JPH05179022A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film having uniform surface and excellent in operating properties and abrasion resistance represented in traveling property and winding characteristics. CONSTITUTION:The objective biaxially oriented polyester film is characterized by including 0.005-2.0wt.% globular vaterite type calcium particle having 0.07-1.5mum average particle diameter and 0.4 to pi/6 volume shape factor phiV and being <=2.00 in the distribution value of particle size defined in the following formula: The distribution value of particle sized25/d75 [wherein d25 and d75 exhibit particle size (mum) obtained by measuring integrate volume of the particle group from larger particle side and corresponding to 25% and 75% of total volume, respectively].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film having a uniform surface and excellent running properties and abrasion resistance.

[0002]

BACKGROUND OF THE INVENTION Biaxially oriented polyester films have been widely used as industrial materials, but in recent years, the preference for high grade has become remarkable in each application, and the film surface is uniform. It became strongly desired. On the other hand, the polyester film does not always have sufficient wear characteristics represented by abrasion of the film and abrasion of the surface layer and falling of particles, and improvement in this respect is desired. It is necessary to satisfy these points to a high degree in magnetic recording medium applications where particularly strict quality is required. Conventionally, as a means for improving the running property and abrasion resistance of a polyester film, a method of causing the surface of the film to be roughened by the presence of inert fine particles in the film is known, and some improvement has been made. However, sufficient results have not been obtained. For example, when so-called precipitated particles from a catalyst residue during polyester production are used as the fine particles, the fine particles are easily broken by stretching, so that the running property and wear resistance are poor, and it is also difficult to recycle and use the precipitated particles. is there.

When inert inorganic compound particles are added to polyesters such as silicon oxide, barium sulfate, titanium dioxide, calcium phosphate, etc., the fine particles are not broken or deformed by stretching, and the projections are relatively sharp. Although the runnability is improved, the particle size distribution of those particles is usually wide, and the particles easily fall off,
For example, when it is used for a magnetic recording medium, it often causes deterioration of electromagnetic conversion characteristics and frequent occurrence of dropouts. 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, in JP-A-62-207356 and JP-A-59-217755, respectively,
Monodisperse silicon oxide and crosslinked organic particles by emulsion polymerization are shown. However, when using silicon oxide particles, because of its high hardness, it is easy to scratch the substrate contacting the film, the improvement of wear resistance is insufficient,
On the other hand, when the crosslinked organic particles are used, not only the heat resistance is difficult, but also the particles are easily deformed by stretching. As described above, the actual situation is that a polyester film satisfying the surface uniformity, running property and abrasion resistance of the film at a high level has not been obtained so far.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that a film containing vaterite-type calcium carbonate particles having a specific shape has excellent properties. The present invention has been completed.

That is, the gist of the present invention is that the average particle size is 0.07 to 1.5 μm and the volume shape factor φ _V is 0.4 to π.
/ 6 and the particle size distribution value defined by the following formula is 2.0.
A biaxially oriented polyester film characterized by containing 0.005 to 2.0% by weight of spherical vaterite-type calcium carbonate particles, which is 0 or less. Particle size distribution value = d ₂₅ / d ₇₅ [In the above formula, d ₂₅ and d ₇₅ are measured by measuring the cumulative volume of the particle group from the large particle side, and the particle diameter corresponding to 25% and 75% of the total volume (μm )]]

The present invention will be described in detail below. In the present invention, the polyester means that 80% or more of repeating structural units are ethylene terephthalate units or ethylene-2,6.
-Refers to polyesters having naphthalate units. An important essence of the present invention is to use monodisperse spherical vaterite-type calcium carbonate as particles to be incorporated 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, as shown in, for example, JP-A-59-69425, a carbon dioxide-containing gas is added to a calcium hydroxide solution. Precipitable calcium carbonate particles by a so-called synthetic method of injecting and reacting are known. In this case, calcite-type calcium carbonate particles having a relatively uniform particle size are obtained, and it is known to mix the particles with a polyester film as disclosed in, for example, Japanese Patent Publication No. 16856/1989. Due to the wide size distribution of such particles, films with good properties at high levels 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 and reaction rate in the system are adopted. 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 including the reaction temperature and the reaction temperature. Such vaterite-type calcium carbonate particles can be added to the polyester production process as they are, but it is preferable to carry out 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-59-69.
Surface treatment agents, particularly polycarboxylic acids or their sodium salts, ammonium salts, etc., as described in JP-A-426-256 or JP-A-1-256558 are preferably used. These surface treatment agents are usually effective when added during the production process of particles.

In the present invention, among the vaterite type calcium carbonate particles, spherical particles are used. Volume shape factor φ of calcium carbonate particles used in the present invention
_V is 0.4 to π / 6, preferably 0.42 to π
/ 6, and more preferably 0.45 to π / 6. When vaterite-type calcium carbonate particles having a volume shape factor φ _V of less than 0.4 are compounded in a polyester film, the running property cannot be satisfied at a high level. The particle size distribution value of the vaterite type calcium carbonate particles used in the present invention 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, which may impair the electromagnetic conversion characteristics.
The withstand voltage will deteriorate.

The average particle size of the calcium carbonate particles used in the present invention is 0.07 to 1.5 μm, preferably 0.
10 to 1.2 μm, more preferably 0.12 to 1.0
μm. If the average particle size is less than 0.07 μm, the running property and wear resistance are hardly improved and it is unsuitable. on the other hand,
If the average particle size exceeds 1.5 μm, the surface roughness of the film becomes too high, and the electromagnetic conversion characteristics are impaired. The calcium carbonate particles used in the present invention are preferably porous from the viewpoint of affinity with polyester. Examples of the particles satisfying the above characteristics include VAN-S brand manufactured by Maruo Co., Ltd. The amount of calcium carbonate particles added to the film was 0.
005 to 2.0% by weight, preferably 0.01 to
It is 2.0% by weight, and more 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 are hardly improved and it is unsuitable. on the other hand,
When the blending amount exceeds 2.0% by weight, the surface roughness of the film becomes too high and the electromagnetic conversion characteristics are impaired.

As described above, in the present invention, vaterite type calcium carbonate particles having a specific shape and a specific particle size distribution are used, and the effect is remarkable when such particles and the following several requirements are combined. Become. First, in the case of a film containing 80 mol% or more of ethylene terephthalate units, the refractive index in the thickness direction of the film is 1.492 or more. If this value is less than 1.492, the effect of improving slipperiness and wear resistance may be insufficient. Moreover, when the refractive index in the thickness direction of the film is 1.492 or more, the adhesiveness to the magnetic layer can be improved, which is preferable. The refractive index in the thickness direction of the film is preferably 1.494 to 1.505. In the case of sequential biaxial stretching, the film having such physical properties has a longitudinal stretching temperature of 105 to 115 ° C. which is 5 to 30 ° C. higher than a normal stretching temperature.
It can be obtained by setting the degree. The second combination in which the effect of the present invention is particularly exerted is in the case of a film containing 80 mol% or more of ethylene terephthalate units,
The sum of the Young's modulus in the longitudinal direction and the Young's modulus in the lateral direction of the film is 900 kg / mm ² or more, more preferably 1000 k.
g / mm ² or more, particularly preferably 1100 kg / mm ²
That is all. Usually, when strongly stretched to have such a high strength, the particles easily fall off from the film surface layer and wear resistance deteriorates, but when the particles of the present invention are used, such drop-off phenomenon is reduced. Tend to do.
Such a high-strength film has, for example, a substantially non-oriented unstretched sheet at 3.0 ° C to 80 ° C to 120 ° C in the longitudinal direction.
6.0 times, then 3.0 to 6.0 times in the transverse direction, and 1
It can be obtained by heat treatment at 70 ° C to 240 ° C. Of course, it is also possible to adopt a method in which after sequential biaxial stretching in the longitudinal and transverse directions or simultaneous biaxial stretching, further re-stretching in the longitudinal direction by 1.05 to 2.5 times at a temperature of 110 ° C. to 180 ° C. and then heat treatment. At this time, a method such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, or micro-longitudinal longitudinal stretching before or after re-longitudinal stretching can be appropriately adopted. Further, re-stretching may be performed in the transverse direction as well.

A third combination in which the effects of the present invention are particularly exerted is polyethylene-2,6-as polyester.
It is to use a naphthalate unit containing 80 mol% or more. Among polyester films, a film containing 80 mol% or more of polyethylene-2,6-naphthalate units has been particularly noted because it has excellent mechanical strength and heat resistance. In particular, improved wear resistance is desired as it is often used under more stringent conditions in terms of tension. Particularly, the sum of the Young's modulus in the longitudinal direction and the Young's modulus in the lateral direction of the film is 1300 kg / mm ² or more, more preferably 14
00 kg / mm ² or more, particularly preferably 1500 kg /
When it is at least ² mm ² , the effect of improving the wear resistance is remarkable. In the case of polyethylene-2,6-naphthalate, such a high-strength film can be obtained by the same method as polyethylene terephthalate except that the stretching temperature is increased. That is, a substantially non-oriented unstretched sheet
In the vertical direction at 140 ° C to 120 ° C for 3.0 to 6.0.
Double, and then stretched in the transverse direction 3.0 to 6.0 times, 180 ° C
This is a method of heat treatment at ˜260 ° C. Of course, after sequential biaxial stretching in the longitudinal and transverse directions or simultaneous biaxial stretching,
A method of re-stretching 1.05 to 4.0 times in the machine direction at a temperature of 0 ° C. to 200 ° C. and then performing heat treatment can also be adopted. At this time, a method such as heat setting before re-longitudinal stretching, after re-longitudinal stretching, longitudinal relaxation, before or after re-longitudinal stretching, or micro-longitudinal stretching may be appropriately adopted. Further, re-stretching may be performed in the transverse direction as well.

As described above, in the present invention, the characteristics of the polyester film can be improved by using the vaterite type calcium carbonate particles having a specific shape and a specific particle size distribution. However, the effect is obtained in the above three cases. Can be especially enjoyed. In the present invention, it is possible to improve the running property, abrasion resistance, scratch resistance and the like of the film by using one or more kinds of other particles in combination within a range not exceeding the gist thereof. 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,
Even if one or more phosphorus compounds such as phosphoric acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, ethyl acid phosphate, phosphorous acid, trimethyl phosphite, triethyl phosphite, and tributyl phosphite are present. Good. 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 polycondensation reaction is carried out in the presence or absence of the phosphorus compound. Therefore, the precipitated particles according to the present invention contain one or more elements such as calcium, lithium, antimony and phosphorus.

Additive particles can also be used as the particles to be used in combination. The term "added particles" as used herein refers to particles added to the polyester from the outside, and specifically, kaolin, talc, carbon black, molybdenum sulfide, gypsum, aluminum oxide, barium sulfate, lithium fluoride, calcium fluoride. , Zeolite, calcium phosphate, silicon dioxide, titanium dioxide and heat-resistant polymer fine powder can also be mentioned. Typical examples of the heat-resistant polymer fine powder include a monovinyl compound having only one aliphatic unsaturated bond in the molecule and a cross-linking agent as described in JP-B-59-5216. Examples thereof include a copolymer with a compound having two or more aliphatic unsaturated bonds in the molecule, but are not limited thereto, and examples thereof include a thermosetting epoxy resin and a thermosetting pheno It is also possible to use fine powder of fluororesin such as resin, thermosetting urea resin, benzoguanamine resin or polytetrafluoroethylene.

Examples of particles that can be combined with the vaterite-type calcium carbonate particles of the present invention include natural calcium carbonate, calcite-type calcium carbonate produced by a synthetic method, and elliptic spherical, columnar or elliptic cylindrical vaterite-type calcium carbonate. You can Further, in the present invention, two or more kinds of vaterite type calcium carbonate particles of the present invention having different average particle diameters may be used. When the average particle size is larger than that of the vaterite-type calcium carbonate particles of the present invention, the amount of the particles used in combination in the present invention is preferably equal to or less than that of the calcium carbonate particles, and 0.005 to 0. 0.5 times the weight is more preferable, and 0.
A weight of 01 to 0.3 times is particularly preferable. On the other hand, when the average particle size is smaller than that of the vaterite-type calcium carbonate particles of the present invention, the amount is preferably equal to or more than the calcium carbonate particles, and more preferably 1 to 20 times the weight.

In recent years, base films for magnetic recording media have often been required to have flatness, smoothness, abrasion resistance, adhesiveness, and new scratch resistance. This is because, for example, when the tape travels at a high speed, the portion where the tape comes into contact is scratched, and the abrasion powder generated easily causes scratches on the film. If there are many scratches,
Not only is it unpleasant in appearance, but it also causes process contamination and increased dropout. In order to highly improve the scratch resistance, aluminum oxide is particularly preferably selected as the particles to be used in combination. In particular, aluminum oxide particles having an average particle size of 0.5 μm or less are preferable,
Delta-type or gamma-type aluminum oxide particles of 0.1 μm or less are more preferable, and delta-type aluminum oxide particles of 0.1 μm or less are particularly preferably used. As a method for producing these particles, for example, 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 reacted with sulfuric acid as a raw material to form aluminum sulfate. After that, 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,
Since aggregates often having a size of more than 0.5 μm are often 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 diameter is preferably 0.5 μm or less, and 0.1 μm or less.
m or less is particularly preferable.

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 they may be subjected to treatments such as crushing, dispersing, classifying and filtering in advance, if necessary. The concentration of slurry in the ethylene glycol added is 3
It is good to set it to ˜50% by weight, preferably 10 to 40%. 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. Further, 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, a commonly used catalyst such as Sb, Ti, Ge, Sn and Si compounds is used.

The film of the present invention which is particularly 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. The film surface roughness, the center line average roughness is usually , 0.005 to 0.
1 μm is preferable, 0.007 to 0.08 μm is more preferable, and 0.01 to 0.03 μm is particularly preferable. The film of the present invention can be particularly effective when used as a base film for video tape and also as a base film for audio. Of course, if necessary, it can be used for a dielectric of a capacitor, for packaging, for plate making, and for other purposes.

[0018]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods and definitions of various physical properties and characteristics in the examples are as follows. In the examples and comparative examples, "part" means "part by weight".

(1) Average Particle Size and Particle Size Distribution Centrifugal sedimentation type particle size distribution measuring device (SA-CP) manufactured by Shimadzu Corporation
Equivalent spherical distribution measured by type 3) 5
The average particle size was 0%. At the same time, the diameter of the point with a weight fraction of 25% and the weight fraction of 75% are added up from the large particle side.
The ratio of the diameters of the points was used as an index of the particle size distribution. (2) Volume shape factor φ _V Volume shape factor, φ _V is given by the following equation. φ _V = v / d ³ (In the above formula, v is the volume calculated from the average particle size obtained by the sedimentation method, and d is the arithmetic mean value of the particle sizes measured by electron microscope photography.) (3) Refractive index of film Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., the refractive index in the thickness direction of the film (nα), the maximum refractive index in the film plane (nγ), and the refractive index in the direction perpendicular thereto. (N
β) was measured. The refractive index was measured using sodium D line. (4) Young's modulus (tensile modulus) manufactured by Intesco Co., Ltd. Tensile tester Intesco Model 20
Using the 01 type, a sample film having a length of 300 mm and a width of 20 mm was pulled at a strain rate of 10% / min in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH, and the initial tensile stress-strain curve was obtained. Young's modulus (E) was calculated by the following equation using the linear portion. E = Δσ / Δε (where E, Δσ, and Δε are Young's modulus (kg
/ Mm ² ), the stress difference due to the original average cross-sectional area between two points on a straight line, and the strain difference between the same two points) (5) Average roughness of film surface and uniformity of roughness Japanese Industrial Standard JIS According to the method described in B0601, Kosaka Laboratory Ltd. surface roughness measuring device (SE-
3F) was used to determine the centerline average roughness (Ra) and maximum height (Rt). The smaller Rt / Ra, the more uniform the surface. (6) Runnability It was evaluated by the slip property of the film. Sliding property is 53 g (T ₂ ) when the film is wound around a fixed hard chrome-plated metal roll (diameter 6 mm) at a winding angle (θ) of 135 °.
The load was applied to one end to run at a speed of 1 m / min, the resistance (T ₁ , g) at the other end was measured, and the friction coefficient (μd) during running was determined by the following formula.

[0020]

[Equation 1]

(7) Number of Coarse Protrusions Aluminum was vapor-deposited on the film surface, and the number was measured using a two-beam interference microscope. The measurement wavelength was 0.54 μm, and the number showing the interference fringes of the third order or higher was converted and shown per 10 cm ² . (8) Wear characteristics The wear characteristics were evaluated by the following two methods. (A) Number of particle dropouts Gold film was vapor-deposited on the surface of the film and photographed with a scanning electron microscope at a magnification of 2000 times. The tip portions of the projections, which were determined to be formed by the particles, disappeared and became a depression. The number was measured and converted per unit area (1 mm ² ). The smaller this value is, the better. (B) Amount of white powder generated A film was wound around a fixed pin made of hard chrome having a diameter of 6 mm and brought into contact at an angle of 135, and the speed was 10 m / mi.
The film was run for 1000 m at a tension of 200 g and the amount of worn white powder adhering to the pins was visually evaluated and evaluated according to the ranks shown below. Rank A: Not attached at all Rank B: Attached in a small amount Rank C: Attached in a small amount (more than Rank B) Rank D: Attached extremely

(9) Magnetic tape characteristics First, a magnetic tape was manufactured. That is, the magnetic fine powder 20
0 parts, polyurethane resin 30 parts, nitrocellulose 10
Parts, 10 parts of vinyl chloride-cellulose acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone, 100 parts of methyl isobutyl ketone, and 300 parts of methyl ethyl ketone are mixed and dispersed in a ball mill for 48 hours, and then 5 parts of polyisocyanate compound is added to the magnetic paint. After applying this to a polyester film, it was magnetically oriented before the paint was sufficiently dried and solidified, and then dried to form a magnetic layer having a thickness of 2 μm. Then, this coating film 5000 m was used with a five-step super calender composed of a mirror-finished metal roll and a polyester-based composite resin roll.
Roll temperature 85 ° C, linear pressure 250 kg / cm, running speed 8
The amount of white powder adhering to the resin roll was visually evaluated by repeatedly running 7 times under the condition of 0 m / min, and evaluated according to the ranks shown below. ◯: Almost no white powder adhered to the resin roll Δ: Very slight white powder adhered was seen ×: Obvious white powder adhered Also, 1 / mm of the magnetic tape obtained by the above method After slitting to a width of 2 inches, the following magnetic tape characteristics were evaluated at a constant speed using a Matsushita Electric NV-3700 type video deck. (I) VTR head output The VTR head output at a measurement frequency of 4 MHz was measured with a synchroscope, and the relative value was expressed in decibels with the blank being 0 decibel (dB). (Ii) Number of dropouts A videotape recording a signal of 4.4 MHz was played back, and the number of dropouts was measured for about 20 minutes with a dropout counter of Okura Industry Co., Ltd. and converted into the number of dropouts per minute. ..

(10) Scratch resistance A magnetic tape slit to a width of 1/2 inch has a diameter of 6 mm.
Wrap the film around the hard chrome plated metal pin (Finishing 3S) of 135 °, traveling speed 4m / min, tension 5
The base film surface of the magnetic tape was rubbed once with 0 g. 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: Extremely 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 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. It took 4 hours to raise the temperature to 230 ° C. and substantially complete the transesterification reaction. Next, average particle size 0.24 μm, particle size distribution value 1.5
Almost spherical (volume shape factor, φ _V = 0.50) vaterite type calcium carbonate (VAN-S02 manufactured by Maruo Co., Ltd.)
0) 0.5 part was added as ethylene glycol slurry. The particles have been surface-treated in advance with a high molecular weight polycarboxylic acid (3% by weight based on the particles). After the slurry was added, 0.03 part of phosphoric acid and 0.04 part of antimony trioxide were further added, and polycondensation reaction was carried out for 4 hours to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65. When the inside of the obtained polyester was observed with a microscope, it was confirmed that the particles were uniformly dispersed. Then, a biaxially stretched polyester film was produced using the obtained polyester. That is, after drying the polyester, it is melt extruded at 290 ° C. to obtain an amorphous sheet,
The film was stretched 3.5 times at 110 ° C. in the machine direction (longitudinal direction) and 3.5 times at 110 ° C. in the transverse direction, and heat-treated at 220 ° C. for 3 seconds to obtain a film having a thickness of 15 μm. The Young's modulus of the obtained film was 430 kg / mm ² in the longitudinal direction,
The lateral direction was 440 kg / mm ² . A magnetic layer was applied to the obtained film to obtain a magnetic tape, and its characteristics were measured.

Comparative Examples 1 and 2 Agglomerated calcite-type calcium carbonate (Comparative Example 1) obtained by a synthesis method having an average particle size of 0.25 μm and a particle size distribution value of 2.05 or an average particle size of 0.40 μm and a particle size distribution value of 2. A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the flat kaolin of No. 65 (Comparative Example 2) was used and the contents shown in Table 1 were used, and the characteristics thereof were evaluated.

Example 2 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 set to 1.491, and its characteristics were evaluated. Example 3 With the vaterite-type calcium carbonate used in Example 1,
A film was obtained in the same manner as in Example 1 except that delta type aluminum oxide having a primary particle diameter of 0.03 μm was blended as shown in Table 2, and the characteristics thereof were evaluated. Example 4 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. to obtain a film, and its characteristics were evaluated.

Comparative Examples 3 and 4 Using the particles used in Comparative Examples 1 and 2, a film was obtained in the same manner as in Example 4 and its characteristics were evaluated. Example 5 In the production of the film of Example 1, after stretching in the longitudinal and transverse directions, 1.09 times in the transverse direction was conducted at 160 ° C. At this time, the particles used in the film were the same as those used in Example 3, and the characteristics were measured. Example 6 The transesterification reaction was performed in the same manner as in Example 1 except that dimethyl-2,6-dimethylnaphthalate was used instead of dimethyl terephthalate in the production of the polyester of Example 1. Next, 0.5 part of the vaterite-type calcium carbonate used in the examples was added as ethylene glycol slurry, 0.03 part of phosphoric acid and 0.04 part of antimony trioxide were added, and polycondensation reaction was carried out by a conventional method. Then, polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.59 was obtained. The obtained polymer is 0.3 mmHg, 2
Solid phase polymerization was carried out at 35 ° C. for 7 hours to obtain polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.68. The obtained polymer was extruded in a sheet shape from an extruder at 295 ° C., and an amorphous sheet having a thickness of 100 μm was obtained using an electrostatic cooling method.
It is 4.2 times in the vertical direction at 140 ° C and 3. in the horizontal direction with a tenter.
After being stretched 9 times, a heat treatment was performed at 220 ° C. for 5 seconds to obtain a polyethylene-2,6-naphthalate film having a thickness of 8 μm, and its characteristics were evaluated.

Example 7 Similar to the particles used in Example 6 and having an average particle size of 0.28 μm.
Same as Example 6 except that the same spherical vaterite type calcium carbonate particles (VAN-S030 manufactured by Maruo Co., Ltd.) as in Example 6 except that m is used and Young's modulus in the longitudinal direction is 1010 kg / mm ^2. And polyethylene-2,6-
A naphthalate film was obtained and its characteristics were evaluated. Example 8 Polyethylene-2,6-as in Example 6 except that the particles used in Example 6 were changed as shown in Table 5.
A naphthalate film was obtained and its characteristics 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 8 and its characteristics were evaluated. The results obtained above are summarized in Tables 1-5.

[0029]

Table 1 Example 1 Comparative Example 1 Comparative Example 2 ──────────────────────────────────── < Blended Particles> [First Particles] Type Vaterite Type Calcite Type Kaolin Calcium Carbonate Calcium Carbonate Average Particle Size (μm) 0.24 0.25 0.40 Content (wt%) 0.50 0.50 0.50 [Second Particle] Type --- --Average particle size (μm) --- --Content (wt%) ----- <Film characteristics> nα 1.497 1.497 1.496 Ra (μm) 0.0130 .014 0.013 Rt / Ra 8 18 18 Sliding property 0.27 0.26 0.33 Abrasion resistance Number of particles falling off 3 86 44 White powder generation amount A A to B B to C <Magnetic tape property> Calendar -Dirt ○ ○-△ △ -X S / N (dB) +0.4 -1.1 -1.5 Dropout (Pieces / min) 6.7 12.5 15.6 scratch resistance 3 2 1

[0030]

[Table 2] Example 2 Example 3 ──────────────────────────────────── <Blended particles> [First Particles] Type Vaterite Type Vaterite Type Calcium Carbonate Calcium Carbonate Average Particle Size (μm) 0.24 0.24 Content (wt%) 0.50 0.50 [Second Particle] Type-Al ₂ O ₃ Average particle size (μm) -0.03 Content (wt%) -0.40 <Film property> nα 1.491 1.497 Ra (μm) 0.013 0.013 Rt / Ra 10 8 Slidability 0 .28 0.23 Abrasion resistance Number of particle drop traces 10 7 Amount of white powder generation A to B A <Magnetic tape characteristics> Calendar dirt 〇 〇 S / N (dB) +0.0 +1.0 Dropout (pieces / Min) 6.5 3.3 Scratch resistance 35

[0031]

[Table 3] Example 4 Comparative Example 3 Comparative Example 4 ──────────────────────────────────── < Blended particles> [First particles] Type Vaterite type Calcite type Kaolin Calcium carbonate Calcium carbonate Average particle size (μm) 0.24 0.25 0.40 Content (wt%) 0.50 0.50 0.40 [Second particles] Type --- --Average particle size (μm) ----- Content (wt%) ----- <Film property>Young's modulus (kg / mm ² ) Longitudinal direction 700 690 700 Lateral direction 440 440 420 Ra (μm) 0.012 0.012 0.012 Rt / Ra 8 17 16 Sliding property 0.27 0.26 0.32 Abrasion resistance Number of particles falling off 5 95 50 White powder generation amount A B B to C <Magnetic Tape characteristics> Calendar dirt 〇 △△ 〜X S / N (dB) ＋0 2 -1.6 -1.7 drop-out (pieces / min) 6.8 12.7 15.5 scratch resistance 3 2 1

[0032]

Table 4 Example 5 Example 6 Example 7 ──────────────────────────────────── < Blended Particles> [First Particles] Type Vaterite Type Vaterite Type Vaterite Type Calcium Carbonate Calcium Carbonate Calcium Carbonate Average particle size (μm) 0.24 0.24 0.28 Content (wt%) 0.50 0.50 0 .50 [Second particles] Type Al ₂ O ₃ --- Average particle size (μm) 0.03 --- Content (wt%) 0.40 --- <Film characteristics>Young's modulus (kg / mm ² ) Length Direction 460 730 1010 Lateral direction 690 720 700 Ra (μm) 0.012 0.012 0.016 Rt / Ra 8 8 8 Sliding property 0.28 0.28 0.23 Abrasion resistance Number of particles falling off 5 4 7 White powder Amount A A A <Magnetic tape characteristics> Calendar dirt 〇 〇 〇 S / N (dB) +0.3 +0.2 +0.2 Dropout (pieces / min) 2.0 6.4 7.0 Scratch resistance 5 3 3

[0033]

Table 5 Comparative Example 5 Comparative Example 6 Example 8 ──────────────────────────────────── < Blended Particles> [First Particles] Type Calcite type Kaolin Vaterite type Calcium carbonate Calcium carbonate Average particle size (μm) 0.25 0.40 0.24 Content (wt%) 0.50 0.50 0.50 [Second Particle] Type --- Al ₂ O ₃ Average Particle Diameter (μm) --- 0.03 Content (wt%) --- 0.40 <Film Property>Young's Modulus (kg / mm ² ) Longitudinal 720 730 730 Lateral direction 730 720 730 Ra (μm) 0.012 0.012 0.012 Rt / Ra 20 21 8 Sliding property 0.24 0.35 0.27 Abrasion resistance Number of particles falling off 92 65 5 White powder generation amount B B to C A <Magnetic tape characteristics> Calendar stain Δ Δ to X ○ S / N (dB) -1.4 -1.6 +0.4 Dropout (pieces / minute) 12.1 14.5 1.8 Scratch resistance 2 15

Each of the films of Examples satisfying the requirements of the present invention has a uniform film surface and is excellent in 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 a magnetic recording medium.

[0035]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display area B29K 67:00 B29L 7:00 4F C08L 67:00

Claims (1)

[Claims] 1. The average particle diameter is 0.07 to 1.5 μm, the volume shape factor φ _V is 0.4 to π / 6, and the particle size distribution value defined by the following formula is 2.00 or less. A biaxially oriented polyester film, containing 0.005 to 2.0% by weight of spherical vaterite-type calcium carbonate particles. Particle size distribution value = d ₂₅ / d ₇₅ [In the above formula, d ₂₅ and d ₇₅ are measured by measuring the cumulative volume of the particle group from the large particle side, and the particle diameter corresponding to 25% and 75% of the total volume (μm )]]