JPS63221135A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain the title film which is flat, excels in lubricity, chipping resistance, etc. and has a good winding form, by adding two kinds of spherical silica particles each of which is specified in the average particle diameter, particle diameter ratio and amount of addition in a polyester. CONSTITUTION:First spherical silica particles having an average particle diameter of 0.03-0.3mum and a particle diameter ratio (major diameter/minor diameter) of 1-1.2 and second spherical silica particles having an average particle diameter of 0.6-3mum and a particle diameter ratio of 1-1.2 are prepared. 0.02-2.5wt.% first spherical silica particles and the second spherical silica particles in an amount which is in the range of 0.002-2wt.% and is equal to or smaller than that of the first spherical silica particles are added to a polyester (e.g., polyethylene terephthalate). This polyester is formed into a film, which is biaxially oriented to obtain a biaxially oriented polyester film. This film can be suitably used as a base film for videotapes, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, and more specifically, the present invention relates to a biaxially oriented polyester film, which contains spherical silica particles with different average particle diameters, is flat, and has excellent sliding properties, abrasion resistance, etc. The present invention relates to a biaxially oriented polyester film having excellent and good winding appearance.

[Prior Art] Due to its excellent properties, biaxially oriented polyester films are widely used in many applications such as magnetic tapes, electricity, photography, metallization, and packaging. In particular, because of its high strength and modulus of elasticity, it is widely used as a base film for magnetic recording media, such as video tapes, audio tapes, computer tapes, floppy disks, etc.

In recent years, demands for higher density recording and higher quality have been increasing in these application fields, and as a result, there has been an increasing demand for the base polyester film to have a flat surface.

However, when the surface of the film becomes flat, the friction coefficient of the film increases, for example in magnetic tape applications, resulting in problems such as poor running and easy scratching. In addition, if the film surface becomes flat, the winding appearance of the film during the process of winding it into a roll during film production will deteriorate significantly, making it difficult to obtain a film roll with a good winding appearance. As productivity increases, film winding speeds need to be faster and wider, but as these speeds and widths have increased, it has become increasingly difficult to obtain film rolls with a good shape. There is also a problem.

Defects in the winding appearance of film rolls include (1) Symptoms of protrusions on the roll. ■Wrinkles occur in the longitudinal direction of the film. ■When the edge surface shifts, etc., ■ is when the slipperiness of the film is poor, ■: when winding with high tension to prevent protrusions, ■: when winding a flat film, there is a gap between the films. They tend to occur when the escape of the air layer that occurs becomes difficult.

Therefore, the base polyester film is required to have not only flatness but also excellent slipperiness and air escape properties in order to maintain a good film winding appearance. In particular, better air escape properties are required when winding the film at higher speeds and wider widths.

Conventionally, methods for improving the slipperiness of films include adding inorganic particles such as silicon oxide or calcium carbonate to polyester, or precipitating fine particles containing calcium, lithium, or phosphorus in the polymerization system during polyester synthesis. Proposed. In either method, when polyester is formed into a film, projections are formed on the surface of the film due to fine particles, thereby improving the slipperiness of the film.

However, in the above-mentioned method of improving the slipperiness of a film using protrusions made of fine particles, the slipperiness usually improves as the film surface becomes rougher. In media applications, magnetic coating tends to roughen the surface and deteriorate electromagnetic conversion characteristics.

These are contradictory. As one of the measures to solve the problems of flatness, slipperiness, and air escape, many methods have been proposed that utilize composite inorganic particles in which large-sized particles and small-sized particles coexist. However, these methods also have problems, and if they are not used as they are, it is difficult to improve the grade of magnetic recording media, for example, to increase the density.

It is difficult to meet demands such as higher quality. The reason for this is
The size of the large particles used in composite inorganic particles is coarse compared to the quality required for high-grade grades, and the larger the particles, the higher the protrusions on the film surface. In addition, the larger the particles, the higher the protrusions on the film surface and the larger the voids surrounding the particles. During the cleaning process or calendering process, high protrusions are scraped off, causing dropouts (missing information that occurs during recording and playback), and calendar stains during the processing process and dust from cleaning the base film surface. This causes fabric stains and greatly impairs its properties as a magnetic recording medium.

[Object of the Invention] The present inventor has solved the above-mentioned problems, and has provided a film that has both flatness and a good film winding appearance applicable to the field of high-quality magnetic recording applications, and has good abrasion resistance.

As a result of intensive research to develop a film with scratch resistance, the shape of the protrusions on the film surface was sharpened,
Furthermore, by using a specific combination of large particles and small particles, even if the film surface is flat, the slip properties, air escape properties, and abrasion resistance can be greatly improved. It is most preferable that the particles present in the film are spherical, and there are many particles that are close to spherical, including glass beads, but from these it is possible to create a film that satisfies the surface characteristics especially for video tapes. Although difficult, the inventors have discovered that a film satisfying the above characteristics can be obtained by using specific spherical silica particles in combination with large particles and small particles, and has thus arrived at the present invention.

Therefore, an object of the present invention is to maintain smoothness that can correspond to higher density recording and higher quality magnetic recording media, while improving slipperiness.
The object of the present invention is to provide a biaxially oriented polyester film having excellent abrasion resistance, scratch resistance, etc.

[Configuration/Effects of the Invention] According to the present invention, an object of the present invention is to provide polyester with an average particle diameter of 0.03 μm or more and less than 0.3 μm as a first component, and a particle size ratio (longer diameter/breadth diameter). Contains 0.01 to 2.5% by weight of spherical silica particles whose is 1.0 to 1.2,
And as a second component, spherical silica particles having an average particle diameter of 0.6 to 3 μm and a particle size ratio (major axis/breadth axis) of 1.0 to 1.2 are used. This can be achieved by using a two-wheel stretched polyester film containing the same amount or a smaller amount of the first component within the range of f amount %.

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component.

Such polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid,
Naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid.

Diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid.

Examples include diphenylketone dicarboxylic acid and anthracene dicarboxylic acid. Examples of aliphatic glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimebrene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, etc., or cyclohexane dimetatool. Examples include alicyclic diols.

In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as a main component are preferably used.

Among such polyesters, for example, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% of the total dicarboxylic acid component.
A copolymer in which the above is terephthalic acid and/or 2,6-naphthalene dicarboxylic acid and 80 mol% or more of the total glycol component is ethylene glycol is preferred. In this case, up to 20 mol% of the dicarboxylic acid of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or 2,6-naphthalene dicarboxylic acid, and also fatty acids such as adipic acid, cepatic acid, etc. The dicarboxylic acid may be an alicyclic dicarboxylic acid such as dichlorohexane-1,4-dicarboxylic acid. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2°2-bis(4-hydroxyphenyl)propane, etc.; , 4-dihydroxymethylbenzene; and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

In addition, the polyester used in the present invention contains a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydroxycaproic acid, and a dicarboxylic acid component and an oxycarboxylic acid component. Those copolymerized or combined in an amount of 20 mol % or less based on the total amount of acid components are also included.

In general, the polyester in the present invention contains a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimellitic acid, in a substantially linear amount, for example, 2 mol% or less based on the total acid component. Copolymers of pentaerythritol and the like are also included.

The above-mentioned polyesters are known per se, and can be produced by methods known per se.

The above polyester has an intrinsic viscosity of about 0.4 measured as a solution in 0-chlorophenol at 35°C.
~0.8 is preferred.

The biaxially oriented polyester film of the present invention has many fine protrusions on its surface.

According to the invention, these numerous microscopic protrusions originate from a large number of spherical silica particles dispersed and contained in the polyester.

Polyester containing dispersed spherical silica particles is usually produced at any time during the reaction to form the polyester, for example, during the transesterification reaction or polycondensation reaction when using the transesterification method, or at any time during the polycondensation reaction when using the direct polymerization method. It can be prepared by adding spherical silica particles (preferably as a slurry in glycol) into the reaction system at the same time. Preferably, the spherical silica particles are added to the reaction system at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

In the present invention, the spherical silica particles dispersed in the polyester have a particle diameter ratio (major axis/minor axis) of 1.0 to 1.2, preferably 1.0 to 1.1, more preferably 1.0 to 1.
05. These spherical silica particles have individual shapes very similar to pearls, and are either silica particles conventionally known as lubricants or ultrafine lump particles of about 10 mm, and these aggregate into aggregates of about 0.5 μm. It is distinctive in that it is significantly different from forming particles (agglomerated particles). If the particle size ratio is too large, the void ratio will become large, which may lead to poor machinability, which is not preferable. These spherical silica particles have an average particle size of 0 as the first component.
．． 03μn or more and less than 0.3μm, preferably 0.1μI
The first component is Iim or more and less than 0.3 μm, more preferably 0.1 μm or more and less than 0.2 μm, and the second component has an average particle size of 0.6 to 3.0 Iim, preferably 0.
゜6~1.5μm, more preferably 0.7~1.1μm
There are two types: the second component). If the average particle size of the spherical silica particles as the first component becomes too small, the effect of improving slipperiness will be insufficient, which is undesirable. If it becomes too large, the difference in average particle size with the second component will become small, causing air to escape. This is not preferable because the properties of the film deteriorate and the effect of improving the film winding appearance (edge misalignment) becomes insufficient. Moreover, if the average particle diameter of the spherical silica particles as the second component becomes too large, the surface flatness will become insufficient, which is not preferable.

Also, the difference in average particle size between the first component and the second component is 0130
μm or more, further 0.35μm or more, especially 0140μm
It is preferable that it is more than m. When the difference in average particle size between the first component and the second component becomes smaller, air escape performance becomes worse.
When winding film at wide widths and high speeds, edge misalignment is likely to occur.
This is not preferable because it makes the appearance of the film look bad.

Here, the diameter equivalent to two area circles of the major axis and minor axis of spherical silica particles is determined by depositing metal on the particle surface and then using an electron microscope to determine, for example, 1.
The average particle size is determined from an image magnified 30,000 to 30,000 times, and the average particle size ratio is determined using the following formula.

Average particle diameter = Area of measured particles Sum of circular phase diameters / Number of particle diameter ratio of measured particles = Average major diameter of silica particles / Average minor diameter of core particles Also, spherical silica particles have a sharp particle size distribution. Preferably, the relative standard deviation representing the steepness of the distribution is 0.
．． It is preferably 5 or less, more preferably 0.3 or less, particularly 0.2 or less.

This relative standard deviation is expressed by the following formula.

Here, Di = area circular diameter of individual particles (μm)? 1
5 = Average value of area circle equivalent diameter "1 Σ Di (=i=1>(μm) n: represents the number of particles.

When spherical silica particles with a relative standard deviation of 0.5 or less are used, the particles are truly spherical and have an extremely steep particle size distribution, so the distribution of protrusions formed on the film surface is extremely uniform. A polyester film with uniform height and excellent slip properties can be obtained.

Further, it is preferable that the particle size distributions of the first component and the second component do not substantially overlap each other. As long as the spherical silica particles satisfy the above-mentioned conditions, there are no limitations on the manufacturing method or the like. For example, spherical silica particles are produced by making monodisperse hydrated silica [Si(OH)4] spheres by hydrolyzing ethyl orthosilicate [Si (OCzf-1s>4]), and then dehydrating this hydrated silica monodispersion method. WA can be produced by growing silica bonds [=Si-o-3i=] three-dimensionally (Journal of the Chemical Society of Japan '81. NQ9.
p, 1503).

Si (OC21-15>4+411z.

→5i (Q tol) 4 + 4 G, 41sO
H=Si-Of-1+ 11Q-8i= →Mi5i-Q-8i=+HzO In the present invention, the amount of spherical silica particles added as the first component is 0.01 to 2.5% by weight based on the polyester. The content is preferably 0.02 to 1.5% by weight, more preferably 0.05 to 0.5% by weight. The amount of spherical silica particles added as the second component is 0.002 to 2.0% by weight, preferably 0.005 to 1% by weight based on the polyester.
．． 0% by weight, more preferably 0.01-0.3% by weight,
Particularly (preferably within the range of 0.01 to 0.09% by weight, the amount is the same as or less than the first component. Among these, an amount smaller than the first component is preferable. The amount added is less than 0.01% by weight, and the amount added of the second component is 0.
．． If the amount is less than 0.02% by weight, the effect of improving slipperiness and abrasion resistance is insufficient. Further, the total addition level of the first component and the second component is desirably 0.02 to 2.5% by weight, preferably 0.604 to 1.5% by weight, and more preferably 0.05 to 2.5% by weight.
0.1% by weight, particularly preferably 0.06-0.5% by weight
It is. If the total amount of addition is too large, the surface flatness will deteriorate, which is not preferable.

The polyester film in the present invention is a biaxially oriented film that has been accumulated in the past! ! r# according to the manufacturing method! I can do it up to For example, polyester containing spherical silica particles of a predetermined size is melt-cast to form an amorphous unstretched film,
Next, the unstretched film is biaxially stretched, heat-set, and if necessary, subjected to relaxation heat treatment to produce the film. At this time, the film surface properties vary depending on the particle size, amount, etc. of the spherical silica particles, and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions. Furthermore, since the density, thermal shrinkage rate, etc. change depending on the temperature doubling ratio, speed, etc. during stretching and heat treatment, conditions are determined to satisfy these characteristics at the same time.

For example, the stretching temperature ranges from (Tg-10) to (T(J+45)'
The range of C is from 1g (glass transition temperature of polyester) to the second stretching temperature (for example, lateral stretching temperature 2 T2).
) is preferably selected from the range of (T++5) to (-r++40)°C. In addition, the stretching ratio in the uniaxial direction is 2.
．． It is preferable to select from a range in which the area magnification is 5 times or more, especially 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. Furthermore, the heat setting temperature is 180-250'C, furthermore, 200-250'C.
It is recommended to select from the range of 30'C.

The biaxially oriented polyester film of the present invention is characterized in that it has extremely few voids compared to conventional films. The reason why the voids around these spherical silica particles are small is because the particles have a good affinity for polyester, and because the particles themselves are very similar to pearls, the stress of υ (for the particles) propagates evenly during stretching. It is presumed that this is due to stress on a part of the interface between the polyester and the particles, or the lack of binding.

In the present invention, by adding spherical silica particles whose particle size distribution is extremely sharp, the protrusions formed on the surface of the polyester film have extremely high uniformity.
A polyester film with the same heights of large and small protrusions can be obtained.

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness, excellent abrasion resistance, etc., and is characterized in that, for example, the amount of scratches, white powder, etc. generated is extremely small. This biaxially oriented polyester film can be widely used in various applications by taking advantage of these properties. For example, for magnetic recording such as video and audio.

When used as a base film for computers, etc., it provides excellent electromagnetic conversion properties, slipperiness, running durability, etc. Also, when used in capacitor applications, it has a low coefficient of friction,
Excellent windability, low crushing load, high transparency, etc. can be obtained. As mentioned above, this biaxially oriented polyester film is preferably used as a base film for magnetic recording media, especially as a base film for magnetic tapes, but is also suitable for use in electrical applications, packaging applications, vapor deposition films, etc. It can also be widely applied to other fields.

Furthermore, one or both sides of the film may be subjected to an adhesion treatment, for example, an adhesion layer coating, a corona treatment, or other surface treatment. The film may also contain a third component such as an antistatic agent, an ultraviolet absorber, and a coloring agent.

[Example] The present invention will be further explained below with reference to Examples.

In addition, various physical property values and characteristics related to the present invention were measured as follows.

(1) Particle size of spherical silica particles There are two conditions for measuring particle size:

1) When calculating the ratio of two average particle sizes from powder, etc. 2) When calculating the ratio of two average particle sizes of particles in a film, etc. (i) When using powder, place the powder on the electron microscope sample stage. Scatter the individual particles so that they do not overlap as much as possible, and form a thin gold film vapor deposited layer (200 to 300 layers thick) on the surface using a gold sputtering device.
Observe with a scanning electron microscope at a magnification of, for example, 10,000 to 30,000 times, and measure at least 100 particles' major axis (()Ii) and minor axis (Ds
i) and the equivalent diameter for area ([)i). The major axis (old), minor axis (Os), and average particle diameter (r5) of the silica particles are expressed by the number average value expressed by the following formula.

01=(Σ　Dli)/n.

i=1 Ds=(Σ()si)/n.

i=1 σ=〈 Σ Di)/n 1=1 (ii) For particles in a film A small piece of sample film was fixed on a scanning electron microscope sample stage and sputtered using a JEOL sputtering device (JrC).
The surface of the film is subjected to ion etching treatment using an ion sputtering device (Model 1100) under the following conditions.

In step 1, place the sample in the Pelger and
Raise the degree of vacuum to the vacuum state of Orr, and increase the voltage to 0.25kV.
, Current: 12.5 mAk: Perform ion etching for about 10 minutes. Furthermore, gold sputtering was applied to the film surface using the same equipment, and the film was observed using a scanning electron microscope at a magnification of 10,000 to 30,000 times. ),
Determine the minor axis (Dsi) and the area equivalent diameter ([)i).

The following steps are performed in the same manner as in (i) above.

(2) Particle size etc. of inorganic particles other than spherical silica particles 1) Average particle size
e Analyser). The particle size corresponding to 50 mass percent is read from the integrated curve of particles of each particle size and their abundance calculated based on the centrifugal sedimentation curve obtained by 1q, and this value is taken as the above average particle size (Bookr
"Particle Size Measurement Technology" published by Nikkan Kogyo Shimbun.

1975, 2, pp. 242-247).

2) Particle size ratio A small piece of the film is fixed and molded using an epoxy resin, and an ultra-thin section (cut parallel to the film flow direction) with a thickness of about 600 A is created using a microtome. The cross-sectional shape of the lubricant in the film was observed using a transmission electron microscope (Model 800 manufactured by El Ritsu Seisakusho) and expressed as the ratio of the long axis to the short axis of the lubricant.

3) Relative standard deviation value Measurement is performed in the same manner as for spherical silica, and for particles other than spherical, the volume is determined from the particle size ratio in the film thickness direction, and the particle size is determined by the diameter when using the isometric method. and calculate the relative standard deviation.

(3) The film surface roughness (Ra) is the value defined in JI&-80601 as the center line average roughness (Ra), and in the present invention, (Stylus type surface roughness i+ (StlRFCORDFR5E-30C
) Measure the item for use. The measurement conditions are as follows.

(a) Stylus tip radius = 2 μm (b) Measuring pressure: 30 mg (C) Cutoff 20.25 mm (d) Measuring length: 0.5 mm (e) How to summarize the data - Same sample was measured 5 times. , the largest value is 1
round off the last four digits of the average value of the remaining four data, and display up to the last three digits of the small number fish gear.

(4) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut into 1/2 inch width is held at an angle θ = (152/180) by a fixed rod (surface roughness 0.3 μm). ) 7r radial (152°)
and move (friction) at a speed of 200 cm/min. The outlet tension (T) when the tension controller is adjusted so that the inlet tension 1.1 becomes 50g.
2: g) is detected by an exit tension detector after the film has traveled 90 m, and the running friction coefficient μk is calculated using the following formula.

μk = (2,303/θ) to(1(T2/'T
+)=0.86810fJ (T2.150) (5)
Abrasion resistance The abrasion resistance of the running surface of the base film is evaluated using a 5-stage mini super calendar. The calendar is a 5-stage calender with nylon rolls and steel rolls, the processing temperature is 80℃, and the linear pressure applied to the film is 200 KMc.
m, film speed is 50 m/min. After running the running film for a total length of 2000 m, the abrasion resistance of the base film is evaluated based on the dirt that adheres to the top roller of the calendar.

4-level judgment> ◎ No stains on the nylon roll O Almost no stains on the nylon roll 50% white level signal (10
0% white level signal is peak-to-peak ◆The peak voltage is 0.
714 volts) with a 100% chroma level signal superimposed thereon, and the reproduced signal is measured using a Sivac noise meter Type 952R. The definition of chroma S/N is as follows according to Shibak's definition.

E S (p-p) Chroma S/N (dB) =20 to(]□E N (
rms) Here, E S (p-p) is the peak-to-peak voltage degree (1)-1) of the reproduced signal of the white level signal.

E S (p-1)) = 0.714V(1)-1)
) Furthermore, E N (rms) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

EN (rms) = AM noise effective value voltage m (7) Dropout Commercially available dropout counter (for example, Shihasoku VH
The dropout of 5 μsec xlodB is counted using OIB2 type) and the number of counts per minute is output.

(8) Slit the scratch judgment base film to a width of 172 inches and
) At the same time as measuring the friction coefficient of
The thickness of the scratch on the surface of the 1/2 inch IJ base film after running 0m and repeating this 50 times.
The depth and number were combined to determine the following five levels.

5-level judgment> ◎ No scratches are observed on the 172-inch base film.01 Almost no scratches are observed on the 72-inch base film.Δ Scratches are observed on the 1/2-inch IJ base film (several scratches) ×172 Several thick scratches are observed on the 1/2 inch wide base film.xx Many thick and deep scratches are observed on the 1/2 inch wide base film. The roll is wound up with min.

The end face deviation is graded as follows based on the distance of the end face deviation in the “1” direction.

Regarding symptomatic protrusions, the number of diseased protrusions with a major axis of 2 mm or more was counted and graded (f) as shown below.

Example 1 Dimethyl terephthalate and ethylene glycol were transesterified, manganese acetate was used as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, phosphorous acid was used as a stabilizer, and the average particle size was 0.19 μm as a lubricant.

Spherical silica with a particle size ratio of 1.07 and average particle size of 0.87 μm2
Using spherical silica with a particle size ratio of 1.16, polymerization was performed by a conventional method, and the intrinsic viscosity (orthochlorophenol, 35°C) was 0.
．． 62 polyethylene terephthalate was obtained.

The polyethylene terephthalate pellets are melted at a melting temperature of 280 to 300°C, and the molten polymer is passed through a 1 mm slit die to the surface. temperature 20
Formed and extruded on a rotating cooling drum of 'C' to obtain an unstretched film.

The unstretched film thus obtained was preheated at 75°C, and further heated between low speed and high speed rolls with an IR heater at a surface temperature of 850°C from 12 mm above.
Stretched twice, rapidly cooled, and then fed to a stenter to 110
It was stretched 3.8 times in the transverse direction at 'C.

The obtained biaxially oriented film was heat set at a temperature of 210° C. for 5 seconds to obtain a heat set biaxially oriented film having a thickness of 15 μm.

Furthermore, on this film, 100 parts by weight of Co-containing iron oxide powder having the following composition: 10 parts by weight of ESLETSUKU A (vinyl chloride-vinyl acetate copolymer manufactured by Block Chemical Co., Ltd.) 10〃 Nitsuporan 2304 (polyurethane elastomer manufactured by Nippon Polyurethane Co., Ltd.) 10〃 Coronate L (Japan Polyurethane Co., Ltd.) polyisocyanate) 5 Lecithin
1-fold omega-part methyl edyl ketone 15 methyl isobutyl ketone
75〃Toluene 1
5〃Additives (lubricant, silicone resin>0.15
Apply magnetic paint consisting of tt using a gravure roll, smooth the magnetic paint layer using a doctor knife,
While the magnetic paint has not yet froze, it is magnetically oriented using a conventional method, then introduced into an A-bun for dry curing, further calendered to make the coated surface uniform, and slit to form a magnetic layer with a thickness of approximately 5 μm. A magnetic tape having a width of 172 inches was prepared. The properties of this film and magnetic tape are shown in Table 1.

In this way, the film and magnetic tape are
The winding coefficient was low, and when wound at a high speed of 300 m/min, there was little deviation of the end face and the winding appearance was good, and the calendering resistance and scratch resistance were also good.

Examples 2 to 4 Films and magnetic tapes were produced in the same manner as in Example 1, except that the spherical silica used was changed as shown in Table 1.

The properties were good as shown in Table 1.

Comparative Examples 1 to 3 In Example 1, kaolin, titanium oxide,
Alternatively, a film and a magnetic tape were prepared in the same manner as in Example 1 except that calcium carbonate and titanium oxide were used. The properties are shown in Table 1, and none of them were good.

In Comparative Example 1 using kaolin with an average particle size of 0.65 μm, the scratch resistance was poor, and in Comparative Example 2 using titanium oxide with an average particle size of 0123 μm, the film winding appearance was poor during wide IJ and high speed winding. Furthermore, in Comparative Example 3, which used calcium carbonate with an average particle size of 0.9 μm and titanium oxide with an average particle size of 0.23 μm, the calendering property was not good.

Claims (1)

[Claims] 1. In the polyester, as the first component, the average particle size is 0.
03 μm or more and less than 0.3 μm and the particle size ratio (longer diameter/
Spherical silica particles with a minor axis of 1.0 to 1.2
Contains 1 to 2.5% by weight, and has an average particle size of 0.6 to 3 μm as a second component, and a particle size ratio (major axis/breadth axis) of 1.
．． A biaxially oriented polyester film, characterized in that it contains 0 to 1.2 spherical silica particles in an amount within the range of 0.002 to 2% by weight, and in an amount equal to or smaller than that of the first component. 2. The biaxially oriented polyester film according to claim 1, wherein the spherical silica particles have a relative standard deviation expressed by the following formula of 0.5 or less. Relative standard difference = ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Where, Di: Area circle equivalent diameter of individual particles (μm) @D
@: Average value of area circle equivalent diameter ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (μm) n: Represents the number of particles.