polyester film

Abstract

The present invention provides a polyester film that suppresses film adhesion during conveying processes, exhibits good release properties during heating processes, and can be suitably used as a release film for processing. [Solution] A polyester film in which, on at least one surface A of the polyester film, the rate of change in the amount of fatty acid-derived components, as determined by TOF-SIMS analysis after heat treatment at 170°C for 5 minutes in air, is 15% or more and 60% or less.

Description

[Technical Field]

[0001] This invention relates to a polyester film. [Background technology]

[0002] Polyester films, such as polyethylene terephthalate and polyethylene naphthalate, possess excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and are cost-effective, making them suitable for a wide range of applications.

[0003] However, due to the molecular structure of polyester, it has poor release properties, and generally, a technique of coating the surface with a release component is used to impart this property. However, this has led to problems such as performance degradation due to surface deformation during processing.

[0004] Furthermore, in the case of conductive films used in displays and other applications, particularly polyester films commonly used as support films for transfer-type conductive films, there is a growing need for films that offer superior release properties and handling characteristics after the heat pressing process.

[0005] Polyester films containing high concentrations of inorganic or organic particles (e.g., Patent Document 1) and iridescent stretched polyester films for molding (e.g., Patent Document 2) have been proposed as films to be applied to this use. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent Application No. 2020-503558 [Patent Document 2] Patent Application No. 2000-367242 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the film described in Patent Document 1, while having excellent low gloss due to the formation of irregularities on the film surface, had the problem of poor release properties due to increased non-adhesion strength caused by the anchoring effect of the irregularities on the film surface. In addition, as a result of the increased adhesion strength due to the anchoring effect of the irregularities on the film surface, cohesive breakdown may occur near the particles within the film, leading to problems such as film tearing and film adhesion during the process.

[0008] Furthermore, the film described in Patent Document 2 has excellent transparency and improved release properties by including a small amount of wax in the resin. However, while it has good release properties in its initial state, there was a problem in that it sometimes lacked sufficient release properties during the heating process.

[0009] The object of the present invention is to solve the problems of the conventional technology described above. Specifically, it is to provide a polyester film that suppresses film adhesion during conveying processes, has good release properties during heating processes, and can be suitably used as a release film for processes. [Means for solving the problem]

[0010] To solve the above problems, the present invention has the following configuration. (1) A polyester film in which, on at least one surface A of the polyester film, the rate of change in the amount of fatty acid-derived components determined by TOF-SIMS analysis after heat treatment at 170°C for 5 minutes in air is 15% or more and 60% or less. (2) The polyester film according to (1), wherein the layer constituting one side A of the polyester film contains one or more of polybutylene terephthalate and polytrimethylene terephthalate. (3) The polyester film according to (2), wherein one of the layers A constituting one side of the polyester film contains two or more of the following: polybutylene terephthalate, a block copolymer of polybutylene terephthalate and polyoxyalkylene glycol, and polytrimethylene terephthalate. (4) The polyester film according to any one of (1) to (3), wherein the mean center surface roughness (SRa) of one surface A of the polyester film is 600 nm or more and 2000 nm or less, and the skewness (Ssk) is 0.5 or more and 1.5 or less. (5) The polyester film according to any one of (1) to (4), wherein the layer constituting one side A of the polyester film contains inorganic particles with an average particle diameter of 1 μm or more and 6 μm or less. (6) A polyester film according to any one of (1) to (5) used as a release film for the process. [Effects of the Invention]

[0011] The present invention provides a polyester film that suppresses film adhesion during conveying processes and other stages, and exhibits good release properties during heating processes. Furthermore, it can be suitably used as a release film. [Modes for carrying out the invention]

[0012] A preferred embodiment of the film of the present invention is a polyester film in which, on at least one surface A of the polyester film, the rate of change in the amount of fatty acid-derived components, as determined by TOF-SIMS analysis after heat treatment at 170°C for 5 minutes under air, is 15% or more and 60% or less.

[0013] The polyester constituting the film of the present invention is a general term for polymer compounds in which the main bond in the main chain is an ester bond, and a polyester film is defined as one in which the polyester accounts for 50% by weight or more of the total resin constituting the film. The polyester resin can usually be obtained by polycondensation reaction of a dicarboxylic acid or its derivative with a glycol or its derivative.

[0014] As glycols or their derivatives for providing the polyester used in the present invention, in addition to ethylene glycol, aliphatic dihydroxy compounds such as diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; alicyclic dihydroxy compounds such as 1,4-cyclohexanedimethanol, spiroglycol; aromatic dihydroxy compounds such as bisphenol A, bisphenol S; and their derivatives may be mentioned. Among them, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol are preferably used in terms of moldability and handleability.

[0015] Also, as dicarboxylic acids or their derivatives for providing the polyester used in the present invention, in addition to terephthalic acid, aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; oxycarboxylic acids such as paraoxybenzoic acid; and their derivatives can be mentioned. Examples of the derivatives of dicarboxylic acids include esterified products such as dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl ester of terephthalic acid, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, dimethyl dimer acid. Among them, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and their esterified products are preferably used in terms of moldability and handleability.

[0016] The polyester film of the present invention may be a single layer or may have a laminated structure of two or more layers, but it is preferably a film having a base material layer (B) on one side of the A layer having surface A. By adopting a film structure having a base material layer on one side of the A layer, it is possible to maintain strength and suppress costs, which is preferable. The laminated structure may also be a three-layer structure of A layer / base material layer (B) / A layer. In the present invention, the layer with a high change rate of the fatty acid-derived component is defined as the A layer.

[0017] From the viewpoints of handling properties and film strength, the film thickness of the polyester film of the present invention is preferably 25 μm or more and 70 μm or less, more preferably 35 μm or more and 55 μm or less. If it is less than 25 μm, the film strength may not be sufficient and it may break in a pressing process or the like. If it is thicker than 70 μm, the cost may increase.

[0018] Also, from the viewpoints of curl suppression and the change rate of the fatty acid-derived component, the thickness of the A layer constituting the polyester film is preferably 1.0 μm or more and 10 μm or less, more preferably 2.0 μm or more and 8.0 μm or less. If it is less than 1.0 μm, the change rate of the fatty acid-derived component may be less than the specified value. If it is thicker than 10 μm, the film may be prone to curling and the handling properties in various processes may deteriorate.

[0019] Incidentally, the base material layer B layer may contain particles from the viewpoint of visibility. Inorganic particles are preferable from the viewpoint that they may form voids in the film when stretched and it is not necessary to add a white pigment for improving visibility. Organic particles are preferable from the viewpoint that voids are less likely to occur and the film strength does not decrease. Examples of the inorganic particles include silica, calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, titanium oxide, zirconium oxide, lithium fluoride, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and the like. The silica particles may contain, for example, hydrated silicon dioxide in addition to silicon dioxide (SiO2).

[0020] A preferred embodiment of the polyester film of the present invention is that the change rate of the fatty acid-derived component by TOF-SIMS analysis when heat-treated at 170 ° C for 5 minutes under air is 15% or more and 60% or less.

[0021] Heat treatment at 170 ° C for 5 minutes under air means that the film is placed in an oven at 170 ° C atmosphere and heat-treated while fixing the four sides so as not to shrink the film. Note that 170 ° C for 5 minutes is a condition assuming the press process when using it for the process film.

[0022] The change rate of the fatty acid-derived component by TOF-SIMS analysis indicates the increase in the component amount of the fatty acid-derived component after heat treatment with respect to the fatty acid-derived component on surface A of the untreated film. Specifically, using the peak intensity of the negative secondary ions observed by TOF-SIMS analysis, the peak intensity of the ion species ([[]] 121 C7H5O2 - ) derived from phthalic acid ester is set to 1, the peak intensities of various detected substances are normalized, and this is taken as the component amount. The ion species derived from fatty acids are 367 C 24 H 47 O2 - , 395 C 26 H 31 O2 - , 423 C 28 H 55 O2 - . Using the following formula, the component amount of the fatty acid-derived component is calculated and the change rate is calculated. When two or more ion species derived from fatty acids are detected, the change rate is calculated for each ion species, and the average value is taken as the change rate of the fatty acid-derived component. Note that the measurement and analysis conditions of TOF-SIMS are as described in the examples. <TOF-SIMS Analysis of Untreated Polyester Film> Peak intensity of ion species derived from phthalic acid ester: A Peak intensity of ion species derived from fatty acids: B Component amount of fatty acid-derived component: B / A <TOF-SIMS Analysis of Polyester Film after Heat Treatment> Peak intensity of ionic species derived from phthalate esters: C Peak intensity of fatty acid-derived ion species: D Fatty acid-derived component content: D / C Percentage change in fatty acid-derived components (%) = ((D / C) - (B / A)) / (B / A) × 100 By setting the rate of change of fatty acid-derived components to 15% or more and 60% or less, the peelability from the workpiece after the press heating process is improved, and adhesion can be suppressed. Preferably, it is 25% or more and 60% or less, more preferably 40% or more and 60% or less. If the amount of change is greater than 60%, the adhesion before pressing deteriorates, and problems such as misalignment may be more likely to occur.

[0023] To ensure that the rate of change of fatty acid-derived components is between 15% and 60%, it is preferable to add a wax compound. Here, the wax compound can be, for example, an ester compound of an aliphatic carboxylic acid compound and an aliphatic alcohol compound, or an amide compound of an aliphatic carboxylic acid compound and an aliphatic amine compound. Preferably, the compound has a total of 30 to 120 carbon atoms, and more preferably 40 to 100. Such compounds include, for example, synthetic or natural waxes consisting of aliphatic esters such as stearyl stearate, carnauba wax, candelilla wax, rice wax, pentaerythritol ful ester, behenyl behenate, palmyl myristate, and stearyl triglyceride, which are preferred in terms of compatibility with polyester. In particular, it is preferable to add carnauba wax in order to exhibit excellent release properties and non-adsorption properties even after repeated use, use after molding, and use in a water atmosphere, and among these, it is preferable to use purified carnauba wax.

[0024] From the viewpoint of ensuring that the rate of change in the amount of fatty acid-derived components on surface A after heat treatment is 15% to 60%, it is preferable that the layer constituting surface A contains one or more of either polybutylene terephthalate or polytrimethylene terephthalate. Through interaction with fatty acids, it is possible to more efficiently bleed out fatty acid-derived components from the surface A surface through heat treatment, thereby suppressing adhesion during the heat pressing process.

[0025] The polybutylene terephthalate referred to herein has terephthalic acid and 1,4-butanediol as polymerization components. It may also be copolymerized with other components, but it is preferable that it contains more than 50 mol% terephthalic acid per 100 mol% of the acid component and more than 50 mol% 1,4-butanediol per 100 mol% of the glycol component. The copolymerization components are not particularly limited, but examples of acid components include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfisoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, dicarboxylic acids such as cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid.

[0026] Furthermore, examples of glycol components include ethylene glycol, diethylene glycol, 1,3-propanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene oxide adducts of bisphenol A and bisphenol S.

[0027] Furthermore, small amounts of trifunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, and pentaerythritol may also be used.

[0028] Two or more of these copolymerization components may be used in combination.

[0029] Polytrimethylene terephthalate is obtained by polycondensation of terephthalic acid and 1,3-propanediol, but it is preferable that it contains more than 50 mol% terephthalic acid in 100 mol% of the acid component and more than 50 mol% of 1,3-propanediol in 100 mol% of the glycol component. Polytrimethylene terephthalate may be a polytrimethylene terephthalate homopolymer or a polytrimethylene terephthalate copolymer as shown below. That is, within a range that does not impair the effects of the present invention, acid components such as isophthalic acid, succinic acid, adipic acid, 2,6-naphthalenedicarboxylic acid, and tetrabutylposphonium sulfisoisophthalate, glycol components such as 1,4-butanediol, 1,6-hexanediol, and cyclohexanedimethanol, ε-caprolactone, 4-hydroxybenzoic acid, polyoxyethylene glycol, and polytetramethylene glycol may be copolymerized in amounts of less than 10% by mass.

[0030] In the present invention, it is preferable that the layer constituting one side A of the polyester film contains two or more of the following: polybutylene terephthalate, a block copolymer of polybutylene terephthalate and polyoxyalkylene glycol, and polytrimethylene terephthalate.

[0031] By including two or more of these components, the bleed-out of fatty acid-derived components before heating is further suppressed, improving adhesion. Furthermore, heating promotes the efficient bleed-out of fatty acid-derived components to surface A, thereby further suppressing adhesion during the pressing process.

[0032] Furthermore, it is more preferable that the film contains a block copolymer of polybutylene terephthalate and polyoxyalkylene glycol. The inclusion of a specific amount of flexible polyoxyalkylene glycol increases the crystallization rate and lowers Tcc, thereby further suppressing adhesion during the pressing process. Additionally, the fine dispersion of low-polarity components allows for more efficient bleeding out of fatty acid-derived components to the surface. The structure of the polyoxyalkylene glycol used in the film of the present invention is not particularly limited, but polytetramethylene glycol is preferred from the viewpoint of heat-press resistance and crystallinity, and it is also preferable that it is copolymerized as the glycol component of polyester.

[0033] The polyester film of the present invention preferably has a center surface mean roughness (SRa) of surface A of 0.60 μm or more and 2.00 μm or less, and a skewness (Ssk) of 0.5 or more and 1.5 or less, from the viewpoint of adhesion to the heating roll in the conveying process. If the center surface mean roughness of surface A is less than 0.60 μm, and the skewness is less than 0.5 or greater than 1.5, there is a possibility that the film will adhere to or fuse with the conveying roll, and if the center surface mean roughness is made greater than 2.00 μm, the strength of the film may decrease. From the viewpoint of suppressing adhesion to the conveying roll and film strength, the center surface mean roughness of surface A is preferably 0.60 μm or more and 2.00 μm or less, and more preferably 0.70 μm or more and 2.00 μm or less. The skewness is preferably 0.5 or more and 1.5 or less, and more preferably 0.5 or more and 1.2 or less.

[0034] In the present invention, there are no particular limitations on the method for setting the average roughness and skewness of the central surface of surface A to the above-mentioned specific range, but one example is the method of adding inorganic particles and / or organic particles to layer A constituting surface A. Here, there are no particular limitations on the inorganic particles and / or organic particles to be used, but for example, as inorganic particles, wet and dry silica, colloidal silica, aluminum silicate, calcium carbonate, calcium phosphate, aluminum oxide, etc., and as organic particles, particles composed of styrene, silicone, acrylic acids, methacrylic acids, polyesters, divinyl compounds, etc., can be used. Among these, it is preferable to use inorganic particles such as wet and dry silica, colloidal silica, and aluminum silicate, and particles composed of styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, etc. From an economic standpoint, wet and dry silica, colloidal silica, and aluminum silicate are particularly preferred. Note that two or more of these externally added particles may be used in combination.

[0035] Another method involves incorporating a polyester resin without a melting point, i.e., an amorphous polyester resin, into the layer constituting one side A of the polyester film. By incorporating an amorphous polyester resin, even if voids are generated around the particles when stretched, the resin flows easily during the heat treatment process, causing the voids to disappear. As a result, particle protrusions become clearly visible on the surface, making it easier to control the SRa and skewness within the preferred range of the present invention. On the other hand, if the amorphous polyester resin content is 30% by mass or more, the high fluidity of the resin during the heat treatment process can cause the particles to become embedded within the layer, resulting in extremely small SRa and skewness, which may fall outside the preferred range. Furthermore, if the amorphous polyester resin content is 30% by mass or more, the high fluidity of the resin may worsen the curlability of the film after film formation.

[0036] It is preferable that the layer constituting one side A of the polyester film of the present invention contains inorganic particles with an average particle diameter of 1 μm or more and 6 μm or less. If the average particle diameter is less than 1 μm, the particles may become embedded in layer A, resulting in insufficient average roughness of the central surface, and the film may adhere to the conveyor rolls during the conveying process, causing it to break. If the average particle diameter is greater than 6 μm, the particle diameter will be larger than that of layer A, which may lead to contamination during the conveying process due to particle shedding and a decrease in film strength. In addition, a larger average particle diameter may result in the appearance of the polyester film varying depending on the viewing angle, making it unattractive. In this invention, the average particle diameter refers to the number average diameter D, expressed as D = ΣDi / N (Di: equivalent circular diameter of the particle, N: number of particles).

[0037] The polyester film of the present invention has good visibility, and since the fatty acid-derived components efficiently increase on surface A when heated, it also has good release properties and can be suitably used as a process film.

[0038] Next, an example of a specific method for manufacturing the film of the present invention will be described, but the present invention is not to be interpreted as being limited to such examples.

[0039] When the film of the present invention is composed of layer A and base layer B constituting surface A, and polyester resin is used for both layers, each resin is supplied to a separate extruder and melt-extruded. In this case, it is preferable to control the resin temperature to 255°C to 295°C. Then, foreign matter is removed and the extrusion amount is equalized through filters and gear pumps, respectively, and the sheets are co-extruded from the T-die onto a cooling drum to obtain a laminated sheet. At this time, the sheet-like polymer is adhered to the casting drum and cooled and solidified by an electrostatic application method in which a high-voltage electrode is used to adhere the resin to the cooling drum with static electricity, a casting method in which a water film is created between the casting drum and the extruded polymer sheet, a method in which the casting drum temperature is set to the glass transition point of the polyester resin to (glass transition point - 20°C) to adhere the extruded polymer, or a method that combines several of these methods. Among these casting methods, when polyester is used, the electrostatic application method is preferred from the viewpoint of productivity and flatness, and from the viewpoint of suppressing curling during heating, a method in which a cooling nip roll is provided on the side opposite to the cooling drum is also preferably used. The film of the present invention is preferably a biaxially oriented film from the viewpoint of heat resistance and dimensional stability. A biaxially oriented film can be obtained by stretching an unstretched film by a sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then in the width direction, or by stretching it in the width direction and then in the longitudinal direction, or by a simultaneous biaxial stretching method in which the film is stretched in the longitudinal and width directions almost simultaneously.

[0040] In this stretching method, the stretching ratio in the longitudinal direction is preferably 2.8 to 3.4 times, more preferably 2.9 to 3.3 times. The stretching speed is preferably 1,000% / min to 200,000% / min. The stretching temperature in the longitudinal direction is preferably 70°C to 90°C. The stretching ratio in the width direction is preferably 2.8 to 3.8 times, more preferably 3 to 3.6 times. The stretching speed in the width direction is preferably 1,000% / min to 200,000% / min. The stretching temperature in the width direction is preferably 70°C to 180°C, but from the viewpoint of improving film strength, it is more preferable to set the temperature above the crystallization temperature of layer A. Furthermore, the film is heat-treated after biaxial stretching. The heat treatment can be performed by any conventionally known method, such as in an oven or on a heated roll. This heat treatment is performed at a temperature of 120°C or higher but below the peak melting temperature of polyester crystals. However, from the viewpoint of reducing voids around the particles in layer A, it is preferable to set the heat treatment temperature to a high temperature of 220°C or higher. Furthermore, from the viewpoint of reducing the rate of change in thermal dimensions in the range of 100°C to 150°C, it is also preferable to perform a relaxation treatment while gradually lowering the temperature after the heat treatment. More specifically, it is preferable to perform a relaxation heat treatment with a relaxation rate of 0.5% or more at the maximum heat treatment temperature (Tmax), and then perform one or more stages of relaxation heat treatment with a relaxation rate of 0.5% or more at a temperature of Tmax-50°C or higher but below Tmax-5°C. It is preferable to perform the relaxation heat treatment at Tmax-50°C or higher but below Tmax-5°C at least once in each temperature range of Tmax-25°C or higher but below Tmax-25°C. The relaxation heat treatment may be performed in either the longitudinal or widthwise direction, but when biaxial stretching is performed by sequential biaxial stretching, it is preferable from a productivity standpoint to perform the relaxation heat treatment continuously after stretching in the direction of the second stretching axis. [Examples]

[0041] (1) Composition of polyester Dissolve the polyester resin and film in hexafluoroisopropanol (HFIP), 1 H-NMR and13 The content of each monomer residue and by-product diethylene glycol can be quantified using 1C-NMR. In the case of laminated films, the components constituting each layer can be collected and evaluated by scraping off each layer of the film according to the laminate thickness. For the film of the present invention, the composition was calculated from the mixing ratio during film manufacturing.

[0042] (2) Intrinsic viscosity of polyester The intrinsic viscosity of polyester resins and films was measured at 25°C using an Ostwald viscometer after dissolving the polyester in orthochlorophenol. In the case of laminated films, the intrinsic viscosity of each individual layer was evaluated by scraping off each layer of the film according to the laminate thickness.

[0043] (3) Film thickness The film thickness was measured using a dial gauge.

[0044] (4) Thickness of each layer The film was embedded in epoxy resin, and a cross-section of the film was cut using a microtome. The cross-section was observed at 5000x magnification using a transmission electron microscope (Hitachi TEM H7100), and the thickness of each layer was determined. If the film surface had irregularities due to particles, the thickness was determined by taking the midpoint between the largest and smallest convex points as the film interface position.

[0045] (5) Average particle diameter of the particles The resin was removed from the film using a plasma low-temperature ashing treatment (Yamato Scientific PR-503 model) to expose the particles. These were observed with a transmission electron microscope (Hitachi TEM H7100), and the particle images (the intensity of light created by the particles) were linked to an image analyzer (Cambridge Instruments QTM900). The following numerical processing was performed on 100 particles at different observation points, and the resulting number-average diameter D was taken as the average particle diameter. D = ΣDi / N Here, Di is the equivalent circular diameter of the particle, and N is the number of particles.

[0046] (7) Particle content 1 g of polymer was added to 200 ml of 1N-KOH methanol solution and heated under reflux to dissolve the polymer. After dissolution, 200 ml of water was added to the solution, and the liquid was centrifuged to settle the particles, and the supernatant was removed. The particles were then washed with water and centrifuged twice more. The resulting particles were dried, and their mass was measured to calculate the particle content.

[0047] (8) Crystallinity of polyester The samples were measured using a differential scanning calorimeter EXSTAR DSC6220 manufactured by Hitachi High-Technologies Corporation, in accordance with the method based on JIS K 7122 (1999), as described below.

[0048] A 5 mg sample is weighed into an aluminum sample pan, and the sample is heated from 25°C to 300°C at a heating rate of 20°C / min (1st RUN). After rapidly cooling the sample to room temperature, it is heated again from 25°C to 300°C at a heating rate of 20°C / min (2nd RUN). A differential scanning calorimetry chart (with thermal energy on the vertical axis and temperature on the horizontal axis) is obtained for the 2nd RUN. If the magnitude of the endothermic peak in the differential scanning calorimetry chart for the 2nd RUN is 10 J / g or less, it is determined that the sample does not have crystallinity.

[0049] (9) TOF-SIMS Measurements were performed using the following equipment and conditions. • Measuring device: TOF-SIMS5 (manufactured by IONTOF) • Primary ion: Bi3 ++ • Secondary ion polarity: Negative • Mass range: 0 to 1500 • Raster size: 300μm□ • Number of scans: 32 scans ·Measurement vacuum degree: 4×10 -7 Pa or less • Primary ion acceleration voltage: 25kV Pulse width: 15.2ns ·Bunching: high mass resolution measurement • Neutralization of static charge: Yes ·Late acceleration: 9.5kV The intensity of the negative secondary ion peak was measured under the above conditions.

[0050] (10) Center surface average roughness SRa, skewness Ssk A sample measuring 4.0 cm in length and 3.5 cm in width was used, and the surface morphology of the film was measured under the following conditions by extending it three-dimensionally using a high-precision micro-shape measuring instrument (3D surface roughness meter) with a stylus method in accordance with JIS B0601-1994. • Measuring device: 3D micro-shape measuring instrument (manufactured by Kosaka Research Institute Co., Ltd., model ET-4000A) • Analysis equipment: 3D surface roughness analysis system (TDA-31 model) • Stylus: Tip radius 0.5 μmR, diameter 2 μm, made of diamond ·Stylus pressure: 100μN • Measurement direction: Average the measurement taken once in the longitudinal direction of the film and once in the width direction of the film. • X measurement length: 1.0 mm • X feed rate: 0.1 mm / s (measurement speed) • Y-feed pitch: 5 μm (measurement interval) • Number of Y-lines: 81 (number of measurements) • Z magnification: 20x (vertical magnification) • Low-frequency cutoff: 0.20mm • High-frequency cutoff: R+Wmm (roughness cutoff value). R+W means that there is no cutoff. • Filtering method: Gaussian space type • Leveling: Yes (slope correction) ·Reference area: 1mm Measurements were taken under the above conditions, and then the mean center surface roughness SRa and skewness Ssk were calculated using an analysis system.

[0051] (11) Glossiness In accordance with the method specified in JIS-Z-8741 (1997), the specular gloss at 60° and 85° was measured using a UGV-5D digital angle-distorting gloss meter manufactured by Suga Test Instruments, with N=3 for each measurement. The average values ​​were taken as the 60° gloss (G60) and 85° gloss (G85) of the present invention. Surface A was used for measurement, and a 0.35mm OK AC card (black) was placed on the opposite surface for measurement.

[0052] (12) Curl The film was cut into pieces measuring 100 mm in the longitudinal direction and 100 mm in the direction perpendicular to the longitudinal direction to form samples. These samples were heat-treated by leaving them in a 150°C hot air circulating oven for 5 minutes. After that, they were placed on a glass plate, and the amount of lift at the four corners in the direction perpendicular to the glass plate surface was measured, with the maximum height defined as the curl height. Three samples were measured for each sample, and the average value was calculated and evaluated according to the following criteria. A: Curl height less than 10mm B: Curl height between 10mm and less than 30mm C: Curl height of 30mm or more.

[0053] (13) Suppression of adhesion during the conveying process The film was cut to a size of 100 mm in the longitudinal direction and 100 mm in the direction perpendicular to the longitudinal direction to form a sample. The sample was placed on surface A so as to be in contact with a metal plate plated with HCr (hard chromium) with a roughness of 0.4s, a 2 kg weight was placed on the metal plate, and the sample was heat-treated by leaving it in a hot air circulating oven heated to 70°C for 5 minutes. After the heat treatment, once the metal plate had cooled to below 30°C, the sample was peeled off the metal plate, and the condition of the film at the time of peeling was evaluated according to the following criteria. A: The film could be peeled off the gold plate without resistance, and no tearing of the film occurred. B: The film was slightly adhered to the metal plate, but it peeled off easily. C: The film adhered tightly to the metal plate, causing it to stretch, tear, or otherwise change shape when removed.

[0054] (14) Suppression of adhesion in the pressing process A hard coat (HC) layer (UF-TCI-1, manufactured by Kyoeisha Chemical Co., Ltd.) was applied to the surface of the A layer of the film using an applicator to a thickness of 1.5 μm after drying, and then dried at 80°C for 10 minutes. Afterward, it was cut into 100 mm squares to obtain polyester film-HC laminate samples. Additionally, 3M (manufactured by 3M Limited) samples were used. TM I prepared some thin double-sided tape (model number 9077).

[0055] 3M on the HC of the above polyester film / HC laminate TM Thin double-sided tape (model number 9077) was applied using a hand roller to prevent air bubbles from forming, and a 0.125 mm thick polyimide film (Toray DuPont's "Kapton" (registered trademark) 500H / V) was applied on top of it. The film was then conditioned at 25°C and 60% RH for 24 hours. After that, with all four sides of the film fixed to prevent shrinkage, it was heat-treated in an oven at 170°C for 5 minutes. Three hours after being removed from the oven, the polyimide film was forcibly peeled off, and the condition of the polyester film at the time of peeling was evaluated according to the following criteria. A: Five peel tests were conducted, and in all five tests, the peel was easily removed without resistance. B+: Five peel tests were conducted. In one test, there was some resistance, but the polyester film could be peeled off without tearing or other damage. In four out of five tests, it could be peeled off easily without any resistance. B: Five peel tests were conducted, and while there was some resistance between two and three times, the polyester film could be peeled off without tearing or other damage. B-: After five peel tests, the film could be peeled off without tearing or other damage to the polyester film, although there was some resistance in four or more of the tests. C: After conducting five peel tests, the adhesion was strong and could not be peeled off at least once, or tearing occurred during the peeling process.

[0056] (Manufacturing of polyester resin) The polyester resin used for film formation was prepared as follows:

[0057] (Resin A) Polyester resin A with an intrinsic viscosity of 0.65 was obtained by polymerization of terephthalic acid and ethylene glycol using antimony trioxide as a catalyst by a conventional method.

[0058] (Resin B) The above polyester resin A was subjected to solid-phase polymerization by a conventional method to obtain polyester resin B with an intrinsic viscosity of 0.80.

[0059] (Resin C) A polyethylene terephthalate wax master with an intrinsic viscosity of 0.65, containing 2% by weight of carnauba wax in polyester resin A.

[0060] (Resin D) "Hytrel®" 7747 (block copolymer of polybutylene terephthalate and polyoxyalkylene glycol), manufactured by Toray Celanese Co., Ltd.

[0061] (Resin E) 100 parts by mass of dimethyl terephthalate and 80 parts by mass of 1,3-propanediol were reacted under a nitrogen atmosphere using tetrabutyl titanate as a catalyst, with the temperature gradually increased from 140°C to 230°C, while distilling off methanol during the transesterification reaction. Furthermore, a polycondensation reaction was carried out at a constant temperature of 250°C for 3 hours to obtain a polytrimethylene terephthalate resin with an intrinsic viscosity [η] of 0.86.

[0062] (Resin F) As a resin without a melting point, cyclohexanedimethanol copolymer polyethylene terephthalate resin (intrinsic viscosity 0.78) is obtained by copolymerizing 1,4-cyclohexanedimethanol with the glycol component at a concentration of 66 mol%.

[0063] (Resin G) A polybutylene terephthalate resin (intrinsic viscosity 1.20) containing 100 mol% terephthalate as the dicarboxylic acid component and 100 mol% 1,4-butanediol as the glycol component.

[0064] (Resin H) A copolymerized polyethylene terephthalate resin (intrinsic viscosity 0.80) is obtained by copolymerizing isophthalic acid with a dicarboxylic acid component at a concentration of 20 mol%, as a resin that does not have a melting point.

[0065] (particle 1) Aluminum silicate particles with an average particle size of 2.5 μm and a hexahedral shape.

[0066] (Particle Master 2) A polyethylene terephthalate particle masterbatch (intrinsic viscosity 0.60) containing barium sulfate particles (specific gravity 4.5) with an average particle diameter of 6.0 μm in resin A at a particle concentration of 50% by mass.

[0067] (Particle Master 3) A polyethylene terephthalate particle master containing 50% by mass of anatase-type titanium dioxide in resin A (intrinsic viscosity 0.60).

[0068] (Particle Master 4) A polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing aggregated silica particles with an average particle diameter of 3.2 μm at a particle concentration of 20% by mass in resin A.

[0069] (Particle Master 5) A polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing aluminum silicate particles with an average particle diameter of 6.0 μm and a hexahedral shape at a particle concentration of 30% by mass in resin A.

[0070] (Particle Master 6) A polybutylene terephthalate particle master (intrinsic viscosity 0.70) containing aluminum silicate particles with an average particle size of 6.0 μm and a hexahedral shape in resin G at a particle concentration of 30% by mass. (Particle Master 7) A polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing aluminum silicate particles with an average particle diameter of 4.0 μm and a hexahedral shape in resin A at a particle concentration of 50% by mass.

[0071] (Example 1) Layer A, which constitutes surface A, was compounded with the composition and lamination ratio shown in the table. The raw materials for Layer A and the base layer B were supplied to the extruder, and the extruder cylinder temperature for Layer A was set to 270°C and the extruder cylinder temperature for Layer B to melt the material. The short tube temperature after the merger of Layers A and B was set to 275°C and the die temperature to 280°C, and the resin was extruded in a sheet form from the T-die onto a cooling drum whose temperature was controlled to 25°C, with a resin temperature of 280°C. At this time, electrostatic discharge was applied using a wire electrode with a diameter of 0.1 mm to ensure close contact with the cooling drum and to obtain an unstretched sheet. Next, before stretching in the longitudinal direction, the film temperature was raised with a heating roll, and the film was stretched 3.1 times in the longitudinal direction at a stretching temperature of 85°C, and immediately cooled with a metal roll whose temperature was controlled to 40°C. Subsequently, the film was stretched 3.6 times in the width direction at a stretching temperature of 90°C using a tenter-type transverse stretcher. Then, heat treatment was performed at 235°C inside the tenter, with a 5% relaxation applied in the width direction, to obtain a polyester film with a thickness of 45 μm (the thickness of each layer is as shown in the table) and a two-layer structure of layer A / layer B.

[0072] (Example 2) A polyester film with a thickness of 45 μm was obtained in the same manner as in Example 1, except that the structure was changed to a three-layer configuration of layer A / layer B / layer A.

[0073] (Examples 3, 4, and 5) A polyester film with a film thickness of 45 μm was obtained in the same manner as in Example 1, except that the thickness of layer A was set as shown in the table by changing the discharge amount of layer A.

[0074] (Examples 6 and 7) A polyester film with a thickness of 45 μm was obtained in the same manner as in Example 1, except that the amount of particles 1 contained in layer A constituting surface A was changed.

[0075] (Examples 8 and 16) A polyester film with a film thickness of 45 μm was obtained in the same manner as in Example 1, except that the resin composition constituting surface A was changed as shown in the table, and the raw materials were supplied to the extruder separately without compounding.

[0076] (Examples 9-15) A polyester film with a film thickness of 45 μm was obtained in the same manner as in Example 1, except that the resin composition constituting surface A was changed as shown in the table.

[0077] (Comparative Example 1) The raw materials were supplied to the extruder so that the composition and lamination ratio were as shown in the table. A polyester film with a thickness of 50 μm was obtained in the same manner as in Example 1, except that the widthwise stretching conditions in a tenter-type transverse stretcher were set to a stretching temperature of 100°C and a stretching ratio of 3.3 times, followed by heat treatment at 235°C for 15 seconds in the tenter, and then heat treatment at 175°C for 10 seconds while relaxing by 3.5% in the widthwise direction.

[0078] (Comparative Example 2) The raw materials were supplied to the extruder so that the composition and lamination ratio were as shown in the table. The film was then stretched 3.5 times in the width direction using a tenter-type transverse stretcher at temperatures of 110°C in the first half of stretching, 130°C in the middle of stretching, and 140°C in the latter half of stretching. The film was then heat-treated at 230°C in the tenter, and the heat treatment was carried out in the same manner as in Example 1, except that a 5% relaxation was applied in the width direction during the heat treatment. A polyester film with a thickness of 50 μm and a three-layer structure of A / B / A was obtained.

[0079] (Comparative Example 3) A polyester film with a thickness of 50 μm was obtained in the same manner as in Comparative Example 2, except that the composition was changed as shown in the table.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3]

[0083] [Table 4] [Industrial applicability]

[0084] The polyester film of the present invention has a change rate of 15% to 60% in the amount of fatty acid-derived components as determined by TOF-SIMS analysis after heat treatment at 170°C for 5 minutes in air on at least one surface A of the polyester film. This suppresses film adhesion and bonding during conveying processes and provides a polyester film with good release properties during heating processes. Furthermore, it can be suitably used as a release film.

Claims

1. A polyester film in which, on at least one surface A of the polyester film, the rate of change in the amount of fatty acid-derived components, as determined by TOF-SIMS analysis after heat treatment at 170°C for 5 minutes in air, is 15% or more and 60% or less.

2. The polyester film according to claim 1, wherein the layer constituting one side A of the polyester film contains one or more of polybutylene terephthalate and polytrimethylene terephthalate.

3. The polyester film according to claim 2, wherein the layer constituting one side A of the polyester film contains two or more of the following: polybutylene terephthalate, a block copolymer of polybutylene terephthalate and polyoxyalkylene glycol, and polytrimethylene terephthalate.

4. The polyester film according to claim 1 or 2, wherein the mean center surface roughness (SRa) of one surface A of the polyester film is 0.60 μm or more and 2.00 μm or less, and the skewness (Ssk) is 0.5 or more and 1.5 or less.

5. The polyester film according to claim 1 or 2, wherein the layer constituting one side A of the polyester film contains inorganic particles having an average particle diameter of 1 μm or more and 6 μm or less.

6. A polyester film according to claim 1 or 2, used as a release film for processing.

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