JP2616048B2 - Biaxially oriented polyester film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film. More specifically, the present invention relates to a base film for a magnetic tape and a biaxially oriented polyester film suitable for use in a condenser, packaging, and the like.

[Prior art] As a biaxially oriented polyester film, a film containing inert inorganic particles in polyester (for example,
JP-A-63-72729) is known.

[Problems to be Solved by the Invention] In recent years, the speed of a film processing step has been increased, the speed of a dubbing system for magnetic media has been increased, and the speed of assembling a magnetic tape cassette has been increased. In the above-mentioned conventional biaxially oriented polyester film, when it is used in a high-speed process, when it comes into contact with a roll, a pin or the like during the process, there is a problem that the surface of the film is scratched and the performance of the product is deteriorated.

An object of the present invention is to solve such a problem and to provide a biaxially oriented polyester film having excellent film surface scratch resistance (scratch resistance) during high-speed running.

Means for Solving the Problems In order to achieve the above object, the present invention provides an oxide of an element of the fifth and sixth periods of the Periodic Table of the Elements having an average primary particle size in a film of 1 nm or more and less than 300 nm. Of particles A consisting of 0.08-3
The biaxially oriented polyester film is characterized by containing 0.01% to 0.5% by weight of inert particles B having an average primary particle size of 300 to 2000 nm.

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 particles A used in the film of the present invention are the fifth in the periodic table of the element,
The particles must be made of an oxide of the element of the sixth period. In the case of particles other than oxides of the elements of the fifth and sixth periods of the periodic table, the scratch resistance cannot be satisfied.

Examples of the particles A made of an oxide of an element of the fifth and sixth periods of the periodic table of the present invention include cerium oxide, zirconium oxide, and tin oxide.

The average primary particle size of the particles A in the film is 1n
It is necessary that the thickness be not less than m and less than 300 nm, preferably not less than 5 nm and less than 100 nm. If the average primary particle size is smaller or larger than the above range, the scratch resistance becomes poor, which is not preferable.

The content of the particles A composed of oxides of the elements of the fifth and sixth periods of the periodic table of elements used in the film of the present invention is 0.
It should be from 08 to 3% by weight, preferably from 0.08 to 2% by weight. Even when the content of the particles A is less than the above range,
Even if the amount is large, the scratch resistance becomes poor, which is not preferable.

The average agglomeration degree in the film of the particles A composed of the oxides of the elements of the fifth and sixth periods of the periodic table of the element of the present invention is 5 to 5.
A value of 100 is preferable for improving scratch resistance.

In the present invention, it is necessary to use the inert particles B at the same time as the particles A. The inert particles B do not need to be oxides composed of elements of the fifth and sixth periods of the periodic table, but are preferably silica, calcium carbonate, a crosslinked styrene-divinylbenzene copolymer, or the like. The average primary particle size of the inert particles B in the film is 300 to 200.
0 nm and the content of 0.01 to 0.5% by weight are necessary for improving the scratch resistance. If the average primary particle size is smaller than the above range or larger, the scratch resistance becomes poor. Also, when the content of the inert particles B is less than or in the above range, the scratch resistance becomes poor.

In addition, inert particles other than those described above and internally precipitated particles may be used in combination as long as the effects of the present invention are not impaired.

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, the scratch resistance becomes good, which is desirable.

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

First, as a method for incorporating the particles A and the inert particles B into a predetermined polyester, any of the following methods may be added before, during, or after the polymerization. The method of mixing, dispersing and adding in the form of 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 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 the polyester, it is supplied to a known melt extruder, and after passing through a filtration filter, 260-320 ° C.
Melt extruded from a slit die and cooled and solidified to produce an unstretched film.

Also, the draft ratio at the time of casting (the slit width of the base /
It is effective that the thickness of the unstretched film) is about 5 to 30 to obtain 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 120 ° C. in two or three steps, and a method of stretching 4 to 5 times is used.

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.

[Action] The film of the present invention limits the type of particles A contained therein,
It is presumed that by setting the particle size and the amount of addition of the particles A and B in the specific ranges, the characteristics of the particles were maximized and the effects of the present invention were obtained.

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

(1) Average primary particle size, average agglomeration degree The film containing the particles is made into an ultra-thin section with a thickness of 1000 mm perpendicular to the film plane, and using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.) The particle size of the particles was observed at about 100,000 times, and the value averaged over 100 visual fields was defined as the average primary particle size.

In addition, the number of primary particles each of which was observed in the same manner as one aggregated particle was counted, and a value averaged over 100 visual fields was defined as an average aggregation degree.

(2) Particle content The particle content was measured by a usual fluorescent X-ray analysis method.

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

(3) Scratch resistance The film is slit into a 1/2 inch wide tape, and a tape running tester TBT-300H type (manufactured by Yokohama System Research Institute Co., Ltd.) is used at 20 ° C and 60% RH atmosphere. At 60
g, run on a video cassette guide pin (stainless steel guide pin with a surface roughness of about 50 nm for Ra and 2500 nm for Rt) at a running angle of 60 degrees at a running speed of 250 m / min.
The amount of damage at a point 90 m from the beginning of the run was visually determined according to the following criteria.

No scratches at all 5 points Shallow scratches 3 points Many deep scratches 1 point 4 points between 5 and 3 points 4 points 3 points And two points between the two points. This measurement was performed 10 times, and the average was set as the scratch resistance score, and 3 or more points were set as the good scratch resistance.

(4) Surface roughness The surface roughness was measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the average value of 20 measurements was taken as the surface roughness.

・ Tip tip radius: 0.5 μm ・ Touch load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm [Example] Next, an embodiment of the present invention will be described based on an example.

Example 1 (Table 1) Fine cerium oxide 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. The content of the particles with respect to the 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.

45 parts by weight of cerium oxide particle-containing master pellets, 20 parts by weight of calcium carbonate particles-containing master pellets, and 35 parts by weight of polyethylene terephthalate pellets substantially containing no particles are mixed, and the pellets are dried under reduced pressure at 180 ° C. for 3 hours. (3 Torr), then feed into the extruder and filter pressure 120
High precision filtration (5μ cut filter) at 290 ° C with kg / cm ²
Extrusion at a surface temperature of 30
The film was wound around a casting drum at a temperature of 200 ° C. and solidified by cooling to form an unstretched film having a thickness of about 180 μm. At this time, the ratio (draft ratio) of the die slit gap to the thickness of the unstretched film was 10.

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 210 ° C. for 5 seconds under a constant length to obtain a film having a thickness of 12 μm.

The particle content of this film was 0.45% for cerium oxide.
% By weight and 0.20% by weight of calcium carbonate.

The average primary particle size of the cerium oxide particles in the film was 20 nm, the average degree of aggregation was 35, and the average primary particle size of the calcium carbonate was 1050 nm.

The average surface roughness of this film was 0.0124 μm.

Next, when the scratch resistance of this film was measured, it was 5 points and was very good.

Thus, it can be seen that a film having excellent scratch resistance can be obtained by setting the average primary particle size and the content of the particles in the film to specific ranges.

Examples 2 to 6, Comparative Examples 1 to 5 (Table 1) Biaxial orientation of polyethylene terephthalate in the same manner as in Example 1 except that the kind of the particles contained, the average primary particle size, the content, and the film forming conditions were changed. Film. When the average primary particle diameter and the content of the contained particles were within the ranges of the present invention, the scratch resistance was good. It is also found that setting the average degree of agglomeration of the particles to a specific range is more desirable for improving scratch resistance. (Examples 2 to 6).

However, when either the average primary particle size or the content of the contained particles was outside the scope of the present invention, the scratch resistance could not be satisfied (Comparative Examples 1 to 5).

[Effects of the Invention] The present invention provides a biaxially oriented polyester film having a good scratch resistance at the time of film processing or at the time of use as a product, with the average primary particle size of the contained particles and the amount added being in a specific range. It can cope with severer processing steps and usage in various applications. The use of the film of the present invention is not particularly limited, but it is useful as a base film for a magnetic recording medium in which scratches due to surface abrasion during processing and use as a product cause problems in product performance.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 7:00 (56) References JP-A-62-212132 (JP, A) JP-A-60- 58431 (JP, A) JP-A-64-90254 (JP, A) JP-A-62-207356 (JP, A)

Claims (2)

(57) [Claims] An average primary particle size in a film is 1 nm or more and 300 or more.
Particles A composed of oxides of elements of the fifth and sixth periods of the periodic table having a particle diameter of less than nm are contained in an amount of 0.08 to 3% by weight, and 0.01 to 0.5% by weight of inert particles B having an average primary particle diameter of 300 to 2000 nm. %
A biaxially oriented polyester film characterized by containing. 2. An average degree of aggregation of particles A in a film is 5 to 5.
The biaxially oriented polyester film according to claim 1, wherein the number is 100.