JP2890710B2 - Biaxially stretched polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a biaxially stretched polyester film, and more particularly, to a film excellent in F5 value and Young's modulus (waist strength), which has abrasion resistance and thermal dimension. Magnetic tape with excellent stability,
The present invention relates to a biaxially oriented polyester film suitable for use in printer ribbons, packaging materials, condensers, and other industrial materials.

[Conventional technology]

Conventionally, biaxially stretched polyester films are added with particles to impart lubricity, running properties, anti-blocking properties, etc. when processed or made into a product. However, specific particles are added because the abrasion resistance deteriorates. (Eg, Japanese Patent Publication No. 59-29610 and Japanese Patent Application Laid-Open No. 63-230741).
Such).

Further, in order to reduce the thickness of the biaxially stretched polyester film, to increase the F5 value and Young's modulus, to strengthen the stiffness, JP-A-61-241128 and JP-A-50-133276, etc. There is known a method in which the film is stretched in two stages under specific conditions in the longitudinal direction and then horizontally stretched.

[Problems to be solved by the invention]

 However, the above method has the following problems.

1) Since it is limited to a specific particle type, inexpensive particles cannot be used.

2) Sufficient abrasion resistance and abrasion resistance cannot be obtained even when limited to a specific particle type.

3) Particles having a large particle size are excellent in slipperiness and running properties, but have poor wear resistance, so that the particle size is extremely limited.

4) In the above-mentioned method of increasing the F5 value and the Young's modulus, the wear resistance is deteriorated more than the ordinary stretching method, and satisfactory wear resistance cannot be obtained even when the particle surface is considered.

5) When the F5 value or the Young's modulus is increased, the thermal dimensional stability is deteriorated (the thermal shrinkage is also increased).

An object of the present invention is to solve the above-mentioned conventional problems and to provide a biaxially oriented polyester film having a large F5 value and Young's modulus, and excellent in abrasion resistance and thermal dimensional stability.

[Means for solving the problem]

In order to achieve the above object, the present invention provides the following constitution, that is, biaxial stretching in which particles are contained, and the sum of the F5 value in the longitudinal direction and the width direction (F5 value sum) is 25 kg / mm ² or more. In a polyester film, the void volume in the film and F5
A biaxially stretched polyester film characterized in that the relationship with the sum of values satisfies the following expression.

Void volume / F5 value sum ≦ 300 (μm ³ / kg) Also, in a biaxially stretched polyester film containing particles and having a F5 value sum of 25 kg / mm ² or more, while satisfying the features of the present invention described above, Further, a biaxially stretched polyester film is characterized in that the relationship between the heat shrinkage in the longitudinal direction and the F5 value in the longitudinal direction of the film satisfies the following expression.

Longitudinal heat shrinkage / longitudinal F5 value ≦ 0.1 (% V / kg / mm ² ) The polyester in the present invention is a polymer obtained by condensation polymerization from a diol and a dicarboxylic acid,
Dicarboxylic acids include terephthalic acid, isophthalic acid,
Representative examples include phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, and diols such as ethylene glycol, trimethylene glycol,
These are represented by tetramethylene glycol, cyclohexanedimethanol and the like. Specifically, for example, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate,
And polyethylene-2,6-naphthalenedicarboxylate.

In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferred.

Of course, these polyesters may be homopolyesters or copolyesters. Examples of the copolymerization component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid, and phthalic acid. And dicarboxylic acid components such as isophthalic acid, 2,6-naphthalenedicarboxylic acid and 5-sodium sulfoisophthalic acid.

The biaxially stretched polyester film of the present invention is a biaxially stretched film made of the above polyester, and the sum of the F5 value in the longitudinal direction and the width direction (F5 value sum) needs to be 25 kg / mm ² or more. If it is less than 25 kg / mm ^2, there is a problem that the strength is insufficient when the film is thinned for the above-mentioned applications, for example, magnetic tape applications, and it cannot be used. Also, the F5 value in each direction does not necessarily need to be balanced, but
F5 value ≧ F5 value in the width direction is preferable, and the F5 value in the width direction is 12
It is more preferably at least kg / mm ² .

Further, the biaxially stretched polyester film of the present invention needs to contain particles. Here, the particles of the present invention refer to all particles including internally precipitated particles, inert inorganic particles, and organic particles.

Specific examples of the particles include particles formed by combining at least one compound selected from the group consisting of a calcium compound, a magnesium compound, a manganese compound, and a lithium compound, which is added during the synthesis of the polyester, with the polyester constituent component.

Further, specific examples of the inert inorganic particles include, but are not limited to, substantially spherical silica particles resulting from colloidal silica, titanium oxide, calcium carbonate, aluminum oxide, barium sulfate, and the like. .

Examples of the organic particles include silicon particles, polyimide particles, crosslinked (styrene-divinylbenzene) copolymer particles, crosslinked (ethylstyrene-divinylbenzene) copolymer particles, crosslinked polyester particles, and Teflon particles. (Ethylstyrene-divinylbenzene) copolymer particles are preferred. Crosslinking (ethylstyrene-
Among divinylbenzene) copolymer particles, it is particularly preferable that 30% or more of divinylbenzene is copolymerized.

The average particle size of these particles is preferably 0.01 to 4.0 μm, and more preferably 0.05 to 2.0 μm. If the thickness is less than 0.01 μm, the slipperiness and the running property are deteriorated. For those exceeding 4.0 μm,
Abrasion resistance deteriorates.

The content of the particles is preferably 0.001 to 1.0 wt%, more preferably 0.005 to 0.8 wt%. If it is less than 0.001% by weight, the slipperiness and running properties deteriorate, and if it exceeds 1.0% by weight, the wear resistance deteriorates.

The void volume / F5 value sum in the present invention needs to be 30 μm ³ / kg or less, preferably 200 μm ³ / kg or less, more preferably 150 μm ³ / kg or less. If the void volume / F5 value sum exceeds 300 μm ³ / kg, the wear resistance deteriorates,
In magnetic tape applications, dropout is caused, and in printer ribbons, the print head is contaminated by scraping, making clear printing difficult. In addition, in packaging applications, problems such as deterioration of the barrier property of water vapor and oxygen are caused, and in capacitors applications, a reduction in withstand voltage is caused.

In the present invention, the heat shrinkage in the longitudinal direction /
The ratio of the F5 value needs to be 0.1% / kg / mm ² or less, preferably 0.08% / kg / mm ² or less, more preferably 0.05% / kg / mm ²
The following is good. If it exceeds 0.1% / kg / mm ² , heat resistance is poor and it cannot be used for each application.

As a method for producing the polyester film of the present invention,
A raw material obtained by sufficiently drying a polyester containing particles by a vacuum dryer is supplied to an extruder, extruded at a temperature within the range of the melting point of the polymer to within the range of (the melting point of the polymer + 50 ° C.), discharged from a die, and cast.

The cast film (or sheet) is heated in the longitudinal direction in a temperature range of (glass transition temperature (hereinafter referred to as Tg) +30) to (Tg + 60) ° C, preferably (Tg + 35) to (Tg + 50) ° C.
Stretching is performed 2.5 times or less, preferably 2.3 to 1.2 times, and at a temperature lower than this temperature, the second stage is further stretched in the longitudinal direction within a range of 2.0 to 5.5 times. At this time, it is important to note that the above-mentioned stretching temperature and magnification are of course important.
It is necessary to keep the temperature of the film after the second stage stretching below the second stage stretching temperature, while maintaining the film temperature at the second stage stretching temperature. When this temperature is once cooled to a temperature equal to or lower than the second-stage stretching temperature and then raised again to perform the second-stage stretching, the void volume is greatly increased. In this step, 10%
It is preferable not to give the above elongation and relaxation. Beyond this range, the void volume increases. As the void volume increases, wear resistance and abrasion resistance deteriorate.

The stretching method in the longitudinal direction is not necessarily limited to the two-stage stretching, and may be at least two stages.
The next stretching step is performed while keeping the stretching temperature lower than the previous stretching temperature and maintaining the film temperature after stretching so as not to fall below the next stretching temperature. It is important not to give elongation or relaxation of 10% or more during this time.

Further, in this stretching, the stretching speed is also an important factor, and the stretching speed in the first stage is 50,000% / min or less, and the stretching speed in the second stage is
It is preferably at least 50,000% / min.

These various stretching conditions are also important for imparting thermal dimensional stability in the longitudinal direction.

After stretching in the longitudinal direction in this way, stretch in the width direction by 2.5 to 5.0 times using a conventional tenter, and then heat-set (if necessary, relaxation heat treatment in the width direction may be performed). Thus, the film of the present invention is obtained.

In order to further improve the thermal dimensional stability in the longitudinal direction, a relaxation heat treatment may be performed in a known tenter or after leaving the tenter.

(Effect of the present invention)

By providing a particle-containing biaxially stretched polyester film having a specific range of void volume / sum of F5 value or longitudinal heat shrinkage / longitudinal F5 value, the following excellent effects are obtained.

Even when the F5 value and Young's modulus were large, the biaxially stretched polyester film having excellent wear resistance, abrasion resistance and scratch resistance was obtained by reducing the void volume.

In addition, since the film type is not limited, the film surface can be freely designed and inexpensive particles can be used.

Furthermore, even when the particle diameter becomes large, the void volume is suppressed, and the running property and the slipping property are further improved, and the one having excellent wear resistance, abrasion resistance and scratch resistance is obtained.

In addition, even if the F5 value was large, a material having a small heat shrinkage was obtained as compared with a known stretching method, and a useful biaxially stretched polyester film having a small dimensional change due to heat during post-processing or use was obtained. .

〔Evaluation methods〕

(1) Young's modulus Measured at 25 ° C. and 65% RH using an Instron tensile tester according to ASTM-D-882.

(2) F5 value Pulled in the same way as the tensile test method above, 5%
It was represented by the strength at the time of elongation (kg / mm ² ).

(3) Glass transition point (Tg), melting point (Tm) Measured using a DSC-II type manufactured by PerkinElmer.

(4) Void volume A film cut into a rectangle is placed on a slide glass, and a few drops of liquid paraffin are dropped on it.
Place a cover glass on it and mount the film with liquid paraffin. When this is placed on an optical microscope ("Metaloplan" manufactured by Rights) and observed by a transmission method (objective lens 32 times, eyepiece 8 times), black spots are scattered inside the film. The number and area of these black spots were measured using an image processing machine (Cambridge Instrument Inc., Image Analyzing Computer, Containet 72).
0). After converting this area into a circle equivalent diameter, the void volume (μm ³
/ Mm ² ).

(5) Particle content The sample was sufficiently washed with methanol to remove surface deposits, 2.7 kg of o-chlorophenol was added to 300 g of the washed and dried sample, and the temperature was raised to 100 ° C with stirring, and the temperature was raised. Thereafter, the polyester portion is left to stand for another hour to dissolve the polyester portion. However, when the polyester portion does not dissolve due to, for example, a high degree of crystallization, the above-described dissolving operation is performed after dissolving once and rapidly cooling.

Next, coarse insoluble matter such as dust contained in the polyester is filtered off with a G-1 glass filter and removed.
This is subtracted from the sample weight of the on-furnace material.

Equipped with a rotor RP30 in the Hitachi 40P ultra-stretching machine for separation, and after injecting 30cc of the filtered solution into each cell with the above glass filter, rotate the rotor at 4500rpm to confirm that there is no abnormal rotation. Thereafter, the inside of the rotor is evacuated, the rotation speed is increased to 30,000 rpm, and the particles are centrifuged at this rotation speed. Completion of the separation is approximately 40 minutes later, but this confirmation is made, if necessary, when the light transmittance at 375 mμ of the liquid after the separation becomes a constant value higher than that before the separation. After the separation, the supernatant is removed by a gradient method to obtain separated particles.

Since the separated particles may contain a polyester component due to insufficient separation, o-chlorophenol at room temperature is added to the collected particles, and after substantially uniform suspension, the mixture is again subjected to ultracentrifugation. This operation must be repeated until the particles described below are dried and then subjected to scanning differential calorimetry to detect no melting peak corresponding to the polymer.

Finally, the separated particles thus obtained are heated at 120 ° C., 1
Vacuum dry for 6 hours and weigh.

The separated particles obtained by the above operation include both the internally precipitated particles and the inert inorganic particles. For this reason, it is necessary to separately determine the amount of internal particles and the amount of inert inorganic particles.First, quantitative analysis of the metal content of the separated particles is performed, and Ca, L
Determine the content of i and the content of metals other than Ca and Li.

Next, the separated particles are heated under reflux in a three-fold molar amount of ethylene glycol for 6 hours or more, and then ethylene glycol is distilled off to 200 ° C. or more to depolymerize, whereby only the internal particles are dissolved. The separated particles obtained by centrifuging the remaining particles are dried and weighed to obtain the amount of inert inorganic particles, and the difference from the initial total amount of separated particles is used as the amount of internal particles.

(6) Content of organic particles A solvent that dissolves the polyester but does not dissolve the particles is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content.
Further, if necessary, for example, when two or more kinds of particles are mixed, it can be quantified using pyrolysis gas chromatography, infrared spectroscopy, X-ray fluorescence analysis, Raman scattering, SEM-XMA, or the like. .

(7) Runnability The film was slit to 1/2 inch, and the tape was run in a 20 ° C, 60% RH atmosphere using a tape runnability tester TBT-300 (Yokohama System Laboratory Co., Ltd.). Was determined from the following equation to evaluate the running property.

μK = 0.733 log (T ₁ / T ₀ ) where T ₀ is the entrance tension and T ₁ is the exit tension. The guide diameter is 6mm, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 180 °, and the running speed is 3.3cm / sec.

(8) Abrasion resistance The film is slit to 1/2 inch, and the tape is repeatedly run using a tape running tester and a plastic guide (made of polyacetal) as a guide pin.
After running at a running speed of 3.3 cm / sec for 60 minutes, observe the plastic guide surface with an optical microscope to see any scratches on the surface.

When there were no scratches, the abrasion resistance was good; when many scratches occurred, the abrasion resistance was poor.

(9) Sharpness resistance One edge of the film is vertically pressed into a tape slit to a width of 1/2 inch, and the film is further pushed in by 0.5 mm and run for 20 cm (running tension: 500 g, running speed: 6.7 cm /
Seconds). At this time, the height of the shavings on the film surface attached to the tip of the single blade was read with a microscope, and the height was determined as the shaving amount (unit: μ).
m).

When the scraping amount is 8 μm or less, the scraping resistance: good, 8
If it exceeds μm, the chipping resistance was determined to be poor. This 8
The value of μm is a critical value as to whether or not abrasion powder generated by abrasion of the film surface during film processing or running as a product affects product quality.

(10) Intrinsic viscosity It was measured at 25 ° C. using o-chlorophenol.

(11) Thermal shrinkage rate Cut the sample to a width of 10 mm and a length of 30 cm, insert a line at the center of the sample at a position of 20 cm, apply a load of 3 g, and treat in a oven at 150 ° C for 30 minutes. The length (L) was measured, calculated by the following equation, and displayed.

Heat shrinkage (%) = (20−L) / 20 × 100 (12) Print clarity The following hot melt ink was applied to the film of the present invention by a hot melt method to prepare a heat-sensitive transfer material. A 0.8 μm polyether-modified silicon layer was coated as a heat-resistant lubricant layer on the back surface, and was used for evaluation.

[Hot-melt ink composition] 100 parts by weight of carnauba wax 30 parts by weight of microcrystalline wax 15 parts by weight of vinyl acetate / ethylene copolymer 20 parts by weight of carbon black Thermal transfer printer BC-8MKI manufactured by Autonics is evaluated.
Using I, applied voltage with a thermal head with a head resistance of 500Ω
Printing was performed at 13 V and a pulse width of 0.8 msec, and 100 characters after printing 1000 characters were evaluated from the following viewpoints.

All prints with clear prints were marked as good and marked with a circle, and those with clearly distorted, missing, or uneven thickness were marked as unusable with a mark x. In addition, there is unevenness of thickness,
Those with no distortion or omission are indicated by △.

(13) Sharpness by thermal head Prints in the same way as (12),
It was observed and evaluated with a 100 × optical microscope.

If the area of contamination of the head is less than 20%, it is judged as good,
3030% are indicated by Δ, and those exceeding 30% are indicated by X as defective.

〔Example〕

Hereinafter, the present invention will be described based on examples, but is not necessarily limited thereto.

Examples 1-2, Comparative Examples 1-2 Polyethylene terephthalate (I) containing 0.3 wt% of SiO ₂ particles having an average particle size of 0.2 μ as a polyester.
V = 0.60), vacuum dried at 180 ° C., supplied to an extruder, melted at 290 ° C., discharged from a T-die, and cast on a cooling drum.

This sheet is first stretched 2.8 times in the longitudinal direction by a roll group heated to 90 ° C, then stretched 4.5 times in the width direction at 90 ° C, and further stretched 1.8 times in the longitudinal direction by a roll group heated to 120 ° C,
Heat treatment was performed with a roll at 200 ° C. (Comparative Example 1).

In Examples 1 and 2, the cast sheet was heated to 105 ° C.
In the longitudinal direction, 1.6 times (Example 1) and 2.0 times (Example 2) were stretched in the first stage, respectively, and subsequently maintained at a temperature of 80 ° C., and then stretched in the second stage in the longitudinal direction by 3.5 times. . This film was once cooled to Tg or less, stretched 4.5 times with a tenter (transverse stretching machine) heated to 90 ° C., and subsequently relaxed in the 5% width direction at a temperature of 200 ° C. In Comparative Example 2, the stretching was the same as that in Example 1, but after the completion of the first stretching,
C., and then heated to 80.degree. C., the second-stage stretching temperature. The thickness of each of the films was adjusted by the discharge amount so as to be 6 μm after the stretching heat treatment.

The results are shown in Table 1. As is clear from the results, when the sum of void volume / F5 value is within a specific range,
It turns out that what was excellent in abrasion resistance and shaving property was obtained.
Also, in print ribbon applications, there is no change due to the heat of the thermal head, and excellent print clarity can be obtained.
Also, it can be seen that a thermal head free from wear and dirt can be obtained.

Continuation of front page (56) References JP-A-63-112631 (JP, A) JP-A-63-235337 (JP, A) JP-A-59-127730 (JP, A) JP-A-2-63895 (JP) JP-A-58-153232 (JP, A) JP-A-3-246814 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 55/02-55/28 C08J 5/18

Claims (2)

(57) [Claims] A biaxially stretched polyester film containing particles and having a sum of the F5 value in the longitudinal direction and the width direction (hereinafter referred to as the F5 value sum) of 25 kg / mm ² or more, wherein the void volume in the film is A biaxially stretched polyester film, wherein the relationship with the F5 value sum satisfies the following expression. Void volume / F5 value sum ≤ 300 (μm ³ / kg) 2. A biaxially stretched polyester film containing particles and having a sum of F5 values of 25 kg / mm ² or more, the relationship between the heat shrinkage in the longitudinal direction and the F5 value in the longitudinal direction of the film satisfies the following expression. The biaxially stretched polyester film according to claim 1, wherein: Longitudinal thermal shrinkage rate / longitudinal F5 value ≦ 0.1 (% / kg / mm 2)