JPH05318582A - Biaxially oriented laminated film - Google Patents

Abstract

PURPOSE:To improve traveling properties and protrusion breaking strength, to reduce a decrease in picture quality and to improve dubbling performance of a biaxially oriented laminated film by forming the film in a laminated structure of three or more layers, incorporating special particles in an outermost layer of its one side surface, and simultaneously processing means such as enhancing intrinsic viscosity of the outermost layer part. CONSTITUTION:A biaxially oriented laminated film is formed of a laminated structure of at least three or more layers. In this case, particles are contained at least in an outermost layer of its one side surface of the film. The relationship between a mean particle size (d) (mum) of the particle and a thickness(t) of the outermost layer is so set as to satisfy 0.2d<= t<=10d. Further, the number of protrusions of the surface of the film at the outermost layer side is set to 3X10<3>-2X10<5>/mm<2>. Further, intrinsic viscosity of the outermost layer of at least one side surface is set to higher than that of an intermediate layer. Thus, fine protrusions on the surface of the film are optimized to improve traveling properties and protrusion breaking strength, a decrease in picture quality at the time of using it as a magnetic medium is reduced, and its dubbing performance is improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially oriented laminated film.

[0002]

2. Description of the Related Art As a biaxially oriented laminated film, for example, a biaxially oriented polyester film, a film in which polyester contains substantially spherical silica particles derived from colloidal silica is known (see, for example, Japanese Patent Laid-Open Publication No. Sho. 59
No. 171623).

However, with the increase in the process speed of the film processing process, particularly the magnetic layer coating / calendering / winding process in a magnetic medium application, the cassette assembling process, etc., the film surface, especially minute irregularities, is formed on the film by the contacting rolls or guides. There was a drawback that the film surface was easily scraped off (inferior scratch resistance). Also, in the conventional one,
With the speeding up of dubbing due to high-speed magnetic field transfer, etc.,
Image quality, that is, S / N
There was a drawback that the (signal / noise ratio) was also insufficient.

In order to solve such a drawback, the outermost layer of the laminated film is a thin layer, and particles having a relatively large particle diameter relative to the layer thickness are contained, and the layer thickness and the particle diameter of the particles are specified. A biaxially oriented laminated film has been proposed in which minute projections that are difficult to be scraped off are formed on the film surface according to the above relation (Japanese Patent Laid-Open No. 2-77431).

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and, at the same time, discloses in Japanese Patent Laid-Open No. 2-7
This is a further improvement of the technology proposed in Japanese Patent No. 7431, which further improves the runnability, scratch resistance, and breakage strength of protrusions by further optimizing the minute protrusions on the film surface, and has little deterioration in image quality when used as a magnetic medium. It is an object of the present invention to provide a biaxially oriented laminated film having good dubbing characteristics (hereinafter, sometimes referred to as excellent electromagnetic conversion characteristics).

[0006]

A biaxially oriented laminated film of the present invention for this purpose is a biaxially oriented laminated film having a laminated structure of at least three layers and containing particles in at least one outermost layer. Then, the relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the outermost layer is
0.2d ≦ t ≦ 10d, the number of protrusions on the film surface on the outermost layer side is 3 × 10 ³ to 2 × 10 ⁵ pieces / mm ² , and the intrinsic viscosity of at least one outermost layer portion is intermediate. It has a higher viscosity than that of the layer portion.

Further, another biaxially oriented laminated film of the present invention is a biaxially oriented laminated film having a laminated structure of at least three layers or more, containing particles in at least one outermost layer, and Relation between average particle diameter d (nm) and layer thickness t (nm) of outermost layer 0.2d ≦ t ≦ 10d
The number of particles having a particle size satisfying the above conditions is 3 × 10 ^{3 to} 1.5 × 10 ⁵ particles / mm ² , and the intrinsic viscosity of at least the outermost layer portion on one side is higher than the intrinsic viscosity of the intermediate layer portion. ..

First, the film of the present invention must have a laminated structure of at least three layers. If there are 3 or more layers,
Four or five layers may be used, but a three-layer structure is preferable because the effect of the present invention is further improved. However, a single-layer or double-layer structure film cannot satisfy the running property, scratch resistance, protrusion breaking strength and electromagnetic conversion characteristics, and cannot obtain good image quality and good dubbing resistance.

Next, in the film of the present invention, at least one of the above-mentioned layers constituting the film must be biaxially oriented. It is particularly preferable that all layers in the laminated structure of three or more layers are biaxially oriented. When all layers are non-oriented or uniaxially oriented, the characteristics of the present invention cannot be satisfied.

The polymer constituting the biaxially oriented laminated film of the present invention is not particularly limited, but polyester is preferred for magnetic media applications. The polyester is not particularly limited, but ethylene terephthalate, ethylene α,
β-bis (2-chlorophenoxy) ethane-4,4′-
It is particularly preferable when at least one structural unit selected from dicarboxylate and ethylene 2,6-naphthalate units 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.

In the outermost layer on at least one side of the biaxially oriented laminated film of the present invention, first, the particles have a relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the outermost layer. Is contained so that 0.2d ≦ t ≦ 10d. When t is smaller than 0.2d, the running property is deteriorated, and when t is larger than 10d, the image quality of a magnetic tape is deteriorated.

[0012] Then, primarily by the outermost layer containing particles, the film surface of the outermost layer side, the number 3 × 10 ³ to 2
× 10 ⁵ projections / mm ² are formed.

When the number of projections on the surface of the outermost layer side film is less than the above range, the coefficient of friction becomes high and good running performance cannot be obtained. On the other hand, when the number of protrusions is larger than the above range, the image quality of a magnetic tape is deteriorated and the scratch resistance is deteriorated.

In order to form such protrusions, the number of particles having a particle size satisfying the relation of the above formula is 3 × 10 ^{3 to} 1.5 × 1.
It is contained so as to be 0 ⁵ pieces / mm ² . in this way,
By setting the number of particles having a particle size satisfying a specific relationship between the particle size of the particles and the layer thickness of the outermost layer within a specific range, first, the desired minute projections are efficiently formed on the film surface by the contained particles themselves. To be done. The range of the number of particles is smaller than the range of the number of protrusions because the protrusions may be formed by the transfer effect from the intermediate layer or the like.

In the biaxially oriented laminated film of the present invention, the intrinsic viscosity of each layer is set so that the intrinsic viscosity of the outermost layer portion of at least one surface is higher than the intrinsic viscosity of the intermediate layer portion. By increasing the intrinsic viscosity of the outermost layer to be higher than the intrinsic viscosity of the intermediate layer, the scratch resistance of the outermost layer is kept high, the particles are more firmly retained in the layer, and the protrusion fracture strength is also improved. To be done.

In particular, the intrinsic viscosity of the laminated film as a whole is 0.60 or more, and the intrinsic viscosity of at least one outermost layer portion is 0.02 or more and less than 0.2 higher than the intrinsic viscosity of the intermediate layer portion. preferable. When the intrinsic viscosity of the laminated film as a whole is lower than 0.60, the thermal dimensional stability becomes poor and the skew characteristic of the magnetic recording medium deteriorates. Further, if the difference between the intrinsic viscosity of the outermost layer portion and the intrinsic viscosity of the intermediate layer portion is less than 0.02, the scratch resistance of the outermost layer portion is insufficient. Becomes too high, the filter for filtration may be damaged, and productivity is reduced.

In the film of the present invention, different polymers may be blended within a range not impairing 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.

Next, the method for producing the film of the present invention will be described for the case of polyester film. First, as a method for incorporating particles into the polyester, for example, a method is preferred in which particles are dispersed in a predetermined ratio in ethylene glycol, which is a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding particles, for example, when the particles are added without drying the water sol or alcohol sol obtained at the time of synthesis, the dispersibility of the particles is very good, and high-speed sharpness,
The electromagnetic conversion characteristics can both be improved. Further, a method in which an aqueous slurry of particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into polyester is also very effective for further improving the effect of the present invention. As a method of adjusting the content and number of particles, a high-concentration particle master is prepared by the above method, and the particle content is adjusted by diluting it with a polyester that does not substantially contain particles during film formation. The method is effective.

Next, the polyester pellets are used to form a polyester film having a laminated structure of three 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, using two or more extruders, three or more layers of manifolds or merging blocks (for example, a merging block having a square merging portion), a film layer forming each outermost layer and a film layer forming an intermediate layer are used. Are laminated, and three or more sheets are extruded from the die and cooled with a casting roll to prepare an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Also, the melting temperature of the extruder for extruding the polymer on the outermost layer side is 5% from the base layer side.
It is effective to lower the temperature by -10 ° C.

Next, the 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 and number of particles The polymer is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. The magnification of the SEM is approximately 2000 to 10,000 times, and the visual field for one measurement is appropriately selected from approximately 10 to 50 μm on each side. The volume average diameter d is obtained from the particle diameter and its volume fraction with the number of particles of 5000 or more by changing the observation location. d = Σd _i · Nv _i where d _i is the particle size and Nv _i is the volume fraction thereof. The number of particles is calculated from the volume fraction and converted per mm ² for those satisfying the relationship between the laminated thickness and the average particle diameter. When the particles are organic particles or the like and are significantly damaged by the plasma low temperature ashing method, the following method may be used. Using a transmission electron microscope (TEM), the cross section of the film is 30
Observe at 00-100,000 times. The section thickness of the TEM is set to about 1000 Å, the location is changed and 500 or more visual fields are measured, and the volume average diameter d is calculated from the above formula.

(2) Thickness of laminated polyester layer (thickness of outermost layer: t) Using a secondary ion mass spectrometer (SIMS), the highest thickness among the particles in the film in the range of 3000 nm from the surface layer to the depth The concentration ratio (M ⁺ / C ⁺ ) of the element due to the concentration of particles and the carbon element of polyester is defined as the particle concentration, and the analysis is performed in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration becomes 1/2 of the maximum value (this depth is deeper than the maximum value) was determined as the laminated thickness. The conditions are as follows. Measuring instrument Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12KV Primary ion current: 200nA Raster area: 400μm □ Analysis area: Gate 30% Measured vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A If the most contained particles in the range from the surface layer to the depth of 3000 nm are organic polymer particles, SIMS Is difficult to measure with XPS (X
The depth profile similar to the above may be measured by line photoelectron spectroscopy (IR), IR (infrared spectroscopy), etc. to obtain the laminated thickness, and the cross-sectional observation by an electron microscope or the like may be used to determine the state of change in particle concentration or the polymer. It is also possible to recognize the interface from the difference in contrast due to the difference and obtain the laminated thickness. Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(3) Number of projections on the film surface The film surface of the film surface was measured using a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Elionix Co., Ltd.]. The measurement value of the height of the projection when scanning is performed with the height of the flat surface set to 0 is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct a film surface projection image on the image processing apparatus. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is taken as the height of the projection, and this is calculated for each projection. This measurement was repeated 500 times at different places, and those having a height of 20 nm or more were used as protrusions to determine the number of protrusions. The magnification of the scanning electron microscope is selected to be 1000 to 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40-200
The height information obtained by using a double high-resolution camera is effective) may be used instead of the value of the SEM.

(4) Intrinsic viscosity [η] (unit: dl / g) The value calculated from the following formula is used from the solution viscosity measured at 25 ° C. in orthochlorophenol. That is, ηsp / C = [η] + K [η] ² · C, where ηsp = (solution viscosity / solvent viscosity) -1, C is the solvent
Dissolved polymer weight per 100 ml (g / 100 ml, usually 1.2), K is Huggins constant (0.343). Also,
Solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(5) Image quality (chroma S / N) 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 is slit into 1/2 inch and length 25
A length of 0 m was incorporated into a VTR cassette to obtain a VTR cassette tape. (Composition of magnetic paint) ・ Co-containing iron oxide (BET value 50 m ² / g): 100 parts by weight ・ ESREC A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer): 10 parts by weight ・ Nipporan 2304 (Nippon Polyurethane) Polyurethane Elastomer): 10 parts by weight Coronate L (Polyisocyanate made by Nippon Polyurethane): 5 parts by weight Lecithin: 1 part by weight Methyl ethyl ketone: 75 parts by weight Methyl isobutyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon Black: 2 parts by weight Lauric acid: 1.5 parts by weight Using a VTR for home use on this tape, a 100% chroma signal was recorded by a TV test waveform generator (TG7 / U706) made by Shibasoku, and the reproduced signal was shibasoku. Chroma S / N was measured with a color video noise measuring instrument manufactured by 925 D / 1.

(6) Runnability (friction coefficient μk) A film slitted into a tape having a width of 1/2 inch was used with a tape runnability tester SFT-700 type (manufactured by Yokohama System Laboratory Co., Ltd.). The film was run at 20 ° C. and 60% RH and the initial friction coefficient was determined by the following formula (film width was 1/2 inch). μk = 2 / πln (T ₂ / T ₁ ), where T ₁ is the inlet tension and T ₂ is the outlet tension. The guide diameter is 6 mmφ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 90 °, and the running speed is 3.
It is 3 cm / sec. When μk obtained by this measurement was 0.3 or less, the coefficient of friction was judged to be good, and when it exceeded 0.3, the coefficient of friction was judged to be poor. This μk is a critical point that affects the handleability when processing the film for magnetic recording media, capacitors, packaging, and the like.

(7) Scratch resistance The film is slit into a tape having a width of 1/2 inch, and a tape running tester TBT-300D / H type (manufactured by Yokohama System Laboratory Co., Ltd.) is used. , 20 ° C., 60% RH atmosphere, inlet side tension of 90 g, traveling speed of 250 m / min Video cassette guide pin (surface roughness Ra is 50 nm, R
At the time t, a guide pin made of stainless steel having a surface of 2500 nm is run at a winding angle of 60 degrees, a point 90 m from the beginning of the run is sampled, aluminum vapor deposition is performed, and the amount of scratches is visually checked as follows. It was judged according to the standard. No scratch at all ・ ・ ・ Although there are excellent scratches but the number is small ・ ・ ・ Good There are many deep scratches ・ ・ ・ Poor

(8) Dubbing resistance A magnetic coating composition 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 stages), temperature: 70 ° C, linear pressure: 200 kg / cm calendar
After the treatment, cure at 70 ° C for 48 hours. The above
The original fabric was slit into 1/2 inch to create 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 (BET value 50 m ² / g): 100 parts by weight ・ ESREC A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer): 10 parts by weight ・ Nipporan 2304 (Nippon Polyurethane) Polyurethane elastomer: 10 parts by weight Cotone L (polyisocyanate made by Nippon Polyurethane): 5 parts by weight Lecithin: 1 part by weight Methyl ethyl ketone: 75 parts by weight Methyl isobutyl ketone: 75 parts by weight Toluene: 75 parts by weight・ Carbon black: 2 parts by weight ・ Lauric acid: 1.5 parts by weight On this tape, a 100% chroma signal was recorded by a TV test waveform generator (TG7 / U706) made by Shibasoku using a home VTR. The chroma S / N was measured from the reproduced signal by a color video noise measuring instrument (925 D / 1) manufactured by Shiba Soku and was designated as A. Also, the master data recorded the same signal as above.
The same sample tape that was used to measure A using a magnetic field transfer type video software high-speed printing system (for example, Sprinter manufactured by Sony Magnesque Co., Ltd.)
The chroma S / N of the tape after dubbing to the unbaked pancake was measured in the same manner as above and designated as B. Chroma S / N decrease (AB) due to this dubbing is 3d
When it was less than B, dubbing resistance was excellent: when 3 dB or more and less than 5 dB, it was judged to be good, and when 5 dB or more, it was judged to be defective. Good is desirable, but good is practically usable.

(9) Breaking strength of protrusions A film slit into a tape having a width of 1/2 inch is repeatedly run on a guide pin using a tape running tester. (Guide material: SUS, surface roughness:
0.3S) A load of 200 g is applied to one end of the film, the film is run for 20 passes at a winding angle of 90 degrees and a running speed of 3.3 cm / sec, and then the amount of white powder adhering to the guide pins is evaluated. Was observed with a differential interference microscope to evaluate the damage of protrusions and the state of dropout of particles. Magnification 1
Observed in 10 fields of view at a magnification of 000, and the ratio of the locations where the particles fall out relative to the total number of protrusions is excellent (almost no particles are found), good (some particles are found, but the amount of white powder is very small), poor (A large number of particles dropped out and a large amount of white powder adhered) were used for the three-level evaluation.

[0030]

EXAMPLES Next, the embodiments of the present invention will be described based on examples. Example 1 (Table 1) The particles to be contained in the outermost layer were added in ethylene glycol.
Disperse 50 μm diameter glass beads as media,
After removing the glass beads, it was polymerized with terephthalic acid to obtain polyethylene terephthalate master pellets.

The above master pellets were diluted with polyethylene terephthalate pellets containing no particles at a predetermined ratio, adjusted to have predetermined viscosities, dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then extruded. Machine 1 and extruder 2 (for example, a vented twin-screw kneading extruder) were supplied and melted at 280 ° C and 290 ° C. These two polymers were respectively filtered with high precision, then laminated in a three-layer confluence block equipped with a rectangular laminated portion, extruded into a sheet form from a fish tail type die, and then applied with an electrostatic applied cast method. The film was wound around a casting drum having a surface temperature of 30 ° C. and cooled and solidified to prepare 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 divided into two stages in the width direction using a stenter, and stretched 3.7 times at 111 ° C. and 1.2 times at 113 ° C. to 200 at a fixed length.
The film was heat treated at 5 ° C. for 5 seconds to obtain a film having a thickness of 13 μm. The outermost layer portion laminated thickness t of the obtained film was 100.
0 nm, the stacking thickness t of the outermost layer and the average particle diameter d of the contained particles
The relationship t / d with was 1.5. The number of protrusions on both surfaces is the same, and the number of protrusions on the surface is 18,000 / mm ²
Met. Further, the number of particles having a t / d of 0.2 to 10 is 1
It was 4000 pieces / mm ² . The outermost layer has an intrinsic viscosity of 0.66 dl / g, and the intermediate layer has an intrinsic viscosity of 0.60 d.
It was 1 / g. Intrinsic viscosity as a whole is 0.61dl
/ G.

When the image quality of the VTR tape produced from this film was measured, it was +2.5 dB in chroma S / N. The running property (friction coefficient) of the film was also good at 0.24. Furthermore, when the scratch resistance, the dubbing resistance, and the protrusion breaking strength were evaluated, all were excellent. Thus, the relationship between the particles contained in the outermost layer and the laminated thickness, the number of particles satisfying the relationship, the number of surface protrusions are within the scope of the present invention, and the intrinsic viscosity of each layer is the relationship of the present invention. When the above conditions are satisfied, excellent image quality, running property, scratch resistance, dubbing resistance, and protrusion breaking strength are obtained.

Examples 2 to 5, Comparative Examples 1 to 4 (Table 1) In the same manner as in Example 1, the lamination thickness of the outermost layer, and the relation t between the lamination thickness t and the average particle diameter d of the contained particles. / D, the number of surface protrusions, the number of particles having t / d of 0.2 to 10 and the case where the intrinsic viscosity of each layer was changed, various biaxially oriented laminated polyester films were produced. The laminated thickness of the outermost layer, the relationship t / d between the laminated thickness t and the average particle diameter d of the contained particles, the number of surface protrusions, and the number of particles having t / d of 0.2 to 10 are within the scope of the present invention. However, when the intrinsic viscosity of each layer satisfies the relationship of the present invention, excellent image quality, running property, scratch resistance, dubbing resistance, and projection breaking strength were obtained in all cases (Examples 2 to 5). ), If any of the requirements, especially the intrinsic viscosity of each layer, does not satisfy the relationship of the present invention, even if some other conditions are within the scope of the present invention, the image quality, running property, scratch resistance, It was not possible to satisfy all of the dubbing resistance and the protrusion breaking strength (Comparative Examples 1 to 4).

[0035]

[Table 1]

[0036]

According to the biaxially oriented laminated film of the present invention, the outermost layer on at least one side of a laminated structure of at least three layers satisfies a specific particle average particle diameter and the layer thickness of the outermost layer. As described above, the number of surface protrusions or the number of particles having a particle size satisfying the relationship is set within a specific range, and the relationship between the intrinsic viscosity of the outermost layer and the intermediate layer is specified, so that the surface of the laminated film is not easily scraped. And it is possible to efficiently form the desired protrusions to obtain the desired surface morphology,
Excellent running properties, scratch resistance, and protrusion breaking strength can be exhibited, and excellent image quality and dubbing resistance for magnetic media can be obtained.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 4F 9:00 4F

Claims (3)

[Claims] 1. A biaxially oriented laminated film having a laminated structure of at least three or more layers, wherein at least one outermost layer on one side thereof contains particles, and the average particle diameter d (nm) of the particles.
And the layer thickness t (nm) of the outermost layer is 0.2d ≦
t ≦ 10d, the number of protrusions on the film surface on the outermost layer side is 3 × 10 ³ to 2 × 10 ⁵ pieces / mm ² , and the intrinsic viscosity of at least one outermost layer portion is intrinsic to the intermediate layer portion. A biaxially oriented laminated film characterized by having a higher viscosity. 2. A biaxially oriented laminated film having a laminated structure of at least three layers, wherein particles are contained in at least one outermost layer on one side, and the average particle diameter d (nm) of the particles.
And the layer thickness t (nm) of the outermost layer 0.2d ≦ t ≦ 1
The number of particles having a particle size satisfying 0d is 3 × 10 ^{3 to} 1.5 × 10
^A biaxially oriented laminated film, characterized in that the intrinsic viscosity is ⁵ pieces / mm ² , and the intrinsic viscosity of at least one outermost layer portion is higher than that of the intermediate layer portion. 3. The laminated film as a whole has an intrinsic viscosity of 0.60 or more, and an intrinsic viscosity of at least one outermost layer portion is 0.02 or more and less than 0.2 higher than an intrinsic viscosity of the intermediate layer portion. 1 or 2 biaxially oriented laminated film.