JP2897554B2 - Biaxially oriented film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 film containing particles having a Mohs' hardness of at least 8 on at least one side is known (for example, Japanese Patent Application Laid-Open No. 3-1941).

However, with an increase in the processing speed of a film processing step, particularly a magnetic layer coating / calendering and winding step in a magnetic medium application, a cassette assembling step, the contacting rolls and guides have a film surface, especially minute irregularities. There was a disadvantage that the film surface was 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.

The present invention solves such a problem, and in particular, the film surface is hardly scraped off in a high-speed process (hereinafter, referred to as excellent in high-speed scraping property), and hardly damaged (hereinafter, referred to as excellent in scratch resistance), and magnetic. When used as a medium, image quality during dubbing or the like is less reduced, that is, the electromagnetic conversion characteristics are good (hereinafter referred to as excellent in electromagnetic conversion characteristics).
An object is to provide a biaxially oriented laminated film.

[0005]

The biaxially oriented laminated film of the present invention for this purpose has a laminated structure of at least three layers, and has at least two kinds of particles 1 and 2 in the outermost layer on at least one side thereof. The average particle size d of the particles
(Μm) and the thickness t (μm) of the outermost layer are 0.2d ≦ t ≦ 10d, and the outermost layer side film surface is not more than 0.02 μm.
The number of protrusions at the upper height is 3 × 10 ³ to 1 × 10 ⁶ / m
m ² and the particles 2 are made of θ-type alumina having a primary diameter of 10 to 150 nm.

Further, another biaxially oriented laminated film of the present invention has a laminated structure of at least three layers, and has at least two types of particles 1 and 2 in the outermost layer on at least one side thereof. The relationship between the average particle size d (μm) of the particles 1 and the layer thickness t (μm) of the outermost layer is 0.2d ≦ t ≦ 10d, and the number of particles having a particle size satisfying the relationship of the expression is 3 × 10 ³
0.8 × 10 ⁶ particles / mm ² and the particles 2 are 1
It is made of θ-type alumina having a next diameter of 10 to 150 nm.

First, the film of the present invention needs to have a laminated structure of at least three layers. If there are three or more layers,
Four or five layers may be used, but a three-layer structure is preferable because the effects of the present invention are further improved. However, a film having a single-layer or two-layer structure cannot satisfy high-speed scraping properties and electromagnetic conversion characteristics.

Next, in the film of the present invention, it is necessary that at least one of the layers constituting the film is biaxially oriented. It is particularly preferable that all the layers of the three or more layered structure are biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the characteristics of the present invention are not satisfied.

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

In the biaxially oriented laminated film of the present invention, at least one type of particles 1
2 is contained. The particles 1 are composed of particles having a relatively large particle size, and form a projection on the surface of the outermost layer portion, and play a role in improving high-speed running while improving abrasion resistance. Particle 2
Is composed of particles having a smaller particle size than the particles 1 and mainly serves to reinforce the background of the outermost layer.

Although the type of the particles 1 is not limited, calcite-type calcium carbonate, vaterite-type calcium carbonate, colloidal silica, and organic particles are preferable. Due to the characteristics of the particle material, surface projections that are hard to be removed are efficiently formed. Calcite-type calcium carbonate exists as a natural material such as calcite having a hexagonal crystal form, and has a stable natural crystal form. Since no alteration or the like occurs, it is possible to stably contribute to the formation of surface projections even when subjected to a mechanical or thermal load such as stretching of a film. Vaterite-type calcium carbonate has a hexagonal crystal form and is found only in a kind of snail in nature, and is usually manufactured as a synthetic product. The synthesis is usually carried out in alcohol since it becomes calcite-type under heating or in the presence of water. Synthetic products are uniform in quality, but unstable (high activity)
High affinity with polyester etc. The density is 2.54g /
The birefringence is as small as 1.550 at about cm ³ . In particular, in the present invention, the uniform quality, the uniform particle size, and the high affinity with polyester and the like are effectively utilized, and the particles 1 form projections having a uniform height and which are difficult to be cut. Organic particles are also easily formed into a uniform particle size, and have an extremely high affinity for a film base material such as polyester.

The organic particles are not particularly limited, but include cross-linkable organic particles, silicone particles and the like. The degree of crosslinking of the crosslinked organic particles is preferably 51% or more, more preferably 60% or more, and still more preferably 75% or more. The term “crosslinking degree” as used herein refers to the weight percent of the crosslinking component in all the monomers constituting the particles.

As a preferable addition formulation of the particles 1 in the film of the present invention, there can be mentioned a combination of calcium carbonate particles and organic particles.

The average particle diameter of the particles 1 is preferably from 0.1 to 2 μm, more preferably from 0.2 to 1.5 μm. 0.
If it is smaller than 1 μm, the height of the projections formed is too low, and the effect of improving running properties is reduced. If it exceeds 2 μm, the height of the projections becomes too high, and the high-speed shaving property may be deteriorated.

The content of the particles 1 in the outermost layer is 0.005.
To 2% by weight, more preferably 0.1 to 1.0% by weight.
% By weight. If the content is less than 0.005% by weight, the number of surface projections becomes too small, so that the contact area of the background other than the projections becomes too large, the friction coefficient becomes high, and the running property deteriorates. Conversely, if it exceeds 2% by weight, the number of particles becomes too large, the layer itself becomes brittle, and the particles may easily fall off.

Since the particles 1 mainly play the role of forming surface protrusions, it is necessary to regulate the particle size distribution of the particles 1 in order to make the heights of the formed protrusions as uniform as possible. Therefore, the particle size distribution of the particles 1 needs to have a sharp distribution, and the relative standard deviation is preferably 0.6 or less.

The particles 1 are contained in at least one outermost layer to form projections on the surface of the layer. In order to form desired surface protrusions by containing the particles 1, it is necessary to specify a relative relationship between the particle diameter of the particles 1 and the thickness of the layer containing the particles 1. In the present invention, the average particle diameter d of the particles 1 (μm)
And the thickness t (μm) of the layer containing the particles 1 needs to be 0.2d ≦ t ≦ 10d. Preferably, 0.3d ≦ t ≦ 8d, and more preferably, 0.5d ≦ t ≦ 5d. By setting the relative relationship within this range, surface projections having a uniform height and a desired height are formed. This uniform formation of the desired surface projections improves the electromagnetic conversion characteristics as well as the high-speed cutting property.

The number of protrusions having a height of 0.02 μm or more on the surface of the outermost film containing the particles 1 is 3 × 10 ^3.
１1 × 10 ⁶ / mm ² , more preferably 5 × 1
0 ^{3 to} 5 × 10 ⁵ pieces / mm ² . 3 × 10 ³ pieces / m
If it is less than m ² , the running performance is inferior. On the other hand, if it is more than 1 × 10 ⁶ pieces / mm ² , the high-speed shaving property may be deteriorated.

Average particle diameter d of the outermost layer containing particles 1
(Μm) and the thickness t (μm) of the layer portion satisfy the following condition: 0.2 ≦ t ≦ 10d The number of particles is 3 × 10 ^{3 to} 0.8 × 10 ⁶ particles /
mm ² , more preferably 5 × 10 ^{3 to} 0.5 × 1
0 is ^six / mm ^2. 3 × 10 ³ particles / mm
^If it is less than ² , the running performance is inferior. 0.8 × 10
^If it is more than ⁶ pieces / mm ² , the high-speed shaving property may be deteriorated.

The particles 2 contained in the film of the present invention must be θ-type alumina. With respect to aluminum oxide, it is possible to obtain aluminum oxide having different crystal forms such as α-form, γ-, δ-, η-, χ-, and θ-forms depending on the type of raw material at the time of the production method, the firing temperature and the like. It is well known that these aluminum oxides are added as abrasive particles to a magnetic layer of a magnetic recording medium.

The present inventors have conducted intensive studies on many of these aluminum oxides, and as a result, have found that θ-alumina is used for particles 2 in at least one outermost layer of a biaxially oriented laminated film having a laminated structure of at least three layers. Only when this was the case, a film with significantly improved scratch resistance could be obtained.

The primary diameter of the θ type alumina is 10 to 150 nm
Needs to be More preferably, it is in the range of 15 to 100 nm. If it is less than 10 nm, it is difficult to disperse in the film, and a large agglomeration is formed, so that the background reinforcing effect is weak. If it is more than 150 nm, a surface projection forming effect appears, and high-speed shaving property may be deteriorated.

It is preferable that the θ-type alumina forms an aggregate in the film from the viewpoint of the background reinforcing effect. The size (secondary particle diameter) of the aggregate is not particularly limited, but is preferably in the range of 0.05 to 1.5 μm, and more preferably in the range of 0.1 to 1.0 μm.

The content of the .theta.-type alumina in the outermost layer is not particularly limited, but is preferably 0.05 to 2% by weight, more preferably 0.1 to 1% by weight. If the content is less than 0.05% by weight, the particle density in the layer becomes too low, so that the expected background reinforcing effect is hardly obtained. Content 2
If the content exceeds% by weight, the amount of particles becomes too large, and the layer may be brittle.

The θ-type alumina added to the film of the present invention may contain aluminum oxide having another crystal form, for example, α, γ, δ-type aluminum oxide as long as it is 15% or less.

The laminated portion and the intermediate layer of the film of the present invention may be blended with a different kind of polymer as long as the object of the present invention is not impaired, or may be an antioxidant, a heat stabilizer, a lubricant, an ultraviolet ray, or the like. Organic additives such as absorbents may be added to the extent that they are usually added.

The polymer constituting the intermediate layer of the biaxially oriented laminated film of the present invention is not particularly limited, but polyester is preferred for use in magnetic media. The polyester is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene 2,6
Particularly preferred is a case where at least one structural unit selected from naphthalate units is the main constituent. Among them, a polyester containing ethylene terephthalate as a main component is particularly preferable. In addition, two or more types of ponoesters may be mixed or a copolymer may be used within a range that does not impair the present invention.

The film of the present invention preferably has an in-plane birefringence Δn of -10 to -50 from the viewpoint of scratch resistance.

Next, the method for producing the film of the present invention will be described for the case of a polyester film. First, as a method for incorporating particles 1 and 2 into polyester, for example, particles 1 and 2 are separately dispersed in a predetermined ratio in the form of a slurry in ethylene glycol which is a diol component, and the ethylene glycol is mixed with a predetermined dicarboxylic acid component. The method of polymerizing is preferred. When adding particles, for example,
When the particles are added to a water sol or an alcohol sol obtained at the time of synthesis without drying, the dispersibility of the particles is very good, and high-speed scraping, scratch resistance, and electromagnetic conversion characteristics can be improved. Also, a method of directly mixing a water slurry of particles with predetermined polyester pellets, feeding the mixture to a vent-type twin-screw kneading extruder, and kneading the polyester into a polyester is very effective in further improving the effect 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 at the time of forming a film to adjust the content of particles is known. It is valid.

Next, a polyester film having a laminated structure of three 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 into a sheet from a slit die, and cooled and solidified in a casting roll. At least make an unstretched film. That is, two or three or more extruders, three or more layers are stacked using a manifold or a merging block (for example, a merging block having a square merging portion),
A sheet of three or more layers is extruded from a die and cooled by a casting roll to form 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 in the outermost layer laminated portion by 5 to 10 ° C. lower than that of the base layer side.

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, 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 raise the temperature after the second stage. The longitudinal stretching speed is 5,000 to 50,000% / m
The range of in 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 6.0 times is appropriate. The stretching speed in the width direction is 1
000-20,000% / min, temperature is 80-160 ° C
Is suitable. 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.

[0032]

[Method for measuring physical properties and method for evaluating effects] The method for measuring physical properties and the method for evaluating effects according to the present invention are as follows.

(1) Average Particle Size and Number of Particles 1 The polymer is removed from the film by plasma low-temperature ashing to expose the particles. The processing conditions are selected so that the polymer is ashed but the particles are not damaged as much as possible. The particles are observed with a scanning microscope (SEM), and the particle image is processed with an image analyzer. The magnification of SEM is about 2000 to 10000 times, and the visual field in one measurement is appropriately selected from about 10 to 50 μm on one side. The volume average diameter d is obtained from the particle diameter and its volume fraction by the following formula from 5000 particles or more at different observation points.

D = Σdi · Nvi where di is the particle diameter and Nv is its volume fraction.

The number of particles, which satisfy the relationship between the layer thickness and the average particle size, is determined from the volume fraction and is converted per mm ² .

When the particles are organic particles or the like and are significantly damaged by the plasma low-temperature incineration method, the following method may be used.

The cross section of the film is observed at a magnification of 3000 to 100,000 using a transmission microscope (TEM). The thickness of the section of the TEM is about 0.1 μm, measurement is made at 500 or more fields at different places, and the volume average diameter d is obtained from the above equation.

(2) Primary and Secondary Particle Sizes of θ-Alumina Particles The cross section of the film was measured using a transmission electron microscope (TEM) for 5 minutes.
Observe at a magnification of 0,000 or more. TEM section thickness is about 1
It is set to 00 nm, and the measurement is performed at 100 places or more in different places.
The primary particle size of the θ-type alumina particles is the average value of the equivalent circle equivalent diameter for the smallest unit of particles that cannot be divided, and the secondary particle size is for the aggregate.

(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. I do.
Also, if necessary, heat dispersion gas chromatography, infrared spectroscopy, fluorescent X-ray analysis, Raman scattering, SEM-XM
Quantification can also be performed using A 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.

(4) Particle Size Distribution of Particle 1 The average particle size was determined for 1000 particles by the method of (1) above, and the particle size distribution was represented by the relative standard deviation obtained by dividing the standard deviation by the average particle size. .

(5) Thickness of Laminated Polyester Layer (Thickness of Outer Layer: t) Using a secondary ion mass spectrometer (SIMS), the highest among particles in a film having a depth of 3000 nm from the surface layer. The concentration ratio (M ⁺ / C ⁺ ) between the element resulting from the particles and the carbon element of the polyester is defined as the particle concentration, and the analysis in the thickness direction is performed 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 which has once reached the maximum value starts to decrease again.
Based on this concentration distribution curve, the surface particle concentration is 1/1 of the maximum value.
A depth of 2 (this depth is deeper than the depth of the maximum value) was determined, and this was defined as the lamination thickness. The conditions are as follows.

Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measurement conditions Primary ion species: O ₂ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis Region: gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUN: 0.5 KV-3.0 A In the case where the particles contained most in the range from the surface layer to the depth of 3000 nm are organic polymer particles Is difficult to measure with SIMS, XPS while etching from the surface
(X-ray photoelectron spectroscopy), IR (infrared spectroscopy) or the like may be used to measure the same depth profile as above to determine the lamination thickness. The interface can be recognized from the difference in contrast due to the difference in polymer, and the lamination thickness can be determined. Further, after the laminated polymer is peeled off, the laminated thickness can be determined using a thin film step measuring device.

(6) Number and height of projections on the film surface A two-detector scanning electron microscope (Elionix, Inc.)
SM-3200) and cross section measuring device (P made by Elionix)
In MS-1), the height measurement value of the projection when scanning was performed with the height of the flat surface of the film surface set to 0, was sent to an image processing apparatus (IBAS-2000 manufactured by Carl Zeiss), and the projection of the film surface was placed on the image processing apparatus. Reconstruct the image. Next, the highest value among the individual protrusions obtained by binarizing the protrusions in this surface protrusion image is defined as the protrusion height,
This is determined for each projection. This measurement was repeated 500 times at different locations, and a projection having a height of 0.02 μm or more was determined as a projection, the number of projections was determined, and the average value of the measured projections was defined as the average height. As the magnification of the scanning electron microscope, a value between 1000 and 8000 times is selected. In some cases, a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens:
Height information obtained by using a high-resolution camera (40 to 200 times, effective use of a high-resolution camera) may be read and used as the SEM value.

(7) In-plane birefringence of the film The refractive index in the longitudinal direction n _MD and the width direction n _TD of the film is calculated as _follows :
It measured using the Appe refractometer, and calculated | required the difference of these two values by the following formula.

Δn = (n _MD −n _TD ) × 10 ³

(8) High-speed scalability One edge of a film is slit into a tape having a width of 1/2 inch and pressed 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: 100 g). The adhering height of the powder shaved on one blade was read with a microscope, and the shaved amount (μm) was determined. When the shaving amount is 180 μm or less, the shaving resistance is good, and when the shaving amount exceeds 180 μm, the shaving resistance is poor.

(9) Electromagnetic conversion characteristics A magnetic paint 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,
After performing a calendering process at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, 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 Parts-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 TV test waveform using a home VTR on this tape A 100% chroma signal was recorded by the generator, and the chroma S / N was measured from the reproduced signal by a color video noise measuring instrument.

(10) Scratch resistance The film obtained by slitting the film into a tape having a width of 1/2 inch is run on guide pins (surface roughness: 0.1 μm in Ra) using a tape running tester. (Running speed 25
0m / min, 1 pass, winding angle: 60 °
Running tension: 90 g). At this time, the scratches in the film were observed with a microscope, and if the number of scratches with a width of 2.5 μm or more was less than 2 per tape width, it was judged as excellent. Although excellent is desirable, even good is practically usable.

[0050]

Next, embodiments of the present invention will be described based on examples.

Example 1 Vaterite-type calcium carbonate having an average particle diameter of 0.6 μm as particles 1 was dispersed in ethylene glycol using glass beads having a diameter of 50 μm as a medium, and after removing the glass beads, polymerization was performed with terephthalic acid. A polyethylene terephthalate master pellet was used.

Next, θ-type alumina particles having a primary diameter of 32 nm as particles 2 and 1% by weight of polyacrylic acid with respect to the particles 2 were uniformly dispersed in ethylene glycol by the above-mentioned media dispersion method. In the same manner as in the above, a master pellet of particles 2 was obtained. The above-mentioned master pellet of the particle 1, the master pellet of the particle 2, and the pellet of polyethylene terephthalate containing no particles were added to the particles 1 and 2.
And 0.3% by weight, respectively, and supplied to the vented twin-screw kneading extruder 1,
Melted at 280 ° C. (Polymer I). Further, another extruder 2 was prepared, and pellets containing no particles were heated at 180 ° C.
And dried under reduced pressure (3 Torr) for 3 hours, and supplied to an extruder to be dissolved at 290 ° C. (Polymer II). Each of the two polymers was subjected to high-precision filtration, and then a 3
In the layer merging block, polymer II is laminated on the base layer and polymer I is laminated on the double-sided surface layer, and extruded into a sheet shape from a fishtail-type die. The film was wound around a casting drum at a temperature of 30 ° C., solidified by cooling, and an unstretched film having a thickness of about 160 μm was produced. The drum ratio at this time was 6.5.

The unstretched film was divided into three stages in the longitudinal direction, and 1.2 times at 123 ° C., 1.45 times at 126 ° C., and 11 times.
Each film was stretched 2.3 times at 4 ° C. This uniaxial film was divided into two stages in the width direction using a stenter, stretched 3.7 times at 111 ° C., 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 13 .mu.m. The outermost layer thickness t of the obtained film is 1.0
μm, the thickness t of the outermost layer and the average particle size d of the contained particles 1
And the relationship t / d was 1.67. The number of protrusions on the film surface was 1.5 × 10 ⁴ / mm ² . Furthermore, t /
The number of particles having d of 0.2 to 10 was 1 × 10 ⁴ particles / mm ² .

When the scratch resistance of this film was measured, it was excellent. Further, when the electromagnetic conversion characteristics were measured, the chroma S / N ratio was 2.6 dB. In addition, the high-speed scraping property was as good as 100 μm. As described above, the type of the particles contained in the outermost layer laminated portion, the relationship between the particle diameter, the content and the lamination thickness, the number of particles satisfying the relationship, when the number of surface protrusions is within the scope of the present invention, A film having good scratch resistance, electromagnetic conversion characteristics, and high-speed scraping properties was obtained.

Examples 2 to 3 and Comparative Examples 1 to 4 In the same manner as in Example 1, the type, particle diameter, content, and lamination thickness of the particles contained in the outermost layer laminated portion were variously changed. An axially oriented laminated polyester film was obtained. When the type of the particles contained in the outermost layer laminated portion, the particle size, the content, and the relationship between the laminated thickness and the like are not within the scope of the present invention, the scratch resistance, the electromagnetic conversion characteristics, and the high speed shaving property are both good. The film could not be formed.

[0056]

[Table 1]

[Table 2]

[0057]

According to the present invention, there is provided a biaxially oriented laminated film having a laminated structure of at least three layers and containing at least two kinds of particles 1 and 2 under specific conditions in at least one outermost layer. As a result, in a magnetic medium application, a biaxially oriented laminated film having good electromagnetic conversion characteristics and a film surface that is hardly scraped off and damaged easily in a high-speed process could be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI B29L 7:00 9:00 (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 1/00-35/00 C08J 7/04 B29C 55/12 G11B 5/704

Claims (2)

(57) [Claims] 1. A biaxially oriented laminated film having a laminated structure of at least three or more layers, the outermost layer on at least one side of the film contains at least two types of particles 1 and 2, and an average particle diameter d ( μm) and the thickness t (μm) of the outermost layer.
0.2d ≦ t ≦ 10d, and 0.02 μm or less of the outermost film surface.
The number of protrusions at the upper height is 3 × 10 ³ to 1 × 10 ⁶ / m
m ² , and the particles 2 are θ-type alumina having a primary diameter of 10 to 150 nm. 2. A biaxially oriented laminated film having a laminated structure of at least three or more layers, the outermost layer on at least one side of the biaxially oriented laminated film contains at least two kinds of particles 1 and 2, and has an average particle diameter d ( μm) and the thickness t (μm) of the outermost layer.
m) is 0.2d ≦ t ≦ 10d, and the number of particles having a particle size satisfying the relationship of the formula is 3 × 10 ³
0.8 × 10 ⁶ particles / mm ² and the particles 2 are 1
A biaxially oriented laminated film, which is a θ-type alumina having a next diameter of 10 to 150 nm.