JPH0859973A - Polyester film - Google Patents

Abstract

PURPOSE: To prepare a biaxially oriented polyester film capable of satisfying both slipperiness and scrape resistance. CONSTITUTION: This polyester film contains 0.005-2wt.%. silicone resin fine particles based on the weight of the polyester. The silicone resin fine particles have 0.05-3μm average particle diameter, consist of bond units expressed by the formula RSiO3/2 (R is a 1-6C alkyl or phenyl) and are treated by a silane coupling agent on their surfaces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film containing silicone resin particles dispersed therein. More specifically, the silicone resin particles are well dispersed in polyester, and are biaxially oriented with excellent smoothness and abrasion resistance. Regarding polyester film.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films are used for various purposes, especially for magnetic recording media because of their excellent physical and chemical properties.

In the biaxially oriented polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and processing process and the product quality. If these are insufficient, for example, when a magnetic layer is applied to the surface of a biaxially oriented polyester film and used as a magnetic tape, friction and abrasion between the coding roll and the film surface are severe, and wrinkles and scratches on the film surface are likely to occur. Even when it is used for a VTR or a data cartridge, friction is generated between many guide parts, a reproducing head, etc. during pulling out from a cassette, winding, and other operations, causing scratches, distortion, and even a base film. The generation of white powder due to scraping of the surface often causes dropout.

Many investigations have been made to solve these problems. Among them, the method of adding fine silicone resin particles (for example, Japanese Patent Laid-Open No. 62-172031) has a great improvement effect and is expected to develop as these technologies. It

However, even in such a method,
Under the harsh conditions such as high-speed processing for improving productivity such as magnetic layer coating or calendar process in recent video tape manufacturing process, high-speed dubbing of soft tape, and repeated running and rewinding Problems such as an increase in the amount generated are newly pointed out.

[0006]

To solve these problems, the present inventors have earnestly studied to develop silicone resin fine particles capable of greatly improving the abrasion resistance while maintaining stable slipperiness in the film. As a result, they have found that the inclusion of silicone resin fine particles surface-treated with a silane coupling agent in a polyester film can realize stable slipperiness and good abrasion resistance, and arrived at the present invention.

[0007]

That is, the present invention has an average particle size of 0.05 to 3 μm, 80% by weight or more of the particles are composed of a bonding unit represented by the following formula, and the particle surface has a silane cup. The silicone resin fine particles treated with the ring agent are added in an amount of 0.0
The polyester film is characterized in that it is contained in an amount of 05 to 2% by weight.

[0008]

Embedded image RSiO _3/2 (wherein R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group.) The polyester in the present invention is an aromatic dicarboxylic acid-based acid component. And is a polyester having an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film-forming properties, especially melt-forming film-forming properties. Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, anthracenedicarboxylic acid. Etc. can be mentioned. Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and alicyclic compounds such as cyclohexanedimethanol. Examples thereof include diols.

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

Among such polyesters, especially polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, A copolymer in which 80 mol% or more of all glycol components is ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. A cycloaliphatic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Further, 20 mol% or less of the total glycol component may be the above-mentioned glycol other than ethylene glycol, and aromatic diols such as hydroquinone, resorcin, and 2,2-bis (4-hydroxyphenyl) propane, 1, An aliphatic diol having an aromatic ring such as 4-dihydroxydimethylbenzene, polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can also be used.

The polyester of the present invention includes
Aromatic oxyacids such as hydroxybenzoic acid, ω-
Those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid is copolymerized or bonded in an amount of 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component are also included.

In the present invention, the silicone resin fine particles contained in the polyester have the following formula:

[0013]

Embedded image of a silicone resin having 80% by weight or more of bonding units represented by RSiO _3/2 (wherein R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group). It is a particle.

The above-mentioned bonding unit means the following structural formula.

[0015]

[Chemical 4]

Here, R is the same as above.

A method for producing the above-mentioned silicone resin fine particles is known, and for example, a method of hydrolyzing and condensing an organotrialkoxysilane (for example, Japanese Examined Patent Publication No. 40-14917 or Japanese Examined Patent Publication No. 2-22767) or methyltrichlorosilane is used. Method for producing fine particles of polymethylsilsesoxane as a raw material (for example, Belgian patent 572412)
No.) etc. However, the production method is not limited in the present invention, and silicone resin fine particles produced by any method may be used.

R in the above formulas [Chemical Formulas 1 to 3] and structural formula [Chemical Formula 4] is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group, and the alkyl group is, for example, a methyl group, Examples thereof include ethyl group, propyl group, butyl group, pentyl group and hexyl group. These can be one or more. When R is a plurality of groups, for example, when it is a methyl group and an ethyl group, it can be obtained by producing a mixture of methyltrimethoxysilane and ethyltrimethoxysilane as a starting material. However, considering the manufacturing cost and the ease of the synthesis method, the silicone resin (polymethylsilsesquioxane) fine particles in which R is a methyl group are preferable.

The silicone resin fine particles preferably have a substantially spherical shape, and in this case, they are effective in imparting slipperiness.

In the present invention, it is necessary to surface-treat the silicone resin fine particles with a silane coupling agent, and the surface treatment greatly improves the abrasion resistance.

Examples of the silane coupling agent include N-β (aminoethyl) γ-, which is an amino silane such as vinyltriethoxysilane having an unsaturated bond, vinyltrichlorosilane, and vinyltris (β-methoxyethoxy) silane.
Aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ
-Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and other epoxy-based β
(3,4-Epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, etc. -Methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, and further γ-mercaptopropyltrimethoxysilane, γ-chloro Examples include propyltrimethoxysilane and the like. Of these, epoxy-based silane coupling agents are preferable because of their ease of handling, difficulty in coloring when added to polyester, and great effect of abrasion resistance.

The surface treatment with the silane coupling agent is carried out by filtering the silicone resin fine particle slurry (water slurry or organic solvent slurry) immediately after synthesis with a filter or a centrifuge to separate the silicone resin fine particles, and before drying. It is a practical method to re-slurry the silane coupling agent with water or an organic solvent in which the silane coupling agent is dispersed, to separate the fine particles again after the heat treatment, and then to dry the separated fine particles, and to further perform heat treatment depending on the type of the silane coupling agent. Although preferred, the once dried silicone resin fine particles may be reslurried by the same method, and the treatment method is not particularly limited.

One of the mechanisms by which the silicone resin fine particles surface-treated with the silane coupling agent in the present invention prevent the generation of white powder and the like and improve the abrasion resistance is, for example, the starting raw material components or the like in the silicone resin fine particles. Unreacted substances such as hydrolyzed products of organotrialkoxysilane, which is one of the raw materials, or terminal silanol groups in the silicone resin are chemically bonded to the silane coupling agent to stabilize them, It has a poor affinity with polyester due to the prevention of the effect of uneven distribution or escape of these substances on the film surface, which occurred during the treatment, and the adsorption of the silane coupling agent on the particles. It seems that the affinity of fine particles of silicone resin is improved, the fine particles fall off due to abrasion, and the polyester around the fine particles White powder generation, such as abrasion dust is thought whether not to be pressing.

The average particle diameter of the silicone resin fine particles in the present invention is 0.05 to 3 μm, preferably 0.3 to
It is 2.0 μm. If the average particle size is less than 0.05 μm, it is difficult to obtain the effect of improving the sliding property and the abrasion resistance, while the average particle size of 3 μ
When it exceeds m, it is difficult to obtain surface flatness, which is not preferable. Further, it is preferable that the silicone resin fine particles have a spherical particle shape because it is effective in imparting slipperiness.

The addition amount of the silicone resin fine particles in the present invention is 0.05 to 2% by weight based on the weight of polyester. If the amount added is too small, slipperiness deteriorates, while if the amount added is too large, problems such as insufficient dispersibility in the polymer occur.

In the present invention, the silicone resin fine particles may be used alone, or may be used in combination with other fine particles, that is, other organic fine particles and / or inert inorganic particles. Other organic fine particles include crosslinked polystyrene fine particles, crosslinked acrylic resin fine particles, melamine resin fine particles and the like, and the inert inorganic fine particles include aluminum oxide, titanium oxide, silicon oxide, zirconium oxide, calcium carbonate, kaolin, clay and carbon. Black etc. can be illustrated. The aluminum oxide may have various crystal forms, but α
-Type, γ-type, δ-type, θ-type, κ-type aluminum oxide is preferable, and γ-type, δ-type and θ-type aluminum oxide is particularly preferable.

The other fine particles used in combination with the silicone resin fine particles preferably have an average particle diameter of 0.05 to 2 μm. Also, the combined amount is based on the weight of polyester.
It is preferably 0.01 to 2% by weight.

In the present invention, the silicone resin fine particles may be dispersed and contained in the polyester at any time, but in the polyester production process, for example, an esterification step of a direct polymerization method using terephthalic acid or 2,6-naphthalenedicarboxylic acid as a raw material, Alternatively, a transesterification step of a transesterification method using dimethyl terephthalate or dimethyl-2,6-naphthalenedicarboxylate as a raw material is preferable, and when the polyester composition not containing the fine particles is remelted, the powder of the fine particles is directly added. A polyester composition may be added to the composition, or a method in which the fine particles are directly added as a powder when a film is produced using polyester may be used. However, as the timing of adding the fine particles becomes late, it is necessary to increase the kneading share of the melt extruder in order to secure the dispersibility of the fine particles in the film.

A conventionally known method can be applied to the production of a film using the polyester of the present invention. For example, it can be produced by melt-extruding polyester and quenching it to obtain an unstretched film, then stretching the unstretched film biaxially, heat-setting, and if necessary, relaxation heat treatment. At this time, the surface characteristics, density, heat shrinkage rate, and other properties of the film change depending on the stretching conditions and other manufacturing conditions, and are appropriately selected as necessary.

For example, the unstretched film is uniaxially (longitudinal or transverse) in the range of [Tg-10] to [Tg + 6].
At a temperature of 0] ° C. (however, Tg: glass transition temperature of polyester), the film is stretched at a draw ratio of 2.5 times or more, preferably 3 times or more, and then Tg to [Tg] in a direction perpendicular to the drawing direction.
It is preferable to stretch at a temperature of +70] ° C. at a draw ratio of 2.5 times or more, preferably 3 times or more. Further, if necessary, it may be re-stretched in the machine direction and / or the transverse direction. In this way, the total draw ratio is preferably 9 times or more, more preferably 12 to 35 times, and more preferably 15 to 15 times as the area draw ratio.
25 times is particularly preferable. Furthermore, the biaxially stretched film can be heat-set at a temperature of [Tg + 70] ° C. to [Tm-10] ° C. (however, Tm: melting point of polyester), for example, at 180-250 ° C. Preferably. The heat setting time is preferably 1 to 60 seconds.

The polyester film of the present invention is excellent in stable slipperiness and abrasion resistance, and is particularly useful as a base film for magnetic recording media.

[0032]

EXAMPLES The present invention will be described in detail below with reference to examples. Also,
Various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Average particle size of particles (d) (i) Obtaining average particle size from granular material Shimadzu CP-50 type Centrifugal particle size analyzer (Centrifugal Particle S
The particle size corresponding to 50 mass% is read from the integrated curve of the particle size calculated based on the centrifugal sedimentation curve obtained using ize Analyzer) and the abundance of particles having that particle size, and this value is averaged as above. The particle size is defined as the volume ("Particle size measurement technology" published by Nikkan Kogyo Shimbun, 1975, pages 242-24).
7).

(Ii) In the case of particles in the film: A small piece of the sample film is fixed on a sample stand for a scanning electron microscope, and a sputtering device (JFC-made by JEOL Ltd.) is used.
1100 type ion etching apparatus) is used to perform ion etching treatment on the film surface under the following conditions. The condition is that the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, the voltage is 0.25 kV, and the current is 1
Perform ion etching at 2.5 mA for about 10 minutes. Further, gold sputtering is applied to the film surface with the same apparatus, and it is observed with a scanning electron microscope from 50,000 to 10,000.
Observed at double magnification, the equivalent spherical diameter distribution of at least 100 particles is obtained by Luzex 500 manufactured by Nippon Regulator Co., Ltd., and calculated from the point of 50% in weight accumulation.

(2) Running friction coefficient (μk) of film The measurement is carried out as follows using the apparatus shown in FIG.
In FIG. 1, 1 is an unwind reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (inlet), 7 is a stainless steel SUS304 fixed rod (outside). Diameter 5mmφ, surface roughness Ra =
0.02 μm), 10 is a tension detector (exit), 1
Reference numeral 2 is a guide roller, and 13 is a take-up reel.

At a temperature of 20 ° C. and a humidity of 60%, the width is 1 /
The film cut into 2 inches is attached to the fixed rod 7 at an angle θ = (1
52/180) π radians (152 °) and moved (rubbed) at a speed of 200 cm per minute. The exit tension (T ₂ : g) when the tension controller 2 is adjusted so that the entrance tension T ₁ is 35 g is detected by the exit tension detector after the film has run 90 m, and the running friction coefficient μk is calculated by the following formula. calculate.

[0037]

[Number 1] μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35)

(3) Flatness of film surface Ra (center line average roughness) is measured according to JIS B 0601. Using a stylus type surface roughness meter (SURFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd., a chart (film surface roughness curve) is drawn under the conditions of a needle radius of 2 μm and a load of 0.07 g to obtain a film. A portion of the measurement length L is extracted from the surface roughness curve in the direction of the center line, the center line of the extracted portion is taken as the X axis, the longitudinal magnification direction is taken as the Y axis, and the roughness curve Y = f (x) When expressed, the value (Ra: μm) given by the following equation is defined as the flatness of the film surface.

[0039]

[Equation 2]

In the present invention, 8 pieces are measured with a reference length of 0.25 mm, and Ra (μm) is expressed as an average value of 5 pieces excluding 3 pieces having the larger values.

(4) Scraping resistance In the same apparatus as that used in FIG. 1 used for measuring the running friction coefficient μk, the winding angle was 30 degrees, and the running tension was 600 m at a speed of 300 m / min and an inlet tension of 50 g. Let The shavings adhering to the fixed rod 7 after running and the scratches of the tape after running are evaluated. At this time, as the fixing rod 7, a 6φ tape guide (surface roughness Ra = 0.15 μm) obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish.
To use.

<Judgment of shavings> A: No shavings are observed. ○: A slight amount of shavings can be seen. Δ: The presence of shavings can be seen at a glance. X: Shavings are badly attached.

(5) Glass transition temperature of polyester (T
g) Using a differential calorimeter (Model 990 ThermalAnalyzer, manufactured by Dupont Instruments), the sample is heated from room temperature at a rate of 20 ° C./min to 290 ° C. when the polyester is polyethylene terephthalate (PET), and polyethylene-2,6- In the case of naphthalate (PEN), it is obtained from the temperature-differential heat quantity curve when the temperature is raised to 300 ° C., then rapidly cooled to 0 ° C., and again raised at a rate of 20 ° C./min.

(6) Melting point (Tm) of polyester Using a differential calorimeter (Model 990 Thermal Analyzer) manufactured by Dupont Instruments, the temperature / differential calorimetric curve when the sample is heated from room temperature at a rate of 20 ° C./min. Ask more.

Example 1 (1) Production of Silicone Resin Fine Particles and Surface Treatment with Silane Coupling Agent: A 10 liter glass container equipped with a stirring blade was charged with 7000 g of an aqueous solution containing 0.2% by weight of sodium hydroxide. After gently injecting 1000 g of methyltrimethoxysilane into the upper layer to form two layers, 1
Interfacial reaction was carried out at 0 to 15 ° C. at a rotation speed of 20 rpm for 3 hours, whereby particles were generated. Then the temperature is 70 ℃
After aging for 1 hour, the mixture was cooled and then filtered with a vacuum filter to obtain a cake of silicone resin fine particles having a water content of about 30%. Next, the entire cake-like substance obtained in the above reaction was added to 4000 g of an aqueous solution in which 2% by weight of γ-glycidoxypropyltrimethoxysilane as a silane coupling agent was dispersed in the above glass container used in the reaction, and a slurry was added. The surface treatment was performed for 3 hours at an internal temperature of 70 ° C. and a rotation speed of 60 rpm, and after cooling, filtration was performed with a vacuum filter. Then, this time, the whole amount of the surface-treated cake was added to 6000 g of water containing no silane coupling agent to form a slurry again, and the mixture was stirred at room temperature and 60 rpm for 1 hour, and then filtered with a vacuum filter, A cake having a water content of about 40% from which the excess silane coupling agent was removed was obtained. Finally, the cake was dried under reduced pressure at 120 ° C. and 15 Torr for 10 hours to obtain about 400 g of fine powder of silicone resin surface-treated with a silane coupling agent.

Observation of the obtained fine particles with an electron microscope revealed that the particles had a true spherical shape, and the particle size distribution obtained by the centrifugal sedimentation method was 0.5% for 90% or more by weight.
Average particle size of 0.6 μm with uniform particle size within 0.7 μm
Of fine particles.

(2) Production of polyester containing fine particles of silicone resin: Using dimethyl terephthalate and ethylene glycol as raw materials, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, and phosphorous acid as a stabilizer are prepared by a conventional method. Further, at the end of the transesterification reaction, the silicone resin fine particles obtained in (1) were sufficiently dispersed by a conventional method to prepare a 20 wt% ethylene glycol slurry, and 0.10 wt% of the fine particles was added to dimethyl terephthalate. Add a considerable amount and then carry out the polymerization reaction to obtain an intrinsic viscosity (orthochlorophenol, 35
C.) 0.62 polyester (polyethylene terephthalate) was obtained. The polyester has Tg of 70 ° C. and Tm2
It was 57 ° C.

(3) Film formation of polyester: (2)
The polyester pellets obtained in 1. were dried at 170 ° C. for 3 hours and then fed to an extruder hopper at a melting temperature of 280 to 3
It was melted at 00 ° C., and the molten polymer was extruded through a 1 mm slit die onto a rotary cooling drum having a surface temperature of 20 ° C. and rapidly cooled to obtain an unstretched film.

The unstretched film thus obtained is preheated at 75 ° C., and further 15 m between low speed and high speed rolls.
m from above, heated by one IR heater having a surface temperature of 900 ° C., stretched to 3.6 times, rapidly cooled, then fed to a stenter, and stretched 3.7 times in the transverse direction at 105 ° C. .
The obtained biaxially oriented film was heat-set at a temperature of 205 ° C. for 5 seconds to obtain a heat-set biaxially oriented polyester film having a thickness of 15 μm.

The characteristics of the obtained film are shown in Table 1.

[Example 2] The silane coupling agent was N-
A polyester film was obtained in the same manner as in Example 1 except that β (aminoethyl) γ-aminopropyltrimethoxysilane was used.

The film properties obtained are shown in Table 1.

[Example 3] Instead of synthesizing silicone resin fine particles, a polymethylsilsesquioxane powder (trade name: Tospearl 120) manufactured by Toshiba Silicone Co., Ltd. having a true spherical shape and an average particle size of 1.3 μm A surface treatment with a silane coupling agent was performed in the same manner as in Example 1 except that 400 g was used and γ-glycidoxypropylmethyldiethoxysilane was used as the silane coupling agent, and the addition amount was changed to dimethyl terephthalate. 0.03% by weight
A polyester film was obtained in the same manner as in Example 1 except that the amount was increased.

The film properties obtained are shown in Table 1.

Example 4 A polyester (polyethylene naphthalate) was obtained in the same manner as in Example 1 except that 2,6-naphthalenedicarboxylic acid dimethyl ester was used in place of dimethyl terephthalate in the polyester raw material of Example 1. It was The resulting polyester has a Tg of 120.
C. and Tm 267.degree.

Then, 17 pellets of the polyester are prepared.
After drying at 0 ° C. for 3 hours, it is fed to an extruder hopper and melted at a melting temperature of 290 to 310 ° C.
It was extruded onto a rotary cooling drum having a surface temperature of 60 ° C. through a slit-shaped die of m and rapidly cooled to obtain an unstretched film.

The unstretched film thus obtained is preheated at 130 ° C., and the rolls are rolled at low speed and high speed for 15 minutes.
mm from above, heated by one IR heater having a surface temperature of 900 ° C., stretched 3.6 times, rapidly cooled, then supplied to a stenter, and stretched laterally 3.7 times at 135 ° C. . The obtained biaxially oriented film was heat set with hot air at 230 ° C. for 5 seconds to obtain a heat set biaxially oriented polyester film having a thickness of 15 μm.

The characteristics of the obtained film are shown in Table 1.

Comparative Example 1 A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the surface treatment with the silane coupling agent in Example 1 was omitted.

Table 2 shows the characteristics of the obtained film.

[Comparative Example 2] A polyethylene terephthalate film was obtained in the same manner as in Example 3, except that the surface treatment with the silane coupling agent in Example 3 was omitted.

Table 2 shows the characteristics of the obtained film.

[Comparative Example 3] A polyethylene naphthalate film was obtained in the same manner as in Example 4, except that the surface treatment with the silane coupling agent in Example 4 was omitted.

The characteristics of the obtained film are shown in Table 2.

In contrast to the films of Comparative Examples 1 to 3, the films of Examples 1 to 4 all have stable slipperiness, the generation of white powder is greatly reduced, and the abrasion resistance is significantly improved. Admitted.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

According to the present invention, it is possible to provide a polyester film which is excellent in both slipperiness and abrasion resistance.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for measuring a running friction coefficient (μk).

[Explanation of symbols]

 1 Unwinding reel 2 Tension controller 4 Tension detector (inlet) 7 Fixed rod 10 Tension detector (outlet) 13 Take-up reel

Claims (6)

[Claims] 1. Silicone resin fine particles having an average particle diameter of 0.05 to 3 μm, 80% by weight or more of the particles consisting of a bonding unit represented by the following formula, and the surface of the particles being treated with a silane coupling agent. Is contained in an amount of 0.005 to 2% by weight with respect to the weight of polyester. Embedded image RSiO _3/2 (wherein R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group.) 2. The polyester film according to claim 1, wherein the silane coupling agent is a silane coupling agent having an epoxy group. 3. The polyester film according to claim 1, wherein the silicone resin fine particles are substantially spherical and are fine particles made of polymethylsilsesquioxane. 4. A total of 0.01 to 2% by weight (based on the weight of polyester) of one or more kinds of fine particles having an average particle diameter of 0.05 to 2 μm selected from other organic fine particles and inert inorganic fine particles. ) The polyester film according to claim 1, which further comprises: 5. The polyester film according to claim 1, wherein the polyester is polyalkylene terephthalate or polyalkylene naphthalate. 6. The polyester film according to claim 1, wherein the polyester film is a biaxially oriented film.