JPH061864A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film useful as a base film of a magnetic recording medium, which is excellent in chipping and scratch resistances and does not injure a well-surface-finished metallic guide, an insufficiently surface-finished metallic guide and a plastic guide. CONSTITUTION:The title film contains 0.05-1wt.%, based on the polyester, inert particles (A) having a specific surface area of 50-150m<2>/g and a mean particle diameter of 0.05-0.3mum 3-30wt.%, based on component A, alumina having a mean particle diameter of 0.1-0.3mum and 0.005-5wt.%, based on the polyester, inert particles ' having a mean particle diameter of 0.3-1.2mum.

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 of a magnetic recording medium which does not damage various guides.

[0002]

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

In a 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. When 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 a 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 scraping property of a 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-54-54). 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 the magnetic tape to which the back coat is not applied, the D / O level is increased due to the generation of shavings and scratches in the process of winding the cassette at a high speed.

In order to solve such problems, a method of adding fine particles having high Mohs hardness to reduce scratches (for example, JP-A-1-306220, JP-A-2-18553).
No. 3) has been proposed, but this method is effective for the guide post for cost reduction, but the improvement effect is insufficient for the metal guide with a good surface finish that has been used conventionally. Met. There is also a method to improve scratches on a metal guide with a good surface finish by using a combination of slightly larger inert particles than fine particles, but the adverse effect of shavings is also found. ing.

[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 size of 0.05 to
0.3 μm of the inert particles A was added to the polyester in the range of 0.
05 to 1% by weight, with an average particle size of 0.1 to 0.3 μm
Α-alumina of 3 to 30% by weight based on the inert particles A, and the average particle size exceeds 0.3 μm and 1.2 μm.
Inert particles B of m or less are added to the polyester in an amount of 0.00
The polyester film contains 5 to 5% 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 film formation by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid and anthracenedicarboxylic acid. You can 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 and decamethylene glycol, and alicyclic compounds such as cyclohexanedimethanol. Examples thereof include diols.

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

Among such polyesters, especially 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 can 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 are used. Those which are copolymerized or bonded at 20 mol% or less based on the total amount of the acid component are also included.

The inert particles A added to the polyester in the present invention have a specific surface area of 50 to 150 m ² /
g, preferably 50 to 130 m ² / g, and an inactive particle having an average particle size (average particle size of secondary particles) of 0.05 to 0.3 μm. If the specific surface area is less than 50 m ² / g, the primary particle diameter becomes too large and the scratch resistance is good, but shavings are likely to be generated and the guide is often damaged. On the other hand, the specific surface area is 15
If it exceeds 0 m ² / g, the primary particle size becomes too small,
Sufficient protrusions are no longer formed, and the effect of scratch resistance is lost. If the average particle size is less than 0.05 μm, the fine particles become too fine to form fine projections required for scratch resistance and abrasion resistance, while if it is larger than 0.3 μm, the lubricant is Aggregation is too large and shavings are easily generated.

As the inert particles A, titanium dioxide and / or silicon dioxide can be preferably used. Further, a composite oxide composed of two or more kinds of components selected from the group consisting of titanium dioxide, silicon dioxide and aluminum oxide can also be preferably used.

The inert particles A are not limited by the manufacturing method, and those manufactured by various methods can be used. For example, for silicon dioxide,
A method of hydrolyzing a silicate such as sodium silicate to disperse solid primary particles in water, and then drying colloidal particles to form porous particles (silicate sol-gel method), silicon tetrachloride Those produced by a method of vaporizing and performing combustion decomposition in oxyhydrogen (vapor phase method) or the like can be used. Regarding titanium dioxide, a method of thermally decomposing a sulfate salt such as titanium sulfate to separate acid groups and firing (acid method), a method of vaporizing titanium tetrachloride and performing combustion decomposition in oxyhydrogen ( What was manufactured by the vapor phase method) etc. can be used. Of these, titanium dioxide synthesized by a vapor phase method is preferable because of its high effect. Further, as the complex oxide, for example, one produced by a method in which two or more kinds of vapors selected from aluminum chloride, titanium tetrachloride and silicon tetrachloride are simultaneously supplied into an oxyhydrogen flame and subjected to high temperature hydrolysis is used. be able to. The added content of the inert particles A is 0.05 to 1% by weight based on the polyester. If this addition amount is less than 0.05% by weight, the effect of adding fine particles becomes small, while if it is more than 1% by weight,
Overlapping particles are seen, and shavings are likely to occur.

In the present invention, the α-alumina used together with the inert particles A has an average number diameter of 0.1 to 0.3 μm. If the average particle size is less than 0.1 μm, the fine particles become too fine to form minute projections necessary for scratch resistance, while if it is larger than 0.3 μm, the projections become too large and the guide Often hurt.

Such α-alumina is prepared by, for example, hydrolyzing an aluminum alkoxide to form an alumina hydrate gel, followed by drying and baking (aluminum oxide method), and thermal decomposition of aluminum sulfate to separate acid groups. It can be produced by a method of performing firing (acid method), a method of vaporizing aluminum chloride or the like and performing combustion decomposition in oxyhydrogen (vapor phase method), and the like.

The content of α-alumina added is 3 to 30% by weight with respect to the inert particles A. This amount is 3% by weight
If it is less than, the effect of improving scratch resistance is not expressed,
On the other hand, if it exceeds 30% by weight, scratch resistance is good, but shavings are likely to occur, and the guide is often damaged, which is not preferable.

In the present invention, the inert particles A and the inert particles B used in combination with the α-type alumina have an average particle size of 0.3 μm.
It is an inert particle of more than 1.2 m and less than 1.2 m. If the inactive particles B (in other words, the inactive particles A and the inactive particles having a particle size larger than that of α-alumina) do not exist, the friction coefficient with respect to various guides becomes high, and the scratch resistance and the abrasion powder resistance are deteriorated. In addition to this, the handling property in the manufacturing process of the biaxially oriented polyester film becomes difficult, and the running property when used as a base film for a magnetic recording medium deteriorates. However, when the inert particles B having a large size of 1.2 μm are used, only a film having insufficient surface flatness is obtained, which is not preferable in terms of electromagnetic conversion characteristics and the like.

The content of the inert particles B added is 0.005 to 5% by weight, more preferably 0.01 to 5% by weight, based on the polyester.
It is preferably 2% by weight. If the addition amount is too small, the friction coefficient becomes high, and the action of the fine particles is not sufficient. 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 B 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,
Also, internally deposited particles due to the polymerization catalyst can be used.

In the polyester film of the present invention, for example, polyester is melt-extruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. and rapidly cooled to obtain an intrinsic viscosity of 0.35.
To 0.9 dl / g of unstretched film is obtained, and the unstretched film is uniaxially (lengthwise or transversely) (Tg-10) to
Stretching at a temperature of (Tg + 70) ° C. (however, Tg: glass transition temperature of polyester) at a draw ratio of 2.5 to 5.0,
Next, in the direction perpendicular to the above-mentioned stretching direction (when the first stage stretching is the longitudinal direction, the second stage stretching is the transverse direction), Tg (° C)-
It can be produced by stretching at a temperature of (Tg + 70) ° C. and 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 + 7
It can be heat-set at a temperature of 0) ° C. 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.

The reason why the polyester film of the present invention is excellent in abrasion resistance and scratch resistance is not clear, but α
The type alumina has a high hardness and forms protrusions stronger than the inactive particles A on the film surface, and these protrusions form the inactive particles A.
From the reasonably scattered in the protrusions formed by,
It is considered that these interactions stabilize the projections as a whole by, for example, the projections of α-type alumina becoming anchors.

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 magnetic recording media. It is useful.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In addition, 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 Powder CP-50 Model Centrifugal Particle Size Analyzer (Centrifugal Particle Si) manufactured by Shimadzu Corporation
ze Analyzer). The particle diameter corresponding to 50 mass% is read from the integrated curve of the particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the amount thereof,
This value is defined as the above average particle size (Book “Particle size measuring technology”, published by Nikkan Kogyo Shimbun, 1975, pages 242 to 247).

2) Particles in the film A small piece of the sample film is fixed on a sample stand for a scanning electron microscope, and a sputtering device manufactured by JEOL Ltd. (JFC-1) is used.
The film surface is subjected to ion etching treatment under the following conditions using a 100 type ion etching apparatus). condition is,
Place the sample in a bell jar, raise the degree of vacuum to a vacuum state of about 10 ^-3 Torr, voltage 0.25 KV, current 12.
Ion etching is performed at 5 mA for about 10 minutes. Further, gold sputtering was applied to the film surface by the same apparatus, and the film was observed with a scanning electron microscope at 50.000 to 10.000 times, and Luzex 500 manufactured by Nippon Regulator Co., Ltd.
To find the equivalent spherical diameter distribution of at least 100 particles,
The weight is calculated from the point of 50%.

(2) Specific surface area of powder, total pore volume BET was measured by using Autosorb-1 manufactured by Kantachrome Co., Ltd.
The specific surface area and total pore volume are measured by the method.

(3) 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), 7 is stainless steel SUS
304 fixed rod (outer diameter 5 mmφ, surface roughness Ra = 0.0
2 μm), 10 is a tension detector (exit), 12 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 that is slit into 2 inches is attached to 7 fixed rods at angle θ.
= (152/180) π Radial (152 °) is brought into contact and moved (rubbed) at a speed of 200 cm per minute. The exit tension (T ₂ : g) when the tension controller 2 is adjusted so that the entrance 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 formula. calculate.

[0031]

[Equation 1]

(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 drawn under the conditions of a needle radius of 2 μm and a load of 0.07 g to obtain a film. A portion of the measurement length L is extracted from the surface roughness curve in the direction of the center line, the center line of the extracted portion is taken as the X axis, the longitudinal magnification direction is taken as the Y axis, and the roughness curve Y = f (x) When expressed, the value (Ra: μm) given by the following equation is defined as the flatness of the film surface.

[0033]

[Equation 2]

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

(5) Scratch resistance and abrasion resistance In the device similar to that used in FIG. 1 used for measuring the running friction coefficient μk, the winding angle was set to 30 ° and the inlet tension was set to 50 g at a speed of 300 m / min. And run for 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, as a fixing rod, a 6φ tape guide made of SUS304 having a sufficiently finished surface (surface roughness R
a = 0.015 μm) A method (running for 300 m), a 6φ tape guide (surface roughness Ra = 0.15 μ) in which the SUS sintered plate is bent into a cylindrical shape and the surface finish is insufficient.
m) is used as method B (running 200 m), and the case where a 6φ tape guide made of carbon black-containing polyacetal is used as method C (running 200 m).

<Judgment of shavings> ⊚: No shavings are observed at all ◯: Slightly shavings are seen Δ: Presence of shavings can be seen at a glance X: 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

[0038]

Examples 1 to 10 and Comparative Examples 1 to 11 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and Table 1 as a lubricant. The additive particles shown in 2 were added and polymerized by a conventional 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,
It is melted at a melting temperature of 280 to 300 ° C., and this molten polymer is extruded through a 1 mm slit die onto a rotary cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C.
An unstretched film of 0 μm was obtained.

The unstretched film thus obtained is preheated at 75 ° C., and further 15 mm between low speed and high speed rolls.
It was heated from above by one IR heater having a surface temperature of 900 ° C., stretched 3.6 times, rapidly cooled, and then supplied to a stenter and stretched laterally 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 performed for an hour.

[0043] 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,
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 thick film had a thickness of 35 μm. Then, after orientation treatment in a DC magnetic field, 10
It was dried at 0 ° C. After drying, calendering treatment was performed and slit to 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.

[0046]

[Table 1]

[0047]

[Table 2]

As is clear from the results shown in Tables 1 and 2, when a small amount of aluminum oxide having a crystal form of α type is used, a polyester having excellent abrasion resistance and scratch resistance, which is useful as a base film of a magnetic recording medium. The film is obtained.

[0049]

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 all excellent in scratch resistance and abrasion resistance, and particularly as a base film of a magnetic recording medium. A particularly 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

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Claims (4)

[Claims] 1. An inactive particle A having a specific surface area of 50 to 150 m ² / g and an average particle size of 0.05 to 0.3 μm is contained in an amount of 0.05 to 1% by weight with respect to the polyester. Α-alumina of 0.1 to 0.3 μm is contained in an amount of 3 to 30% by weight based on the inert particles A, and the average particle size is 0.3.
A polyester film which comprises 0.005 to 5% by weight of an inert particle B having a size of more than 1.2 μm and not more than 1.2 μm with respect to the polyester. 2. The polyester film according to claim 1, wherein the inert particles A are titanium dioxide and / or silicon dioxide. 3. The polyester film according to claim 1, wherein the inactive particles A is a composite oxide composed of two or more components selected from the group consisting of titanium dioxide, silicon dioxide and aluminum oxide. 4. The polyester film according to claim 2, wherein the titanium dioxide is titanium dioxide synthesized by a flame hydrolysis method of titanium tetrachloride.