JPH0796265B2 - Biaxially oriented polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film having a uniform surface and excellent running properties and abrasion resistance.

[Problems to be Solved by Prior Art and Invention]

The biaxially oriented polyester film is widely used as an industrial material, but in recent years, the tendency toward high grade has become remarkable in each application, and it has been strongly desired that the film surface be uniform. On the other hand, from the viewpoint of characteristics, the abrasion characteristics represented by the abrasion of the film and the abrasion of the surface layer and the falling of particles are not always sufficient, and improvement in this respect is desired. In magnetic recording applications where particularly strict quality is required, it is necessary to satisfy these points to a high degree.

Conventionally, as a means for improving the running property and abrasion resistance of a polyester film, a method of causing inert fine particles to exist in the film and appropriately roughening the film surface has been known, and some improvement has been made. However, the sufficient effect is not always obtained.

For example, when so-called precipitated particles are used as the fine particles from a catalyst residue during the production of polyester, the fine particles are easily broken by stretching, so that the running property and wear resistance are poor,
It is also difficult to recycle.

When inert inorganic compound particles are added to polyesters such as silicon oxide, barium sulfate, titanium dioxide and calcium phosphate, the particles are not broken or deformed by stretching, and relatively sharp projections are given. And the running property is improved, but the particle size distribution is usually wide,
Since particles easily fall off, when used for magnetic recording, for example, electromagnetic conversion characteristics often deteriorate and dropouts frequently occur.

In order to overcome these problems, it has recently been proposed to use inorganic or organic particles having a sharp particle size distribution. For example, JP-A-62-207356 and JP-A-59-2177.
JP-A-55 discloses monodisperse silicon oxide and crosslinked organic particles produced by emulsion polymerization. However,
When silicon oxide particles are used, the hardness thereof is high, so that the base material with which the film comes into contact is easily damaged, and when crosslinked organic particles are used, the particles are easily deformed by stretching and also in heat resistance. There are difficulties.

As described above, it is the actual situation that a polyester film having a high degree of uniformity in film surface, running property and abrasion resistance has not been obtained so far.

[Means for Solving the Problems]

As a result of intensive investigations in view of the above problems, the present inventors have found that a film containing vaterite-type calcium carbonate particles having a specific shape can achieve such an object, and have completed the present invention. .

That is, the gist of the present invention is that the average particle size is 0.07 to 1.5 μm.
And a biaxially oriented polyester film containing 0.005 to 2.0% by weight of columnar or elliptic columnar vaterite-type calcium carbonate particles having a particle size distribution value defined by the following formula of 2.00 or less.

(In the above formula, d ₂₅ and d ₇₅ are particle sizes (μm) corresponding to 25% and 75% of the total volume obtained by measuring the cumulative volume of the particle group from the large particle side.) The details will be described.

The polyester referred to in the present invention is a repeating structural unit of 80
The above is ethylene terephthalate unit or ethylene-2,
Refers to polyesters having 6-naphthalate units. Further, the polyester film of the present invention refers to a biaxially oriented film using such polyester as a starting material, and a known method can be used as a production method thereof. For example, usually melt-extruded into a sheet at 270 ~ 320 ℃, then cooled and solidified at 40 ~ 100 ℃ into an amorphous sheet,
Next, at 80-140 ℃, lengthwise so that the area magnification is 4-20 times,
Stretch horizontally or sequentially and heat-treat at 160-250 ° C. If necessary, stretching or heat treatment in multiple stages,
Alternatively, re-stretching or the like may be performed.

One of the characteristics of the present invention is that monodisperse columnar or elliptical columnar vaterite-type calcium carbonate is used as the particles to be mixed in the polyester film.

Conventionally, as a method for producing calcium carbonate particles, in addition to a method of crushing and classifying natural calcium carbonate, for example, JP-A-59-
As shown in Japanese Patent No. 69425, there is known a precipitated calcium carbonate particle by a so-called synthetic method in which a carbon dioxide-containing gas is injected into a calcium hydroxide solution and reacted. In this case, calcite-type calcium carbonate particles having a relatively uniform particle size can be obtained.
It is also known to incorporate it into a polyester film as disclosed in Japanese Patent Application Publication No. JP-A-2003-242242, but since the particles cannot reach the desired particle size distribution, a film having good properties cannot be obtained.

The present inventors have adopted a carbonation reaction in which carbon dioxide is blown in an alcohol medium, in which methanol is a typical example, in such a synthetic method, and the hydrogen ion concentration in the system, the reaction rate, and the reaction temperature are included. It was found that vaterite-type calcium carbonate particles having an extremely sharp particle size distribution can be produced by appropriately selecting the production conditions. The vaterite-type calcium carbonate particles can be added to the polyester production process as they are, but it is preferable that they are subjected to a surface treatment in order to reduce the solubility in the reaction system and improve the dispersibility. Examples of the surface treatment agent which also serves as the dispersant include, for example, JP-A-59-69426 and JP-A-1-2.
Surface treatment agents as described in JP 56558, especially polymeric polycarboxylic acids or their sodium salts,
Ammonium salts and the like are preferably used. These surface treatment agents are usually effective when added during the production stage of the particles.

In the present invention, among these vaterite-type calcium carbonate particles, columnar or elliptical columnar particles are particularly used. In this case, the height of the cylinder is 0.1 to 1.0 times the average value of the diameters of the major axis and the minor axis of the bottom surface (average bottom surface diameter), preferably 0.2 to 0.6.
Doubled particles are suitable for use in the present invention. In the case of such a shape, the particles are arranged substantially parallel to the film surface in the biaxially stretched film, and it is difficult for the particles to fall off even when worn.

If the ratio of the height of the cylinder to the average bottom diameter is less than 0.1, the particles are likely to be damaged during the processing of the particles or the film production process, and the surface protrusions are too small. On the other hand, when this value exceeds 1.0, the particles become close to lumps and come off from the film surface relatively easily.

In the present invention, even if the central portion of the particle is slightly thicker or the bottom surface is slightly different from a true ellipse, basically the same effect is obtained as long as it is a columnar shape or an elliptic shape. Can be demonstrated.

The particles may or may not be porous,
The former is superior in affinity with polyester.

Further, in the present invention, the particle size distribution value of calcium carbonate particles is 2.00 or less, preferably 1.80 or less, more preferably 1.50 or less. When the particle size distribution value exceeds 2.00, the surface roughness of the finally obtained film becomes non-uniform, so that the electromagnetic characteristics are impaired and the withstand voltage is deteriorated.

The average particle size of the calcium carbonate particles used in the present invention is
The thickness is 0.07 to 1.5 μm, preferably 0.15 to 1.0 μm. If the average particle size is less than 0.07 μm, the running property and wear resistance are hardly improved, while if it exceeds 1.5 μm, the roughness is uniform but the absolute value becomes too large, and the electromagnetic characteristics deteriorate. .

The amount of calcium carbonate particles added to the film is 0.00
It is selected from the range of 5 to 2.0% by weight, preferably 0.01 to 0.8% by weight. If the blending amount is less than 0.005% by weight, the running property and wear resistance will not be improved, and conversely, if it exceeds 2.0% by weight, the electromagnetic characteristics will deteriorate.

As described above, in the present invention, vaterite-type calcium carbonate particles having a specific shape and a specific particle size distribution are used, but the effect can be exhibited particularly when the particles and some of the following requirements are combined.

First, in the case of a film containing 80 mol% or more of ethylene terephthalate units, the film containing the particles has a refractive index of 1.492 or more in the thickness direction. If this value is less than 1.492, the effect of imparting slipperiness and abrasion resistance is insufficient even if the particles of the present invention are used. This value is preferably 1.494 or more and 1.505 or less. In the case of longitudinal-transverse sequential biaxial stretching, for example, a film having such physical properties can be obtained by setting the longitudinal stretching temperature to about 105 to 115 ° C., which is 5 to 30 ° C. higher than the normal stretching temperature. Alternatively, it can also be obtained by performing a large lateral relaxation after the biaxial stretching and before the heat treatment.

When the refractive index in the thickness direction of the film is 1.492 or more, another advantage is that the adhesiveness with the magnetic layer is improved.

A second combination in which the effect of the present invention is particularly exerted is a film containing 80 mol% or more of ethylene terephthalate units, in which the sum of Young's modulus in the machine direction and the Young's modulus in the machine direction is 900 kg / mm ² or more, particularly 1000 kg / mm ² or more, especially 1100 kg / mm
It is a case of ² or more.

Usually, when strongly stretched to have such high strength, the particles easily fall off from the surface layer and wear resistance deteriorates, but in the case of the flat particles of the present invention, the bottom surface of the particles is parallel to the film surface. Therefore, the number of dropouts decreases.

The high-strength film can be obtained, for example, by using the following known film-forming method. Ie 270
After melt extruding the polyester chips into a film at ℃ ~ 300 ℃, after cooling and solidifying at 40 ℃ ~ 70 ℃ to form an amorphous sheet, at 80 ℃ ~ 120 ℃ 3.0 times to 6.0 times in the vertical direction, then in the horizontal direction This is a method in which it is stretched 3.0 to 6.0 times and heat-treated at 170 to 240 ° C. Of course, after the biaxially stretching in the longitudinal and transverse directions or the simultaneous biaxial stretching, at a temperature of 110 ° C to 180 ° C, 1.05 to
A method of performing heat treatment after performing 2.0 times re-stretching can also be adopted.
At this time, a technique such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, or before or after re-longitudinal stretching and fine stretching longitudinal stretching can be appropriately adopted. Further, re-stretching may be performed in the transverse direction as well.

The third case where the effects of the present invention are particularly effectively exerted is
This is the case where calcium carbonate particles are blended with a polyethylene-2,6-naphthalate film.

Among the polyester films, polyethylene-2,6 containing 80 mol% or more of ethylene-2,6-naphthalate units
-A naphthalate film is attracting attention because it is excellent in mechanical strength and heat resistance and is being put to practical use. However, since the film is often used under more severe conditions in terms of running speed and tension of the film, abrasion resistance is improved. Improvement is desired.

In particular, the sum of Young's modulus in the longitudinal direction of the film and Young's modulus in the lateral direction is 1300 kg / mm ² or more, preferably 1400 kg / mm ² or more, and more preferably in the case of a film strongly stretched to be 1500 kg / mm ² , The bottom surface of the grain is parallel to the film surface, improving the wear properties.

In the case of polyethylene-2,6-naphthalate, such a high-strength film can be obtained by using the same method as that of polyethylene terephthalate except that the stretching temperature is increased. For example, melt-extruded and solidified by cooling at 280 ° C to 320 ° C, a substantially non-oriented unstretched sheet of polyethylene-2,6-naphthalate is sequentially biaxially stretched longitudinally and transversely or simultaneously biaxially stretched, and then in the longitudinal direction. Re-longitudinal stretching of 1.05 times or more and 4.0 times or less is again performed at 140 ° C to 200 ° C. Further, the film is heat-treated at a temperature of 180 ° C. or higher and 260 ° C. or lower. At this time, similarly, methods such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, before or after re-longitudinal stretching, and fine longitudinal stretching can be appropriately adopted.

As described above, in the present invention, the characteristics of the polyester film can be improved by using certain specific calcium carbonate particles, but in the cases of the above three cases,
The effect can be especially enjoyed.

By the way, in the present invention, one or more kinds of other particles may be used in combination within a range not exceeding the gist thereof to further improve the running property, winding property, scratch resistance and the like of the film.

Precipitated particles can be mentioned as one of such particles. The term "precipitated particles" as used herein refers to particles that are precipitated in the reaction system by polymerizing a system using an alkali metal or alkaline earth metal compound as a transesterification catalyst by a conventional method. Alternatively, terephthalic acid may be added during the transesterification reaction or polycondensation reaction to cause precipitation. In these cases, phosphoric acid, trimethyl phosphate,
One or more phosphorus compounds such as triethyl phosphate, tributyl phosphate, ethyl acid phosphate, phosphorous acid, trimethyl phosphite, triethyl phosphite and tributyl phosphite may be present.

In addition, the inert substance particles can be deposited by these methods even when the esterification step is performed. For example, before or after the completion of the esterification reaction, an alkali metal or alkaline earth metal compound is allowed to exist, and the polymerization reaction is carried out in the presence or absence of the phosphorus compound.

In any case, the fine precipitation compound generated during the polyester forming reaction in the present invention includes calcium, lithium,
It contains one or more elements such as antimony and phosphorus.

Also, so-called additive particles can be used as one of the particles used in combination. The added particles refer to particles externally added to the polyester manufacturing process, specifically, kaolin,
Examples thereof include talc, carbon, molybdenum sulfide, gypsum, rock salt, aluminum oxide, barium sulfate, lithium fluoride, calcium fluoride, zeolite, calcium phosphate, silicon dioxide and titanium dioxide.

As an example of such added particles, heat-resistant polymer fine powder can be cited. As a typical example in this case, a monovinyl compound having only one aliphatic unsaturated bond in the molecule, as described in, for example, JP-B-59-5216, and a divinyl compound in the molecule as a cross-linking agent. Examples thereof include a copolymer with a compound having one or more aliphatic unsaturated bonds, but are not limited thereto. For example, thermosetting phenol resin, thermosetting epoxy resin, thermosetting It is also possible to use a fine powder of a urea resin, a benzoguanamine resin, or a fluorine resin such as polytetrafluoroethylene.

As a matter of course, as particles that can be combined with the vaterite-type calcium carbonate particles of the present invention, natural calcium carbonate, calcite-type calcium carbonate by a synthetic method, or vaterite-type calcium carbonate by a spherical or elliptic spherical synthetic method is used. Can be mentioned.

Further, in the present invention, two or more kinds of vaterite type particles of the present invention having different average particle sizes may be used.

When the average particle size of the particles used in the present invention is larger than that of the vaterite-type calcium carbonate of the present invention, the weight is equal to or less than that of the calcium carbonate, preferably 0.005.
˜0.5 times the weight, more preferably 0.01 to 0.3 times the weight. Further, when the particle size of the particles used in combination is smaller than the same weight as calcium carbonate, for example, 1 to 20.
The weight can be doubled.

In recent years, in addition to flatness, slipperiness, abrasion resistance and adhesiveness, a base film for magnetic recording is often required to have new scratch resistance. This is because, for example, when the tape travels at a high speed, the tape may be damaged from the contact portion, or the film may be easily damaged by the abrasion powder generated. Not only does it look bad if it is scratched, but it also causes process contamination and increased dropouts.

In order to highly improve the scratch resistance, it is particularly preferable to select aluminum oxide as the particles to be used in combination.
In particular, delta-type or gamma-type aluminum oxide particles having an average particle size of 0.5 μm or less, preferably 0.1 μm or less, and particularly delta-type aluminum oxide particles are preferably used. Examples of the method for producing these particles include a thermal decomposition method, that is, a method of flame hydrolysis using anhydrous aluminum chloride as a raw material, or an ammonium alum thermal decomposition method, that is, aluminum hydroxide is used as a starting material and reacted with sulfuric acid to form aluminum sulfate. Then, a method of reacting with ammonium sulfate and baking it as ammonium alum can be mentioned.

The primary particle size of aluminum oxide obtained by these methods is usually in the range of 5 to 40 nm, but often 0.5 μm.
Since aggregates exceeding m are formed, it is desirable to appropriately crush and use. In this case, the secondary particles may be agglomerated to some extent, but the apparent average particle size is usually
It is 0.5 μm or less, preferably 0.1 μm or less.

Thus, by blending vaterite-type calcium carbonate having a specific shape and other particles such as fine aluminum oxide particles as necessary, an extremely excellent polyester film particularly suitable for a magnetic recording medium can be obtained. It will be possible.

In the production of the polyester containing the vaterite-type calcium carbonate particles of the present invention, it is preferable to add the particles and the additive particles used in combination during the polyester synthesis reaction. Particularly, it is preferably added after the completion of the transesterification reaction or the esterification reaction and before the start of the polycondensation reaction.

The particles to be added are usually added as a slurry of ethylene glycol, but may be subjected to treatment such as crushing, dispersing, classifying, and passing in advance, if necessary.

Slurry concentration in the added ethylene glycol is 5-50
It is good to set it as the weight%, preferably 10 to 40 weight%.

If the particle concentration of the slurry is less than 3% by weight, the amount of ethylene glycol used increases and the basic unit of ethylene glycol increases, which is not preferable. Moreover, when a slurry having a particle concentration of more than 50% by weight is added, the dispersibility of particles is often deteriorated.

As the polycondensation reaction catalyst for polyester synthesis, S
Commonly used catalysts such as b, Ge, Ti, Sn and Si compounds are used.

Especially the film of the present invention suitable for a magnetic recording medium is obtained for the first time by a combination of specific particles and specific physical properties of the film, but the film surface roughness is a center line average roughness of usually 0.005 to 0.1 μm, preferably 0.
It is appropriately adjusted and selected so as to be in the range of 007 to 0.08 μm, more preferably 0.01 to 0.03 μm.

The film of the present invention can be particularly effective when used as a base film for a video tape and also as an audio film.

Of course, if necessary, for capacitor dielectrics, packaging,
It can also be used for decoration, plate making, and other purposes.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded.

The physical properties of the present invention were measured according to the following methods.

In the examples, "part" and "%" mean "part by weight" and "% by weight", respectively.

(1) Average particle size and particle size distribution value The particle size was measured by a photographic method using an electron microscope and converted into equivalent spheres. Regarding the particle size distribution, the particle size of about 1000 particles was measured, and the volume was integrated from the large particle side. The particle diameter corresponding to 25% of the total volume was defined as d _25, and the particle diameter corresponding to 75% was defined as d ₇₅ , and the ratio [d ₂₅ / d ₇₅ ] indicated the sharpness of the particle size distribution.
The closer this value is to 1, the sharper the particle size distribution. The average particle size is represented by d ₅₀ (μm).

(2) Refractive index in the thickness direction of the film The Abbe type refractometer manufactured by Atago Optical Co., Ltd. was used to measure the refractive index n _α in the thickness direction of the film. The refractive index was measured at 23 ° C. using sodium D line.

(3) Young's modulus (tensile modulus) manufactured by Intesco Co., Ltd. Tensile tester Intesco Model 2001
Using a mold, a sample film with a length of 300 mm and a width of 20 mm was placed at 10% / min in a room controlled at a temperature of 23 ° C and humidity of 50% RH.
The Young's modulus (E) was calculated by the following equation using the first linear portion of the tensile stress-strain curve.

(4) Average roughness of film surface and uniformity of roughness According to the method described in Japanese Industrial Standard JIS B0601,
The center line average roughness (Ra) and the maximum height (Rt) were obtained using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. The smaller the Rt / Ra, the more uniform the surface.

(5) Travelability A film is wound around a fixed hard chrome-plated metal pin (diameter 6 mm) at a contact angle of 135 °, a load of 53 g is applied to one end and the product is run at a speed of 1 m / min, and the resistance force at the other end is measured. Then
The coefficient of friction of the film was determined by the Euler's equation and used as a measure of running property.

(6) Abrasion characteristics Evaluation was performed by the following two methods.

(A) Number of particle dropouts Gold film was vapor-deposited on the film surface and photographed with a scanning electron microscope at a magnification of 2000 times. Of the projections formed by the particles, the tips of the projections disappeared and became a depression. The number of objects was measured over 1 mm ² . The smaller this value, the better.

(B) Amount of white powder generated A film is wound around a fixed hard chrome-plated metal pin (diameter 6 mm) at a winding angle of 135 °, speed 10 m / min, tension 2
The film was run at 1000 g for 1000 m, and the amount of white powder adhering to the pins was visually observed to make the following judgment.

Rank A: No adhesion Rank B: Small amount adhesion Rank C: Small amount (more than Rank B) adhesion D: Extremely large adhesion (7) Magnetic tape characteristics First, apply the following magnetic paint to polyester film Then, the magnetic layer was formed so that the film thickness after drying was 2 μm. That is, 200 parts of magnetic fine powder, 30 polyurethane resin
Parts, nitrocellulose 10 parts, vinyl chloride / vinyl acetate copolymer 10 parts, lecithin 5 parts, cyclohexanone 100 parts, methyl isobutyl ketone 100 parts and methyl ethyl ketone 300 parts by mixing and dispersing in a ball mill for 48 hours, and then polyisocyanate compound 5
After adding parts, a magnetic paint was applied, which was applied to a polyester film, magnetically oriented before the paint was sufficiently dried and solidified, and then dried.

Then, when the coated film was subjected to a calendar treatment, the degree of stain on the roll surface contacting the base film was evaluated.

That is, using a five-stage super calender composed of a mirror-finished metal roll and a polyester-based composite resin roll, a magnetic tape of 5000 m under the conditions of a roll temperature of 85 ° C., a linear pressure of 250 kg / cm, and a running speed of 80 m / min. Was repeatedly run 7 times and the amount of white powder adhering to the resin roll was observed, and the following judgment was made.

○: Almost no adhesion of white powder was observed on the resin roll △: Very slight adhesion of white powder was observed ×: Obvious adhesion of white powder was observed. Then, after slitting the tape to 1/2 inch width, Matsushita The following magnetic tape characteristics were evaluated at a constant speed using an NV-3700 type video deck manufactured by Denki Co., Ltd.

VTR head output: The VTR head output at a measurement frequency of 4 MHz was measured with a synchroscope, and the relative value to the reference sample was displayed in decibel (dB).

(8) Scratch resistance A magnetic tape slit to a width of 1/2 inch is wrapped around a hard chrome-plated metal pin (diameter mm, finishing 3S) with a tension of 50 g, a winding angle of 135 °, and a running speed of 4 m / sec. Was rubbed once.

Next, aluminum was vacuum-deposited on the abraded surface to a thickness of about 1000Å and the amount of scratches was visually observed, and the following judgment was made.

Rank 1: Very large amount of scratches Rank 2: Large amount of scratches Rank 3: Intermediate amount of scratches 2, 4 Rank 4: Small amount of scratches Rank 5: No scratches Example 1 Dimethyl terephthalate 100 Parts and ethylene glycol 60
Parts and 0.09 parts of magnesium acetate / tetrahydrate in a reactor, the temperature of the mixture is heated and the methanol is distilled off to carry out a transesterification reaction. The temperature is raised to 230 ° C. in 4 hours from the start of the reaction, and the transesterification reaction is substantially carried out. Ended.

Next, an approximately elliptic cylinder with an average particle size of 0.22 μm and a particle size distribution value of 1.50 (the major axis of the elliptical bottom is about 0.30 μm, the minor axis is about 0.25 μm,
0.5 parts of vaterite-type calcium carbonate (VAX-030 manufactured by Maruo Calcium Co.) having a height of about 0.10 μm) was added as an ethylene glycol slurry. The particles were surface-treated in advance with a high molecular weight polycarboxylic acid (3% by weight based on the particles).

After adding the slurry, 0.03 parts of phosphoric acid, antimony trioxide
Add 0.04 part and carry out polycondensation reaction for 4 hours to obtain an intrinsic viscosity of 0.65.
Of polyethylene terephthalate was obtained.

When the inside was observed with a microscope, it was confirmed that the particles were uniformly dispersed.

Then, a biaxially stretched polyester film was produced using the polyester.

That is, the polyester is extruded in a sheet form from an extruder at a temperature of 295 ° C., and a thickness of 190 μm is obtained by using an electrostatic cooling method.
An amorphous sheet of m was obtained.

Next, the obtained amorphous sheet is stretched 3.5 times at 110 ° C. in the sheet flow direction (longitudinal direction) and further stretched 3.5 times at 110 ° C. in the direction (transverse direction) orthogonal to the sheet flow, and at 220 ° C. for 3 seconds. After heat treatment, it was cooled to obtain a biaxially stretched film having a thickness of 15 μm. The Young's modulus of the obtained film is 430k in the longitudinal direction.
The g / mm ² was 440 kg / mm ² in the lateral direction.

Comparative Examples 1 and 2 Agglomerated calcite-type calcium carbonate produced by a synthesis method having an average particle size of 0.25 μm and a particle size distribution value of 2.05 (Comparative Example 1) or flat kaolin having an average particle size of 0.40 μm and a particle size distribution value of 2.65 (Comparative Example A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that 2) was used and the contents were shown in Table 1, and the characteristics thereof were evaluated.

Example 3 Using the vaterite-type calcium carbonate used in Example 1,
A film was obtained in the same manner as in Example 1 except that the refractive index in the thickness direction of the film was 1.491, and its characteristics were evaluated.

Example 4 A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that delta type aluminum oxide having a primary particle diameter of 0.02 μm was blended as shown in Table 1 together with the vaterite type calcium carbonate used in Example 1. , Its characteristics were evaluated.

Example 5 A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that spherical silica having an average particle size of 0.20 μm and a particle size distribution value of 1.44 was used together with the vaterite-type calcium carbonate used in Example 1 and its properties were evaluated. .

The results obtained above are summarized in Table 1 below.

Example 6 In the production of the film of Example 1, the film was stretched in the machine and transverse directions, and then stretched 1.08 times in the machine direction at 130 ° C.

Comparative Examples 3 and 4 Using the particles used in Comparative Examples 1 and 2, a polyethylene terephthalate film was obtained in the same manner as in Example 6, and its characteristics were evaluated.

Examples 7 and 8 In the production of the film of Example 1, the film was stretched in the machine and transverse directions, and then 1.09 times in the transverse direction at 160 ° C. In addition,
The particles compounded in the film at this time were the same as those in Example 4 in Example 7 and the same as those in Example 5 in Example 8.

The results obtained above are summarized in Table 2 below.

Example 9 A transesterification reaction was carried out in the same manner as in Example 1 except that dimethyl-2,6-naphthalate was used instead of dimethyl terephthalate in the production of the polyester of Example 1.

Then, the vaterite type calcium carbonate used in Example 1 was used.
5 parts of ethylene glycol slurry was added, 0.03 parts of phosphoric acid and 0.04 parts of antimony trioxide were further added to carry out polycondensation reaction by a conventional method, and polyethylene having an intrinsic viscosity of 0.59 was added.
2,6-naphthalate was obtained.

The polymer obtained is then solid-state polymerized at 0.3mmHg and 235 ° C for 7 hours to obtain a polymer with an intrinsic viscosity of 0.68, which is extruded into a sheet at 295 ° C from an extruder and cooled by electrostatic cooling.
An amorphous sheet of 100 μm was obtained. Then, using the peripheral speed difference of the rotating rolls, it was drawn 4.2 times in the longitudinal direction at 140 ° C and 3.9 times in the transverse direction with a tenter, and heat treated at 220 ° C for 5 seconds.
A biaxially oriented film having a thickness of 8 μm was obtained.

Example 10 The same elliptic cylindrical vaterite-type calcium carbonate particles (VAX-040 manufactured by Maruo Calcium Co., Ltd.) as in Example 9 except that the particles were similar to the particles used in Example 9 and had a size 1.5 times larger, and Example 9 except that the Young's modulus in the longitudinal direction is 1000 kg / mm ^2.
A polyethylene-2,6-naphthalate film was obtained in the same manner as in 1. and its properties were evaluated.

Comparative Examples 5 and 6 Using the particles used in Comparative Examples 1 and 2, a polyethylene-2,6-naphthalate film was obtained in the same manner as in Example 9,
Its characteristics were evaluated.

Examples 11 and 12 A polyethylene-2,6-naphthalate film was obtained in the same manner as in Example 9 except that the particles used in Example 9 were changed as shown in Table 3, and the characteristics thereof were evaluated.

The results obtained above are summarized in Table 3 below.

The films of Examples satisfying the requirements of the present invention all have a uniform film surface and excellent abrasion resistance. In particular, a film containing fine aluminum oxide particles is also excellent in scratch resistance and is suitable as a base film for magnetic recording.

〔The invention's effect〕

The film of the present invention has a uniform fine surface structure, is particularly excellent in running properties and abrasion resistance, and is useful as an industrial material such as a base film of a magnetic recording medium, and has a high industrial value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B29K 67:00 105: 16 B29L 7:00 (56) Reference JP-A-4-40623 (JP, JP, A) JP-A-3-292354 (JP, A) JP-A-4-31456 (JP, A) JP-A-4-55464 (JP, A)

Claims (1)

[Claims] 1. A columnar or elliptical columnar vaterite-type calcium carbonate particle having an average particle size of 0.07 to 1.5 μm and a particle size distribution value defined by the following formula of 2.00 or less is contained in an amount of 0.005 to 2.0% by weight. Characteristic biaxially oriented polyester film. (In the above formula, d ₂₅ and d ₇₅ represent the particle size (μm) corresponding to 25% and 75% of the total volume, respectively, by measuring the cumulative volume of the particle group from the large particle side)