JPS63235340A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain the title flat film excellent in lubricity, chipping resistance, etc. and suitable for videotapes, etc., by forming a polyester homoginously containing specified amounts of two kinds of spherical silica particles of different particle diameters into a film and biaxially stretching this film. CONSTITUTION:A polyester containing 0.01-2.5wt.% spherical silica particles, as a first component, of an average particle diameter of 0.05-0.5mum and a particle diameter ratio (major diameter/minor diameter) of 1-1.2 and 0.005-2wt.% (<= the amount of said first component) spherical silica particles, as a second component, of an average particle diameter which is larger than that of said first component by at least 0.1mum and is in the range of 0.15-0.6mum is produced. This polyester is formed into a film, and this film is biaxially stretched to obtain the purpose biaxially oriented polyester film. In this way, a film low in a content of voids and highly uniform in a distribution of protrusions formed on the surface can be obtained.

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. Concerning an excellent biaxially oriented polyester film.

[Prior Art] Because of its excellent properties, biaxially stretched polyester films are widely used in many applications such as magnetic tapes, electricity, photography, metallization, and packaging. In particular, because of its properties such as high strength and modulus, magnetic recording media, such as video tapes.

Widely used as a base film for 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 becomes flat, the winding appearance of the film in the process of winding the film into a roll deteriorates significantly, and there is a problem that it is difficult to obtain a film roll with a good winding appearance.

Defects in the winding appearance of the film roll include (1) bump-like protrusions on the roll, and (2) wrinkles in the longitudinal direction of the film. ■When the edge surface shifts, etc., ■ is when the film has poor slipperiness, ■: when the film is wound with high tension to prevent bump-like protrusions, ■: when the film is rolled up when flat film is rolled up. Each of these tends to occur when the air space created in between becomes difficult to escape.

Therefore, the base polyester film is required to have not only flatness but also excellent slipperiness and air escape properties in order to obtain a good film winding appearance.

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, but on the other hand, due to the roughening, for example In media applications, the surface after applying the magnetic paint tends to become rough, and the electromagnetic conversion characteristics tend to deteriorate.

As one of the measures to solve these contradictory problems of flatness and slipperiness, many methods have been proposed that utilize composite inorganic fine particles in which large-sized particles and small-sized particles coexist.

However, these methods also have problems, and it is difficult to meet the demands for higher grades of magnetic recording media, such as higher density and higher quality.The reason for this is that the large particles used in composite inorganic particles The size of the grains is coarse compared to the quality required for high-grade grades, and the larger the grains, the higher the protrusions on the film surface, which deteriorates the electromagnetic conversion characteristics in magnetic recording media applications. In addition, the larger the particles are, the higher the protrusions on the film surface and the larger the voids surrounding the particles.High protrusions are removed during the cleaning process with nonwoven fabric or the calendering process during the magnetic tape manufacturing process. This can cause dropouts (parts where information is missing during recording and playback), and it can also cause calendar stains during the processing process and dust fabric stains for cleaning the base film surface, which can damage the magnetic recording medium. This would greatly impair its characteristics.

[Object of the Invention] The present inventor has solved the above-mentioned problems, and has created a film that has both flatness and good film winding shape applicable to the field of high-quality magnetic recording applications, and also has good abrasion resistance. As a result of intensive research to develop the film, we found that by sharpening the shape of the protrusions on the film surface and using a specific combination of large particles and small particles, even if the film surface is flat, it has great slipperiness, air escape properties, and abrasion resistance. In order to sharpen the shape of the protrusions, it is most preferable that the particles present in the film be spherical.There are many particles that are close to spherical, including glass peas. discovered that it is difficult to obtain a film that satisfies the surface properties especially for video tapes, and that it is possible to obtain a film that satisfies the above properties by using specific spherical Sicari particles in combination with large particles and small particles, We have 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.
An object of the present invention is to provide a biaxially oriented polyester film having excellent abrasion resistance and the like.

[Configuration and Effects of the Invention] According to the present invention, an object of the present invention is to
As the first component, spherical silica particles having an average particle diameter of 0.05 to 0.5 μm and a particle size ratio (major axis/minor axis) of 1.0 to 1.2 are used in an amount of 0.01 to 2.5 jl. %, and as a second component, the average particle diameter is in the range of 0.1 μm or more thicker than the first component, 0.15 μm or more and less than 0.6 μm, and the particle size ratio (major axis / short axis) is 1.0 ~ 1.2 is achieved by a biaxially oriented polyester film characterized by containing spherical silica particles in an amount within the range of 0.005 to 2.0% by weight, which is the same as or less than the first component. .

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 alkylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, and alicyclic glycols such as cyclohexane dimetatool. Diols and the like can be mentioned.

In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as main constituents 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 preferable, in which case the dicarboxylic acid that is 20 mol% or less of the total acid component is It can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or 2,6-naphthalenedicarboxylic acid, and also, for example, aliphatic dicarboxylic acids such as adipic acid, cepacic acid, etc.; such as cyclohexane-1,4-dicarboxylic acid. It can be an alicyclic dicarboxylic acid or the like.

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. Aliphatic diols containing an aromatic ring such as 1,4-dihydroxymethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, poly10-pyrene glycol, polytetramethylene glycol, etc. can also be used.

Furthermore, in the polyester used in the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as droxybenzoic acid; an aliphatic oxyacid such as ω-hydroxycaproic acid, 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.

Furthermore, the polyester in the present invention contains a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimelli-ytoic acid, in an amount within a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component. , bentaerinlitol, etc. are also included.

The above-mentioned polyester is known per se and can be produced by a method known per se.4 The above-mentioned polyester is 35% as a solution in 0-chlorophenol.
Preferably, it has an intrinsic viscosity of about 0.4 to about 0.8 as measured at °C.

The biaxially oriented polyester film of the present invention has a large number of Sa dark blue protrusions on the film surface.

According to the invention, these large numbers of fine 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 a specific time. Preferably, 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 that are extremely close to true spheres, and the silica particles conventionally known as lubricants are either ultra-fine podium particles of about 10 mμm, or aggregated particles of about 0.5 μm. It is characterized by a marked difference from the formation of aggregates (agglomerated particles).

If the particle size ratio becomes too large, the void ratio becomes large, which is undesirable because the machinability deteriorates, and
These spherical silica particles have an average particle size of 0.0 as the first component.
5 to 0.5 μm, preferably 0.05 to 0.4 μm, more preferably 0.05 to 0.3 μm, and a second component with an average particle size of 0.15 μm or more and less than 0.6 μm, preferably 0. .2 μm or more and less than 0.6 μm.

More preferably 0.3 to 0.5 μm, particularly preferably 0
．． There are two types: one with a diameter of 4 to 0.5 μm. 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 from the second component will become small, resulting in poor air escape properties. This is not preferable because the effect of improving the film winding appearance (edge misalignment) becomes insufficient.

Also, the difference in average particle size between the first component and the second component is 0.1μ
m or more, preferably 0.15 μm or more, more preferably 0.20 μm or more. If the difference in average particle size between the first component and the second component is too small, air escape performance will be poor, end face deviation will easily occur during film winding, and the film winding appearance will be poor, which is not preferable.

Here, the major axis and minor axis of the spherical silica particles are determined using an electron microscope, for example, after depositing metal on the particle surface.
It is determined from an image magnified 30,000 to 30,000 times, and the average particle size 9 grain size ratio is determined by the following formula.

Average particle diameter = sum of area circle-equivalent diameters of measured particles / ratio of several particle diameters of measured particles = average major diameter of silica particles / average minor diameter of the particles Also, it is preferable that the spherical silica particles have a sharp particle size distribution. , the relative standard deviation representing the steepness of the distribution, or 0.
It is preferably 5 or less, more preferably 0.3 or less, particularly 0.15 or less.

This relative standard difference is expressed by the following formula.

Relative standard deviation - where, D;: Area circle equivalent diameter of individual particles (μm) D=
Average diameter equivalent to sum of surface areas (=(Σ Di)/nl (μm) i=1 n: represents the number of particles measured.

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. Also, in this case, the first
The average particle size of the component and the average particle size of the second component are at least 0.
．． Since there is a difference of 1 μm, the particle size distributions of the first component and the second component do not substantially overlap each other. Spherical silica particles are not limited in any way to their manufacturing method or other aspects as long as they satisfy the above conditions.For example, spherical silica particles are produced by hydrolysis of ethyl orthosilicate [3i (OC2H!1) a ]. It can be manufactured by creating silica [5i(O)[)a] monodisperse spheres, and then dehydrating this hydrous silica monodisperse region to three-dimensionally grow silica bonds [;S 1-0-311. (Journal of the Chemical Society of Japan 81. Hase 9. P, 1
503).

S i (OC2H!l) a +48z O→ S
t (O)() a + 4 Cz
H50H;S1-OH+HO-31: →:=S1-o-st=+HtomiO In the present invention, the amount of spherical silica particles added as the first component is 0.01 to 2.5 to the polyester. % by weight, preferably 0.05-2.0% by weight, more preferably 0.05-1.0% by weight, particularly preferably 0.1-2.0% by weight.
0.5. f! :Amount%. Further, the amount of spherical silica particles added as the second component is o, o
os ~2.0% by weight, preferably 0.01-1.5% by weight, more preferably 0.02-1.0% by weight, particularly preferably 0.04-0.4% by weight First of all
It is the same as the component or less than 1. Of these, the first ingredient!
The following is preferable; if the amount of the first component added is less than 0.01% by weight and the amount of the second component added is less than 0.005% by weight, the effect of improving slipperiness and abrasion resistance is insufficient. In addition, the total amount of the first component and second component added is 0.015~
3.0% by weight, preferably 0.02-2.0% by weight, more preferably 0.04-1.011j1%, particularly preferably 0.06-0.3% by weight. If the total amount added exceeds 3.0% by weight, surface flatness will deteriorate, which is not preferable.

The biaxially oriented polyester film of the present invention can be produced in accordance with conventional methods for producing biaxially oriented films. The unstretched film is then stretched in the two-wheel direction, heat set, and if necessary subjected to relaxation heat treatment. At this time, the film surface characteristics vary depending on the particle size of the spherical silica particles and the stretching conditions, so they are appropriately selected from conventional stretching conditions. In addition, the density, heat shrinkage rate, etc. change depending on the temperature, magnification, speed, etc. during stretching and heat treatment, so the conditions that satisfy these characteristics at the same time are determined. Temperature (T1) is in the range of (Tg-10) to (Tg+, 45)'C (where Tg: glass transition temperature of polyester),
The second-stage stretching temperature (for example, the lateral direction stretching temperature 2T2) is (T
It is preferable to select from the range of 1+5) to (Tt+40)'C, and the stretching ratio in the uniaxial direction is 2.5 or more, especially 3 times or more, and the area ratio is 8 times or more, especially 10
The heat setting temperature is preferably selected from a range of 180 to 250°C, more preferably 200 to 230°C.

The biaxially oriented polyester film of the present invention is characterized by extremely small voids compared to conventional films. The reason why the voids around the spherical silica particles are small is that the particles have a good affinity for polyester, and the particles themselves are very close to true spheres, so the stress around the lubricant propagates evenly during stretching, and the polyester This is presumed to be due to the fact that stress is not concentrated on a part of the particle interface.

In the present invention, by adding spherical silica particles with an extremely sharp particle size distribution in advance, the distribution of the protrusions formed on the surface of the polyester film is extremely uniform, and the heights of the large and small protrusions are uniform. A polyester film is obtained.

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness, and excellent abrasion resistance, and is characterized by significantly less generation of scratches, white powder, etc. Taking advantage of these characteristics, this biaxially oriented polyester film can be used in a wide variety of applications, including aX recording, video, audio, etc.
When used as a base film for computers, etc., excellent ta conversion characteristics, slipperiness, running durability, etc. can be obtained. 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 not limited thereto, and can be used for electrical applications, packaging applications, and deposition films. It can be widely applied to other fields such as Furthermore, one or both sides of the film may be subjected to an adhesion treatment, such as an adhesion layer coating or a corona treatment, and the film may be coated with an antistatic agent.

A third component such as an ultraviolet absorber 1 and a coloring agent may be included.

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

Note that various physical property values and characteristics in the present invention were measured as follows.

(1) Particle size of spherical silica particles There are the following conditions for particle size measurement.

1) When determining the average particle size, particle size ratio, etc. from powder 2) When determining the average particle size, particle size ratio, etc. of particles in a film.

(1) In the case of a powder book, the powder book is scattered on an electron microscope sample table so that the individual sperm do not overlap as much as possible, and a thin gold film is deposited on the surface using a gold sputtering device to a thickness of 200 to 300 people. Observe with a scanning electron microscope at a magnification of, for example, 10,000 to 30,000 times, and measure the major axis (Dli), minor axis (Dsi), and area of at least 100 particles using Luzex 500 manufactured by Nippon Regulator ■. Find the equivalent diameter (Di).

Then, with the number average value expressed by these following formulas,
It represents the major axis (DI), minor axis (Ds>, and average particle diameter (D)) of the silica particles.

n
nDI=(Σ D Ii) /n, D s = (Σ
Dsi)/n.

i=1 i=1 D=(ΣD i ) / n 1=1 (It) In the case of particles in a film, a small piece of sample film was fixed on a scanning electron microscope sample stage and sputtered using a sputtering device manufactured by JEOL ( JFC-110
Ion etching is performed on the film surface under the following conditions using a 0-type ion bath/tarling device. Under the 0 condition, the sample is placed in a Pel jar and the temperature is approximately 10°3 Torr.
Raise the degree of vacuum to a vacuum state of 0.25K V,
Current: 12.511A4: Perform ion etching for about 10 minutes. Furthermore, gold sputtering was applied to the surface of the film using the same equipment, and the film was observed under a scanning electron microscope at a magnification of 10,000 to 30,000 times.
0, the major axis (Dli), minor axis (DSi), and area equivalent diameter <Di) of at least 100 particles are determined. The following steps are performed in the same manner as (+) above.

(2) Particle size of particles other than silica particles, etc. 1) Average particle size Shimadzu manufactured rupture CP-SO type centrifugal particle size analyzer
Particle 5ize Analyzer
), and 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 obtained centrifugal sedimentation curve, and this value is calculated based on the above average particle size. (see Bookr Particle Size Measurement Techniques J, published by Nikkan Kogyo Shimbun, 1975, pp. 1, 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 approximately 600 mm is prepared using a microtome. The cross-sectional shape of the lubricant (particles) in the film was observed using a transmission electron microscope (manufactured by Hitachi, Ltd., model H-800) and expressed as the ratio of the long axis to the short axis of the lubricant.

3) Relative standard deviation value Measure in the same manner as for silica particles, and for particles other than spherical, calculate the volume from the particle size ratio of the particles in the film thickness direction, and define the particle size as the diameter when it is made into a uniform sphere. ,
Calculate the relative standard deviation value.

(3 Film surface roughness Ra) This is the value defined in JIS-BO601 as the center line average roughness Ra), and in the present invention, a stylus type surface roughness meter (SURFCORDERSE-30C) from Koita Research Institute is used. Measure. The measurement conditions are as follows.

(a) Stylus tip radius: 2μm (b) Measurement pressure: 30cm (C) Cutoff: 0.25cm (d) Measurement length
: 0.5m+ (e) How to summarize the data - Measure the sample 5 times and set the largest value as 1
The average value of the remaining four data is rounded off to the fourth decimal place and displayed to the third decimal place.

(4) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut to a width of 1/2 inch was held on a fixed rod (surface roughness: 0.3 μm) at an angle θ = (152
/18G) π radian (152@) and 2 per minute
Incoming tension T that moves (friction) at a speed of 003
When the tension controller is adjusted so that 1 is 50 g, the exit tension (Tz: g) of the film is 9.
After traveling 0m, the exit tension detector detects the tension and calculates the running wear coefficient μk using the following formula.

tt k = (2,303/θ) l0fl (T
2/TI)-0,86810! J(Tz 150
) (5) Scrapability The scratchability of the running surface of the base film was evaluated using a 5-stage mini super calendar. The calendar is a 5-stage calendar with nylon rolls and steel rolls, the processing temperature is 80'C, and the linear pressure applied to the film is 200 kg.
/all, the 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 was evaluated based on the dirt that adhered to the top roller of the calendar.

4-level evaluation: ◎: No stains on the nylon roll ○: Almost no stains on the nylon roll 50% white level signal (10
The 0% white level signal has a peak:to:peak voltage of 0.
714 volts), record a signal with a 100% chroma level signal superimposed, and measure the reproduced signal using a Shibaku noise meter type 952R.
The definition of chroma S/N is as follows according to Shibak's definition.

ES (D-D) Roma s/N (dB) = 201°EN (rms) Here, ES (p-p) is the peak voltage level (D-1) of the reproduction signal of the white level signal. )).

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

EN (rlms) = AM noise effective value voltage (V) (7
) Dropout Commercially available dropout counter (e.g. Shibatsu VI
5) Count the dropouts of tsec x 10dB using the IOIBZ type) and calculate the number of counts per minute.

(8) Slit the scratch judgment base film into 1/2 inch pieces and
) At the same time as measuring the friction coefficient of
After running 0 m and repeating this process 50 times, the thickness, depth, and number of scratches on the surface of the 1/2 inch wide base film are comprehensively judged in the following five stages.

5-level judgment> ◎ No scratches are observed on the 172 inch wide base film. 0 Almost no scratches are observed on the 1/2 inch wide base film. Δ Scratches are observed on the 1/2 inch wide base film (how many). × Several thick scratches are observed on the 172 inch wide base film. Many thick and deep scratches are observed on the entire surface of the XXL/2 inch wide base film. The roll is wound up at a speed of 1/min, and the appearance of the roll is carefully inspected and graded from 1st grade to 5th grade.

The end face misalignment is graded as follows based on the distance of the end face misalignment in the width direction.

Regarding lump-like protrusions, the number of layered protrusions with a major diameter of 2 km or more is counted and graded as follows.

Example 1 Dimethyl terephthalate and ethylene glycol were transesterified, manganese acetate was used as a transesterification catalyst, antimony dioxide was used as a polymerization catalyst, hypophosic acid was used as a stabilizer, and the average particle size was 0.14 μm as a lubricant.

Spherical silica with a particle size ratio of 1.03 and average particle size of 0.42 μm1
Polymerize using a conventional method using spherical silica with a particle size ratio of 1.05, and the intrinsic viscosity (orthochlorophenol, 35'C)
0.62 of polyethylene terephthalate was obtained.

This polyethylene terephthalate pellet was heated to 170°C.
, after drying for 3 hours, fed to the extruder hopper, melting temperature 28
The molten polymer is melted at 0 to 300°C and 1 +w+
It was extruded through a slit-shaped die onto a rotating cooling drum with a surface temperature of 20°C to obtain an unstretched film.

The unstretched film thus obtained was preheated at 80°C, and further rolled between low speed and high speed rolls from above 15 degrees Celsius.
It was heated with an IR heater with a surface temperature of 0° C. and stretched to 3.6 times, rapidly cooled, and then supplied to a stenter and stretched at 105° C. to 3.8 times in the transverse direction. The obtained biaxially oriented film was heat-set at a temperature of 210°C for 5 seconds to a thickness of 15 μm.
A heat-set biaxially oriented film was obtained.

Furthermore, on this film, 100 parts by weight of CO-containing Chichichi Oxide powder with the following composition: S-LEC A (vinyl chloride-vinyl acetate copolymer manufactured by Tsukisui Chemical Co., Ltd.) lQn Nizuborane 2304 (polyurethane elastomer manufactured by Nippon Polyurethane Co., Ltd.) 10 parts by weight! Polyisocyanate made by Coronate Nippon Polyurethane) 5 No! Lecithin l nMethyl ethyl ketone 754) Methyl isobutyl ketone 7514 Toluene
Apply a magnetic paint consisting of 0.15 II additives (lubricant, silicone resin) with a gravure roll, smooth the magnetic paint layer with a doctor knife, and perform magnetic orientation by a conventional method while the magnetic paint is still dry. After drying and curing the tape in the open, it is calendered to make the coated surface uniform and slit to create a 1/2 inch magnetic tape with a magnetic layer about 4μ thick. did.

The properties of this film and magnetic tape are shown in Table 1.

The film thus obtained had a low surface roughness Ra, a low coefficient of friction, a good winding appearance when wound into a roll, and good calender abrasion properties.

Furthermore, the electromagnetic conversion characteristics after processing into magnetic tape.

Characteristics such as dropout (Dlo) were also good.

Example 2 Films and tapes were produced in the same manner as in Example 1, except that the average particle diameter of the spherical silica used and the amount added were varied as shown in Table 1.

The properties were good as shown in Table 1.

Comparative Examples 1 to 4 Films and tapes were created in the same manner as in Example 1 except that kaolin and calcium carbonate were used as particles.

The properties are shown in Table 1, but none of them were good.

Procedural amendment dated July 2, 1986! F Temple 3 Go Director '■ Beating 1, $ Kaiki Patent Application No. 62-69143 2, Name of the invention Biaxially oriented polyester film Confucianist Okamoto Sashibe (1) ro, 3rd line from the bottom of page 13 of the specification. 15" should be corrected to ro, 12".

(2) In the third line from the bottom of page 30 of the same book, it says, ``Change J. Correct.

(3) Add the following sentence after the third line from the bottom of page 32.

Example 3 Films and tapes were produced in the same manner as in Example 1, except that the average particle diameter of the spherical silica used and the amount added were changed as shown in Table 2.

The properties were particularly excellent as shown in Table 2.

Claims (1)

[Claims] 1. As the first component in polyester, the average particle size is 0.0.
Spherical silica particles having a diameter of 5 μm to 0.5 μm and a particle diameter ratio (major axis/breadth axis) of 1.0 to 1.2 are 0.01 to 2.
5% by weight, and as a second component, the average particle size is 0.1 μm or more larger than the first component and 0.15 μm or more 0.6 μm.
Particle size ratio (major axis/minor axis) is 1.0.
A biaxially oriented polyester film, characterized in that it contains spherical silica particles having a molecular weight of 0.005 to 2.0% by weight, which is the same as or less than 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. {√[■＾n_i_=_1(Di-@D@)＾2]/n
/@D@Here, Di: Diameter equivalent to area circle of each particle (μm) @D@: Average value of equivalent area circle diameter {=(Σ^n_i_=_1Di)/n} (μm) n: Number of particles represents.