JPH06210721A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PURPOSE:To highly dimensionally reconcile electromagnetic conversion characteristics and a tape edge damage when a polyester film is formed into a magnetic tape by adding particles to the outermost layer at least on a single side and setting the thickness of the outermost layer and the average particle size of the particles to specific relation and setting the Young's modulus of the film in the lateral direction thereof to a specific value. CONSTITUTION:Particles are added to the outermost layer at least on a single side and the relation between the thickness (t) of the outermost layer and the average particle size (d) of the particles is set to the range of 0.2<=t/d<=5 and the Young's modulus of a film in the lateral direction thereof is set to 600kg/mm<2> or more. Polyester films having these characteristics are sufficiently dried to be laminated using two or more extruders, two or more manifolds and a confluent block to form a non-stretched film which is, in turn, biaxially stretched. As preheating and stretching rolls, Teflon or silicone rolls are used in order to improve the surface smoothness of the film. Next, this film is heat- treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film, and more particularly to a biaxially oriented laminated polyester film suitable for magnetic recording media, capacitors and packaging.

[0002]

2. Description of the Related Art As a polyester film containing ethylene naphthalate as a main constituent, Japanese Patent Publication No. 48-41
700, Japanese Patent Laid-Open No. 62-135339 and the like are conventionally known. The polyester film containing ethylene naphthalate as a main constituent is superior in mechanical strength to a polyester film containing ethylene terephthalate as a main constituent, and has a high elastic modulus capable of coping with thinning of the film.

[0003]

However, in the case of the above-mentioned conventional polyester film, high mechanical strength is obtained,
Although the film can be made thinner, the control of the film surface morphology is insufficient, so the electromagnetic conversion characteristics (RF output) when used as a magnetic tape, which is an important characteristic especially for magnetic recording medium applications, are satisfied. It was difficult to say. In addition, with the recent thinning of the tape, the strain is weak especially in the tape width direction and the running property of the tape is insufficient, so the tape meanders while the tape is running and the edge of the tape is damaged and shavings are generated, I could not deal with the trouble that the magnetic surface was damaged. The present invention has improved these drawbacks, and the electromagnetic conversion characteristics (RF
The purpose of the present invention is to provide a film capable of achieving both high output and tape edge damage at a high level.

[0004]

The present invention comprises at least two aspects.
In a polyester film mainly composed of ethylene naphthalate having a laminated structure of at least one layer, particles are contained in at least one outermost layer, and the relationship between the thickness t of the outermost layer and the average particle diameter d of the particles is 0. .2 ≦ t / d ≦ 5, Young's modulus in the film width direction is 600 kg
/ Mm ² or more, and relates to a biaxially oriented laminated polyester film.

The film of the present invention must have a laminated structure of at least two layers. If there are 2 layers or more, 3 layers will be 4
Although it may be a layer, a laminated structure of two layers or three layers is particularly effective for obtaining the effect of the present invention.

At least one outermost layer of the film of the present invention contains particles, and the relationship between the thickness t of the outermost layer and the average particle diameter d of the particles contained in the outermost layer is 0.2≤t / d≤5. Must be in the range. When t / d is out of the above range, the traveling property and the electromagnetic conversion characteristic cannot be compatible with each other. Examples of the particles contained in the outermost layer include crosslinked polydivinylbenzene, colloidal silica, calcium carbonate, zirconium oxide, aluminum oxide and the like, but are not particularly limited. One kind of particles selected from these particles may be used, or two or more kinds of particles may be used in combination. Although not particularly limited, when the average particle size of the particles contained is 0.01 to 2 μm and the content is 0.1 to 20% by weight, it is particularly effective for obtaining the effect of the present invention.

The main constituent of the film of the present invention must be ethylene naphthalate. When the main constituents are other than ethylene naphthalate, it is difficult to obtain the effects of the present invention. In addition, other components may be mixed or copolymerized as long as the effects of the present invention are not impaired.

The Young's modulus in the width direction of the film of the present invention is 60.
It should be 0 kg / mm ² or more. Also preferably the width direction of the Young's modulus 650 kg / mm ² or more, more preferably when the 680 kg / mm ² or more, it is effective in obtaining the effect of the present invention. Furthermore, the Young's modulus in the longitudinal direction of the film is particularly preferably [Young's modulus in the width direction-50 kg / mm < ² >] or less.

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%.

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

As the polyester containing ethylene naphthalate as a main constituent in the present invention, those obtained by a conventionally known method can be used. As a method for incorporating particles into this polyester, it may be added before the polymerization, during the polymerization, or after the polymerization, but it may be added by mixing and dispersing it in a slurry form with ethylene glycol, which is the diol component of the polyester. And a method of mixing particle powder or an aqueous slurry of particles with a polymer using a vent type twin-screw kneading extruder are preferably used.

As a method for controlling the content of particles, if the method of diluting the high-concentration particle master pellet obtained by the above method during film formation and extrusion is used, the effect of the present invention is further enhanced. preferable.

Next, after sufficiently drying these polyesters, the polyester containing particles is at least on one side at a temperature of 260 to 330 ° C. using two or more extruders, two or more layers of manifolds, and a confluent block. Laminate to form a surface layer, melt extrude from a slit-shaped die, and 20 ℃
An unstretched film is prepared by cooling and solidifying on a cutting drum at -60 ° C.

Next, this unstretched film is biaxially stretched and 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, a roll made of a non-adhesive material such as Teflon or silicon is used, and the smoothness of the film surface is good. 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. The stretching may be performed in one stage or in two or more stages. If the stretching ratio is out of this range, uneven stretching, breakage, etc. occur and a film having good properties cannot be obtained.

In the stretching in the width direction, it is preferable to stretch at a temperature of 100 to 160 ° C. for 3 to 8 times using a known tenter. 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 width-direction Young's modulus within the range of the present invention by making the width-direction stretching ratio higher than the length-direction stretching ratio to increase the width-direction orientation.

The biaxially stretched film may be further stretched in at least one direction, especially in the width 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.

[0020]

[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) Stacking Thickness (t) Using a secondary ion mass spectrometer (SIMS), the concentration ratio of the element derived from the highest concentration of particles in the film and the carbon element of polyester ( M ⁺ / C ⁺ ) is used as the particle concentration, and analysis is performed in the thickness direction 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. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again. The depth at which the particle concentration of this concentration distribution curve becomes 1/2 of the maximum value (this depth is deeper than the maximum value) was determined and used as the laminated thickness. Measurement conditions are as follows.

Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA 3000 manufactured by ATOMIKA Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 kV Primary ion current: 200 nA Raster area: 400 μm □ Analytical area: Gate 30% Measured vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUN: 0.5 kV-3.0 A If the particles contained in the outermost layer are organic particles, SI
Since measurement by MS is difficult, it is possible to obtain the laminated thickness by performing the same depth direction analysis as described above by X-ray photoelectron analysis, infrared analysis, etc. while etching from the surface.

Further, by observing the cross-section with an electron microscope or the like, it is possible to recognize the lamination interface and obtain the lamination thickness ratio from the change in particle concentration and the difference in contrast due to the difference in polymer.

(2) Average particle size (d), number of particles The polymer is removed from the film by a plasma ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. SEM magnification is about 20
00 to 100,000 times, and one side of each measurement visual field is appropriately selected from 10 to 50 μm. The average particle size (d) was obtained by the following equation from the particle size and its volume fraction when the number of particles was 5000 or more by changing the observation location.

D = Σdi · Nvi Here, di is the particle size, and Nvi is the volume fraction of particles of that size. The number of particles is calculated from the volume fraction for those satisfying the relationship between the laminated thickness and the average particle diameter, and converted per 1 mm ² .

When particles are damaged in the plasma ashing method, the cross section of the film is observed with a transmission electron microscope (TEM) at a magnification of 3000 to 100000. The section thickness of the TEM was set to about 1000 angstroms, 100 locations or more were measured at different locations, and the average particle diameter (d) was determined from the above formula.

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

(4) Heat Shrinkage A sample film having a width of 10 mm and a length of 250 mm was cut out,
Put two marked lines at intervals of about 200 mm and measure the intervals accurately (this is Amm). This sample film was allowed to stand in a hot air oven at 150 ° C. under no tension for 30 minutes, then the interval between the marked lines was measured (this is Bmm), and the heat shrinkage rate was 100 × (A−B) / A. And

(5) RF Output The following composition was mixed and dispersed by a ball mill for 48 hours, and 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. Coating, magnetic field orientation, drying at 110 ° C, calendering with a calendering device (steel roll / nylon roll, 5 stages) at a temperature of 70 ° C and a linear pressure of 200 kg / cm, and 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 to 1/2 inch to prepare a pancake, and a length of 250 m from the pancake was incorporated into a VHS cassette to form a cassette tape.
A household VTR was used for this cassette tape, and a luminance signal was recorded by a television test waveform generator, and the luminance signal output (RF output) at the time of reproduction was measured. Among the experimental levels, the one with the smallest output was relatively displayed 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

(6) Tape edge damage Similar to the measurement of RF output, a video tape assembled in a cassette, 250 m is fast-forwarded by a commercially available VCR and rewound repeatedly 50 times, and the end surface of the tape is observed with a scanning electron microscope or the like. Then, the tape was compared with the end surface of the tape before the measurement and judged according to the following criteria.

Almost the same as the end surface before measurement: ○ Slightly attached shavings and damaged the magnetic layer: △ Large amount of shavings attached, large destruction of magnetic layer: ×

[0033]

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

Example 1 Polydivinylbenzene particles having a particle size of 0.35 μm were added to pellets of polyethylene-2,6-naphthalate obtained by a known method by using a vent type twin-screw kneading extruder. The amounts were mixed so as to be 3% by weight.
This particle-containing pellet was vacuum dried at 170 ° C. for 6 hours to obtain a polymer A. Particle-free polyethylene-2,6
Polymer 95 was mixed with 95 parts by weight of naphthalate pellets vacuum-dried at 170 ° C. for 6 hours to prepare polymer B. Polymer A is supplied to extruder A, polymer B is supplied to extruder B, and they are melted at 295 ° C. After high-precision filtration of each, they are joined and laminated by a two-layer merging block having a rectangular merging portion, and a fish with a slit width of 1 mm. Extruded in sheet form from the tail die, wound around a casting drum at 30 ° C by an electrostatically applied casting method, cooled and solidified to a thickness of about 14
An unstretched film of 5 μm was obtained. This unstretched film was stretched 3.3 times in the longitudinal direction at a roll surface temperature of 130 ° C. by a Teflon roll, and then 1.3 times at a roll surface temperature of 135 ° C. by a silicon roll. This uniaxially stretched film was heated at an ambient temperature of 135 with a known tenter.
The film was stretched 5.0 times at 0 ° C. and heat-treated at an ambient temperature of 195 ° C. for 3 seconds to obtain a biaxially oriented laminated polyester film having a thickness of 6.5 μm. The properties of this film are as shown in Table 1. The t / d and the Young's modulus in the width direction were values satisfying the claims of the present invention, and the Young's modulus in the longitudinal direction, the number of particles, and the heat shrinkage ratio were also preferable values. . This film is measured (6)
The characteristics when formed into a magnetic tape by the method described are as shown in Table 1, and a high RF output of 3.6 dB was obtained, and there was almost no tape edge damage, which was good.

Examples 2 to 6 and Comparative Examples 1 to 4 In the same manner as in Example 1, the biaxially oriented laminated polyester film having the characteristics shown in Table 1 was obtained by changing the t / d ratio and the number of particles. Got When the requirements of the present invention were satisfied, both the RF output and the tape edge damage shown in Table 1 were good.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY The present invention is a biaxially oriented laminated polyester film having a laminated structure of two or more layers containing ethylene terephthalate as a main constituent, and has a laminated thickness of at least one outermost layer and particles contained therein. By setting the average particle size to a specific range and setting the Young's modulus in the width direction to a certain value or more, high mechanical strength peculiar to ethylene naphthalate and control of the film surface morphology can be realized, especially when used as a magnetic medium tape It is possible to cope with the reduction of the film thickness, obtain high electromagnetic conversion characteristics, and prevent damage to the tape edge during tape running.

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Claims (4)

[Claims] 1. A polyester film containing ethylene naphthalate as a main constituent, which has a laminated structure of at least two layers, contains particles in at least one outermost layer, and has a thickness t of the outermost layer and an average of the particles. The relationship of the particle size d is in the range of 0.2 ≦ t / d ≦ 5, and the Young's modulus in the film width direction is 600 kg.
/ Mm ² or more, a biaxially oriented laminated polyester film. 2. The biaxially oriented laminated polyester film according to claim 1, wherein the Young's modulus in the longitudinal direction of the film is [Young's modulus in the width direction-50 kg / mm ² ] or less. 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. The number of particles having a particle size such that the relationship between the thickness t of the outermost layer and the average particle size d of the particles satisfies 0.2 ≦ t / d ≦ 5 is 3000 to 10 million /
The biaxially oriented laminated polyester film according to claim 1, which has a size of mm ² .