JPH06234907A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film which is excellent in resistance to shaving and travelling properties and useful as a base film of a magnetic recording medium. CONSTITUTION:A polyester film contains fine platy alumina hydrate particles having aspect ratios of 3-10 and a mean particle size of 0.1-3mum in an amt. of 0.05-2wt.% of the polyester.

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 running and is 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 widely used for magnetic recording media because of their excellent physical and chemical properties.

In a biaxially oriented polyester film, its running property and abrasion resistance are major factors that affect the workability of the film manufacturing process and the processing process and the product quality. When these are insufficient,
For example, in the step of applying a magnetic layer to the surface of a biaxially oriented polyester film and performing a calendering process, the friction between the calender roll and the film surface is severe, and shavings are generated,
It also causes dropout when used as a magnetic tape.

Particularly, a high-strength base film for a long-time recording magnetic tape is manufactured by increasing the surface area of stretching, but in that case, large voids are easily formed around the lubricant, which causes deterioration of calendering.

In order to improve the calendering property, it is preferable to reduce the peak stress between the calender roll and the surface projections formed by the lubricant, but the higher the projection height, the sharper the projection shape. The more
The protrusions dig into the compliant rolls of the calender, making them more susceptible to peaking stress.

To improve the running property, the center line average roughness (Ra) may be increased, but in order to increase Ra, the lubricant concentration should be increased or the particle size should be increased. I have to. However, increasing the addition concentration and increasing the particle size are in a bad direction for calendering because the former increases the number of particles that cause calendering and the latter increases the peak stress received from the calender roll. . In addition, when the surface becomes rough, electromagnetic conversion characteristics deteriorate and the slipperiness becomes too good to make the tape running unstable, and edge damage occurs, for example, in a collared roll in a VTR.

Therefore, a conventional technique for improving the running property and abrasion resistance of the film, for example, a method of adding inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate (for example, JP-A-54-57562) is used. In the applied magnetic tape having no back coat, calendering occurs and increases with an increase in the surface area of stretching, and the dropout level deteriorates. These defects become remarkable when lump-shaped particles having a small aspect ratio are added.

Further, a method is known in which alumina fine particles are added to the inorganic particles to improve the abrasion resistance (including scratch resistance), but the abrasion resistance to various guide pins during running of the magnetic tape is improved. However, since the particle shape is spherical or lumpy, it is not effective in improving calendar abrasion and edge damage.

In order to solve such a problem, a method of adding organic resin particles as a soft material (for example, European Patent [Publication] 2296 in which true spherical silicon resin particles are added)
No. 70) is proposed, but it is effective in calendering due to the effect of relaxing the peak stress,
There is a problem that the effect of edge damage is small and the cost of organic resin particles is high.

[0010]

In view of the above circumstances, the present inventor has found that the abrasion resistance (especially calendar abrasion) does not deteriorate even when the surface magnification at the time of stretching is increased, and the edge damage resistance during tape running is improved. The present invention has been achieved as a result of intensive research to produce an excellent polyester film for magnetic recording media.

[0011]

That is, the present invention provides plate-like alumina hydrate fine particles having an aspect ratio of particles of 3 to 10 and an average particle diameter of 0.1 to 3 μm. The polyester film contains 0.05 to 2% by weight of polyester.

The polyester in the present invention is a polyester containing 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 forming properties by melt molding.

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

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. Aliphatic diol etc. can be mentioned.

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

Among such polyesters, especially polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid or 2,6-naphthalenedicarboxylic acid, and total glycol. A copolymer in which 80 mol% or more of the component is ethylene glycol is preferable. In that case, 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acid other than terephthalic acid or 2,6-naphthalenedicarboxylic acid, and, for example, adipic acid,
It may be an aliphatic dicarboxylic acid such as sebacic acid or the like, 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 glycols other than ethylene glycol, and aromatic diols such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane, 1, It is also possible to use an aliphatic diol having an aromatic ring such as 4-dihydroxydimethylbenzene, polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

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

Further, in the polyester of the present invention, a polycarboxylic acid or a polyhydroxy compound having three or more functional groups, such as trimellitate, is added in an amount in a range which is substantially linear, for example, an amount of 2 mol% or less based on the total acid component. It also includes a copolymer of acid and pentaerythritol.

The above polyesters are known per se,
And it can be manufactured by a method known per se.

As the above polyester, those having an intrinsic viscosity of about 0.4 to about 0.9 measured at 35 ° C. as a solution in o-chlorophenol are preferable.

In the present invention, the tabular alumina hydrate fine particles to be added to the polyester have an aspect ratio of 3
10 to 10, preferably 5 to 8, and an average particle size of 0.1 to 3 μm, preferably 0.1 to 3 μm.
It is in the range of 1 μm. When the aspect ratio is smaller than 3, the powder shape becomes close to a lump, and the projections on the film surface due to the particles are sharpened, and shavings are likely to be generated during the calendar treatment. On the other hand, when the aspect ratio is larger than 10, the layered structure of the particles becomes strong, so that the dispersibility in the polymer becomes poor and the film surface becomes rough and shavings are easily generated. However, particles having a shape other than the aspect ratio described above may be mixed in as long as the object of the present invention is not impaired.

The average particle diameter of the fine particles is 0.1 μm.
If it is less than the range, the fine particles become too fine to form protrusions necessary for running performance. On the other hand, if it is larger than 3 μm, the film surface becomes rough and edge damage and shavings are likely to occur.

The alumina fine particles that have been conventionally used are calcined alumina fine particles, but the fine particles of the present invention are uncalcined alumina hydrate (aluminum hydroxide) fine particles. Therefore, the hardness of the powder is soft, and the projections formed on the film surface are also soft, which has the advantage of being difficult to scrape.

The morphology of the plate-like alumina hydrate fine particles in the present invention may be either crystalline or gel-like. For example, crystalline ones include boehmite, gibbsite, bayerite, etc. Examples include pseudo-boehmite and alumina gel.

The fine particles can be obtained from any of natural products and synthetic products (hydrothermal synthesis method, alkoxide method, hydrolysis method, etc.) and are not particularly limited by the synthesis method. Impurities (silicon oxide, transition alumina, etc.) may be contained within a range that does not impair the object of the present invention.

In the present invention, the addition amount of such plate-like alumina hydrate fine particles is 0.05 to 2% by weight. If the amount added is less than 0.05% by weight, the effect of addition of the fine particles becomes small and the running property deteriorates. On the other hand, if it exceeds 2% by weight, the dispersion of the particles becomes poor and shavings are likely to occur.

In the present invention, other inactive particles may be used together with the plate-like alumina hydrate fine particles as long as the object of the present invention is not impaired.

The type of the other inert particles is not particularly limited, and examples thereof include inorganic inert particles such as calcium carbonate, silicon dioxide, titanium oxide, barium sulfate and zeolite, organic resins such as silicone resin and crosslinked polystyrene. Inert particles, particles internally deposited by a polyester polymerization catalyst, and the like can be used. The average particle diameter and the addition amount may be selected within the range of the conventionally known average particle diameter and the addition amount. The polyester film of the present invention has, for example, a melting point (Tm: ° C.) to (Tm + 70)
Polyester is extruded at a temperature of ℃ to obtain an intrinsic viscosity of 0.35
To 0.9 dl / g of unstretched film, and the unstretched film is uniaxially (longitudinal or lateral) (Tg-10).
At a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polyester) at a draw ratio of 2.5 to 5.0, and then at a direction perpendicular to the above-mentioned stretching direction (when the first-stage stretching is in the longitudinal direction). Indicates that the second stage drawing is in the transverse direction)
It can be produced by stretching at a temperature of (° C) to (Tg + 70) ° C at a draw ratio of 2.5 to 5.0 times. In this case, the area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching, but sequential biaxial stretching is preferred.

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

The polyester film of the present invention has good running properties,
It is not clear why it excels in abrasion resistance, but
Hardness is moderately soft, and alumina hydrate fine particles excellent in dispersibility in the polymer due to the surface charge of the particles are used. Further, by making the particle shape into a plate shape having an aspect ratio of 3 to 10, The protrusions on the film surface have a trapezoidal gentle shape, and the affinity (adhesion) with polyester is improved compared to the lump-shaped particles, so the shavings can be maintained while maintaining the running property on the film. It is estimated to decrease.

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

[0032]

EXAMPLES The present invention will be described in more detail below with reference to examples. Each characteristic value in the examples was measured by the following method.

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

2) Particles in film A small piece of film was fixed on a sample stand for a scanning electron microscope (S-570 type) manufactured by Hitachi, Ltd., and was sputtered by JEOL Ltd. (JFC-). The film surface is subjected to ion etching treatment under the following conditions using a 1100 type ion etching apparatus). That is, the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 100-3 Torr, and ion etching is performed at a voltage of 0.25 KV and a current of 12.5 mA for about 10 minutes. After that, with the same device,
Gold sputtering is applied to the surface of the film, and the surface of the gold sputtering is 10,000 to 50,000 with a scanning electron microscope.
Observed at 0 times, the equivalent spherical diameter distribution of at least 100 particles is obtained by Luzex 500 manufactured by Nippon Regulator Co., Ltd., and calculated from the point of 50% weight integration.

(2) Aspect Ratio of Particles (Plate Diameter / Plate Thickness of 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, A drop of the suspension is put on a sample stage for a coordinate electron microscope and dried immediately. Next, a coordinate electron microscope (EMM manufactured by Elionix
-3000) per 10,000 dispersed particles
It is observed at a magnification of up to 50,000 times, the major axis (plate diameter) and the thickness (plate thickness) of at least 50 particles are measured, and the value obtained by averaging the ratios (plate diameter / plate thickness) is taken as the aspect ratio.

2) In case of particles in film A film containing particles to be measured and stretched 3.2 times or more in at least one of the longitudinal and lateral directions is sliced with a microtome, and a section is made by Hitachi, transmission electron microscope (TE).
MH-800 type) and observed at 20,000 to 30,000 times. The major axis (plate diameter) and the thickness (plate thickness) of at least 30 particles seen in the section are measured, and the average of the ratios (plate diameter / plate thickness) is defined as the aspect ratio.

(3) Coefficient of running friction (μk) of film The measurement is carried out 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 (outlet), 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%
A film slit into inches is attached to the fixed rod 7 at an angle θ =
They are brought into contact with each other at (152/180) π radial (152 °) and moved (rubbed) at a speed of 200 cm per minute. When the tension controller 2 is adjusted so that the inlet tension (T1) is 35 g, the outlet tension (T2:
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.

[0039]

## EQU1 ## μk = (2.303 / θ) log (T2 / T1) = 0.868 log (T2 / 35)

(4) Flatness of film surface Ra (center line average roughness) is measured according to JIS B 0601. Stylus-type surface roughness meter (S manufactured by Tokyo Seimitsu Co., Ltd.)
URFCOM 3B) was used to draw a chart (film surface roughness curve) under the conditions of a needle radius of 2 μm and a load of 0.07 g, and from the obtained film surface roughness curve, the measurement length L was measured in the direction of the center line. When the roughness curve Y = f (x) is expressed with the center line of the extracted portion as the X axis and the direction of the vertical magnification as the Y axis, the value (Ra: μm) obtained by the following equation is obtained. It is defined as the flatness of the film surface.

[0041]

[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) Calendering Ability With a three-stage mini super calendering device (made by Yuri Roll Co., Ltd.) having an elastic roll made of nylon, heating roll temperature 80 ° C., linear pressure 160 Kg / cm, speed 120 m / min. The film slit to a width of 150 mm is treated for 5000 m, and the sharpness is evaluated by the stain condition on the elastic roll. The evaluation criteria are as follows. <Scraped powder determination> ⊚: No dirt is recognized on the surface of the elastic roll. ◯: Although the gloss of the surface of the elastic roll is slightly lowered, no shavings are attached. Poor: Adhesion of scraped powder is recognized on the surface of the elastic roll.

(6) Edge Damage After making polyester film into a magnetic tape with BR6400 manufactured by JVC and running it for 50 passes, the end face is observed with a scanning electron microscope to check for scratches. The evaluation criteria are as follows. <Judgment of edge damage> ⊚: No scratch is observed. ○: There are some scratches, but no actual damage. Δ: Scratches are present, but there is no actual damage. X: Damaged as can be seen visually.

[0045]

Examples 1 to 10 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 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 (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 0.1.
It was extruded on a rotary cooling drum having a surface temperature of 20 ° C. for about 3 s and rapidly cooled to obtain an unstretched film having a thickness of 200 μm.
The unstretched film thus obtained is preheated to 75 ° C., and 90 mm from above 15 mm between low speed and high speed rolls.
4.4 by heating with one IR heater with a surface temperature of 0 ° C
The film was stretched twice, then fed to a stenter, and stretched 3.5 times in the transverse direction at 90 ° 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 13 μm.

In Example 7, dimethyl-2,6-naphthalate was used instead of dimethyl terephthalate to prepare polyethylene-2,6-naphthalate pellets, and the melting temperature was 280 to 310 ° C. and the heat setting temperature was 215 ° C. And other conditions were the same as in Example 1 to obtain a heat-fixed biaxially oriented film.

On the other hand, 100 parts by weight of γ-Fe2O3 (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 Cyclohexane 100 parts After dispersion 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, and the mixture was subjected to high-speed shear dispersion for 1 hour to prepare a magnetic coating solution. The obtained coating solution was applied onto the heat-set biaxially oriented film having a thickness of 13 μm described above so that the film thickness after drying was 3.5 μm. Then, after orientation treatment in direct current magnetism, it was dried at 100 ° C. After drying, calendering is applied and slit to 1/2 inch width, thickness 16.5
A magnetic tape of μm was obtained.

The magnetic tapes obtained here are Comparative Examples 3 and 5.
Except for, the running friction coefficient was about 0.15 to 0.22 μk, and the center line average roughness (Ra) was about 14 to 18 nm. still,
In Comparative Examples 3 and 5, the running friction coefficient was very high and running failure occurred, so that the subsequent evaluation was not performed. The characteristics of this magnetic tape are shown in Tables 1 and 2.

[0052]

[Table 1]

[0053]

[Table 2]

As is clear from the results of Tables 1 and 2, when the plate-shaped alumina hydrate fine particles were used, a polyester film useful as a base film for a magnetic recording medium and excellent in running property and abrasion resistance was obtained. can get.

[0055]

According to the present invention, it is possible to provide a polyester film which is excellent in running property and abrasion 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 unwind reel 2 tension controller 3 tension detector (entrance) 7 fixed rod 10 tension detector (exit) 13 take-up reel

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[Procedure amendment]

[Submission date] June 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The alumina fine particles that have been conventionally used are calcined alumina fine particles . In contrast, although particles of the present invention is alumina hydrate is not firing (aluminum hydroxide) particles, was also heat treated if hydrate
May be Therefore, the hardness of the powder is soft, and the projections formed on the film surface are also soft, which has the advantage of being difficult to scrape.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G11B 5/704 7215-5D H01F 1/28 // B29K 67:00

Claims (2)

[Claims] 1. A plate-shaped alumina hydrate fine particle having an aspect ratio of particles in the range of 3 to 10 and an average particle size in the range of 0.1 to 3 μm, relative to polyester.
A polyester film containing 5 to 2% by weight. 2. The polyester film according to claim 1, which is a film for a magnetic recording medium.