JPH06157782A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a polyester film excellent in chipping resistance and scratch resistance and useful as a base film for magnetic recording media. CONSTITUTION:This polyester film contains 0.05-2.0wt.% plate-like boron nitride fine particles having 3-20 aspect ratio and 0.05-3mum average particle diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film, and more particularly to a polyester film which is excellent in abrasion resistance and scratch resistance and is particularly useful as a base film for magnetic recording media.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films are used for various purposes, especially for magnetic recording media because of their excellent physical and chemical properties.

In the biaxially oriented polyester film, its slipperiness and abrasion resistance are major factors that affect the workability in the film manufacturing process and the film manufacturing process, and the product quality. If these are insufficient, for example, when a magnetic layer is applied to the surface of a biaxially oriented polyester film and used as a magnetic tape, friction between the coding roll and the film surface is severe, and shavings are generated, or scratches are generated on the film surface. . Also,
Even when used as a VTR or data cartridge,
Shavings and scratches are generated in the process of winding the cassette at high speed, causing dropout.

Particularly in VTR applications, recently, for the purpose of cost reduction, a metal guide or a plastic guide having an insufficient surface finish may be used for a guide post fixed in a cassette, and the surface of the guide post is extremely rough.

For this reason, conventional techniques for improving the slipperiness and the scraping property of the film, for example, a method of adding inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate, talc, clay and calcined kaolin (for example, Japanese Patent Laid-Open Publication No. 54-575
No. 62) or a method of precipitating fine particles containing calcium, lithium or phosphorus in the polymerization system (for example, Japanese Examined Patent Publication No.
In a magnetic tape to which No. 32-32914) is applied and which does not have a back coat, shavings and scratches are generated in the process of winding the cassette at a high speed, and the dropout level is increased.

[0006] In order to solve such problems, a method of reducing scratches by adding porous alumina, silica and titania particles having a large porosity (for example, JP-A-62-43450).
No.), a method of adding fine particles having a high Mohs hardness to reduce scratches (JP-A-1-306220, JP-A-2-30620).
No. 185533) has been proposed, for example, when the treatment is performed at a higher speed with silica, the effect is reduced, while with alumina, the effect of scratch resistance is sufficient.
Since the hardness is high, the plastic guide may be damaged and shavings may be generated. In particular, those having a lump shape with a small aspect ratio have a remarkable problem.

[0007]

In view of the above situation, the present inventor has good abrasion resistance and scratch resistance even for a metal guide or a plastic guide having a rough surface.
The present invention has been achieved as a result of intensive research to produce a polyester film which is particularly useful for magnetic recording media.

[0008]

That is, according to the present invention, plate-like boron nitride fine particles having an aspect ratio (plate diameter / plate thickness) in the range of 3 to 20 and an average particle size in the range of 0.05 to 3 μm. Of 0.05 to 2.0% by weight.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film-forming properties, especially melt-forming film-forming properties.

Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenylketone dicarboxylic acid and anthracene dicarboxylic acid.

Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol and cyclohexanedimethanol. Examples thereof include alicyclic diols and the like.

In the present invention, as the polyester,
Those containing alkylene terephthalate and / or alkylene naphthalate as a main constituent are preferably used.

Among such polyesters, especially polyethylene terephthalate, polyethylene-2,6-naphthalate, etc., for example, 8 of all dicarboxylic acid components are used.
A copolymer in which 0 mol% or more is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid and 80 mol% or more of all glycol components is ethylene glycol is preferable. In that case, 20 mol% or less of the total acid component may be the above-mentioned aromatic dicarboxylic acid other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid. It may be an acid, an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid, or the like. Further, 20 mol% or less of the total glycol component may be the above-mentioned glycol other than ethylene glycol, and, for example, hydroquinone,
Resorcin, 2,2-bis (4-hydroxyphenyl)
Aromatic diols such as propane, aliphatic diols having an aromatic ring such as 1,4-dihydroxydimethylbenzene, polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. You can also

The polyester of the present invention includes
Aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid is copolymerized or bonded at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component.

Further, in the polyester of the present invention, the polycarboxylic acid or polyhydroxy compound having 3 or more functional groups, such as trimellitate, is contained in a substantially linear range, for example, in an amount of 2 mol% or less based on the total acid components. A copolymer of acid, pentaerythritol and the like is also included.

The above polyester is known per se and can be produced by a method known per se.

The above polyester is preferably one having an intrinsic viscosity of about 0.4 to about 0.9 measured at 35 ° C. as a solution in o-chlorophenol.

The plate-like boron nitride fine particles added to the polyester in the present invention can be synthesized by, for example, a metal nitriding method (boric acid, borate etc. are reacted with a nitrogen-containing organic substance, ammonia, nitrogen etc.) and the like. it can.

However, the plate-like boron nitride fine particles used in the present invention may be synthesized by a method other than the above-mentioned method and is not particularly limited by the synthesis method and the like.

Impurities (for example, residues at the time of synthesis) may be contained as long as the object of the present invention is not impaired.

The plate-like boron nitride fine particles in the present invention are
The aspect ratio of the particles needs to be in the range of 3 to 20, preferably 8 to 15. Further, the average particle size of the fine particles is in the range of 0.05 to 3 μm, preferably 0.1.
Is about 1.0 μm.

When the aspect ratio is less than 3, the powder shape becomes close to a lump, and the projections on the film surface due to the particles are sharpened, and the scratching property is good, but shavings are easily generated. On the other hand, when the aspect ratio is larger than 20, the plate-like structure of the particles becomes strong, so that the dispersibility in the polymer becomes poor, the film surface becomes rough and shavings are easily generated. However, particles having a shape other than the above-described aspect ratio (for example, cubic boron nitride) may be mixed as long as the object of the present invention is not impaired.

The average particle size of the fine particles is 0.05 μm.
If it is less than the above, the fine particles become too fine, and it becomes impossible to form fine projections required for scratch resistance and abrasion powder resistance. On the other hand, if it is more than 3 μm, the surface becomes rough and abrasion powder is easily generated. .

The amount of the tabular boron nitride fine particles added to the polyester is 0.05 to 2.0% by weight. If the addition amount is less than 0.05% by weight, the effect of adding the fine particles becomes small and the scratch resistance is not effective.
If it exceeds, the dispersion of particles becomes poor and shavings are likely to occur.

In the present invention, other inert particles may be used in combination with the plate-like boron nitride fine particles as long as the object of the present invention is not impaired.

The type of the inert particles is not particularly limited, and examples thereof include inorganic inert particles such as calcium carbonate, silicon dioxide, titanium oxide, barium sulfate, kaolin and zeolite, organic resins such as silicone resin and crosslinked polystyrene. Examples thereof include inert particles and particles internally deposited by a polyester polymerization catalyst.

The polyester film of the present invention has an intrinsic viscosity of 0.35 to 0.9 dl obtained by extruding polyester at a temperature of, for example, a melting point (Tm: ° C.) to (Tm + 70) ° C.
/ G of unstretched film is obtained, and the unstretched film is uniaxially (longitudinal or transverse) in the direction of (Tg-10) to (Tg + 7).
At a temperature of 0) ° C. (however, Tg: glass transition temperature of polyester), the film is stretched at a draw ratio of 2.5 to 5.0, and then in the direction perpendicular to the stretching direction (when the first stage stretching is the longitudinal direction,
The second stage drawing is in the transverse direction) and Tg (° C)-(Tg + 7
It can be produced by stretching at a temperature of 0) ° C. at a draw ratio of 2.5 to 5.0 times. In this case, the area draw ratio is 9
It is preferably ˜22 times, more preferably 12 to 22 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching.

Further, the obtained film has (Tg + 70)
It can be heat-set at a temperature of ℃ to Tm (℃). For example, for polyethylene terephthalate film,
It is preferable to heat-set at 190 to 230 ° C. The heat setting time is, for example, 1 to 60 seconds.

The reason why the polyester film of the present invention is excellent in scratch resistance and abrasion resistance is not clear, but probably the addition of boron nitride fine particles having a high Mohs hardness improves scratch resistance and further the aspect ratio of the particle shape. By making it 3 to 20 plate-shaped, the projection shape on the film surface may become a trapezoidal gradual shape, and the affinity (adhesiveness) to the polyester film is improved as compared with the lump-shaped particles, and the shavings are It is speculated that this is due to the decrease.

The polyester film of the present invention has excellent abrasion resistance and scratch resistance, and is particularly useful as a base film for magnetic recording media.

[0031]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, each characteristic value in an Example is based on the following method.

(1) Average particle size of particles 1) In the case of granules Shimadzu Corporation's centrifugal sedimentation type particle sizer (SACP-4)
L type: CENTRIFUGAL PARTICLE S
IZE ANALYZER). The particle diameter corresponding to 50 mass% is read from the integrated curve of particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is taken as the above-mentioned average particle diameter (Book “Particle size measurement Technology ", published by Nikkan Kogyo Shimbun, 1975, pp. 242-247).

2) Particles in film A small piece of sample film is fixed on a sample stand for a scanning electron microscope (S-570 type) manufactured by Hitachi, Ltd., and a sputtering device (JFC) manufactured by JEOL Ltd. -1100 type ion etching apparatus) is used to perform ion etching treatment on the film surface by the following method. The sample is set in a bell jar, the degree of vacuum is raised to a vacuum state of about 100 ⁻³ Torr, and ion etching is performed for about 10 minutes at a voltage of 0.25 kV and a current of 12.5 mA. Furthermore, gold spatter was applied to the film surface with the same device, and 1 with a scanning electron microscope.
Observed at 10,000 to 50,000 times and at least 100 with Luzex 500 manufactured by Nippon Regulator Co., Ltd.
The equivalent spherical diameter distribution of each particle is obtained and calculated from the weight cumulative 50%.

(2) Aspect Ratio of Particles (Plate Diameter of Plate / Plate Thickness in Plate Particles) 1) In case of powder 5 to 20 mg of powder are dispersed in 100 ml of purified methanol to prepare a suspension, One drop of the suspension is dropped on the sample stand for coordinate electron microscope at a spot, and dried immediately. Next, a coordinate electron microscope (EFM manufactured by Elionix
-3000 type) 10,000 per particle dispersed
Observing at 50,000 times, measuring the major axis (plate diameter) and the thickness (plate thickness) of at least 50 particles and averaging the ratio (plate diameter / plate thickness) is defined as the aspect ratio. .

2) In the case of particles in film 3.2 or more in the longitudinal and lateral directions including the particles to be measured is 3.2.
The film stretched more than twice is sliced with a microtome, and the section is manufactured by Hitachi Ltd., transmission electron microscope (TEM).
H-800) and observe at 20,000 times. The major axis (plate diameter) and the thickness (plate thickness) of at least 30 particles visible in the section are measured, and the ratio (plate diameter / plate thickness) is averaged to obtain the aspect ratio.

(3) Film running friction coefficient (μk) The film is measured as follows using the apparatus shown in FIG.
In FIG. 1, 1 is an unwind reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers,
4 is tension detector (inlet), 7 is stainless steel SU
Fixed rod made of S304 (outer diameter 5 mmφ, surface roughness = 0.0
2 μm), 10 is a tension detector (exit), 12 is a guide roller, and 13 is a take-up reel.

Width 1/2 in an environment of temperature 20 ° C. and humidity 60%
The film slit into inches is attached to 7 fixed rods at an angle θ =
They are brought into contact with each other at (152/180) π radians (152 °) and moved (rubbed) at a speed of 200 cm per minute. Outlet tension (T ₂ : g) when adjusting the tension controller 2 so that the inlet tension T ₁ is 35 g
Is detected by the exit tension detector after the film has run 90 m, and the running friction coefficient μk is calculated by the following equation.

[0038]

[Number 1] μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35)

(4) Flatness of film surface Ra (center line average roughness) is measured according to JIS B 0601. Using a stylus-type surface roughness meter (SURFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd., a chart (film surface roughness curve) is applied under the condition of a needle radius of 2 μm and a load of 0.07 g to obtain a film surface. A portion of the measurement length L is extracted from the roughness curve in the direction of the center line, and the center line of the extracted portion is taken as the X axis, and the longitudinal magnification direction is taken as the Y axis, and the roughness curve is expressed as Y = f (x). Then, the value (Ra: μm) obtained by the following equation is defined as the flatness of the film surface.

[0040]

[Equation 2]

In the present invention, 8 pieces are measured with a reference length of 0.25 mm, and Ra is expressed as an average value of 5 pieces obtained by removing 3 pieces from the larger value.

(5) Scratch resistance and abrasion resistance In a device similar to that used in FIG. 1 used for measuring the running friction coefficient μk, a magnetic tape was used, the winding angle was 30 degrees, and the inlet speed was 300 m / min. Run for 200 m with a tension of 50 g. The shavings adhering to the fixed rod 7 after running and the scratches of the tape after running are evaluated. At this time, a 6φ tape guide (surface roughness Ra =
0.15 μm) is used as method A, and a 6φ tape guide made of carbon black-containing polyacetal is used as method B.

<Judgment of shavings> ⊚: No shavings are observed at all ◯: Slightly shavings are seen Δ: Presence of shavings can be seen at a glance ×: Shavings are extremely adhered <Scratch judgment > ⊚: No scratches found ◯: 1 to 5 scratches found Δ: 6 to 15 scratches found ×: 16 or more scratches found

[0044]

Examples 1 to 15 and Comparative Examples 1 to 12 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and a lubricant as shown in Table 1. Two
Polymerization was carried out in the usual manner by adding the additive particles shown in (1) to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62 (o-chlorophenol, 35 ° C.).

The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours, then fed to an extruder hopper and melted at a melting temperature of 280 to 300 ° C. The molten polymer was surface-finished through a 1 mm slit die to give a surface finish of 0.
It was extruded onto a rotary cooling drum having a surface temperature of 20 ° C. for about 3 s to obtain an unstretched film of 200 μm. The unstretched film thus obtained is preheated at 75 ° C. and further stretched 3.6 times by heating with an IR heater having a surface temperature of 900 ° C. from above 15 mm between low speed and high speed rolls. Then, it was rapidly cooled, then fed to a stenter, and stretched 3.9 times in the transverse direction at 105 ° C. The obtained biaxially oriented film was heat set at a temperature of 205 ° C. for 5 seconds to obtain a heat set biaxially oriented film having a thickness of 14 μm.

The characteristics of this film are shown in Tables 1, 2, and 3.

On the other hand, 100 parts by weight of γ-Fe ₂ O ₃ (hereinafter, simply referred to as “part”) and the following composition were kneaded and dispersed in a ball mill for 12 hours.

Polyester polyurethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black 1 part Butyl acetate 70 parts Methyl ethyl ketone 35 parts Cyclohexanone 100 parts Further dispersed fatty acid oleic acid 1 part Palmitic acid 1 part Fatty acid ester (amyl stearate) 1 part was added and kneading was continued for 15 to 30 minutes. Furthermore, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added,
A high-speed shear dispersion was carried out for 1 hour to prepare a magnetic coating liquid.

The obtained coating solution was applied onto the above-mentioned biaxially oriented polyester film having a thickness of 14 μm to give a dry film thickness of 3.5 μm.
Was applied so that Then, after orientation treatment in a DC magnetic field, it was dried at 100 ° C. After drying, it is calendered and slit into a 1/2 inch width to give a thickness of 17.
A 5 μm magnetic tape was obtained. The characteristics of this tape are shown in Table 1.
2,3,4.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

As is clear from the results of Tables 1, 2, 3, and 4, when the plate-like boron nitride fine particles were used, they were excellent in abrasion resistance and scratch resistance, which were useful as a base film for magnetic recording media. A polyester film is obtained.

[0055]

According to the present invention, it is possible to provide a polyester film which is excellent in abrasion resistance and scratch resistance, and is particularly useful as a base film of a magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for measuring a running friction coefficient (μk).

[Explanation of symbols]

 1 Unwinding reel 2 Tension controller 4 Tension detector (inlet) 7 Fixed rod 10 Tension detector (outlet) 13 Take-up reel

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Claims (1)

[Claims] 1. The aspect ratio is in the range of 3 to 20,
A polyester film containing 0.05 to 2.0% by weight of tabular boron nitride fine particles having an average particle diameter of 0.05 to 3 μm.