JPH07108663A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PURPOSE:To obtain excellent high speed cutting properties and electromagnetic conversion characteristics by adding non-spherical particles with a particle size ratio of a specific value or more to one uppermost layer of a biaxially oriented laminated polyester film having a two-layered laminated structure. CONSTITUTION:A polyester film has at least a two-layered laminated structure and at least one uppermost layer thereof can satisfy both of high speed cutting properties and electromagnetic conversion characteristics by this laminated structure. At least one layer of the respective layers constituting the polyester film is necessarily oriented biaxially. Further, flat silica particles of which the particle size ratio being the ratio of the average value of the long diameters of particles and that of the short diameters thereof is 1.4 or more and an average particle size is 0.05-3.0mum are added to at least one upper most layer of the polyester film. In order to form desired surface projections efficiently and effectively, the relation between the average particle size (d) of non-spherical particles and the thickness (t) of the particle-containing uppermost layer is set to 0.2d<=t<=10d.

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 film which is hard to be scraped off and which is capable of forming surface projections optimal as a base material for video tapes.

[0002]

2. Description of the Related Art Biaxially oriented polyester film, for example, a biaxially oriented polyester film which can be used as a base material for video tapes, is a film in which polyester contains substantially spherical silica particles derived from colloidal silica. Are known (for example, JP-A-5
9-171623).

[0003]

However, as the process speed of film processing, especially the magnetic layer coating / calendering / winding process for magnetic media applications, the process of assembling a cassette, etc., is increased, the film surface is contacted by rolls or guides. ,
In particular, there is a drawback that the film surface having minute irregularities is easily scraped off. Further, the conventional one has a drawback that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality is deteriorated during dubbing as the dubbing speed is increased by high-speed magnetic field transfer.

The present invention solves the above problems, the film surface is hard to be scraped off in a high speed process (hereinafter referred to as excellent in high speed sharpness), and there is little deterioration in image quality at the time of dubbing when used as a magnetic medium. It is an object of the present invention to provide a biaxially oriented laminated polyester film which is optimum as a base material for a video tape having good electromagnetic conversion characteristics (hereinafter referred to as excellent electromagnetic conversion characteristics).

[0005]

The biaxially oriented laminated polyester film of the present invention which meets this object is a biaxially oriented laminated polyester film having at least a two-layer laminated structure, and at least one outermost layer (A) is provided. , Containing non-spherical particles having a particle size ratio of 1.4 or more.

First, the polyester film of the present invention needs to have a laminated structure of at least two layers. As long as it has two or more layers, it may have three layers, four layers, or a laminated structure of more layers. With the laminated structure, it is possible to satisfy at least one of the outermost surface layer (A) of the surface with both high-speed sharpness and electromagnetic conversion characteristics.

Next, the polyester film of the present invention is
It is necessary that at least one layer of each of the above-mentioned layers is biaxially oriented. It is particularly preferable that all layers in a laminated structure of two or more layers are biaxially oriented. When all layers are non-oriented or uniaxially oriented, the characteristics of the present invention cannot be satisfied.

The polyester constituting the present invention is not particularly limited, but ethylene terephthalate, ethylene α, β
It is particularly preferable when at least one structural unit selected from -bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent component. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Two or more kinds of polyesters may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

The polyester film of the present invention contains non-spherical particles having a particle size ratio of 1.4 or more in at least one outermost layer (A). As will be described later, the non-spherical particles have a flat particle shape with a particle size ratio of 1.4 or more, which is the ratio of the average value of the major axis to the average value of the minor axis. Since such flat particles have a higher resistance when falling off than spherical particles, they are less likely to drop off the film surface. Therefore, the flat particles themselves, and further the film surface projections formed by the particles,
The abrasion resistance, especially the high-speed abrasion resistance is improved. In particular, when the flattened direction of the flat shape of the particles is the film orientation direction, that is, when the flattened particles are in the film orientation direction, a film surface that is hard to drop off and is not easily scraped off is formed.

The type of the non-spherical particles is not particularly limited, but silica particles or the like whose particle diameter ratio is relatively easy to control are suitable. The average particle size of the non-spherical particles is also not particularly limited, but is preferably in the range of 0.05 to 3.0 μm so that the non-spherical particles may be contained in the outermost surface layer (A) to effectively serve for forming surface protrusions.

Further, although the target projections are formed on the film surface due to the inclusion of the non-spherical particles, the non-spherical particles are concentrated in the outermost surface layer (A) so that the desired surface projections can be produced efficiently and effectively. In order to form, the relationship between the average particle diameter d of the non-spherical particles and the thickness t of the particle-containing layer (A) is 0.2
It is preferable that d ≦ t ≦ 10d.

As described above, the polyester film of the present invention contains non-spherical particles in at least one outermost layer (A), but this layer (A) contains other particles. Good. By including appropriate other particles in combination, it is possible to further improve high-speed sharpness and electromagnetic conversion characteristics. In addition, the background of the film surface can be made stronger.

The combined particles contained in the layer (A) include:
For example, the primary particle size is 5 to 200 nm, preferably 10
Agglomerated particles A selected from α-type alumina, γ-type alumina, δ-type alumina, θ-type alumina, zirconia, silica, and titanium particles having a size of ˜100 nm are preferable, and the content is 0.05 to 2% by weight, preferably 0.1-1% by weight
Is preferred.

Further, as other combination particles contained in the layer (A), calcium carbonate having an average particle size of 0.05 to 3.0 μm, preferably 0.1 to 2 μm, more preferably 0.2 to 1 μm. Particles, monodisperse silica particles, particles selected from divinylbenzene particles, silicone particles are preferred,
The content is 0.05 to 10% by weight, preferably,
0.1 to 5% by weight is preferable.

By including the above particles in the layer (A) together with the non-spherical particles, as described above, the high-speed sharpness and electromagnetic conversion characteristics are higher than those of the non-spherical particles alone.
It is possible to further improve.

In the film of the present invention, high-speed sharpness,
The layer (A) is not particularly limited in terms of electromagnetic conversion characteristics.
Has a thickness of 0.1 to 5 μm, preferably 0.2 to 4 μm.

In the film of the present invention, the surface roughness parameter P10 of the projections on the surface of the layer (A) formed mainly of the non-spherical particles is preferably 350 nm or less, more preferably 300 nm or less. .
If it is larger than this value, the high-speed scraping property is deteriorated and the electromagnetic conversion characteristics may be deteriorated.

Regarding the height of the protrusions on the surface of the layer (A), the relative standard deviation of the protrusion height distribution is preferably 1.2 or less, more preferably 1.0 or less. If it is larger than this value, undesired coarse protrusions are present, and that portion is easily scraped off, the high-speed sharpness is deteriorated, and the electromagnetic conversion characteristics are also likely to be deteriorated.

In the film of the present invention, other polymers may be blended within the range not impairing the object of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. The organic additive may be added to the extent that it is usually added.

Further, the polymer IV of the layer (A) of the laminated polyester film of the present invention is particularly preferably in the range of 0.4 to 0.9 because the high speed abrasion property is further improved. Further, when the difference between the polymer IV and the adjacent layer is within 0.1, the high-speed sharpness is further improved, which is very preferable.

Next, a method for producing the film of the present invention will be described. First, as a method of incorporating non-spherical particles into polyester, for example, a method of dispersing in a slurry form in ethylene glycol, which is a diol component, and polymerizing the ethylene glycol with a predetermined dicarboxylic acid component is preferable. When adding non-spherical particles, for example, if the water sol or alcohol sol obtained at the time of synthesis is added without drying once, the dispersibility of the particles is very good, and both high-speed sharpness and electromagnetic conversion characteristics are good. Can be Further, a method in which an aqueous slurry of non-spherical particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into polyester is also very effective for further improving the effect of the present invention. is there. As a method for adjusting the content of particles, there is a method of preparing a high-concentration particle master by the above method, and diluting it with a polyester that does not substantially contain particles during film formation to adjust the content of particles. It is valid.

Next, the polyester pellets are used to form a polyester film having a laminated structure of two or more layers. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll. At the very least make an unstretched film. That is, two or more extruders, two or more layers of manifolds or a merging block (for example, a merging block having a square merging portion) are used for lamination, and two or more layers of sheets are extruded from a die and cast on a casting roll. Cool to make unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Also, the melting temperature of the extruder for extruding the polymer on the side of the internal particle-containing layer is 5-10
It is effective to lower the temperature by ° C.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, and stretching in the longitudinal direction is performed in three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated, but the first stage is usually 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 6.0 times is appropriate. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows. (1) Average particle size of particles The polymer is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM) and the particle image is processed with an image analyzer. The magnification of the SEM is approximately 2000 to 10,000 times, and the visual field in one measurement is appropriately selected from approximately 10 to 50 μm on each side. The volume average diameter d is obtained from the particle diameter and its volume fraction when the number of particles is 5,000 or more by changing the observation location. d = Σdi · Nvi Here, di is the particle size, and Nvi is the volume fraction thereof. When the particles are significantly damaged by the plasma low temperature ashing method, the following method may be used. The cross section of the film is 3000 to 100 by using a transmission electron microscope (TEM).
Observe at 000 times. The section thickness of the TEM is set to about 1000 Å, the location is changed and 500 or more visual fields are measured, and the volume average diameter d is calculated from the above formula.

(2) Content of Particles A solvent in which the polyester is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is taken as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Particle size ratio In the measurement of (1) above, the average value of the major axis of each particle /
It is the ratio of the average value of the minor axis. That is, it is calculated by the following formula. Major axis = ΣD1 _i / N long diameter short diameter _{= ΣD2 i / N D1 i,} D2 i each individual particle (maximum diameter), short diameter (the shortest diameter), N is the total number.

(4) Film Laminate Thickness While etching from the surface, the depth profile of the particle concentration is measured by XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy), confocal microscope or the like. In the surface layer of the film laminated on one side, the particle concentration is low due to the interface called the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film laminated on one side of the present invention, the particle concentration once reaching the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [II] at which the maximum particle concentration is halved (here,
The layer thickness was II> I). Furthermore, when inorganic particles are contained, a secondary ion mass spectrometer (S
Using IMS), the concentration ratio (M ⁺ / C ⁺ ) of the element causing the highest concentration of particles in the film and the carbon element of polyester is defined as the particle concentration, and the depth from the surface of the polyester A layer is determined. Analyze in the (thickness) direction. Then, the laminated thickness is obtained from the same method as described above. Alternatively, it can be obtained by observing the film cross section or a thin film step measuring machine.

(5) Standard deviation of height distribution of surface protrusions Two-detector scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and cross-section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the projection when the flat surface of the film surface is set to 0, and the measured height of the protrusion is measured by an image processing apparatus [IBAS2000, Carl Zeiss Co., Ltd.].
Manufactured] to reconstruct the film surface projection image on the image processing device. Next, the equivalent circle diameter is calculated from the area of each protrusion obtained by binarizing the protrusion portion in this surface protrusion image, and this is made the average diameter of the protrusion. In addition, the highest value among the binarized individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 500 times at different places, and the height distribution of the measured protrusion was regarded as a normal distribution (normal distribution centered on a point with height 0) and approximated by the least squares method to calculate the height distribution. The standard deviation was calculated. The magnification of the scanning electron microscope is 1000
Select between ~ 8000 times.

(6) Surface roughness parameter P10 Optical interference type three-dimensional surface analyzer (TOPO- manufactured by WYKO)
3D, objective lens: 40 to 200 times, effective use of high resolution camera) is used to construct a film surface protrusion image on the image processing apparatus. In this surface protrusion image, the average of 10 points from the highest value of the protrusion portion was defined as P10. Two
The value was defined as the average value of 0 measurements (unit: nm).

(7) Polymer IV It was measured at 25 ° C. using o-chlorophenol as a solvent.

(8) High-speed shaving property A film is slit into a tape having a width of 1/2 inch, a single-edged blade is pressed at an angle of 90 °, and the film is pushed 0.5 mm to run for 200 m (speed: 200 m / min, tension: 100 g). The adhering height of the powder scraped off on one edge was read with a microscope, and the scraped amount (μm) was taken. If the abrasion amount is 180 μm or less, the abrasion resistance is good, and if it exceeds it, the abrasion resistance is poor.

(9) Electromagnetic conversion characteristics A magnetic coating composition having the following composition is applied to the film by a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
(5 stages), temperature: 70 ° C., linear pressure: 200 kg / cm, and then calendaring is performed at 70 ° C. for 48 hours. The above tape raw material was slit to 1/2 inch to prepare a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to obtain a VTR cassette tape. (Composition of magnetic paint) -Co-containing iron oxide: 100 parts by weight-Vinyl chloride / vinyl acetate copolymer: 10 parts by weight-Polyurethane elastomer: 10 parts by weight-Polyisocyanate: 5 parts by weight-Lecithin: 1 part by weight-Methyl ethyl ketone : 75 parts by weight Methyl isoptyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon black: 2 parts by weight Lauric acid: 1.5 parts by weight Using a VTR for home use on this tape, a TV test waveform generator was used. A 100% chroma signal was recorded, and the chroma S / N was measured from the reproduced signal with a color video noise measuring instrument.

[0033]

EXAMPLES Next, the embodiments of the present invention will be explained based on examples. Example 1 (Table 1) Non-spherical silica particles having an average particle size of 0.5 μm and a particle size ratio of 1.5, and an average primary diameter of 0.04 μm as a combined particle and an average secondary diameter (diameter in an aggregated state) 0 50 parts by weight of pellets containing 3 μm zirconia particles, and 5 parts of polyethylene terephthalate pellets containing no particles.
When mixed in an amount of 0 part by weight, the content of non-spherical silica particles is 0.
The mixture was prepared so as to have a concentration of 5% by weight and supplied to a vent type twin-screw kneading extruder 1 and melted at 280 ° C. (Polymer I). Furthermore,
Another extruder 2 was prepared, and pellets containing substantially no particles were dried under reduced pressure at 180 ° C. for 3 hours (3 Torr).
It was then fed to the extruder 2 and melted at 290 ° C. (Polymer I
I). After filtering these two polymers with high precision respectively, in a three-layer merging block equipped with a rectangular laminated portion, polymer II is placed in the base layer portion (B) and polymer I is placed in both surface layer portions (A). / B / A laminated in 3 layers, extruded into a sheet from a fish tail type die, and then wound around a casting drum with a surface temperature of 30 ° C by the electrostatic applied casting method to be cooled and solidified to obtain a thickness. An unstretched film of about 160 μm was made. The draft ratio at this time was 6.5.

This unstretched film is divided into three stages in the longitudinal direction, 1.2 times at 123 ° C., 1.45 times at 126 ° C., 1
Each was stretched 2.3 times at 14 ° C. This uniaxial film was divided into two steps in the width direction using a stenter, and stretched 3.7 times at 111 ° C. and 1.2 times at 113 ° C. to 200 at a fixed length.
The film was heat treated at 5 ° C. for 5 seconds to obtain a film having a thickness of 14 μm. The laminated thickness ratio of the biaxially stretched film is A layer / B layer / A
The layer was 1/12/1 (μm). The surface roughness parameter P10 was 150, and the relative standard deviation of the height distribution of protrusions was 0.8.

As a result of measuring the electromagnetic conversion characteristics and the high-speed abrasion resistance of this film, both were good. As described above, when the constitution of the present invention in which at least one layer (A) contains non-spherical particles, a film having both good electromagnetic conversion characteristics and high-speed abrasion resistance can be obtained.

Examples 2 to 3 and Comparative Examples 1 to 3 (Table 1) In the same manner as in Example 1, biaxially oriented polyester films were prepared. In Examples 2 and 3, in addition to the non-spherical silica particles, the combined particles shown in Table 1 were added to the layer (A). In Example 3, no combined particles were contained,
Moreover, a two-layer laminated structure of A / B was adopted. As shown in Table 1, when the presence or absence of non-spherical particles was contained, that is, when the particle diameter ratio of the contained particles was not within the range of the present invention, it was not possible to obtain a film excellent in both electromagnetic conversion characteristics and high-speed abrasion resistance. .

[0037]

[Table 1]

[0038]

According to the biaxially oriented laminated polyester film of the present invention, it has a laminated structure of two or more layers, and at least one outermost layer (A) contains non-spherical particles having a specific particle size ratio or more. Since the particles can form uniform and hard-to-cut protrusions on the surface of the layer (A) to form a desired surface roughness, it is possible to achieve excellent abrasion resistance at high speed and also to provide a magnetic medium for magnetic media. It is possible to exhibit excellent electromagnetic conversion characteristics.

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Claims (7)

[Claims] 1. A biaxially oriented laminated polyester film having at least a two-layer laminated structure, wherein at least one outermost layer (A) contains non-spherical particles having a particle size ratio of 1.4 or more. A biaxially oriented laminated polyester film. 2. The biaxially oriented laminated polyester film according to claim 1, wherein the non-spherical particles are silica particles. 3. The average particle diameter of the non-spherical particles is 0.05 to
The biaxially oriented laminated polyester film according to claim 1 or 2, which is in the range of 3.0 μm. 4. The biaxial according to claim 1, wherein the relationship between the average particle diameter d of the non-spherical particles and the thickness t of the layer (A) is 0.2d ≦ t ≦ 10d. Oriented laminated polyester film. 5. The layer (A), in addition to the non-spherical particles, α-type alumina, γ-type alumina, δ-type alumina, θ-type alumina particles, zirconia particles, silica particles, titanium particles, calcium carbonate particles, The biaxially oriented laminated polyester film according to any one of claims 1 to 4, which contains 0.05 to 10% by weight of particles selected from divinylbenzene particles and silicone particles. 6. A surface roughness parameter P1 of the layer (A).
The biaxially oriented laminated polyester film according to any one of claims 1 to 5, wherein 0 is 350 nm or less. 7. The biaxially oriented laminated polyester film according to claim 1, wherein the relative standard deviation of the protrusion height distribution on the surface of the layer (A) is 1.2 or less.