JPH0639536B2 - Oriented polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester film having excellent abrasion resistance. More specifically, the present invention is excellent in the running characteristics of the film, and further, the generation of scratches and abrasion powder is extremely small,
The present invention relates to an oriented polyester film suitable for metal deposition or magnetic recording media.

[Problems to be Solved by Conventional Techniques and Inventions]

The polyester film has excellent physical and chemical properties and is widely used as an industrial base material. Among them, polyethylene terephthalate film oriented in at least uniaxial direction is particularly excellent in mechanical strength, dimensional qualification, flatness, etc., and is therefore used in various applications such as base films of magnetic recording media and capacitor dielectrics. Has been done.

By the way, when these films are actually handled, runnability and abrasion resistance are required, but this has not been sufficiently achieved in the past.

That is, when the film and the metal pin having high hardness come into contact with each other at a high speed, friction and wear between them are increased, and scratches are generated on the film, and abrasion powder is generated.

As a result of intensive studies on the improvement of the wear resistance, the present inventors have found that the wear resistance can be improved by incorporating particles having a high Mohs hardness, for example, aluminum oxide, into the film.

However, the present inventors have also found that the incorporation of such particles of aluminum oxide may cause new problems. That is, the film containing the particles, while exhibiting an extremely excellent effect, in terms of scratching of the film itself and generation of abrasion powder in contact with the metal pin, the film has a relatively high hardness such as aluminum. When a low-metal is vapor-deposited or superposed and wound in a concentric shape, particles present on the film surface in contact with the metal surface often damage the metal surface. A similar phenomenon is observed when a magnetic layer is provided instead of such a metal layer, and the surface of the magnetic layer is often scratched to deteriorate the electromagnetic characteristics.

[Means for Solving the Problems]

As a result of intensive studies on the improvement of this point, the present inventors have found that if a specific amount of aluminate particles having a characteristic particle size is used, the generation of abrasion powder at the time of contact with these metal pin, metal surface, and magnetic layer. The present inventors have completed the present invention by finding that it is possible to obtain an excellent oriented polyester film that scarcely damages a contacting partner.

That is, the gist of the present invention resides in an oriented polyester film characterized by containing 0.01 to 2% by weight of aluminate particles having an average particle diameter of 0.5 μm or less.

Hereinafter, the present invention will be described in more detail.

The polyester referred to in the present invention means terephthalic acid, 2,6
An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and a polyester obtained by using ethylene glycol as a main starting material, but may contain other third component. In this case, examples of the dicarboxylic acid component include isophthalic acid, phthalic acid, 2,
6-naphthalenedicarboxylic acid, terephthalic acid, adipic acid, sebacic acid, and oxycarboxylic acid components such as p
-One or more of oxyethoxybenzoic acid and the like can be used. As the glycol component, one kind or two or more kinds of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used. In any case, the polyester of the present invention refers to a polyester in which 80% or more of repeating structural units have ethylene terephthalate units or ethylene 2,6-naphthalene units.

Further, the polyester film of the present invention refers to a polyester film which is made of such polyester as a starting material and is oriented at least uniaxially, and a known method can be used as a production method thereof. For example, usually 270-320
A method of melt-extruding into a sheet form at 40 ° C., cooling and solidifying at 40 to 80 ° C. to obtain an amorphous sheet, then biaxially stretching in the longitudinal and transverse directions successively or simultaneously and then heat treating at 160 to 250 ° C. (for example, The method described in JP-B-30-5639) can be used. In the case of stretching in the machine direction and the transverse direction, each may be stretched in one stage, or may be stretched in multiple stages or a heat treatment section for relaxing orientation may be provided between the multi-stage stretches, if necessary. Further, after biaxial stretching, it may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching can be carried out in any of the longitudinal and lateral directions, or in both directions.

A feature of the present invention is that aluminate particles having an average particle diameter of 0.5 μm or less are used as main particles to be mixed with polyester.

As is well known, an aluminate is a salt formed from aluminum oxide and a metal oxide having a stronger basicity than aluminum oxide, and is divided into an alkali metal salt and a divalent metal salt. Of these, divalent metal salts are preferred in the present invention,
Among these, zinc aluminate or magnesium aluminate is more preferable, and zinc aluminate is particularly preferable.

A polyester film containing aluminate particles hardly generates abrasion powder when it comes into contact with a metal pin or a guide roll, and when it is wound up on a metal vapor deposition layer, for example, it does not scratch them and It can be suitably used throughout the process. The reason why such excellent wear properties are exhibited in the case of the aluminate is not clear, but it is considered that the good fit of the particles to polyester and the appropriate hardness are the main reasons.

The aluminate can be obtained, for example, by igniting a metal oxide or a carbonate with aluminum oxide, but in the present invention, the aluminate particles to be incorporated in the film may contain some impurities. . For example, zinc aluminate often contains zinc oxide due to its production method, but if the amount of these impurities is less than 30% by weight, preferably less than 10% by weight, the desired effect can be sufficiently enjoyed. .

Further, in the present invention, the particle size distribution of the aluminate particles is not particularly limited, but it is sharper, specifically, the weight fractions of 75% and 25% when integrated from the smaller particle size. The particle size ratio of 2.0 or less, preferably
Those of 1.5 or less are preferably used.

The specific surface area is not particularly limited, either.
It can be suitably used up to about 0 m ² / g.

In the present invention, even if the surface of the aluminate particles is treated with various surface treatment agents such as silane coupling agent and titanium coupling agent, the effect is sufficiently exhibited.

The average particle size of the aluminate is 0.5 μm or less, especially 0.1
μm or less is preferable. If this value exceeds 0.5 μm, the surface roughness of the film, especially the maximum protrusion, becomes too large, and the base material that comes into contact with the film is easily scratched.

In the present invention, it is preferable to use such aluminate particles as completely dispersed up to the primary particles, but as long as it does not adversely affect the surface condition of the film, it may behave even as slightly aggregated secondary particles. Absent. However, also in this case, an apparent average particle size of 0.5 μm or less is preferably used.

The lower limit of the average particle size is about 5 mμ.

The blending amount of aluminate particles with respect to polyester is 0.
It is selected from the range of 01 to 2% by weight. If this amount is less than 0.01% by weight, the effects of scratch resistance and abrasion resistance will be insufficient, while if it exceeds 2% by weight, they will often be damaged when they come into contact with the metal vapor deposition layer or the magnetic layer. The preferred range is 0.2 to 0.7% by weight.

These aluminate particles are blended with polyester through operations such as pulverization, classification and filtration, if necessary. For the pulverization treatment, for example, a rod mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a pan mill, a roller mill, an impact mill, an agitation grinding mill, a fluid energy mill or the like can be used. Further, for the classification treatment, for example, a semi-free vortex type, a forced vortex type, a hydrocyclone type, a centrifugal separation method and the like can be adopted.

As a method of blending the particles with the polyester, a method of adding the particles as an ethylene glycol slurry to a reaction system in the initial stage of polyester production is usually adopted.
Of course, a method of directly blending with the polyester before film formation may be used.

Thus, in the present invention, it becomes possible to obtain a film having an abrasion property which has hitherto been unachievable by blending a specific particle diameter and a specific amount of aluminate with a polyester film. However, with such aluminate particles alone, the slipperiness of the film may be insufficient and the handling workability may be inferior. By using other particles in combination, the workability can be improved.

So-called precipitated particles can be mentioned as one of such particles. The deposited particles are those in which the metal compound is deposited as fine particles in the polyester manufacturing process,
For example, an alkali metal or an alkali metal compound is present before or after the transesterification reaction or the esterification reaction, and precipitated as inactive fine particles having an average particle size of about 0.1 to 5 μm in the presence or absence of a phosphorus compound. In this case, the runnability can be particularly improved by allowing the particles to exist in an amount of 0.01 to 1% by weight based on the polyester film.

Another example is so-called additive particles. The additive particles refer to particles externally added to the polyester manufacturing process, and specifically, kaolin, talc, carbon, molybdenum sulfide, gypsum, rock salt, calcium carbonate, barium sulfate, lithium fluoride, calcium fluoride, zeolite. , Calcium phosphate, silicon dioxide,
Titanium dioxide etc. can be mentioned. In this case, the average particle size of these added particles is larger than that of the aluminate, and it is preferable to select from the range of 0.1 to 3 μm and the compounding amount with respect to the polyester from the range of 0.05 to 2% by weight.

As an example of such added particles, heat-resistant polymer fine powder can be cited. As a typical example in this case, a monovinyl compound having only one aliphatic unsaturated bond in the molecule, as described in JP-B-59-5216, and a divinyl compound in the molecule as a cross-linking agent. Examples thereof include copolymers with a compound having one or more aliphatic unsaturated bonds, but are not limited thereto, and examples thereof include thermosetting phenol resin, thermosetting epoxy resin, and thermosetting. It is also possible to use a fine powder of a fluororesin such as a basic urea resin, a benzoguanamine resin, or polytetrafluoroethylene. In this case, the average particle size of these heat-resistant polymer fine powders is selected from the range of 0.05 to 5 μm, and the compounding amount thereof with respect to the polyester film is selected from the range of 0.01 to 3% by weight.

As described above, in the present invention, in addition to the specific aluminate particles, other particles are optionally used in combination, but when the polyester film obtained has certain physical properties, the running property of the film is Can be improved to a higher degree, improved mechanical strength and improved slitting property can be achieved, for example, it becomes more suitable as a base film for magnetic recording media. The refractive index in the thickness direction is 1.492 or more. If this value is less than 1.492, slipperiness and abrasion resistance will often be insufficient even if the particles of the present invention are used. This value is preferably in the range 1.494 to 1.505. In order to obtain a film having such physical properties, for example, in the case of biaxial stretching at the time of longitudinal-transverse, the longitudinal stretching temperature is set to be 5 times higher than the normal stretching temperature.
It may be set to about 105 to 115 ° C., which is higher by about 30 ° C. Alternatively, such a film can be obtained by subjecting the film to a substantial lateral relaxation after the biaxial stretching and before the heat treatment.

Further, as one of preferred embodiments of the polyester film containing a specific aluminate of the present invention, a biaxially oriented film having a film thickness of 12.0 μm or less, which is strongly oriented in the longitudinal direction, can be mentioned. That is, the film of the present invention can be suitably used particularly as a base film for magnetic recording media by taking advantage of its high abrasion resistance, but its features are particularly exerted when it is used for high strength and thin high recording density. be able to. Specifically, the F-5 value in the longitudinal direction is 12.0 kg / mm ³ or more, preferably 14.0 kg / mm ³ or more, and the film thickness is 12.0 μm or less, especially 10.0 μm or less, and particularly wear resistance is required. It is effective in various applications.

Furthermore, in the present invention, the difference Δn (n _TD −n _MD ) between the refractive index n _{TD in} the width direction and the refractive index n _{MD in the} longitudinal direction is 0.010.
In the above case, the slit property is particularly excellent, and the film is suitable as a base film for magnetic recording media. The slitting property is a characteristic when a tape coated with a magnetic layer is slit by a shear cutter or the like, and when the degree is low, the cut end is curled up in a streak shape, and a whisker or powder is generated from the cut end. When such a phenomenon occurs, the tape and the white powder adhere to each other, deteriorating the electromagnetic conversion characteristics and inducing dropout. By setting Δn to be 0.010 or more, preferably 0.020 or more, more preferably 0.025 or more, this slitting property can be effectively improved. If this Δn is too large, inconvenience may occur in terms of heat shrinkage, etc., so this Δn is preferably set to 0.060 or less.

In addition, in order to obtain a film having such physical properties, for example, an amorphous unstretched polyester film is stretched 3 to 4 times in the machine direction at about 90 ° C. and then stretched in the width direction at 90 to 150 ° C.
A method of simply stretching 3.5 to 6 times (usually higher than the longitudinal direction), and then heat treating at 170 to 230 ° C. is simply adopted.

In the present invention, it is needless to say that the basic technical idea of using aluminate particles may be combined with a plurality of these preferable characteristics.

The film of the present invention can be particularly effective when used as a base film for a video tape and also as an audio film. In other words, in the field, there are two types of conventional radio boomboxes, compo stereos, etc.
As a result of the widespread use of models equipped with a double or more high-speed dubbing function, the tape and the base material come into contact with each other at a higher speed during the dubbing process, fast-forwarding, and rewinding. The effect of is effectively exhibited.

When the film of the present invention is used as a substrate for metal vapor deposition, the effect is maximized when the metal has a Mohs hardness of 2 to 3 such as aluminum, zinc, copper or silver.
The laminate obtained by subjecting the film of the present invention to metal vapor deposition is used, for example, for gold and silver threads, for decoration, for foil, for labels, for packaging, for capacitors, for electroluminescence, for printed boards and the like.

Another advantage of using the aluminate particles specified in the present invention is that the specific resistance of the polyester containing the particles when melted can be extremely reduced.

The specific resistance at the time of melting is, for example, JP-B-61-43173.
As described in the publication, when a so-called electrostatic applied cooling method is used in the method for producing a polyester film, it has a good correlation with the film forming rate, and the lower the value, the more preferable.

It is not clear why the low resistivity is exhibited in the case where the aluminate is blended, but it is considered that the solubility in the polyester is larger than that in other particles and the ionization is facilitated when a voltage is applied.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. In the examples and comparative examples, "parts" means "parts by weight".

The measuring method used in the present invention is as follows.

(1) Average particle size The particle size is measured with a microscope and the volume fraction of the equivalent sphere is 50.
% Particle diameter (diameter) was taken as the average particle diameter.

(2) Runnability The slip property of the film was evaluated. The slidability was measured using the apparatus shown in FIG. That is, the film is wound around a fixed hard chrome-plated metal roll (diameter 6 mm) and the angle is 135 °.
That is, contact at 2.356 rad (θ), 53 g (T ₂ )
This was run at a speed of 1 m / mm over one end, the resistance force (T ₁ , g) at the other end was measured, and the friction coefficient (μd) during running was determined by the following formula.

(3) Abrasion property (A) Abrasion property with metal pin The film was brought into contact with and scraped with a metal pin to measure the degree of scratches generated on the film surface.

That is, the film is wrapped around a hard chrome-plated metal pin (diameter 6 mm, surface roughness 3S), the angle is 135 °, and the tension is 50.
They were contacted with each other at g and rubbed at a running speed of 4 m / sec.

Then, aluminum was vapor-deposited on the film surface, and the degree of scratches was visually determined, and the wear characteristics with the metal pin were classified into the following 5 ranks.

Rank 1 There are many wounds and often deep scratches.

Rank 2 The amount of scratches is relatively large, and there are deep scratches in some places.

Rank 3 The degree of scratches is relatively small and the number of deep scratches is small.

Rank 4 Some scratches are recognized.

Rank 5 Almost no scratches.

(B) Abrasion property with magnetic tank 200 parts of magnetic fine powder, 30 parts of polyurethane resin, 10 parts of nitrocellulose, vinyl chloride-vinyl acetate copolymer 1
0 parts, 5 parts of lecithin, 100 parts of cyclohexanone, 100 parts of methyl isobutyl ketone and 300 parts of methyl ethyl ketone are mixed and dispersed in a ball mill for 48 hours, and then 5 parts of a polyisocyanate compound is added to obtain a magnetic paint, which is applied to a polyester film. The coating was magnetically oriented before being sufficiently dried and solidified, and then dried to form a magnetic layer having a thickness of 2 μm. Further, this coated film was surface-treated with a super calendar and slit into a 1/2 inch width to obtain a video tape.

The magnetic tape obtained next is 8000 m long and speed 2
It was wound up at 0 m / sec and a tension of 100 g.

Then, the tape was rewound, and the degree of scratches on the magnetic surface was visually evaluated and classified into the following 5 ranks.

Rank 1 There are many wounds and often deep scratches.

Rank 2 The amount of scratches is relatively large, and there are deep scratches in some places.

Rank 3 The degree of scratches is relatively small and the number of deep scratches is small.

Rank 4 Some scratches are observed, but it is a satisfactory level.

Rank 5 Almost no scratches.

(C) Abrasion property with vapor-deposited metal layer 250 ± 10Å on 15μm polyester film surface
A film in which aluminum is vacuum-deposited is slit into a width of 35 mm, and the aluminum-deposited surface is faced up, and the film is attached to a moving table. The test film of the same width is fixed and overlapped on the aluminum vapor-deposited surface, and a load of 1 g / 16 cm ² is applied on the test film, and the moving table is moved to 2
Move at a speed of 0 mm / min and rub the aluminum deposition surface with the test film for 50 to 60 mm.

Using a haze meter NDH-20D manufactured by Nippon Denshoku Co., Ltd., the gold light transmittance before and after the test is measured, and the difference therebetween is determined. The higher this value, the more scratches on the aluminum surface.

(4) Specific resistance when melted British British Journal of Applied Physics (Brit. J. Appl. Phya) Vol. 17, No. 1
The method described in pages 149 to 1154 (1966). However, in this case, the melting temperature of the polymer was 295 ° C., and the value immediately after applying a direct current of 1,000 V was taken as the specific resistance during melting.

Example 1 100 parts of dimethyl terephthalate ethylene glycol 7
0 part and 0.20 part of magnesium acetate tetrahydrate were placed in a reactor to carry out a transesterification reaction. After 4 hours, the transesterification reaction was substantially completed, and the average particle size was 0.02μ.
1.0 part of zinc aluminate of m., 0.06 part of ethyl acid phosphate and 0.04 part of antimony trioxide were further added, and the polymerization reaction was carried out for 5 hours according to a conventional method to obtain an intrinsic viscosity of 0.
63 polyesters were obtained. (Polyester (A)) The specific resistance of polyester (A) when melted is 7.2 × 10 ⁶ Ω-cm.
That was a sufficiently low value.

On the other hand, in the above polyester production, polymerization was carried out in the same manner as above except that 0.40 part of calcium carbonate having an average particle size of 0.8 μm was added in place of zinc aluminate, and the intrinsic viscosity was increased.
0.63 of polyethylene terephthalate was obtained. (Polyester (B)) The specific resistance of polyester (B) when melted is 4.1 x 1
It did not reach the level of 0 ⁷ Ω-cm and relatively low in the polyester (A).

Next, polyester (A) and polyester (B) are mixed at 50:50.
The mixture was mixed in a weight ratio of 1, and after drying, it was extruded into a sheet form at 290 ° C. from an extruder to obtain an amorphous sheet. The specific resistance of the amorphous sheet when melted was 1.0 × 10 ⁷ Ω-cm, which was satisfactory.

Next, the obtained sheet was stretched 3.5 times at 90 ° C. in the longitudinal direction and 4.3 times at 110 ° C. in the transverse direction, and heat-treated at 210 ° C. for 3 seconds to obtain a biaxially stretched film having a thickness of 15 μm.

Next, the obtained film was coated with a magnetic layer or vapor-deposited with aluminum.

The results of these evaluations are shown in Table 1 together with those of other examples and comparative examples.

Example 2 A polyester and a polyester film were obtained and evaluated in the same manner as in Example 1 except that the average particle size of zinc aluminate and the blending amount in polyester were changed.

Example 3 Evaluations were made in the same manner as in Example 1 except that magnesium aluminate was used instead of zinc aluminate and kaolin was used instead of calcium carbonate.

Comparative Example 1 Evaluation was performed in the same manner as in Example 1 except that zinc aluminate was not included in Example 1.

Comparative Examples 2 and 3 A film was obtained in the same manner as in Example 1 except that calcium carbonate (Comparative Example 2) or α-type aluminum oxide (Comparative Example 3) was used in place of zinc aluminate in Example 1, and the characteristics thereof were evaluated. did.

[Effects of the Invention] The film of the present invention has excellent abrasion properties with various materials, and can be suitably used for various applications including base films for metal vapor deposition and magnetic recording media, and its industrial use. The target value is high.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a running system for evaluating the running property of a film. In the figure, (I) is a stainless steel fixing pin having a diameter of 6 mm, (II) and (III) are tension meters, and θ is 135 °.

Claims (1)

[Claims] 1. An oriented polyester film comprising 0.01 to 2% by weight of aluminate particles having an average particle diameter of 0.5 μm or less.