JPH0584821A - Biaxially stretched laminated film - Google Patents

Abstract

PURPOSE:To obtain excellent slipperiness, abrasion resistance and electromagnetic conversion characteristics by a method wherein non-round soft particles having low strength are included and, at the same time, highly dense surface projections having even height are formed. CONSTITUTION:The film concerned has the lamination structure consisting of two or more layers. At least one side outermost layer part contains particles, the particle diameter ratio of each of which is 1.1-10 and the strength of each of which under 10% deformation is 10kgf/mm<2> or less. The relative standard deviation of the distribution of the height of the surface projections of the film due to the particle is 1.0 or less and the number of the projections is 5,000/mm<2> or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention contains fine particles which are originally non-round (deformed) because of their low strength when deformed, and
The present invention relates to a biaxially oriented laminated film which is excellent in slipperiness and abrasion resistance when formed into a film, and particularly excellent in electromagnetic conversion characteristics when used as a magnetic tape.

[0002]

2. Description of the Related Art In the secondary processing and use of biaxially oriented laminated film, for example, biaxially oriented polyester film,
The slidability and abrasion resistance greatly affect the workability in the manufacturing process and the processing process in various applications.
When used as a base film of a magnetic tape, for example, if these properties are insufficient, the friction between the coating roll and the film increases during the manufacturing process of the magnetic tape, and the film is wrinkled. Scratches may occur. Further, abrasion powder of the film is liable to be generated, and coating omission occurs in the step of applying the magnetic layer, and as a result, magnetic recording omission (drop-out) or the like is caused.

As a method for improving the slipperiness of a film, many proposals have been made so far to incorporate inorganic particles such as titanium dioxide, calcium carbonate and silicon dioxide into polyester. However, since these inorganic particles are hard and have a low affinity with polyester, for example, when they are used as a film, they are used in a calendar process in the step of applying a magnetic layer or with a roll during film running. contact,
When an external force is applied due to contact between the films during winding, the films easily fall off, which causes scrapes, deterioration of slipperiness and scratches on the surface. Moreover, since the particles that have fallen off are themselves hard, scrapes and surface scratches will increase synergistically with time. If such scraps are often generated and the surface is scratched, the coating may be missed in the step of coating the magnetic layer, causing drop-out. further,
Since the particles are hard and the projections on the film surface are hard, the surface projections due to the particles of the diamagnetic layer are transferred to the magnetic surface in the curing step after coating and winding the magnetic layer, and the electromagnetic conversion characteristics of the magnetic surface. May worsen.

As a method for improving the affinity between the particles and the film base material, surface treatment of inorganic particles, use of organic particles, etc. have been proposed. As the surface treatment of the inorganic particles, for example, the surface treatment with a polyacrylic acid-based polymer as disclosed in JP-A-63-128031 and JP-A-62-2353 are disclosed.
53, JP-A-63-234039, surface treatment with a phosphorus compound, JP-A-62-223239 and JP-A-63-313345, surface treatment with a coupling agent, JP-A-63-304038. Surface treatment with a silane compound, JP-A-63-280763.
Although the surface treatments by grafting with glycol have been proposed in the publications, the abrasion resistance is not sufficient even if these methods are adopted. As organic particles, Japanese Patent Publication No. 63-45409 and Japanese Patent Laid-Open No. 59-217 are available.
No. 755 and JP-A-2-189359 propose crosslinked polymer fine particles, but the abrasion resistance is not sufficient even if these methods are adopted.

[0005]

As a result of intensive studies, the present inventors have used non-round fine particles that are soft and originally deformed, and determine the height and number of surface protrusions formed by the fine particles. It has been found that the regulation can greatly improve the slipperiness and the abrasion resistance, and can also suppress the transfer of the projections formed by the particles. An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a biaxially oriented laminated film which is excellent in slipperiness and abrasion resistance and, at the same time, can exhibit excellent electromagnetic conversion characteristics when formed into a magnetic tape. Especially.

[0006]

In order to achieve the above object, the biaxially oriented laminated film of the present invention is a biaxially oriented laminated film having a laminated structure of two or more layers, and has at least one outermost surface layer portion. In addition, the particle size ratio is 1.1 to 10 and the particle is 1
It contains particles having a strength when deformed by 0% of 10 kgf / mm ² or less, the relative standard deviation of the height distribution of the surface protrusions of the outermost layer is 1.0 or less, and the number of protrusions is 5000 / mm ^2.
It consists of the above.

The biaxially oriented laminated film of the present invention needs to have a laminated structure of at least two layers. As long as there are two or more layers, three layers or four layers may be used. By containing a predetermined amount of a predetermined particle in at least the outermost layer portion of the laminated film, the particles can be efficiently concentrated in the outermost layer portion to form a desired protrusion on the film surface. With a single-layer film, it is difficult to satisfy the target electromagnetic conversion characteristics and abrasion resistance.

The material of the biaxially oriented laminated film of the present invention is not particularly limited, and a resin can be selected according to the use, but polyester is particularly preferable for magnetic tape. The polyester is not particularly limited, but at least one structure selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, and ethylene 2,6-naphthalate unit. Particularly preferred when the unit is the main constituent. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Two or more kinds of polyesters may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

The particles contained in the outermost layer are not limited in material as long as they satisfy the particle size ratio described below and the strength at the time of 10% deformation. In order to obtain strength, organic polymer particles are preferable. The soft particles having a predetermined strength at 10% deformation may be porous inorganic particles such as silica, and the porous particles may have a predetermined particle size ratio.

The organic polymer particles in the present invention include, for example, polystyrene or crosslinked polystyrene particles, styrene / acrylic and acrylic crosslinked particles, vinyl particles such as styrene / methacrylic and methacrylic crosslinked particles, benzoguanamine / formaldehyde, and silicone.
However, the particles are not limited to these, and at least a part of the parts constituting the particles is a film base resin, for example, polyester. However, any particles may be used as long as they are insoluble organic polymer particles. Preferably, a monovinyl compound (A) generally having only one aliphatic unsaturated bond in the molecule and a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent are used. Polymers may be mentioned.

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

As the compound (A), those having the structural formula of the following chemical formula 1 are desirable, and those having R ₂ having 4 or more carbon atoms are preferable for imparting a flexible segment. Particularly preferably, when the compound (A) has a structure of a polymer with a single component, its glass transition temperature is preferably not higher than the glass transition temperature of the polyester used in the present invention,
Further, it is desirable that the glass transition temperature thereof is 50 ° C. or lower, preferably 20 ° C. or lower, more preferably 0 ° C. or lower. Specifically, acrylic acid ester monomers such as butyl acrylate, octyl acrylate, dodecyl acrylate, hexadecyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, se.
c-butyl methacrylate, hexyl methacrylate,
Methacrylic acid ester monomers such as hexadecyl methacrylate and 2-ethylhexyl methacrylate are preferably used.

[0013]

[Chemical 1] R ₁ : H or CH ₃ R ₂ : H or an alkyl group having 1 or more carbon atoms

Examples of compound (B) are divinylbenzene compounds, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
Alternatively, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol diacrylate,
Examples thereof include polyvalent acrylates and methacrylates such as 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate. Of the compound (B),
In particular divinylbenzene, ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate
Is preferably used.

Each of these compounds (A) and (B) is 2
It is also possible to use a mixture of two or more species. In addition, in order to produce the organic polymer particles having a relatively low strength as in the present invention, the ratio of the pure crosslinking agent in the organic polymer particles is 1 to 6.
It is desirable that the amount is 0% by weight, preferably 2 to 50% by weight, more preferably 5 to 40% by weight. Furthermore, components other than the compounds (A) and (B) may be added, and the heat resistance,
You may perform coating with a trace amount of inorganic substances in order to improve dispersibility, and surface treatment for improving affinity.

Preferred examples of the composition of the organic polymer particles of the present invention include butyl acrylate-divinyl benzene copolymer, methyl methacrylate-divinyl benzene copolymer, octyl acrylate-divinyl benzene copolymer, 2-ethylhexyl acrylate-divinylbenzene copolymer, 2-ethylhexyl acrylate
Examples thereof include crosslinked polymer fine particles such as a to-ethylene glycol dimethacrylate copolymer, a hexyl methacrylate-divinylbenzene copolymer copolymer, and a 2-ethylhexyl methacrylate-divinylbenzene copolymer.
Further, fine particles may be produced by a three-component system such as a styrene-butyl acrylate-divinylbenzene copolymer and a styrene-hexyl methacrylate-divinylbenzene copolymer.

The method for producing the organic polymer particles of the present invention will be described by taking the method for producing the crosslinked polymer particles as an example. For example, the compounds (A) and (B) are mixed and the following emulsion polymerization is performed. There is a way. (A) Soap-free polymerization method, that is, a method in which an emulsifier is not used or an extremely small amount of an emulsifier is used for polymerization. (B) A seed polymerization method in which polymer particles are added to the polymerization system prior to emulsion polymerization and then emulsion polymerization is carried out. (C) A core-shell polymerization method in which a part of the monomer component is emulsion polymerized and the remaining monomers are polymerized in the polymerization system. (D) JP-A-54-97582 and JP-A-54
-126288, the polymerization method by Eugerstat et al. Of the above, the methods (c) and (d) are particularly preferable for producing soft particles.

When the contained particles are organic polymer particles, the heat resistant temperature is not particularly limited, but is 300 ° C. or higher, preferably 330 ° C. or higher, more preferably 360 ° C.
The above cases are more preferable in obtaining the effects of the present invention.

The contained particles in the present invention are originally non-round (not spherical) deformed particles, and the particle size ratio (ratio of maximum diameter and minimum diameter) (r) before being contained is in the range of 1.1 to 10. It is desirable that r is in the range of 1.2 to 8, and particularly preferably in the range of 1.3 to 5 in order to improve slip stability and abrasion resistance. By setting the particle size ratio to 1.1 or more, high protrusion stability and slipperiness can be obtained, the generation of voids is extremely small, and particles are unlikely to fall off. When the particle size ratio exceeds 10, the projection forming property deteriorates and it becomes difficult to form high density projections. Particle size ratio (r ') measured after stretching the film
Is preferably larger than the particle size ratio (r) before being contained, and particularly preferably r '/ r is in the range of 1.1 to 5. The shape of the particles is not particularly limited, but specific examples thereof include a rod shape, an ellipse shape, and a plate shape.

The strength of the contained particles of the present invention when deformed by 10% (hereinafter also referred to as S ₁₀ ) is 10 kgf / mm ² or less. Chipping of the film surface, to the particular sliding stability good, the upper limit is 8 kgf / mm ² in S _10, preferably 6 kgf / mm ^2, still more preferably is 4 kgf / mm ^2. In particular, organic polymer particles having an S ₁₀ value of less than 3 kgf / mm ² and excellent affinity with polyester are preferable because the flatness is greatly improved.

Here, the S ₁₀ of the particles is an index of the softness of the particles, and is obtained by measuring the deformation behavior of the particles by an external force, for example, by the method shown in FIG. (In the illustrated example, the particle shape is elliptical). In the method shown in FIG. 1, first, particles are dispersed on the lower pressurizing indenter 1 and one fine particle 3 is fixed between the upper pressurizing indenter 2 and the lower pressurizing indenter 1. Then, the load force is applied at a constant increase rate, and the deformation amount of the fine particles and the load force are automatically measured.
From the load P (kgf) at the time of% deformation, according to the following formula, S ₁₀
(This measurement is performed 10 times in total, and the average value of 10 times is defined as S _10. ) is calculated. S = 2.8 P / πd ² (kgf / mm ² ), where d represents the equivalent circle diameter (mm) of the particles.

Such particles are contained in the outermost layer of the laminated film to form a predetermined protrusion on the film surface. The average particle size of these particles is 0.00 in order to optimize the slipperiness of the film, the height of protrusions formed on the surface and the height distribution.
It is preferably in the range of 1 to 3 μm, more preferably in the range of 0.005 to 2 μm, and further preferably 0.0.
It is in the range of 1 to 1 μm. If the average particle size is less than 0.001 μm, the height of the protrusions formed on the surface is low, and the slipperiness is insufficient. If the average particle size exceeds 3 μm, the protrusion height becomes too high, resulting in abrasion during high-speed traveling. There is a risk.

The content of the particles may be basically set so as to satisfy the number of protrusions described later, but a preferable content is 0.005 with respect to the layer containing the particles.
To 3% by weight, more preferably 0.01 to
It is 2.5% by weight. If the content is less than 0.005% by weight, the density of the protrusions formed becomes too small, and it becomes difficult to satisfy the number of protrusions described below. If it exceeds 3% by weight, the amount of particles becomes too large and the abrasion resistance may deteriorate.

The method of adding the particles of the present invention to the film-forming base material is not particularly limited. For example, it is added as a glycol slurry of the polyester raw material during the polyester production step, that is, ester exchange, esterification, polycondensation reaction,
It can be added during the kneading of the molten polyester. The appropriate slurry concentration is about 0.5 to 20% by weight.

The low-strength and soft particles as described above are
By including it in the outermost film layer on at least one side, projections are formed on the film surface by the particles.
The formed protrusions can have appropriate height and density by controlling the height distribution and the number of protrusions as described below. Further, since the formed protrusion itself is soft, even when the magnetic layer is applied for a magnetic tape, wound and cured, for example, the transfer of the protrusion to the magnetic surface is extremely unlikely to occur.

The height distribution and the number of projections formed by the particles are regulated. The relative standard deviation of the projection height distribution must be 1.0 or less, and if it exceeds this, a uniform projection height cannot be obtained, and particles (projections) may easily fall off (deterioration in abrasion resistance). The slipperiness may deteriorate.

The number of protrusions is 5000 / mm
^It is necessary to have ² or more, and if it is less than this, the friction coefficient of the surface becomes high and the running property (sliding property) may deteriorate. That is, since the particles in the present invention are originally deformed particles having the above-mentioned particle size ratio, if the number of protrusions is too small, the coefficient of friction may become too high. is there.

In the film of the present invention, different polymers may be blended within the range that does not impair the object of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers and the like may be blended. The organic additives may be added to the extent that they are usually added.

Further, in order to control the particle size ratio of the particles, the component concentration, temperature, stirring condition and the like may be changed at any stage of the polymerization. Further, in order to control the particle size ratio, the synthesized particles may be subjected to a treatment such as crushing.

Next, the method for producing the film of the present invention will be described by taking a biaxially oriented polyester laminated film as an example. First, as a method for incorporating organic polymer particles into polyester, for example, a method in which ethylene glycol, which is a diol component, is dispersed in the form of a slurry, and this ethylene glycol is polymerized with a predetermined dicarboxylic acid component, is preferable. When adding the organic polymer particles, for example, the dispersibility of the particles is very good if the particles are added without drying the water sol or alcohol sol obtained at the time of synthesis.
It is possible to improve both the high-speed sharpness and the electromagnetic conversion characteristics. Further, a method of directly mixing a water slurry of organic polymer particles with a predetermined polyester pellet, supplying the mixture to a vent type twin-screw kneading extruder and kneading into polyester is also very effective in further improving the effect of the present invention. Is. As a method for adjusting the content of particles, there is a method of preparing a high-concentration particle master by the above method, and diluting it with a polyester that does not substantially contain particles during film formation to adjust the content of particles. It is valid.

Next, the polyester pellets are used to form a polyester film having a laminated structure of two or more layers. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried and then fed to a known melt laminating extruder, extruded into a sheet from a slit die, and solidified by cooling on a casting roll. At the very least make an unstretched film. That is, two or more extruders, two or more layers of manifolds or a merging block (for example, a merging block having a square merging portion) are used for stacking, and the
Sheets of more than one layer are extruded and cooled on a casting roll to make an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Further, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer layer side from the base layer side by 5 to 10 ° C.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, stretching in the longitudinal direction is divided into three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated, but usually the first step is 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows. (1) Average particle size After the particles were photographed with an electron microscope, the diameter of each particle was measured individually, and the particle equivalent spherical diameter corresponding to 50% by volume was determined and used as the average particle size.

(2) Particle size and maximum diameter, minimum diameter a. Particle size ratio (r) before addition to polyester When determining the average particle size, the maximum diameter and the minimum diameter of each particle were measured and the ratio was calculated. Further, the arithmetic mean is calculated to obtain the particle size ratio (r)
And b. Particle size ratio (r ') in the film The film was cut, the cross section in the longitudinal direction was observed, the maximum diameter and the minimum diameter of each particle were measured, and the ratio was calculated. Further, the arithmetic mean was obtained and the particle size ratio (r ') was obtained.

(3) Content of Particles A solvent that dissolves the film base material but does not dissolve the particles is selected, and the particles are centrifuged from the film base material. To do.
If necessary, pyrolysis gas chromatography, infrared spectroscopy, fluorescent X-ray analysis, Raman scattering, SEM-X
It can also be quantified using MA or the like. The inclusion of particles in the laminated portion and the base layer portion can be distinguished by scraping off each laminated portion. Further, if necessary, it can be calculated from the number of particles observed in each cross section using a TEM.

(4) Particle Strength (S ₁₀ ) Micro compression tester (MCTM-20 manufactured by Shimadzu Corporation)
1 type), load speed: 0.0145 gf / s,
The amount of deformation was measured by applying a load of 0 to 1 gf. Then, from the load (kgf) when the particles were deformed by 10%, S ₁₀ (this measurement was performed 10 times in total and the average value of 10 times was taken as S ₁₀ ) was calculated according to the above-mentioned formula (2). ..

(5) Average height, number of surface protrusions, and relative standard deviation of height distribution 2 detector type scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and cross-section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the flat portion of the film surface was measured as 0, and the measured height of the protrusion was measured by an image analyzer [IBAS2000, Carl Zeiss Co., Ltd.].
Manufactured] to reconstruct the film surface protrusion image. Next, the equivalent circle diameter is calculated from the area of each protrusion obtained by binarizing the protrusion portion in this surface protrusion image, and this is set as the average diameter of the protrusion. Further, the highest value among the binarized individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 500 times at different places to determine the number of protrusions, and the average value of the heights of all the measured protrusions was taken as the average height. In addition, the standard deviation of the height distribution was calculated 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 taken as the relative standard difference. The scanning electron microscope has a magnification of 1000 to
Select a value between 8000 times. In some cases, the height information obtained using a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200 times, use of a high resolution camera is effective) is used as the SEM. You may read and use it for the value of.

(6) Electromagnetic conversion characteristics A magnetic coating composition having the following composition is applied to the film by a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
(5 stages), temperature: 70 ° C., linear pressure: 200 kg / cm, followed by calendaring at 70 ° C. for 48 hours.
The above tape raw material was slit to 1/2 inch to prepare a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to obtain a VTR cassette tape. (Composition of magnetic paint) -Co-containing iron oxide: 100 parts by weight-Vinyl chloride / vinyl acetate copolymer: 10 parts by weight-Polyurethane elastomer: 10 parts by weight-Polyisocyanate: 5 parts by weight-Lecithin: 1 part by weight-Methyl ethyl ketone : 75 parts by weight Methyl isoptyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon black: 2 parts by weight Lauric acid: 1.5 parts by weight By using a household VTR for this tape, a TV test waveform generator was used. A 100% chroma signal was recorded, and the chroma S / N was measured from the reproduced signal with a color video noise measuring instrument.

(7) Scraping in fast-forwarding / rewinding (deck running scraping: abbreviated as FF / REW) A video tape assembled in a cassette in the same manner as in the measuring method (6), 250 m fast-forwarding and winding with a commercially available video deck. The return was repeated 50 times, and the amount was determined by the amount of shavings adhering to the tape running surface. It was judged visually by the following criteria, and the characteristics of the first grade and the second grade were good. Almost no shavings are adhering Class 1 Small amount of shavings is adhering Class 2 Large amount of shavings is adhering Class 3

(8) Heat-resistant temperature of particles Using TG-30M manufactured by Shimadzu Corporation, a temperature rising rate of 10 ° C. /
Thermogravimetric analysis was performed in nitrogen content, and the temperature at 10% weight loss was defined as the heat resistant temperature of the particles. The sample weight was 5 mg.

[0041]

EXAMPLES Next, the embodiments of the present invention will be described based on examples. Example 1 (Table 1) A water slurry of organic polymer particles composed of a butyl acrylate (70 wt%)-divinylbenzene (30 wt%) copolymer having a particle size ratio r of 2.0 and S ₁₀ of 3.9. And polyethylene terephthalate pellets were supplied to a vent type twin-screw kneading extruder and mixed to obtain polyethylene terephthalate particle master pellets. The content of the organic polymer particles in the polyester was 1.0% by weight.

30 parts by weight of the above master pellets of organic polymer particles and 70 parts by weight of polyethylene terephthalate pellets containing no particles were mixed and fed to a vent type twin-screw kneading extruder 1 and melted at 280 ° C. I). Furthermore, another extruder 2 was prepared, and pellets containing no particles were dried under reduced pressure at 180 ° C. for 3 hours (3 Tor).
r), fed to the extruder and melted at 290 ° C. (polymer
II). These two polymers were respectively filtered with high precision and then laminated in a three-layer structure with a three-layer merging block having a rectangular laminated portion so that polymer II was present in the base layer portion and polymer I was in the two-sided surface laminated portion. After being extruded into a sheet form from a fish tail type die, it was wound around a casting drum having a surface temperature of 30 ° C. by an electrostatically applied casting method and cooled and solidified to form an unstretched film having a thickness of about 160 μm. The draft ratio at this time was 6.5.

This unstretched film is divided into three stages in the longitudinal direction, 1.2 times at 123 ° C., 1.45 times at 126 ° C., 1
Each was stretched 2.3 times at 14 ° C. This uniaxial film was stretched 3.5 times at 111 ° C. in the width direction using a stenter and heat-treated at 200 ° C. for 5 seconds under a fixed length to give a thickness of 13 μm.
m film was obtained. The particle diameter ratio r ′ of the organic polymer particles in the outermost layer of the obtained film was 2.3, and S ₁₀ was 3.
9 kgf / mm ² , the relative standard deviation of the height distribution of the formed protrusions is 0.5, and the number of protrusions is 26,000 / mm 2.
^{Was 2} .

When a magnetic layer was applied to this film to form a video tape, the transfer of the film surface projections to the magnetic surface was small, and the electromagnetic conversion characteristics were measured and the chroma S / N was +2.8 dB. Also, scraping the deck (FF /
The evaluation of (REW) showed that it was grade 1, and excellent running properties and abrasion resistance were obtained.

Examples 2 to 5 (Table 1), Comparative Examples 1 to 4 (Table 1) In the same manner as in Example 1, two types of particles contained in the outermost layer portion, having different particle size ratios and S ₁₀ were used. It was an axially oriented laminated polyester film. The type of particles contained in the outermost layer,
If the relationship between the particle size ratio and S ₁₀ is outside the range of the present invention, a film having good electromagnetic conversion characteristics and abrasion resistance could not be obtained.

[0046]

[Table 1]

[0047]

INDUSTRIAL APPLICABILITY In the biaxially oriented laminated film of the present invention, low-strength, soft particles having a predetermined particle size ratio are contained in the outermost surface layer, and soft surface protrusions having uniform height are formed at a predetermined density or more. As a result, excellent abrasion resistance and slipperiness can be exhibited even at high speeds. Especially for magnetic tape applications, there is no transfer of surface protrusions to the magnetic surface and excellent electromagnetic conversion characteristics. Can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a method for measuring the strength (S ₁₀ ) of particles in the present invention.

[Explanation of symbols]

 1 Lower pressure indenter 2 Upper pressure indenter 3 Fine particles

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Claims (2)

[Claims] 1. A biaxially oriented laminated film having a laminated structure of two or more layers, wherein the particle size ratio is 1.1 to 10 and the strength when the particles are deformed by 10% at least on the outermost surface layer part. Is 10 kgf / mm ² or less, the relative standard deviation of the height distribution of the surface projections of the outermost layer is 1.0 or less, and the number of projections is 5000 pieces / mm ² or more. Biaxially oriented laminated film. 2. The biaxially oriented laminated film according to claim 1, wherein the particles are organic polymer particles.