JP2018053198A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mat-like polyester film capable of being continuously produced without pressure rise of a filter, reducing oligomer amount deposited from a film surface by a heat treatment, capable of being suitably used as a mold release film and having no contamination of an adherend after mold release when used as a mold release film.SOLUTION: There is provided a polyester film of which at least one surface is constituted by a polyester film layer A, in which the polyester film layer A contains organic particles having thermal decomposition temperature under ambient air atmosphere of 275°C or more and the amount of an oligomer deposited from a surface of the polyester film layer A at 100°C after 5 hours is 3.5 mg/mor less.SELECTED DRAWING: None

Description

  The present invention relates to a polyester film containing organic particles.

Many methods have been proposed and put into practical use in which fine particles are contained in a polyester film, moderate irregularities are added to the film surface, and blocking resistance and releasability are imparted.
For example, Patent Document 1 discloses that a polyester film contains inert inorganic particles such as silicon oxide. However, the inorganic particles are not easily deformed, and the filter is clogged in the filtration step of the resin melt extrusion, and the pressure of the filter is likely to be increased, which may cause a problem in productivity. Patent Document 2 discloses a biaxially oriented polyester film for mold release having a low glossiness in which organic particles are contained in the outermost polyester layer. However, the polyester film containing organic particles disclosed in Patent Document 2 has a complicated process in which a release layer containing a binder component and a fluorine-based release agent is further provided on the surface. Since the low molecular component contained in the mold layer may contaminate the adherend surface after release, it is unsuitable for use in obtaining the residual adhesion rate on the adherend after release.

  On the other hand, in recent years, due to diversification of uses of polyester films, the processing of films at high temperatures and the use of them at high temperatures have increased, and oligomers generated from high-temperature-treated polyester films are often regarded as problems. It has become. That is, the oligomer deposited from the polyester film not only contaminates the process equipment such as a cooling roll and a press die, but also may contaminate the surface of the adherend when used for mold release.

In order to solve the above problem, Patent Document 3 discloses a method of reducing the amount of generated oligomers by subjecting polyester to solid-phase polymerization, and Patent Document 4 discloses a laminated film of a water-soluble resin mixture as polyester. A method of sealing a generated oligomer by laminating on a film is disclosed.
However, in the matte film using the polyester subjected to the solid phase polymerization treatment disclosed in Patent Document 3, since the intrinsic viscosity of the polyester is high, voids are generated in the stretched film, and the obtained film is The appearance was inferior. In addition, even when using solid-phase polymerized polyester, if the surface is matte, oligomers are deposited on the film surface by heat treatment even during the production of the film. This oligomer may cause streaks and the like.
Moreover, the method disclosed in Patent Document 4 for laminating a laminated film to suppress oligomer precipitation has a problem that it is complicated because of an increase in steps. In addition, when the surface uneven shape is imparted, the film in which the laminated film is laminated after the surface uneven shape is imparted has a tendency that the surface uneven shape is leveled, resulting in inferior blocking resistance and releasability. .

JP 2001-322218 A Japanese Patent Laying-Open No. 2015-40220 JP 2000-141570 A JP 2004-195775 A

  The present invention solves the above problems, can be continuously produced without increasing the pressure of the filter, the amount of oligomers precipitated from the film surface by heat treatment is suppressed, can be suitably used as a release film, as a release film When used, the object is to provide a matte polyester film that does not contaminate the adherend after release.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by a polyester film containing specific organic particles, and has reached the present invention.

The gist of the present invention is as follows.
(1) A polyester film having at least one surface composed of a polyester film layer A,
The polyester film layer A includes organic particles having a thermal decomposition temperature of 275 ° C. or higher in an air atmosphere,
The polyester film characterized by the amount of the oligomer which precipitates from the surface of the polyester film layer A after heating at 100 degreeC for 5 hours being 3.5 mg / m < ² > or less.
(2) The polyester film according to (1), wherein the organic particles have an average particle diameter of 1 to 15 μm.
(3) The polyester film according to (1) or (2), wherein the content of organic particles in the polyester film layer A is 0.1 to 15% by mass.
(4) The polyester film according to any one of (1) to (3), wherein the organic particles are crosslinked acrylic particles.
(5) The polyester film according to any one of (1) to (4), wherein the glossiness (60 °) on the surface of the polyester film layer A is 60% or less.

  According to the present invention, in production, there is no filter pressurization and suitable for continuous production, and in use, since oligomer precipitation from the film surface during heat treatment is suppressed, cooling rolls, press dies, etc. Matte polyester that can suppress contamination of process equipment and contamination of the adherend surface when used as a release film, and the adhesive material used as the adherend has excellent residual adhesion after release. A film can be provided.

The polyester film of the present invention has at least one surface constituted by a polyester film layer A, and the polyester film layer A contains organic particles having a thermal decomposition temperature of 260 ° C. or higher in an air atmosphere.
In the present invention, the polyester resin constituting the polyester film is not particularly limited, and examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. Among these, polyethylene terephthalate is excellent in the balance between heat resistance and mechanical properties, and is excellent in stretchability, so that it can be suitably used. Polyethylene terephthalate is usually a method of transesterification from dimethyl terephthalate and ethylene glycol, or a method of melt polymerization or further solid phase polymerization after obtaining an oligomer by direct esterification from terephthalic acid and ethylene glycol. Is obtained.

  The polyester resin can be copolymerized with other components. Other copolymer components include dicarboxylic acid components such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecane Examples include acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid. In addition, as other copolymer components, glycol components include diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, triethylene. Examples include glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and the like.

The polyester film of the present invention is a polyester film layer A in which at least one surface contains organic particles in order to improve surface slipperiness and prevent blocking and the like by forming irregularities on the surface and forming a matte tone. It is necessary to consist of.
The polyester film of the present invention may be composed only of the polyester film layer A containing organic particles, or a laminated film with a polyester film layer other than the polyester film layer A (hereinafter sometimes referred to as polyester film layer B). There may be. When the polyester film layer B constitutes the surface layer of the polyester film, the polyester film layer B preferably includes particles from the viewpoint of film running, and the particles may be either organic particles or inorganic particles.

The thickness of the polyester film layer A is not particularly limited, but is preferably at least one quarter of the average particle diameter of the organic particles, and more preferably at least one half. Since the film layer A has a thickness that is at least one-fourth of the average particle diameter of the organic particles, the organic particles can be easily held in the film layer A, and the organic particles are less likely to fall off. The upper limit of the thickness of the film layer A is not particularly provided as long as the diffuse transmittance and the total light transmittance are within the desired ranges.
When the polyester film of the present invention is composed of a plurality of film layers A, the total thickness is not particularly limited, but is 1 to 50% of the total thickness of the polyester film from the viewpoint of controlling the total light transmittance. Is preferable, and 10 to 40% is more preferable.

The organic particles contained in the polyester film layer A are required to have a thermal decomposition temperature of 275 ° C. or higher in the air atmosphere, more preferably 290 ° C. or higher, and further preferably 300 ° C. or higher. In the present invention, the thermal decomposition temperature in the air atmosphere is a temperature at which the mass is reduced by 5% in the thermal analysis (TG / DTA) in the air atmosphere.
The polyester film layer A contains organic particles having a thermal decomposition temperature of 275 ° C. or higher in an air atmosphere, and the reason is unknown, but the amount of oligomers deposited on the film surface by heat treatment can be reduced.

  Specific examples of the organic particles include crosslinked acrylic particles, crosslinked polystyrene particles, crosslinked melamine particles, organic silicone particles, and crosslinked styrene-acrylic particles. Among these, cross-linked acrylic particles, cross-linked styrene particles, and cross-linked styrene-acrylic particles are preferable because they have a high thermal decomposition temperature in the air atmosphere. As the organic particles, a single component may be used, or two or more components may be used simultaneously.

  The average particle diameter of the organic particles varies depending on the use application of the polyester film, and is not particularly limited, but is preferably 1 to 15 μm, and more preferably 2.5 to 12 μm. Since the organic particles have an average particle diameter of 1 μm or more, sufficient unevenness can be imparted to the film surface. Therefore, the polyester film is excellent in slipperiness, blocking between films, and meandering or winding deviation when wound. Is less likely to occur. In addition, organic particles having an average particle diameter of 15 μm or less can be easily held in the film, and it is difficult for the particles to fall off or to be cut.

  Although there is no restriction | limiting in particular in content of the organic particle in the polyester film layer A, it is preferable that it is 0.1-15 mass%, and it is more preferable that it is 1-6 mass%. Since the organic particles can make a sufficient number of protrusions on the film surface when the content is 0.1% by mass or more, it is possible to impart good anti-blocking performance. Moreover, it becomes easy to hold | maintain the organic particle whose content is 15 mass% or less in a film, and drop | omission of a particle | grain and the cutting | disconnection of a film become difficult to generate | occur | produce.

The polyester film layer A may contain particles other than the organic particles defined in the present invention as long as the effects of the present invention are not impaired, and the type of particles may be organic particles or inorganic particles, but the average particle diameter Is preferably smaller than the average particle size of the organic particles defined in the present invention.
Examples of the inorganic particles include silicon oxide, titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, zeolite, kaolin, clay, talc, and mica. Examples of the organic particles include organic particles such as melamine resin, polystyrene, organic silicone resin, and acrylic-styrene copolymer. In particular, silicon oxide (silica) is preferable because it has an excellent particle size distribution and is inexpensive.

Since the polyester film of the present invention contains organic particles having a thermal decomposition temperature of 275 ° C. or higher in an air atmosphere, oligomer precipitation from the film surface during heat treatment is suppressed, and the polyester film is heated at 100 ° C. for 5 hours. The amount of oligomer precipitated from the surface of layer A can be 3.5 mg / m ² or less, and the amount of oligomer deposited is preferably 2.5 mg / m ² or less, and is 1.5 mg / m ² or less. More preferably. There is no particular lower limit on the amount of oligomers to be precipitated, and a smaller amount is preferred. When the thermal decomposition temperature of the organic particles contained in the polyester film in the air atmosphere is, for example, less than 275 ° C., the amount of oligomer precipitation from the film surface increases when heated at 100 ° C. for 5 hours.

  In the polyester film of the present invention, the glossiness (60 degrees) of the polyester film layer A surface is not particularly limited, but is preferably 60% or less, more preferably 40% or less, and 25% or less. More preferably it is. Since the gloss (60 degrees) of the polyester film layer A surface is 60% or less, the polyester film does not block when laminated, and does not embed air during winding, and is easy to work with. It will be excellent. Although the lower limit of the glossiness (60 degrees) of the polyester film layer A surface is not particularly provided, it is preferably 5% or more from the viewpoint of the strength of the film surface.

  The diffuse transmittance of the polyester film of the present invention is not particularly limited, but is preferably less than 50% and 20% or more, and more preferably less than 50% and 35% or more. When the polyester film has a diffuse transmittance of less than 50%, when used for a protective film or the like, it becomes easy to identify the state of the bonded partner. Further, the polyester film has a diffuse transmittance of 20% or more, more preferably 35% or more, thereby eliminating blocking when the matte film is wound.

  The total light transmittance of the polyester film of the present invention is not particularly limited, but is preferably 75% or more, and more preferably 85% or more. When the polyester film has a total light transmittance of 75% or more, when used for a protective film or the like, it becomes easy to identify the state of the bonded partner. The upper limit of the total light transmittance of the polyester film is not particularly limited, but when it is 85% or more, there is almost no performance difference in identification.

  The haze of the polyester film of the present invention is not particularly limited, but is preferably 60% or more, more preferably 70% or more, and further preferably 75% or more. When the polyester film is used for a protective film or the like because the haze is 60% or more, the polyester film can be distinguished from the bonded partner.

  The polyester film of the present invention has a layer containing a silicone resin, an epoxy resin, an acid-modified polyolefin resin, etc., as long as at least one surface is composed of the polyester film layer A, so long as the effects of the present invention are not impaired. May be.

Next, an example of the manufacturing method of the polyester film of this invention is demonstrated.
When the polyester film of the present invention is a laminated film, a method in which an unstretched sheet extruded by a co-extrusion method in which all layers are co-melt extruded from a die is biaxially stretched and heat-set is preferable.
As a coextrusion method, any of a feed block type or a multi-manifold type may be used. A resin composition containing organic particles for forming the polyester film layer A and a resin composition for forming the film layer B are supplied to separate melt extrusion apparatuses, and the melting points of the respective polyester resins. It is melted at a temperature of ˜ (melting point + 40 ° C.) and extruded through a filter by a T-die into a sheet shape.
Then, the extruded laminated sheet-like body is brought into close contact with a cooling drum whose temperature is adjusted to 30 ° C. or lower by a known method such as an electrostatic application casting method or an air knife method so that the temperature becomes a glass transition temperature or lower. Rapid solidification is performed to obtain an unstretched sheet having a desired thickness.

Next, a polyester film excellent in mechanical properties and dimensional stability can be obtained by biaxially stretching the obtained unstretched sheet in the longitudinal direction and the transverse direction. As a biaxial stretching method, a simultaneous biaxial stretching method in which stretching is performed simultaneously in the machine direction and the transverse direction with a tenter type simultaneous biaxial machine, or in a transverse direction with a tenter type transverse stretching machine after stretching in the longitudinal direction with a roll type stretching machine. A sequential biaxial stretching method for stretching can be used.
Although there is no restriction | limiting in particular in a draw ratio, 3 times or more are preferable at the area magnification of a polyester film, More preferably, it is 4-20 times, More preferably, it is 6-15 times. Although there is no particular upper limit, by setting the area magnification to 20 times or less, it is possible to further suppress the generation of voids and further reduce the frequency of film breakage.
The stretching temperature is not particularly limited, but a range of (glass transition temperature + 5 ° C.) to (glass transition temperature + 60 ° C.) of the polyester resin is preferable, and a range of (glass transition temperature + 15 ° C.) to (glass transition temperature + 55 ° C.). More preferred. By stretching at (glass transition temperature + 5 ° C.) or more, generation of voids can be further suppressed. The stretched film was heat treated for several seconds at a temperature of 150 ° C. to (polyester melting point−5 ° C.) in a tenter at a relaxation rate of 0 to 10% in the machine direction and the transverse direction, and then cooled to room temperature. Wind up at a speed of ~ 200 m / min. Thereby, a film having a desired thickness can be obtained.

The heat treatment step for heat-setting the stretched film is a preferable step for reducing the thermal shrinkage of the polyester film. As a heat treatment method, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, or the like can be used. Among them, a method of blowing hot air is preferable because it can be heated uniformly and accurately.
Although the thickness of a film is not specifically limited, The range of 5-500 micrometers is preferable.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Characteristic evaluation method]
[Average particle diameter]
Measurement was performed with a laser diffraction / scattering particle size analyzer (SALD-7100 manufactured by Shimadzu Corporation), and the volume average particle size was defined as the average particle size of the particles. The dispersion of the particles was prepared by dissolving the master batch chip in a mixed solvent of phenol / tetrachloroethane = 50/50 (mass ratio) so that the diffracted / scattered light intensity was 40 to 60%. A dispersion was obtained.

[Thermal decomposition temperature of organic particles (in air)]
After drying the organic particles under reduced pressure at 60 ° C. for 4 hours, using a differential thermothermal gravimetric simultaneous measurement apparatus (SII Nano Technology, “TG / DTA 7200”), under an air atmosphere (Sumitomo Seika Co., Ltd., AIR ZERO-A). At a flow rate of 200 mL / min), the temperature was increased from 30 ° C. to 470 ° C. at 20 ° C./min. The temperature at which the mass decreased by 5 mass% with respect to the mass before the temperature elevation was defined as the thermal decomposition temperature.

[Thermal decomposition temperature of organic particles (under nitrogen atmosphere)]
After drying the organic particles under reduced pressure at 60 ° C. for 4 hours, using a differential thermothermal gravimetric simultaneous measurement apparatus (SII Nano Technology, “TG / DTA 7200”), under a nitrogen atmosphere (Sumitomo Seika Co., Ltd., N2 ZERO-A) At a flow rate of 200 mL / min), the temperature was increased from 30 ° C. to 470 ° C. at 20 ° C./min. The temperature at which the mass decreased by 5 mass% with respect to the mass before the temperature elevation was defined as the thermal decomposition temperature.

[Total light transmittance and haze]
The total light transmittance and haze of the polyester film were measured with a Nippon Denshoku Industries Co., Ltd. spheroid turbidimeter NDH-300A.

[Glossiness]
According to the method prescribed | regulated to JIS-Z-8741, the 60 degree specular glossiness was measured about the polyester film layer A surface of the polyester film using the gloss meter (Nippon Denshoku VG7000).

[Surface roughness Ra, Rz]
Using a non-contact type surface roughness measuring device (Tailorf CCI6000, manufactured by Taylor Hobson), the polyester film layer A surface of the polyester film fixed on the slide glass was actually measured with an objective lens 20 times, and the robust Gaussian filter 0 .25 mm is used to analyze the surface roughness of the polyester film layer A surface of the polyester film, the arithmetic average value of the deviation from the average value is the centerline average roughness Ra (μm), and the top five heights An average value obtained by adding the height and the top five depths was defined as a ten-point average height Rz.

[Blocking resistance]
The polyester film obtained in Examples and Comparative Examples was cut into a size of 50 mm × 50 mm, and the polyester film and a biaxially stretched polyethylene terephthalate (PET) film (S-50, manufactured by Unitika Ltd.) were used as a polyester film layer A. The surface and the non-corona surface of the biaxially stretched PET film were overlapped and left standing for 24 hours at 60 ° C. under a load of 10 kPa. After removing the load and cooling to room temperature, the blocking resistance was evaluated by examining the adhesion between the layer A and the PET film.
○: Adhesion is not recognized between the layer A and the PET film.
(Triangle | delta): Although adhesion | attachment was recognized between the layer A and PET film, it peeled easily and there is no change, such as whitening, in the layer A (no problem practically).
X: When peeling between the layer A and PET film, the layer A causes cohesive failure, or the layer A after peeling is entirely white.

[Operability]
In Examples and Comparative Examples, polyester films were produced continuously for 15 hours, and operability was evaluated according to the following criteria.
○: There was no problem including the film appearance.
Δ: Although some streaks entered the film, there was no problem in production.
X: A film could not be continuously produced for 15 hours due to the pressure increase of the filter.

[Surface precipitation oligomer amount]
A polyester film was superposed on JIS A4 size Kent paper so that the polyester film layer A surface was on the outside, and the four corners were clipped to fix the polyester film to the Kent paper. The polyester film in a fixed state was put in an oven at 100 ° C. under a nitrogen atmosphere and left for 5 hours, and then taken out.
Next, a box is formed by folding four sides so that the bottom surface of the polyester film layer A faces inward (12.5 cm × 20 cm), and about 10 ml of acetonitrile is placed in this box and immersed for 3 minutes. The extract and the co-wash solution of the box were transferred to a 20 mL volumetric flask and finally made up to 20 ml. The amount of oligomer in the solution was determined from the peak area ratio of the standard sample peak area and the measured sample peak area using liquid chromatography (Waters Alliance) (absolute calibration curve method). A standard sample was prepared by accurately weighing a preliminarily prepared cyclic trimer of polyethylene terephthalate and dissolving it in accurately weighed acetonitrile.
The amount of precipitated oligomer (mg / m ² ) on the surface of the polyester film layer A was calculated by dividing the amount of oligomer in the solution by the area of the polyester film layer A.
The measurement conditions of the liquid chromatograph were as follows. Mobile phase A: acetonitrile, mobile phase B: acetonitrile / water mixture (= 7/3), column: Water Bond microbond sphere, column temperature: 25 ° C., flow rate: 1 ml / min, detection wavelength: 254 nm.

[Peel strength]
The polyester films obtained in Examples and Comparative Examples were put in an oven at 100 ° C. and heat-treated for 5 hours. An adhesive tape (LP-24 manufactured by Nichiban Co., Ltd.) was applied to the polyester film layer A surface, and the humidity was adjusted in an atmosphere of 23 ° C. and 50% RH. Then, the 180 degree peeling test at the time of peeling an adhesive tape from the polyester film layer A surface was performed for the sample which adjusted humidity using the autograph at the crosshead speed of 300 mm / min, and the peeling strength was measured. The releasability was evaluated according to the following criteria.
○: Less than 1.5 N / cm Δ: 1.5 N / cm or more, less than 2.5 N / cm x: 2.5 N / cm or more

[Residual adhesion rate]
In the measurement of the peel strength, an adhesive tape (LP-24 manufactured by Nichiban Co., Ltd.) peeled from the layer A surface of the polyester film was attached to a SUS plate and conditioned in an atmosphere of 23 ° C. and 50% RH. Thereafter, the peel strength (F1) between the pressure-sensitive adhesive tape and the SUS plate was measured in the same manner as the above-described peel strength measurement method.
On the other hand, an unused adhesive tape was affixed to a SUS plate and conditioned in an atmosphere of 23 ° C. and 50% RH. Thereafter, the peel strength (F2) between the pressure-sensitive adhesive tape and the SUS plate was measured in the same manner as the peel strength measurement method.
From the obtained F1 and F2, the residual adhesion rate was calculated using the following formula.
Residual adhesion rate (%) = (F1 / F2) × 100
○: 85% or more Δ: 50% or more and less than 85% ×: less than 50%

[material]
[Organic particles]
The following crosslinked acrylic particles were used as the organic particles (P-1) to (P-7).
P-1: KSR-3A manufactured by Soken Chemical
P-2: MX-180TA manufactured by Soken Chemical Co., Ltd.
P-3: Uni powder NMB-0520 manufactured by JX Nippon Oil & Energy
P-4: Uni powder NMB-1520 manufactured by JX Nippon Oil & Energy Corporation
P-5: Uni powder NMB-3020 manufactured by JX Nippon Oil & Energy
P-6: MX-300 manufactured by Soken Chemical Co., Ltd.
P-7: Uni powder NMB-0520C manufactured by JX Nippon Oil & Energy

[Inorganic particles]
P-8: Silica particles (average particle size 2.3 μm)
P-9: Titanium oxide particles (average particle size 0.2 μm)

Example 1
[Preparation of resin composition for forming polyester film layer A]
Polyethylene terephthalate (inherent viscosity 0.65 dl / g) and organic particles were melt blended with a biaxial kneader so that the content of the organic particles (P-1) was 4.0% by mass. Dispensing by a conventional method and then pelletizing and drying by a conventional method gave a resin composition (A-1) for forming a polyester film layer A.
[Preparation of resin composition for forming polyester film layer B]
After blending the silica particles (P-8) with polyethylene terephthalate pellets (inherent viscosity 0.69 dl / g) so that the content is 0.05 mass%, it is dried by a conventional method and melted in a sub-extruder. Then, a resin composition for forming the polyester film layer B was prepared.
[Production of polyester film]
After the melt of the resin composition (A-1) for forming the film layer A and the melt of the resin composition for forming the film layer B are merged in a feed block, the film layer A is obtained from the T die. And a film layer B is extruded so that the thickness ratio is 15/23, and is brought into close contact with an electrostatic application method on a cooling drum whose surface temperature is adjusted to 20 ° C. and rapidly cooled to obtain an unstretched film having a thickness of 650 μm. It was.
Subsequently, the unstretched film was preheated with a preheating roll group whose temperature was adjusted to 90 ° C., and then longitudinally stretched 3.5 times by changing the peripheral speed between the stretching rolls whose temperature was adjusted to 90 ° C. A stretched film was obtained. Subsequently, the longitudinally stretched film is guided to a tenter type stretching machine, and is stretched 5 times at a preheating temperature of 90 ° C. and a stretching temperature of 120 ° C., followed by heat treatment at 245 ° C., and a relaxation treatment of 3% in the transverse direction at 200 ° C. Went.
The film coming out of the tenter was subjected to corona treatment on the film layer B side, and then wound up at a film speed of 90 m / min to obtain a polyester film having a thickness of 38 μm.

Examples 2-12, Comparative Examples 1-4
As shown in Table 1, a polyester film was prepared in the same manner as in Example 1 except that the type and content of particles constituting the polyester film layer A, the type of polyester resin, and the laminated configuration and thickness configuration of the polyester film were changed. Obtained. In Example 8, polybutylene terephthalate (intrinsic viscosity 1.10 dl / g) was used as the polyester resin constituting the film layers A and B.

  Table 1 shows the evaluation results of the polyester films obtained in Examples and Comparative Examples.

Since the polyester film of Examples 1-12 contains the organic particle prescribed | regulated by this invention, it was excellent in blocking resistance and mold release property, and the oligomer amount which precipitates on the film surface by heat processing was suppressed. As a result, the polyester film can be stably produced for a long time, and the adhesive tape released from the polyester film maintains the residual adhesion rate.
On the other hand, the polyester films of Comparative Examples 1 and 2 contain organic particles whose thermal decomposition temperature in the air atmosphere is lower than the range specified in the present invention. In the continuous production, the coating streaks tended to be inferior due to the accumulation of oligomers.
Since the polyester film of Comparative Example 3 contained inorganic particles instead of the organic particles defined in the present invention, the pressure of the filter increased due to long-term production, and production was interrupted.
Since the polyester film of Comparative Example 4 did not contain particles in the film layer A, blocking when wound in a roll shape was remarkable, and the release property was inferior.

Claims (5)

At least one surface is a polyester film composed of a polyester film layer A,
The polyester film layer A includes organic particles having a thermal decomposition temperature of 275 ° C. or higher in an air atmosphere,
The polyester film characterized by the amount of the oligomer which precipitates from the surface of the polyester film layer A after heating at 100 degreeC for 5 hours being 3.5 mg / m < ² > or less.   The polyester film according to claim 1, wherein the organic particles have an average particle diameter of 1 to 15 µm.   The polyester film according to claim 1 or 2, wherein the content of organic particles in the polyester film layer A is 0.1 to 15% by mass.   The polyester film according to claim 1, wherein the organic particles are crosslinked acrylic particles. The polyester film according to claim 1, wherein the glossiness (60 °) on the surface of the polyester film layer A is 60% or less.