JPH06210722A - Biaxially oriented laminated polyester - Google Patents

Abstract

PURPOSE:To obtain high electromagnetic conversion characteristics and high burst strength at the time of the formation of a magnetic tape by constituting at least one layer other than the outermost layer based on polyethylene -2,6- naphthalate of polyester of a polyethylene terephthalate component and setting the thickness of this layer to a specific ratio with respect to the whole thickness. CONSTITUTION:A biaxially oriented laminated polyester film is characterized by that at least the outermost layer is composed of polyester based on polyethylene -2,6-naphthalate and at least one layer other than the outermost layer is composed of polyester containing 20wt.% or more of a polyethylene terephthalate component. The thickness of the layer containing 20wt.% or more of the polyethylene terephthalate component is set to 1/50-1/2 the whole thickness of the film. These polyesters are dried to be laminated using two or more extruders, three or more manifolds and a confluent block to form a non- stretched film which is, in turn, biaxially stretched. When a non-sticking roll composed of Teflon or silicone is used, the smoothness of the film is improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially oriented laminated polyester film, more specifically a base film for magnetic tape,
The present invention relates to a biaxially oriented laminated polyester film suitable for capacitors and packaging.

[0002]

2. Description of the Related Art Polyethylene terephthalate as a composite polyester film having three or more layers and polyethylene-2,
There is JP-A-63-197643 for the purpose of suppressing precipitation of oligomers by compounding 6-naphthalate. In addition, polyethylene-2,6-having high mechanical strength is used in order to cope with the thinning of the film for magnetic tape applications.
It is well known that naphthalate films are useful.

[0003]

In the case of the conventional composite polyester film, since the polyethylene terephthalate layer is relatively thick, the high mechanical strength characteristic of polyethylene-2,6-naphthalate cannot be fully utilized. For example, in a magnetic tape application, when the thickness of the tape is reduced as the length of time of the tape is increased, the stiffness of the tape becomes weak, the head touch becomes defective, and the electromagnetic conversion characteristics deteriorate. Further, in the case of a biaxially oriented polyethylene-2,6-naphthalate film having a single layer, although a high elastic modulus is obtained, it is weak against tearing or tearing, and is used during the film manufacturing process, the processing process, or the product as a product. The drawback of tearing and tearing could not be remedied. The present invention provides a film which improves the above-mentioned drawbacks, has a high elastic modulus, has a good head touch when used as a magnetic tape, can obtain high electromagnetic conversion characteristics (RF output), and is resistant to tearing and tearing. The purpose is to do.

[0004]

The present invention comprises at least 3
In a biaxially oriented laminated polyester film having a laminated structure of two or more layers, at least the outermost layer is made of polyester containing polyethylene-2,6-naphthalate as a main component, and at least one layer other than the outermost layer is a polyethylene terephthalate component of 20% by weight. A biaxially oriented laminated polyester film comprising the above polyester, wherein the layer containing 20% by weight or more of a polyethylene terephthalate component is 1/50 to 1/2 of the total film thickness. It is about.

The film of the present invention must have a laminated structure of at least three layers. If there are 3 layers or more, 4 layers will be 5
Although it may be a layer, it is effective to obtain the effect of the present invention particularly in the case of a laminated structure of 3 layers or 5 layers.

At least the outermost polyester of the film of the present invention contains polyethylene-2,6-naphthalate as a main component. Polyethylene in the outermost layer
The proportion of the 2,6-naphthalate component is not particularly limited, but is preferably 80% by weight or more. It should be noted that other polymers may be mixed or copolymerized as long as the effects of the present invention are not impaired.

At least one layer other than the outermost layer of the film of the present invention must be made of a polyester having a polyethylene terephthalate component of 20% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more. In addition, other polymers may be mixed or copolymerized as long as the effects of the present invention are not impaired.

The layer containing 20% by weight or more of the polyethylene terephthalate component in the film of the present invention is 1/50 to 1/2 of the total thickness of the laminated film, preferably 1/50 to 1
/ 3, more preferably 1/50 to 1/5. If it is more than 1/2, the elastic modulus of the film becomes low,
If it is / 50 or less, tearability is not improved, which is not preferable.

Although the Young's modulus of the film of the present invention is not particularly limited, the Young's modulus in the film width direction and the longitudinal direction is Young's modulus in the width direction ≧ 600 kg / mm ² Young's modulus in the longitudinal direction ≦ Young's modulus in the width direction −50 kg / m
When it is m ^2, it is preferable to obtain the effect of the present invention.

The heat shrinkage of the film of the present invention is not particularly limited, but the effect of the present invention is further improved when the heat shrinkage at 150 ° C. in the longitudinal direction of the film is less than 4.0%.

Although not particularly limited, it is effective for obtaining the effects of the present invention when at least one of the outermost layers of the film of the present invention contains inorganic or organic particles. Examples of the particles to be contained at this time include calcium carbonate, colloidal silica, aluminum oxide, zirconium oxide, polydivinylbenzene, silicone, and the like, and even one kind of particles selected from these particles can be used as two or more kinds of particles. You can use a combination.

Next, a method for producing the film of the present invention will be described.

Polyethylene-2,6-naphthalate (hereinafter referred to as 2,6-PEN) and polyethylene terephthalate (hereinafter referred to as PET) used in the present invention may be those obtained by known methods. Further, a mixture of these polymers and another polymer in advance, or a copolymer of other components in the polymerization step may be used. As a method of incorporating inert particles into these polyesters, they may be added before the polymerization, during the polymerization, or after the polymerization, but mixed with ethylene glycol, which is the diol component of the polyester, in the form of a slurry,
A method of dispersing and adding, and a method of mixing the particle powder and the polymer using a vent type twin-screw kneading extruder are preferably used.

As a method of controlling the content of particles, it is preferable to use a method of diluting high-concentration particle master pellets during film formation and extrusion, because the effect of the present invention is further enhanced.

Next, after thoroughly drying these polyesters, using two or more extruders, three or more layers of manifolds, and a confluent block at a temperature of 260 to 330 ° C. for 2,6
-PEN-based polyester is the outermost layer, PE
A polyester having a T component of 20% by weight or more is laminated so as to be a layer other than the outermost layer, melt-extruded from a slit-shaped die, and cooled and solidified on a cutting drum at 20 ° C to 60 ° C to form an unstretched film.

Next, the unstretched film is biaxially stretched,
It is biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However,
It is preferable to use a sequential biaxial stretching method in which stretching is first performed in the longitudinal direction and then in the width direction.

Stretching in the longitudinal direction is carried out by using a commonly used roll, but as preheating and stretching rolls, it is preferable to use a roll made of a non-adhesive material such as Teflon or silicon so that the film surface has good smoothness. Therefore, the electromagnetic conversion characteristics of the magnetic tape are improved, which is preferable. The stretching temperature is 110 to 160 ° C, preferably 115 to 150
A method of stretching at a temperature of 3.5 to 7 times is used. Stretching temperature,
If the stretching ratio is out of this range, uneven stretching, breakage, etc. occur and a film having good properties cannot be obtained.

Stretching in the width direction is preferably carried out using a known tenter at a temperature of 100 to 160 ° C. for 3 to 8 times. If the stretching temperature and the stretching ratio deviate from these ranges, uneven stretching, breakage, etc. occur and a film having good characteristics cannot be obtained. It is particularly effective to obtain a Young's modulus within the range of the present invention by increasing the stretching ratio in the width direction to be higher than the stretching ratio in the longitudinal direction to increase the orientation in the width direction.

The biaxially stretched film may be further stretched in at least one direction.

Next, this stretched film is heat-treated. As a heat treatment condition, it is performed at a constant length of 160 to 230 ° C., preferably 170 to 220 ° C. for 0.5 to 30 seconds. Performing such heat treatment is effective for obtaining the effects of the present invention.

If necessary, the film can be relaxed in the longitudinal direction by a method of utilizing the peripheral speed difference between two or more rolls heated to a temperature equal to or lower than the heat treatment temperature after the heat treatment. . This method is an effective means for obtaining the effects of the present invention.

[0022]

[Measurement Method of Physical Properties and Evaluation Method of Effect] The characteristic values of the present invention are based on the following measurement methods and evaluation criteria.

(1) Young's modulus According to ASTM-D-882, it was measured at 25 ° C. and 65% RH using an Instron type tensile tester.

(2) Thickness ratio of laminated film A profile of peak intensity due to naphthalene ring and benzene ring in the depth direction of the film is obtained by using IR (infrared spectroscopy) while etching the film from the surface,
The thickness of each layer was obtained from the change in each peak intensity, and the thickness ratio of the laminated film was obtained.

When particles are contained in the outermost layer, a profile in the depth direction of the element caused by the particles is obtained by secondary ion mass spectrometry, and the thickness ratio of the laminated film is calculated based on the change in the element concentration. You can also ask.

In addition to the above, it is possible to determine the thickness ratio of the laminated film by recognizing the laminated interface from the change in particle concentration or the difference in contrast due to the difference in polymer by observing the cross section with an electron microscope or the like.

(3) Tear Strength An Elmendorf tear tester manufactured by Toyo Seiki Seisaku-sho, Ltd. was used to measure the tear strength. 50, 8 mm (longitudinal direction)
A film sample of x63, 5 mm (width direction) was taken,
12. Width at a right angle at the center of both knobs along the longitudinal direction.
A 7 mm cut was made and the tearing force for the remaining 50.8 mm was determined. This force was divided by the film thickness to give the tear strength. This measurement was carried out in the longitudinal and width directions of the film, and the tear strengths in both the longitudinal and width directions were both 15
Those having a tear strength of 0 g / mm or more were considered good. If the tear strength is 150 g / mm or less, tearing during film formation and breakage during use as a magnetic tape frequently occur, which is a quality problem.

(4) Particle content It was measured by a usual fluorescent X-ray analysis method.

If necessary, pyrolysis gas chromatography, infrared absorption, Raman scattering, SEM-XMA, etc. were used.

(5) Heat Shrinkage A sample film was cut out with a width of 10 mm and a length of 250 mm,
Two marks are put at intervals of about 200 mm, and the distance is accurately measured (this is Amm. This sample is left in a hot air oven at 150 ° C for 30 minutes under no tension, and then the distance between the marks is measured. Is measured (this is Bmm), and 100 × (A−
B) / A was defined as the heat shrinkage rate.

(6) RF Output The following composition was mixed and dispersed by a ball mill for 48 hours, then 6 parts of a curing agent was added and the resulting kneaded product was filtered through a filter to prepare a magnetic coating liquid, which was then applied to the film. Coating, magnetic field orientation, drying at 110 ° C, calendering with a calendering device (steel roll / nylon roll, 5 steps) at a temperature of 70 ° C and a linear pressure of 200 kg / cm, and then winding into a roll at 70 ° C. Cure for 24 hours, 40 more
Aging was carried out at 72 ° C. for 72 hours to obtain a magnetic recording tape. The obtained magnetic recording tape raw fabric was slit into 1/2 inch to prepare a pancake, and a length of 250 m from the pancake was incorporated into a cassette to obtain a cassette tape. Using a domestic VTR on this cassette tape, a luminance signal was recorded by a television test wave generator, and the luminance signal output (RF output) at the time of reproduction was measured. It should be noted that the one having the smallest output among the respective experimental levels was relatively indicated as the standard 0 dB.

Fe 100 parts Average particle size Length: 0.3 μm Needle ratio: 10/1 Coercive force 2000 Oe ・ Polyurethane resin 15 parts ・ Vinyl chloride / vinyl acetate copolymer 5 parts ・ Nitrocellulose resin 5 parts ・Aluminum oxide powder 3 parts Average particle size: 0.3 μm ・ Carbon black 1 part ・ Lecithin 2 parts ・ Methyl ethyl ketone 100 parts ・ Methyl isobutyl ketone 100 parts ・ Toluene 100 parts ・ Stearic acid 2 parts

[0033]

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

Example 1 1% by weight of polydivinylbenzene particles having a particle diameter of 0.5 μm was contained in pellets of 2,6-PEN obtained by a known method using a vent type twin-screw kneading extruder, and the particles were added. The containing pellets and 2,6-PEN-free pellets were mixed to give a particle content of 0.5% by weight.
It was vacuum dried at 0 ° C. for 6 hours to obtain a polymer A. Further, 1 particle-free PET pellet obtained by a known method was used.
65 parts by weight of the product dried in vacuum at 70 ° C. for 6 hours and 35 parts by weight of particles-free 2,6-PEN pellets dried in vacuum at 170 ° C. for 6 hours were mixed to prepare a polymer B. Polymer A is fed to extruder A, melted at 295 ° C.,
Polymer B is supplied to extruder B and melted at 285 ° C., and after high-precision filtration, each is joined and laminated so that the joining portion is a rectangular three-layer joining block and the core layer is polymer B and the surface layer is polymer A. Then, it is extruded in a sheet form from a fish tail type die with a slit width of 1 mm, and it is 35
The film was wound around a casting drum at ℃ and solidified by cooling to obtain an unstretched film having a thickness of about 150 μm. The surface temperature of this unstretched film is set to 1 by a roll made of silicon.
It was stretched 4.5 times in the longitudinal direction at 30 ° C. This uniaxially stretched film was stretched by a tenter at an ambient temperature of 135 ° C. for 4.8 times and heat-treated at an ambient temperature of 200 ° C. for 3 seconds to obtain a biaxially oriented laminated polyester film having a thickness of 6 μm. The properties of this film are shown in Table 1. The tear strength of this film is 285 g / mm in the longitudinal direction,
The width direction was good at 260 g / mm, and the video output when this film was used as a magnetic tape was 3.5 dB, which was a good value even though the tape was thin.

Examples 2 to 7, Comparative Examples 1 to 5 In the same manner as in Example 1, 2,6-PEN and PET were used.
Content ratio, laminated structure, laminated ratio, stretching method,
A biaxially oriented laminated polyester film having the properties shown in Table 1 was obtained. When the requirements of the present invention were satisfied, both the tear strength and the RF output shown in Table 1 were good. However, when the requirements of the present invention were not satisfied, both the tear strength and the RF output could not be made excellent.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY The present invention has a biaxially oriented laminated polyester having a laminated structure of three or more layers having a layer composed of polyester containing polyethylene-2,6-naphthalate as a main component and a layer containing a certain amount or more of polyethylene terephthalate. It is a film, and is intended to improve the disadvantage of polyethylene-2,6-naphthalate, which is high in mechanical strength characteristic of polyethylene-2,6-naphthalate and is weak against tearing and tearing. In the film forming, processing process and use as a product, the tape is not easily torn or torn, and due to its high elastic modulus, the head touch in the VTR is good and the electromagnetic conversion characteristics are high even if the tape is thinned. Obtainable.

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Claims (4)

[Claims] 1. A biaxially oriented laminated polyester film having a laminated structure of at least three layers, wherein at least the outermost layer is made of polyester having polyethylene-2,6-naphthalate as a main component, and at least one layer other than the outermost layer. Is a biaxially oriented laminated polyester film consisting of polyester with a polyethylene terephthalate component content of 20% by weight or more, and a layer containing a polyethylene terephthalate component content of 20% by weight or more is 1% of the total thickness of the laminated film.
/ 50 to 1/2 The biaxially oriented laminated polyester film. 2. The Young's modulus in the width direction of the film and the Young's modulus in the length direction of the film are Young's modulus in the width direction ≧ 600 kg / mm ² Young's modulus in the length direction ≦ Young's modulus in the width direction−50 kg / m
The biaxially oriented laminated polyester film according to claim 1, wherein the biaxially oriented laminated polyester film is m ² . 3. The heat shrinkage in the longitudinal direction of the film at 150 ° C. is less than 4.0%.
Alternatively, the biaxially oriented laminated polyester film according to claim 2. 4. At least one of the outermost layers contains inorganic or organic particles.
The biaxially oriented laminated polyester film according to any one of 1.