JP3044765B2 - Polyester film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester film, and more particularly, to a base film for a magnetic tape and a polyester film suitable for use in capacitors and packaging.

[Prior Art] As a polyester film, a film in which calcium carbonate particles are added to polyester (for example, JP-A-60-197755) is known.

[Problems to be Solved by the Invention] In recent years, the speed of the magnetic agent application step and the slitting step in the magnetic tape manufacturing process in magnetic media applications and the printing process in the packaging application have been increased, and the surface of the base film has been shaved during high-speed running. There is a demand for a polyester film having good properties. However, the above-mentioned conventional polyester film is insufficient in sharpness at high speed, which causes trouble in each process.

In recent years, the demand for soft tape for magnetic media has been increasing, and the speed of the soft tape dubbing process has been increasing, and image quality degradation at high speed dubbing has become a problem. There is a need for less polyester films for magnetic tape bases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester film which solves the above-mentioned problems, has good film sharpness at high speed, and has little deterioration in image quality even when dubbing at high speed (hereinafter, high-speed dubbing property).

Means for Solving the Problems In order to achieve the above object, the present invention provides a film having a particle flatness of more than 1.5 and not more than 10 and an average particle diameter of 0.01 or less.
It contains 0.002% by weight to 10% by weight of elliptical calcium carbonate particles having a size of not less than 5 μm and not more than 5 μm, and the ratio (σ / h) between the standard deviation σ of the projection height on the film surface and the average projection height h *.
*) Is 1.0 or less, and the thickness orientation index is 1.2 or less.

Although the polyester of the present invention is not particularly limited, polyethylene terephthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylate, polyethylene 2,6-naphthalate, polybutylene terephthalate and the like are usually used. Among them, polyethylene terephthalate is preferred.

The particle flatness of the calcium carbonate particles used in the film of the present invention must be greater than 1.5 and less than or equal to 10, preferably greater than 1.5 and less than 5.0, more preferably greater than 1.5 and less than 2.5. When the particle flatness of the ellipsoidal calcium carbonate particles is smaller than the above range, it is not preferable because projections having a preferable shape cannot be obtained on the film surface and the high-speed shaving property is poor. On the other hand, if the particle flatness is larger than the above range, the running property is insufficient, and the high-speed dubbing property is unfavorable.

The average particle size of the ellipsoidal calcium carbonate in the film must be 0.01 μm or more and 5 μm or less, preferably 0.05 μm or more and 3 μm or less. If the average particle size in the film is smaller than the above range, the high-speed dubbing property is undesirably poor. On the other hand, if the average particle size in the film is larger than the above range, the surface of the film is too rough, resulting in poor high-speed shaving properties.

The content of the ellipsoidal calcium carbonate particles used in the film of the present invention is 0.002% by weight or more and 10% by weight or less,
Preferably, it must be 0.005% by weight or more and 5% by weight or less. When the content in the film is less than the above range, the high-speed dubbing property is unfavorably deteriorated. On the other hand, when the content in the film is larger than the above range, the high-speed shaving property becomes poor, which is not preferable.

The thickness orientation index of the film of the present invention needs to be 1.2 or less, preferably 1.1 or less. When the thickness orientation index of the film is larger than the above range, the effect of the present invention cannot be obtained, which is not preferable.

It is desirable that the relative standard deviation of the particles in the film of the present invention is 0.7 or less, preferably 0.5 or less, and more preferably 0.4 or less, in order to improve both high-speed scraping and high-speed dubbing.

Standard deviation σ of projection height on film surface in the present invention
And the ratio of the average protrusion height h * (σ / h *) to 1.0 or less, and preferably 0.8 or less is more desirable in order to improve both high-speed shaving and high-speed dubbing.

The fact that the crystal form of the ellipsoidal calcium carbonate in the present invention has a vaterite structure is effective for obtaining the effects of the present invention.

In addition, inert particles other than the above-mentioned elliptical calcium carbonate particles and internally precipitated particles may be used in combination as long as the effects of the present invention are not impaired. Examples of the inert particles include aluminum oxide, titanium dioxide, a crosslinked ethylstyrene-divinylbenzene copolymer, and the like. Particularly, the use of fine inert particles in combination is preferable in further improving the properties of the film.

Furthermore, the average surface roughness of the film of the present invention is not particularly limited, but the average surface roughness of at least one side is 0.003 to 0.060.
When the thickness is in the range of μm, it is desirable because the high-speed shaving property is improved.

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

First, as a method of incorporating elliptical calcium carbonate particles into a predetermined polyester, it may be added before, during, or after the polymerization, but the slurry may be added to the diol component of the polyester, such as ethylene glycol. It is preferable to use a method of mixing, dispersing, and adding. As a dispersion method, a medium dispersion method in which fine glass beads or the like are dispersed as a medium and then the glass beads are removed is preferable.

Also, a method of kneading powder of ellipsoidal calcium carbonate or water slurry with pellets of polyester to which no particles are added using a biaxial kneading extruder of a vent type is also known in which particles are uniformly dispersed and added. This method is preferable.

As a method of adjusting the content of particles, it is preferable to use a method of diluting a high-concentration master pellet at the time of film formation, since the effect of the present invention is further increased.

Next, after sufficiently drying this polyester, it is supplied to a known melt extruder, and after passing through a filtration filter, 260 to 320 ° C.
Melt extruded from a slit-shaped die and cooled and solidified to produce an unstretched film. The draft ratio at the time of casting (slit width of the die / thickness of the unstretched film) is 5 to 30.
The value of the degree is effective for obtaining the effect of the present invention.

Next, the unstretched film is biaxially stretched and biaxially oriented. As the 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 performed first in the longitudinal direction and then in the width direction.

Stretching in the longitudinal direction is performed at 70 to 150 ° C. using a method in which the film is stretched 4 to 5 times in two or three stages. In the case of two-stage stretching, a method in which the first stage is stretched 1.2 to 2 times at 100 to 150 ° C., and the second stage is stretched 1.5 to 4 times at a lower temperature than the first stage,
In the case of three-stage stretching, the first and second stages are stretched 1.2 to 3 times at 100 to 150 ° C. so that the stretching ratio of the second stage is higher than that of the first stage. Lower temperature than the second stage
A method of stretching 1.5 to 4 times is particularly preferable. Such a stretching method is effective in obtaining the effects of the present invention because the stretching ratio can be increased without increasing the orientation of the film and the heights of the protrusions on the film surface can be made uniform.

The stretching in the width direction is preferably performed 3 to 4 times at 80 to 120 ° C.

Further, the biaxially stretched film may be further stretched in at least one direction.

If necessary, the stretched film can be heat-treated. The heat treatment conditions in this case are:
It is preferably carried out at a temperature of 150 to 220 ° C, preferably 170 to 210 ° C for 0.5 to 30 seconds.

In addition, a known composite extruder at the time of melt extrusion, that is, forming a composite polyester film of two or more layers using two or more extruders, a manifold of two or more layers, or a merging block can obtain the effects of the present invention. More preferred above.

[Function] The film of the present invention has characteristics of particles by limiting the type and shape of the particles contained, setting the particle diameter and the amount of particles to be in specific ranges, and limiting the orientation state in the thickness direction of the film. It is estimated that the effects of the present invention were obtained to the fullest extent.

[Method of Measuring Characteristics] The characteristic values of the present invention are based on the following measuring methods and evaluation criteria.

(1) Particle flatness of the particles in the film The film containing the particles is made into an ultra-thin section with a thickness of 1000 mm perpendicular to the plane of the film, using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.). , About 100,000 times, 100
Observing the particles in the field of view, the longest diameter of each particle (D1),
Find the shortest diameter (D2). The value determined by the following equation from the determined longest diameter and shortest diameter was defined as the particle flatness.

Particle flatness = Σ (D1 / D2) / NN: Total number of particles (2) Average particle diameter and relative standard deviation of the particles in the film Permeation through the film containing the particles in the same manner as in the property measurement method (1) The particles were observed with a scanning electron microscope, the circle-equivalent diameter was measured for 100 visual fields, and the average particle diameter and relative standard deviation were determined. Here, the relative standard deviation means a value obtained by dividing the standard deviation of a particle by the average diameter of the particle.

(3) Particle content 100 g of the polyester is added to a solvent in which the polyester is dissolved and the particles are not dissolved, and heated to completely dissolve the polyester. This solution is centrifuged at 30,000 rpm for 40 minutes using an ultracentrifuge 55P-72 manufactured by Hitachi Koki Co., Ltd., and the obtained particles are dried in vacuum. When a melting peak corresponding to polyester is observed when the particles are measured by a scanning differential calorimeter, a solvent is again added to the particles, and after heating and dissolving, centrifugation is performed. When no melting peak is observed, the weight of the particles is determined. This weight was divided by 100 grams and the percentage was taken as the content.

 Usually, about three centrifugation operations are sufficient.

If necessary, the quantification is performed using pyrolysis gas chromatography, infrared absorption, Raman scattering, SEM-XMA, or the like.

(4) Protrusion height standard deviation σ and average protrusion height h * 2 detector type scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-sectional measuring device [PMS-1, manufactured by Elionix Co., Ltd.] ], The measured height of the projections when scanning with the height of the flat surface of the film surface as 0 was sent to an image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] (512 × 512 pixels). First, the film surface projection image is reconstructed. The highest value of the measured individual projections is defined as the height of the projection, and the projection height of each individual projection is determined. This measurement was repeated 500 times in different places, and the average height was defined as the average projection height h *.

Further, the standard deviation of the above-mentioned measured projection height was obtained and defined as the projection height standard deviation σ of the film surface.

The magnification of the scanning electron microscope is usually 3000 times, but an optimum magnification can be selected from the range of 2000 to 5000 times depending on the size of the projection.

(5) High-speed shaving property 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 200 m (running tension: 100 g, running speed: 250 m /
Minutes). 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 shaving amount (unit: μ)
m). For at least one side, this shaving amount is 150μm
In the following cases, it was determined that the abrasion resistance was good: when it exceeded 150 μm, the abrasion resistance was poor. The value of this shaving amount: 150 μm is a critical point for determining whether or not troubles in the process and product performance occur due to shaving of the film surface in a processing step such as a printing step or a calendering step.

(6) Crystal Form of Calcium Carbonate Particles are separated from the polyester in the same manner as in the method of measuring properties (3), and the crystal structure of the particles after vacuum drying is measured by a usual X-ray diffraction method.

(7) Thickness orientation index of film Using a Abbe refractometer with sodium D line (wavelength 589 nm) as a light source, the refractive index in the thickness direction of the non-oriented film (A) and the thickness of the biaxially oriented film The refractive index in the direction (referred to as B) was measured, and A / B was defined as a thickness orientation index. Use methylene iodide as the mounting solution, 25 ° C, 65
It was measured at% RH.

(8) High-speed dubbing property A magnetic paint is applied to the film using a gravure roll. The magnetic paint was prepared as follows.

・ 100 parts of γ-Fe ₂ O ₃ Average particle size Length: 0.3 μm Needle ratio: 12/1 Coercive force 650 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 The above composition was mixed and dispersed by a ball mill for 48 hours. Thereafter, the kneaded material obtained by adding 6 parts of a curing agent was filtered through a filter to prepare a magnetic coating solution, coated on the film, oriented in a magnetic field, dried at 110 ° C., and further reduced in a small test calender device ( Steel roll / polyester amide roll,
After performing a calendering process at a temperature of 75 ° C. and a linear pressure of 220 kg / cm, the resultant was cured at 70 ° C. for 48 hours to obtain an oxide-coated magnetic recording medium.

100% by TV test waveform generator using home VTR
The chroma signal was recorded, and the chroma S / N was measured from the reproduced signal with a color video noise measuring instrument, which was designated as A. Also, the tape chromatogram after dubbing the tape pancake on which the same signal was recorded was dubbed to the unrecorded tape pancake of the same type at a high speed of 250 m / min using a magnetic field transfer type video software high-speed printing system. The value of / N was measured in the same manner as described above, and was designated as B. When the decrease in chroma S / N (AB) due to this dubbing is less than 4.0 dB, the dubbing resistance is good,
When it was more than dB, it was judged that the anti-dubbing property was poor.

[Examples] Next, embodiments of the present invention will be described based on examples.

Example 1 (Table 1) Elliptical calcium carbonate particles were uniformly dispersed in ethylene glycol by a media dispersion method using glass beads, and polymerized with dimethyl terephthalate to obtain polyethylene terephthalate pellets. When the content of the particles with respect to the polyester was measured, the content of calcium carbonate was 1.0% by weight.

25 parts by weight of a master pellet containing ellipsoidal calcium carbonate particles, 75 parts by weight of polyethylene terephthalate pellets containing substantially no particles are mixed.
After drying under reduced pressure (3 Torr) at 180 ° C. for 3 hours, it is supplied to an extruder,
High-precision filtration (5μ cut filter), melt extrusion at 290 ° C, winding around a casting drum with a surface temperature of 30 ° C using the electrostatic application casting method, cooling and solidifying, thickness of about 180
A μm unstretched film was made.

This unstretched film was stretched 4.2 times in the longitudinal direction at 90 ° C. This uniaxial film was stretched 3.6 times in the width direction at 100 ° C. using a stenter, and heat-treated at 205 ° C. for 5 seconds under a constant length to obtain a film having a thickness of 11 μm.

The calcium carbonate contained in the film was 0.25% by weight, and the crystal form of the calcium carbonate was analyzed, and the crystal form was found to have a vaterite structure.

Also, when the particle flatness of calcium carbonate particles in the film, the average particle size, and the relative standard deviation of the particles were measured,
The particle flatness was 2.1, the average particle size was 0.55 μm, and the relative standard deviation was 0.40.

The ratio of the standard deviation σ of the projection height on the surface of the film to the average projection height h * was 0.60, and the thickness orientation index of the film was 1.05.

The surface average roughness of this film was 0.014 μm.

When the high-speed dubbing property of a video tape using this film was measured, the reduction in S / N due to dubbing was as good as 0.6 dB.

 In addition, the high-speed scraping property was 40 μm, which was good.

Thus, by setting the particle flatness, average particle diameter, and content of the particles in the film to a specific range of the thickness orientation index of the film, a high-speed dubbing property and a high-speed scraping property are both good polyester films. It can be seen that

Examples 2 to 9 and Comparative Examples 1 to 9 (Table 1) The type of particles contained, particle flatness, average particle size, content, film forming conditions, etc. were changed, and polyethylene terephthalate was produced in the same manner as in Example 1. A biaxially oriented film was obtained. When the type of the contained particles, the particle flatness, the average particle diameter, the content, and the thickness orientation index were all within the ranges of the present invention, both the high-speed dubbing property and the high-speed scraping property were good. It is also found that setting the relative standard deviation of the particles in the film and the ratio of the standard deviation σ of the projection height to the average projection height h * in a specific range is more desirable for improving the high-speed cutting property. It can also be seen that the calcium carbonate crystal form in the film having a vaterite structure is effective for improving both high-speed dubbing and high-speed scraping.

(Examples 2 to 9) However, when any of the type of the contained particles, the particle flatness, the average particle size, the content, and the film thickness orientation index are out of the range of the present invention, both the high-speed dubbing property and the high-speed scraping property are required. Could not be satisfied.

(Comparative Examples 1 to 9) [Effects of the Invention] In the present invention, the type, shape, average particle size, content, and thickness orientation index of a film contained in a specific range,
It is a polyester film that has good high-speed scraping properties when used as a film or when used as a product, and high-speed dubbing when used as a magnetic tape, and can cope with severer processing steps and usage conditions in various applications. Things.
The use of the film of the present invention is not particularly limited. Useful as a film.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI B29K 67:00 B29L 7:00 C08L 67:00 (56) References JP-A-4-40623 (JP, A) JP-A-4-41534 ( JP, A) JP-A-3-202354 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 CFD C08L 67/02

Claims (3)

(57) [Claims] 1. A film comprising from 0.002% by weight to 10% by weight of elliptical calcium carbonate particles having a particle flatness of more than 1.5 and not more than 10 and an average particle diameter of not less than 0.01 μm and not more than 5 μm in the film. A polyester film, wherein the ratio (σ / h *) of the standard deviation σ of the projection height on the surface to the average projection height h * (σ / h *) is 1.0 or less, and the thickness orientation index is 1.2 or less. 2. The method according to claim 1, wherein the relative standard deviation of the calcium carbonate particles in the film is 0.7 or less.
Polyester film described 3. The polyester film according to claim 1, wherein the crystalline form of calcium carbonate has a vaterite structure.