JPH05331299A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film excellent in cut resistance and scratch resistance, useful for magnetic recording media, etc., incorporated with aluminum oxide particles having each specific surface area, means diameter and alpha-type crystal form content and inert particles having specific mean diameter. CONSTITUTION:Pellets such as of polyethylene terephthalate incorporated with (A) 0.05-1wt.% of aluminum oxide particles 50-150m<2>/g in specific surface area, 0.05-0.3mum in means diameter and 3-30wt.% in the content of aluminum oxide with alpha-type crystal form and (B) 0.005-5wt.% of inert particles 0.3-1.2mum in mean diameter (e.g. calcium carbonate particles) are dried at 170 deg.C for 3hr and fed to a hopper followed by an extruder where the pellets are melted at 280-300 deg.C and extruded via a 1mm slit die onto a rotary cooling drum with a surface temperature of 20 deg.C into an undrawn film, which is, in turn, drawn between a low-speed roll and a high-speed roll and then further drawn transversely using a tenter, thus obtaining the objective polyester film excellent in cut and scratch resistances.

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 useful as a base film for magnetic recording media which does not damage various guides.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films are widely used 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 of the film manufacturing process and processing 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, the friction between the coating roll and the film surface is severe, and shavings are generated,
Scratches occur on the film surface. Also when used as a VTR or data cartridge, shavings and scratches are generated in the process of winding the cassette at high speed, and D /
It causes O.

Particularly in VTR applications, a metal guide or a plastic guide whose surface is not sufficiently finished may be used for a guide post fixed in a cassette for the purpose of cost reduction recently, but the surface of the guide post is extremely rough. .. For this reason, a conventional technique 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, JP-A-54- 57562
No.), or a method of precipitating fine particles containing calcium, lithium or phosphorus in the polymerization system (for example, Japanese Patent Publication No.
In a magnetic tape to which No. 2-32914) is applied and which does not have a back coat, shavings and scratches are generated in the step of winding the cassette at a high speed, and the D / O level is increased.

In order to solve such a problem, a method of adding fine particles having a high Mohs hardness to reduce scratches (for example, JP-A-1-306220 and JP-A-2-185533).
No.) has been proposed, this method is effective for the guide post for cost reduction, but the improvement effect is not sufficient for the metal guide with a good surface finish that has been used conventionally. there were. In addition, for the occurrence of scratches on a metal guide with a good surface finish,
There is also a method of improving it by using inactive particles that are slightly larger than fine particles, but conversely, the adverse effect of generation of shavings has been found.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present inventors have found that not only the conventionally used metal guide with a good surface finish but also the newly developed rough metal guide and The present invention has been achieved as a result of intensive research to develop a polyester film for a magnetic recording medium, which has good abrasion resistance and scratch resistance even for a plastic guide.

[0007]

That is, the present invention has a specific surface area of 50 to 150 m ² / g and an average particle diameter of 0.05 to
It contains 0.05-1% by weight of aluminum oxide particles of 0.3 μm, and the average particle size exceeds 0.3 μm and 1.2 μm.
A polyester film containing at least one of m or less inactive particles, wherein the aluminum oxide particles contain 3 to 30% by weight of α-type crystal form aluminum oxide.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aromatic glycol as a main glycol component. Such polyesters are substantially linear and have film-forming properties, especially film-forming by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, 2,
Examples thereof include 6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid and anthracenedicarboxylic acid. Examples of the aliphatic glycols include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, and fats such as cyclohexanedimethanol. Examples thereof include cyclic diols.

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

Among such polyesters, particularly polyethylene terephthalate, polyethylene-2,6-naphthalate, etc., such as total dicarboxylic acid component 8
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. 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. A cycloaliphatic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. 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)
An aromatic diol such as propane; an aliphatic diol having an aromatic ring such as 1,4-dihydroxydimethylbenzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. You can also

In the polyester of the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid. Those which are copolymerized or bonded at 20 mol% or less based on the total amount of the acid component are also included.

The aluminum oxide particles to be added to the polyester in the present invention have a specific surface area of 50 to 150.
m ² / g, preferably 50~130m ² / g, and the average particle size (average secondary particle size) is 0.05 to 0.3
μm. If the specific surface area is less than 50 m ² /, the primary particle size becomes too large and the scratch resistance is good, but shavings are likely to occur, and
Frequently damage the guide. On the other hand, the specific surface area is 1
When it exceeds 50 m ² / g, the primary particle diameter becomes too small, sufficient projections are no longer formed, and the effect of scratch resistance is lost. If the average particle size is less than 0.05 μm, the particles become too fine to form fine projections required for scrum-tch resistance and abrasion powder resistance. On the other hand, if it is larger than 0.3 μm, the particles are Aggregation is too large and shavings are easily generated.

It is necessary that the aluminum oxide particles further contain 3 to 30% by weight of a crystal form of α type crystal form. If the proportion of α-type crystal form aluminum oxide is less than 3% by weight, the effect of improving scratch resistance is not exhibited, while if it exceeds 30% by weight, the scratch resistance is good, but shavings are likely to occur, and The guide is often damaged, which is not preferable. As the crystal form other than the α-type crystal form in the aluminum oxide particles, one or more kinds of crystal forms selected from the group of θ-type, δ-type and γ-type are preferable.

The aluminum oxide particles may be a mixture of particles of each crystal form, a composite crystal form of two or more kinds of crystals, or a mixture thereof.

In such aluminum oxide particles, for example, a method of hydrolyzing an aluminum alkoxide to form an alumina hydrate gel, followed by drying and firing (aluminum oxide method), and thermal decomposition of aluminum sulfate or the like to separate acid groups. In the method of performing firing (acid method), the method of vaporizing aluminum chloride and the like and performing firing decomposition in oxyhydrogen (vapor phase method), etc. , Γ, δ type composition ratio can be variously controlled for production. Further, it can be produced by mixing the α-type crystal form aluminum oxide particles and the other crystal form aluminum oxide particles. Furthermore, the α-type crystal form aluminum oxide particles and the other crystal form aluminum oxide particles can be added to the polyester, respectively.

The content of aluminum oxide particles added in the present invention is 0.05 to 1% by weight based on the polyester.
Is. If this amount is less than 0.05% by weight, the effect of adding particles will be small, while if it is more than 1% by weight, particles will overlap and shavings will tend to occur.

In the present invention, the average particle size of the aluminum oxide particles together with the aluminum oxide particles exceeds 0.3 μm and 1.2 μm.
The following inert particles are added and contained.

This is because if there are no inert particles larger than aluminum oxide particles, the friction coefficient with respect to various guides becomes high, and not only scratch resistance and abrasion resistance are deteriorated, but also biaxially oriented polyester film is produced. It becomes difficult to handle in the process, and the running property deteriorates when used as a base film for magnetic recording media.
It depends. However, when the inert fine particles having a size larger than 1.2 μm are used, only a film having insufficient surface flatness can be obtained, which is not preferable in terms of electromagnetic conversion characteristics.

The amount of the inert particles added is preferably 0.005 to 5% by weight, more preferably 0.01 to 2% by weight.
If the addition amount is too small, the friction coefficient becomes high, and the action of the fine particles is insufficient. On the other hand, if the addition amount is too large, the dispersibility in the polymer is insufficient and the abrasion resistance is deteriorated.

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 and kaolin, organic inert particles such as silicone resin and crosslinked polystyrene, and It is possible to use particles internally deposited by the polymerization catalyst.

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

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

Although the reason why the polyester film of the present invention is excellent in abrasion resistance and scratch resistance is not clear, it is presumed that the α-type crystal form contained particles or the composite crystal-form particles containing the α-type crystal form are α-type. It has a larger particle size and higher hardness than other aluminum oxide particles that do not contain crystalline morphology, and forms strong protrusions on the film surface.
Properly dispersed in relatively small protrusions formed by other aluminum oxide particles that do not contain the type crystal morphology, and the protrusions are stabilized as a whole by interaction (the protrusions due to the α type crystal morphology are anchors, etc.), it is conceivable that.

The polyester film of the present invention is excellent in scratch resistance and abrasion resistance over a metal guide having a good surface finish, a metal guide having a poor surface finish, and a plastic guide, and particularly as a base film for a magnetic recording medium. It is useful.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Each characteristic value in the examples is based on the following method.

(1) Average Particle Size of Particles 1) When Obtaining Average Particle Size from Granules Shimadzu CP-50 Centrifugle Particle Size Analyzer (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 average particle diameter (Book Technology "Published by Nikkan Kogyo Shimbun, 1975, pages 242-24
7).

2) Particles in film A small piece of sample film is fixed on a sample stand for a scanning electron microscope, and a sputtering device (JFC-made by JEOL Ltd.) is used.
The film surface is subjected to ion etching treatment under the following conditions using a 1100 type ion etching apparatus). The condition is that the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, the voltage is 0.25 kV and the current is 1
Ion etching is performed at 2.5 mA for about 10 minutes. Further, gold sputtering is applied to the film surface with the same apparatus, and it is observed with a scanning electron microscope to 50,000 to 10,000.
Observation is performed twice, and the equivalent spherical diameter distribution of at least 100 particles is obtained by Luzex 500 manufactured by Nippon Regulator Co., Ltd., and the weight cumulative value is calculated from the point of 50%.

(2) Specific surface area of powder BET using Autosorb-1 manufactured by Kantachrome Co., Ltd.
The specific surface area is measured by the method.

(3) Content Ratio of α-Type Crystal Morphology in Aluminum Oxide Particles It is measured using a Rokuflex RV-200 type X-ray diffractometer manufactured by Rigaku Denki Co., Ltd. Aluminum oxide with 100% α-type crystal form (specific surface area = 100 m ² / g) and aluminum oxide with 100% α-type crystal form (specific surface area = 20 m ²
/ G) is used.

Γ-type 100 g-α-type 0 g; γ-type 80 g-α-type 20 g; γ-type 60 g-α-type 40 g; γ-type 4
0g-α type 60g; γ type 20g-α type 80g; γ type 0g
-Α type 100g; 6 levels were mixed well, 3g was sampled and measured at 2θ = 70 to 20 °, α
The peak height of 2θ = 57.5 ° peculiar to the type crystal morphology,
The weight ratio of the α-type crystal form is plotted and a calibration curve is prepared. The content of α-type aluminum oxide in each sample is measured in the same manner as the above measurement conditions and calculated from the height of the peak at 2θ = 57.5 ° using a calibration curve.

(4) Coefficient of running friction of film (μk) It 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 a tension detector (inlet), and 7 is a fixing rod made of stainless steel SUS304 (outside). Diameter 5mmφ, surface roughness Ra =
0.02 μm), 10 is a tension detector (exit), 1
Reference numeral 2 is a guide roller, and 13 is a take-up reel.

At a temperature of 20 ° C. and a humidity of 60%, the width is 1 /
The film cut into 2 inches is attached to a fixed rod of 7 at an angle θ =
(152/180) π radians (152 °) are brought into contact and moved (rubbed) at a speed of 200 cm per minute. When the tension controller 2 is adjusted so that the inlet tension T ₁ becomes 35 g, the outlet tension (T ₂ : g) is detected by the outlet tension detector after the film has run 90 m, and the running friction coefficient μk is calculated by the following formula. calculate. μk = (2.303 / θ) log (T ₂ / T ₁ ) = 0.
868log (T _2/35)

(5) Flatness of film surface Ra (center line average roughness) is measured according to JIS B 0601 by Tokyo Seimitsu Co., Ltd. stylus type surface roughness meter (SU).
RFCOM3B), needle radius 2μm, load 0.07g
Draw a chart (film surface roughness curve) under the conditions of, and extract a portion of the measurement length L from the obtained film surface roughness curve in the direction of the center line, and use the center line of the extracted portion as the X axis, When the roughness curve Y = f (x) is expressed with the direction of longitudinal magnification as the Y axis, the value (Ra: μm) given by the following equation is defined as the flatness of the film surface.

[0034]

[Equation 1]

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.

(6) Scratch resistance and abrasion resistance In the same apparatus as used in FIG. 1 used for measuring the running friction coefficient μk, the winding angle was 30 degrees and the inlet tension was 50 g at a speed of 300 m / min. Run the length shown below. The shavings adhering to the fixed rod 7 after running and the scratches of the tape after running are evaluated. At this time, the fixed rod is made of SUS304, and its surface is finished to 6 mm.
When a φ tape guide (surface roughness Ra = 0.015 μm) is used, the A method (300 m travel), the SUS sintered plate is bent into a cylindrical shape and the surface finish is insufficient 6 mm φ tape guide (surface roughness Ra = 0.15 μm) is used for the B method (running for 200 m), and a 6 mmφ tape guide made of carbon black-containing polyacetal is used for the C method (2).
00m).

<Judgment of shavings> ◎: No shavings are observed ○: Slightly shavings are seen △: Presence of shavings is visible at a glance ×: Shavings are severely adhered

<Scratch Judgment> ⊚: No scratches were found ◯: 1 to 5 scratches were found Δ: 6 to 15 scratches were found ×: 16 or more scratches were found

[0039]

Examples 1 to 9 and Comparative Examples 1 to 10 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. The particles shown in 2 were added and polymerized by an ordinary method to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62 (orthochlorophenol, 35 ° C.).

The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours and then fed to an extruder hopper,
Melt at a melting temperature of 280 to 300 ° C., and surface finish this molten polymer through a 1 mm slit die for 0.3 s.
Extruded on a rotating cooling drum with a surface temperature of 20 ° C.
An unstretched film of 00 μm was obtained.

The unstretched film thus obtained is preheated at 75 ° C., and further 15 m between low speed and high speed rolls.
From above, it was heated with one IR heater having a surface temperature of 900 ° C., stretched to 3.6 times, rapidly cooled, then supplied to a stenter, and stretched laterally to 3.9 times 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 and 2.

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 mixed with a ball mill to obtain 12 parts.
Kneading and dispersion were carried out for an hour.

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 After dispersion, fatty acid oleic acid 1 part Palmitic acid 1 part Fatty acid ester (amyl stearate) 1 part is added and kneading is continued for 15 to 30 minutes. Furthermore, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added,
High-speed shear dispersion was carried out for 1 hour to prepare a magnetic coating solution.

The obtained coating solution was applied onto the above described polyester film having a thickness of 14 μm so that the dry film thickness would be 3.5 μm.

Then, after orientation treatment in a DC magnetic field, 10
It was dried at 0 ° C. After drying, it was calendered and slit into a width of 1/2 inch to obtain a magnetic tape having a thickness of 17.5 μm.

The characteristics of this magnetic tape are shown in Tables 1 and 2.

[0048]

[Table 1]

[0049]

[Table 2]

As is clear from the results of Tables 1 and 2, when aluminum oxide particles containing aluminum oxide whose crystal form is α type were used, the abrasion resistance and scratch resistance useful as the base film of the magnetic recording medium were obtained. An excellent polyester film can be obtained.

[0051]

According to the present invention, a metal guide having a good surface finish, a metal guide having a poor surface finish, and a plastic guide are excellent in scratch resistance and abrasion resistance, and particularly as a base film of a magnetic recording medium. A useful film can be provided.

[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

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area // B29K 67:00 B29L 7:00 4F

Claims (3)

[Claims] 1. An aluminum oxide particle having a specific surface area of 50 to 150 m ² / g and an average particle diameter of 0.05 to 0.3 μm is contained in an amount of 0.05 to 1% by weight, and an average particle diameter of 0.3 μm.
A polyester film containing at least one kind of inactive particles having a size of more than 1.2 m and not more than 1.2 m, wherein the aluminum oxide particles contain 3 to 30% by weight of α-type crystal form aluminum oxide. Polyester film. 2. The polyester film according to claim 1, wherein the crystal form of aluminum oxide other than α-type is at least one selected from the group of θ-type, δ-type and γ-type. 3. The polyester film according to claim 1, wherein the content of the inert particles is 0.005 to 5% by weight.