JP3323409B2 - 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 a laminated biaxially oriented polyester film which is excellent in flatness, windability and abrasion resistance (abrasion resistance) with a heating roll, and is particularly useful for magnetic recording media. The present invention relates to a laminated biaxially oriented polyester film.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films have been used for a wide range of applications because of their excellent physical and chemical properties, especially as base films for magnetic recording media.

In recent years, higher density and higher capacity of magnetic recording media have been promoted, and accordingly, flatness and thinner thickness of the base film have been demanded.
However, in order to maintain excellent electromagnetic characteristics,
When the surface of the base film is flattened, the slipperiness is insufficient.For example, when rolled up into a roll, wrinkles or blocking occurs, and the surface of the film roll becomes uneven, lowering the yield of the product or winding up. The suitable range of tension, contact pressure, and speed becomes narrow, and it becomes very difficult to wind up.

Further, in a film processing step, particularly in a calendering step using a heating roll, friction with a heated metal roll increases, and shaving powder is generated, which causes a loss of magnetic recording, that is, a dropout. .

In general, the slipperiness of a polyester film can be improved by (i) a method in which inert particles are precipitated from a catalyst residue in a production process of a raw material polymer, or (ii) a method in which inert particles are added. A method of imparting irregularities to the film surface is employed. In general, the larger the size of the particles in these films and the greater the content thereof, the greater the improvement in the slipperiness.

On the other hand, as described above, the surface of the base film is required to be as flat as possible from the viewpoint of improving the electromagnetic conversion characteristics. When the surface roughness of the base surface is rough, when processing is performed on a magnetic recording medium, surface irregularities of the base film protrude from the surface of the magnetic layer even after the application of the magnetic layer, thereby deteriorating the electromagnetic conversion characteristics. In this case, as the size and the content of the particles in the base film increase, the surface roughness increases, and the electromagnetic conversion characteristics deteriorate.

[0007] As a means for achieving both the contradictory characteristics of the improvement of the slipperiness and the improvement of the electromagnetic conversion characteristics as described above, by forming a laminated film, the surface on which the magnetic layer is applied is flattened to improve the electromagnetic conversion characteristics. Means for improving the slipperiness by roughening the opposite surface are widely known.

However, even when the surface opposite to the surface on which the magnetic layer is applied (hereinafter referred to as a rough surface) is roughened by using the above-mentioned laminated biaxially oriented polyester film, the problem of slipperiness and abrasion resistance is not solved. Further, since the base thickness is thin, depending on the amount, type, and particle size of the lubricant added to the rough surface side, it affects the surface to which the magnetic layer is applied, causing undulations and the like on a flat surface, and This causes a problem of worsening the performance.

As means for improving abrasion resistance and running properties, there is a proposal to improve abrasion properties and running properties by incorporating particles A and aggregated particles B in a base film. For example, JP-A-3-90329 proposes a method in which silica particles and beads are added. However, in the case of using beads of aggregated silica particles, that is, aggregated particles, the affinity for the base film is impaired due to aggregation, and the particles easily fall off, especially on heated rolls, and generate shavings. The disadvantage of causing In addition, the aggregates of the particles are particularly likely to become coarse aggregates, which cause problems such as not only falling out easily as described above, but also easily causing projections which deteriorate the magnetic conversion characteristics.

[0010] Further, as a means for improving the wear resistance, there is a proposal to improve the wear resistance by including a single component particle in the base film. For example, Japanese Patent Application Laid-Open No. 4-119
No. 845 proposes a method for containing spherical silica particles. However, for example, when particles having a small particle size are included, the voids due to the unevenness generated on the surface are reduced, so that at the time of winding the film in the manufacturing process, the air squeezability deteriorates, and a defect occurs on the roll, Also, if the particle size is too large, the surface becomes too rough, which makes it easy to be scraped, or affects the flat surface on which the magnetic layer is applied, causing undulation on the flat surface, leading to deterioration in electromagnetic conversion characteristics. Is generated.

[0011]

The inventor of the present invention has conducted intensive studies to develop a film which solves the above problems at the same time. As a result, the film is made into a laminated biaxially oriented polyester film, and the surface of the film is run while heating. By setting the coefficient of friction to a specific value, the abrasion resistance (abrasion resistance) in the manufacturing process represented by the calendering process using a heated roll
And that the flatness and the winding property can be satisfied at the same time, and arrived at the present invention.

[0012]

Means for Solving the Problems That is, the present invention is a laminated biaxially oriented polyester film which is laminated to the polyester layer A on one surface of the polyester layer B, the thickness of the film is at 9μm or less, both running friction coefficient with respect to 60 ° C. hot pin surface (hereinafter, referred to as 60 ° C. running friction coefficient.) Ri is 0.05 to 0.75 der respectively, poly
Lubricant particles I and II are contained in the ester layer A, and the particles I,
When the aggregation rate of II is greater than 0 (%) and less than 20%
The average particle size of the particles I is 0.3 to 1.0 μm;
The content is 0.005% by weight or more and less than 0.1% by weight.
And the average particle size of the particles II is represented by the following formula (1)

(Equation 2) (Where dI is the average particle size of the lubricant particles I, dII is the lubricant particles
This is the average particle size of the child II. ) Is satisfied and the content is 0.1.
Not less than 1.0% by weight and a polyester B layer
Inactive particles having an average particle size of 0.005 to 1 μm are contained in 0.1%.
001 to 0.3 is a laminated biaxially oriented polyester film characterized that you containing by weight%.

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, as the polyester, alkylene terephthalate and / or alkylene-2,
Those containing 6-naphthalate as a main component are 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. In this case, 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. acid;
It may be an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Further, 20 mol% or less of the total glycol component can be the above-mentioned glycols other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcinol, and 2,2-bis (4-hydroxyphenyl) propane; Aliphatic diols having an aromatic ring such as dihydroxydimethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol.

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.
As the above-mentioned polyester, the intrinsic viscosity determined at 35 ° C. as a solution in o-chlorophenol is 0.4 to
0.9 is preferable, 0.5 to 0.7 is more preferable, and 0.55 to 0.65 is particularly preferable.

The biaxially oriented laminated polyester film of the present invention comprises two layers, polyester layer A and polyester layer B.
It is composed of layers. The two layers of polyester may be the same or different, but are preferably the same.

The laminated biaxially oriented polyester film of the present invention has a running friction coefficient at 60 ° C. of 0.05 to 0.7 on both surfaces of the polyester layer A and the polyester layer B.
Must be 5. The 60 ° C. running friction coefficient is preferably 0.1 to 0.5. When this 60 ° C running friction coefficient is smaller than 0.05, the film is very slippery,
When the film is wound, a trouble of a roll end face defect occurs. On the other hand, when it is larger than 0.75, the film running property in the film manufacturing process is poor, and the winding property is deteriorated.

[0021] The polyester film often comes into contact with a heating roll in a manufacturing process or a processing process. For example, the film comes into contact with the surface of the heating roll at the time of longitudinal stretching or re-longitudinal stretching, and the surface of the high-temperature roll comes into contact with the film at the time of calendering after application of the magnetic paint. Therefore, when the film comes into contact with the roll surface at such a high temperature (60 ° C. or higher), the particles easily fall off, and shavings are generated. Therefore, as described above, it is necessary to reduce the coefficient of friction at high temperatures.

As in the present invention, in order to reduce the running friction coefficient at a high temperature and to improve the flatness and good winding property of the film, the polyester layer A contains lubricant particles I and II. In addition, the agglomeration ratio of the lubricant particles I and II is more than 0 (%) and less than 20% . This aggregation rate is preferably 3% or more and less than 15%, more preferably 3% or more and less than 10%.

Here, the agglomeration rate of the particles means that the number of agglomerated particles in which two or more particles are agglomerated is X (number) and the total number of particles is Y (number) per 1 mm ² in the film plane. , Calculated by the following equation (2).

[0024]

(Equation 3)

X and Y are, for example, the number of agglomerated particles in which two particles are agglomerated (a ₁ ), the number of agglomerated particles in which three particles are agglomerated (a ₂ ), If there the number of particles and (a _{3) is, X = a 1 + a 2} , Y = a 1 + a
_It should be understood that ₂ + a ₃ .

When the agglomeration ratio of the lubricant particles I and II is 20% or more, the particles are liable to fall off and the abrasion resistance is remarkably deteriorated.
The coarse protrusions caused by aggregated particles affects the magnetic layer surface, causing undulation, to cause <br/> This pulls the reduction of electromagnetic characteristics.

Furthermore, the average particle diameter of the lubricant particles I to be included in the polyester layer A is 0.3 to 1.0 [mu] m, Ru further 0.4~0.8μm der. This average particle size is 1.0 μm
By weight, surface becomes rough, chipping resistance is deteriorated, while the air squeeze property you significantly deteriorated between runnability and film to be less than 0.3 [mu] m. Further, the lubricant particles I
Is more than 0.005% by weight and less than 0.1% by weight, more preferably 0.007 to 0.08% by weight, particularly preferably.
Properly is Ru 0.01 to 0.08% by weight der. When the content is 0.1 wt% or more, chipping resistance is deteriorated, while running properties is less than 0.005% by weight you worse. The average particle size of the lubricant particles II contained in the polyester layer A needs to satisfy the following formula (1).

[0028]

(Equation 4)

Here, dI is the average particle diameter of the lubricant particles I, dI
II is the average particle size of the lubricant particles II. The ratio (dI) of the average particle size (dI) of the lubricant particles I to the average particle size (dII) of the lubricant particles II
/ DII) is further preferably 2 to 8, particularly preferably 3 to 7. When the ratio (dI / dII) exceeds 10, the running property deteriorates, and the blocking between the films increases, and the winding property deteriorates. On the other hand, when the ratio becomes 1 or less, the film surface is remarkably roughened, chipping resistance, Ru worsen electromagnetic conversion characteristics.

[0030] In addition, the content of the lubricant particles II is 0. 1% to less than 1.0% by weight, more preferably 0.2% to less than 0.5% by weight, particularly preferably 0.2% by weight
Ru less than 0.4 wt% der least. When the content is less than 0.1% by weight, the running property is deteriorated, and the blocking between the films is increased, and the winding property is deteriorated. On the other hand, when the content is 1.0% by weight or more, the film surface is deteriorated. is significantly roughened, Ru worsen the chipping resistance and electromagnetic conversion characteristics.

In the laminated biaxially oriented polyester film according to the present invention, the surface roughness of the polyester layer A is 2 to 15 nm (0.002 to 0.01 nm) in terms of center plane average roughness WRa ^A.
5 μm). Polyester layer B
Has a center plane average roughness WRa ^B of 0.1 to 8 n.
m (0.0001 to 0.008 μm).

The center plane average roughness WRa was measured using a non-contact type three-dimensional roughness meter (TOPO-3D) manufactured by WYKO Co., Ltd., at a measurement magnification of 40 times, and a measurement area of 242 μm × 239 μm (0.
058 mm ² ).

The center plane average roughness WRa ^A is 0.002.
When the thickness is less than μm, the film running property is deteriorated.
If the thickness exceeds 015 μm, the abrasion resistance deteriorates, and even if a back coat is applied in the film processing step, the film is considerably roughened, and the magnetic conversion characteristics are deteriorated by the show-through phenomenon during curing, which is not preferable. . When the center plane average roughness WRa ^B is less than 0.0001 μm, blocking between films is increased, thereby deteriorating the winding property, and the coefficient of friction of a metal roll or the like in the film processing step is increased. Worsen the sharpness, while 0.0
When the thickness exceeds 08 μm, electromagnetic conversion characteristics are significantly deteriorated, which is not preferable.

In the laminated biaxially oriented polyester film, when the lubricant particles I and II contained in the polyester layer A are at least one selected from heat-resistant polymers and spherical silica particles, the effects of the present invention are more remarkable. Is preferable.

Examples of the heat-resistant polymer particles include cross-linked polystyrene resin particles, cross-linked silicone resin particles, cross-linked acrylic resin particles, cross-linked styrene-acryl resin particles, cross-linked polyester particles, polyimide particles, melamine resin particles, and the like. Among them, it is preferable to include crosslinked polystyrene resin particles or crosslinked silicone resin particles, because the effects of the present invention become more remarkable.

The laminated biaxially oriented polyester film
Then, polyester layer BIsContains inert particlesYou
RWith an average particle size of 0.005 to 1 μmPreferably
0.05 to 0.6 μm of inert particles of 0.001 to 0.
3% by weight, andPreferably0.005-0.2 weight
%,In particularPreferably0.005 to 0.1% by weightdo it
Is. Thereby, the running friction coefficient is kept within a predetermined range.
The film can be wound well. This inert
Lubricant particles to be contained in the polyester layer A as particles
Preferred examples include those exemplified above. this
One or more kinds of inert particles can be used. Po
Type and size of lubricant particles contained in the ester layers A and B
The lengths may be the same or different.

The laminated biaxially oriented polyester film of the present invention can be produced according to a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing a laminated non-oriented film and then biaxially orienting the film. This laminated non-oriented film can be produced by a conventionally accumulated method for producing a laminated film. For example, a method of laminating a polyester layer A and a polyester layer B forming the opposite surface in a molten state of the polyester or in a state of being cooled and solidified can be used. More specifically, it can be produced by a method such as co-extrusion or extrusion lamination. The film laminated by the above-mentioned method can be made into a biaxially oriented film by further following the conventional method for producing a biaxially oriented film. For example,
The polyester is melted and co-extruded at a temperature of melting point (Tm: ° C) to (Tm + 70) ° C to obtain a laminated unstretched film,
Place the unstretched film in a uniaxial direction (vertical or horizontal)
At a temperature of (Tg-10) to (Tg + 70) ° C (however, T
g: glass transition temperature of polyester) 2.5 times or more,
Preferably, the film is stretched at a magnification of 3 times or more, and then at a temperature of Tg to (Tg + 70) ° C.
The stretching is preferably performed at a magnification of at least 3 times, preferably at least 3 times. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. As described above, the total stretching ratio is preferably 9 times or more, more preferably 12 to 35 times, particularly preferably 15 to 30 times as the area stretching ratio. Furthermore, the biaxially oriented film is (Tg + 70) ° C. to (Tm
-10) can be heat-set at a temperature of ℃, for example, 18
It is preferable to heat set at 0 to 250 ° C. The heat setting time is preferably 1 to 60 seconds.

The Young's modulus of the obtained laminated biaxially oriented polyester film in the machine direction (MD) and the transverse direction (TD) is 400 kg / mm ² or more and 2000 kg / m ² , respectively.
m ² or less is preferred. This Young's modulus is 400 kg / mm
^If it is less than ² , the contact between the magnetic tape and the magnetic head becomes insufficient, and the electromagnetic conversion characteristics deteriorate, which is not preferable. on the other hand,
If the Young's modulus exceeds 2000 kg / mm ² , the film-forming properties of the film are undesirably reduced. MD Young's modulus is 40
0 to 900 kg / mm ² and the Young's modulus of TD is 55
It is particularly preferable that it is 0 to 1500 kg / mm ² .

The laminated biaxially oriented polyester film of the present invention preferably has an overall thickness of 2 to 9 μm. Further, when the thickness is 2 to 7 μm, the present effect is more remarkable, so that it is preferable.

The laminated biaxially oriented polyester film of the present invention is preferably used as a support (base film) of a magnetic recording medium and further a magnetic tape, particularly as a support of a magnetic tape of a digital recording system, due to the above-mentioned characteristics. .

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

(1) Average particle size (DP) of particles CP-50 type centrifugal particle size analyzer (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. 242-24
7).

(2) Non-contact type three-dimensional center plane average roughness WR
a Using a non-contact three-dimensional roughness tester (TOPO-3D) manufactured by WYKO, measurement magnification 40 times, measurement area 242 μm × 239 μm
The measurement is performed under the condition of m (0.058 mm ² ), and from the surface analysis by the built-in software of the roughness meter, WRa uses a value calculated and output by the following equation.

[0044]

(Equation 5)

Z _jk is the height on the two-dimensional roughness chart at the j-th and k-th positions in the measurement direction (242 μm) and the direction orthogonal to it (239 μm) divided into M and N, respectively. is there.

(3) Coefficient of running friction at 60 ° C. (μk) Measured as follows using the apparatus shown in FIG.
In FIG. 1, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, 8 and 11 are free rollers,
Is a tension detector (entrance), 7 is stainless steel SUS
A fixing pin 304 (outer diameter 5 mmφ), 10 is a tension detector (exit), 12 is a guide roller, and 13 is a take-up reel.

The primer layer side of the polyester film cut to a width of 1/2 inch was attached to a fixing pin (surface roughness: 10 nm) heated to 60 ° C. by a heater at 90 °.
At an angle [θ = (90/180) π (radian)], and move (friction) at a speed of 2 m / min. Inlet tension T ₁ is adjusted by the second tension controller so as to be 30g, the outlet tension obtained while 40m run (Ti: g) is detected and the maximum tension and T ₂ (g) during which the μk by the following formula calculate.

[0048]

(Equation 6)

(4) Particle Aggregation Rate The polyester film was etched using a plasma reactor PR3 manufactured by Yamato Chemical Co., Ltd. under the following conditions. High frequency power (W): 50 Oxygen flow rate (ml / min): 30 Etching Time (hr): 0.5 EMM3 manufactured by Elionix Co., Ltd.
000, and SEM (scanning electron microscope) observation is performed at a magnification of 10,000 times to measure the agglomeration rate of the lubricant particles.

(5) Sharpness (Abrasion Resistance) When measuring the running friction coefficient at 60 ° C., the amount of abrasion white powder adhering to the pins is visually evaluated and evaluated according to the rank shown below. ◎: Not adhered at all ○: Trace amount adhered △: Small amount adhered (more than ○) ×: Extremely large amount adhered

(6) 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 with the tape of Example 3 shown in Table 1 was determined. Ask. The VTR used is Sony Corporation EDV-6000.

The method of manufacturing the magnetic tape is as follows.
The composition shown below was placed in a ball mill and kneaded for 16 hours.
After dispersing, 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer AG) is added, and the mixture is sheared and dispersed at a high speed for 1 hour to obtain a magnetic paint. Composition of magnetic paint: needle-like 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 2 parts by weight of lecithin Part 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 B) of the laminated biaxially oriented polyester film so as to have a coating thickness of 3 μm, then subjected to an orientation treatment in a DC magnetic field of 2500 gauss, and dried by heating at 100 ° C. And spar calendering (linear pressure 300 kg / cm, temperature 80 ° C.) and winding. After keeping the wound roll in an oven at 55 ° C. for 3 days, it is cut into イ ン チ inch width to obtain a magnetic tape.

(7) Layer Thickness Using a secondary ion mass spectrometer (SIMS), an element originating from the highest concentration of particles in the film in a range from the surface layer to a depth of 3000 nm and a carbon element of polyester The concentration ratio (M ⁺ / C ⁺ ) 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. Then, the particle concentration that has once reached the maximum value starts to decrease again. Based on the concentration distribution curve, a depth at which the surface particle concentration becomes 1/2 of the maximum value (this depth is deeper than the depth at which the maximum value is obtained) is determined, and this is defined as the surface layer thickness.

The conditions are as follows. Measuring device Secondary ion mass spectrometer (SIMS) Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6 0.0 × 10 ⁻³ Torr E-GUN: 0.5 KV-3.0 A

In the case where the particles most contained in the range from the surface layer to the depth of 3000 nm are organic polymer particles, it is difficult to measure by SIMS. Therefore, XPS (X-ray photoelectron spectroscopy) and IR ( Infrared spectroscopy) may be used to measure the same depth profile as above to determine the surface layer thickness.

(8) Film winding property The film is wound into a roll, the appearance of the roll is visually evaluated, and the evaluation is made for each rank. The film is 700m
m width, winding length 7000m, contact pressure 40kg / m, tension 5kg
/ M. ：: no defect Δ: slight defect, but slight degree ×: extremely large defect

[0058]

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

Example 1 Dimethyl-2,6-naphthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and lubricant as a lubricant are shown in Table 1. The added particles were added and polymerized by a conventional method to obtain polyethylene-2,6-naphthalate (PEN) for layer A and layer B having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.61.

The polyethylene-2,6-naphthalate pellets were dried at 170 ° C. for 6 hours, and then supplied to two extruder hoppers and melted at a melting temperature of 280 to 300 ° C.
Layer A is laminated on one side of Layer B using a multi-manifold type coextrusion die, surface finish is about 0.3S, surface temperature is 6
It was extruded on a rotating cooling drum at 0 ° C. to obtain a laminated unstretched film having a thickness of 120 μm.

The unstretched laminated film thus obtained is preheated to 120 ° C., and is further rolled between low-speed and high-speed rolls.
The film was stretched 4.0 times by heating with an IR heater having a surface temperature of 900 ° C. from 5 mm above, rapidly cooled, then supplied to a stenter, and stretched 5.0 times horizontally at 145 ° 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 6.5 μm. The Young's modulus of these films is 6
00kg / mm ^2, was transverse 900 kg / mm ^2. Table 2 shows other film characteristics.

Examples 2 and 3, Comparative Examples 1 and 2 The same as Examples 1 and 2 except that the particles shown in Table 1 were used, and dimethyl terephthalate was used instead of dimethyl-2,6-naphthalate. Polyethylene terephthalate (PET) for polyester layer A and layer B was obtained by the method.

The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours, and a laminated unstretched film was obtained in the same manner as in Examples 1 and 2. (However, the surface temperature of the rotary cooling drum was set to 20 ° C.)

The unstretched laminated film thus obtained was preheated at 78 ° C., and further rolled between low-speed and high-speed rolls.
The film was stretched 2.3 times by heating with an IR heater having a surface temperature of 850 ° C. from 5 mm above, rapidly cooled, then supplied to a stenter, and stretched 3.6 times in the horizontal direction at 110 ° C.
Subsequently, it is preheated at 110 ° C., stretched 2.0 times in the longitudinal direction between low-speed and high-speed rolls, further supplied to a stenter, stretched 1.5 times in the transverse direction at 90 ° C., and obtained. 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.

The thickness of each layer was adjusted by changing the discharge amount of two extruders. The Young's modulus of this film is 600 kg / mm ^{2 in} the vertical direction and 610 kg /
mm ² . Table 2 shows other film characteristics.

[0066]

[Table 1]

[0067]

[Table 2]

As is clear from Table 2, the material according to the present invention has excellent resistance to scraping and winding with a heated roll,
It has electromagnetic conversion characteristics.

[0069]

According to the present invention, there is provided a laminated biaxially oriented polyester film which is excellent in flatness, windability and abrasion resistance (abrasion resistance) with a heating roll, and is particularly useful for magnetic recording media. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring a running friction coefficient.

[Explanation of symbols]

 1: Unwinding reel 4: Tension detector (entrance) 7: Heat fixing pin 10: Tension detector (exit) 13: Take-up reel

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-1114726 (JP, A) JP-A-5-212789 (JP, A) JP-A-8-30958 (JP, A) 77318 (JP, A) JP-A-9-277472 (JP, A) JP-A-9-201926 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00

Claims (7)

(57) [Claims] 1. A laminated biaxially oriented polyester film in which a polyester layer A is laminated on one side of a polyester layer B, wherein the thickness of the film is 9 μm or less, and 60 ° C. heating pins on both surfaces. running friction coefficient with respect to the 0.05 to 0.75 der respectively is, contains lubricant particles I, II in the polyester layer a, particles
Aggregation ratio of I and II is more than 0 (%) and less than 20%
And the average particle size of the particles I is 0.3 to 1.0 μm.
And the content is not less than 0.005% by weight and less than 0.1% by weight
And the average particle size of the particles II satisfies the following formula (1)
And the content is 0.1% by weight or more and less than 1.0% by weight.
The average particle size in the polyester B layer is 0.005 to 1 μm.
Laminated biaxially oriented polyester film characterized that you contain inert particles 0.001 to 0.3 wt%. (Equation 1) Here, dI is the average particle size of the lubricant particles I, and dII is the lubricant particle I.
It is the average particle size of I. 2. A laminated biaxially oriented polyester film of claim 1, wherein center plane average roughness WRa ^A of the surface of the polyester layer A is 2 to 15 nm. 3. A laminated biaxially oriented polyester film of claim 1 wherein the center plane average roughness WRa ^B of the surface of the polyester layer B is 0.1 to 8 nm. 4. The laminated biaxially oriented polyester film according to claim 1, wherein the total thickness of the film is 2 to 7 μm. 5. The laminated biaxially oriented polyester film according to claim 1, wherein a running friction coefficient with respect to a 60 ° C. heating pin on both surfaces of the polyester layers A and B is 0.1 to 0.5. 6. A magnetic recording medium using the laminated biaxially oriented polyester film according to claim 1 as a base film. 7. The magnetic recording medium according to claim 6, which is a digital recording type magnetic tape.