JP2001138460A - Laminated polyester film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film which shows good end part skiving properties and is best suited for a high-capacity magnetic tape. SOLUTION: This laminated polyester film is characterized in that it has a thickness of 15 μm or less and a modulus of elasticity E of 6 GPa or more in the film width direction and/or the film longer direction and further, a bending strength index M of 7.5×10-3 N/m or more in the width direction in terms of 5 μm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film having a large flexural strength even if the thickness is small, and particularly suitable for a high-density magnetic recording tape.

[0002]

2. Description of the Related Art Polyester films are used for capacitors and packaging by utilizing their excellent mechanical properties, thermal properties, electrical properties, surface properties, optical properties, heat resistance and chemical resistance. Are widely used for various purposes such as magnetic recording media. Among them, magnetic recording media are widely used as video tapes and data tapes because tape-shaped media can provide a large recording area. For video tapes and data tapes, there are a helical system that records a large number of recording tracks inclined with respect to the film longitudinal direction using a rotating head, and a linear system that uses multiple fixed heads to provide recording tracks parallel to the film longitudinal direction. In any case, in order to increase the storage capacity, various measures have been taken, such as increasing the areal recording density or reducing the tape thickness to increase the recording area per volume.

Conventionally, as a support for a magnetic recording tape,
Films made of polyester represented by polyethylene terephthalate have been used. However, when the tape thickness is reduced as described above, the bending rigidity of the film is reduced, and various problems are likely to occur. In particular, the lack of bending stiffness in the film width direction not only tends to cause insufficient output due to spacing loss between the tape and the reproducing head, especially in helical recording tape, and also causes the tape end to buckle during tape running. It is susceptible to abrasion, and in linear recording, a recording track cannot be provided up to the end of the tape. In helical recording, there is a problem that the track length cannot be long. In addition, when the bending rigidity in the longitudinal direction of the film is insufficient, not only the output tends to be insufficient particularly in a linear recording tape, but also the end wear similar to the above tends to occur.

[0004] In order to solve the above-mentioned problems, various measures have been devised to increase the elastic modulus of polyethylene terephthalate by devising stretching conditions, and to use a polyethylene naphthalate film which is easy to obtain a film having a higher elastic modulus than polyethylene terephthalate. However, it was insufficient to increase the capacity more than the present. Aramid films for magnetic recording media with higher elastic modulus than polyester are also being studied, but in general, aramid films are more expensive than polyester films, especially for data backup tapes for personal computers using small cassettes. It is not used outside.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to provide a laminated polyester film having a large bending strength.

[0006]

The laminated polyester film of the present invention for achieving the above object has a thickness of 15 μm or less, an elastic modulus E in the film width direction and / or the film longitudinal direction of 6 GPa or more, and 5
A laminated polyester film having a bending strength index M in terms of μm of 7.5 × 10 ⁻³ N / m or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the laminated polyester film of the present invention includes polyethylene terephthalate, polyethylene naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polypropylene naphthalate. It is preferable to reduce coarse protrusions on the surface, but is not particularly limited. Further, a mixture of two or more of these may be used. Further, those obtained by copolymerizing these and other dicarboxylic acid components or diol components may be used. Further, a composite film having two or more layers of an inner layer and a surface layer may be used. For example, a composite film having substantially no particles in the inner layer portion and having a layer containing the particles in the surface layer portion, a laminate film having coarse particles in the inner layer portion and containing fine particles in the surface layer portion And the like. In the composite film, the inner layer portion and the surface layer portion may be of different polymers or of the same type. When the above-mentioned polyester is used, its intrinsic viscosity (measured in o-chlorophenol at 25 ° C) is preferably 0.4 to 1.2 dl / g, and 0.5 to 0.8 d / g.
More preferably, it is 1 / g.

The polyester film of the present invention comprises
It is biaxially oriented. Biaxially oriented means that the polyester film has not been stretched, that is, the polyester film before crystal orientation is completed is stretched about 2.5 to 5.0 times in the longitudinal direction and width direction, respectively, and then the crystal orientation is completed by heat treatment. Which indicates a biaxially oriented pattern in wide-angle X-ray diffraction. When the polyester film is not biaxially oriented, the heat resistance, dimensional stability, and mechanical strength of the laminated polyester film become insufficient, and a laminated film suitable for the present invention cannot be obtained. The polyester film of the present invention may contain various additives, a resin composition, a cross-linking agent, and the like as long as the effects of the present invention are not impaired. For example, antioxidants, heat stabilizers, ultraviolet absorbers, organic and inorganic particles, pigments, dyes, antistatic agents, nucleating agents, flame retardants, acrylic resins, polyester resins, urethane resins,
Polyolefin resin, polycarbonate resin, alkyd resin, epoxy resin, urea resin, phenol resin, silicone resin, rubber-based resin, wax composition, melamine-based crosslinking agent, oxazoline-based crosslinking agent, methylolated, alkylolated urea-based crosslinking Agents, acrylamide, polyamide, epoxy resin, isocyanate compound, aziridine compound, various silane coupling agents, various titanate coupling agents, and the like.

The laminated polyester film of the present invention has a thickness of 15 μm or less, preferably 10 μm or less, more preferably 7 μm or less. In general, in the case of a film having a single structure, the bending strength is proportional to the cube of the thickness. Therefore, when the film thickness is larger than 15 μm, the problem due to the insufficient bending strength to be solved by the present invention does not occur. Although the lower limit of the thickness of the laminated polyester film is not particularly limited, when the thickness is 0.5 μm or less, the film is liable to be broken by stretching, or to be liable to cause troubles such as pinholes. However, it is difficult to mass-produce industrially.

The laminated polyester film of the present invention has a modulus of elasticity of 6 GPa or more in the film width direction and / or the longitudinal direction of the film and a bending strength index of 7.5 × 10 ^-3 or more in terms of a thickness of 5 μm. It is necessary that the elastic modulus in the film width direction and / or the film longitudinal direction is 7 GPa or more, and the thickness is 5 μm.
The bending strength index in terms of m is 8.5 × 10 ⁻³ or more, more preferably the elastic modulus in the film width direction and / or the film longitudinal direction is 8 GPa or more, and the thickness is 5 μm.
The converted bending strength index is preferably 10 × 10 ⁻³ or more. When the elastic modulus in the film width direction and the film longitudinal direction are both smaller than 6 GPa, or when the bending strength index in the film width direction and the film longitudinal direction in terms of the thickness of 5 μm is less than 7.5 × 10 ^-3. However, when the tape is used as a narrow tape, there is a problem that the end portion is liable to be worn by running. In the laminated polyester film of the present invention, the ratio M / N of the bending strength index M (N / m) and the elastic modulus E (GPa) in terms of a thickness of 5 μm in either the longitudinal direction or the width direction of the film.
It is preferable that E is 1.2 × 10 ⁻³ or more, preferably 1.3 × 10 ⁻³ or more, and more preferably 1.4 × 10 ⁻³ or more. When M / E is smaller than 1.2 × 10 ⁻³ , in order to obtain a laminated polyester film having a large bending strength index E, the heat shrinkage in the film width direction increases,
Reliability when used as a magnetic tape is likely to deteriorate.
Elastic modulus E of film, flexural strength index M converted to thickness of 5 μm
Although there is no particular upper limit on the ratio M / E of the two, the material that can be used by being laminated on the polyester film is limited, and the cost is limited. Therefore, the elastic modulus E of the film is 12 GPa or less. And the bending strength index M converted to a thickness of 5 μm is 25 N / m or less, and the ratio M between the bending strength index M converted to a thickness of 5 μm (N / m) and the elastic modulus E (GPa).
/ E is generally 2.0 or less.

It is necessary that the elastic modulus and the flexural strength index in at least one direction are in specific ranges.
However, it is generally difficult to satisfy the specific range at the same time in both the width and longitudinal directions of the film.

The bending strength of a film is proportional to the product of the modulus of elasticity and the cube of the film thickness in a single-layer film having a uniform elastic modulus in the thickness direction. Therefore, it is effective to increase the elastic modulus in order to increase the bending strength of a thin single-layer film. However, in the case of a film having a laminated structure, the bending strength can be greatly improved by providing layers having a large elastic modulus on both sides of the film. As a layer having a large elastic modulus, an inorganic film such as a metal or glass, a cross-linkable polymer film, or the like can be used. It is preferable to use a polyester film that is biaxially oriented as a base layer and heat-resistant resin laminated on both sides.

Generally, the degree of orientation of a polyester film can be estimated from the refractive index. Since the refractive index in that direction is increased by stretching a polyester film, the average value of the refractive index in the film longitudinal direction and the refractive index in the film width direction is larger than the refractive index in the film thickness direction in a biaxially oriented polyester film. Become. Although not particularly limited, the difference between the average value of the refractive index in the film longitudinal direction and the refractive index in the film width direction and the difference in the film thickness direction is preferably 0.05 to 0.25, and 0.10 to 0.18. Is particularly preferred. The refractive index in each direction of the film can be measured by, for example, an Abbe refractometer provided with an eyepiece with a polarizer.

The heat-resistant resin used here has a glass transition point of 170 ° C. or higher and / or 300 ° C. due to its heat resistance.
Those having no melting point or decomposition point are preferred below. The heat-resistant resin selected from the above requirements is not particularly limited as long as the resin satisfies the requirements, but examples thereof include aromatic polyamide resins, aromatic polyimide resins and precursors thereof, and polyamideimide resins. , Polyethersulfone-based resins, polyetherimide-based resins, polybenzimidazoles and their precursors, polybenzoxazoles and their precursors, polybenzthiazoles and their precursors, and polysulfone-based resins. Among these, those which can be dissolved in a dipolar aprotic solvent are particularly preferred, and aromatic polyamide resins are particularly preferred. Examples of the dipolar aprotic solvent include N-
Methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like can be mentioned. In the present invention, dissolving the heat-resistant resin in these dipolar aprotic solvents has a very important meaning in the adhesion between the polyester film and the heat-resistant resin layer. Is difficult. That is, a solvent that dissolves the heat-resistant resin and whitens or swells the polyester film before the completion of the crystal orientation is particularly preferable, and among the above, N-methyl-2-pyrrolidone is particularly preferable. The aromatic polyamide suitable in the present invention is a repeating unit represented by the following general formula (1) and / or general formula (2) alone or in a copolymerized form in an amount of 50 mol% or more, preferably 70 mol% or more. It is desirable to include it.

[0015]

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[0016]

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Here, as Ar ₁ , Ar ₂ and Ar ₃ , for example, those shown in (a) to (e) of the general formula (3) are used.

[0018]

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X and Y are -O-, -CH-, -CO-,
-SO_Two-, -S-, -C (CH_Three) _Two-Selected from
However, the present invention is not limited to these. Furthermore, these
Some of the hydrogen atoms on the aromatic ring are chlorine, fluorine, bromine, etc.
Halogen group (especially chlorine is preferred), nitro group, methyl
Groups, ethyl groups, propyl groups and other alkyl groups (especially methyl
A methoxy group, an ethoxy group, and a propoxy group.
Substituted with a substituent such as an alkoxy group such as a silyl group
And the hydrogen in the amide bond that constitutes the polymer
Includes those substituted with other substituents.
is there.

In particular, a polymer in which the aromatic ring of the general formula (2) is bonded at the para position accounts for 50 mol% or more, more preferably 70 mol% or more of the total aromatic ring, reduces the curl amount during heat treatment. It is preferred in terms of. Some of the hydrogen atoms on the aromatic ring are chlorine, fluorine, bromine and other halogen groups (particularly preferably chlorine), nitro groups, methyl groups, ethyl groups, alkyl groups such as propyl groups (particularly preferably methyl groups), Aromatic ring substituted with a substituent such as an alkoxy group such as a methoxy group, an ethoxy group, or a propoxy group accounts for 30 mol% of the whole.
As described above, it is preferable that the content be 50 mol% or more, because it becomes easier to obtain a laminated film having a small curl amount during the heat treatment. In the present invention, the content of the repeating unit represented by the general formula (1) and / or the general formula (2) is desirably 50 mol% or more, preferably 70 mol% or more. Copolymerization of compounds or other polymers may be mixed.

The heat-resistant resin layer may contain various additives, a resin composition, a cross-linking agent and the like within a range not to impair the effects of the present invention. For example, antioxidants, heat stabilizers, ultraviolet absorbers, organic, inorganic particles such as spherical silica, pigments,
Dyes, antistatic agents, nucleating agents, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins, alkyd resins, epoxy resins, urea resins, phenol resins, silicone resins, rubber resins, wax compositions, melamine crosslinks Agents, oxazoline-based crosslinking agents, methylolated, alkylolated urea-based crosslinking agents, acrylamide, polyamide, epoxy resins, isocyanate compounds, aziridine compounds, various silane coupling agents, various titanate coupling agents, and the like. it can.

The method of laminating the heat-resistant resin layer on the polyester film is not particularly limited, and any method such as a method of bonding a film made of the heat-resistant resin via an adhesive layer, a method of applying and drying the heat-resistant resin, and the like can be used. However, a method in which a heat-resistant resin layer is provided by coating and drying is preferable because a surface form suitable for use as a magnetic recording medium can be easily obtained. In order to more effectively exhibit the effects of the present invention, it is preferable that the heat-resistant resin layer is laminated on both surfaces of the biaxially oriented polyester film without substantially interposing an adhesive layer. Here, the term "substantially not through the adhesive layer" means that no layer other than the base material and the laminated film forming substance is formed at the interface between the base material and the laminated film in a state where the heat-resistant resin layer is laminated on the polyester film. It means that. However, it is particularly preferable that a mixed layer of a base material and a heat-resistant resin layer is formed at the interface because the adhesiveness is further improved, and the layer is out of the definition of the adhesive layer.

The laminated polyester film of the present invention comprises:
The curl amount at the time of heat treatment at 80 ° C. needs to be 10 mm or less, preferably 5 mm or less. If the curl amount at the time of heat treatment at 180 ° C. is greater than 10 mm, a step of providing a magnetic layer by a method such as evaporation or sputtering when subjected to a heat treatment in a film processing step, particularly when used as a high-density magnetic recording medium, After coating the thin film magnetic layer containing powder or hexagonal ferrite, there is a problem that the flatness is deteriorated in the step of heating and drying.

In the laminated polyester film of the present invention, when a heat-resistant resin is laminated on both sides of a biaxially oriented polyester film, the ratio (TL) of the thickness of the heat-resistant resin layer to the total thickness of the film is 1% or more and 50% or more. %, Preferably 10% or more and 30% or less. When the TL is less than 1%, it is difficult to obtain a film having a large bending strength, which is not preferable. TL
Is larger than 50%, the recoverability tends to deteriorate, and the raw material price becomes high, which is not preferable.

The method for producing the laminated film of the present invention will be described, but is not limited thereto.

A sufficiently dried polyester chip is supplied to an extruder, melt-extruded at 280 to 300 ° C., and formed into a sheet on a mirror cooling drum at 20 to 70 ° C. The sheet is stretched in the longitudinal direction at a temperature of 80 to 120 ° C. for 2.5 to
Stretch 5.5 times. Here, it is preferable to carry out stretching twice or more while changing the temperature and the magnification in order to increase the film forming speed and to obtain a film having a large elastic modulus in the longitudinal direction of the film. A heat-resistant resin dissolved in a solvent to be laminated on the both sides of the uniaxially oriented polyester film is applied, and then both ends of the film are gripped with clips.
Through a preheating step of 0 to 120 ° C, stretching is performed 2.5 to 6.0 times in the width direction at 80 to 120 ° C. 180 more continuously
Heat treatment is performed at ~ 250 ° C to complete the crystal orientation of the base polyester film. Here, when stretching in the width direction,
It is preferable that the solvent is stretched together with the base material before being completely dried, and then the solvent is evaporated to evaporate and complete the crystal orientation of the base material.The solvent used is a preheating step after the coating and before the stretching, in the stretching step. It is preferable from the viewpoint of adhesion to the base material that most of the residual material remains and evaporates in the heat treatment step after stretching. Further, it is preferable to re-stretch in the longitudinal direction or the width direction after the solvent is dried in order to obtain a film having a large elastic modulus in the longitudinal direction or the width direction of the film.

The laminated polyester film of the present invention is suitable for a high-capacity magnetic recording medium.
For applications where edge wear due to low bending strength in the width direction is likely to be a problem during film processing and when used as processed products, for example, thermal transfer type printer ribbons and condensers for vapor deposition , FP
It can be used for C applications.

(Method of measuring characteristics and method of evaluating effects)
The method for measuring characteristics and the method for evaluating effects in the present invention are as follows.

(1) Flexural strength index M converted to a thickness of 5 μm.
Cut to 0 cm and 20 mm width. Using a loop stiffness tester manufactured by Toyo Seiki Seisaku-sho, Ltd., bending stress M1 (m
g) was measured. The loop length was 50 mm and the crushing distance was 20 mm.

From the measured value M1 (mg) of the bending stress and the sample thickness t (μm), a bending strength index M (N / m) converted into a thickness of 5 μm was calculated using the following equation.

M = 3.92 × 10 ⁻⁶ × M1 × t ^{3 The} measurement was performed using 20 samples at different sampling positions, and the average value was used.

(2) Elastic Modulus E The sample was cut into a strip having a length of 200 mm and a width of 10 mm in the measurement direction. In accordance with the method specified in JIS K-7127, it was measured at 25 ° C. and 65% RH using a tensile tester manufactured by Toyo Seiki Seisaku-sho, Ltd. The initial distance between the tensile chucks was 100 mm, and the tensile speed was 300 mm / min. The measurement was performed 20 times while changing the sample, and the average value was used.

(3) Film bending strength index M and elastic modulus E
The film bending strength index M obtained by the above method was divided by the elastic modulus E in the direction to obtain M / E.

(4) Ratio of thickness of heat-resistant resin layer to thickness of entire film (TL) A cross section is cut out from the laminated polyester film, and the cross section is observed with a transmission electron microscope. Was measured for the thickness (t2) of the heat-resistant resin layer and the thickness (t3) of the entire film. When there is a mixed phase, the thickness including the mixed phase was defined as the thickness of the heat-resistant resin layer.

TL (%) = 100 × (t1 + t2) / t3 (5) Number of coarse projections having a height of 0.27 μm or more (H1) Foreign substances are observed and marked under polarized light on a film surface of 10 cm ² or more by a stereoscopic microscope. The height of the marked foreign matter is observed at a wavelength of 546 nm using a multiple interferometer, and the number of interference fringes having a single ring or more is converted into the number per 100 cm ² .

(6) End scraping test 1 (end flaw) Using a tape running tester, a film obtained by slitting a film into a tape having a width of 12.7 cm and a stainless steel guide pin (10 ° inclined from the vertical direction) was used. 7mm diameter, surface roughness:
Run on 100nm Ra (running speed 3.3m)
/ Min, wrap angle 90 °, output side tension 100g, running frequency reciprocating 50 times). At this time, the scratches entering the edge of the film were observed with a microscope, and the number of scratches having a width of 2.5 μm or more per tape width was determined to be excellent when 2 or less, and 2 or more and less than 10 were determined to be good, and 10 or more were determined to be bad. . Although excellent is desirable, even good is practically usable.

(7) End scraping test 2 (end shavings) The surface of the metal guide after the above-mentioned test (6) was observed, and white shavings generated by the shaving and adhered to the metal guide were visually observed. In the above, the detection was inferior and not visually observable, but the one that could be confirmed with an optical microscope (50 times) was good, and the one that could not be confirmed with an optical microscope (50 times) was excellent.

(8) End scraping test 3 (one-sided elongation) Using a tape running tester, a film obtained by slitting a film into a tape having a width of 12.7 cm was tilted by 10 ° from a vertical direction into a stainless steel guide pin (diameter). 7 mm, surface roughness:
(100 nm in Ra), and run once, with a diameter of 15.2.
cm of cylindrical core (running speed 250m / min,
Winding angle 60 °, output side tension 100g, sample length 2
00m). Observe both ends of the film in the width direction of the rolled film.
A value of 1 mm or more was judged as good if less than 1 mm. Although excellent is desirable, even good is practically usable.

(9) Heat Shrinkage The heat shrinkage was measured according to the method specified in JIS C-2318. However, the oven temperature and the holding time were set to 100 ° C. and 30 minutes.
The average of the measurement results was used. The smaller the heat shrinkage in the width direction is, the more preferable it is.
When used as a high-density magnetic tape, the reliability is poor and the tape is unsuitable.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) which had been passed through a sintered metal filter having a filtration accuracy of 1.2 μm and a polypropylene filter having a filtration accuracy of 0.6 μm in advance as an aromatic diamine component was added as an aromatic diamine component. 2 mol% of 2-chloroparaphenylenediamine and 10 mol% of 4,4′-diaminodiphenyl ether are dissolved,
To this, 2-chloroterephthalic acid chloride corresponding to 100 mol% and colloidal silica having an average particle diameter of 0.05 μm were added, and the mixture was stirred for 2 hours to complete the polymerization, thereby obtaining an aromatic polyamide solution having a polymer concentration of 10% by weight. Was. Since hydrochloric acid is contained in this polyamide solution, this solution is reprecipitated with a large amount of water, the polymer is isolated, and
The hydrochloric acid was removed by washing in running water at 0 ° C. for 60 minutes. After drying the obtained polymer at 150 ° C., 5
The solution was gradually dissolved at 0 ° C. to obtain an aromatic polyamide solution (hereinafter referred to as solution A) having a polymer concentration of 10% by weight and a colloidal particle concentration of 0.005% by weight based on the polymer.

A polyethylene terephthalate (intrinsic viscosity: 0.63 dl / g) chip containing substantially no particles was used.
After sufficiently vacuum drying at 80 ° C, supply to an extruder,
After melting at 285 ° C, it is passed through a sintered metal filter with a filtration accuracy of 2 μm, extruded into a sheet shape from a T-shaped die, and wrapped around a mirror surface cast drum having a surface temperature of 20 ° C using an electrostatic application casting method to cool and solidify. did. The unstretched sheet was stretched 3.5 times in the longitudinal direction with a group of rolls heated to 95 ° C. to obtain a uniaxially stretched film. The solution A was passed through a sintered metal filter having a filtration accuracy of 5 μm and 0.9 μm on both sides of the film, and then applied by a die coating method so that the final lamination thickness per side was 0.5 μm. The coated film was guided to a preheating zone at 80 ° C. while holding both ends of the film with clips, and then stretched 4.0 times in the width direction in a heating zone at 100 ° C. Further, after a heat treatment for one second was continuously performed with a heat treatment soak at 230 ° C., the film was heated in a 230 ° C. heating zone while holding both ends of the film with clips.
After stretching three times, heat treatment was performed at 230 ° C. for 4 seconds under constant length to completely dry the NMP. This laminated film had a thickness of 5 μm and a laminated thickness of 0.5 μm on each of the front and back sides.

Example 2 The overall thickness of the film was 7.5 μm, and the lamination thickness was 0.1 mm for each of the front and back sides.
A laminated film was obtained in the same manner as in Example 1 except that the thickness was 3 μm.

Example 3 A polyethylene terephthalate (intrinsic viscosity: 0.63 dl / g) chip substantially free of particles was sufficiently dried in vacuum at 180 ° C., fed to an extruder, melted at 285 ° C., and filtered. After passing through a 2 μm sintered metal filter, it was extruded into a sheet shape from a T-shaped die and wound around a mirror-surface cast drum having a surface temperature of 20 ° C. using an electrostatic application casting method to be cooled and solidified. The unstretched sheet was stretched 3.5 times in the longitudinal direction with a group of rolls heated to 95 ° C. to obtain a uniaxially stretched film. After passing the solution A through a sintered metal filter having a filtration accuracy of 5 μm and 0.9 μm on both sides of the film, the final lamination thickness per side is 0.1 mm by a die coating method.
It was applied so as to have a thickness of 2 μm. While holding both ends of the applied film with clips, guide it to the preheating zone of 80 ° C,
Subsequently, the film was stretched 4.0 times in the width direction in a heating zone at 100 ° C. Further, the film was continuously heat-treated at 230 ° C. for 1 second, then stretched 1.2 times in a heating zone at 230 ° C. while holding both ends of the film with clips, and then heated at 230 ° C. under a constant length. Heat treatment for 4 seconds, NMP
Was completely dried. This laminated film has a thickness of 5μ.
m, and the lamination thickness was 0.2 μm on each of the front and back sides.

Example 4 A polyethylene terephthalate (intrinsic viscosity: 0.63 dl / g) chip substantially free of particles was sufficiently dried in vacuum at 180 ° C., fed to an extruder, melted at 285 ° C., and filtered. After passing through a 2 μm sintered metal filter, it was extruded into a sheet shape from a T-shaped die and wound around a mirror-surface cast drum having a surface temperature of 20 ° C. using an electrostatic application casting method to be cooled and solidified. The unstretched sheet was stretched 3.5 times in the longitudinal direction with a group of rolls heated to 95 ° C. to obtain a uniaxially stretched film. After passing the solution A through a sintered metal filter having a filtration accuracy of 5 μm and 0.9 μm on both sides of the film, the final lamination thickness per side is 0.1 mm by a die coating method.
It was applied so as to have a thickness of 3 μm. While holding both ends of the applied film with clips, guide it to the preheating zone of 80 ° C,
Subsequently, the film was stretched 4.5 times in the width direction in a heating zone at 100 ° C. Further, a heat treatment was continuously performed with a heat treatment soak at 230 ° C. for 5 seconds to completely dry the NMP. This laminated film had a thickness of 5 μm and a laminated thickness of 0.3 μm on each of the front and back sides.

Example 5 The total film thickness was 5 μm, and the lamination thickness was 1.0 μm for each of the front and back sides.
A laminated film was obtained in the same manner as in Example 4 except that m was used.

Example 6 The total thickness of the film was 5 μm, and the lamination thickness was 0.06 for each of the front and back sides.
A laminated film was obtained in the same manner as in Example 5, except that the stretching ratio in the width direction was set to 5.2 times in μm.

Example 7 A polyethylene terephthalate (intrinsic viscosity: 0.63 dl / g) chip substantially free of particles was sufficiently vacuum-dried at 180 ° C., fed to an extruder, melted at 285 ° C., and filtered. After passing through a 2 μm sintered metal filter, it was extruded into a sheet shape from a T-shaped die and wound around a mirror-surface cast drum having a surface temperature of 20 ° C. using an electrostatic application casting method to be cooled and solidified. The unstretched sheet was stretched 3.5 times in the longitudinal direction with a group of rolls heated to 95 ° C. to obtain a uniaxially stretched film. After passing the solution A through a sintered metal filter having a filtration accuracy of 5 μm and 0.9 μm on both sides of the film, the final lamination thickness per side is 0.1 mm by a die coating method.
It was applied so as to have a thickness of 5 μm. While holding both ends of the applied film with clips, guide it to the preheating zone of 80 ° C,
Subsequently, the film was stretched 4.5 times in the width direction in a heating zone at 100 ° C. Further, heat treatment was continuously performed for 3 seconds with a heat treatment sone at 230 ° C. Thereafter, the film is stretched 1.3 times in the longitudinal direction of the film continuously on a group of known silicone rubber rolls having a surface temperature of 160 ° C., and heated at 230 ° C. for 10 seconds while holding both ends of the film in a known tenter. went.
This laminated film had a thickness of 5 μm and a laminated thickness of 0.5 μm on each of the front and back sides.

Comparative Example 1 0.005 of colloidal silica having an average particle size of 0.05 μm
A polyethylene naphthalate (intrinsic viscosity: 0.60 dl / g) chip containing 1.0% by weight is sufficiently vacuum-dried at 180 ° C., fed to an extruder, melted at 285 ° C., and passed through a sintered metal filter having a filtration accuracy of 2 μm. After that, the resultant was extruded into a sheet shape from a T-shaped die, wound around a mirror-surface cast drum having a surface temperature of 20 ° C. by an electrostatic application casting method, and cooled and solidified. The unstretched sheet is stretched 3.5 times in the longitudinal direction with a group of rolls heated to 140 ° C., guided to a preheating zone of 100 ° C. while holding both ends of the film with clips, and then in a width direction in a heating zone of 140 ° C. The film was stretched 4.0 times. Further, a heat treatment was continuously performed for 5 seconds using a 230 ° C. heat treatment sone. This polyester film has a thickness of 5μ.
m.

Comparative Example 2 The total film thickness was 5 μm, and the lamination thickness was 0.01 on each side.
A laminated film was obtained in the same manner as in Example 1 except that the thickness was changed to μm.

Table 1 shows film properties of Examples and Comparative Examples.
Shown in The examples were within the scope of the present invention and were excellent in the abrasion resistance of the edges, but the films of the comparative examples were out of the scope of the invention and were poor in edge scraping. Met.

Example 8, Comparative Example 3 A cobalt-nickel alloy (N) was applied to the surface of the film of Example 1 by using a continuous vacuum evaporation apparatus in the presence of a trace amount of oxygen.
(i 20% by weight). Then
After a carbon protective film was formed on the surface of the vapor deposition layer and a back coat layer was formed on the opposite surface by a known means, slits were formed to a width of 8 mm to prepare a pancake. Then the length from this pancake
A 200-m portion was assembled into a cassette to form a cassette tape (Example 8). For the film of Comparative Example 2, a cassette tape was prepared in the same manner as in Example 8. About this tape,
Using a commercially available VTR for Hi8 (EV-BS3000 manufactured by Sony), the C / N was measured at 7 MHz ± 1 MHz. As a result, the output characteristic of Example 8 was +3.0 dB, which was superior to that of Comparative Example 3. It had the following.

[0053]

[Table 1]

[0054]

The laminated polyester film of the present invention has
It has excellent bending strength in the width direction and very good wear resistance at the ends. Thereby, the film of the present invention can be suitably used for any applications such as a magnetic recording medium field, an electric / electronic field, and a packaging field.
In particular, it can be preferably used for a high-capacity magnetic tape using a thin film.

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Claims (6)

[Claims] An elastic modulus E of 6 GP or less in a film width direction and / or a film longitudinal direction is not more than 15 μm.
a or more and a bending strength index M converted to a thickness of 5 μm.
Is not less than 7.5 × 10 ⁻³ N / m. 2. A flexural strength index M (N) in terms of a thickness of 5 μm in a film width direction and / or a film longitudinal direction.
/ M), and the ratio M / E of the elastic modulus E (GPa) is 1.2 × 10 ⁻³ or more. 3. The laminated polyester film according to claim 1, wherein a heat-resistant resin is laminated on both sides of the polyester film as a base layer. 4. The laminated polyester film according to claim 3, wherein the heat-resistant resin is an aromatic polyamide. 5. The laminated polyester film according to claim 3, wherein the ratio (TL) of the thickness of the heat-resistant resin layer to the total thickness of the film is 1% or more and 50% or less. 6. A magnetic recording medium comprising a laminated polyester film according to claim 1 and a magnetic layer provided on at least one surface.