JPH0577318A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To provide a biaxially oriented polyester film wherein damages on the surface of the film during high speed process occur seldom and damages on the magnetic face occur seldom when used as a magnetic tape. CONSTITUTION:A biaxially oriented polyester film wherein 0.01-3wt.% particle A consisting of an oxide of an element of the fifth or the sixth period in the periodical table of elements with a mean primary particle diameter of at least 0.0017mum and at most 0.3mum and a mean degree of aggregate of 2-100 are incorporated and at the same time, 0.01-2.0wt.% inert particle B with a mean primary particle diameter of at least 0.3mum and at most 2.0 P are incorporated and the heat shrinkage in the longer direction of the film is at most 2.0% and the number of projections on one face of the film is 1,000/mm<2> or larger and the mean carvature radius of the projections is 0.3-3.0mum.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Biaxially oriented polyester film containing fine agglomerated particles (Japanese Patent Laid-Open No. 3-1154)
37).

[0003]

In the case of the above-mentioned conventional biaxially oriented polyester film, a roll and a guide pin which come into contact with each other in the magnetic layer application in the magnetic medium application, the calendering step, or the dubbing step in manufacturing the soft tape. Although it is possible to suppress the scratches that occur when the film surface is rubbed, etc., because the particles contained are hard,
When the tape is used as a magnetic tape when the magnetic surface of the tape comes into contact with the base film surface and rubs against it during the winding process of the magnetic tape manufacturing process or the aging process under heating after winding. We were unable to solve the problem of poor image quality and sound quality.

The present invention suppresses the generation of scratches on the film surface (hereinafter referred to as scratch resistance) and the generation of scratches on the magnetic surface (hereinafter referred to as magnetic surface scratches), which have conventionally had contradictory properties. At the same time, another object of the present invention is to provide an improved biaxially oriented polyester film.

[0005]

In order to achieve the above object, the present invention has an average primary particle size in the film of 0.00
0.01 to 3% by weight of particles A made of oxides of elements of the 5th and 6th periods of the periodic table of the periodic table of elements having an average cohesion of 2 to 100 μm and not more than 0.3 μm, and further having an average primary particle diameter. Is a biaxially oriented polyester film containing 0.01 to 2.0% by weight of inert particles B having a particle size of more than 0.3 μm and not more than 2.0 μm at the same time, wherein the number of protrusions on one side of the film is 1000 pieces / mm ^2. As described above, the biaxially oriented polyester film is characterized in that the average radius of curvature of the protrusion is 0.3 to 3.0 μm and the thermal shrinkage in the longitudinal direction of the film is 2.0% or less.

The polyester of the present invention is not particularly limited, but is usually polyethylene terephthalate, polyethylene α,
β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylate, polyethylene 2,6-naphthalate, polybutylene terephthalate and the like are used. Of these, polyethylene terephthalate is preferred. Further, in the case of polyester containing ethylene terephthalate as a main constituent, scratch resistance is further improved, which is particularly desirable. Two or more polyesters may be mixed or a copolymerized polymer may be contained within a range not impeding the present invention.

The particles A used in the film of the present invention must be composed of oxides of elements of the 5th and 6th periods of the periodic table of the elements.
In the case of particles other than oxides of elements of the 5th and 6th periods of the periodic table of the elements, scratch resistance cannot be satisfied.

The particles A in the present invention include zirconium oxide, cerium oxide, tungsten oxide, molybdenum oxide, tin oxide and the like. Of these, zirconium oxide, cerium oxide, tungsten oxide, and molybdenum oxide are particularly effective in improving scratch resistance.

The content of the particles A used in the film of the present invention in the film is 0.01 to 3% by weight, preferably 0.03.
Must be ~ 2% by weight. If the content of the inert particles A is less than the above range, scratch resistance becomes poor, and if the content is too large, magnetic surface scratches become poor, which is not preferable.

The average primary particle diameter of the particles A in the present invention is 0.001 μm or more and 0.3 μm or less, preferably 0.0
It should be not less than 03 μm and not more than 0.2 μm. Particle A
If the average primary particle size of is outside the above range, the effect of the present invention cannot be obtained.

The average degree of coagulation of the particles A in the film of the present invention is 2 to 100, preferably 3 to 80 in order to improve the scratch resistance. The particle A is obtained by uniformly aggregating fine primary particles, and the effect of the present invention can be obtained by using the agglomerated particles.

Inert particles B used together with the above particles in the present invention include silica, calcium carbonate, cross-linked polydivinylbenzene, etc. These inert particles B are those of the 5th and 6th periods of the periodic table of the elements. It need not be an oxide composed of elements. The average primary particle size of the particles B in the film is more than 0.3 μm and 2.0 μm or less,
Preferably it is more than 0.3 μm and 1.5 μm or less, the content is 0.01 to 2.0% by weight, preferably 0.03 to
It should be 2.0% by weight, more preferably more than 0.5% by weight and 2.0% by weight or less. When the average primary particle diameter of the particles B and the content of the particles B deviate from the above ranges, both scratch resistance and suppression of scratches on the magnetic surface cannot be achieved. The particles B are preferably monodisperse. When the particles B are agglomerated, the particles B themselves are likely to drop off from the film surface, and the dropped particles are likely to cause scratches on the film surface.

Inert particles other than the above, internal precipitated particles, additives and the like may be used in combination as long as the effects of the present invention are not impaired.

The number of protrusions on one side of the film of the present invention is 100.
It should be 0 pieces / mm ² or more. When the number of protrusions on one surface of the film is less than 1000 / mm ² , the slip resistance is insufficient and the scratch resistance becomes poor.

The average radius of curvature of protrusions on the film surface of the film of the present invention must be 0.3 to 3.0 μm. If the average of the radius of curvature of the protrusion is not within the above range, the scratch resistance becomes poor.

Further, the heat shrinkage of the film of the present invention in the longitudinal direction of the film must be 2.0% or less, preferably 1.8% or less. If the heat shrinkage ratio in the longitudinal direction of the film is larger than the above range, the tightness of the winding of the tape during aging in the magnetic tape manufacturing process will cause the magnetic surface and the base film surface to be rubbed and scratched on the magnetic surface, degrading the product performance. I will let you.

The height of the average protrusion on one surface of the film of the present invention is not particularly limited, but is more preferably 0.05 to 0.3 μm in order to obtain the effects of the present invention.

Further, forming a composite film of two or more layers in which the film of the present invention is laminated on at least one side is an effective means for obtaining the effects of the present invention.

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

First, as a method of incorporating inert particles into a predetermined polyester, it may be added before, during, or after the polymerization, such as ethylene glycol which is a diol component of the polyester. A method of mixing, dispersing and adding in the form of a slurry is used. 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.

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

Next, after the polyester is sufficiently dried, it is fed to a known melt extruder, passed through a filtration filter, and melt-extruded from a slit-shaped die at 260 to 320 ° C.,
An unstretched film is prepared by cooling and solidifying.

In the case of forming a composite film having two or more layers, a method of obtaining a composite film by using two or more extruders, two or more layers of manifolds, and a merging block at the time of melt extrusion is effective in obtaining the effect of the present invention. Is.

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 at 70 to 120 ° C. in 2 or 3 stages and 4 to 5 times stretched.

The stretching in the width direction is performed at 80 to 120 ° C. for 3 to 5
Double stretching is preferable.

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

If necessary, this stretched film can be heat-treated. In this case, the heat treatment condition is preferably 0.5 to 30 seconds under a constant length in the range of 150 to 230 ° C.

Further, after the biaxial stretching and heat treatment, the film is relaxed in the longitudinal direction by a method utilizing the peripheral speed difference between two or more rolls heated to a temperature equal to or lower than the heat treatment temperature within the scope of the present invention. It is a very effective means for obtaining the heat shrinkage ratio of.

[0030]

[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) Average Primary Particle Size of Particle A B. E. The specific surface area of the particles is determined by the T method, and the particle diameter when the particles are spheres is determined from the specific surface area by the following formula,
This was defined as the average primary particle size. Particle size = 6 / (particle density × specific surface area) (particle size: μm, particle density: g / cm ³ , specific surface area: m ²
/ G) If it is difficult to determine the primary particle size by the above method,
Observe the particles from the cross section of the film with an electron microscope,
The primary particle size can also be determined. The term "primary particle size" as used herein means a particle size obtained from each of the primary particles even when the particles are in an agglomerated state.

(2) Average Coagulation Degree of Particle A A film containing particles is made into an ultrathin section having a thickness of 1000 angstroms perpendicular to the plane of the film, and a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.) is used.
Particles were observed at a magnification of about 100,000 by using, and the equivalent circle diameter of the particles was determined, and the value averaged in 20 fields of view was taken as the secondary particle diameter of the particles. The ratio (secondary particle size / primary particle size) between this secondary particle size and the primary particle size obtained by the method (1) was defined as the average degree of aggregation. The cohesion degree indicates how many primary particles the secondary particles, which are aggregates, consist of. If necessary, XMA or the like is used to distinguish the particles B or other particles from each other to obtain the average diameter.

(3) Average Primary Particle Size of Particle B The particles are observed by a transmission electron microscope in the same manner as in the method of (2), the equivalent circle diameter of the particles is determined, and the average value of 20 visual fields is averaged for the particles B. The primary particle size was used. The particles B are monodisperse particles, and the particle diameter obtained by this method is the primary particle diameter.

(4) Particle content It was measured by a usual fluorescent X-ray analysis method. Further, if necessary, quantification is carried out by utilizing pyrolysis gas chromatography, infrared absorption, Raman scattering, SEM-XMA, or the like.

(5) Scratch resistance The film is slit into a tape having a width of 1/2 inch, and a tape running tester TBT-300H type (manufactured by Yokohama System Laboratory Co., Ltd.) is used at 20 ° C. and 60 ° C. In a% RH atmosphere, a guide pin of a video cassette at a tension of 30 g and a traveling speed of 250 m / min (surface roughness Ra: 50 nm, Rt: 2
A guide pin made of stainless steel having a surface of about 500 nm was run at a winding angle of 60 degrees, and the amount of scratches at a point 90 m from the beginning of the run was visually determined according to the following criteria. No scratch at all ... 5 points Shallow scratch ... 3 points Many deep scratches ... 1 point Also, 4 points and 3 points between 5 points and 3 points Between 1 and 1 was 2 points. This measurement was performed 10 times, and the average was taken as the score of scratch resistance, and the score of 3 or more was taken as good scratch resistance.

(6) Average protrusion height on film surface, number of protrusions 2 Detector type scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and cross-section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the flat portion of the film surface was measured as 0, and the measured height of the protrusion was measured by an image analyzer [IBAS2000, Carl Zeiss Co., Ltd.].
Manufactured] to reconstruct the film surface protrusion image. Next, the projection portion is binarized in this surface projection image, the highest value among the individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 50 times by changing the place. The number of protrusions was determined by regarding the protrusions having a height of 0.03 μm or more measured here as protrusions. The magnification of the scanning electron microscope is usually 3000 times, and the optimum magnification can be selected in the range of 2000 to 5000 times according to the size of the protrusion.

(7) Radius of curvature of protrusion tip The radius of curvature of the protrusion tip was determined according to the following definition for each of the protrusions having a diameter of 0.03 μm or more measured by the same method as the measurement of the above (6). In the cross-sectional curve (y = f (x)) of the protrusion passing through the apex of the protrusion on the image analysis device, the value of the protrusion height corresponding to the portion of 9 pixels in total including the apex of the protrusion as the center is calculated as Interpolated by the least squares method to the function represented by
Curvature radius βT in the film width direction perpendicular to MD and βMD
D was calculated. Next, the radius of curvature β of the projection tip was calculated from this value by the following formula. Thus, the radius of curvature β of the projection tip of each projection was obtained, repeated 50 times at different locations in the same manner as in the measurement of (5), and averaged. y = ax ² + bx + c ... βMD, TD = 1 / | y ″ | ... β = 2βMD · βTD / (βMD + βTD)

(8) Heat Shrinkage About 10 mm wide and 250 mm long were cut out from the sample film, and about 2
Insert two marked lines at an interval of 00 mm and measure the interval accurately (this is A mm. This sample is 100 under no tension)
After leaving it in a hot air oven at a temperature of 30 ° C. for 30 minutes, the distance between the marked lines was measured (this was B mm), and 100 × (A−B) / A was taken as the heat shrinkage ratio.

(9) Magnetic surface scratch A commercially available video tape and a sample film slit to a width of 1/2 inch are applied with a tension of 100 g, and the magnetic surface of the tape and the measurement surface of the sample film are in contact with each other. Co-roll as described above, and leave to stand in a hot air oven at 100 ° C. for 12 hours. After that, the magnetic surface of the video tape was observed with a microscope in the width direction. When there was almost no scratch, the magnetic scratch was good, and when there were 20 or more scratches, the magnetic scratch was defective.

[0040]

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

Example 1 (Table 1) Fine zirconium oxide was uniformly dispersed in ethylene glycol by a media dispersion method using glass beads and polymerized with dimethyl terephthalate to obtain polyethylene terephthalate. Of pellets were obtained. The content of particles with respect to polyester was 1.0% by weight. Similarly, when polyethylene terephthalate pellets containing calcium carbonate particles were obtained, the particle content was 1.0% by weight.

30 parts by weight of zirconium oxide particle-containing master pellets, 25 parts by weight of calcium carbonate particle-containing master pellets and 45 parts by weight of substantially particle-free polyethylene terephthalate pellets were mixed, and the pellets were mixed at 180 ° C. for 3 days. Time reduced pressure drying (3 Torr)
After that, it is supplied to the extruder, filtered with high precision (5μ cut filter) at a filtration pressure of 120 kg / mm ² , melt-extruded at 290 ° C., and wound around a casting drum with a surface temperature of 30 ° C. using an electrostatically applied casting method. Cooled and solidified, thickness about 18
An unstretched film of 0 μm was made.

The unstretched film was stretched 4.0 times in the longitudinal direction at 90 ° C. This uniaxial film was stretched 3.8 times in the width direction at 100 ° C. using a stenter, and was stretched at a constant length of 21
After heat treatment at 0 ° C. for 5 seconds, the film was relaxed in the longitudinal direction by two rolls heated to 200 ° C. having different peripheral speeds to obtain a film having a thickness of 12 μm.

The content of particles in this film was 0.30% by weight of zirconium oxide and 0.25 of calcium carbonate.
% By weight.

The zirconium oxide particles in the film had an average primary particle size of 0.03 μm, an average degree of aggregation of 20, and calcium carbonate had an average primary particle size of 0.6 μm.

Next, the average radius of curvature of the surface protrusions of this film and the number of protrusions were determined.
m, 3,800 pieces / mm ² .

The heat shrinkage in the longitudinal direction was 0.4%.

The scratch resistance of this film was 5 points, and the number of scratches on the magnetic surface was 5, which were all good levels.

As described above, by setting the particles in the film, the characteristic values relating to the protrusions on the film surface, and the thermal shrinkage in the longitudinal direction of the film within the specific ranges, the scratch resistance is excellent and the scratches on the magnetic surface are not generated. It can be seen that there can be few films.

Examples 2 to 8 and Comparative Examples 1 to 8 (Tables 1 to 4) Example 1 was changed by changing the average primary particle size, average cohesion degree, content, film forming conditions, etc. of the two types of particles contained. In the same manner as described above, a biaxially oriented film of polyethylene terephthalate was used. When each property was within the range of the present invention, both scratch resistance and magnetic scratches were good. (Examples 2 to 8) However, if even one of the characteristics is outside the scope of the present invention,
It was not possible to satisfy both the scratch resistance and the magnetic surface scratch (Comparative Examples 1 to 8).

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

The present invention has two types of particles,
Average primary particle diameter, average degree of cohesion, the amount of addition and the heat shrinkage ratio in the longitudinal direction of the film when a biaxially oriented polyester film and the curvature radius of the projections on the film surface, the number of projections within a specific range, during film processing, or The product is a biaxially oriented polyester film that has good scratch resistance when used as a product, and has less scratches on the magnetic surface when used as a magnetic tape. It is possible.

The use of the film of the present invention is not particularly limited, but scratches due to abrasion of the surface become a problem in product performance during processing and use as a product, and scratches on a magnetic surface when the product is manufactured affect product performance. It is particularly useful as a base film for magnetic recording media to be determined.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08L 67/00 // B29K 67:00 105: 02 105: 16 B29L 9:00 4F

Claims (4)

[Claims] 1. The average primary particle size in the film is 0.00.
0.01 to 3% by weight of particles A made of oxides of elements of the 5th and 6th periods of the periodic table of the periodic table of elements having an average cohesion of 2 to 100 μm and not more than 0.3 μm, and further having an average primary particle diameter. Is a biaxially oriented polyester film containing 0.01 to 2.0% by weight of inert particles B having a particle size of more than 0.3 μm and not more than 2.0 μm at the same time, wherein the number of protrusions on one side of the film is 1000 pieces / mm ^2. As described above, the biaxially oriented polyester film having an average radius of curvature of protrusions of 0.3 to 3.0 μm and a thermal shrinkage ratio of 2.0% or less in the longitudinal direction of the film. 2. A biaxially oriented polyester film obtained by laminating the biaxially oriented polyester film according to claim 1 on at least one surface. 3. The particle A is composed of one kind selected from zirconium oxide, cerium oxide, tungsten oxide and molybdenum oxide, or a mixture of two or more kinds selected from these. The biaxially oriented polyester film according to item 2. 4. The biaxially oriented polyester film according to claim 1, wherein the content of the inert particles B is more than 0.5% by weight and 2.0% by weight or less.