretch the stretched film to an area stretching ratio of 9 times or more (longitudinal ratio x width ratio). In this case, the heat treatment conditions are 140 to 250°C, preferably 160 to 220°C for 0.5 to 60 seconds in the width direction in any state of relaxation, slight stretching, or constant length. Although this is suitable, it is desirable to use microwave heating in combination with the heat treatment because it makes it easier to obtain a film having a surface morphology within the range of the present invention.

The manufacturing method of the film of the present invention is characterized by using a highly concentrated particle volima prepared by a special method and having a specific range of thermal properties.
This method involves biaxially stretching the film after forming an extremely thin layer containing particles.In the film forming process, the film is uniaxially stretched and then coated and further stretched, or the biaxially stretched film is coated. The performance of the laminated film produced by this method does not come close to that of the film of the present invention, and the film of the present invention is also superior in terms of cost efficiency.

[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} Average particle size of particles Polyester is removed from the film surface using a plasma low-temperature ashing method (for example, Yamato Scientific p R-503 model) to expose the particles.The processing conditions are such that polyester is incinerated but the particles are Select 25 conditions that will not be damaged. Observe them with a SEM (scanning electron microscope) and connect the particle image (shade of light created by the particles) to an image analyzer (for example, Cambridge Instrument QTM900). In addition to measuring the number of particles, we changed the observation location and reached 500 particles.
If the particle size is 0 or more, the following numerical processing is performed, and the average diameter D obtained thereby is taken as the average particle diameter.

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

(2) Particle content Select a solvent that dissolves the polyester but does not dissolve the particles.The particles are centrifuged from the polyester, and the particle content is defined as the ratio (weight %) to the total weight of the particles.In some cases, infrared rays A combination of spectroscopy is also effective.

(3) Glass transition point T1, cold crystallization temperature Tcc, crystallization parameter △TC g, melting point Perxielmer DSC (differential scanning calorimeter)
Measured using a mold. The DSC measurement conditions are as follows. That is, 10 mg of the sample is placed 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 continued to be gradually raised, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc. Stomach temperature was continued briefly, and the melting peak temperature was taken as the melting point. Also, the difference between Tcc and Tci (Tc
c-Tg) is defined as the crystallization parameter ΔTCg.

(4> Average height of surface protrusions, relative standard deviation of height distribution 2-detector scanning electron microscope [ESIVl3200
, made by Elionix ■] and a cross-sectional measuring device [PMS-1, ■
The height of the protrusion was measured using an image processing device [I BAS2000, Rikiichi Lutz Ice ■'!] when scanning with the height of the flat surface of the film set as O. A
] to reconstruct the film surface protrusion image on an image processing device. Next, with this surface protrusion image, the protrusion part is 2ia
The equivalent circle diameter is determined from the area of each protrusion obtained by the process, and this is taken as the average diameter of the protrusion. Furthermore, the highest value among the binarized individual protrusions 27 is taken as the height of the protrusion, and this is determined for each protrusion. Change this measurement location 5
The number of protrusions was determined by repeating 00 times, and the average height 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. The value obtained by dividing the obtained standard deviation by the average value of the heights was defined as the relative standard deviation. Further, the magnification of the scanning electron microscope is selected to be a value between iooo and 8000 times. In addition,
In some cases, a high-precision optical interferometric three-dimensional surface analysis device (
WYKO TOPO-3D, objective lens: 40-20
0x, use of high-resolution camera is effective> may be read and used as the above-mentioned SEM value.

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

The ratio of the particle concentration A at the outermost layer measured by SIMS (a point at a depth of 28 O) to the maximum concentration B obtained by further analysis in the depth direction, A/B, was defined as the surface layer particle concentration ratio. The measuring device and conditions are as follows.

■ Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany ■
Measurement conditions Primary ion species 2024 Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μ Wide-mouth analysis area: Gate 30% Measurement vacuum degree: 6. Oxl09TorrE-GLJ
N: 0.5KV-3. OA (6) Photo-observe the cross-section of the single particle index film using a transmission electron microscope (TEM) to detect particles. If the observation magnification is set to about 00x, it will be possible to detect particles that cannot be further separated. Particles can be observed.If the total area occupied by particles is A, and the area occupied by aggregates of two or more particles is B, then (A-B)/'A is a single particle. The TEM conditions are as follows and 1
The field of view area = 2μTrt2 was measured at a different location, and 500
Measure visual field.

・Equipment 2 JEM-1200EX ・Observation magnification:
100,000 times Section thickness: Approximately 1,000 ang 1 loam (7> Particle size ratio Average value of the long diameter of each particle in the measurement of (1>) above /
It is the ratio of the average value of the short axis.

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

Major axis - ΣD1i/N Minor axis = ΣD2i/N Di r , where D2i is the major axis (maximum diameter) and minor axis (shortest axis) of each individual particle, and N is the total number.

(8> Thickness of the polyester A layer in the laminated film. Using a secondary ion mass spectrometer (SIMS), we measured the 30 elements originating from the particles with the highest concentration among the particles in the film and the carbon element of the polyester. The concentration ratio (M”/C+
〉 is the particle concentration, and the depth from the surface of the polyester A layer (
Perform analysis in the thickness direction. In the surface layer, the particle concentration is low because of the interface called the surface, and the particle concentration increases as you move away from the surface. In the case of the film of the present invention, the particle concentration once reached a maximum value at depth [I] begins to decrease again. Based on this concentration distribution curve, the depth [■] (where II>I) at which the particle concentration becomes 1/2 of the maximum value was determined as the lamination thickness.

The conditions are the same as in measurement method (5).

In addition, if the particles contained in the film are organic polymer particles, it is difficult to measure by SIMS, so while etching from the surface, XPS (X-ray photoelectron spectroscopy),
The depth profile of the particle concentration may be measured using IR (infrared spectroscopy) or a confocal microscope, and the layer thickness may be determined using the same method as described above.

Furthermore, it can be determined not from the above-mentioned depth profile but by observing the cross section of the film, using a thin film step measuring device, or the like.

31 (9> Intrinsic viscosity [η] (unit: dl/1) A value calculated from the following formula from the solution viscosity measured at 25° C. in orthophenol is used.

That is, ηsp/C=[η1+K[η]2・C where ηsp= (solution viscosity/'solvent viscosity) - LC is the weight of dissolved polymer per 10077L of solvent (g/10
0TrL waist usually 1.2〉, K is Huggins constant (0.34
3〉 In addition, solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(10) A scratch-resistant film slit into a 1/2 inch wide tape is run on a guide pin (surface roughness: 100 nm in Ra) using a tape running tester (running speed 10
0077L/min, number of runs: 10 passes, wrapping angle: 60
°, running tension: 2 og). At this time, the scratches in the film were observed under a microscope, and less than 2 scratches with a width of 2.5 μm or more per tape width were judged as good, 2 or more and less than 10 scratches were judged as good, and 10 or more scratches were judged as poor. Excellent is desirable, but good is still usable for practical purposes.

32 <11> Apply a magnetic paint of the following type to a dubbing-resistant film using a gravure roll, magnetically orient it, and dry it. In addition, a small test calender device (steel roll/nylon roll,
5 stages), temperature = 70℃, linear pressure: 20O KFI/
After calendering at 70° C. for 48 hours. The original tape was slit into 1/2 inch pieces to form pancakes.

A length of 250 m from this pancake is V −f−
It was incorporated into an R cassette and used as a VTR cassette tape.

(Magnetic paint composition) - Co-containing iron oxide (BET value 50 m2/g): 100 parts by weight Eslec A (vinyl chloride/vinyl acetate copolymer manufactured by Sekisui Chemical Co., Ltd.): 10 parts by weight Nitsuporan 2304 (polyurethane manufactured by Nippon Polyurethane) Elastomer>: 10 parts by weight, Cotonate L (Polyisocyanate 1- manufactured by Nippon Polyurethane): 5 parts by weight, lecithin
: 1 part by weight 33 ・Methyl ethyl ketone = 75 parts by weight ・Methyl isobutyl ketone] ~ 75 parts by weight ◆Toluene
:75 parts by weight/force-bon black
:2 parts by weight・lauric acid :
1.5 parts by weight A 100% chroma signal was recorded on this tape using a home VTR using a Shibasoku TV test waveform generator (TG7/U70B), and the playback signal was measured using a Shibasoku color video noise measuring device (925 D). /1〉
The chroma S/N was measured and given as A. In addition, the same sample tape (unrecorded) on which A was measured using a magnetic field transfer video software high-speed printing system (for example, Sony Magnescale's Sprinter) was used to record the master tape pancake on which the same signal as above was recorded. The chroma S/N of the tape after dubbing to the pancake was measured in the same manner as above and designated as B. If the decrease in chroma S/N (A-B) due to this dubbing is less than 3 dB, dubbing resistance is determined. : Yu,
A value of 3 dB or more and less than 5 dB was determined to be good, and a value of 5 dB or more was determined to be poor. Excellent is desirable, but even good is usable for practical purposes.

(12) Press one blade perpendicularly against a tape-like slit of abrasion-resistant film 1/2 inch wide, press it further by 0.5 mm, and run it for 20 cm (running tension: 500 (j,
Running speed: 6.7 crn/sec>. At this time, the height of the scraped material on the film surface attached to the tip of the single blade was read using a microscope.
The unit for the amount of wear is μ〉. If the amount of powder abrasion is 10μ or less on at least one side, the abrasion resistance is good.
If it exceeds 10 μm, the abrasion resistance is judged to be poor. This scraping value of 174: 10 μm is the critical point for determining whether or not problems in process and product performance will occur due to scraping of the film surface during processing steps such as printing and calendering. .

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

Examples 1 to 8, Comparative Examples 1 to 6 Ethylene glycol slurry containing cross-linked polystyrene particles with different average particle diameters, spherical silica particles caused by colloidal silica force, etc. was prepared, and this ethylene glycol slurry was heated at 190°C for 10 minutes. After heat treatment for 5 hours, pellets of polyethylene terephthalate (hereinafter abbreviated as PET) containing a predetermined amount of the particles were made by a conventional method. Polyester A was prepared using this pellet, and polyester A was prepared by a conventional method. P containing no particles
ET was produced and designated as Polyester B. Each of these polymers was dried under reduced pressure (3 Torr) at 180°C for 3 hours.
L/ta. Polyester A is supplied to extruder 1 and melted at 310°C, and polyester B is further supplied to extruder 2.
Melted at 80°C, these bolimars were laminated in a confluent block with a rectangular laminated section before entering the die, and rolled onto a casting drum with a surface temperature of 45°C using the electrostatic casting method. Cool and solidify, polyester A on one side
Unstretched films with two or three layer structures were made. At this time, adjust the discharge rate of each extruder to obtain the total thickness,
The thickness of the polyester A layer was adjusted. (However, Comparative Example 6
is a single layer of A layer). This unstretched film was stretched 36 to 4.5 times in the longitudinal direction at a temperature of 80°C. This stretching was carried out in two stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 4.0 times in the width direction at 100°C at a stretching speed of 2000%/min using a stencil, and then heat-treated at 200°C for 5 seconds at a constant length to give a total thickness of 15 μm. Pan, polyester A layer thickness 0
．． A biaxially oriented laminated film having a size of 03 to 4μ was obtained. The scratch resistance of the polyester A layer side of this film was evaluated, as well as the abrasion resistance of the polyester A layer side.

Next, the dubbing resistance of Horai using these films as magnetic tape was evaluated.

Each parameter as a base film is as shown in Table 1, and when these are within the range of the present invention, scratch resistance, dubbing resistance, and abrasion resistance are good as shown in Table 1. However, if this was not the case, it would not be possible to have both of these characteristics.

[Effects of the Invention] As explained above, when using the biaxially oriented polyester film of the present invention, protrusions of uniform height are formed at a high density on the surface of the particle-containing Borester A layer, and Since the magnitude relationship of the intrinsic viscosity of the polyester A layer and the polyester B layer is set to a specific relationship, it is possible to obtain excellent scratch resistance by uniform protrusion formation, and it is also possible to obtain excellent scratch resistance when used for magnetic tapes. By keeping the intrinsic viscosity of the polyester A layer high, in which the particles are concentrated, it is possible to obtain excellent scratch resistance. A film is obtained that is extremely suitable for use in magnetic recording media and has abrasion resistance.

In addition, the biaxially oriented polyester film of the present invention is a film made by direct composite lamination by coextrusion without any operation such as coating during the film forming process,
Compared to laminated films made during the film forming process or by subsequent coating, the molecules in the outermost layer are also biaxially oriented, making the surface layer as well as the entire film extremely strong, while also providing stable cost and quality. You will have an advantage in sex and smell.

39

Claims (1)

[Claims] 1. A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B, comprising:
The thickness of the polyester A laminated film is 0.005
~3 μm, the average particle size of the particles contained in the laminated film is 0.1 to 10 times the thickness of the laminated film, and the content of the particles in the laminated film is 0.5 to 50% by weight,
A biaxially oriented polyester film characterized in that the intrinsic viscosity of the laminated film layer composition of polyester A is greater than the intrinsic viscosity of the base film layer composition of polyester B. 2. A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B,
The average height of the protrusions on the surface of the polyester A laminated film formed by the particles is 1/3 of the average particle size of the particles.
5 or more, and the intrinsic viscosity of the laminated film layer composition of polyester A is larger than the intrinsic viscosity of the base film layer composition of polyester B. 3. A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B,
Regarding the protrusions on the surface of the polyester A laminated film formed by the particles, the number of protrusions with a height of 1/3 or less of the average particle diameter of the particles is 70% or less of the total number of protrusions, and,
A biaxially oriented polyester film characterized in that the intrinsic viscosity of the laminated film layer composition of polyester A is greater than the intrinsic viscosity of the base film layer composition of polyester B. 4. A biaxially oriented polyester film in which a film mainly composed of polyester A and particles is laminated on at least one side of a film mainly composed of polyester B,
A base film layer in which the relative standard deviation of the height distribution of protrusions on the surface of the polyester A laminated film formed by the particles is 0.6 or less, and the intrinsic viscosity of the polyester A laminated film layer composition is polyester B. A biaxially oriented polyester film characterized by having a higher intrinsic viscosity than the composition. 5. Claims 1 to 4, wherein the difference between the crystallization parameter of the laminated film layer of the polyester A and the crystallization parameter of the base film layer of the polyester B is 10°C or more.
The biaxially oriented polyester film according to any one of the above.