JP3048828B2 - Laminated biaxially oriented polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated biaxially oriented polyester film, and more particularly, to abrasion resistance, slipperiness, and the like.
Also, the present invention relates to a laminated biaxially oriented polyester film having excellent electromagnetic conversion characteristics when used as a magnetic tape, and particularly useful as a base film for an electromagnetic recording medium.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used in many applications such as magnetic tapes, electrical applications, photographic applications, metallizing applications and packaging applications because of their excellent properties. In particular, because of its high strength and elastic modulus, it is widely used as a base film for magnetic recording media, for example, video tapes, audio tapes, computer tapes, floppy disks, and the like.

[0003] In recent years, these fields of application have increased the recording density,
There is an increasing demand for higher quality, and accordingly, there is an increasing demand for a polyester film as a base to have a flat surface.

However, when the film surface is flat, the coefficient of friction of the film becomes high in, for example, a magnetic tape application, which causes problems such as poor running and scratches.

Further, when the film surface is flat, the film winding in the step of winding the film into a roll in the production of the film is remarkably deteriorated, and it is difficult to obtain a film roll having a good winding shape. It is necessary to further increase the film winding speed and increase the width in accordance with the increase in productivity. However, with the increase in speed and width, it becomes more difficult to obtain a film roll having a better winding shape. There is also a problem.

Therefore, a polyester film as a base is required to have excellent smoothness as well as flatness in order to obtain a good film winding form.

Conventionally, as a method for improving the lubricity of a film, a method of adding inorganic fine particles such as silicon oxide and calcium carbonate to a polyester, or a method of depositing fine particles containing calcium, lithium or phosphorus in a polymerization system at the time of polyester synthesis. A method has been proposed. In any of these methods, fine projections are formed on the film surface due to fine particles when the polyester is formed into a film, thereby improving the slipperiness of the film.

However, in the method of improving the slip property of the film by the projections of the fine particles as described above, the slip property is usually improved as the surface of the film is roughened.
On the other hand, due to the surface roughening, for example, in a magnetic recording medium application, the surface of the magnetic layer after applying a magnetic paint is rough,
Electromagnetic conversion characteristics tend to deteriorate.

As one method of simultaneously solving these contradictory flatness and slipperiness, one side of the film is flat and the other is rough and slippery. Methods using different laminated biaxially oriented films have been proposed.

[0010] In recent years, magnetic recording tends to be more and more dense, and the flat surface of the base film is required to be flatter. However, the processing speed of magnetic tapes has been increasing more and more in recent years, and even if a laminated biaxially oriented film having a different surface roughness as described above is used, the effect is becoming insufficient.

For example, when a magnetic layer is applied using a reverse coater, the smaller the friction coefficient between the application roll and the application surface side of the base film, the higher the speed can be achieved. However, it is necessary to roughen the coating surface side of the base film, which makes it impossible to meet the recent demand for high-density recording.

In general, the use of a die coater makes it possible to increase the speed of the magnetic layer coating process. In this case, if shaving powder is generated due to contact between the coating surface of the base film and the die, the shaving powder is removed. There is a problem that it causes dropout. Further, attempts have been made to increase the drying temperature of the coated web for the purpose of speeding up the drying process after the application of the magnetic layer.However, internal strain is generated in a sag where high tension is applied to the base film at a high temperature,
This causes a problem in that the coated web is wrinkled because it is intended to be restored in the subsequent curing step, and the product yield is reduced.

[0013]

The inventor of the present invention has conducted intensive studies to develop a film which simultaneously solves the above-mentioned problems, and as a result, the particles contained on the flat surface side of the laminated biaxially oriented film are solved. It has been found that it is essential that the hardness and the particle shape of the film satisfy a specific relationship, and that the heat shrinkage in the longitudinal direction of the film is within a specific range, and have reached the present invention.

[0014] Accordingly, an object of the present invention is to provide both flatness applicable to high-grade magnetic tape applications, slipperiness and abrasion resistance capable of responding to high-speed processing steps, and a rolled form of a coated web. Is to provide a good laminated biaxially oriented polyester film.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
According to the present invention, there is provided a laminated biaxially oriented polyester film in which at least two layers are laminated, and one of the exposed surface layers (layer A) of the film has an apparent Young's modulus (E :
(Kg / mm ² ) and 0.005 to 1% by weight of inert particles A having a particle size ratio (γ) satisfying the following formulas 1 and 2 and having an average particle size of 0.01 to 0.4 μm. , Surface roughness (Ra
_A : unit nm) is 1 to 10 nm, and the other surface layer (layer B) has a surface roughness (Ra _B : unit nm) satisfying the following formula 3, and is kept at 120 ° C. in the longitudinal direction of the film for 30 minutes. This is achieved by a laminated biaxially oriented polyester film having a heat shrinkage of 3% or less.

[0016]

Equation 1 150 <E Equation 2. (E / γ) ≦ 150 Equation 3. Ra _A <Ra _B <25 (nm)

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film forming properties, especially film forming by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Can be. As the aliphatic glycol, for example, a polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol or the like, or an alicyclic group such as cyclohexanedimethanol. Diols and the like can be mentioned.

In the present invention, a polyester containing alkylene terephthalate and / or alkylene naphthalate as a main component is preferably used.

Of these polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for at least 80 mol% of all dicarboxylic acid components, 80 of all glycol components
A copolymer in which at least mol% is ethylene glycol is preferred. At that time, not more than 20 mol% of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and also aliphatic dicarboxylic acids such as adipic acid and sebacic acid. An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid; In addition, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcin, and 2,2-bis (4-hydroxyphenyl) propane; Aliphatic diols having an aromatic ring such as 4-dihydroxydimethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol can also be used.

Further, the polyester in the present invention includes:
For example, aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those which copolymerize or combine a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component.

Further, the polyester in the present invention includes:
An amount in the range that is substantially linear, for example, 2 for the total acid component
Also included are those obtained by copolymerizing a tri- or higher functional polycarboxylic acid or polyhydroxy compound such as trimellitic acid or pentaerythritol in an amount of not more than mol%.

The above polyesters are known per se and can be produced by a method known per se.

The polyester preferably has an intrinsic viscosity of about 0.4 to about 0.9 as measured at 35 ° C. as a solution in o-chlorophenol.
0.7 is more preferable, and 0.55 to 0.65 is particularly preferable.

The laminated biaxially oriented polyester film of the present invention comprises at least two layers. The two layers of polyester may be the same or different, but are preferably the same.

In the present invention, one exposed surface layer (layer A) of the laminated biaxially oriented polyester film has an apparent Young's modulus (E : unit kg / mm ² ) and a particle size ratio (γ) of the following formula 1, 2 is satisfied and the average particle size is 0.01 to 0.4.
0.005 to 1.0% by weight of inert particles A
(Based on polyester).

[0026]

Equation 1 150 <E Equation 2. (E / γ) ≦ 150

Particle A has an apparent Young's modulus (E) of 150
(Kg / mm ² ) or less is not preferred because the coefficient of friction with the metal roll becomes too large. The apparent Young's modulus (E) is 160 (kg / mm ² ) or more, and 17
It is preferably 0 (kg / mm ² ) or more.

The apparent Young's modulus of the particles A (E : unit kg)
/ Mm ² ) and the particle size ratio (γ) must be 150 or less. When this ratio exceeds 150, the impact resistance of the particles is reduced, and for example, there occurs a problem that the particles easily fall off when the magnetic layer is coated with a die coater. This ratio is preferably 140 or less, particularly preferably 130 or less.

The average particle size of the particles A is from 0.01 to 0.1.
It needs to be 4 μm. This average particle size is 0.01 μm
If the amount is less than the above range, the slipperiness of the film becomes insufficient. On the other hand, if the average particle size exceeds 0.4 μm, shavings are likely to be generated, and electromagnetic conversion characteristics are undesirably reduced. This average particle size is preferably from 0.03 to 0.35 μm, more preferably from 0.05 to 0.30 μm.

Further, if the addition amount of the particles A is less than 0.005% by weight, the slipperiness is insufficient, which is not preferable. On the other hand, if the addition amount exceeds 1.0% by weight, the particles are remarkably overlapped, shaving powder is easily generated, and the electromagnetic conversion characteristics are undesirably deteriorated. This addition amount is 0.01 to
It is preferably 0.8% by weight, more preferably 0.02 to 0.6% by weight.

The type and shape of the particles A in the present invention are not particularly limited as long as they satisfy the above-mentioned characteristics, but particles obtained by agglomerating hard and fine primary particles are preferable. Specific examples include, for example, aluminum oxide, titanium oxide, silicon dioxide, zirconium oxide, potassium oxide, mullite, and the like.

In the present invention, the surface roughness (center line average roughness: Ra _A , unit nm) of the layer _A needs to be 1 to 10 nm. If it is less than 1 nm, sufficient slip properties cannot be obtained, and if it exceeds 10 nm, the electromagnetic conversion characteristics will be reduced, which is not preferable. The surface roughness (Ra _A ) is preferably 2 to 8 nm, more preferably 3 to 6 nm.

In the present invention, the other surface layer (layer B) where the laminated biaxially oriented polyester film is exposed must have a surface roughness (center line average roughness: Ra _B , unit: nm) satisfying the following equation (3). .

[0034]

Equation 3 Ra _A <Ra _B <25 (nm)

If Ra _B is smaller than Ra _A , the processing step and, for example, the handling of a magnetic tape, for example, will be very poor. On the other hand, when Ra _B is 25 (nm) or more, for example, in the curing step after coating the magnetic layer,
It is not preferable because the projections are transferred off to the surface of the magnetic layer and the surface of the magnetic layer is roughened to deteriorate the electromagnetic conversion characteristics.
The surface roughness (Ra _B ) of the B layer is less than 20 nm, and
It is preferably less than nm.

The above-mentioned surface properties of the layer B can be achieved by adding inert particles to the polyester forming the layer B and adjusting the average particle diameter, the content and the like.

The inert particles contained in the polyester include, for example, (1) granular polymer particles (eg, silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, polyamide resin, polyimide resin, polyamideimide resin, and crosslinked polyester). ), (2) metal oxides (eg, aluminum oxide, titanium oxide, silicon dioxide, magnesium oxide, zinc oxide and zirconium oxide), (3) metal carbonates (eg, magnesium carbonate and calcium carbonate), (4) metal oxides. Sulfates (eg, calcium sulfate and barium sulfate), (5) carbon (eg, carbon black, graphite and diamond), and (6) clay minerals (eg, kaolin, clay, and bentonite). Among these, silicone resin, cross-linked polystyrene,
Melamine-formaldehyde resins, polyamideimide resins, aluminum oxide, titanium oxide, silicon dioxide, zirconium oxide, calcium carbonate, barium sulfate, diamond and kaolin are preferred, especially silicone resins, crosslinked polystyrene, aluminum oxide, titanium oxide, silicon dioxide and carbon dioxide. Calcium is preferred. These may be used alone, but it is preferable to use a combination of two or more kinds of particles because the effect of the present invention becomes more remarkable.

The average particle size of the inert particles contained in the layer B is preferably 0.03 to 1.0 μm, more preferably 0.05 to 0.9 μm, and particularly preferably 0.1 to 0.8 μm.
μm. The preferred addition amount is 0.01 to 1.0% by weight, more preferably 0.04 to 0.8% by weight, and particularly preferably 0.05 to 0.7% by weight.

As a method for incorporating inert particles into the polyester of the layer A and the layer B, the particles are added before or during the polymerization of the polyester, or are pelletized after the polymerization is completed. When extruding, a method of sufficiently kneading with the polyester in an extruder may be used.

In the present invention, the laminated biaxially oriented polyester film must have a heat shrinkage of 3% or less when held at 120 ° C. in the longitudinal direction of the film for 30 minutes. If it exceeds 3%, the internal distortion of the base film ordered in the drying step after the application of the magnetic layer becomes too large, so that the coated web tends to wrinkle in the subsequent curing step. This heat shrinkage is preferably 2.9% or less, more preferably 2.8% or less.

In the present invention, the laminated biaxially oriented polyester film preferably has an air bleeding index of less than 5,000. More preferably less than 4000,
Particularly preferably, it is less than 3000. If the film air release index is too large, when winding the film roll,
Air tends to stay between the films, which is not preferable because it causes wrinkles of the film roll.

In the present invention, the laminated biaxially oriented polyester film preferably has a thickness of 3 to 20 μm, more preferably 4 to 16 μm. And the thickness of the layer B is 0.1
It is preferably from 3.5 to 3.5 μm, more preferably from 0.5 to 3.0 μm. When the laminated film has a laminated structure of three or more layers, the thickness of the layer A is 0.5 to 19 μm, and more preferably 0.8 to 19 μm.
It is preferably 19 μm, particularly preferably 1.0 to 19 μm. Various polyesters can be used as the polyester of the core layer (inner layer).

The laminated biaxially oriented polyester film of the present invention can be obtained by a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing an unoriented laminated film and then biaxially orienting the film. This unoriented laminated film can be manufactured by a conventionally accumulated method for manufacturing a laminated film. For example, a method of laminating a film layer forming a surface and a film layer forming an opposite surface or a core layer in a molten state or a cooled and solidified state of polyester can be used. More specifically, it can be manufactured by a method such as coextrusion / extrusion lamination.

The film laminated by the above-mentioned method can be further made in accordance with a conventional method for producing a biaxially oriented film, which is a biaxially oriented film. For example, polyester is melted and co-extruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. to have an intrinsic viscosity of 0.4 to 0.1.
An unstretched laminated film of 8 dl / g was obtained, and the unstretched laminated film was uniaxially (longitudinal or transverse) (Tg-1).
0) to (Tg + 70) ° C. (where Tg: glass transition temperature of polyester) is 2.5 times or more, preferably 3 times or more.
It is preferable that the film be stretched at a magnification of at least twice, and then stretched at a temperature of Tg to (Tg + 70) ° C. at a temperature of Tg to (Tg + 70) ° C. at a ratio of at least 2.5 times, preferably at least 3 times. Furthermore, you may extend | stretch again in a longitudinal direction and / or a horizontal direction as needed. As described above, the total stretching ratio is preferably 9 times or more, more preferably 12 to 35 times, particularly preferably 15 to 25 times as the area stretching ratio. Furthermore, the biaxially stretched film can be heat-set at a temperature of (Tg + 70) to (Tm-10) C (where Tm is the melting point of the polyester), and for example, preferably 180 to 250C. The heat setting time is preferably 1 to 60 seconds.

The various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Average particle size of particles: Centrifugal Particle S (Centrifugal Particle S) manufactured by Shimadzu Corporation
ize Analyzer). The particle size corresponding to 50% by mass is read from the integrated curve of the particles of each particle size and its abundance calculated on the basis of the obtained centrifugal sedimentation curve, and this value is defined as the above average particle size (see Book “Particle Size Measurement Technology "Published by Nikkan Kogyo Shimbun, 1975, pp. 242 to 247
reference).

(2) Surface roughness of film (center line average roughness: Ra) The center line average roughness (Ra) is measured according to JIS-B601. In the present invention, it is measured and measured under the following conditions using a stylus type surface roughness meter (SURFCORDER SE-30C) of Kosaka Laboratory Co., Ltd. (A) Stylus tip radius: 2 μm (b) Measurement pressure: 30 mg (c) Cut-off: 0.08 mm (d) Measurement length: 8.0 mm (e) How to summarize data: Repeated measurement of the same sample eight times The center line average roughness (Ra) is determined as an average value using the remaining seven data except for the largest value.

(3) Apparent Young's Modulus of Particles Ultra-fine compression tester MCTM-201 manufactured by Shimadzu Corporation
Using a diamond indenter at a constant load speed (29 mgf
/ Second) and apply an external force to one particle. And
The load P (kgf) when the particles are broken, the displacement Z (mm) of the indenter when the particles are broken, and the particle size d (m
From m), the apparent Young's modulus Y is calculated according to the following formula, and the same operation is performed 10 times, and the average value of 10 times is used as the apparent Young's modulus of the particles.

[0049]

## EQU5 ## Y = 2.8P / πdZ

(4) Particle Size Ratio (γ) A small piece of the particle-containing film is fixedly formed with an epoxy resin, and an ultra-thin section (cut in parallel to the longitudinal direction of the film) having a thickness of about 600 Å with a microtome. create. This sample is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.) to observe the cross-sectional shape of the particles in the film, and is represented by the ratio of the maximum diameter (long axis) to the minimum diameter (short axis) of the lubricant.

(5) Heat Shrinkage Marking points were formed at intervals of 30 cm in parallel with the longitudinal direction of the film.
This is kept in a gear oven at 120 ° C. for 30 minutes, and then the distance between the gauge points is measured. The heat shrinkage is determined by the following equation.

[0052]

(Equation 6)

(6) Air bleeding index 20 pieces of 8 cm × 5 cm pieces of film were stacked,
A 2mm-sided triangular hole is made in the center of the sheet. Using a Beck smoothness tester (Digi Beck) manufactured by Toyo Sokki Co., Ltd., the air bleeding time (unit: seconds) of 2 mmHg of this sample was 5
Measurements and the average value is taken as the air bleeding index.

(7) Sharpness Measured using the apparatus shown in FIG. 1 as follows. FIG.
Among them, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, and 8 are free rollers, 4 is a tension detector, 7 is a blade (a blade for an industrial razor testing machine manufactured by GKI, USA), and 9 is a guide roller. Reference numerals 10 and 10 respectively indicate take-up reels.

A sample film slit to a 1/2 inch width is run at 100 g under a tension of 100 g at a running speed of 100 m / min for 100 m at a running speed of 100 m / min so as to strike the blade blade edge at a 6 degree angle. To evaluate.

This evaluation is related to the impact strength of the projections formed on the film surface, and corresponds well to the generation of shavings by a die coater in the magnetic tape manufacturing process. <Judgment> Class 1 The width of the shaving powder adhering to the blade tip is 0.1 m.
Less than m 2nd grade The width of the shaving powder adhering to the blade tip is 0.1m
m or more and less than 0.2 mm Class 3 The width of the shaving powder adhering to the blade tip is 0.2 m
m or more and less than 0.5 mm Class 4 Blade shavings adhering to blade edge 0.5 m
m or more and less than 1.0 mm Class 5 The width of the shaving powder adhering to the blade tip is 1.0 m
m or more

(8) Coefficient of running friction Measured as follows using the apparatus shown in FIG.
In FIG. 2, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (entrance), and 7 is a stainless steel SUS304 fixing rod (outside). (Diameter 5 mmφ), 10 is a tension detector (outlet), 12 is a guide roller, and 13 is a take-up reel.

In an environment at a temperature of 20 ° C. and a humidity of 60%, the width 1 /
The film cut into 2 inches is placed on a 7 fixed rod (surface roughness 0.3 μm) at an angle θ = 152 / 180π radian (1
(52 °) and move (friction) at a speed of 200 cm per minute. The outlet tension (T ₂ : g) when the tension controller 2 is adjusted so that the inlet tension T ₁ becomes 35 g is detected by the outlet tension detector after the film has traveled 90 m, and the running friction coefficient μk is calculated by the following equation. calculate.

[0059]

(Equation 7)

(9) Electromagnetic conversion characteristics The S / N ratio of the magnetic tape for video was measured using a noise meter manufactured by Shibasoku Co., Ltd., and the difference between the S / N ratio and the tape of Comparative Example 1 shown in Table 2 was measured. Ask. The VTR used is Sony Corporation EDV-6000.

(10) Drop-out Using a drop-out counter manufactured by Shibasoku Co., Ltd., a drop-out of 15 μsec / 20 dB or more is performed for one drop-out.
Measure for 0 minutes and convert to the number per minute. V used
TR is Sony Corporation EDV-6000.

(11) Non-defective coated web rate A magnetic paint described below was applied to the base film, subjected to an orientation treatment in a DC magnetic field of 2500 Gauss, dried by heating at 120 ° C., and then subjected to a super calender treatment (linear pressure: 300 kg / c).
m, temperature 90 ° C.), and the wound roll of coated web was left in an oven at 55 ° C. for 3 days.
Evaluate the roll appearance. 100 rolls are inspected, and those without wrinkles are regarded as good products, and the number is shown as a percentage.

[0063]

EXAMPLES The present invention will be further described below with reference to examples.

Examples 1 to 8 and Comparative Examples 1 to 7 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and a lubricant as a lubricant The added particles shown in Tables 1 and 2 were added and polymerized by a conventional method to obtain an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.
62 polyethylene terephthalate (PET) for layer A and layer B was obtained.

Next, the polyethylene terephthalate for the A layer and the B layer was dried at 170 ° C. for 3 hours, respectively, and then supplied to separate extruders of a co-extrusion film forming machine, and the thickness ratio of the A layer and the B layer was 2: 2. An unstretched film was obtained by co-extrusion through a two-layer die.

The unstretched film thus obtained was preheated at 78 ° C., and furthermore, 15 m between low-speed and high-speed rolls.
The film was heated by an IR heater having a surface temperature of 850 ° C. from above and stretched 2.3 times, quenched, and subsequently supplied to a stenter and stretched 4.0 times horizontally at 100 ° C.

Subsequently, it is preheated at 110 ° C.
The film was stretched 2.3 times in the machine direction between low-speed and high-speed rolls.
The obtained biaxially stretched film was heat-set with hot air at 220 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 7.5 μm.

On the other hand, the following composition was placed in a ball mill, kneaded and dispersed for 16 hours, and 5 parts by weight of an isocyanate compound (Desmodur L, manufactured by Bayer AG) was added.
A high-speed shearing dispersion was performed for 1 hour to obtain a magnetic paint.

Composition of magnetic coating material: Acicular Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer 15 parts by weight (SREC 7A manufactured by Sekisui Chemical) 5 parts by weight of thermoplastic polyurethane resin 5 parts by weight of chromium oxide 5 parts by weight of carbon black Lecithin 2 parts by weight Fatty acid ester 1 part by weight Toluene 50 parts by weight Methyl ethyl ketone 50 parts by weight Cyclohexanone 50 parts by weight

This magnetic paint was applied to one side (layer A) of the above-mentioned polyester film so as to have a coating thickness of 3 μm, and then subjected to an orientation treatment in a DC magnetic field of 2500 gauss, and dried by heating at 120 ° C. It was calendered (linear pressure 300 kg / cm, temperature 90 ° C.) and wound up. The wound roll was left in an oven at 55 ° C. for 3 days. Further, a back coat layer having the following composition was applied to a thickness of 1 μm, dried and cut to obtain a magnetic tape.

Back coat layer composition: Carbon black 100 parts by weight Thermoplastic polyurethane resin 60 parts by weight Isocyanate compound (18 parts by weight from Japan Polyurethane Industry Co., Ltd. Coronate L) Silicone oil 0.5 parts by weight Methyl ethyl ketone 250 parts by weight Toluene 50 parts by weight

Tables 1 and 2 show the properties of the obtained films and tapes. As is clear from Tables 1 and 2, the film and the tape according to the present invention are magnetic tapes having excellent running properties, little dropout, and excellent electromagnetic conversion characteristics. Young's modulus of these films are longitudinal 830 kg / mm ^2, was transverse 460 kg / mm ^2.

Comparative Example 8 A film and a magnetic tape were obtained in the same manner as in Example 1 except that the heat setting temperature was 195 ° C. Table 2 shows the properties of the obtained films and tapes.
Shown in

As is clear from Table 2, the running property and the scraping property of the film were good, but the yield rate of the coated web was low due to the high heat shrinkage in the longitudinal direction of the film. The Young's modulus of this film is 850 kg / mm in the vertical direction.
² and 460 kg / mm ² in the horizontal direction.

[Examples 9 and 10] Layers A and B were prepared in the same manner as in Example 1 except that the acid component was changed to 2,6-naphthalenedicarboxylic acid and the particles A shown in Table 1 were used.
A pellet of polyethylene-2,6-naphthalenedicarboxylate (PEN) for the layer was obtained. After drying the polyethylene-2,6-naphthalenedicarboxylate pellets at 170 ° C. for 5 hours, an unstretched film was obtained in the same manner as in Example 1. You.

The unstretched film thus obtained is preheated to 120 ° C., and is further moved between low-speed and high-speed rolls by 15 m.
The film was stretched 5.2 times by heating with an IR heater having a surface temperature of 900 ° C. from above, rapidly cooled, and then supplied to a stenter and stretched 4.2 times in the transverse direction at 140 ° C. The obtained biaxially stretched film was heat-set with hot air at 210 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 7.5 μm.

Table 1 shows the properties of the obtained film and magnetic tape. Even if the type of polyester is changed, the film according to the present invention is a magnetic tape having excellent running properties, low dropout, and excellent electrical conversion characteristics for both the film and the magnetic tape. Young's modulus of these films are longitudinal 910 kg / mm ^2, was transverse 600 kg / mm ^2.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

According to the present invention, it has a flatness which can be applied particularly to a high quality magnetic tape, and also has a slipperiness and abrasion resistance which can sufficiently cope with a high speed of the magnetic tape processing step. Thus, it is possible to provide a laminated biaxially oriented polyester film having a good coated web winding form.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for measuring the sharpness of a film.

FIG. 2 is a schematic view of an apparatus for measuring a running friction coefficient of a film.

Claims (2)

(57) [Claims] 1. A laminated biaxially oriented polyester film in which at least two layers are laminated, and one exposed surface layer (layer A) of the film has an apparent Young's modulus (E : unity ) of particles.
Kg / mm ² ) and a particle size ratio (γ) satisfying the following formulas (1) and ( ² ) and containing 0.005 to 1% by weight of inert particles A having an average particle size of 0.01 to 0.4 μm. , Surface roughness (R
a _A: unit nm) is 1 to 10 nm, the other surface layer (B layer) is a surface roughness (Ra _B: unit nm) is the following formula 3
And a heat-shrinkage rate of 3% or less when kept at 120 ° C. in the longitudinal direction of the film for 30 minutes. Equation 1 150 <E Equation 2. (E / γ) ≦ 150 Equation 3. Ra _A <Ra _B <25 (nm) 2. The laminated biaxially oriented polyester film according to claim 1, wherein the film has an air release index of less than 5000.