JP3123665B2 - Biaxially oriented laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated film having four or more layers, and more particularly to a biaxially oriented laminated film capable of obtaining a desired outer layer surface irrespective of the properties of a central layer.

[0002]

2. Description of the Related Art As a biaxially oriented film in which fine irregularities are formed on the surface of a base film for a magnetic medium or the like, a film in which polyester contains substantially spherical silica particles caused by colloidal silica is known. (For example, JP-A-59-171623). However, in such a film, as the process speed of the film processing step, particularly the application of a magnetic layer, calendering and winding in a magnetic medium application, and the step of assembling a cassette, etc., increase, the contacting rolls and guides make the film surface, especially There is a disadvantage that the film surface having minute irregularities is easily scraped off. Further, the conventional one has a disadvantage that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality at the time of dubbing decreases due to the increase in dubbing due to high-speed magnetic field transfer or the like. Further, a thick film can be used as a base material of a floppy. However, the conventional film has a problem that tracking resistance and surface durability are insufficient.

[0003] In order to solve the above-mentioned drawbacks of the conventional film, the applicant of the present invention has previously made the film into a laminated structure and contained predetermined particles in the outer thin film.
By specifying the relationship between the type and particle size of the contained particles and the thickness of the thin film layer, it is possible to form uniform surface projections with the desired height, and it is difficult to scrape off even in high-speed processes. A series of proposals have been made for biaxially oriented films having excellent surface morphology with little reduction.

[0004]

In the biaxially oriented film proposed by the present applicant, the particles contained in the thin film layer on the surface form desired projections on the outer surface thereof. The central layer needs only a certain level of mechanical properties. However, if the center layer is made of a relatively messy polymer with many foreign substances, for example, unnecessary irregularities (for example, coarse projections) are formed on the surface of the center layer, which adversely affects the thin surface layer. In some cases, a desired uniform projection is not formed on the surface of the surface layer.

The present invention solves the above-mentioned problems of the conventional film, and in particular, the film surface is hardly scraped off in a high-speed process (hereinafter referred to as excellent in high-speed shaving property). It is desirable to achieve a desired surface form of the outer layer irrespective of the properties of the central layer, while achieving a film surface form with little reduction, that is, good electromagnetic conversion characteristics (hereinafter referred to as excellent in electromagnetic conversion characteristics). It is an object of the present invention to provide a biaxially oriented laminated film which can be used not only as a magnetic tape but also as a base material of a floppy disk.

[0006]

According to the present invention, there is provided a biaxially oriented laminated film according to the present invention, which comprises a C layer having a layer thickness of 0.1 μm or more in a biaxially oriented laminated film having a laminated structure of at least four layers. A layer B having a particle content of 2% by weight or less and a layer thickness of 0.2 μm or more is present on both sides, and a layer A is present on at least one outer surface of the layer B. The layer A has a particle content of 20% by weight. % Or less, the layer thickness is 0.005 to 3 μm,
The ratio d / t of the particle diameter d of the particles in the layer A to the thickness t of the layer A is 3 or less.

First, the biaxially oriented laminated film of the present invention needs to have a laminated structure of at least four layers. That is, layer B is laminated on both sides of layer C which is the central layer,
The layer A needs to be laminated on at least one outer surface side of the layer. A five-layer structure in which the A layer is stacked on both outer surface sides of both the B layers may be employed. At least A / B /
It is sufficient that there is a C / B lamination structure, and a lamination structure of six or more layers other than the four-layer and five-layer structures described above may be used. For a double-sided floppy or the like, a laminated structure of A / B / C / B / A is preferable.

In the film having such a laminated structure, the B layer located between the A layer and the C layer functions as a buffer layer for the C layer, and the surface properties of the C layer affect the A layer. Even if it is easy, it can be buffered (leveling down) so that the layer A is not adversely affected. In the case of the four-layer structure, the B layer on the side where the B layer itself constitutes the outermost layer has a function of covering the surface properties of the C layer so as not to appear directly as the outer surface. In a single-layer, two-layer, or three-layer structure, the above-mentioned A / B / C / B lamination structure cannot be obtained, so that a buffer B layer between the A layer and the C layer cannot be provided.

The material of the biaxially oriented laminated film of the present invention comprises:
Although not particularly limited, at least the outermost layer A,
Polyester is preferred from the viewpoints of surface projection formation, high-speed scraping, and electromagnetic conversion characteristics. The B layer and the C layer are also preferably polyester film layers from the viewpoint of mechanical properties and the like.

The polyester is not particularly limited, but may be at least one selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and ethylene 2,6-naphthalate units. It is particularly preferable when one kind of structural unit is used as a main component. Among them, a polyester containing ethylene terephthalate as a main component is particularly preferable. In addition, two or more types of polyesters may be mixed or a copolymer may be used within a range not to impair the present invention.

The layer A constituting the outermost layer of the biaxially oriented laminated film of the present invention is a layer having a small thickness and containing a predetermined amount of particles to uniformly form fine irregularities on the outer surface. It is necessary that the layer thickness is in the range of 0.005 to 3 μm. If the thickness is smaller than this range, the layer becomes too thin to appropriately hold the contained particles, and desired projections are hardly formed on the surface. Become. On the other hand, if it is larger than this range, the effect of forming surface projections due to the inclusion of particles is weakened, and it becomes difficult to uniformly form desired projections.

Further, the content of the particles needs to be 20% by weight or less. If the particle content is too large, the layer A itself may become brittle, and the high-speed scraping property may decrease.

Further, the ratio d / t between the particle diameter d of the particles in the layer A and the thickness t of the layer A needs to be 3 or less. By specifying the relationship between particle size and layer thickness in this way,
Desired fine protrusions are uniformly formed on the surface of the A layer, and high-speed scraping properties and electromagnetic conversion characteristics are improved. In addition, when used as a floppy substrate, tracking resistance and surface durability can be improved.

The type of particles contained in the layer A is not particularly limited, and may be any of inorganic particles, organic particles, and internally precipitated particles. However, in order to improve the high-speed scraping property, it is preferable to include particles having relatively high hardness. Such particles include, for example, inorganic particles having a relatively high Mohs hardness, for example, having a crystal form of α, β, γ, or δ.
Alumina, titanium nitride, zirconia, silica, or the like, which is a mold, can be used.

The layer thickness of the layer A, the content of the contained particles, and the ratio d / t between the particle diameter d of the contained particles and the thickness t of the A layer can be respectively set in appropriate ranges depending on the application. For example, in high-grade video applications, etc., the thickness of the A layer is 0.1 mm.
The range is preferably from 005 to 3 μm, the particle content is preferably from 1 to 20% by weight, and the d / t is preferably from 0.1 to 3. For general-purpose video applications, the thickness of the layer A is preferably 0.005 to 3 μm, the particle content is preferably 0.05 to 1% by weight, and the d / t is preferably 0.05 to 2. Furthermore, for more general purpose applications,
The thickness of the layer A can be in the range of 0.005 to 3 μm, the particle content can be less than 0.05% by weight, and the d / t can be in the range of 0.05 to 2.

The thickness of the layer B can be appropriately selected from the range of 0.2 μm or more depending on the state of the layer C. That is, as described above, since the layer B functions as a buffer layer for the layer A with respect to the layer C, the thickness and the like can be appropriately selected according to the application as long as the buffer effect is obtained. That is, the thickness can be made appropriately thick for a floppy disk or the like, and appropriately thin for a magnetic tape or the like. However, below 0.2 μm, the expected buffering effect cannot be obtained.

The layer B does not need to contain any particular particles, but if it contains particles in the range of 0 to 2% by weight,
The layer B itself is reinforced, which is preferable. The type of the contained particles is
The particles may be the same as those contained in the A layer, or may be different.

The layer C constitutes the central layer (core layer) of the biaxially oriented laminated film of the present invention. Therefore, its thickness is
It may be set appropriately within the range of 0.1 μm or more according to the application. Since the C layer constitutes the central layer, it preferably has a certain level of mechanical strength or more, depending on the application. For example, it is preferable that both the Young's modulus in the film longitudinal direction and the film width direction are 500 kg / mm ² or more.

The layer C is covered on both sides with a layer B, and the layer B functions as a buffer layer for the layer A in particular. Therefore, the layer C has a certain level of mechanical strength. It may be a layer made of a polymer in which foreign substances and the like are mixed. Therefore, the C layer can contain a recycled polymer. Here, the term “recycled polymer” refers to, for example, polyester films having a terminal carboxylic acid of 55 equivalents / 10 ⁶ g or more and a solution haze of 1 polymer.
8% or less.

In the film of the present invention, the surface roughness parameter P10 of the outermost layer A layer containing the particles is 2
It is preferably 50 nm or less. If it is larger than this value, high-speed scraping and durability may be reduced, and electromagnetic conversion characteristics may be reduced.

Further, in the film of the present invention, the relative standard deviation of the projection height distribution on the surface of the layer A is preferably 1.2 or less. If the value is larger than this value, undesired coarse projections and the like may be mixed, so that high-speed cutting properties may be reduced and electromagnetic conversion characteristics may be reduced. In the case of a floppy disk, the tracking resistance may be reduced.

In the film of the present invention, other kinds of polymers may be blended as long as the object of the present invention is not impaired, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. May be added to the extent that the organic additives are usually added.

It is particularly preferable that the polymer IV of the outermost layer laminated portion of the laminated film of the present invention is in the range of 0.4 to 0.9, because the high-speed shaving property is further improved. Further, it is highly preferable that the difference in polymer IV between the A layer and the B layer and between the B layer and the C layer be within 0.1 or less, because the high-speed scraping property and the durability are further improved.

Next, the method for producing the film of the present invention will be described, but the present invention is not limited thereto. First, as a method for incorporating particles into a predetermined polymer, for example, polyester, it is preferable to disperse the particles in, for example, ethylene glycol, which is a diol component, in the form of a slurry, and polymerize the ethylene glycol with a predetermined dicarboxylic acid component. When adding the particles, for example, if the water sol or alcohol sol obtained during the synthesis of the particles is added without drying once, the dispersibility of the particles is very good, and the high-speed scraping property and the electromagnetic conversion characteristics are both good. be able to. A method of directly mixing a water slurry of particles with predetermined polyester pellets, supplying the mixture to a vent-type twin-screw kneading extruder, and kneading the resulting mixture with polyester is also very effective for further improving the effects of the present invention. As a method of adjusting the content of particles, a method of preparing a high-concentration particle master by the above method and diluting it with a polyester substantially containing no particles during film formation to adjust the content of particles is known. It is valid.

Next, a polyester film having a laminated structure of four or more layers is formed using the polyester pellets. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, fed to a known extruder for melt lamination, extruded from a slit die into a sheet, and cooled and solidified on a casting roll. At least make an unstretched film. That is, three or more extruders, four or more layers, a manifold or a merging block (for example, a merging block having a square merging portion) are stacked, and 4
Extrude more than one layer of the sheet and cool it with a casting roll to make an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer flow path is effective. Further, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer laminated portion side by 5 to 10 ° C. than that on the base layer side. Also, extruding the sheet in three layers,
One or more layers may be further laminated on the sheet.

Next, the unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, the 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 unconditionally determined.
It is effective to set the temperature to 30 ° C. and to increase the temperature after the second stage. The longitudinal stretching speed is 5,000 to 50,000% /
A range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. Stretch ratio is 3.0
A range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The temperature is preferably in the range of 1000 to 20000% / min and the temperature is in the range of 80 to 160 ° C. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., particularly 1
The temperature is preferably from 80 to 200 ° C. and the time is preferably from 0.2 to 20 seconds.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows. (1) Average Primary Particle Size of Particles
Ultra-thin sections of about 00 ° are used, and the particles are observed using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.). When the particles are observed at a magnification of about 100,000, a minimum particle diameter (primary particle diameter) at which the particles cannot be further divided can be observed. This observation was performed for 100 visual fields, and the average value was defined as the average primary particle size.

(2) Content of Particles A solvent that dissolves the polymer (polyester) but does not dissolve the particles is selected, and the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content. . If necessary, pyrolysis gas chromatography, infrared spectroscopy, X-ray fluorescence analysis, Raman scattering, S
Quantification can also be performed using EM-XMA or the like. The content of the particles in the laminated portion and the base layer portion can be distinguished by shaving each laminated portion. Further, if necessary, it can be calculated from the number of particles observed in each cross section using a TEM.

(3) Thickness of the outermost layer Using a secondary ion mass spectrometer (SIMS), the concentration ratio (M) of the element resulting from the highest concentration of the particles in the film and the carbon element of the polyester. ⁺ / C ⁺ ) is defined as the particle concentration, and the analysis is performed in the depth (thickness) direction from the surface of the polyester A layer. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration that has once reached the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth at which the particle concentration of the maximum value becomes 1/2 [II]
(Where II> I) was taken as the lamination thickness. In addition, when the particles most contained in the film are organic polymer particles, it is difficult to measure by SIMS. Therefore, while etching from the surface, XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) or a confocal microscope is used. For example, the depth profile of the particle concentration may be measured, and the layer thickness may be obtained by the same method as described above. Furthermore, it can be obtained not from the above-mentioned depth profile but by observation of a cross section of a film or a thin film step measuring device.

(4) Surface roughness parameter P10 Light interference type three-dimensional surface analyzer (TOPO- manufactured by WYKO)
3D, objective lens: 40 to 200 times, use of a high-resolution camera is effective) to construct a film surface projection image on an image processing apparatus. In this surface projection image, the average of 10 points from the highest value of the projection portion was defined as P10. 2
The value was the average value of 0 measurements (unit: nm).

(5) Polymer IV The measurement was carried out at 25 ° C. using o-chlorophenol as a solvent.

(6) Standard deviation of height distribution of surface protrusions A scanning electron microscope with two detectors [ESM-3200,
Elionix Co., Ltd.] and a cross section measuring device [PMS-1,
Elionix Co., Ltd.] and the image processing device [IBAS2000, Carl Zeiss Co., Ltd.]
To reconstruct the film surface projection image on the image processing apparatus. Next, a circle-equivalent diameter is determined from the area of each projection obtained by binarizing the projection portion on the surface projection image, and this is defined as the average diameter of the projection. The highest value among the binarized individual projections is defined as the height of the projection, and this is determined for each individual projection. This measurement is repeated 500 times in different places, and the height distribution of the measured protrusion is regarded as a normal distribution (normal distribution centered on a point having a height of 0) and approximated by the least squares method to obtain a height distribution. The standard deviation was determined. The magnification of the scanning electron microscope is 1000
Choose between ~ 8000x.

(7) Young's modulus Measured according to ASTM-D-882-81 (Method A). However, the measurement was performed at 25 ° C.

(8) High-speed scalability One edge of the film is pressed into the slit of a tape having a width of 1/2 inch at an angle of 90 °, and the film is pushed in by 0.5 mm and run for 200 m (speed: 200 m / min, tension: 10
0 g). The adhering height of the powder shaved on one blade was read with a microscope, and the shaved amount (μm) was determined. This shaving amount is 180μ
When it is less than m, the abrasion resistance is good, and when it exceeds it, the abrasion resistance is poor.

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

(10) Tracking Deviation Test (Tracking Resistance) A floppy was recorded in an atmosphere at a temperature of 25 ° C. and a relative humidity of 20%, and the atmosphere was maintained at 25 ° C. and a relative humidity of 70%. 20% and 25 ° C relative humidity 7
Compare the 0% output envelope. The smaller the difference, the better the tracking characteristics. This difference is 3
When the value was equal to or more than dB, the tracking was poor and the evaluation was poor, and those within 3 dB were evaluated as excellent.

(11) Durability The same track magnetically recorded on the floppy obtained in the same manner as in the above (10) was scanned over 1,000,000 times at a relative traveling speed of 6 m / sec, and its output envelope was examined. Evaluation criteria were as follows: scratches generated on the surface of the magnetic layer were confirmed, and those in which the output envelope became unstable were regarded as defective. Those having no scratch on the surface of the magnetic layer and having a stable output envelope were evaluated as excellent.

[0038]

Next, embodiments of the present invention will be described based on examples. Example 1 (Table 1) Synthetic calcium carbonate particles A having an average particle diameter d of 0.8 μm
(Surface treatment with polyacrylic acid) was dispersed in ethylene glycol using glass beads having a diameter of 50 μm as a medium. After removing the glass beads, the mixture was polymerized with terephthalic acid to obtain polyethylene terephthalate pellets. The content of the particles A with respect to the polyester was 1.0% by weight.

30 parts by weight of the master pellets of the particles A and 70 parts by weight of pellets of polyethylene terephthalate containing no particles were mixed and supplied to a vented twin-screw extruder 1 to be melted at 280 ° C. (Polymer I) . Further, an extruder 2 is prepared, and a master pellet 10 of particles A is prepared.
Parts by weight and 90 parts by weight of a particle-free pellet are mixed and then dried at 180 ° C. for 3 hours under reduced pressure (3 Torr).
And fed to an extruder and melted at 290 ° C. (Polymer I
I). Further, another extruder 3 is prepared, 30 parts by weight of the recycled polymer and 70 parts by weight of the pellets containing no particles are mixed, and then dried under reduced pressure at 180 ° C. for 3 hours (3T).
orr) and fed to an extruder where it melted at 290 ° C. (Polymer III). After each of these three polymers is filtered with high precision, a five-layer merging block having a rectangular laminated portion is provided with polymer III on the central layer, polymer II on both sides thereof, and polymer I on the outermost laminated portion. After being extruded in the form of a sheet from a fishtail-type die, it is wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, cooled and solidified, and an unstretched film having a thickness of about 160 μm is obtained. Had made. The draft ratio at this time was 6.5.

The unstretched film is divided into three stages in the longitudinal direction, and is 1.2 times at 123 ° C., 1.45 times at 126 ° C.,
Each was stretched 2.3 times at 14 ° C. This uniaxial film is divided into two stages in the width direction using a stenter, stretched 3.7 times at 111 ° C. and 1.2 times at 113 ° C., and stretched 200 times at a constant length.
C. for 5 seconds to obtain a film having a thickness of 15 .mu.m. The outermost layer thickness t of the obtained film is 1 μm.
m and d / t were 0.8. Particles A on both surfaces of the surface layer
And the layer thickness were the same. Further, the polymer IV of the outermost layer laminated portion was 0.615, and the polymer IV of the intermediate buffer layer (B layer) was 0.605, and the difference was 0.010. The surface roughness parameter P10 of this film is
It was 100 nm.

When the electromagnetic conversion characteristics of this film were measured, it was +2.0. In addition, high-speed scraping is 90 (μ
m) and good. As described above, when the particle diameter, the content, and the layer thickness of the particles contained in each laminated portion are within the range of the present invention, it is possible to obtain a film having both good electromagnetic conversion characteristics and high-speed shaving properties. it can.

Examples 2 to 4 and Comparative Examples 1 to 6 (Table 1) In the same manner as in Example 1, the particle diameter, the content and the lamination thickness of the particles contained in the various layers were varied to obtain a biaxial An oriented laminated polyester film was obtained. When the relationship among the particle diameter, content, and layer thickness of the particles contained in each layered portion was not within the range of the present invention, it was not possible to obtain a film with good electromagnetic conversion characteristics and high-speed scraping properties.

[0043]

[Table 1]

Examples 5 and 6, Comparative Example 7 (Table 2) As a film for a floppy base material, a relatively thick biaxially oriented laminated polyester film was produced in the same manner as in Example 1. The large B layer provided a large buffering effect, and the large C layer contained a large amount of recycled polymer. As shown in Table 2, when each property is within the range of the present invention, excellent tracking resistance and durability are obtained, and the biaxially oriented laminated film of the present invention is a film excellent as a floppy base material. It turns out there is.

[0045]

[Table 2]

[0046]

According to the biaxially oriented laminated film of the present invention, a laminated structure of four or more layers is provided, a buffer layer B is provided between the center layer C and the outermost layer A, and a surface of the layer A is provided on the surface. The particles having a predetermined content and a predetermined particle size form uniform and hard-to-cut projections, so that a desired surface roughness form can be obtained. While exhibiting excellent electromagnetic conversion characteristics as above, the adverse effect on the layer A from the layer C is removed, and the surface form of the outermost layer can be secured to an optimum form according to the application. As a result, it is possible to obtain a magnetic tape excellent in abrasion resistance and electromagnetic conversion characteristics and a floppy excellent in tracking resistance and durability.

As described above, due to the presence of the B layer, C
Regardless of the properties of the layer, the outermost layer can be provided with the above-mentioned excellent properties, so that the center layer C layer can contain the recycled polymer without causing any problems, thereby improving the productivity. Can also be planned.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (6)

(57) [Claims] In a biaxially oriented laminated film having a laminated structure of at least four layers or more, both sides of a C layer having a layer thickness of 0.1 μm or more have a particle content of 2% by weight or less and a layer thickness of 0.2 μm or more. A layer A is present on at least one side of the outer surface of the layer B. The layer A has a particle content of 20% by weight or less, a layer thickness of 0.005 to 3 μm, and particles in the layer A. Wherein the ratio d / t of the particle diameter d to the thickness t of the layer A is 3 or less. 2. The biaxially oriented laminated film according to claim 1, wherein the C layer contains a recycled polymer. 3. The biaxially oriented laminated film according to claim 1, wherein both the Young's modulus of the C layer in the film longitudinal direction and the film width direction are 500 kg / mm ² or more. 4. The surface roughness parameter P1 of the surface of the layer A
4. The biaxially oriented laminated film according to claim 1, wherein 0 is 250 nm or less. 5. The biaxially oriented laminated film according to claim 1, wherein a relative standard deviation of a distribution of protrusion heights on the surface of the layer A is 1.2 or less. 6. The biaxially oriented laminated film according to claim 1, which has a laminated structure of A / B / C / B / A.