JPH0670147B2 - Biaxially oriented polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a biaxially oriented polyester film, and more specifically, it is made of a polyester containing lubricant fine particles that have been plasma-treated in a high oxygen concentration atmosphere, The present invention relates to a biaxially oriented polyester film which has excellent abrasion resistance, slipperiness, and scratch resistance.

<Prior Art> Polyester film represented by polyethylene terephthalate film is used for a wide range of applications because of its excellent physical and chemical properties, for example, for magnetic tapes, capacitors, photography, packaging, OHP, etc. Is used for.

In a polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and the processing process in each application, and further the quality of the product. If these are insufficient, for example, when a magnetic layer is applied to the polyester film surface and is used as a magnetic tape, the friction between the coating roll and the film surface during the application of the magnetic layer is severe, and the abrasion of the film surface due to this is also severe, In extreme cases, wrinkles and scratches on the film surface occur. In addition, even after slitting the film after coating the magnetic layer and processing it into audio, video or computer tape, etc., when pulling out from the reel or cassette, winding up and other operations, many guide parts, playback heads etc. In the meantime, abrasion occurs remarkably, scratches and distortions are generated, and white powder-like substances are deposited due to abrasion of the polyester film surface and the like, which often becomes a major cause of loss of magnetic recording signals, that is, dropout.

Generally, in order to improve the slipperiness of the film, a method of reducing the contact area with the guide roll or the like by giving unevenness to the film surface is adopted, and it is roughly classified into (i)
The method of precipitating inactive fine particles from the catalyst residue of the polymer used for the film raw material and (ii) the method of adding inactive fine particles are used. Generally, the larger the size of the fine particles in the raw material polymer, the greater the effect of improving the slipperiness. However, for precision applications such as magnetic tapes, particularly for video, the particles are large. Since the fact itself may cause a defect such as dropout, the unevenness of the film surface needs to be as fine as possible, and at present, there is a demand to satisfy these contradictory characteristics at the same time.

A film made of polyester containing the above-mentioned inactive fine particles is usually biaxially stretched to cause peeling at the boundary between the fine particles and the polyester, and voids are formed around the fine particles. The larger the particles, the more voids
The spherical shape is larger than the plate shape, the fine particles are less likely to be deformed as a single particle, and the stretching area ratio in stretching the unstretched film is large, and the temperature is low. As the voids become larger, the shape of the protrusions becomes gentler to increase the coefficient of friction, and particles are removed even by small scratches (scratches) on the voids of the biaxially oriented polyester film produced during repeated use. Occurs, which reduces durability and causes shavings. It has been well practiced to add one or more kinds (combination of large particles and small particles) of calcium carbonate, titanium oxide, kaolin and the like as the inert fine particles (Japanese Patent Laid-Open No. 51-34272, JP-A-51-34272, JP-A-52-78953, JP-A-SHO
52-78954, JP-A-53-41355, JP-A-53-71154, etc.)
However, since these fine particles form large voids, the above-mentioned problems are inherent, and improvement thereof is also desired. In addition, the deposited particles (for example, polyester oligomer metal salt) deposited during the production of polyester have small voids,
It has good sharpness, but has drawbacks such as poor running properties and scratch resistance.

<Purpose of the Invention> The present inventor has solved these inconveniences, the voids around the lubricant fine particles are small, and the film surface is appropriately roughened to improve the slipperiness and abrasion resistance of the film, and is suitable for each application. As a result of intensive studies to obtain a biaxially oriented polyester film having a surface, the present invention has been achieved.

Therefore, an object of the present invention is to provide a biaxially oriented polyester film having small voids and excellent in slipperiness, abrasion resistance and scratch resistance.

<Structure / Effect of Invention> According to the present invention, the present invention is characterized by comprising 0.005 to 3% by weight of fine particles subjected to plasma treatment in an atmosphere having an oxygen concentration of 50% or more. And a biaxially oriented polyester film.

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, as the polyester, for example, those having alkylene terephthalate and / or alkylene naphthalate as a main constituent component are preferably used.

Among such polyesters, for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, of course, for example, 80 mol% or more of the total acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and the total glycol component is A copolymer in which 80 mol% or more is ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid, etc .;
Also, up to 20 mol% of the total glycol component can be the above glycols other than ethylene glycol, or, for example, hydroquinone, resorcin, 2,2-bis (4
-Aromatic diols such as hydroxyphenyl) propane; Aliphatic diols containing an aromatic ring such as 1,4-dihydroxymethylbenzene; Polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol (polyoxyalkylene glycol) ) And so on.

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

Further, in the polyester of the present invention, a polycarboxylic acid or polyhydroxy compound having a functionality of 3 or more, such as trimellitic acid, penta A copolymer of erythritol and the like is also included.

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

As the above polyester, the intrinsic viscosity obtained by measuring at 35 ° C. as a solution in O-chlorophenol is about 0.4 to about
0.9 is preferable.

The biaxially oriented polyester film of the present invention has a large number of fine projections on the surface of the film. The numerous fine projections are derived from the inorganic or organic fine particles additionally contained in the film. The fine particles have an average particle diameter of 0.05 to 4 μm, and further 0.1 to 3 μm.
m, particularly preferably 0.1 to 2 μm. If this average particle size is too small, the efficiency of improving the slipperiness and scratch resistance is insufficient, and if it is too large, the film surface becomes too rough, which is not preferable.

In the present invention, the content of the lubricant fine particles added needs to be 0.005 to 3% by weight based on the polyester. It is preferably 0.01 to 1.0% by weight, and more preferably 0.05.
~ 0.5% by weight. If the added content is less than 0.005% by weight, the effect of improving slipperiness and abrasion resistance is insufficient, while if it exceeds 3% by weight, the film is frequently cut during the manufacturing process, which is not preferable.

In the present invention, the above-mentioned fine particles are preferably silicon dioxide (including hydrates, diatomaceous earth, silica sand, quartz, etc.), alumina; silicates containing 30% by weight or more of SiO ₂ (for example, Amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), asbestos, zircon, fly ash, etc., oxides of Mg, Zn, Zr, and Ti; Ca, and Ba Sulfates; Li, Na, and Ca phosphates (including monohydrogen and dihydrogen salts); Li, Na, and K benzoates; Ca, Ba, Zn, and Mn terephthalates; Mg , Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, and Ni titanates; Ba and Pb chromates; Carbon (eg carbon black, graphite, etc.); Glass (eg glass powder) , Glass beads, etc.); Ca, and Mg carbonates; fluorspars; and ZnS. More preferably, silicic acid anhydride, hydrous silicic acid, aluminum oxide, aluminum silicate (including calcined products, hydrates, etc.),
1 lithium phosphate, 3 lithium phosphate, sodium phosphate, barium phosphate, titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay etc.), Examples are talc, diatomaceous earth, calcium carbonate and the like.

As other fine particles, crosslinked organic particles such as crosslinked polystyrene particles and crosslinked acrylic particles are preferably exemplified. As components constituting these crosslinked organic particles, unsaturated nonionic monomers such as (meth) acrylic acid, (meth) acrylic acid ester (eg, methyl methacrylate, butyl acrylate, etc.), unsaturated compounds such as maleic acid dialkyl ester, etc. Dicarboxylic acid ester, unsaturated vinyl compound such as styrene, unsaturated nitrile compound such as acrylonitrile, functional monomer such as unsaturated carboxylic acid, monomer having hydroxyl such as hydroxyethylmethacrylate, epoxide group such as glycidylmethacrylate Examples thereof include monomers and unsaturated sulfonic acids.

In the present invention, the above-mentioned fine particles need to be plasma-treated in an atmosphere having an oxygen concentration of 50% or more before being added to the polyester. Here, the plasma treatment is a treatment with plasma generated in the vicinity of the electrode to which a high voltage is applied. Plasma is a state in which molecules or atoms are dissociated into a gas containing neutral atoms and cations and a number of anions or electrons approximately balanced with the cations. And as an external condition that causes such a state,
A so-called low temperature plasma is used, which uses a method other than a temperature of several thousands to several tens of thousands.

As a power source for generating such low temperature plasma, there are well-known high frequency wave, microwave, direct current, alternating current, etc., and discharge methods include glow discharge, corona discharge and the like.

It is desirable to stir the lubricant fine particles in order to uniformly treat the lubricant fine particles with the plasma.

As the plasma gas, use a reactive or non-reactive gas such as air, oxygen, hydrogen, ammonia, carbon dioxide, carbon tetrafluoride, nitrogen, argon, helium, or a mixture of two or more of these gases. You can However, the purpose of the plasma treatment in the present invention is to impart polar groups to the surface of the fine particles by oxidation, and therefore it is necessary to perform the plasma treatment in an atmosphere having an increased oxygen concentration. The oxygen concentration is 50% or higher, preferably 75% or higher, more preferably 90% or higher. The higher the oxygen concentration, the more effectively the polar groups due to oxidation can be attached to the surface of various fine particles.

In plasma processing, the degree of vacuum in the processing device is 0.01 to 10 mmHg when processing at low pressure, and further 0.05 to 5 mmHg,
It is particularly preferably 0.1 to 2 mmHg. When the treatment is carried out at normal pressure, the treatment gas may be brought into contact with the fine particles to be treated.

It is preferable to appropriately select the treatment time depending on the type of plasma gas, the output of plasma, the type of fine particles, and the like.

The polyester containing the plasma-treated fine particles is generally used at any time during the reaction for forming the polyester, for example, during the transesterification reaction or the polycondensation reaction in the case of the transesterification method, or in the direct polymerization method. It can be produced by adding the above-mentioned fine particles (preferably as a slurry in glycol) to the reaction system during the period. Preferably, the fine particles are added to the reaction system at the initial stage of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

The biaxially oriented polyester film in the present invention is not particularly limited by the production method, but usually melts polyester containing a predetermined proportion of fine particles, extrudes it into a sheet form from a slit die, and solidifies by cooling with a casting drum. Manufactured by subjecting the unstretched sheet to a non-stretched sheet, then stretching the unstretched sheet biaxially to form a product (film), and further subjecting it to heat treatment (heat set) and lateral heat shrinkage rate adjustment treatment. To be done. At that time, for example, the stretching temperature is the first stage stretching temperature (for example, the longitudinal stretching temperature: T ₁ ) in the range of (Tg−10) to (Tg + 45) ° C. (where Tg: the glass transition temperature of polyester), and the second stage. The stretching temperature (for example, the transverse stretching temperature: T ₂ ) is set in the range of (T ₁ +15) to (T ₁ +40) ° C., and the stretching ratio is 2.5 to 6.0 times in the first stage stretching, particularly 3.
5 to 5.5 times, 2.5 to 4.0 times in the second stage stretching, especially 2.8 to
It is preferably 3.7 times. Further obtained biaxially stretched film is preferably 150 ~ 245 ℃, more preferably 170
Heat set at a temperature in the range of ~ 240 ° C for about 1 to 200 seconds. Further, the heat treatment conditions in a normal tenter may be adjusted to adjust the heat shrinkage ratio in the lateral direction, and then the longitudinal relaxation treatment may be performed.

The biaxially oriented polyester film of the present invention is characterized in that voids around the fine particles are small. It is considered that this is because the affinity of the lubricant fine particles for polyester was increased by the plasma treatment.
When expressing this affinity by a void ratio, it usually depends on the kind of the lubricant, but the void ratio in the case of the fine particles subjected to plasma treatment is 0.1 or more, further 0.2 or more, in particular, compared with the case of the fine particles not subjected to the plasma treatment. It has been improved by 0.3 or more and has become smaller. The void ratio of the biaxially oriented polyester film varies depending on the type of fine particles, the condition of plasma treatment, the condition of stretching treatment, etc., but is 1.7 or less, more preferably 1.5 or less,
It is particularly preferably 1.3 or less. The smaller the void ratio, the better the abrasion resistance and scratch resistance. The biaxially oriented polyester preferably has a friction coefficient of 0.4 or less.

The biaxially oriented polyester film of the present invention has excellent sliding properties and abrasion resistance, and is characterized in that the amount of cuts, white powder, etc., is extremely small. This biaxially oriented polyester film can be widely used for various purposes by utilizing these characteristics. For example, when used as a base film for magnetic recording such as video, audio, and computer, excellent electromagnetic conversion characteristics, slipperiness, running durability, etc. can be obtained. In addition, when used for capacitors, low friction coefficient, excellent winding property, low crush load, high transparency, etc. can be obtained. As described above, this biaxially oriented polyester film is preferably used for the base film of the magnetic recording medium, especially for the base film of the magnetic tape, but is not limited to this, and it can be used for electrical applications,
It can be widely applied to other fields such as packaging and vapor deposition films. The film may be subjected to surface treatment such as easy adhesion layer coating or corona treatment on one side or both sides. Further, the film may contain a third component such as an antistatic agent, an ultraviolet absorber and a coloring agent.

<Examples> Hereinafter, the present invention will be further described with reference to Examples. Various physical properties and characteristics in the present invention are measured as follows.

(1) Average particle size of fine particles (DP) Measured using a CP-50 type Centrifugal Particle Size Analyzer (Centrifugal Particle Size Analyzer) manufactured by Shimadzu Corporation. 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 its abundance, and this value is taken as the above average particle diameter (Book Technology ”Published by Nikkan Kogyo Shimbun, 1975,
See pages 242-247).

(2) Void ratio A sample film piece is fixed on a sample stand for a scanning electron microscope, and a sputtering device (JFC-1100 manufactured by JEOL Ltd.) is used.
Type ion sputtering apparatus), the film surface is subjected to ion etching treatment under the following conditions. As for the conditions, the sample is set in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-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. Further, gold spatter is applied to the film surface with the same device, and the film is observed with a scanning electron microscope at, for example, 10000 to 30000 times, and is manufactured by Nippon Regulator Co., Ltd.
Measure the major axis of at least 50 particles and the major axis of voids with Luzex 500 manufactured by It is expressed by the number average value of the Houd ratio calculated in.

(3) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra), and in the present invention, a stylus type surface roughness meter (SURFCORDER SE of Kosaka Laboratory Ltd.) -30C). The measurement conditions are as follows.

(A) Stylus tip radius: 2 μm (b) Measuring pressure: 30 mg (c) Cut-off: 0.25 mm (d) Measuring length: 0.5 mm (e) How to put together the data Value 1
Except for one, the average value of the remaining four data is rounded off to the fourth decimal place and displayed up to the third decimal place.

(4) Coefficient of friction (μk) A film cut into a width of 1/2 inch in an environment of temperature 20 ° C and humidity 60% is attached to a fixed rod (surface roughness 0.3 μm) at an angle θ = (1
52/180) π radian (152 °) contact and move (rub) 10 m at a speed of 200 mm per second. Entrance tension T ₁ is 3
The exit tension (T ₂ : g) when the tension controller is adjusted to be 5 g is detected by the exit tension detector after repeating the above movement 200 times, and the traveling friction coefficient μk is calculated by the following formula.

μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35) (5) of the running surface of the scraping of the scraping of the film is evaluated using a 5-stage mini-super calendar. The calender is a 5-stage calender consisting of nylon roll and steel roll, and the processing temperature is
The film is run at 80 ° C, the linear pressure applied to the film is 200 kg / cm, and the film speed is 50 m / min. Running film length is 2000m
The dirt attached to the top roller of the calendar at the time of running is used to evaluate the sharpness of the film according to the following four grades.

◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled × Nylon roll is soiled × × Nylon roll is heavily soiled (6) Scratch resistance A film cut into 1/2 inch width is measured for friction coefficient in (4) above Using the device, the film surface is in contact with the fixed rod at an angle of 152 °, and it is run for 10 m at a speed of 20 cm / sec,
After repeating this 50 times, the thickness, depth, and number of scratches on the surface of the film are comprehensively evaluated in the following 5 steps.

◎ No scratches are found on 1/2 inch width film. ○ Most scratches are not found on 1/2 inch width film. △ Scratches are found on 1/2 inch width film (some) × 1 Some thick scratches are found on a 1/2 inch wide film XX A large number of thick and deep scratches are found on a 1/2 inch wide film (7) Pin scraping conditions, contents described in (4) above After measuring the friction coefficient (μk) of the film, the abrasion resistance of the base film is evaluated by the following four grades due to the dirt attached to the fixing rod (pin).

◎ No dirt on the fixing rod (pin) ○ Almost no dirt on the fixing rod (pin) △ Dirty fixing rod (pin) × Severe dirt on the fixing rod (pin) (8) Dropout Commercial dropout counter (eg Shibasoku VH01
The BZ type) is used to count the dropout of 5 μsec × 10 dB and calculate the count number per minute.

(9) Electromagnetic conversion characteristics (chroma S / N) Using a commercially available VTR for home use, 50% white level signal (100% white level signal is peak: two: peak voltage is 0.714 volt), 100% chroma A signal on which a level signal is superimposed is recorded, and the reproduced signal is recorded as a shiba sox oximeter Type
Measure with 925R. The definition of chroma S / N is as follows according to the definition of Shibasoku.

Here, ES (pp) is the peak of the reproduced signal of the white level signal:
Two: The peak voltage difference (pp).

ES (pp) = 0.714V (pp) EN (rms) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

EN (rms) = AM noise effective value voltage (V) Comparative Examples 1 to 6 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and Fine particles shown in Table 1 were added as a lubricant and polymerized by a conventional method to obtain an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.62
Of polyethylene terephthalate was obtained.

The polyethylene terephthalate pellets were dried at 170 ° C for 3 hours and then fed to the extruder hopper to melt at a temperature of 280-3.
It was melted at 00 ° C., and this molten polymer was formed and extruded through a 1 mm slit die on a rotary cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain an unstretched film of 200 μm.

The unstretched film obtained in this way is preheated at 75 ° C, and further between the low speed and high speed rolls at 15 ° C above 900 ° C.
Was heated with one 1R heater having a surface temperature of 3 to draw up to 3.6 times, quenched, and then supplied to a stenter, and then drawn at 3.7 times in the transverse direction at 105 ° C. The resulting biaxially oriented film is 2
Heat setting was performed for 5 seconds at a temperature of 05 ° C. to obtain a heat setting biaxially oriented film having a thickness of 15 μm.

The characteristics of this film are shown in Table 1.

Examples 1 to 22 Lubricants of the types shown in Table 2 were treated at a frequency of 13.56 MHz and a microwave power of 200 W under a high oxygen concentration while being stirred using a plasma treatment device (manufactured by Toshiba Corp.).

Comparative Examples 1 to 6 except that the obtained plasma-treated lubricant was used
A biaxially oriented polyester film was obtained in the same manner as above.

The properties of these films are shown in Table 2. These films are superior in abrasion resistance, running property and scratch resistance as compared with Comparative Examples 1-6.

Also, the film characteristics are superior under the high oxygen concentration condition.

Comparative Examples 7 and 8 and Examples 23 and 24 Films obtained in Comparative Examples 5 and 3, and Example 11
Based on each of the films obtained in 1 and 19, 100 parts by weight of iron oxide powder having the following composition Co on the film S-REC A (Sekisui Chemical's vinyl chloride-vinyl acetate copolymer) 10 〃 Nipolan 2304 Elastomer) 10〃 Coronate L (Polyisocyanate made by Nippon Polyurethane) 5〃 Lecithin 1〃 Methyl ethyl ketone 75〃 Methyl isobutyl ketone 75〃 Toluene 75〃 Magnetic powder paint with 0.15〃 additive (quasi-lubricant) is applied by gravure roll Then, the magnetic paint layer was smoothed with a doctor knife, magnetically oriented by a conventional method while the magnetic paint was still dry, and then introduced into an oven for dry curing. Approximately 5 slits by calendering
A 1 / 2-inch wide magnetic tape having a μm magnetic layer was prepared. The characteristics of this magnetic tape are shown in Table 3.

The magnetic tapes obtained in Examples 23 and 24 were scraped due to the excellent abrasion resistance and scratch resistance of the base film, and scratches were not observed. Therefore, the dropout (D / O) generated from the abrasion of the tape was small and good. In addition, the electromagnetic conversion characteristics are kept at a good level.

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Claims (2)

[Claims] 1. A biaxially oriented polyester film comprising a polyester containing 0.005 to 3% by weight of fine particles subjected to plasma treatment in an atmosphere having an oxygen concentration of 50% or more. 2. The biaxially oriented polyester film according to claim 1, wherein the fine particles have an average particle diameter of 0.05 to 4 μm.