JPH07119293B2 - Biaxially oriented polyester film - Google Patents

Description

The present invention relates to a biaxially oriented polyester film, and more specifically, it has a specific surface area (BET method) of 70 m ² / g as an effective lubricant component.
Contains the above spherical porous silica fine particles and is flat and slips,
The present invention also relates to a biaxially oriented polyester film having excellent abrasion resistance.

[Prior Art] Polyester typified by polyethylene terephthalate is widely used as a film for magnetic tape, photography, capacitors, packaging, etc. because of its excellent physical and chemical properties. In these films, the slidability and abrasion resistance are major factors that affect the workability of the film manufacturing process and the working process in each application, and further the quality of the product. In particular, when the magnetic layer is applied to the polyester film surface, friction and abrasion between the coating roll and the film surface are extremely large, and wrinkles and scratches are likely to occur on the film surface. In addition, even after slitting the film after coating the magnetic layer and processing it into audio, video or computer tapes, many guide parts, such as reels, cassettes, etc.
Abrasion occurs remarkably between the reproducing head and the like, scratches and distortion are generated, and white powder-like substances are deposited due to abrasion of the polyester film surface, resulting in loss of magnetic recording signals.
That is, it is often a major cause of dropout.

Generally, in order to improve the slipperiness and abrasion resistance of a film, a method of reducing the contact area with a guide roll or the like by giving unevenness to the film surface is adopted, and it is roughly classified into (i) film raw material. The method of precipitating inactive fine particles from the catalyst residue of the polymer used and (ii) the method of adding inactive fine particles are used. Generally, the larger the size of the inert fine particles in these raw material polyesters, the greater the effect of improving the slipperiness, but for precision applications such as magnetic tapes, especially for video,
Since the fact that the particles are large can cause defects such as dropouts, the unevenness of the film surface needs to be as fine as possible, and there is a demand for satisfying contradictory properties at the same time. Is.

[Object of the Invention] An object of the present invention is to provide a biaxially oriented polyester film having excellent surface flatness, slipperiness, and abrasion resistance.

An object of the present invention is to provide a biaxially oriented polyester film having a large number of fine projections formed by spherical porous silica fine particles on the surface of the film and having excellent surface flatness, slipperiness and abrasion resistance. .

Further objects and advantages of the present invention will be apparent from the following description.

[Structure / Effects of the Invention] According to the present invention, the above objects and advantages of the present invention are defined by (1) an aromatic polyester, and (2) (a) a ratio of a maximum diameter to a minimum diameter. Particle size ratio
1.0 to 1.2, (b) an average particle diameter of 0.01 to 4 μm, and (c) a BET specific surface area of 70 m ² / g or more Spherical porous silica fine particles 0.005 to 4 wt% (aromatic polyester In contrast, a biaxially oriented polyester film obtained by molding an intimate mixture of

The aromatic 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-forming properties by melt molding. Aromatic dicarboxylic acids include, for example, terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid,
Examples thereof include diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid and anthracene dicarboxylic acid. The aliphatic glycol is, for example, an alkylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, or an alicyclic diol such as cyclohexanedimethanol. Etc.

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

Among such polyesters, for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, of course, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and total glycol. A copolymer in which 80 mol% or more of the component is ethylene glycol is particularly preferable.

At that time, 20 mol% or less of the total acid component of the dicarboxylic acid may be the above aromatic dicarboxylic acid other than terephthalic acid or 2,6-naphthalenedicarboxylic acid, and may be an aliphatic dicarboxylic acid such as adipic acid or sebacic acid. Dicarboxylic acids; can be alicyclic dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid and the like. Further, 20 mol% or less of the total glycol component may be the above glycol other than ethylene glycol, or an aromatic diol such as hydroquinone, resorcin, 2,2'-bis (4-hydroxyphenyl) propane; It is also possible to use an aliphatic diol having an aromatic ring such as 4,4-dihydroxymethylbenzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

In the aromatic polyester used in 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. Those containing 20 mol% or less based on the total amount of the carboxylic acid component are also included. Further, the aromatic polyester in the present invention has a substantially linear amount, for example, an amount of 2 mol% or less with respect to the total acid component, of a trifunctional or higher polycarboxylic acid or polyhydroxy compound, such as trimellitate. It also includes a copolymer of acid, pentaerythritol and the like.

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

The aromatic polyester has an intrinsic viscosity of about 0, measured at 35 ° C. as a solution in o-chlorophenol.
Those of 4 to about 1.0 are preferred.

The biaxially oriented polyester film of the present invention has a large number of fine projections on the surface of the film.

According to the present invention, these numerous fine protrusions are derived from the numerous spherical porous silica fine particles contained in the aromatic polyester in a dispersed state.

The spherical porous silica fine particles in the present invention are characterized by having characteristics such as (a) a spherical shape close to a true sphere, (b) a small particle diameter, and (c) a large specific surface area, and further, these characteristics and (d) Characterized by having the property of a narrow particle size distribution.

That is, the spherical porous silica fine particles have (a) a particle size ratio defined by the ratio of the maximum diameter and the minimum diameter in the range of 1.0 to 1.2,
(B) The average particle size is 0.01 to 4 μm, and (c) the specific surface area (BET method) is 70 m ² / g or more. The particle size ratio is preferably in the range of 1.0 to 1.15,
It is particularly preferably in the range of 1.0-1.12. The average particle size is preferably in the range of 0.05 to 2 μm, particularly preferably in the range of 0.01 to 1 μm.

Furthermore, the spherical porous silica fine particles have a relative standard deviation (σ) of particle diameters defined by the following formula (A). Is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.12 or less. Here, the area circle equivalent diameter means a diameter when each particle is converted into a true sphere. When the above relative standard deviation (σ) is 0.5 or less, the spherical porous silica fine particles have an extremely sharp particle size distribution, and the spherical surface which is close to a true sphere has an extremely uniform height on the film surface and Gives a sharp projection.

For this reason, the same number of protrusions as the conventional film has a non-uniform height, and the same number of protrusions gives a film having extremely good slipperiness.

Further, the specific surface area is as large as 70 m ² / g or more, the area is extremely active, and various surface modification treatments can be performed, so that the adhesiveness with polyester can be further improved.

The spherical porous silica particles are not limited to any production method or other characteristics as long as they satisfy the above characteristics.

For example, from a composition in which the zeolite silica component and the alumina component are in the zeolite formation range, zeolite (Na ₂ O ・ 2SiO _2
2・ Al ₂ O ₃・ nH ₂ O) crystals are precipitated, and the alumina component is eluted and removed by acid treatment of this zeolite.
Spherical porous silica can be obtained. The acid used here is not particularly limited and may be an inorganic acid or an organic acid, but nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or the like can be preferably used.

The spherical porous silica fine particles may have any shape as long as they are finally spherical in terms of preparation, and the starting material zeolite may be spherical or adjusted to be spherical after acid treatment.

The spherical porous silica fine particles in the present invention, as described above, each shape is a sphere which is extremely close to a true sphere and has a large specific surface area of 70 m ² / g or more, which is conventionally known as a lubricant. there and porous silica bulk is indefinite shape a 200 meters ² / g approximately, aerosols, colloidal silica, the surface smooth silica particles of about 10 to 40 m ² / g even specific surface area a spherical It is characterized by a marked difference.

The intimate mixture of the aromatic polyester forming the film of the present invention and the spherical porous silica fine particles has a fine particle size of 0.
It contains 005 to 4.0% by weight (based on the aromatic polyester). If the amount of the fine particles is less than 0.005% by weight, the effect of improving the slipperiness and abrasion resistance of the film is insufficient.
If it exceeds 4.0% by weight, the flatness of the film is deteriorated. The amount of the fine particles is preferably 0.01 to 2.0% by weight (based on the aromatic polyester).

A polyester film containing such spherical porous silica fine particles is characterized by having uniform uneven surface characteristics, excellent slipperiness and abrasion resistance, and having a significantly small amount of scratches and white powder. The reason why this characteristic, particularly the excellent slipperiness and abrasion resistance is exhibited, has not been fully clarified yet.

As described above, since the spherical porous silica fine particles have excellent characteristics, according to the present invention, by using together with other inert fine particles, there is an advantage of using two or more kinds of fine particles, and the running property is improved. It has become clear that a film excellent in abrasion resistance, fatigue resistance, electric insulation and transparency can be provided.

That is, the biaxially oriented polyester film has a particle size ratio defined by (1) aromatic polyester, (2) (a) ratio of maximum diameter to minimum diameter.
1.0 to 1.2, (b) an average particle diameter of 0.01 to 4 μm, and (c) a BET specific surface area of 70 m ² / g or more Spherical porous silica fine particles 0.005 to 4 wt% (aromatic polyester (3) and (3) 0.005 inactive particles having an average particle size of 0.01 to 4 μm
It is a biaxially oriented polyester film obtained by molding an intimate mixture of about 4% by weight (based on the aromatic polyester).

The aromatic polyester (1) and the spherical porous silica fine particles (2) are as described above.

As the above-mentioned inert fine particles (3), those which are substantially inactive and insoluble in the aromatic polyester and which are fixed at room temperature are used. These may be externally added particles (A) or internally generated particles (B). Further, for example, it may be a metal salt of an organic acid or an inorganic substance. As preferable externally added inert particles (A), calcium carbonate, silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.),
Alumina, silicate containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline clay minerals, aluminosilicate compounds (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.) Oxides of Mg, Zn, Zr, and Ti, sulfates of Ca and Ba, phosphates of Li, Na, and Ca (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 chromium Acid salts, carbon (eg carbon black, graphite, etc.), glass (eg glass powder, glass beads, etc.), MgCO ₂ , fluorspar,
And ZnS are exemplified. Particularly preferred is
Calcium carbonate, silicic acid anhydride, hydrous silicic acid, aluminum oxide, aluminum silicate (including calcined products, hydrates, etc.), 1 lithium phosphate, 3 lithium phosphate, sodium phosphate, calcium phosphate, barium sulfate, titanium oxide, benzoin Examples thereof include lithium acid, double salts (including hydrates) of these compounds, glass powder, clay (including kaolin, bentonite, and clay), talc, diatomaceous earth, and the like.

Further, the internal component particles (B) are generated and precipitated from a catalyst residue or the like during the production of polyester and are contained in the polymer. For this dispersion and inclusion, a conventionally known method for forming internal precipitated particles should be used. You can For example, Japanese Patent Laid-Open Nos. 48-61556, 51-112860, and 5
1-115803, JP-A-53-41355, JP-A-54-
The method disclosed in Japanese Patent No. 90397 can be used. The internally deposited particles are preferably formed between the stage when the monomer formation reaction is substantially completed and the initial stage of the polycondensation reaction. Preferred examples of the catalyst used in the monomer formation reaction and the compound added in this reaction stage include calcium compounds and lithium compounds. Further, examples of components that form the calcium compound and the lithium compound include aliphatic carboxylic acids such as acetic acid, propionic acid and butyric acid; aromatic carboxylic acids such as benzoic acid, p-methylbenzoic acid and naphthoic acid; methyl. Examples thereof include alcohols such as alcohol, ethyl alcohol, propyl alcohol and butyl alcohol; glycols such as ethylene glycol and propylene glycol; chlorine, hydrogen and the like. Explaining further, examples of the lithium compound include salts of the above-mentioned aliphatic carboxylic acids, salts of aromatic carboxylic acids, alcoholates, glycolates, chlorides, hydrides and the like. The formation of internally deposited particles is usually carried out by adding a phosphorus compound to the system in which the above compound is present. Examples of phosphorus compounds include phosphoric acid, phosphorous acid, and their esters (eg, alkyl esters, aryl esters, etc.). Further, other additives (for example, lithium phosphate) can be used for the generation, particle size, stabilization, etc. of the internally precipitated particles. Among the internally precipitated particles, those containing calcium, lithium and phosphorus have a relatively large particle size, and those containing lithium and phosphorus have a relatively small particle size, so that the composition can be changed depending on the desired particle size. The preferred internally deposited particles include lithium element 0.03 to 5% by weight, calcium element 0.03 to 5% by weight, and phosphorus element 0.03.
Mention may be made of particles containing ˜10% by weight.

The internally precipitated particles can be separated from the polymer, for example, by the method described below, and the particle size, amount, etc. can be determined.

[Particle Separation Method] Polyester or polyester film is thoroughly washed with methanol to remove surface deposits, washed with water and dried.
500 g of the film was sampled and o-chlorophenol was added to it.
4.5 Kg was added and the temperature was raised to 100 ° C. with stirring, and after the temperature was raised, it was left as it was for 1 hour to dissolve the polyester part. However, in the case where the polyester portion is not dissolved due to a high degree of crystallization, the above melting operation is performed after melting once and quenching.

Then, in order to remove coarse insoluble matters other than internal particles such as dust contained in the polyester or reinforcing agents added, the dissolved solution is separated by a C-1 glass filter, and this weight is subtracted from the sample weight.

Equipped with Hitachi's separation ultracentrifuge 40P type rotor RP30, the solution after separating the glass filter per cell
After injecting 30 cc, rotate the rotor at 4500 rpm, confirm that there is no abnormal rotation, then evacuate the inside of the rotor to 3000
The rotation speed is increased to 0 rpm, and the particles are centrifuged at this rotation speed.

The separation is completed after about 40 minutes, but if necessary, this confirmation is carried out when the light transmittance at 375 mμ of the liquid after the separation becomes a constant value higher than that before the separation. After separation
The supernatant is removed by a gradient method to obtain separated particles.

The separated particles may have a polyester content due to insufficient separation.
-Add chlorophenol and suspend almost uniformly, then repeat the ultracentrifuge treatment. This operation needs to be repeated until the particles to be described later are dried and then the particles are subjected to scanning differential calorimetric analysis until the melting peak corresponding to the polymer cannot be detected. Finally, the separated particles thus obtained were treated at 120 ° C, 16 ° C.
Vacuum dry for an hour and weigh.

The separated particles obtained by the above operation include both internally precipitated particles and spherical porous silica particles. Therefore, it is necessary to separately determine the amount of internal particles and the amount of spherical porous silica particles, and first perform a quantitative analysis of the metal content of the separated particles.
The contents of Ca and Li and the contents of metals other than Ca and Li are obtained. Then, the separated particles are heated under reflux in a 3-fold molar amount of ethylene glycol for 6 hours or more, and then ethylene glycol is distilled off at 200 ° C. or more to depolymerize, whereby only the internal particles are dissolved. Separated particles obtained by centrifuging the remaining particles are dried and weighed to obtain the amount of external particles, and the difference from the initial total amount of separated particles is taken as the amount of internally precipitated particles.

The internally precipitated particles may contain a trace amount of other metal components, such as zinc, manganese, magnesium, cobalt, or antimony, germanium, titanium, etc., as long as the effect of the present invention is not impaired.

In the present invention, particles having the same composition as the above internally precipitated particles may be separately produced and added to the aromatic polyester. These particles can be called externally added precipitated particles (C), and can be used in combination with spherical porous silica fine particles. The particle size, amount, etc. of the particles in the polymer can be determined in the same manner as in the case of the internally precipitated particles.

The average particle size of the inert fine particles (3) is in the range of 0.01 to 4 μm, preferably 0.05 to 3 μm, and particularly preferably 0.1 to 2 μm.

In the present invention, when the spherical porous silica fine particles (2) and the inert fine particles (3) are used in combination, the content of the spherical porous silica fine particles is 0.005 relative to the aromatic polyester (1).
-4% by weight, preferably 0.01-2% by weight, more preferably 0.04-1% by weight, particularly preferably 0.1-0.5% by weight. On the other hand, the content of the inert fine particles (3) is 0.005 to 4% by weight, preferably 0.01 to 2% by weight, more preferably 0.01 to 1% by weight, and particularly preferably, the content of the aromatic polyester.
It is 0.05 to 0.5% by weight.

If the content of spherical porous silica fine particles or inert fine particles is too small, the synergistic effect of using two kinds of particles, large and small, will not be obtained, and the running properties, wear resistance, fatigue resistance, crushing property, end face uniformity, etc. It is not preferable because the characteristics are deteriorated. On the other hand, if the content of the spherical porous silica fine particles or the inert fine particles is too large, the film surface becomes too rough and, for example, the electromagnetic conversion characteristics of the magnetic tape are deteriorated, which is not preferable.

In producing the biaxially oriented film of the present invention, in order to intimately mix the spherical porous silica fine particles, or the inert fine particles with the aromatic polyester, these fine particles are used.
The aromatic polyester may be sufficiently kneaded with the aromatic polyester in a polymerization vessel before or during the polymerization, in an extruder when pelletizing after the completion of the polymerization, or in an extruder when melt-extruding into a sheet. .

The polyester film of the present invention has, for example, a melting point (Tm:
C.) to (Tm + 70) C. Aromatic polyester is melt extruded at a temperature of (Tm + 70) .degree. C. to obtain an unstretched film having an intrinsic viscosity of 0.35 to 0.9 dl / g, and the unstretched film is uniaxially (longitudinal or transverse) (Tg- 10) to (Tg + 70) ° C. (where Tg: glass transition temperature of aromatic polyester) is drawn at a draw ratio of 2.5 to 5.0, and then in a direction perpendicular to the above drawing direction (when the first drawing is in the longitudinal direction). Is the second direction stretching is in the lateral direction)
It can be produced by stretching at a temperature of Tg (° C) to (Tg + 70) ° C at a draw ratio of 2.5 to 5.0 times. In this case, the area draw ratio is 9
It is preferably 22 to 22 times, more preferably 12 to 22 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching.

Further, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° 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 thickness of the polyester film is preferably 1 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 1 to 25 μm.

The polyester film of the present invention has a small coefficient of friction during running and has very good operability. Further, when this film is used as a base of a magnetic tape, the base film is scarcely scraped due to contact friction with a running portion of a magnetic recording / reproducing apparatus (hardware), and has good durability.

Due to the combination of the above advantages as a film product and the advantages at the time of film formation, the film of the present invention, in particular,
It is extremely useful as a base film for high-grade magnetic fields, and has the advantage that it can be manufactured easily and stably. The polyester film of the present invention is a high-grade magnetic recording medium such as a micro recording material, a compact or high-density floppy disk product, an ultra-thin material for long-time recording of audio and video, a high-density recording magnetic film, and high quality. It is suitable as a magnetic recording film for image recording / reproducing, for example, a base film such as metal or vapor-deposited magnetic recording material.

Therefore, according to the present invention, a magnetic recording medium provided with a magnetic layer on one side or both sides of the biaxially oriented polyester film of the present invention is also provided.

The magnetic layer and the method for providing the magnetic layer on the base film are known per se, and the known magnetic layer and the method for providing the magnetic layer can be adopted in the present invention.

The biaxially oriented polyester film of the present invention can be used in various applications other than the above magnetic recording medium. For example, it is useful for applications such as capacitors, packaging, and vapor deposition.

Various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Particle Size of Spherical Porous Silica Fine Particles The particle size can be measured in the following states.

1) When determining the average particle size, particle size ratio, etc. from the particles 2) When determining the average particle size, particle size ratio, etc. of the particles in the film 1) From the powder: Powder on the electron microscope sample stand Disperse the body so that the individual particles do not overlap as much as possible, and form a gold thin film vapor deposition layer (layer thickness 200 to 300Å) on the surface with a gold sputtering device, with a scanning electron microscope at a magnification of 10,000 to 30,000 times. Observe and use Luzex 500 manufactured by Nippon Regulator Co., Ltd. to obtain the maximum diameter (Dli) and minimum diameter (Dsi) of at least 100 particles.
And the area equivalent circle diameter (Di). Then, with the number average value expressed by the following equation, the maximum particle diameter (D
l), minimum diameter (Ds), and average particle diameter ().

2) Particles in the film: A small piece of the sample film is fixed to a sample stand for a scanning electron microscope, and a sputtering device (JFC-110 manufactured by JEOL Ltd.) is used.
The film surface is subjected to ion etching treatment under the following conditions using a 0-type ion sputtering apparatus). condition is,
The sample is placed 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. Furthermore, gold spatter is applied to the film surface with the same device, and 1 with a scanning electron microscope.
Observed at 0,000 to 30,000 times, Nippon Regulator Co., Ltd.
Determine the maximum diameter (Dli), minimum diameter (Dsi), and area equivalent circle diameter (Di) of at least 100 particles with Luzex 500. Thereafter, the same procedure as 1) above is performed.

(2) Particle size of particles other than spherical porous silica particles 1) Average particle size CP-50 type Centrifugure particle manufactured by Shimadzu
Size Analyzer (Centrifugal Particle Size An
alyser), from the integrated curve of particles of each particle size calculated based on the obtained centrifugal sedimentation curve and its abundance,
The particle size corresponding to 50 mass percent is read, and this value is taken as the above-mentioned average particle size (see Book "Particle Size Measurement Technology", Nikkan Kogyo Shimbun, 1975, pp. 242-247).

2) Particle size ratio A small piece of film is fixedly molded with epoxy resin, and an ultrathin section with a thickness of about 600Å (cut parallel to the film flow direction) is made with a microtome. The cross-sectional shape of the lubricant in the film of this sample is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.), and the ratio is expressed as the ratio of the maximum diameter to the minimum diameter of the lubricant.

3) Relative standard deviation Calculate the difference particle size distribution from the integrated curve in item 1) and calculate the relative standard deviation based on the following relative standard deviation definition formula.

Here, each particle size (μm) obtained in the item Di: 1): Average diameter (μm) obtained in the item 1) The number of divisions when the integrated curve in the item n: 1) was obtained φi: Each particle size Represents the probability of existence of particles (mass percent).

(3) Particle surface area Obtained by applying the BET adsorption theory. A constant pressure capacity method is adopted as the measuring method, N ₂ is used as an adsorbing gas, and the measurement temperature is set to −195 ° C. using a liquid nitrogen bath.

BET type Where Ps is the saturated vapor pressure of nitrogen at the measurement temperature P is the nitrogen pressure at the adsorption equilibrium V is the adsorption amount at the adsorption equilibrium Vm is the adsorption layer for the monomolecular layer K is a constant.

Using Draw a graph of the relationship with Is drawn in the range of 0.05 to 0.35, and from this intercept and the slope
Calculate Vm and K. In this case,
16.2Å ²

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

(A) Stylus tip radius: 2 μm (b) Measuring pressure: 30 mg (c) Cutoff: 0.25 mm (d) Measuring length: 2.5 mm (e) Data compilation method The same material was repeatedly measured 5 times, and the largest 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.

(5) Friction coefficient (μk) of film The film cut into 1/2 inch width at a temperature of 20 ° C and humidity of 60% is attached to a fixed rod (surface roughness 0.3 μm) at angle θ = (1
52/180) π radian (152 °) contact and move (rub) at a speed of 200 cm per minute. Entrance tension T ₁ is 35g
The exit tension (T ₂ : g) when the tension controller is adjusted so that the film travels for 90 m, is detected by the exit tension detector, and the running friction coefficient μk is calculated by the following formula.

μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35) (6) of the running surface of the scraping of the scraping of the film was 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
At 80 ° C, the linear pressure applied to the film was 200 Kg / cm, the film speed was 50 m / min, and the film was evaluated for its sharpness due to dirt adhering to the top roller of the calender when running the film for 2000 m.

<Five-step judgment> ◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled △ Nylon roll is slightly soiled × Nylon roll is heavily soiled × × Nylon roll is heavily soiled (7) Intrinsic viscosity [η] o-chloro The value is measured at 35 ° C using phenol as a solvent, and the unit is 100 cc / g.

<Examples> Hereinafter, the present invention will be described with reference to Examples.

Comparative Example 1 The presence of dimethyl terephthalate and ethylene glycol in the presence of manganese acetate (transesterification catalyst), antimony trioxide (polymerization catalyst), phosphorous acid (stabilizer) and kaolin (lubricant) with an average particle size of 0.56 μm and a particle size ratio of 10 Then, polymerization was carried out by a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62.

This polyethylene terephthalate pellet is
After drying for 3 hours, supply to the extruder hopper and melt temperature 280 ~
It was melted at 300 ° C., and this molten polymer was 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. to obtain an unstretched film of 200 μm.

The unstretched film obtained in this way is preheated at 75 ° C and then heated by a single IR heater with a surface temperature of 900 ° C from 15 mm above between low speed and high speed rolls to obtain low and high roll surface speeds. Due to the difference, the film was longitudinally stretched 3.5 times, rapidly cooled, then fed to a stenter and laterally stretched 3.7 times at 105 ° C.
The obtained biaxially stretched film was heat set at a temperature of 205 ° C. for 5 seconds to obtain a biaxially oriented film having a thickness of 15 μm.

The obtained film had good abrasion resistance, but had a large running friction coefficient and was unsatisfactory. The characteristics of this film are shown in Table 1.

Comparative Example 2 The same procedure as in Comparative Example 1 was repeated except that calcium carbonate having an average particle size of 0.72 μm and a particle size ratio of 1.4 was used instead of kaolin.
A biaxially oriented film of μm was obtained. Although this film has good runnability, white powder was generated in the calendar process. The characteristics of this film are shown in Table 1.

Comparative Examples 3 and 4 Porous silica having an average particle size of 0.65 μm and a particle size ratio of 10 instead of kaolin (Comparative Example 3), or an average particle size of 0.35 μm and a particle size ratio of 1.
A biaxially oriented film having a thickness of 15 μm was obtained in the same manner as in Comparative Example 1 except that 4 of calcium carbonate (Comparative Example 4) was used.

In Comparative Example 3, the sharpness was good, but the running friction coefficient was large, which was unsatisfactory. In Comparative Example 4, the surface was flat, but the running property was poor and white powder was generated, which was unsatisfactory. These properties are shown in Table 1.

Examples 1 to 3 Biaxially oriented films having a thickness of 15 μm were obtained in the same manner as in Comparative Example 1 except that spherical porous silica described in Table 1 was used instead of kaolin. Each of the films had a flat surface, but was excellent in running property, and had less scratches and white powder generation, which was satisfactory. These characteristics are shown in Table 1.

Comparative Example 5 A biaxially oriented film having a thickness of 15 μm was obtained in the same manner as in Comparative Example 1 except that spherical porous silica described in Table 1 was used instead of kaolin. The film had good running performance because the spherical porous silica had an excessively large particle size, but the surface was rough and the amount of white powder generated was unsatisfactory. These characteristics are shown in Table 1.

Comparative Examples 6 to 8 Biaxially oriented films having a thickness of 15 μm were obtained in the same manner as in Comparative Example 1 except that the fine particles listed in Table 2 were used instead of kaolin.

In Comparative Examples 6 to 8, the films of Comparative Examples 1 to 4 were unsatisfactory. Therefore, calcium carbonate having a small particle size was added together with kaolin having a large particle size or porous silica to improve the sharpness. Although the improvement effect was small, it was unsatisfactory. These characteristics are shown in Table 2.

Examples 4 to 6 Biaxially oriented polyester films having a thickness of 15 μm were obtained in the same manner as in Comparative Example 6 except that the fine particles shown in Table 2 were used.
Since spherical porous silica was used as small particles in these films, the running resistance was low and the generation of white powder was extremely small, which was satisfactory. These characteristics are shown in Table 2.

Example 7 Manganese acetate as a transesterification catalyst in a mixture of dimethyl terephthalate and ethylene glycol, lithium acetate and calcium acetate dissolved in ethylene glycol, and spherical porous silica having an average particle diameter of 0.54 μm uniformly dispersed in ethylene glycol. Add 0.05 wt% (relative to polyester) and carry out transesterification reaction by the usual method,
When the transesterification reaction was completed, trimethyl phosphate and antimony trioxide as a polymerization catalyst were added, and polycondensation reaction was carried out by a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62 (o-chlorophenol, 35 ° C.).

When the amount of internally precipitated particles in this polyethylene terephthalate was determined by the above-mentioned particle separation method, the internally deposited particles corresponded to the amount of spherical silica added as externally added particles. Further, when the polyethylene terephthalate was sandwiched in a preparation, dissolved, cooled and observed with a microscope, it was found that a large number of particles having an average particle size of about 0.7 μm and spherical particles of 0.54 μm were mixed. The former is internally precipitated particles precipitated in the polymer during polyester production, and the latter is spherical porous silica particles added from the outside.

Then, the polyethylene terephthalate is melt extruded from a slit at 280 to 300 ° C. and rapidly cooled, and the unstretched film is stretched at a longitudinal draw ratio of 3.5 times, a lateral draw ratio of 3.7 times, and a heat treatment temperature of 205 ° C.
The film was stretched and heat-set under the conditions described above to obtain a biaxially oriented film having a thickness of 15 μm. The characteristics of this film are shown in Table 2.

The obtained film had a small amount of white powder and was excellent in running property and was satisfactory.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location // B29K 67:00 B29L 7:00 (72) Inventor Hideo Kato 337-19 Oyama, Sagamihara City, Kanagawa Prefecture Teijin Ltd. Plastics Research Laboratory (56) References JP 62-30146 (JP, A) JP 62-53374 (JP, A)

Claims (4)

[Claims] 1. A particle size ratio defined by (1) an aromatic polyester, and (2) (a) a ratio of a maximum diameter to a minimum diameter.
1.0 to 1.2, (b) an average particle diameter of 0.01 to 4 μm, and (c) a BET specific surface area of 70 m ² / g or more Spherical porous silica fine particles 0.005 to 4 wt% (aromatic polyester A biaxially oriented polyester film obtained by molding an intimate mixture of 2. The spherical porous silica fine particles are zeolite (Na
_{2 O · 2SiO 2 · Al 2} O 3 · nH 2 O) from the acid treatment as prepared is the claims film as set forth in claim 1, wherein the. 3. The film according to claim 1, wherein the relative standard deviation represented by the following formula (4) of the spherical porous silica fine particles is 0.5 or less. Relative standard deviation = Where Di: area circle equivalent diameter of each particle (μm): average value of area circle equivalent diameter n: represents the number of particles. 4. (1) Aromatic polyester, (2) (a) The particle size ratio defined by the ratio of the maximum diameter and the minimum diameter is
1.0 to 1.2, (b) an average particle diameter of 0.01 to 4 μm, and (c) a BET specific surface area of 70 m ² / g or more Spherical porous silica fine particles 0.005 to 4 wt% (aromatic polyester (3) and (3) 0.005 inactive particles having an average particle size of 0.01 to 4 μm
A biaxially oriented polyester film obtained by molding an intimate mixture of about 4% by weight (based on the aromatic polyester).