Polyester film, release film, method for manufacturing polyester film, and ceramic capacitor

Abstract

To provide a polyester film for producing a release film, which can prevent foreign matter from mixing into a peeling layer, and to provide a release film, a method for producing a polyester film, and a ceramic capacitor.SOLUTION: A polyester film comprises a polyester substrate and a particle-containing coating layer. The surface of the polyester substrate that is remote from the particle-containing coating layer is provided with a peeling layer, so that a release film is produced. The surface of the particle-containing coating layer that is remote from the polyester substrate is measured by X-ray photoelectron spectroscopy, resulting in a fluorine atom density of 0-1.0 atom% and a silicon atom density of 0-3.0 atom%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a polyester film, a release film, a method for manufacturing a polyester film, and a ceramic capacitor. [Background technology]

[0002] As electronic devices become more high-performance and smaller, there is a growing demand for higher performance and smaller size in the electronic components used in them. Among electronic components, multilayer ceramic capacitors, for example, are seeing an increase in the number of points they can be mounted on a circuit board, and there is a strong demand for miniaturization. In the manufacture of multilayer ceramic capacitors, it is common practice to fabricate a ceramic green sheet on a release film having a polyester film and a release layer, and then manufacture the multilayer ceramic capacitor using the fabricated ceramic green sheet. To miniaturize multilayer ceramic capacitors, there is a need to thin the above-mentioned ceramic green sheet.

[0003] Patent Document 1 discloses a release film that uses a polyester film substantially free of inorganic particles as a base material, has a release coating layer on one surface of the base material, and has a smooth coating layer containing particles on the other surface of the base material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2019 / 039264 [Overview of the project] [Problems that the invention aims to solve]

[0005] With the rapid miniaturization and increase in capacitance of ceramic capacitors in recent years, there is a growing demand for even thinner ceramic green sheets. Thinning of ceramic green sheets has progressed to, for example, about 2 μm. As ceramic green sheets become thinner, the influence of minute foreign matter and uneven surfaces on the release layer of the release film used in the manufacture of the ceramic green sheet on the performance of the ceramic green sheet becomes greater. Therefore, the release film requires even greater smoothness. The present inventors, referring to the technology described in Patent Document 1, investigated release films used in the manufacture of ceramic green sheets and found that, depending on the properties of the polyester film used in the release film, foreign matter from the environment may be mixed in when the release layer forming composition is applied to the polyester film to form the release layer. It has been found that foreign matter mixed into the release layer of the release film causes minute irregularities on the surface of the release layer, which affects the performance of the ceramic green sheet.

[0006] In view of the above circumstances, the present invention aims to provide a polyester film for manufacturing a release film that can suppress the incorporation of foreign matter into the release layer. Furthermore, the present invention aims to provide a release film, a method for manufacturing a polyester film, and a ceramic capacitor. [Means for solving the problem]

[0007] The inventors of the present invention have diligently studied and found that the above problems can be solved by the following configuration.

[0008] [1] A polyester film comprising a polyester substrate and a particle-containing coating layer, used for manufacturing a release film by forming a release layer on the surface of the polyester substrate, wherein the fluorine atom concentration is 0 to 1.0 atomic%, and the silicon atom concentration is 0 to 3.0 atomic%, as measured by X-ray photoelectron spectroscopy on the surface of the particle-containing coating layer opposite to the polyester substrate. [2] The polyester film according to [1], wherein the peak observed in the spectrum obtained by measuring the surface of the particle-containing coating layer opposite to the polyester substrate by X-ray photoelectron spectroscopy is a peak originating from silica and is derived from a silicon-containing compound. [3] The polyester film according to [1], wherein, when the surface of the particle-containing coating layer is analyzed by time-of-flight secondary ion mass spectrometry, the ratio (P / T) of the secondary ion intensity (P) of the highest fragment peak among the fragment peaks derived from dimethylsiloxane to the sum of the secondary ion intensities (T) of all detected fragment peaks is less than 0.001. [4] A polyester film according to any one of [1] to [3], wherein the polyester base material is substantially free of particles. [5] The surface free energy of the surface of the particle-containing coating layer opposite to the polyester substrate is 25-50 mJ / m². 2 The polyester film described in any of [1] to [4]. [6] A polyester film according to any one of [1] to [5], wherein the thickness of the particle-containing coating layer is 1 to 500 nm. [7] The polyester film according to any one of [1] to [6], wherein the particle-containing coating layer comprises at least one binder selected from the group consisting of acrylic resin, urethane resin, and olefin resin. [8] A polyester film according to any one of [1] to [7], wherein the absolute value of the peel charge on both sides of a polyester film corresponding to a circle with a diameter of 1.5 cm is 0.12 nC or less. [9] A release film comprising a polyester film as described in any of [1] to [8], and a release layer laminated on the surface of the polyester film opposite to the particle-containing coating layer.

[10] The release film described in [9] for use in the manufacture of ceramic green sheets.

[11] The release film according to [9] or

[10] , wherein the release layer contains a silicone resin. 〔12〕The surface free energy on the surface of the release layer opposite to the polyester base material is 10 to 35 mJ / m 2 and the surface average roughness is 0 to 5 nm, the release film according to any one of 〔9〕 to 〔11〕. 〔13〕The release film according to any one of 〔9〕 to 〔12〕, wherein the thickness of the release film is 40 μm or less. 〔14〕The release film according to any one of 〔9〕 to 〔13〕, wherein the particle-containing coating layer contains particles and a hydrocarbon-based surfactant. 〔15〕A method for producing a polyester film comprising a polyester base material and a particle-containing coating layer, wherein the polyester film is a polyester film used for producing a release film by forming a release layer on the surface on the polyester base material side, and a particle-containing coating layer forming composition containing particles and a hydrocarbon-based surfactant is applied to the surface of the polyester base material opposite to the surface on which the release layer is formed. 〔16〕A ceramic capacitor produced using a ceramic green sheet formed on the surface of the release layer of the release film according to any one of 〔9〕 to 〔14〕.

Advantages of the Invention

[0009] According to the present invention, a polyester film for producing a release film capable of suppressing the inclusion of foreign substances in the release layer can be provided. Further, according to the present invention, a release film, a method for producing a polyester film, and a ceramic capacitor can be provided.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0011] In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this specification, the amount of each component in a composition means the total amount of multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In this specification, "longitudinal direction" means the longitudinal direction of each film during the manufacturing of the polyester film or release film, and is synonymous with "conveying direction" and "machine direction". In this specification, "width direction" means the direction perpendicular to the longitudinal direction. In this specification, "orthogonal" is not limited to strictly orthogonal, but includes approximately orthogonal. "Approximately orthogonal" means that the directions intersect within a range of 90° ± 5°, preferably within a range of 90° ± 3°, and more preferably within a range of 90° ± 1°. Furthermore, in this specification, "film width" means the distance between the two ends in the width direction of the polyester film or release film.

[0013] [Polyester film] The polyester film according to the present invention (hereinafter also simply referred to as "polyester film") comprises a polyester substrate and a particle-containing coating layer, and is used to manufacture a release film by forming a release layer on the surface of the polyester substrate, wherein the fluorine atom concentration (hereinafter also simply referred to as "fluorine atom concentration") obtained by measuring the surface of the particle-containing coating layer opposite to the polyester substrate by X-ray photoelectron spectroscopy (XPS) is 0 to 1.0 atomic%, and the silicon atom concentration (hereinafter also simply referred to as "silicon atom concentration") obtained by measuring the above surface of the particle-containing coating layer by X-ray photoelectron spectroscopy is 0 to 3.0 atomic%.

[0014] When manufacturing a release film using a polyester film having the above configuration, the mechanism by which the inclusion of foreign matter in the release layer can be suppressed is not entirely clear, but the inventors of the present invention speculate as follows. In the polyester film of the present invention, the surface on the polyester substrate side (the surface of the polyester film opposite to the particle-containing coating layer; hereinafter also referred to as the "release layer forming surface") corresponds to the surface on which the release layer is formed, and the surface of the particle-containing coating layer opposite to the polyester substrate (hereinafter also simply referred to as the "surface of the particle-containing coating layer") corresponds to the transport surface that comes into contact with the transport member when transporting the polyester film or release film. The release layer forming composition used to form the release layer often contains a release agent and is prone to static electricity. Therefore, when the release layer forming composition is applied to the release layer forming surface, foreign matter in the environment may adhere to the release layer forming composition due to the influence of static electricity, etc., and as a result, foreign matter may be mixed into the formed release layer. In contrast, the polyester film according to the present invention is characterized in that the fluorine atom concentration obtained by measuring the surface of the particle-containing coating layer by XPS is 0 to 1.0 atomic%, and the silicon atom concentration obtained by measuring the surface of the particle-containing coating layer by XPS is 0 to 3.0 atomic%. By reducing the amount of compounds containing easily charged fluorine atoms and silicon atoms on the surface of the particle-containing coating layer, the charging of the release layer after contact with and separation from the release layer forming surface of the polyester film is suppressed, and the charging of the entire release film when applying the release layer forming composition is suppressed, which is presumed to have suppressed the inclusion of foreign matter in the release layer. Furthermore, based on the XPS measurement conditions described later, the above fluorine atom concentration and silicon atom concentration correspond to the content of fluorine atoms or silicon atoms in the ultrasurface region of the particle-containing coating layer, up to a depth of approximately 2 nm from the surface.

[0015] The polyester substrate and particle-containing coating layer of the polyester film will be described below. The polyester film may have an intermediate layer between the polyester substrate and the particle-containing coating layer.

[0016] <Polyester base material> A polyester substrate is a film-like object containing polyester resin as its main polymer component. Here, "main polymer component" refers to the polymer that is present in the largest quantity (by mass) of all polymers contained in the film-like object. The polyester substrate may contain one type of polyester resin, or it may contain two or more types of polyester resins.

[0017] [Polyester resin] Polyester resins are polymers having ester bonds in their main chain. Polyester resins are usually formed by polycondensation of dicarboxylic acid compounds and diol compounds, as described later. The polyester resin is not particularly limited, and known polyester resins can be used. Examples of polyester resins include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), and copolymers thereof. Among these, at least one selected from the group consisting of PET, PEN, and copolymers thereof is preferred, with PET being preferred.

[0018] The intrinsic viscosity of the polyester resin is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g. The melting point (Tm) of the polyester resin is preferably 220 to 270°C, and more preferably 245 to 265°C. The glass transition temperature (Tg) of the polyester resin is preferably 65 to 90°C, and more preferably 70 to 85°C.

[0019] The method for producing polyester resin is not particularly limited, and known methods can be used. For example, polyester resin can be produced by polycondensation of at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst. The following describes the materials used in the manufacture of polyester and the manufacturing conditions.

[0020] (Dicarboxylic acid compounds) Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or methyl aromatic dicarboxylic acids are preferred.

[0021] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, dimer acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of alicyclic dicarboxylic acid compounds include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

[0022] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfisoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorenic acid, as well as their methyl esters. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, with terephthalic acid being more preferred.

[0023] Dicarboxylic acid compounds may be used individually or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or copolymerized with other aromatic dicarboxylic acids such as isophthalic acid, or with aliphatic dicarboxylic acids.

[0024] (Diol compounds) Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0025] Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred. Examples of alicyclic diol compounds include cyclohexanedimethanol, spiroglycol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. Diol compounds may be used individually or in combination of two or more.

[0026] (catalyst) The catalyst used in the production of polyester resin is not particularly limited, and any known catalyst usable for the synthesis of polyester resin can be used. Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds are preferred from the viewpoint of catalytic activity and cost. The catalyst may be used alone or in combination of two or more. It is preferable to use at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds in combination with a phosphorus compound, and more preferably to use a titanium compound in combination with a phosphorus compound.

[0027] As the titanium compound, organic chelate titanium complexes are preferred. Organic chelate titanium complexes are titanium compounds that have an organic acid as a ligand. Examples of organic acids include citric acid, lactic acid, trimellitic acid, and malic acid. As a titanium compound, the titanium compounds described in paragraphs

[0049] to

[0053] of Japanese Patent Publication No. 5575671 can also be used, and the contents of the above publication are incorporated herein by reference.

[0028] (Terminal encapsulant) In the manufacture of polyester resin, end encapsulants may be used as needed. By using end encapsulants, structures derived from the end encapsulant are introduced to the ends of the polyester resin. The end-captive agent is not limited, and known end-captive agents can be used. Examples of end-captive agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds. As end-capturing agents, refer to the contents described in paragraphs

[0055] to

[0064] of Japanese Patent Publication No. 2014-189002, and the contents of the above publication are incorporated herein by reference.

[0029] (Manufacturing conditions) The reaction temperature when manufacturing polyester resin is not limited and can be set appropriately depending on the raw materials. The reaction temperature is preferably 260 to 300°C, and more preferably 275 to 285°C. The pressure is not limited and should be set appropriately according to the raw materials. The pressure is 1.33 × 10⁻⁶. -3 ~1.33 × 10 -5 MPa is preferred, 6.67 × 10 -4 ~6.67×10 -5 MPa is more preferable.

[0030] As a method for synthesizing polyester resin, the method described in paragraphs

[0033] to

[0070] of Japanese Patent Publication No. 5575671 can also be used, and the contents of the above publication are incorporated herein.

[0031] The polyester resin content in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polymer in the polyester substrate. There is no particular upper limit to the polyester resin content, and it can be appropriately set within a range of, for example, 100% by mass or less relative to the total mass of the polymer in the polyester substrate. When the polyester substrate contains polyethylene terephthalate, the polyethylene terephthalate content is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 100% by mass, relative to the total mass of polyester resin in the polyester substrate.

[0032] The polyester substrate may contain components other than polyester resin (for example, catalysts, unreacted raw material components, particles, and water). From the viewpoint of improving the smoothness of the release film, it is preferable that the polyester substrate is substantially free of particles. Examples of particles include those contained in the particle-containing coating layer described later. "Substantially particle-free" is defined as a polyester substrate in which, when elements derived from particles are quantitatively analyzed by X-ray fluorescence analysis, the particle content is 50 ppm or less relative to the total mass of the polyester substrate. Preferably, the particle content is 10 ppm or less relative to the total mass of the polyester substrate, and more preferably below the detection limit. This is because even without actively adding particles to the polyester substrate, contaminants derived from foreign substances, raw resins, or dirt adhering to the lines or equipment in the manufacturing process of the polyester substrate may detach and become mixed into the polyester substrate.

[0033] [Properties of polyester substrates] The polyester substrate is preferably a biaxially oriented polyester substrate. "Biaxial orientation" means the property of having molecular orientation in two axial directions. The molecular orientation is measured using a microwave transmission type molecular orientation meter (for example, MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The angle formed by the two axial directions is preferably within the range of 90° ± 5°, more preferably within the range of 90° ± 3°, and even more preferably within the range of 90° ± 1°. In the release film of the present invention, the biaxially oriented polyester base material preferably has molecular orientation in the longitudinal direction and the width direction. The biaxially oriented polyester base material can be produced, for example, by performing the stretching process described later on the polyester base material.

[0034] The density of the polyester base material is preferably 1.39 to 1.41 g / cm 3 and more preferably 1.395 to 1.405 g / cm 3 and even more preferably 1.398 to 1.400 g / cm 3 is even more preferred. The density of the polyester base material can be measured using an electronic specific gravity meter (product name "SD-200L", manufactured by Alpha Mirage Co., Ltd.).

[0035] The thickness of the polyester base material is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less in terms of controlling the peelability. The lower limit of the thickness is not particularly limited, but in terms of improving strength and workability, it is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 10 μm or more. The thickness of the polyester base material shall be measured using a continuous stylus type thickness gauge. Specifically, the thickness of the polyester base material is measured with a continuous stylus type thickness gauge over 10 m along the longitudinal direction. This measurement is performed at five different positions in the width direction. The arithmetic mean value of the obtained measurement values is taken as the thickness.

[0036] <Particle-containing coating layer> The particle-containing coating layer refers to a layer containing particles. By providing a particle-containing coating layer on at least one surface of the polyester substrate, the transportability of the polyester film and release film can be improved. Specifically, winding quality can be improved (blocking can be suppressed), the occurrence of scratches and defects during transport can be suppressed, and transport wrinkles can be reduced during high-speed transport. The particle-containing coating layer may be laminated so as to be in contact with the surface of the polyester substrate, or it may be laminated on the surface of the polyester substrate via another layer, but it is preferable that it be laminated so as to be in contact with the surface of the polyester substrate in terms of superior productivity.

[0037] [Composition of the particle-containing coating layer] This section describes each component contained in the particle-containing coating layer.

[0038] (particle) The average particle size of the particles contained in the particle-containing coating layer is not particularly limited, but is preferably 1 nm to 3 μm, more preferably 40 nm to 2 μm, and even more preferably 50 nm to 1 μm, in terms of superior transportability. Furthermore, in terms of superior transportability, it is preferable that the average particle diameter of the particles contained in the particle-containing coating layer is 50 to 500 nm, the thickness of the particle-containing coating layer is 1 to 200 nm (more preferably 30 to 130 nm), and the average particle diameter of the particles is greater than the thickness of the particle-containing coating layer.

[0039] The particles contained in the particle-containing coating layer may be of a single type or two or more types. When the particle-containing coating layer contains two or more types of particles with different average particle diameters, it is preferable that the particle-containing coating layer contains at least one type of particle whose average particle diameter falls within the above range, and it is more preferable that all two or more types of particles with different average particle diameters fall within the above range.

[0040] Examples of particles contained in the particle-containing coating layer include organic particles and inorganic particles. As organic particles, resin particles are preferred. Examples of resins constituting the resin particles include acrylic resins such as polymethyl methacrylate (PMMA), polyester resins, silicone resins, and styrene-acrylic resins. The resin particles may or may not have a crosslinked structure. Specifically, examples include non-crosslinked acrylic resin particles, crosslinked acrylic resin particles, and divinylbenzene crosslinked particles. In this specification, "acrylic resin" means a resin containing constituent units derived from acrylate or methacrylate. Examples of inorganic particles include silica particles (silicon dioxide particles, colloidal silica), titania particles (titanium oxide particles), calcium carbonate, barium sulfate, and alumina particles (aluminum oxide particles). Among these, silica particles are preferred from the viewpoint of improving haze and durability.

[0041] The shape of the particles is not particularly limited and can be, for example, rice grain-shaped, spherical, cubic, spindle-shaped, flaky, aggregated, or irregular. Aggregated means a state in which primary particles are aggregated. The shape of the aggregated particles is not limited, but spherical or irregular shapes are preferred.

[0042] As the aggregated particles, fumed silica particles are preferred. A commercially available example is the Aerosil series from Nippon Aerosil Co., Ltd. Colloidal silica particles are preferred as non-aggregated particles. Examples of commercially available products include the Snowtex series manufactured by Nissan Chemical Corporation.

[0043] From the viewpoint of transportability and the applicability of the release layer, the particle content in the particle-containing coating layer is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, and even more preferably 1 to 15% by mass, relative to the total mass of the particle-containing coating layer. Furthermore, the particle content is preferably 0.0001 to 0.01% by mass, and more preferably 0.0005 to 0.005% by mass, relative to the total mass of the polyester substrate.

[0044] (Surfactants) The particle-containing coating layer preferably contains a surfactant, as this improves the smoothness of the areas on its surface other than those where protrusions formed by the particles exist. In particular, for superior effects of the present invention, the particle-containing coating layer is more preferably composed of a hydrocarbon surfactant. Here, a hydrocarbon surfactant means a surfactant whose hydrophobic group (a group that acts on the interface) consists of an alkyl group. Hydrocarbon surfactants are preferably substantially free of fluorine and silicon atoms.

[0045] Examples of hydrocarbon-based surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, with anionic surfactants and / or nonionic surfactants being preferred, and anionic surfactants being more preferred. Examples of anionic hydrocarbon surfactants include alkyl sulfates, alkylbenzene sulfons, alkyl phosphates, and fatty acid salts. Examples of nonionic hydrocarbon surfactants include polyalkylene glycol mono- or dialkyl ethers, polyalkylene glycol mono- or dialkyl esters, and polyalkylene glycol monoalkyl esters / monoalkyl ethers. Examples of cationic hydrocarbon surfactants include primary to tertiary alkylamine salts and quaternary ammonium compounds. Examples of amphoteric hydrocarbon surfactants include surfactants that have both anionic and cationic parts in their molecule.

[0046] Examples of commercially available anionic surfactants include Rapisol® A-90, A-80, BW-30, B-90, and C-70 (all manufactured by NOF Corporation), NIKKOL® OTP-100 (all manufactured by Nikko Chemical Co., Ltd.), Kohacool® ON, L-40, and Phosphanol® 702 (all manufactured by Toho Chemical Industry Co., Ltd.), and Viewlight® A-5000 and SSS (all manufactured by Sanyo Chemical Industries, Ltd.). Examples of commercially available nonionic surfactants include Naroacty® CL-95 and HN-100 (product name: manufactured by Sanyo Chemical Industries, Ltd.), Risolex BW400 (product name: manufactured by Kofu Alcohol Industry Co., Ltd.), EMALEX® ET-2020 (all manufactured by Nippon Emulsion Co., Ltd.), and Surfinol® 104E, 420, 440, 465, and Dynol® 604, 607 (all manufactured by Nisshin Chemical Industry Co., Ltd.).

[0047] Anionic hydrocarbon surfactants are preferable to have multiple hydrophobic end groups in that they have improved smoothness. The hydrophobic end groups may be some of the hydrocarbon groups that the hydrocarbon surfactant has. For example, a hydrocarbon surfactant having a branched-chain hydrocarbon group at its end will have multiple hydrophobic end groups. Examples of anionic hydrocarbon surfactants having multiple hydrophobic end groups include sodium di-2-ethylhexyl sulfosuccinate (having four hydrophobic end groups), sodium di-2-ethyloctyl sulfosuccinate (having four hydrophobic end groups), and branched-chain alkylbenzene sulfonates (having two hydrophobic end groups).

[0048] One type of surfactant may be used, or two or more types may be used in combination. The surfactants used in combination may include two or more hydrocarbon-based surfactants, or one or more hydrocarbon-based surfactants may be combined with one or more other surfactants other than hydrocarbon-based surfactants. Other surfactants mentioned above include silicone-based surfactants and fluorine-based surfactants. For superior effects of the present invention, it is preferable that the total content of silicone-based surfactants and fluorine-based surfactants be low.

[0049] In terms of reducing the amount of fluorinated surfactant introduced, surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms are preferred. The perfluoroalkyl group with 1 to 4 carbon atoms may be linear or branched. Among these, surfactants having a linear perfluoroalkyl group with 1 to 4 carbon atoms or a branched perfluoroalkyl group with 3 carbon atoms are more preferred, and surfactants having a perfluoroalkyl group with 1 or 2 carbon atoms or a branched perfluoroalkyl group with 3 carbon atoms are even more preferred. Examples of the above-mentioned perfluoroalkyl groups include CF3-*, C2F5-*, C3F7-*, n-C4F9-*, and (CF3)2CF-*. Here, * indicates the bonding position with carbon atoms other than those substituted with fluorine atoms. It is preferable that the carbon atoms bonded to these perfluoroalkyl groups either have hydrogen atoms or are bonded only to carbon atoms.

[0050] Examples of commercially available fluorine-based surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms include Futergent® 100, 100C, 110, 150, 150H, 212M, 215M, 250, 251, 222F, 245F, 208G, FTX-218, DFX-18, 300, 310, 320, 400SW, 710FL, 683, 601AD, 602A, and 681 (all manufactured by Neos Co., Ltd.), as well as PF-136A, PF-156A, PF-151N, PF-636, PF-6320, PF-656, PF-6520, and PF-652-NF (all manufactured by OMNOVA).

[0051] When the particle-containing coating layer contains a surfactant, the surfactant content is preferably 0.1 to 10% by mass of the total mass of the particle-containing coating layer, more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 2% by mass, in terms of superior surface smoothness. When the particle-containing coating layer contains a hydrocarbon-based surfactant, the content of the hydrocarbon-based surfactant is preferably 25% by mass or more, and more preferably 40% by mass or more, relative to the total mass of the surfactant. The upper limit is not particularly limited and may be 100% by mass.

[0052] (binder) The particle-containing coating layer preferably contains a binder. A resin binder is preferred as the binder. Examples of resin binders include acrylic resin, urethane resin, polyester resin, and olefin resin. Among these, non-polyester resins are preferred as binders, and acrylic resins, urethane resins, or olefin resins are more preferred. The acrylic resin, urethane resin, or olefin resin is not particularly limited, and known resins can be used. Furthermore, the resin binder may be an acid-modified resin. The binder is preferably formed by coating it with an aqueous dispersion. Furthermore, as a binder, it is preferable to use one that substantially does not contain fluorine atoms and silicon atoms, as this offers superior effects compared to the present invention.

[0053] The acrylic resin is a resin containing structural units derived from at least one selected from acrylates and methacrylates (hereinafter also referred to as "(meth)acrylate"), and may be copolymerized with vinyl monomers such as styrene. The acrylic resin is not particularly limited, but it is preferable to contain structural units derived from (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and more preferable to contain structural units derived from (meth)acrylate having an alkyl group having 1 to 8 carbon atoms. The acrylic resin may contain an acid-modified component. The acrylic resin may contain constituent units derived from (meth)acrylic acid as the acid-modified component. Furthermore, the (meth)acrylic acid may form an acid anhydride or be neutralized with at least one selected from alkali metals, organic amines, and ammonia.

[0054] The acid value of the acrylic resin is preferably 30 mg KOH / g or less, and more preferably 20 mg KOH / g or less. The lower limit of the acid value is not particularly limited, for example, 0 mg KOH / g, but from the perspective of coating as an aqueous dispersion, 2 mg KOH / g or more is preferred. When an acrylic resin with a solubility parameter (SP value) far removed from that of a polyester resin is used, the compatibility between the acrylic resin and the polyester resin becomes insufficient, resulting in improved defect suppression during long-term storage. Such an acrylic resin can be obtained, for example, by adjusting it to satisfy at least one of the following: setting the acid value within the above range, and including constituent units derived from (meth)acrylate having alkyl groups with 1 to 12 carbon atoms. Adjusting it to satisfy both the above range for acid value and the inclusion of constituent units derived from (meth)acrylate having alkyl groups with 1 to 12 carbon atoms can further improve defect suppression performance during long-term storage.

[0055] The olefin resin can be any resin that contains olefin-derived structural units in its main chain. Having an olefin structure in the main chain results in insufficient compatibility with polyester resins, which in turn improves defect suppression performance during long-term storage. The olefin is not particularly limited, but alkenes having 2 to 6 carbon atoms are preferred, ethylene, propylene, or hexene are more preferred, and ethylene is even more preferred. The olefin-derived structural units in the polyolefin are preferably 50 to 99 mol%, and more preferably 60 to 98%, relative to the total structural units of the polyolefin.

[0056] As the olefin resin, an acid-modified olefin resin is preferred. Examples of acid-modified olefin resins include copolymers obtained by modifying the above-mentioned olefin resin with an acid-modifying component such as an unsaturated carboxylic acid or its anhydride.

[0057] Examples of commercially available acid-modified olefin resins include the Zaixen® series (manufactured by Sumitomo Seika Co., Ltd.), such as Zaixen AC, A, L, NC, and N; the Chemipearl® series (manufactured by Mitsui Chemicals, Inc.), such as Chemipearl S100, S120, S200, S300, S650, and SA100; and the Hitec® series (manufactured by Toho Chemicals, Inc.), such as Hitec S3121 and S3148K. Examples include the Arrowbase (registered trademark) series (manufactured by Unitika Ltd.), such as Arrowbase SE-1013, SE-1010, SB-1200, SD-1200, SD-1200, DA-1010, DB-4010, Hardlen AP-2, NZ-1004, NZ-1005 (manufactured by Toyobo Co., Ltd.), and Sepolsion G315, VA407 (manufactured by Sumitomo Seika Co., Ltd.). Furthermore, the acid-modified olefin resin described in paragraphs

[0022] to

[0034] of Japanese Patent Publication No. 2014-076632 can also be preferably used.

[0058] The urethane resin is not limited as long as it is a polymer having urethane bonds, and known urethane resins such as reaction products of polyisocyanate compounds and polyol compounds can be used. When using an aqueous dispersion containing urethane resin in the manufacture of a particle-containing coating layer, it is preferable that the aqueous dispersion contains a urethane resin having an acidic group (e.g., a carboxyl group), or contains a urethane resin and a dispersant. This improves the film-forming properties of the particle-containing coating layer. The desired SP value of the urethane resin can be achieved by adjusting, for example, at least one of the following: the structure of the raw material polyol compound, the hydrophobicity or hydrophilicity of the raw material polyol, the structure of the raw material polyisocyanate compound, and the hydrophobicity or hydrophilicity of the raw material polyisocyanate compound. By using a urethane resin adjusted to be hydrophobic in this way, the compatibility between the urethane resin and the polyester resin becomes insufficient, and as a result, the defect suppression performance during long-term storage can be further improved. Among urethane resins, urethane resins having a polyester structure (polyester-based urethane resins) are preferred because they are hydrophobic and can further improve defect suppression performance during long-term storage. Examples of commercially available urethane resins include Hydran® AP-20, AP-40N, and AP-201 (all manufactured by DIC Corporation), Takelac® W-605, W-5030, and W-5920 (all manufactured by Mitsui Chemicals, Inc.), Superflex® 210 and 130, and Elastron® H-3-DF, E-37, and H-15 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0059] The binder contained in the particle-containing coating layer may have a cross-linked structure. In other words, the particle-containing coating layer may be a cross-linked film. To form a binder having a crosslinked structure, one method is to form a particle-containing coating layer using a particle-containing coating layer forming composition containing a crosslinking agent, as described later.

[0060] The particle-containing coating layer may contain one type of binder or two or more types of binders. When the particle-containing coating layer contains a binder, the binder content is preferably 30 to 99.8% by mass, and more preferably 50 to 99.5% by mass, relative to the total mass of the particle-containing coating layer, in terms of suppressing defects.

[0061] (Other additives) The particle-containing coating layer may also contain additives other than the above-mentioned particles, surfactant, and binder. Examples of additives included in the particle-containing coating layer are crosslinking agents, waxes, antioxidants, ultraviolet absorbers, colorants, strengthening agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and mold inhibitors, which will be described later.

[0062] The wax is not particularly limited and may be either natural or synthetic. Examples of natural waxes include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, the lubricants described in section

[0087] of International Publication No. 2017 / 169844 may also be used. The wax content is preferably 0 to 10% by mass relative to the total mass of the particle-containing coating layer.

[0063] [Properties of the particle-containing coating layer] (Fluorine atom concentration, silicon atom concentration) The surface of the particle-containing coating layer of the polyester film of the present invention is characterized in that, when measured by XPS, the fluorine atom concentration is 0 to 1.0 atomic percent and the silicon atom concentration is 0 to 3.0 atomic percent. By setting the fluorine and silicon atom concentrations on the surface of the particle-containing coating layer within the above ranges, the fluorine and silicon atoms in the outermost surface region of the particle-containing coating layer can be reduced, thereby suppressing the electrostatic discharge of the polyester film before the release layer is applied. This is thought to suppress the inclusion of foreign matter in the release layer and further improve the coatability of the release layer.

[0064] In this specification, the XPS measurement of fluorine atom concentration and silicon atom concentration on the surface of a particle-containing coating layer shall be carried out by the following method: The analysis area of ​​the particle-containing coating layer shall be set to 100 μm × 100 μm, and X-rays shall be irradiated onto the surface of the particle-containing coating layer from a direction of 20 degrees, and the atomic concentration of all detected atoms shall be measured. The atomic concentration of fluorine atoms (atomic %) shall be calculated from the content of fluorine atoms relative to all detected atoms (fluorine atoms / total atoms). Similarly, the atomic concentration of silicon atoms (atomic %) shall be calculated from the content of silicon atoms relative to all detected atoms (silicon atoms / total atoms). Five XPS atomic concentration measurements shall be performed, and the average of the five calculated atomic concentrations shall be taken as the fluorine atom concentration and silicon atom concentration, respectively. If the concentration is below the detection limit, it shall be recorded as 0 atomic %,. As described above, by performing XPS measurements under the condition of irradiating the surface of the particle-containing coated layer with X-rays from a 20-degree angle, the content of fluorine atoms and silicon atoms in the outermost layer region up to a depth of approximately 2 nm from the surface of the particle-containing coated layer can be determined.

[0065] In the spectrum obtained by the XPS measurement described above, it is preferable that the peak originating from silica is observed as the peak originating from the silicon-containing compound.

[0066] The fluorine atom concentration described above is preferably 0 to 0.5 atomic percent, and more preferably 0 to 0.1 atomic percent, in terms of achieving superior effects according to the present invention. Furthermore, the silicon atom concentration is preferably 0 to 2.5 atomic percent, and more preferably 0 to 0.1 atomic percent, in terms of achieving superior effects according to the present invention.

[0067] The fluorine and silicon atom concentrations on the surface of the particle-containing coating layer can be adjusted by the type and amount of binder, surfactant, and / or crosslinking agent used in the preparation of the particle-containing coating layer. Specifically, by minimizing the use of raw materials containing fluorine and / or silicon atoms as binders, surfactants, and / or crosslinking agents, the fluorine and silicon atom concentrations can be adjusted to fall within the above range.

[0068] (Dimethylsiloxane content) When the surface of a particle-containing coating layer is analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the ratio (P / T) of the secondary ion intensity (P) of the highest fragment peak derived from dimethylsiloxane to the sum of the secondary ion intensities (T) of all detected fragment peaks is preferably less than 0.01, and more preferably less than 0.001. When the above ratio (P / T) on the surface of the particle-containing coating layer is within the above range, a polyester film with superior effects of the present invention can be obtained because there are fewer dimethylsiloxane-containing components such as silicone compounds on the surface of the particle-containing coating layer. Examples of fragments derived from dimethylsiloxane include SiC3H9 + Si2C5H 15 O + and Si3C5H 15 O3 + While these are some examples, the secondary ionic intensity of the fragment peak with the highest secondary ionic intensity among the fragment peaks derived from compounds having a dimethylsiloxane structure is adopted as the secondary ionic intensity (P). Details of the method for analyzing the surface of the particle-containing coating layer by TOF-SIMS will be described in the examples below.

[0069] (Thickness) The thickness of the particle-containing coating layer is not particularly limited, but is preferably 1 nm to 3 μm, and more preferably 1 to 500 nm, even more preferably 10 to 200 nm, and particularly preferably 40 to 150 nm, from the viewpoint of suitability for manufacturing the particle-containing coating layer and haze reduction. The thickness of the particle-containing coating layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM), and taking the arithmetic mean of the thicknesses of the section.

[0070] (Surface free energy) The surface free energy at the surface of the particle-containing coating layer is 25-65 mJ / m 2 Preferably, 25-50 mJ / m 2 More preferably, 25-45 mJ / m 2 More preferably, 30-45 mJ / m 2 That is particularly preferable. By keeping the surface free energy of the particle-containing coating layer within the above range, the deposition of impurities such as oligomers contained in the polyester substrate onto the particle-containing coating layer (especially deposition after long-term storage of the polyester film or release film) is suppressed, thereby suppressing defects in the ceramic green sheet. Oligomers are low-molecular-weight by-products that are generated during the polymerization of polyester and are components that are present as impurities in polyester substrates.

[0071] The surface free energy on the surface of the particle-containing coating layer is determined by using a contact angle meter (e.g., "DROPMASTER-501" manufactured by Kyowa Interface Chemical Co., Ltd.) at 25°C, dropping droplets of purified water, methylene iodide, and ethylene glycol onto the peeling surface, measuring the contact angle 1 second after the droplets adhere to the surface, and calculating the energy from the obtained contact angles according to the Kitazaki-Hata method. The "surface free energy" obtained by the above method is the sum of the polar component and the hydrogen bonding component of the surface free energy.

[0072] (Maximum protrusion height Sp, average surface roughness Sa) It is preferable that the surface of the particle-containing coating layer has protrusions (projections) formed by the particles contained in the particle-containing coating layer. In order to further suppress defects in the ceramic green sheet during manufacturing, the maximum protrusion height Sp on the surface of the particle-containing coating layer is preferably 600 nm or less. In particular, when the particle-containing coating layer contains inorganic particles, the maximum protrusion height Sp on the surface of the particle-containing coating layer is preferably 300 nm or less. There is no particular lower limit to the maximum protrusion height Sp, but it is preferably 10 nm or more. Furthermore, the average surface roughness Sa on the surface of the particle-containing coating layer is preferably 0 to 10 nm, and more preferably 0 to 5 nm.

[0073] The maximum protrusion height Sp and average surface roughness Sa of the particle-containing coating layer are determined by measuring the surface of the particle-containing coating layer using an optical interferometer (Hitachi High-Tech Corporation's "Vertscan 3300G Lite") under the following conditions, and then analyzing the data using the built-in data analysis software. For measuring the maximum protrusion height Sp, five measurements are taken at different positions, and the maximum value obtained is taken as the maximum protrusion height Sp (indicated as P in the built-in data analysis software). Similarly, for measuring the average surface roughness Sa, five measurements are taken at different positions, and the average value obtained is taken as the average surface roughness Sa. The specific measurement conditions are as follows: Measurement mode: WAVE mode Objective lens: 50x Measurement area: 186μm×155μm

[0074] <Particle-free layer> The polyester film may have a particle-free layer on the surface opposite to the particle-containing coating layer of the polyester substrate. The particle-free layer may be the same as the particle-containing coating layer, including its preferred embodiments, except that it does not contain particles. Examples of the particle-free layer include a non-polyester resin layer and an antistatic layer. The non-polyester resin layer is not particularly limited as long as it contains the non-polyester resin as a binder. The non-polyester resin layer preferably contains the surfactant, and more preferably contains the hydrocarbon-based surfactant. The antistatic layer is not particularly limited as long as it contains an antistatic agent as an additive. Known antistatic agents can be used for the antistatic layer. The antistatic layer is more preferably a non-polyester resin layer.

[0075] <Properties of polyester film> [Amount of separation and falling charge] The polyester film is preferably such that the absolute value of the peel charge on both sides (the surface of the particle-containing coating layer and the surface forming the release layer) corresponding to a circle with a diameter of 1.5 cm, measured at a temperature of 23°C and a relative humidity (RH) of 20%, is 0 to 0.12 nC (nanocoulombs), more preferably 0 to 0.11 nC, and even more preferably 0 to 0.1 nC. Here, the unit nC (nanocoulomb) is 10 -9 It is Coulomb. When the total amount of discharge charge falls within the above range, the effects of the present invention are more pronounced, and the coating properties of the discharge layer are improved.

[0076] The method for measuring the amount of electrostatic charge on both sides of a polyester film is as follows: The measuring device used comprises a platform on which a reference sample of polyester film (with the release layer formed on the upper surface) is placed, a head that can repeatedly press and peel the lower surface of the measurement sample against the upper surface of the reference sample by raising and lowering it vertically while holding the measurement sample of polyester film (with the surface of the particle-containing coating layer on the lower surface), and an electrometer connected to this head that can measure the amount of charge of the measurement sample. More specifically, a polyester film is cut into a circle with a diameter of 1.5 cm to prepare a measurement sample for measuring the amount of charge on the peel, and a rectangular piece measuring 13 cm x 4 cm is cut to prepare a reference sample for measuring the amount of charge on the peel. Next, the obtained polyester film samples are left for at least 2 hours in the environment of the measurement temperature and humidity described above. After that, the reference sample is placed on the stand of the measuring device, and the measurement sample is attached to the head. At this time, the peel-forming surface of the reference sample and the surface of the particle-containing coating layer of the measurement sample are positioned so that they face each other, with the peel-forming surface of the reference sample on the stand facing upwards and the surface of the particle-containing coating layer of the measurement sample attached to the head facing downwards. After static electricity is removed from the measurement sample, the head is raised or lowered to repeatedly press and peel the reference film against the measurement sample (contact pressure is 566 g / cm²). 2 (Contact time 2 seconds). Using the same sample, the amount of charge on the sample is measured after each of the 1st to 5th peelings, and the average of the measured values ​​is calculated. The sample is changed, and the contact position of the sample on the reference sample is also changed for each sample, and measurements are taken with a total of 4 samples. The average of all measurements is taken as the peeling charge. The measurements are taken in an environment with a temperature of 23°C and a relative humidity (RH) of 20%. Regarding the method for measuring the amount of electrostatic charge generated when peeling a polyester film, refer to the contents described in Japanese Patent Publication No. 2003-194865 (especially in sections

[0053] to

[0067] ), and the contents described in the above publication are incorporated herein by reference.

[0077] The amount of electrostatic charge on the peel can be adjusted by selecting the type and amount of the polyester substrate and the binder and surfactant components contained in the particle-containing coating layer. More specifically, the amount of electrostatic charge on the peel can be adjusted to the above range by selecting two materials that are closer in the triboelectric series from the group consisting of the polyester substrate, binder, and surfactant.

[0078] [Thermal shrinkage rate] The polyester film preferably has a heat shrinkage rate in the transport direction measured at a temperature of 150°C of 0 to 3.0%, more preferably 0 to 2.0%, and even more preferably 0 to 1.5%. Furthermore, the polyester film preferably has a heat shrinkage rate in the width direction measured at a temperature of 150°C of 0 to 2.0%, more preferably 0 to 1.5%, and even more preferably 0 to 1.0%. When the heat shrinkage rate of the polyester film is within the above range, the dimensional stability of the ceramic green sheet formed on the release film having the polyester film and release layer, and the dimensional stability of the ceramic green sheet after it has been peeled from the release film and laminated, are good, making it less likely for electronic components to fail. The methods for measuring each of the above-mentioned thermal shrinkage rates will be described in the examples below.

[0079] The thermal shrinkage rate of polyester film can be adjusted by selecting the heating or cooling conditions during the manufacturing process. More specifically, it can be adjusted by changing at least one of the conditions in the heat setting process, heat relaxation process, and cooling process, as described later.

[0080] <Method for manufacturing polyester film> This document describes a method for manufacturing polyester film. The method for producing the polyester film is not particularly limited as long as a polyester film having the above-described properties can be obtained, and known methods can be used. In particular, as a method for manufacturing polyester film, it is possible to produce polyester film with the above-mentioned characteristics with high productivity. An extrusion molding process to form an unstretched polyester substrate by extrusion molding, The process includes a first stretching step of stretching an unstretched polyester substrate in either the conveying direction or the width direction to form a uniaxially oriented polyester substrate, and a second stretching step of stretching the uniaxially oriented polyester substrate in the other direction, the conveying direction or the width direction to form a biaxially oriented polyester substrate, performed either in stages or simultaneously. A manufacturing method is provided which includes a particle-containing coating layer formation step, performed between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, by applying a particle-containing coating layer formation composition to one surface side of the polyester substrate to form a particle-containing coating layer. The preferred manufacturing method described above will be explained in detail below.

[0081] [Extrusion molding process] The extrusion molding process is a process of forming an unstretched polyester substrate by extrusion molding. More specifically, it is a process of extruding a molten resin containing the raw polyester resin into a film to form an unstretched polyester substrate. The raw polyester resin is the same as the polyester resin described in the section on polyester resin above. Furthermore, in order to produce a polyester substrate that is substantially free of particles, it is preferable to use particle-free polyester pellets during the extrusion molding process.

[0082] Extrusion molding is a method of molding raw material resin into a desired shape by, for example, using an extruder to push out a molten raw material resin. The molten material extruded from the extrusion die is formed into a film by cooling. For example, the molten material can be formed into a film by bringing it into contact with a casting roll and cooling and solidifying it on the casting roll. In cooling the molten material, it is preferable to further apply air (preferably cold air) to the molten material.

[0083] [Stretching process] The stretching process is a process that involves performing, either in stages or simultaneously, a first stretching step in which an unstretched polyester substrate is stretched in either the conveying direction or the width direction to form a uniaxially oriented polyester substrate, and a second stretching step in which the uniaxially oriented polyester substrate is stretched in the other direction, either the conveying direction or the width direction, to form a biaxially oriented polyester substrate. One of the first and second stretching steps is a longitudinal stretching step in which the polyester substrate is stretched in the transport direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first and second stretching steps is a transverse stretching step in which the polyester substrate is stretched in the width direction (hereinafter also referred to as "transverse stretching"). During stretching, the polyester polymers are arranged in each respective direction.

[0084] The stretching process described above may be simultaneous biaxial stretching, where longitudinal stretching and transverse stretching are performed at the same time, or it may be sequential biaxial stretching, where longitudinal stretching and transverse stretching are performed in stages. Examples of sequential biaxial stretching include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, and longitudinal stretching → longitudinal stretching → transverse stretching, with longitudinal stretching → transverse stretching being preferred. The following describes the process of longitudinal stretching followed by transverse stretching, but the above manufacturing method is not limited to this process.

[0085] The stretching ratio in the longitudinal stretching process is set as appropriate, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 4.0 times. The stretching speed in the longitudinal stretching process is preferably 800 to 1500% / second, more preferably 1000 to 1400% / second, and even more preferably 1200 to 1400% / second. Here, "stretching speed" is the value obtained by dividing the length Δd of the polyester substrate stretched in the transport direction per second in the longitudinal stretching process by the length d0 of the polyester substrate in the transport direction before stretching, expressed as a percentage. In the longitudinal stretching process, it is preferable to heat the unstretched polyester substrate. This is because heating facilitates longitudinal stretching.

[0086] In the transverse stretching process, it is preferable to preheat the uniaxially oriented polyester substrate before transverse stretching. Preheating the uniaxially oriented polyester substrate allows for easy transverse stretching. The stretching ratio in the width direction (lateral stretching ratio) of the uniaxially oriented polyester substrate in the transverse stretching process is not particularly limited, but it is preferably greater than the stretching ratio in the longitudinal stretching process. The stretching ratio in the transverse stretching process is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, and even more preferably 3.5 to 4.5 times. The stretching speed in the transverse stretching process is preferably 8 to 45% / second, more preferably 10 to 30% / second, and even more preferably 15 to 20% / second.

[0087] [Particle-containing coating layer formation process] The particle-containing coating layer formation process involves applying a particle-containing coating layer formation composition to one surface side of a polyester substrate to form a particle-containing coating layer. The particle-containing coating layer formation process is performed between the extrusion molding process and the first stretching process, between the first stretching process and the second stretching process, or after the stretching process. The particle-containing coating layer formed on one surface of the polyester substrate by the particle-containing coating layer formation process is the same as the layer described in the section on particle-containing coating layers above. The following describes how to apply the particle-containing coating layer-forming composition.

[0088] First, we will describe the composition for forming a particle-containing coating layer. A composition for forming a particle-containing coating layer can be prepared by mixing particles contained in the particle-containing coating layer, a binder added as needed, an additive added as needed, and a solvent. Examples of solvents include water and alcoholic solvents.

[0089] The particle-containing coating layer forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass, based on the total mass of the particle-containing coating layer forming composition. In other words, in a particle-containing coating layer forming composition, the total content of components other than the solvent (solids) is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass, relative to the total mass of the particle-containing coating layer forming composition.

[0090] The particles contained in the particle-containing coating layer forming composition, the binder added as needed, and the additives added as needed, including their preferred embodiments, are as described in the section on particle-containing coating layers above. In particular, in terms of its excellent suitability for manufacturing the polyester film of the present invention, the particle-containing coating layer forming composition preferably contains particles and a hydrocarbon surfactant, and more preferably contains particles, a hydrocarbon surfactant and a binder. With respect to each component other than the solvent in the particle-containing coating layer forming composition, it is preferable to adjust the content of each component in the particle-containing coating layer forming composition so that the content of each component relative to the total mass of solids in the particle-containing coating layer forming composition is the same as the preferred content of each component relative to the total mass of the particle-containing coating layer.

[0091] Furthermore, the particle-containing coating layer forming composition may also contain a crosslinking agent. There are no particular restrictions on the crosslinking agent; known agents can be used. Examples of crosslinking agents include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds, with oxazoline compounds and carbodiimide compounds being preferred. Examples of commercially available products include Carbodilite V-02-L2 (manufactured by Nisshinbo Inc.) and Epocross K-2020E (manufactured by Nippon Shokubai Inc.). For details on epoxy compounds, isocyanate compounds, and melamine compounds, refer to sections

[0081] to

[0083] of Japanese Patent Application Publication No. 2015-163457. Crosslinking agents described in sections

[0082] to

[0084] of International Publication No. 2017 / 169844 can also be preferably used. For carbodiimide compounds, refer to sections

[0038] to

[0040] of Japanese Patent Application Publication No. 2017-087421. For oxazoline compounds, carbodiimide compounds, and isocyanate compounds, the crosslinking agents described in sections

[0074] to

[0075] of International Publication No. 2018 / 034294 can also be preferably used. The crosslinking agent content is preferably 0 to 50% by mass relative to the total mass of the particle-containing coating layer. In a particle-containing coating layer forming composition, the preferred mass ratio of the crosslinking agent to the binder is 2 to 50% by mass.

[0092] The method for applying the particle-containing coating layer composition is not particularly limited, and known methods can be used. Examples of application methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating. The drying method for the particle-containing coating layer formation composition is not particularly limited, and known methods can be used. Examples include heating and drying in a high-temperature atmosphere drying oven, blowing hot air from a nozzle (for example, the method described in Japanese Patent Application Publication No. 2018-155482 and Japanese Patent Application Publication No. 2003-106767), heating with an infrared heater (for example, the method described in Japanese Patent Application Publication No. 2014-129909 and Japanese Patent Application Publication No. 2013-062066), drying by heat transfer using induction heating conveyor rollers, and drying by reduced pressure.

[0093] The particle-containing coating layer formation step is preferably performed between the first stretching step and the second stretching step. The heating temperature for forming the particle-containing coating layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0094] Furthermore, in order to improve the adhesion between the polyester substrate and the particle-containing coating layer, pretreatment such as anchor coating, corona treatment, and plasma treatment may be applied to the release layer forming surface of the polyester substrate before applying the particle-containing coating layer.

[0095] [Heat setting process] A method for manufacturing polyester film may include a heat-setting step as a heat treatment of the polyester film obtained in the stretching step, following the stretching step. In the heat-setting process, the polyester film obtained in the stretching process can be heated and heat-set. By crystallizing the polyester resin through heat-setting, shrinkage of the polyester substrate can be suppressed. The surface temperature of the polyester film in the heat-setting process (heat-setting temperature) is not particularly limited, but is preferably less than 240°C, more preferably 235°C or less, and even more preferably 230°C or less. The lower limit is not particularly limited, but is preferably 190°C or higher, more preferably 200°C or higher, and even more preferably 210°C or higher. The heating time in the heat setting process is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

[0096] [Thermal relaxation process] The method for manufacturing polyester film may include a heat relaxation step after the heat setting step. In the thermal relaxation process, it is preferable to thermally relax the polyester film, which has been thermally fixed in the thermal fixing process, by heating it at a lower temperature than that of the thermal fixing process. Thermal relaxation can alleviate residual strain in the polyester film. In the heat relaxation process, the surface temperature of the polyester film (heat relaxation temperature) is preferably 5°C or more lower than the heat fixing temperature, more preferably 15°C or more lower, even more preferably 25°C or more lower, and particularly preferably 30°C or more lower. That is, the heat relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, even more preferably 210°C or lower, and particularly preferably 200°C or lower. The lower limit of the thermal relaxation temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

[0097] [Cooling process] A method for manufacturing a polyester film may include a cooling step for cooling the heat-relaxed polyester film. In the above manufacturing method, the cooling rate of the polyester film in the cooling step is preferably more than 2000°C / min and less than 4000°C / min, more preferably between 2000 and 3500°C / min, even more preferably more than 2200°C / min and less than 3000°C / min, and particularly preferably between 2300 and 2800°C / min. To reduce thermal shrinkage and impart dimensional stability, the cooling rate of the polyester film in the cooling process is preferably between 500°C / min and less than 4000°C / min, more preferably between 700 and 3000°C / min, and even more preferably between 1000°C / min and less than 2500°C / min. Within this range, it becomes easier to suppress streak-like wrinkles that occur on the surface of the release layer of the release film, and it is possible to manufacture a ceramic green sheet with suppressed thickness unevenness. In the above cooling process, it is also preferable to include a step (expansion step) of expanding the heat-relaxed polyester film in the width direction. The expansion rate in the width direction of the polyester film due to the expansion process, that is, the ratio of the polyester film width at the end of the cooling process to the polyester film width before the start of the cooling process, is preferably 0% or more, more preferably 0.001% or more, and even more preferably 0.01% or more. There is no particular upper limit to the expansion rate, but it is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

[0098] In the above manufacturing method, a method for forming a particle-containing coating layer was described in which a particle-containing coating layer formation composition was applied in the particle-containing coating layer formation step. However, the method for forming the particle-containing coating layer is not limited to the above embodiment, and known methods can be used.

[0099] [Winding process] The above manufacturing method may include a winding step to obtain a roll of polyester film by winding up the polyester film obtained through the above steps.

[0100] [Trimming process] The above manufacturing method may further include a trimming step, before carrying out the above winding step, in which the polyester film is continuously cut along the conveying direction to cut off at least one end of the polyester film in the width direction.

[0101] [Particle-free layer formation process] A polyester film having a particle-free layer can be manufactured, for example, by performing a particle-free layer formation step in the above-mentioned method for manufacturing a polyester film, which involves applying a particle-free layer formation composition to the surface of the polyester substrate opposite to the surface on which the particle-containing coating layer is formed, thereby forming a particle-free layer. The particle-free layer formation step may be the same as the particle-free layer formation step described above, including its preferred embodiment, except that the particle-free layer formation composition is used instead of the particle-containing coating layer formation composition. The particle-free layer formation composition may be the same as the particle-containing coating layer formation composition described above, including its preferred embodiment, except that it does not contain particles, and the desired particle-free layer can be formed by appropriately changing its composition and / or properties.

[0102] [Other conditions] The conveying speed of the polyester film in each step of the polyester film manufacturing method other than the longitudinal stretching step is not particularly limited, but in the transverse stretching step, heat setting step, heat relaxation step, and cooling step, 50 to 200 m / min is preferred, and 80 to 150 m / min is more preferred in terms of productivity and quality.

[0103] In the manufacturing method described in detail above, a combination of two or more preferred embodiments is a more preferred embodiment.

[0104] [Release film] The release film of the present invention comprises the polyester film described above and a release layer laminated on the surface of the polyester film opposite to the particle-containing coating layer (the release layer forming surface). A release film can be manufactured, for example, by providing a release layer on the release layer-forming surface of the polyester film. The release layer may be provided directly on the surface of the polyester substrate, or it may be provided on the polyester substrate via another layer. In terms of superior smoothness, it is preferable to apply the release layer directly to the surface of the polyester substrate. It is also preferable to laminate the release layer onto the polyester substrate via a non-polyester resin layer or an antistatic layer. By laminating the release layer onto the polyester substrate via a non-polyester resin layer, the precipitation of oligomers from the polyester substrate can be suppressed, and the smoothness of the release layer can be further improved. Furthermore, by laminating the release layer onto the polyester substrate via an antistatic layer, the electrostatic charge generated after the particle-containing layer surface and the release layer-forming surface come into contact and separate can be suppressed, thereby suppressing the electrostatic charge of the entire release film when applying the release layer-forming composition, and further suppressing the inclusion of foreign matter in the release layer.

[0105] A functional layer, such as a ceramic green sheet, is formed on the surface of the release film opposite to the polyester substrate of the release layer (hereinafter also referred to as the "release surface") in a peelable manner. The release film is preferably for manufacturing ceramic green sheets. That is, it is preferable that the ceramic green sheet is formed on the release surface of the release film so that it can be peeled off. The release film will be described below using a release film for the manufacture of ceramic green sheets as an example, but the use of the release film of the present invention is not limited to the manufacture of ceramic green sheets.

[0106] <Exfoliation layer> The composition of the release layer is not particularly limited as long as it allows the ceramic green sheet to be manufactured in a way that makes it removable, as described above, but it is preferable that the release layer contains a release agent. The release agent is preferably a resin. The resin included in the release layer as the release agent is not particularly limited, but examples include silicone resin, fluororesin, alkyd resin, acrylic resin, various waxes, and aliphatic olefins. Silicone resin is preferred because it has superior release properties for ceramic green sheets.

[0107] Silicone resin refers to a resin that has a silicone structure within its molecule. Examples of silicone resins include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified resins, with reactive curable silicone resins being preferred. Examples of reactive curable silicone resins include addition reaction-type silicone resins, condensation reaction-type silicone resins, and ultraviolet or electron beam curable silicone resins.

[0108] Examples of silicone resins used in addition reactions include resins obtained by reacting polydimethylsiloxane, which has vinyl groups introduced to its terminals or side chains, with hydrodienesiloxane using a platinum catalyst and then curing the reaction. Examples of silicone resins used in condensation reactions include resins having a three-dimensional crosslinked structure, formed by condensing polydimethylsiloxane having OH groups at its ends with polydimethylsiloxane having H groups at its ends using an organotin catalyst. Examples of UV-curable silicone resins include those that utilize the same radical reaction as silicone rubber crosslinking, those that are photocured by introducing unsaturated groups, those that decompose onium salts with ultraviolet light or electron beams to generate strong acids, which then cleave epoxy groups and cause crosslinking, and those that are crosslinked by the addition reaction of thiols to vinylsiloxane. More specifically, examples include acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane.

[0109] The resin included as a release agent preferably has a crosslinked structure. In other words, the release layer is preferably a crosslinked film. A release layer containing a resin with a crosslinked structure as a release agent can be formed by using a release layer forming composition containing a crosslinking agent, as described later.

[0110] The release layer may contain resins other than the release agent (hereinafter also referred to as "other resins") in addition to the resin used as a release agent. Other resins that can be used include known resins, such as UV-curable resins and thermosetting resins. More specifically, these include acrylic resins, unsaturated polyester resins, melamine resins, epoxy resins, phenolic resins, and urethane resins. The release layer formation composition described later may contain other resins and polymerization initiators and / or catalysts, and the release layer may contain residues of the polymerization initiators and / or catalysts.

[0111] The release layer may contain additives in addition to the resin and other resins used as release agents. Examples of additives include light release additives and heavy release additives for adjusting the release force, adhesion enhancers, and antistatic agents.

[0112] The resin used as a release agent in the release layer may be used alone or in combination of two or more types. The content of the resin used as a release agent in the release layer is preferably 0.1 to 99.9% by mass, and more preferably 0.5 to 98% by mass, relative to the total mass of the release layer. If the release layer contains the above-mentioned other resins, the content of the other resins is preferably 0 to 98% by mass, and more preferably 1 to 95% by mass, relative to the total mass of the release layer. The remainder in the release layer other than the resin and other resins used as release agents may be the above-mentioned additives and / or residues of solvents, polymerization initiators, and catalysts contained in the release layer forming composition (described later) used to form the release layer.

[0113] <Properties of release film> [Thickness of the delamination layer] The thickness of the release layer is preferably 10 to 1000 nm, and more preferably 30 to 700 nm, in order to achieve a good balance between release performance and surface smoothness of the release layer. The thickness of the release layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM), and taking the arithmetic mean of the thicknesses of the section.

[0114] [Surface free energy of the delamination surface] The surface free energy of the release surface in a release film is 5-50 mJ / m². 2 Preferably, 10-35 mJ / m 2 This is preferable. When the surface free energy of the peeled surface is within the above range, the ceramic green sheet formed on the peeled surface becomes easier to peel off, and the applicability of the ceramic slurry when manufacturing the ceramic green sheet becomes better. The surface free energy of the delamination surface can be adjusted by the type of resin and additives used to form the delamination layer. The method for measuring the surface free energy of the peeled surface is the same as the method for measuring the surface free energy of the particle-containing coated layer described above.

[0115] [Maximum protrusion height Sp on the peeled surface, average surface roughness Sa] It is preferable that the peel surface be as smooth as possible, as this allows for a smoother ceramic green sheet to be formed on the peel surface. Specifically, the maximum protrusion height Sp of the peel surface is preferably 1 to 60 nm, more preferably 1 to 40 nm, and even more preferably 1 to 30 nm. Furthermore, the average surface roughness Sa of the peeled surface is preferably 0 to 10 nm, more preferably 0 to 5 nm, and even more preferably 0 to 2 nm. The maximum protrusion height Sp and average surface roughness Sa of the release surface can be adjusted by not incorporating particles into the release layer when forming it, and by selecting the resin and additives that form the release layer. The method for measuring the maximum protrusion height Sp and average surface roughness Sa of the peeled surface is the same as the method for measuring the maximum protrusion height Sp and average surface roughness Sa of the particle-containing coated layer described above.

[0116] [Thickness of the release film] The thickness of the release film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less, in terms of superior release properties. Furthermore, the thickness of the release film is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, in terms of improved strength and processability.

[0117] <Method for manufacturing release film> The method for producing the release film of the present invention is not particularly limited as long as it is a method for forming a release layer on the polyester substrate side of the polyester film. For example, one method is to apply a release layer forming composition to the surface of the polyester substrate opposite to the particle-containing coating layer, dry the coating film to remove the solvent, and then perform a step of forming a release layer (release layer forming step) by heating or irradiating with light as necessary.

[0118] The above-described release layer formation step can be performed, for example, on a polyester film manufactured by the polyester film manufacturing method described above. The release layer formed on one surface of the polyester substrate by the release layer formation process is the same as the layer described in the section on release layers above.

[0119] This section describes a composition for forming a peeling layer used in the peeling layer formation process. A composition for forming a release layer can be prepared by mixing a release agent, additives as needed, and a solvent. Examples of solvents include water, alcohol-based solvents, ether-based solvents, ketone-based solvents, and aromatic hydrocarbon-based solvents.

[0120] The release layer forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass, based on the total mass of the release layer forming composition. In other words, in the release layer forming composition, the total content of components other than the solvent (solids) is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass, based on the total mass of the release layer forming composition.

[0121] The release agent contained in the release layer forming composition, and any additives added as needed, are as described in the section on the release layer above, including their preferred embodiments. The release layer forming composition includes the above-mentioned resin and solvent, and may optionally include the above-mentioned additives and / or the above-mentioned catalyst used for curing the resin. Furthermore, the release layer-forming composition may also contain a crosslinking agent. The crosslinking agent is not particularly limited, and known agents can be used. Furthermore, the release layer-forming composition may also contain a polymerization initiator. Examples of polymerization initiators include photopolymerization initiators, and known ones can be used. With respect to each component other than the solvent in the release layer forming composition, it is preferable to adjust the content of each component in the release layer forming composition so that the content of each component relative to the total mass of solids in the release layer forming composition is the same as the preferred content of each component relative to the total mass of the release layer.

[0122] The method for applying the release layer-forming composition is not particularly limited, and known methods can be used. Specific examples of application methods include those described in the particle-containing coating layer formation step in the method for manufacturing polyester films. The heating temperature for forming the release layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0123] Furthermore, in order to improve the adhesion between the polyester substrate and the release layer, pretreatment such as anchor coating, corona treatment, and plasma treatment may be applied to the surface of the polyester substrate before applying the release layer.

[0124] <Applications of release film> The above-mentioned release film can suppress defects in the ceramic green sheet formed on the release surface, and therefore is preferably used as a release film (carrier film) for manufacturing ceramic green sheets for ceramic capacitors. The method for producing a ceramic green sheet using the above-mentioned release film is not particularly limited and can be carried out by known methods. For example, one method for producing a ceramic green sheet is to apply a prepared ceramic slurry to the release surface of the release film and dry and remove the solvent contained in the ceramic slurry to form a ceramic green sheet on the release surface. The method for applying the ceramic slurry is not particularly limited. For example, known methods such as applying a ceramic slurry, which is prepared by dispersing ceramic powder and a binder agent in a solvent, using a reverse roll method and removing the solvent by heating and drying can be applied. The binder agent is not particularly limited, and an example is polyvinyl butyral. The solvent is also not particularly limited, and an example is ethanol and toluene.

[0125] The ceramic green sheets produced in this manner are used to manufacture ceramic capacitors. Known methods can be applied to manufacture ceramic capacitors using ceramic green sheets, for example, the following methods. First, internal electrodes are provided on a laminate of release film and ceramic green sheet manufactured by the above method by applying or printing conductive paste. Next, the release film is removed from the laminate of ceramic green sheets, and the ceramic green sheets with internal electrodes are sequentially laminated. An intermediate laminate is then produced by pressing the resulting laminate. After cutting the intermediate laminate into the desired shape, the cut intermediate laminate is fired to obtain a ceramic body. Next, external electrodes that electrically connect to the internal electrodes are formed on the two end faces of the fired intermediate laminate using a conductive paste such as silver, thereby obtaining a ceramic capacitor.

[0126] Furthermore, the release film of the present invention can also be used as a protective film for dry film resists, a film for sheet molding such as decorative layers and resin sheets, a release film for process manufacturing such as semiconductor manufacturing processes, a release film for polarizing plate manufacturing processes, and a separator for adhesive films such as labels, medical and office supplies. [Examples]

[0127] The present disclosure will be further explained with reference to the following examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples may be modified as appropriate, as long as they do not deviate from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the following specific examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0128] 〔raw materials〕 The raw materials used to form the particle-containing coating layer are listed below.

[0129] (resin) A copolymer obtained by polymerizing acrylic resin 1, methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2. Acrylic resin 2: Copolymer obtained by polymerizing methyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, and methacrylic acid in a mass ratio of 47:26:20:7 Olefin resin: Zychsen® NC (manufactured by Sumitomo Seika Co., Ltd., acid-modified polyolefin) Urethane resin 1: Adekabon Titer (registered trademark) HUX-370 (manufactured by ADEKA Corporation, polyurethane) Urethane resin 2: Hydran (registered trademark) AP-40N (manufactured by DIC Corporation, polyurethane)

[0130] (Crosslinking agent) Crosslinking agent 1: Carbodilite (registered trademark) V-02-L2 (manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide compound) Crosslinking agent 2: Epocross (registered trademark) WS-700 (manufactured by Nippon Shokubai Co., Ltd., oxazoline group-containing polymer)

[0131] (particle) Particle 1: Snowtex (registered trademark) MP-2040 (manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 200 nm) Particle 2: Snowtex® ZL (manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 80 nm) Particle 3: Epostor (registered trademark) MX050W (manufactured by Nippon Shokubai Co., Ltd., cross-linked PMMA particles, average particle diameter 70 nm) • Particle 4: Nipol (registered trademark) UFN1008 (manufactured by Zeon Corporation, non-crosslinked styrene resin particles (styrene copolymer), average particle size 1.9 μm)

[0132] (Surfactants) W-1: Nonionic hydrocarbon surfactant (Naroacty® CL95, manufactured by Sanyo Chemical Industries, Ltd.) W-2: Anionic hydrocarbon surfactant (Rapizol® A-90, manufactured by NOF Corporation) W-3: Fluorine-based surfactant (Surflon® S-211, manufactured by AGC Seimi Chemical Co., Ltd., structure containing a linear perfluoroalkyl group with 6 or more carbon atoms) W-4: Silicone-based surfactant (BYK-346, manufactured by BYK) W-5: Fluorine-based surfactant (Futergent® 215M, manufactured by Neos Co., Ltd., contains a perfluoroisopropyl group and does not contain a linear perfluoroalkyl group with 6 or more carbon atoms)

[0133] [Example 1] [Extrusion molding process] Polyethylene terephthalate pellets were produced using a titanium compound (titanium citrate chelate complex, VERTEC AC-420, manufactured by Johnson Matthey) described in Japanese Patent No. 5575671 as a polymerization catalyst. Specifically, 1 ton (1000 kg) of terephthalic acid was mixed with 390 kg of ethylene glycol and the titanium compound in an amount that resulted in 9 ppm by mass of Ti atoms relative to the resulting polyethylene terephthalate. The resulting mixture was continuously supplied to a reactor for an esterification reaction. Furthermore, magnesium acetate tetrahydrate in an amount that resulted in 81 ppm by mass of Mg atoms relative to the resulting polyethylene terephthalate, and trimethyl phosphate in an amount that resulted in 73 ppm by mass of P atoms relative to the resulting polyethylene terephthalate were added to the mixture, and a polycondensation reaction was carried out to produce polyethylene terephthalate pellets. The obtained pellets were dried until their moisture content was 50 ppm or less, then placed into the hopper of a 30 mm diameter single-screw kneading extruder, and subsequently melted and extruded at 280°C. The molten material was passed through a filter (pore size 3 μm) and then extruded from the die into a cooling drum at 25°C to obtain an unstretched polyester substrate made of polyethylene terephthalate. The extruded molten material was then brought into close contact with the cooling drum by electrostatic application. The melting point (Tm) of polyethylene terephthalate, which constitutes the unstretched polyester substrate, was 258°C, and the glass transition temperature (Tg) was 80°C.

[0134] [Longitudinal stretching process] The above unstretched polyester substrate was subjected to a longitudinal stretching process using the following method. A uniaxially oriented polyester substrate was produced by passing a preheated, unstretched polyester substrate between two pairs of rolls with different peripheral speeds under the following conditions and stretching it in the longitudinal direction (conveying direction). (Longitudinal extension conditions) Preheating temperature: 75℃ Stretching temperature: 90℃ Stretching ratio: 3.4 times Stretching speed: 1300% / sec

[0135] [Particle-containing coating layer formation process] A particle-containing coating layer was formed by applying the following composition A1 (composition for forming a particle-containing coating layer) to one side of a longitudinally stretched uniaxially oriented polyester substrate using a bar coater, and drying the formed coating film with hot air at 100°C. In other words, composition A1 was in-line coated onto the uniaxially oriented polyester substrate. At this time, the amount of composition A1 applied was adjusted so that the thickness of the particle-containing coating layer formed after transverse stretching was 100 nm.

[0136] (Composition A1) Composition A1 was prepared by mixing the components listed below. The prepared composition A1 was subjected to filtration using a filter with a pore size of 6 μm (F20, manufactured by MAHLE FILES SYSTEMS, Inc.) and membrane degassing (2x6 radial flow superphobic, manufactured by POLIPORE, Inc.) to obtain composition A1. • Acrylic resin 1 (aqueous dispersion of a copolymer obtained by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2, solid content concentration 25% by mass, acid value 16 mg KOH / g) 167 parts by mass • Crosslinking agent 1 (carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Co., Ltd., diluted to 10% by mass) 16.8 parts by mass • Surfactant W-2 (Rapizol (registered trademark) A-90, sodium di-2-ethylhexyl sulfosuccinate, manufactured by NOF Corporation, 1% solid content by mass, diluted with water) 56 parts by mass • Particle 1 (Snowtex® MP-2040, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 200 nm, solid content concentration 40% by mass aqueous dispersion) 11 parts by mass ·Water 776 parts by mass

[0137] [Horizontal stretching process] A polyester substrate that had undergone a longitudinal stretching process and a particle-containing coating layer formation process was stretched in the width direction using a tenter under the following conditions to produce a biaxially oriented polyester substrate. (lateral stretching conditions) Preheating temperature: 100℃ Stretching temperature: 120℃ Stretching ratio: 4.2x Stretching speed: 50% / sec

[0138] [Heat setting process] The polyester film obtained by the above transverse stretching process was subjected to a heat setting process by heating it using a tenter under the following conditions to heat-set the polyester film. (Heat fixation conditions) Heat fixing temperature: 227℃ Thermal fixation time: 6 seconds

[0139] [Thermal relaxation process] Next, a thermal relaxation process was performed on the heat-fixed polyester film to relieve tension by heating it under the following conditions. In addition, during the thermal relaxation process, the film width was reduced compared to the end of the thermal fixing process by narrowing the distance between the gripping members of the tenter that grips both ends of the polyester film (tenter width). The thermal relaxation rate Lr shown below was calculated using the formula Lr = (L1 - L2) / L1 × 100, where Lr is the film width at the end of the thermal relaxation process and L1 is the film width at the start of the thermal relaxation process. (Thermal relaxation conditions) Thermal relaxation temperature: 190℃ Thermal relaxation rate Lr: 4%

[0140] [Cooling process] A cooling process was performed on the heat-relaxed polyester film under the following conditions. The cooling rate shown below was calculated by dividing the temperature difference ΔT (°C) between the film surface temperature measured when the film was loaded into the cooling section of the stretcher and the film surface temperature measured when it was removed from the cooling section by the cooling time ta, with the cooling time ta being the time the polyester film stayed in the cooling section from when it was loaded into the cooling section until it was removed from the cooling section. (Cooling conditions) Cooling rate: 2500℃ / min

[0141] [Winding process] After the polyester film was cooled in the cooling process, a trimming device was used to continuously cut the polyester film along the conveying direction at a position 20 cm from both ends in the width direction of the film, thereby trimming both ends of the film. Next, the trimmed polyester film was subjected to an extrusion process (knurling) up to 10 mm in the width direction from both ends, and then the polyester film was wound up with a tension of 40 kg / m. A biaxially oriented film (polyester film of Example 1) was prepared using the method described above. The obtained biaxially oriented film had a thickness of 31 μm, a width of 1.5 m, and a roll length of 7000 m.

[0142] [Exfoliation layer formation process] The obtained biaxially oriented film was unwound at a transport speed of 30 m / min, and a coating solution consisting of the following formulation B was applied to the side of the biaxially oriented film opposite to the particle-containing coating layer (the side without the particle-containing coating layer) using a slot die method. The coating film was then dried using a 120°C hot air dryer, and the film was wound up to produce a roll-shaped release film (a biaxially oriented film with a release layer). The thickness of the release layer after drying was 0.5 μm, and the surface free energy of the release surface was 15 mJ / m 2 The average surface roughness Sa was 2 nm.

[0143] (Formulation B: Coating solution for forming a peeling layer) • Addition reaction type silicone compound (manufactured by Toray Dow Corning Co., Ltd., SRX-345, release agent): 10 parts • Mixed solvent of toluene and methyl ethyl ketone (mixing ratio = 7:3 (mass ratio)): 490 parts Platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., SRX-212): 0.1 part The coating solution for forming the release layer was prepared by stirring and mixing the above components.

[0144] [Examples 2-16, Comparative Examples 1-2] As shown in Table 1, polyester films (biaxially oriented films) of Examples 2-16 and Comparative Examples 1-2 were prepared in the same manner as in Example 1, except that the types of particles, resin, and surfactant in the particle-containing coating layer and the thickness of the particle-containing coating layer were changed. A release layer was then applied to the surface of the prepared biaxially oriented films to produce release films. In Example 7, a polyester film was prepared in the same manner as in Example 6, except that the amount of surfactant was doubled. In Example 10, a polyester film was prepared in the same manner as in Example 9, except that a further 5 parts by mass of a fluorine-based surfactant (Futergent 215M, manufactured by Neos Co., Ltd., 1% by mass solids diluted with water) was added to the particle-containing coating layer forming composition. In Example 11, a polyester film was prepared in the same manner as in Example 1, except that a further 0.7 parts by mass of a nonionic surfactant (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd., 100% by mass solids) was added to the particle-containing coating layer forming composition. In the release films of Examples 2 to 16, similar to Example 1, the thickness of the release layer after drying was 0.5 μm, and the surface free energy of the release layer surface was 15 mJ / m². 2 The average surface roughness Sa was 2 nm.

[0145] 〔measurement〕 The following properties were measured for the release films obtained in each example and comparative example.

[0146] The thickness of the particle-containing coating layer was measured by cutting the release film using a microtome according to the method described above, exposing the cross-section, etching it with Ar ions to deposit Pt, and then observing it with a SEM (S-4800, Hitachi High-Tech).

[0147] Surface free energy of the particle-containing coated layer (unit: mJ / m 2As described above, the contact angle was calculated from the measured contact angles obtained by dropping droplets of purified water, methylene iodide, and ethylene glycol onto the surface of the particle-containing coating layer using a contact angle meter (DROPMASTER-501, manufactured by Kyowa Interface Chemical Co., Ltd.) at a temperature of 25°C.

[0148] The fluorine and silicon atom concentrations on the surface of the particle-containing coated layer were measured using an XPS instrument (PHI Quantera II, manufactured by ULVAC, Inc.) according to the method described above. In the above measurements, a monochromatic Al-Kα ray (25W / 15kV) was used as the X-ray source, and the surface of the particle-containing coated layer was irradiated with X-rays from a direction of 20 degrees to the surface of the particle-containing coated layer. In addition, an electron gun and a low-energy ion gun were used in combination for charge correction during the measurement. Furthermore, when analyzing the surface of the particle-containing coating layer by XPS using the method described above, and examining the spectrum obtained, only peaks originating from silica were observed in the peaks derived from silica, and no peaks originating from siloxane-containing compounds such as silicone compounds were observed. Therefore, the silicon atom concentration on the surface of the particle-containing coating layer obtained by the method described above was calculated as the ratio of the silicon atom content derived from the silica-derived peak to the total amount of atoms detected.

[0149] The maximum protrusion height Sp and average surface roughness Sa on the surface of the particle-containing coating layer were measured using an optical interferometer (Hitachi High-Tech Corporation's "Vertscan 3300G Lite") according to the method described above.

[0150] In each example and comparative example, the amount of peel charge (unit: nC) on the surface of the particle-containing coating layer and the surface of the polyester substrate, corresponding to a circle with a diameter of 1.5 cm, were measured for the polyester film before the formation of the release layer, according to the measurement method described above, under conditions of 23°C and 20% relative humidity (RH).

[0151] 〔evaluation〕 [Contamination of foreign matter in the delamination layer] Samples were prepared by cutting 30 m lengths of the release film obtained in each example and comparative example in the longitudinal direction. The reflected light reflected from the surface of the release layer side of the obtained samples was observed under a three-wavelength fluorescent lamp, and the performance in suppressing foreign matter contamination during release layer formation was evaluated according to the following criteria. (Evaluation Criteria) A: No foreign objects were observed. B: A foreign object was observed.

[0152] [Unevenness / defect (Evaluation 1)] 100 parts by mass of barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 8 parts by mass of polyvinyl butyral resin as a binder (manufactured by Sekisui Chemical Co., Ltd., product name "Eslec® B·K BM-2"), and 4 parts by mass of dioctyl phthalate as a plasticizer (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate grade 1) were mixed with 135 parts by mass of a mixture of toluene and ethanol (mass ratio 6:4). The resulting mixture was dispersed in a ball mill in the presence of zirconia beads, and then the beads were removed from the mixture to prepare a ceramic slurry. The release films obtained in each example and comparative example were stored for one week in a normal temperature and humidity environment. After storage, the ceramic slurry was applied to the surface of the release layer of the release film using a die coater in a width of 250 mm and a length of 10 m so that the film thickness after drying would be 1 μm. The coating was then dried in a dryer at 80°C for 1 minute. The ceramic green sheet-attached release film prepared by the above method was cut to a width of 250 mm and a length of 250 mm. Ten of the resulting ceramic green sheet-attached release films were stacked so that the surface of the ceramic green sheet and the surface of the particle-containing coating layer were in contact, and 1 kg / cm³ was applied to the resulting laminate. 2 The load was applied for 10 minutes. After that, all but the top three and bottom two sheets were removed, and the release film was peeled off from the removed ceramic green sheets to obtain ceramic green sheets for evaluating surface defects. The surface of the obtained ceramic green sheet was illuminated with light from a three-wavelength fluorescent lamp, and the surface of the ceramic green sheet was visually inspected. Based on the number of defects identified, the surface irregularities were evaluated according to the following evaluation criteria. (Evaluation Criteria) A: No defects were found in the ceramic green sheet. B: One or more defects were found in the ceramic green sheet.

[0153] [Unevenness defects (Evaluation 2)] The release films obtained in each example and comparative example were stored in a normal temperature and humidity environment for 3 months. A ceramic green sheet for evaluating surface defects was then prepared in the same manner as for surface defects (Evaluation 1), except that the release films used were those that had been stored. The fabricated ceramic green sheet was used to evaluate surface irregularities (evaluation 1) in the same manner as the surface irregularities.

[0154] 〔result〕 Table 1 describes the characteristics of the particle-containing coating layer in each example and comparative example, as well as the evaluation results.

[0155] In the table, the "Resin," "Crosslinking Agent," "Particles," and "Surfactant" columns under "Composition" for "Particle-Containing Coating Layer" indicate the types of raw materials used as components of the particle-containing coating layer in the particle-containing coating layer forming composition used for each example and comparative example. In Table 1, "-" indicates that the component is not present.

[0156] In the table, "Surface E" represents the surface free energy (unit: mJ / m) of the particle-containing coated layer. 2 ) represents. "F atom concentration" refers to the concentration of fluorine atoms, and "Si atom concentration" refers to the concentration of silicon atoms. "Sp" and "Sa" represent the "maximum protrusion height Sp (unit: nm)" and "average surface roughness Sa (unit: nm)" of the particle-containing coating layer, respectively. "Peeling charge" refers to the amount of peeling charge (unit: nC) on both sides of the polyester film.

[0157] [Table 1]

[0158] (TOF-SIMS analysis of the surface of a particle-containing coating layer) The surface composition of the particle-containing coating layer of the polyester films in each example and comparative example was analyzed using TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). The measurement apparatus and measurement range were as follows. The measurement conditions were set appropriately according to the measurement target, based on the conditions described in the instruction manual attached to the apparatus below. Equipment: (PHI nanoTOF II, manufactured by ULVAC-PHI, Inc.) Mass range: m / z=0~1000 Measurement range: 100 μm × 100 μm From the surface analysis results of the particle-containing coated layer, T is the sum of the secondary ion intensities of all fragment peaks detected by TOF-SIMS analysis, and the fragment peak with the highest secondary ion intensity among the fragment peaks derived from dimethylsiloxane (SiCH3) + The secondary ionic intensity of the fragment ion (peak M / Z=43) was defined as P, and its ratio P / T was calculated. As a result, the ratio P / T of the surface of the particle-containing coating layer on the polyester films prepared in Examples 1 to 16 was less than 0.001 in all cases. Since the peak intensity of the fragments derived from dimethylsiloxane was small, it was determined that the particle-containing coating layer on the polyester films prepared in each example and comparative example substantially did not contain any silicone compounds.

[0159] From the above, it was confirmed that the polyester films of Examples 1 to 16 according to the present invention have a better effect in suppressing the incorporation of foreign matter when forming a release layer on the surface of the polyester substrate compared to Comparative Example 1, in which the particle-containing coating layer contains a silicone-based surfactant, and Comparative Example 2, in which the particle-containing coating layer contains a fluorine-based surfactant.

[0160] Furthermore, it was confirmed that when the surface free energy of the particle-containing coating layer is 50 or less, it has the effect of suppressing the occurrence of unevenness defects in the ceramic green sheet formed on the peeled surface after long-term storage of the release film obtained by forming a release layer on the surface of the particle-containing coating layer (comparison of Examples 1 to 16).

[0161] For the polyester films obtained in Examples 1 to 16, the thermal shrinkage rates in the transport direction and width direction at a temperature of 150°C were measured according to the measurement method described later. As a result, the thermal shrinkage rates in the transport direction were all within the range of 1.29 to 1.61%, and the thermal shrinkage rates in the width direction were all within the range of 0.85 to 1.03%.

[0162] [Examples 21-26] Composition B1 (composition for forming a particle-free layer) was prepared by mixing the components of composition A1 (composition for forming a particle-containing coating layer) used in the particle-containing coating layer formation process of Example 1, excluding particle 1, and then performing filtration and degassing of the resulting mixture in the same manner as composition A1. In the [Particle-containing coating layer formation process] of Example 1, when applying composition A1 to one side of the longitudinally stretched uniaxially oriented polyester substrate with a bar coater, composition B1 was applied to the side of the polyester substrate opposite to the side on which the composition A1 coating film was formed with a bar coater to form a coating film of composition B1, and when drying the formed composition A1 coating film with 100°C hot air, the coating film of composition B1 was also dried with 100°C hot air. Except for these differences, a polyester film (biaxially oriented film) of Example 21 having a layer structure consisting of a particle-containing coating layer, a polyester substrate, and a particle-free layer was prepared according to the method of Example 1. At this time, the amount of composition B1 applied was adjusted so that the thickness of the formed particle-free layer was 100 nm.

[0163] Furthermore, in the particle-containing coating layer formation process of Examples 2-5 and 13, the components other than particles from the particle-containing coating layer forming composition were mixed, and then the resulting mixture was subjected to filtration and degassing to prepare particle-free layer forming compositions. Similar to Example 21, in the [particle-containing coating layer formation step], a coating film of the particle-free layer formation composition prepared above was formed on the side of the polyester substrate opposite to the side on which the coating film of the particle-containing coating layer formation composition was formed, using a bar coater, and the formed coating film of the particle-free layer formation composition was also dried with hot air at 100°C. Except for these differences, polyester films (biaxially oriented films) of Examples 22 to 26, each having a layer structure consisting of a particle-containing coating layer, a polyester substrate, and a particle-free layer, were prepared according to the methods described in Examples 2 to 5 and 13. The thickness of the formed particle-free layer was 100 nm.

[0164] According to the measurement method described above, the particle-containing coating layers of the polyester films prepared in Examples 21-26 were measured, and the thickness, surface free energy, surface fluorine atom concentration and silicon atom concentration, as well as the maximum surface protrusion height Sp and average surface roughness Sa, were all the same as those measured for the polyester films prepared in Examples 1-5 and 13, respectively. Furthermore, when the surface of the particle-containing coating layers of the polyester films in Examples 21-26 was analyzed by XPS using the method described above, only a peak originating from silica was observed as a peak originating from silicon or silicon-containing compounds, and no peaks originating from compounds having siloxane bonds, such as silicone compounds, were observed. In addition, when the surface composition of the particle-containing coating layer side of the polyester films in Examples 21-26 was analyzed using TOF-SIMS, the ratio P / T was less than 0.001 in all cases.

[0165] Following the method described in Example 1, a release layer was provided on the particle-free layer side of the polyester films of Examples 21 to 26 to produce the respective release films of Examples 21 to 26. In all of the release films obtained in Examples 21-26, the thickness of the release layer after drying was 0.5 μm, and the surface free energy of the release layer surface was 15 mJ / m². 2 The average surface roughness Sa was 2 nm. Furthermore, when the release films of Examples 21 to 26 were evaluated according to the evaluation method described above, the performance in suppressing foreign matter contamination during release layer formation, the unevenness defect (Evaluation 1), and the unevenness defect (Evaluation 2) were all rated "A". Furthermore, according to the measurement method described later, the thermal shrinkage rates in the transport direction and width direction of the polyester films obtained in Examples 21 to 26 were measured at a temperature of 150°C. The results showed that the thermal shrinkage rates in the transport direction and width direction were within the same range as those of Examples 1 to 16.

[0166] [Examples 31-46] In the above-mentioned [cooling step], a cooling step was performed on the polyester film that had been thermally relaxed in the heat relaxation step, under the condition of cooling at a cooling rate of 1500°C / min. Except for this, polyester films (biaxially oriented films) of Examples 31 to 46, each having a layer structure consisting of a particle-containing coating layer, a polyester substrate, and a particle-free layer, were prepared according to the methods described in Examples 1 to 16. According to the measurement method described above, the particle-containing coating layers of the polyester films prepared in Examples 31 to 46 were measured, and the thickness, surface free energy, surface fluorine atom concentration and silicon atom concentration, as well as the maximum protrusion height Sp and average surface roughness Sa, were all the same as those measured for the polyester films prepared in Examples 1 to 16.

[0167] [Measurement of thermal shrinkage rate] The polyester film obtained in Example 31 had its thermal shrinkage rate in the transport direction and width direction measured at a temperature of 150°C according to the measurement method described below. As a result, the thermal shrinkage rate in the transport direction was 1.38 to 1.50%, and the thermal shrinkage rate in the width direction was 0.83 to 0.90%. The method for measuring the thermal shrinkage rate of polyester film is as follows: For each polyester film, rectangular samples were cut out at five points along the width direction, with a length of 350 mm in the measurement direction (conveyor direction or width direction) and a length of 50 mm perpendicular to the measurement direction. Two gauge marks were made near both ends of the obtained sample in the measurement direction, spaced 300 mm apart. The obtained samples were placed in an oven adjusted to 150°C for 30 minutes, and then allowed to cool to room temperature. The distance between the gauge marks on the room temperature sample was measured and defined as L (mm). The heat shrinkage rate was calculated for each of the five samples using the following formula, and the maximum and minimum values ​​of the obtained heat shrinkage rates were expressed as the 150°C heat shrinkage rate for each measurement direction in the format "minimum value ~ maximum value %". Heat shrinkage rate at 150°C (%) = 100 × (300 - L) / 300

[0168] For the polyester films obtained in Examples 32 to 46, the thermal shrinkage rates in the transport direction and width direction at a temperature of 150°C were measured according to the measurement method described above. As a result, the thermal shrinkage rate in the transport direction was within the range of 1.38 to 1.50%, and the thermal shrinkage rate in the width direction was within the range of 0.83 to 0.90%.

[0169] According to the method described in the [Release Layer Formation Process] above, a release layer was provided on the side of the biaxially oriented film of Examples 31 to 46 opposite to the particle-containing coating layer (the side without the particle-containing coating layer), thereby producing the release films of Examples 31 to 46. The release films obtained in Examples 31 to 46 were evaluated using the above method for their performance in suppressing foreign matter contamination during release layer formation, and for unevenness defects (Evaluation 1) and unevenness defects (Evaluation 2). The evaluation results were the same as those for the release films in Examples 1 to 16.

Claims

1. It comprises a polyester substrate and a particle-containing coating layer, A polyester film used to manufacture a release film by forming a release layer on the surface of the polyester substrate, The polyester substrate is substantially free of particles, The particle-containing coating layer comprises particles and a hydrocarbon-based surfactant. The hydrocarbon surfactant is one to three types selected from the group consisting of anionic hydrocarbon surfactants, cationic hydrocarbon surfactants, and amphoteric hydrocarbon surfactants. A polyester film in which, when the surface of the particle-containing coating layer opposite to the polyester substrate is measured by X-ray photoelectron spectroscopy, the fluorine atom concentration is 0 to 1.0 atomic percent and the silicon atom concentration is 0 to 3.0 atomic percent.

2. The polyester film according to claim 1, wherein the peak observed in the spectrum obtained by measuring the surface of the particle-containing coating layer opposite to the polyester substrate by X-ray photoelectron spectroscopy is a peak originating from silica, and the peak originating from a silicon-containing compound is a peak originating from silica.

3. The polyester film according to claim 1, wherein, when the surface on the particle-containing coating layer side is analyzed by time-of-flight secondary ion mass spectrometry, the ratio (P / T) of the secondary ion intensity (P) of the highest fragment peak among the fragment peaks derived from dimethylsiloxane to the sum of the secondary ion intensities (T) of all detected fragment peaks is less than 0.

001.

4. The surface free energy of the particle-containing coating layer on the surface opposite to the polyester substrate is 25 to 50 mJ / m². ２ The polyester film according to claim 1.

5. The polyester film according to claim 1, wherein the thickness of the particle-containing coating layer is 1 to 500 nm.

6. The polyester film according to claim 1, wherein the particle-containing coating layer comprises at least one binder selected from the group consisting of acrylic resin, urethane resin, and olefin resin.

7. The polyester film according to claim 1, wherein the absolute value of the peel charge on both sides of the polyester film corresponding to a circle with a diameter of 1.5 cm is 0.12 nC or less.

8. A release film comprising a polyester film according to any one of claims 1 to 7, and a release layer laminated on the surface of the polyester film opposite to the particle-containing coating layer.

9. The release film according to claim 8, for use in manufacturing ceramic green sheets.

10. The release film according to claim 8, wherein the release layer contains a silicone resin.

11. The surface free energy of the release layer on the surface opposite to the polyester substrate is 10 to 35 mJ / m². ２ The release film according to claim 8, wherein the surface average roughness is 0 to 5 nm.

12. The release film according to claim 8, wherein the thickness of the release film is 40 μm or less.

13. A method for producing a polyester film comprising a polyester substrate and a particle-containing coating layer, The polyester film is a polyester film used to manufacture a release film by forming a release layer on the surface of the polyester substrate. The process includes applying a particle-containing coating layer-forming composition, which contains particles and a hydrocarbon-based surfactant, to the surface of the polyester substrate opposite to the surface on which the release layer is formed. The hydrocarbon surfactant is one to three types selected from the group consisting of anionic hydrocarbon surfactants, cationic hydrocarbon surfactants, and amphoteric hydrocarbon surfactants. A method for manufacturing polyester film.

14. A method for producing a polyester film according to claim 13, wherein the polyester substrate is substantially free of particles.

15. A method for manufacturing a ceramic capacitor, comprising manufacturing a ceramic capacitor using a ceramic green sheet formed on the surface of the release layer of the release film described in claim 8.

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