JPH11228711A - Biaxially-oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film especially having excellent wear resistance, by contg. a specific amt. of aluminum hydroxide particles with a specified particle size. SOLUTION: A biaxially oriented polyester film contains 0.005-3 wt.% of aluminum hydroxide particles having thicknesses of 1-50 nm and lengths of 0.05-10 μm. The aluminum hydroxide particles, depending on the applied use, e.g. in a magnetic recording media use, have pref. thicknesses of 1-50 nm and lengths of 0.05-1 μm, or, in a high grade paper substitute use, have pref. thicknesses of 1-50 nm and lengths of 1-10 μ,. An aluminum hydroxide particle to be used is of an aluminum hydrate, generally called boehmite, but is not limited to this substance. This biaxially-oriented polyester film contg. aluminum hydroxide particles can be used as not only a single layer film, but also a laminated film contg. at least one layer of this film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biaxially oriented polyester film.

[0002]

2. Description of the Related Art As a biaxially oriented polyester film, a biaxially oriented polyester film containing aluminum oxide particles is known (for example, JP-A-62-43).
No. 450). As a biaxially oriented polyester film, a laminated film is known (for example, JP-A-2-77431).

[0003]

However, in the above-mentioned conventional biaxially oriented polyester film, the transportability of the polyester film and the electromagnetic conversion characteristics when used as a magnetic recording medium are improved. There is a problem that the surface of the film is scratched and powder is generated, and furthermore, when a magnetic tape is used, a signal is lost due to the powder. In addition, the uniformity of the film surface protrusion height was determined by defining the relationship between the lamination thickness and the contained particle diameter, and the electromagnetic conversion characteristics of the magnetic recording medium were improved. In addition, there has been a growing demand for characteristics that make particles harder to fall off. An object of the present invention is to solve such problems and to provide a biaxially oriented polyester film having particularly excellent abrasion resistance.

[0004]

According to the present invention, there is provided a biaxially oriented polyester film having a thickness of 1 to 50 n.
m, containing 0.005 to 3% by weight of aluminum hydroxide particles having a length of 0.05 to 10 μm.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester constituting the biaxially oriented polyester film of the present invention is not particularly limited, but polyethylene terephthalate (PET), poly (ethylene-2,6-naphthalenedicarboxylate)
(PEN) is preferred. Note that two or more kinds of polymers may be mixed or a copolymer may be used as long as the object of the present invention is not hindered. In addition, additives such as an antioxidant, a heat stabilizer, and an ultraviolet absorber may be added to the extent that the objects of the present invention are not impaired.

The biaxially oriented polyester film of the present invention needs to contain aluminum hydroxide particles from the viewpoint of abrasion resistance. The aluminum hydroxide particles used in the present invention are aluminum hydrates, which are usually called boehmite, but are not limited thereto. The particles may contain impurities as long as the object of the present invention is not impaired. The content of the particles is 0.005 to 3% by weight, preferably 0.01 to 2% by weight, and more preferably 0.05 to 1% by weight from the viewpoint of abrasion resistance. The thickness of the particles is 1 to 50 nm, preferably 3 to 30 nm from the viewpoint of abrasion resistance. The length of the particles is 0.05 to 1
Although 0 μm is preferred, for example, 0.05 to 1 μm is preferably used for magnetic recording media, and 1 to 10 μm is used for substitute for high-grade paper, depending on the purpose of use and application.

The biaxially oriented polyester film containing the aluminum hydroxide particles of the present invention (hereinafter referred to as layer A)
May be a single-layer film, but may be a laminated film having a plurality of layers from the viewpoint of abrasion resistance. The thickness of the A layer is not particularly limited, but is 0.01 to 3.0 μm from the viewpoint of abrasion resistance.
m, preferably 0.05 to 2.0 μm, more preferably 0.1 to 1.5 μm. In the case of a laminated structure, at least one main component of the layer may be PET, and other layers are not particularly limited, but polyester is preferably exemplified. The polyester is not particularly limited.
Alternatively, a polymer containing PEN as a main component is preferable. The lamination method may be a coextrusion method in a molten state or a coating method.

The relationship between the thickness A of the layer A of the biaxially oriented polyester film of the present invention and the average particle size d of the aluminum hydroxide particles contained in the layer A is not particularly limited, but 5d ≦ t ≦ 5.
In the case of 00d, preferably 10d ≦ t ≦ 300d, the wear resistance is particularly good.

The biaxially oriented polyester film (layer A in the case of a laminated film) of the present invention may contain particles other than aluminum hydroxide particles. In that case,
The average particle size is not particularly limited, but is 0.05 to 1.0 μm.
m, preferably 0.1 to 0.8 μm, and the content is not particularly limited, but is 0.05 to 1.0% by weight. Preferred examples of such particles include particles selected from calcium carbonate, alumina, silica, aluminum silicate, calcium phosphate, titanium oxide, organic particles, and the like. A plurality of these particles may be used in combination.

The film layers other than the layer A (hereinafter referred to as the layer B) may contain particles other than aluminum hydroxide particles. Also in this case, the average particle size is 0.05 to
It is preferable that the content is 1.0 μm and the content is 0.05 to 1.0% by weight. Preferred examples of such particles include particles selected from calcium carbonate, alumina, silica, aluminum silicate, calcium phosphate, titanium oxide, organic particles and the like.

The use of the biaxially oriented polyester film of the present invention is not particularly limited, such as for magnetic recording media, packaging, and cards such as prepaid cards. In particular, it can be preferably used as a biaxially oriented polyester film for digital video tapes requiring high output. Further, the biaxially oriented polyester film of the present invention can be preferably used for data storage such as for computers.

Next, a preferred method for producing the biaxially oriented polyester film of the present invention will be described and described, but the present invention is not limited thereto.

First, as a method for incorporating particles into PET constituting the film, it is preferable to disperse the particles in the form of a slurry in ethylene glycol, which is a diol component, and to polymerize the ethylene glycol with a predetermined dicarboxylic acid component. It is also effective to mix and knead a water slurry of particles with predetermined PET pellets using a vented twin-screw extruder.

As a method of adjusting the content of particles, there is a method in which a high-concentration master is prepared by the above-described method, and the master is diluted with a polymer substantially free of particles during film formation to adjust the content of particles. It is valid.

Next, the pellets containing a predetermined amount of particles are dried as required, and then supplied to a known melt extruder.
It is extruded in a sheet form from a slit-shaped die, and cooled and solidified on a castin roll to form an unstretched film. If necessary, a plurality of extruders, a plurality of manifolds or a merging block are used to laminate the polyester in a molten state.

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. First, using the sequential biaxial stretching method of stretching in the longitudinal direction and then in the width direction,
The longitudinal stretching is divided into three or more stages, and the longitudinal stretching temperature is 80
It is preferably exemplified that the stretching is carried out at a temperature of from 150 to 150 ° C., a total longitudinal stretching ratio of 3.0 to 6.0, and a longitudinal stretching speed of 5,000 to 50,000% / min. As the stretching method in the width direction, a method using a tenter is preferable, and the stretching temperature is 80 to 150 ° C., and the stretching ratio in the width direction is 4.0 to 7.0 times larger than the longitudinal magnification in some cases.
The stretching is preferably performed at a stretching speed in the width direction of 1,000 to 20,000% / min. Further, if necessary, re-longitudinal stretching and re-lateral stretching are performed. As the stretching conditions in this case, the stretching in the longitudinal direction is preferably 90 to 180 ° C, the stretching ratio is 1.1 to 2.0 times, and the stretching method in the width direction is preferably a method using a tenter, and the stretching temperature is 90 to 180 ° C. The stretching ratio in the width direction is 1.1.
It is preferably carried out at 2.0.

Next, the biaxially oriented film is heat-treated.
The heat treatment temperature in this case is 170 to 220 ° C., especially 170
The time at -210 ° C is preferably in the range of 0.5-60 seconds.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Average particle size, thickness and length of particles The cross section of the film was measured using a transmission electron microscope (TEM).
Observe at a magnification of 10,000 times or more. TEM section thickness is about 10
It was set to 0 nm, and the measurement was carried out for 100 or more visual fields at different locations.

In each field of view, the average particle diameter is calculated from the volume equivalent average diameter, the thickness is calculated from the number average for any 10 points, and the length is calculated from the number average for the longest one branched at any 10 points. Calculated.

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

(3) Film Lamination Thickness The depth distribution of the particle concentration is measured by a secondary ion mass spectrometer, X-ray photoelectron spectroscopy, infrared spectroscopy, or a confocal microscope. After obtaining a maximum value in the depth direction with respect to the surface, a depth that is の of the maximum value was defined as a lamination thickness. In addition, it can be determined not only from the depth distribution of the particle concentration but also from observation of the cross section of the film or a thin film level difference measuring instrument.

(4) Abrasion resistance A film obtained by slitting a film to a width of 1/2 inch was guided with a guide pin (surface roughness Ra10) using a tape running tester.
0 nm) (running speed 300 m / min, running frequency 1 time, winding angle 60 °, running tension 60 g). At this time, the scratches in the film were observed with a microscope, and the number of scratches having a width of 2.5 μm or more per tape width was less than 3;

[0024]

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

Examples 1 and 2 An ethylene glycol slurry of aluminum hydroxide particles was prepared, and a transesterification reaction and a polycondensation reaction were performed from dimethyl terephthalate and ethylene glycol to synthesize PET, thereby obtaining PET particle pellets.

The particle pellets and PET polymer pellets containing substantially no particles are mixed, dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then polymer A: polymer containing 0.3% by weight of aluminum hydroxide particles, polymer B: 0.8μ
A polymer containing 0.05% by weight of m-diameter calcium carbonate particles was supplied to the extruder 1 and the extruder 2, respectively.
Melted at 280 ° C. After filtering these polymers, two layers were laminated at the rectangular junction (A / B).

This was wound around a casting drum having a surface temperature of 25 ° C. by an electrostatic application casting method and cooled and solidified to form an unstretched film. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the A layer.

This unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 95 ° C. This stretching was performed in three stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 3.6 times in the width direction at 100 ° C. using a tenter. This film was heat-treated at 200 ° C. for 3 seconds under a constant length to obtain a biaxially oriented polyester film having a total thickness of 11 μm and an A layer thickness of 1.0 μm.

The properties of the biaxially oriented polyester film were as shown in Table 1 and the abrasion resistance was good.

Comparative Examples 1 and 2 In the same manner as in Example 1, a biaxially oriented polyester film was obtained in which the type and content of the particles were changed. As shown in Table 1, the biaxially oriented polyester film in the range of the present invention has good abrasion resistance.

[0031]

[Table 1]

[0032]

As described above, the biaxially oriented polyester film of the present invention uses aluminum hydroxide particles of a specific shape, and the thickness and length of the particles are regulated, so that excellent abrasion resistance can be obtained. Also, good characteristics can be obtained for a magnetic recording medium.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 16 B29L 7:00 9:00

Claims (4)

[Claims] Claims: 1. A thickness of 1 to 50 nm and a length of 0.05 to
Aluminum hydroxide particles of 10 μm
A biaxially oriented polyester film characterized by containing 3% by weight. 2. An aluminum hydroxide particle having a thickness of 1 to 50 nm and a length of 0.05 to less than 1 μm,
The biaxially oriented polyester film according to claim 1, which contains 5 to 3% by weight. 3. A thickness of 1 to 50 nm and a length of 1 to 10 μm.
2. The biaxially oriented polyester film according to claim 1, comprising 0.005 to 3% by weight of aluminum hydroxide particles having a particle size of m. 4. A biaxially oriented polyester film, which is a laminated film having at least one film layer according to claim 1.