JPH07241972A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PURPOSE:To enhance handling properties, winding characteristics and output characteristics, in a biaxially oriented laminated polyester film for a high density magnetic recording medium or the like, by specifying the surface characteristics of the film so that the single surface thereof is set to a magnetic surface at the time of use as a magnetic recording medium and the other single surface is set to a running surface. CONSTITUTION:In a biaxially oriented laminated polyester film composed of laminated constitution of at least two or more layers, the outermost layers A, B thereof are formed so as to satisfy specific conditions such that the layer A contains spherical particles with an average particle diameter of 0.05-0.5mum and is characterized by that the number of the coarse projections with H3 or more is 5/100cm<2> or less, and three-dimensional surface roughness(SRa) is 10nm or less and the layer B contains spherical particles with an average particle diameter of 0.1-1.0mum and is characterized by that three-dimensional surface roughness is 10-40nm and the ratio tB/dB of thickness tB and the average particle diameter dB is 0.2-10 and a calender shaping index is 200/m<2> or less. Further, the total thickness of the laminated film is set to 10mum or less and the F-5 value in the longitudinal direction thereof is set to 14kg/mm<2> or greater.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film, and more particularly to a biaxially oriented laminated polyester film having improved surface characteristics suitable as a film for high density magnetic recording media.

[0002]

As a biaxially oriented polyester film, a film containing spherical silica particles is known (for example, JP-A-59-171623).

[0003]

The conventional biaxially oriented polyester film described above has an increasingly flat surface in order to achieve high output characteristics and high density as a tape in high density magnetic recording medium applications. Becomes a thin film,
There are problems such as poor running properties, poor handling properties, and wrinkles when wound into a roll during the steps of film formation, slitting, and tape production. Further, if the surface of the film is roughened to solve the above problem, there is a problem that the image quality (output) is deteriorated. In particular, in the case of a film having a thickness of 10 μm or less, there is a limit in achieving high output characteristics while maintaining running, handling and winding characteristics.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have found that a film having a thickness of 10 μm or less has high running, handling, and winding characteristics as a magnetic recording medium. The present invention has been accomplished by finding a film that can simultaneously satisfy the output characteristics.

That is, according to the present invention, in a biaxially oriented laminated polyester film having a laminated constitution of at least two layers, one outermost layer (A layer) and the other outermost layer (B layer).
Satisfy the following conditions, and the biaxially oriented laminated polyester film has a total thickness of 10 μm or less and an F-5 value in the longitudinal direction of 14 kg / mm ² or more. .

Layer A: Contains spherical particles having an average particle diameter of 0.05 to 0.5 μ, and has 5 or more coarse protrusions of H3 or more / 100c.
m ² or less, three-dimensional surface roughness (SRa) is 10 nm or less.

Layer B: Contains spherical particles having an average particle size of 0.1 to 1.0 μ and a three-dimensional surface roughness (SRa) of 10 to 40.
nm, thickness (t _B ) and average particle diameter (d)
The ratio t _B / d _{B of B} ) is 0.2 to 10 and the calendar abrasion index is 200 pieces / m ² or less.

The present invention will be described in more detail below.

The polyesters constituting the layers A and B of the present invention include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene 2,6-dicarboxylic acid or esters thereof, ethylene glycol, diethylene glycol and tetramethylene glycol. It is a polyester obtained by polycondensation with glycols such as. Typical examples of such polyesters include polyethylene terephthalate and polyethylene-2,6-naphthalate. The polyester may be a homopolymer or may be a copolymer of a third component. In any case, in the present invention, a polyester having ethylene terephthalate units and / or ethylene-2,6-naphthalate units in an amount of 80 mol% or more, preferably 90 mol% or more is preferable.

The layer A surface of the film of the present invention is preferably a magnetic surface when used as a magnetic recording medium. Therefore, the particles in the layer A have an average particle diameter of 0.05 to 0.5 μm.
Substantially spherical particles, particularly spherical particles of 0.1 to 0.3 μm are preferably used. When the average particle diameter exceeds 0.5 μm, it is difficult to obtain high output characteristics when used as a magnetic recording medium. On the other hand, when the average particle size is less than 0.05 μm, dispersibility in polyester becomes difficult, and aggregates may be generated to form coarse protrusions of H3 or more described later.

The spherical particles having an average particle diameter of 0.05 to 0.5 μm include silica and organic particles (polystyrene particles, crosslinked polystyrene particles, crosslinked polyacrylic particles, crosslinked polyester particles, crosslinked polydivinylbenzene particles). Etc.), and crosslinked polydivinylbenzene particles are particularly preferable because they are more excellent in terms of coarse projections and abrasion resistance.

These particles may be combined in several sizes and types within a range satisfying the following coarse protrusions and three-dimensional surface roughness.

The layer A has coarse projections of H3 or more of 5 (pieces / 100 cm ² ) or less, preferably 2 (pieces / 100 cm ² ).
² ) or less, more preferably 0 (pieces / 100 cm ² ). Coarse protrusions of H3 or more are 5 (pieces / 100
If it exceeds 10 cm ^{2, the} number of dropouts in the magnetic recording medium increases, which is not preferable.

In the present invention, the number of coarse protrusions of H2 or less is not particularly limited, but the number of H2 level coarse protrusions is 100 (pieces / 100).
cm ² ) or less, preferably 50 (pieces / 100 cm ² ) or less, and more preferably 10 (pieces / 100 cm ² ) or less, and H1 level coarse protrusions are 300 (pieces / 100 cm ² ).
² ) or less, preferably 150 (pieces / 100 cm ² ) or less, and more preferably 80 (pieces / 100 cm ² ) or less. The use of non-spherical particles (amorphous particles) is not preferable because the particle size distribution is wide and coarse protrusions increase.

Furthermore, the three-dimensional surface roughness (SRa) of the A layer
Should be 10 nm or less, preferably 8 nm or less, and more preferably 5 nm or less. Three-dimensional surface roughness (S
When Ra) exceeds 10 nm, it is difficult to obtain high output characteristics when used as a magnetic recording medium.

The content of particles in the layer A is not particularly limited as long as it can satisfy the above SRa, but is usually 0.01 to 1.0.
%, Preferably 0.04 to 0.7% by weight, more preferably 0.07 to 0.4% by weight.

The B layer surface constituting the film of the present invention is preferably a running surface (non-magnetic surface) when used as a magnetic recording medium. Therefore, the particles in the B layer have an average particle diameter of 0.1 to 0.1.
1.0 μm substantially spherical particles, preferably 0.2-
Substantially spherical particles of 0.9 μm, more preferably 0.3-0.8 μm are used. Average particle size is 1.0 μm
If it exceeds the range, calendering is likely to occur in the manufacturing process of the magnetic recording medium, and since the total film thickness is as thin as 10 μm or less, the transfer and / or push-up action in the above steps may cause magnetic surface roughness. There is not preferable. On the other hand, if the average particle size is less than 0.1 μm, the surface formation required for improving running and handling properties is insufficient, which is not preferable.

As the spherical particles having an average particle diameter of 0.1 to 1.0 μm, the same particle species as those used for the layer A can be mentioned. In particular, crosslinked polydivinylbenzene particles are more preferable in terms of calendering resistance. These particles may be used in combination of several sizes and types within a range satisfying the following three-dimensional surface roughness, B layer thickness (t _B ) / average particle diameter (d _B ), and calendering index. Good. In particular, a combination of small-diameter particles / large-diameter particles is preferable because the running, handling, and winding characteristics are further improved. Incidentally, within the scope of achieving the object of the present invention, non-spherical particles, specifically silica, synthetic calcium carbonate,
A small amount of titanium dioxide, carbon black, a crosslinked organic polymer compound or the like may be used supplementarily.

Here, in the present invention, the thickness of the B layer (t
_B ) and the average particle diameter (d _B ) of the particles contained, t _B / d _B is 0.2 to 10, preferably 0.25 to 7,
More preferably, it should be 0.3 to 4. t _B /
If d _B exceeds 10, running, handling, and winding characteristics deteriorate, and in extreme cases, particles in the B layer may cause waviness on the surface of the A layer, resulting in a reduction in output when used as a magnetic recording medium. Not preferable. On the other hand, t _B / d _B
Is less than 0.2, particles are likely to fall off, and the calendering abrasion resistance may be deteriorated, which is not preferable.

The layer B has a three-dimensional surface roughness (SR
It is necessary that a) be 10 to 40 nm, preferably 13 to 30 nm, and more preferably 15 to 25 nm. SR
When a exceeds 40 nm, magnetic surface roughness occurs due to transfer and / or push-up action in the magnetic recording medium manufacturing process, and high output characteristics cannot be obtained, which is not preferable. on the other hand,
When SRa is less than 10 nm, running, handling and winding characteristics are poor, which is not preferable.

Further, the B layer has a calendering index of 20.
It should be 0 (pieces / m ² ) or less, preferably 150 (pieces / m ² ) or less, and more preferably 100 (pieces / m ² ). If the calendering index exceeds 200 (pieces / m ² ), frequent cleaning of the calendering device is required during the manufacturing process of the magnetic recording medium, which is not economical, and there are many dropouts when the magnetic recording medium is used, which is not preferable. In particular, the use of non-spherical particles (amorphous particles) is not preferable because the calendering index becomes high.

The content of particles in the B layer is not particularly limited as long as it can satisfy the above SRa, but is usually 0.1 to 8% by weight, preferably 0.3 to 5% by weight, more preferably 0.
5 to 3% by weight is good.

As described above, the laminated polyester film of the present invention exhibits remarkable effects when the total thickness is 10 μm or less, preferably 8.5 μm or less, more preferably 7 μm or less. In the case of a film having a total thickness of more than 10 μm, the handling and winding characteristics are sufficiently within the practical range and there is no problem even if both surfaces are relatively smooth.

Since the laminated polyester film of the present invention has a total thickness of 10 μm or less, the F-5 value in the longitudinal direction is 14 (kg / mm ² ) or more, preferably 16 (kg / mm ² ).
mm ² ) or more, and more preferably 17 (kg / mm ² ) or more. F-5 value in the longitudinal direction is 14 (kg
/ Mm ² ) is not preferable because running durability (tape edge damage, tape breakage) is reduced when used as a magnetic recording medium. In the present invention, the F-5 value in the direction perpendicular to the longitudinal direction (lateral direction) is not particularly limited, but is usually 10
(Kg / mm ² ) or more.

In the film of the present invention, it is sufficient that the A layer and the B layer are provided on both outermost layers of the film, and it does not matter whether or not one or more intermediate layers are present between the two layers. Since the total thickness of the film of the present invention is as thin as 10 μm or less, a two-layer structure having no intermediate layer is preferable from the viewpoint of film forming property.

Next, the method for producing the film of the present invention 2
The case of the layer structure will be described as an example.

First, as a method of incorporating particles into polyester, a method of dispersing in the form of a slurry such as ethylene glycol which is a diol component and polymerizing the slurry with a predetermined dicarboxylic acid component, or a form of particles in the form of a water slurry is used. Then, there can be mentioned a method of mixing with polyester which has been preliminarily polymerized and kneading and kneading using a vent type twin-screw extruder. Here, the slurry of particles such as ethylene glycol is heated to 140 to 200 ° C., particularly 180 to 20 ° C.
The method of heat-treating at a temperature of 0 ° C. for 30 minutes to 5 hours, particularly 1 to 3 hours, or adding a small amount of a water-soluble polymer dispersant to an aqueous slurry of particles to carry out dispersion stabilization treatment is a coarse projection of the present invention. Effective for obtaining a film excellent in calendering.

As a method for adjusting the content of particles, a high-concentration master is prepared by the above-mentioned method, and it is diluted with a polyester containing substantially no particles at the time of film formation to adjust the content of particles. Is effective.

The polyester raw material thus adjusted is dried if necessary.

Next, the following method is effective as a method for obtaining the biaxially oriented laminated film of the present invention.

The polyester raw material A forming the A layer and the polyester raw material B forming the B layer are fed to a known extruder for melt lamination and extruded into a sheet form from a slit die.
An unstretched film is prepared by cooling and solidifying on a casting roll. Here, using two extruders, a two-layer manifold or a merging block, polyester raw materials A and B are used.
Is preferred, and a two-layer sheet is extruded from a die and cooled on a casting roll to prepare an unstretched film.

Next, the unstretched film is biaxially stretched and heat set. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, but the sequential biaxial stretching method is preferable. Usually, it is stretched 2.5 times or more in the longitudinal direction at a temperature of 90 to 130 ° C., then stretched 3 times or more at a temperature of 80 to 160 ° C. in the width direction, and then heat treated at a temperature of 150 to 230 ° C. Stretching speed in the longitudinal direction is 5000 to 50000
% / Min is preferable, and the stretching rate in the width direction is 10
It is preferably from 0 to 20000% / min. Of course, after stretching in the longitudinal and width directions, it is re-stretched 1.03 to 2.5 times in the longitudinal direction and / or 13 at a temperature of 110 to 180 ° C.
A method of heat-treating after re-stretching 1.03 to 1.5 times in the width direction at a temperature of 0 to 200 ° C. is also used.

[0033]

[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) Film thickness 10 films of 1 m in length in the width direction, which were stacked, were measured at 10 places at equal intervals in the width direction using a micrometer, and the average value was divided by 10 to obtain the film. The thickness was used.

(2) F-5 value According to the method specified in ASTM D882-67, using an Instron type tensile tester, 25
It was measured at ℃ × 65% RH.

(3) Average Particle Size Polyester is removed from the film by a plasma ashing method to expose particles. As processing conditions, polyester is incinerated but particles are not damaged. This is observed with a SEM (scanning electron microscope), the image of the particles (light and shade of light generated by the particles) is linked to an image analyzer, and the observation location is changed to 5000 particles.
The following numerical processing is performed on the number of particles or more, and the number average diameter D obtained thereby is taken as the average particle diameter.

D = ΣDi / N (where Di is the equivalent circle diameter of the particles and N is the number).

(4) Lamination Thickness The cross section of the film was observed with a TEM (transmission electron microscope),
The interface is recognized from the change state of the particle concentration and the difference in contrast, and the laminated thickness is obtained.

(5) Coarse projections Two measurement surfaces are superposed and brought into close contact with each other by electrostatic force (loading voltage: 5.4 kV). The height of the coarse protrusion is determined from the Newton ring generated by the interference of the light of the coarse protrusion between the two films, and the coarse protrusion of the single ring is H1, the coarse protrusion of the double ring is H2, the triple protrusion of more than three rings. The coarse protrusion was set to H3 or more. The measurement area is 50 cm ² , and the number of pieces is 100 cm ² because two sheets are stacked. The light source used was a halogen lamp with a 564 nm bandpass filter.

(6) Three-dimensional surface roughness manufactured by Kosaka Laboratory Ltd. Surface roughness measuring machine (ET-30H
K), the tip radius of the stylus is 2 μm, the sampling pitch is 5 μm, the cutoff is 0.25 mm, and the vertical magnification is 50,000.
Double measurement, measurement speed of 100 μm / s, and recording number of 80 were measured.

(A) Three-dimensional center plane average roughness (SRa) The orthogonal coordinate axes X and Y are placed on the center plane of the roughness curved surface, the axis orthogonal to the center plane is the Z axis, and the roughness curved surface is f (X , Y) and the reference plane sizes Lx and Ly, SRa is obtained from the following equation.

[0042]

[Equation 1] (7) Calender abrasion index A film having a width of 270 mm was treated under the following conditions using a one-stage calendering apparatus consisting of a metal roll and an elastic roll, and the abrasion material attached to the elastic roll was washed with pure water. The number of shavings of 3 μm or more contained is counted (using a particle size distribution measuring device by He—Ne laser scattering).

3 converted per 1 m ^{2 of} passing film area
Good when the number of shavings of μm or more is 200 or less,
When the number exceeds 200, it is determined to be defective.

Total running length: 3000 m Running speed: 80 m / min Metal roll temperature: 95 ° C. Linear pressure: 200 kg / cm (8) Winding characteristics Film is wound up on a roll having a width of 1000 mm and a length of 10000 m (slit speed 250 m / min) The state of occurrence of vertical wrinkles, wrinkles and edge shifts of the roll was inspected in detail and judged as follows.

Excellent: No fresh wrinkles, no wrinkles and no edge shift.

Good: The end surface displacement was within 1 mm, and there were no wrinkles or wrinkles.

Defects: Vertical wrinkles or wrinkles are observed immediately after winding the roll or within 10 hours, or the end face deviation exceeds 1 mm.

Up to the good level, there is no practical problem. In addition, when the winding property is a good level or higher, the running property and the handling property are good, and there is a good correlation.

(9) Output characteristics, running durability A coating for a magnetic layer having the following composition, which has been thoroughly mixed and dispersed, is applied to the surface of the film A layer side, magnetic field oriented, dried and calendered, and then the side of the film B layer side. A coating composition for a bag having the following composition was applied to the composition, dried, and further cured at 60 ° C. for 48 hours to obtain a raw roll. Here, the magnetic layer is 2.0μ
The back layer was prepared to have a thickness of 0.4 μm. Finally, the roll-shaped raw fabric was slit into a width of 8 mm and incorporated into a half for 8 mm to obtain a measurement sample.

Coating composition for magnetic layer Ferromagnetic alloy powder 100 parts (coercive force = 1800 Oe, particle size = 0.25 μm, acicular ratio = 10/1) Vinyl chloride / vinyl acetate copolymer 15 parts Polyurethane resin 5 parts Poly Isocyanate 6.5 parts Myristic acid 2 parts Lecithin 1 part Aluminum oxide powder (average particle size: 0.2 μm) 4 parts Carbon black (average particle size: 0.09 μm) 1 part Methyl ethyl ketone 180 parts Toluene 40 parts Cyclohexanone 80 parts Back layer Coating composition for carbon black (average particle size: 0.03 μm) 100 parts Carbon black (average particle size: 0.28 μm) 4 parts Nitrocellulose 100 parts Polyurethane resin 20 parts Polyisocyanate 20 parts Methyl ethyl ketone 480 parts Toluene 20 parts (A) Output characteristics Sony-made EV-S33 There were recorded 100% chroma signals by a television testing wave generator was measured chroma S / N from the reproduced signal in a color video noise measuring instrument.

This chroma S / N is commercially available 8 mm
It was ranked compared to standard videotapes.

Output characteristics: ⊚ (difference +2 dB or more) Output characteristics: ○ (difference 0 to +2 dB) Output characteristics: × (difference 0 dB or less) (B) Running durability: 25 seconds using a Sony EV-S33 ℃, 75% RH
The tape edge damage when the tape was run under 50 passes was visually determined.

⊚: No edge damage.

◯: Edge damage is extremely slight, but practically no problem.

X: There is edge damage, which is a practical problem.

[0056]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

Example 1 An ethylene glycol slurry containing spherical silica particles derived from colloidal silica having an average particle diameter of 0.2 μm as particles was prepared, and the slurry was heat-treated at 190 ° C. for 2 hours, followed by dimethyl terephthalate and ester. A chip (A) containing a predetermined amount of the particles that have undergone exchange reaction and polycondensation
(Polyester raw material A forming layer A) was produced. Similarly, a chip (B) containing a predetermined amount of spherical silica particles of 0.3 μm (polyester raw material B for forming layer B)
Was manufactured.

Each of these chips was dried under reduced pressure at 160 ° C. for 5 hours, and then the chips (A) were fed to the extruder 1 for 2 hours.
Melt at 90 ° C., while supplying the chip (B) to the extruder 2 and melting at 280 ° C., both polymers are joined and laminated by a joining block, and a surface temperature of 25 ° C. is obtained by using an electrostatically applied casting method.
It is extruded on the casting drum, cooled and solidified, and
An unstretched film having a layer structure was obtained.

Here, by adjusting the discharge rate of each extruder, the total thickness and the thickness of layer B (ie, t _B
/ D _B ) was prepared.

The unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 95 ° C., then stretched 4.0 times in the width direction at 95 ° C. using a stenter, and further stretched in the longitudinal direction at a temperature of 140 ° C. After stretching 1.5 times again, at a constant length at 210 ° C for 5
Heat treatment was performed for 2 seconds to obtain a biaxially oriented laminated polyester film having a total thickness of 7 μm. The characteristics of the film are shown in Tables 1 and 2. The parameters were within the range of the present invention, and good film characteristics were obtained.

Example 2 An aqueous slurry of spherical cross-linked polydivinylbenzene particles having an average particle diameter of 0.3 μm was supplied to a vent type twin-screw kneading extruder,
A polyester film having a total thickness of 7 μm was prepared in the same manner as in Example 1 except that the particles were kneaded into polyester while extruding the water out of the system with a vent to produce chips (B ′) of the polyester raw material B forming the B layer. A biaxially oriented laminated polyester film was obtained. The parameters and properties of the film are listed in Table 1,
It was as shown in Table 2.

Example 3 In the same manner as in Example 2 except that the chip (B ′) used in Example 2 was diluted with a particle-free polyester raw material and used as the polyester raw material (A ′) for forming the A layer. A biaxially oriented laminated polyester film having a total thickness of 7 μm was obtained.
The parameters and characteristics of the film were as shown in Tables 1 and 2.

Example 4 A water slurry of spherical crosslinked polydivinylbenzene particles having an average particle diameter of 0.8 μm was supplied to a vent type twin-screw kneading extruder,
The particles were kneaded into polyester while pushing water out of the system with a vent to produce a chip (B ″) of polyester raw material B forming a B layer.

A biaxially oriented laminate having a total thickness of 6 μm was obtained in the same manner as in Example 3 except that the chip (B ″) was used as a part of the raw material for the layer B and the discharge amounts of the extruder 1 and the extruder 2 were changed. A polyester film was obtained, and the parameters and properties of the film were as shown in Table 1.

Example 5 Example 5 was repeated except that the chip (B ′) used in Example 2 was diluted with a particle-free polyester raw material to be used as the polyester raw material (A ′) for forming the layer A. A biaxially oriented laminated polyester film having a total thickness of 7 μm was obtained.
The parameters and properties of the film were as shown in Table 1.

Comparative Example 1 A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the B layer was diluted with a particle-free polyester raw material to have a three-dimensional surface roughness of 9 nm. As shown in Table 1, when the surface roughness of the B layer became smooth, the winding characteristics were poor.

Comparative Example 2 A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the particle content was adjusted so that the three-dimensional surface roughness of the A layer was 15 nm. As shown in Table 1, A
When the surface roughness of the layer increased, the tape output characteristics were poor.

Comparative Example 3 F-5 was carried out in the same manner as in Example 1 except that the re-stretching ratio in the longitudinal direction was 1.1 times and the discharge amount of the extruder 1 was adjusted.
A biaxially oriented laminated polyester film having a (MD) value of 12.0 kg / mm ² was obtained. As shown in Table 1, F-5
When the (MD) value became smaller, the winding characteristics, tape output, and tape running durability were poor.

Comparative Example 4 A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the discharge amount of the extruder 2 was adjusted to t _B / d _B of 0.15. Since the discharge amount of the B layer was low in this film, the total number of particles in the B layer was also reduced, and the three-dimensional surface roughness was 1
It became 3 nm. As shown in Table 1, when t _B / d _B was small, the calendering index was large and the tape output characteristics were also poor.

Comparative Example 5 The discharge amount of the extruder 2 was adjusted to t _B / d _B of 11 and the particle content of the B layer was adjusted to obtain a three-dimensional surface roughness of 30 n.
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the discharge amount of the extruder 1 was adjusted so that the total thickness was 7 μm. As shown in Table 1, when t _B / d _B increased, both winding characteristics and tape output characteristics were poor.

Comparative Example 6 The discharge amount of the extruder 2 was adjusted so that the three-dimensional surface roughness of the B layer was 4
The total thickness is 6.5 in the same manner as in Example 4 except that the thickness is 5 nm.
A biaxially oriented laminated polyester film of μm was obtained. Table 1
As shown in, the tape output characteristics were poor when the three-dimensional surface roughness of the B layer increased.

Comparative Example 7 A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that amorphous calcium carbonate having an average particle diameter of 0.3 μm was used as the particles constituting the layer A. As shown in Table 1, the number of coarse projections of H3 or more in the A layer is 7 (pieces / 10
0 cm ² ) and the tape output characteristics were poor.

Comparative Example 8 A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that amorphous titanium oxide having an average particle diameter of 0.3 μm was used as the particles constituting the layer B. As shown in Table 1, the calendar scraping index was as high as 330 (pieces / m ² ), and the tape output characteristics were also poor.

[0074]

[Table 1]

[Table 2]

[0075]

INDUSTRIAL APPLICABILITY The biaxially oriented laminated film of the present invention has one surface (A layer surface) serving as a magnetic surface when used as a magnetic recording medium and another surface (B layer surface) serving as a running surface. By defining, the high density magnetic recording medium using a film having a thickness of 10 μm or less as a support and the support thereof can simultaneously satisfy running, handling, winding characteristics and high output characteristics.

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Claims (5)

[Claims] 1. In a biaxially oriented laminated polyester film having a laminated constitution of at least two layers, one outermost layer (A layer) and the other outermost layer (B layer) satisfy the following conditions, and The total thickness of the biaxially oriented laminated polyester film is 10 μm or less, and the F-5 value in the longitudinal direction is 14
A biaxially oriented laminated polyester film having a weight of at least kg / mm ² . Layer A: contains spherical particles having an average particle diameter of 0.05 to 0.5 μm and has 5 or more coarse protrusions of H3 or more / 100 cm ² or less,
Three-dimensional surface roughness (SRa) is 10 nm or less. Layer B: spherical particles having an average particle diameter of 0.1 to 1.0 μm, a three-dimensional surface roughness (SRa) of 10 to 40 nm, and a thickness (t _B ) and the average particle diameter (d _{B of the} contained particles). ) Ratio t
_B / d _B is from 0.2 to 10, calendar abrasion index of 200
Pieces / m ² or less. 2. The biaxially oriented laminated polyester film according to claim 1, wherein the spherical particles of the A layer are silica and the spherical particles of the B layer are silica. 3. The biaxially oriented laminated polyester film according to claim 1, wherein the spherical particles of the A layer are silica and the spherical particles of the B layer are organic particles. 4. The biaxially oriented laminated polyester film according to claim 1, wherein the spherical particles of the A layer are organic particles and the spherical particles of the B layer are organic particles. 5. The biaxially oriented laminated polyester film according to claim 3, wherein the organic particles are crosslinked polydivinylbenzene particles.