JP2023073192A - Polyester film, release film, method for producing polyester film, and ceramic capacitor - Google Patents

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

The present invention relates to a polyester film, a release film, a method for producing a polyester film, and a ceramic capacitor.

As electronic devices become more sophisticated and smaller, electronic components used in electronic devices are also required to have higher performance and smaller sizes. Among electronic components, for example, multilayer ceramic capacitors are mounted on substrates in increasing numbers, and there is a strong demand for miniaturization.
In the production of laminated ceramic capacitors, it is common to produce ceramic green sheets on a release film having a polyester film and a release layer, and produce laminated ceramic capacitors using the produced ceramic green sheets. In miniaturization of laminated ceramic capacitors, thinning of the ceramic green sheets is required.

In Patent Document 1, a polyester film that does not substantially contain inorganic particles is used as a base material, a release coating layer is provided on one surface of the base material, and particles are provided on the other surface of the base material. A release film is disclosed that has an easy-to-slip coating layer containing.

International Publication No. 2019/039264

With the recent rapid miniaturization and increase in capacity of ceramic capacitors, ceramic green sheets are required to be thinner. The thinning of ceramic green sheets has progressed to, for example, about 2 μm.
As the thickness of the ceramic green sheet becomes thinner, the performance of the release film becomes more affected by minute foreign matter and irregularities on the surface of the release layer of the release film used to manufacture the ceramic green sheet. is required to be more smooth.
The present inventors examined the release film used in the production of the ceramic green sheet with reference to the technique described in Patent Document 1, and found that depending on the properties of the polyester film possessed by the release film, the composition for forming a release layer It was found that foreign substances in the environment may be mixed in when forming a release layer by applying to a polyester film. It is known that foreign matter mixed in the release layer of the release film causes minute irregularities on the surface of the release layer, affecting the performance of the ceramic green sheet.

In view of the above circumstances, an object of the present invention is to provide a polyester film for producing a release film that can suppress contamination of the release layer with foreign matter.
Another object of the present invention is to provide a release film, a method for producing a polyester film, and a ceramic capacitor.

As a result of intensive studies aimed at solving the above problems, the inventors of the present invention have found that the above problems can be solved by the following configuration.

[1] A polyester film comprising a polyester substrate and a particle-containing coating layer, and used for producing a release film by forming a release layer on the surface of the polyester substrate, the polyester film containing the particles. The fluorine atom concentration is 0 to 1.0 atomic % and the silicon atom concentration is 0 to 3.0 when the surface of the coating layer opposite to the polyester base is measured by X-ray photoelectron spectroscopy. polyester film, in atomic %.
[2] A peak derived from a silicon-containing compound observed in a spectrum obtained by measuring the surface of the particle-containing coating layer on the side opposite to the polyester base material by X-ray photoelectron spectroscopy is due to silica. The polyester film according to [1], which is the derived peak.
[3] Fragments derived from dimethylsiloxane with respect to the total secondary ion intensity (T) of all fragment peaks detected when the surface of the particle-containing coating layer is analyzed by time-of-flight secondary ion mass spectrometry. The polyester film according to [1], wherein the ratio (P/T) of the secondary ion strength (P) of the highest fragment peak among the peaks is less than 0.001.
[4] The polyester film according to any one of [1] to [3], wherein the polyester base material is substantially free of particles.
[5] The polyester film according to any one of [1] to [4], wherein the surface of the particle-containing coating layer opposite to the polyester substrate has a surface free energy of 25 to 50 mJ/m ² .
[6] The polyester film according to any one of [1] to [5], wherein the particle-containing coating layer has a thickness of 1 to 500 nm.
[7] The polyester film according to any one of [1] to [6], wherein the particle-containing coating layer contains at least one binder selected from the group consisting of acrylic resins, urethane resins, and olefin resins.
[8] The polyester film according to any one of [1] to [7], wherein the absolute value of the peeling charge amount on both sides of the polyester film corresponding to a circle with a diameter of 1.5 cm is 0.12 nC or less.
[9] A release film comprising the polyester film according to any one 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 of [9], which is used for producing a ceramic green sheet.
[11] The release film of [9] or [10], wherein the release layer contains a silicone resin.
[12] The release layer has a surface free energy of 10 to 35 mJ/m ² and an average surface roughness of 0 to 5 nm on the surface opposite to the polyester base material, [9] to [11] ] The release film according to any one of the above.
[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 surfactant.
[15] A method for producing a polyester film comprising a polyester substrate and a particle-containing coating layer, wherein the polyester film forms a release layer on the surface of the polyester substrate side to produce a release film. A step of applying a particle-containing coating layer-forming composition containing particles and a hydrocarbon surfactant to the surface of the polyester substrate opposite to the surface on which the release layer is formed. A method of making a polyester film, comprising:
[16] A ceramic capacitor produced using a ceramic green sheet formed on the surface of the release layer of the release film of any one of [9] to [14].

ADVANTAGE OF THE INVENTION According to this invention, the polyester film for manufacturing a peeling film which can suppress the mixing of the foreign material in a peeling layer can be provided.
Moreover, according to this invention, the manufacturing method of a peeling film, a polyester film, and a ceramic capacitor can be provided.

The present invention will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits. In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described stepwise. Moreover, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.
As used herein, the amount of each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. do.
In this specification, the term "process" includes not only an independent process, but also if the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. be
In the present specification, a combination of two or more preferred aspects is a more preferred aspect.

As used herein, the term "longitudinal direction" means the longitudinal direction of each film during the production of the polyester film or release film, and is synonymous with the "conveyance direction" and the "machine direction."
As used herein, "width direction" means a direction perpendicular to the longitudinal direction. In this specification, "perpendicular" is not limited to strictly perpendicular, but includes substantially perpendicular. The term “substantially orthogonal” means intersecting within the range of 90°±5°, preferably intersecting within the range of 90°±3°, more preferably intersecting within the range of 90°±1°. .
Moreover, in this specification, "film width" means the distance between both ends of the polyester film or peeling film in the width direction.

[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 a release layer is formed on the surface of the polyester substrate side to produce a release film. Fluorine atom concentration ( Hereinafter, simply referred to as “fluorine atom concentration”) is 0 to 1.0 atomic %, and the silicon atom concentration obtained by measuring the surface of the particle-containing coating layer by X-ray photoelectron spectroscopy (hereinafter, It is a polyester film having a silicon atom concentration of 0 to 3.0 atomic %.

Although the mechanism by which foreign matter can be suppressed in the release layer when producing the release film using the polyester film having the above structure is not necessarily clear, the present inventors presume as follows.
In the polyester film of the present invention, the surface on the side of the polyester substrate (the surface on the side opposite to the particle-containing coating layer of the polyester film; hereinafter also referred to as “release layer forming surface”) corresponds to the surface on which the release layer is formed. The surface of the particle-containing coating layer on the side opposite to the polyester substrate (hereinafter also simply referred to as "the surface of the particle-containing coating layer") is the transport surface that comes into contact with the transport member when transporting the polyester film or release film. corresponds to The release layer-forming composition used to form the release layer often contains a release agent and is easily charged. The foreign matter may adhere to the release layer-forming composition, and as a result, the foreign matter may be mixed into the formed release layer.
On the other hand, in the polyester film according to the present invention, 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 surface of the particle-containing coating layer is It is characterized by having a silicon atom concentration of 0 to 3.0 atomic % as measured by XPS. By reducing the amount of the compound containing a fluorine atom and the compound containing a silicon atom, which are easily charged, on the surface of the particle-containing coating layer, the release electrification after coming into contact with and separating from the release layer forming surface of the polyester film is suppressed. It is speculated that contamination of the release layer with foreign matter could be suppressed because the charging of the entire release film could be suppressed when the composition for forming the release layer was applied.
From the XPS measurement conditions described later, each of the fluorine atom concentration and the silicon atom concentration is the concentration of fluorine atoms or silicon atoms in the extreme surface layer region up to a distance of about 2 nm in the depth direction from the surface of the particle-containing coating layer. Corresponds to the content rate.

The polyester base material and the particle-containing coating layer included in the polyester film are described below. The polyester film may have an intermediate layer between the polyester substrate and the particle-containing coating layer.

<Polyester base material>
A polyester substrate is a film-like body containing a polyester resin as the main polymer component. Here, the "main polymer component" means the polymer with the highest content (mass) among all polymers contained in the film-like substance.
The polyester base material may contain a single polyester resin, or may contain two or more polyester resins.

[Polyester resin]
A polyester resin is a polymer having an ester bond in its main chain. A polyester resin is usually formed by polycondensing a dicarboxylic acid compound and a diol compound, which will be 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. , PET, PEN, and copolymers thereof, preferably at least one selected from the group consisting of PET.

The intrinsic viscosity of the polyester resin is preferably 0.50 dl/g or more and less than 0.80 dl/g, 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, more preferably 245 to 265°C.
The glass transition temperature (Tg) of the polyester resin is preferably 65-90°C, more preferably 70-85°C.

The method for producing the polyester resin is not particularly limited, and known methods can be used. For example, a polyester resin can be produced by polycondensing at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.
The materials used for the production of polyester and the production conditions are described below.

(Dicarboxylic acid compound)
Examples of dicarboxylic acid compounds include dicarboxylic acids such as aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, and dicarboxylic acids such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. esters. Among them, aromatic dicarboxylic acid or methyl aromatic dicarboxylate is preferable.

Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid.
Alicyclic dicarboxylic acid compounds include, for example, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalinedicarboxylic acid.

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, and 1,8-naphthalenedicarboxylic acid. , 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenanthenedicarboxylic acid, and 9,9′-bis(4- carboxyphenyl)fluoric acid and their methyl esters.
Among them, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is more preferable.

Only one type of dicarboxylic acid compound may be used, or two or more types may be used in combination. When terephthalic acid is used as the dicarboxylic acid compound, terephthalic acid may be used alone, or may be copolymerized with another aromatic dicarboxylic acid such as isophthalic acid, or an aliphatic dicarboxylic acid.

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

Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neo Pentyl glycol may be mentioned, with ethylene glycol being preferred.
Alicyclic diol compounds include, for example, 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.
Only one kind of diol compound may be used, or two or more kinds thereof may be used in combination.

(catalyst)
The catalyst used for producing the polyester resin is not particularly limited, and any known catalyst that can be used for synthesizing the 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 them, titanium compounds are preferable from the viewpoint of catalytic activity and cost.
Only one kind of catalyst may be used, or two or more kinds thereof may be used in combination. 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, and phosphorus compounds is preferably used in combination with, and more preferably, a titanium compound and a phosphorus compound are used in combination.

As the titanium compound, an organic chelate titanium complex is preferred. Organic chelate titanium complexes are titanium compounds with organic acids as ligands.
Organic acids include, for example, citric acid, lactic acid, trimellitic acid, and malic acid.
As the titanium compound, titanium compounds described in [0049] to [0053] of Japanese Patent No. 5575671 can also be used, and the contents of the above publications are incorporated herein.

(Terminal blocking agent)
In the production of the polyester resin, if necessary, a terminal blocker may be used. By using the terminal blocking agent, a structure derived from the terminal blocking agent is introduced to the terminal of the polyester resin.
The terminal blocking agent is not limited, and known terminal blocking agents can be used. Examples of terminal blocking agents include oxazoline-based compounds, carbodiimide-based compounds, and epoxy-based compounds.
As the terminal blocking agent, the content described in [0055] to [0064] of JP-A-2014-189002 can also be referred to, and the content of the above publication is incorporated herein.

(manufacturing conditions)
The reaction temperature for producing the polyester resin is not limited, and may be appropriately set according to the raw materials. The reaction temperature is preferably 260-300°C, more preferably 275-285°C.
The pressure is not limited, and may be appropriately set according to the raw material. The pressure is preferably 1.33×10 ⁻³ to 1.33×10 ⁻⁵ MPa, more preferably 6.67×10 ⁻⁴ to 6.67×10 ⁻⁵ MPa.

As a method for synthesizing the polyester resin, the method described in [0033] to [0070] of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated herein.

The content of the polyester resin in the polyester base is preferably 85% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and 98% by mass with respect to the total mass of the polymer in the polyester base. % or more is particularly preferred.
The upper limit of the content of the polyester resin is not particularly limited, and can be appropriately set, for example, within a range of 100% by mass or less with respect to the total mass of the polymer in the polyester base material.
When the polyester base material contains polyethylene terephthalate, the content of polyethylene terephthalate is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, based on the total mass of the polyester resin in the polyester base material. 100% by mass is more preferred, and 100% by mass is particularly preferred.

The polyester base material may contain components other than the polyester resin (eg, catalyst, unreacted raw material components, particles, water, etc.).
From the viewpoint of improving the smoothness of the release film, it is preferable that the polyester base material does not substantially contain particles. Examples of the particles include particles contained in the particle-containing coating layer described below.
"Substantially free of particles" means that the content of particles is 50 mass with respect to the total mass of the polyester base material when quantitatively analyzing the elements derived from the particles by fluorescent X-ray analysis for the polyester base material. It is defined as being less than or equal to ppm. The content of the particles is preferably 10 ppm by mass or less, more preferably the detection limit or less, relative to the total mass of the polyester base material. This is because even if the particles are not actively added to the polyester base material, contaminants derived from foreign substances, raw material resins, or stains attached to the lines or equipment in the manufacturing process of the polyester base material are peeled off, This is because they may be mixed into the base material.

[Properties of polyester base material]
Preferably, the polyester substrate is 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 still more preferably within the range of 90°±1°. The biaxially oriented polyester substrate in the release film of the present invention preferably has molecular orientation in the longitudinal direction and the width direction. The biaxially oriented polyester base material can be produced, for example, by subjecting the polyester base material to the stretching process described below.

The density of the polyester base material is preferably 1.39 to 1.41 g/cm ³ , more preferably 1.395 to 1.405 g/cm ³ and even more preferably 1.398 to 1.400 g/cm ³ .
The density of the polyester base material can be measured using an electronic hydrometer (product name “SD-200L”, manufactured by Alpha Mirage).

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, from the viewpoint of being able to control the releasability. Although the lower limit of the thickness is not particularly limited, it is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 10 μm or more in terms of improving strength and workability.
The thickness of the polyester base material should be measured using a continuous stylus type film thickness meter. Specifically, the thickness of the polyester base material is measured over 10 m along the longitudinal direction with a continuous stylus film thickness gauge. This measurement is performed at five different positions in the width direction. Let the arithmetic mean value of the obtained measured value be thickness.

<Particle-containing coating layer>
A particle-containing coating layer refers to a layer containing particles.
By providing the particle-containing coating layer on at least one of the surfaces of the polyester substrate, the transportability of the polyester film and the release film can be improved. Specifically, the winding quality can be improved (blocking can be suppressed), the occurrence of scratches and defects during transportation can be suppressed, and wrinkles during high-speed transportation can be reduced.
The particle-containing coating layer may be laminated so as to be in contact with the surface of the polyester base material, or may be laminated on the surface of the polyester base material via another layer. It is preferably laminated so as to be in contact with the surface of the polyester base material.

[Composition of particle-containing coating layer]
Each component contained in the particle-containing coating layer will be described.

(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, from the viewpoint of better transportability.
In terms of better transportability, 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), Moreover, the average particle diameter of the particles is preferably larger than the thickness of the particle-containing coating layer.

The particles contained in the particle-containing coating layer may be used alone or in combination of two or more.
When the particle-containing coating layer contains two or more types of particles having different average particle sizes, the particle-containing coating layer preferably contains at least one type of particles having an average particle size within the above range, and the particles having different average particle sizes It is more preferable that both of the two or more kinds of particles have an average particle size within the above range.

Examples of particles contained in the particle-containing coating layer include organic particles and inorganic particles.
Resin particles are preferable as the organic particles. Examples of the resin constituting the resin particles include acrylic resins such as polymethyl methacrylate resin (PMMA), polyester resins, silicone resins, and styrene-acrylic resins. The resin particles may or may not have a crosslinked structure. Specific examples include non-crosslinked acrylic resin particles, crosslinked acrylic resin particles, and divinylbenzene crosslinked particles.
In addition, in this specification, an acrylic resin means a resin containing structural 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 the above, the inorganic particles are preferably silica particles from the viewpoint of further improving haze and durability.

The shape of the particles is not particularly limited, and examples thereof include rice grain-like, spherical, cubic, spindle-like, scaly, aggregated, and irregular shapes. Aggregate means a state in which primary particles are aggregated. Although the shape of the aggregated particles is not limited, spherical or irregular shapes are preferred.

Fumed silica particles are preferred as aggregated particles. Commercially available products include, for example, the Aerosil series of Nippon Aerosil Co., Ltd.
Colloidal silica particles are preferred as the non-aggregated particles. Commercially available products include, for example, the Snowtex series manufactured by Nissan Chemical Industries, Ltd.

The content of the particles in the particle-containing coating layer is preferably 0.1 to 30% by mass, preferably 1 to 25% by mass, based on the total mass of the particle-containing coating layer, from the viewpoint of transportability and coatability of the release layer. %, more preferably 1 to 15% by mass.
Also, the content of the particles is preferably 0.0001 to 0.01% by mass, more preferably 0.0005 to 0.005% by mass, relative to the total mass of the polyester base material.

(Surfactant)
The particle-containing coating layer preferably contains a surfactant from the viewpoint of improving the smoothness of areas other than the areas where protrusions formed by the particles exist on the surface.
Above all, the particle-containing coating layer more preferably contains a hydrocarbon-based surfactant in terms of better effects of the present invention. Here, the hydrocarbon-based surfactant means a surfactant in which the hydrophobic group (group acting on the interface) of the surfactant is composed of an alkyl group.
It is preferred that the hydrocarbon surfactant be substantially free of fluorine atoms and silicon atoms.

Examples of hydrocarbon surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Active agents are preferred, and anionic surfactants are more preferred.
Anionic hydrocarbon surfactants include, for example, alkyl sulfates, alkylbenzene sulfonates, alkyl phosphates, and fatty acid salts.
Nonionic hydrocarbon surfactants include, for example, polyalkylene glycol mono- or dialkyl ethers, polyalkylene glycol mono- or dialkyl esters, and polyalkylene glycol mono- or dialkyl esters/monoalkyl ethers.
Cationic hydrocarbon surfactants include primary to tertiary alkylamine salts and quaternary ammonium compounds.
Examples of amphoteric hydrocarbon-based surfactants include surfactants having both an anionic site and a cationic site in the molecule.

Examples of commercially available anionic surfactants include RAPISOL (registered trademark) A-90, A-80, BW-30, B-90, and C-70 (manufactured by NOF Corporation). , NIKKOL (registered trademark) OTP-100 (manufactured by Nikko Chemical Co., Ltd.), Kohakul (registered trademark) ON, L-40, and Phosphanol (registered trademark) 702 (manufactured by Toho Chemical Industry Co., Ltd.) (manufactured by Sanyo Chemical Industries, Ltd.), and Beaulight (registered trademark) A-5000 and SSS (manufactured by Sanyo Chemical Industries, Ltd.).
Commercially available nonionic surfactants include, for example, Naloacty (registered trademark) CL-95 and HN-100 (trade name: manufactured by Sanyo Chemical Industries, Ltd.), Resolex BW400 (trade name: KOKYU ALCOHOL KOGYO Co., Ltd.), EMALEX (registered trademark) ET-2020 (manufactured by Nippon Emulsion Co., Ltd.), and Surfynol (registered trademark) 104E, 420, 440, 465, and Dynol (registered trademark) 604, 607 (manufactured by Nissin Chemical Industry Co., Ltd.).

The anionic hydrocarbon-based surfactant preferably has a plurality of hydrophobic terminal groups in terms of further improving smoothness. The hydrophobic end group may be part of the hydrocarbon group of the hydrocarbon surfactant. For example, a hydrocarbon surfactant terminated with a hydrocarbon group having a branched chain structure will have a plurality of hydrophobic end groups.
Examples of anionic hydrocarbon surfactants having multiple hydrophobic terminal groups include di-2-ethylhexyl sodium sulfosuccinate (having four hydrophobic terminal groups), di-2-ethyloctyl sodium sulfosuccinate ( 4 hydrophobic end groups) and branched alkyl benzene sulfonates (2 hydrophobic end groups).

Only one surfactant may be used, or two or more surfactants may be used in combination.
As surfactants to be used in combination, two or more hydrocarbon surfactants may be combined, and one or more hydrocarbon surfactants and one or more other surfactants other than hydrocarbon surfactants It may be combined with an active agent.
Other surfactants mentioned above include silicone-based surfactants and fluorine-based surfactants. The total content of the silicone-based surfactant and the fluorine-based surfactant is preferably as small as possible in terms of the effects of the present invention.

A surfactant having a perfluoroalkyl group having 1 to 4 carbon atoms is preferable as the fluorine-based surfactant in that the introduction amount of the fluorine-based surfactant can be reduced. A perfluoroalkyl group having 1 to 4 carbon atoms may be linear or branched. Among them, surfactants having a linear perfluoroalkyl group having 1 to 4 carbon atoms or a branched perfluoroalkyl group having 3 carbon atoms are more preferable, and perfluoroalkyl having 1 or 2 carbon atoms. A surfactant having a group or a branched perfluoroalkyl group having 3 carbon atoms is more preferable.
Examples of the above perfluoroalkyl groups include CF ₃ -*, C ₂ F ₅ -*, C ₃ F ₇ -*, nC ₄ F ₉ -*, and (CF ₃ ) ₂ CF-*. mentioned. Here, * indicates a bonding position with a carbon atom other than the carbon atom substituted with the fluorine atom. The carbon atoms bonded to these perfluoroalkyl groups preferably have hydrogen atoms or are bonded only to carbon atoms.

Commercially available fluorosurfactants having a perfluoroalkyl group having 1 to 4 carbon atoms include, for example, Ftergent (registered trademark) 100, 100C, 110, 150, 150H, 212M, 215M, 250, 251 and 222F. , 245F, 208G, FTX-218, DFX-18, 300, 310, 320, 400SW, 710FL, 683, 601AD, 602A and 681 (manufactured by Neos Co., Ltd.), and PF-136A, PF-156A , PF-151N, PF-636, PF-6320, PF-656, PF-6520 and PF-652-NF (manufactured by OMNOVA).

When the particle-containing coating layer contains a surfactant, the content of the surfactant is preferably 0.1 to 10% by mass with respect to the total mass of the particle-containing coating layer. .1 to 5% by mass is more preferable, and 0.5 to 2% by mass is even more preferable.
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, more preferably 40% by mass or more, based on the total mass of the surfactant. The upper limit is not particularly limited, and may be 100% by mass.

(binder)
The particle-containing coating layer preferably contains a binder. As the binder, a resin binder is preferred. Examples of resin binders include acrylic resins, urethane resins, polyester resins, and olefin resins.
Among them, the binder is preferably a non-polyester resin, more preferably an acrylic resin, a urethane resin, or an olefin resin. The acrylic resin, urethane resin, or olefin resin is not particularly limited, and known resins can be used.
Also, the resin binder may be an acid-modified resin.
The binder is preferably formed by applying an aqueous dispersion.
As the binder, it is preferable to use a binder that does not substantially contain a fluorine atom and a silicon atom, from the viewpoint of being superior in the effects of the present invention.

Acrylic resins are resins containing structural units derived from at least one selected from acrylates and methacrylates (hereinafter also referred to as "(meth)acrylates"), and are copolymerized with vinyl monomers such as styrene. It's okay. Although the acrylic resin is not particularly limited, it preferably contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a (meth)acrylate having an alkyl group having 1 to 8 carbon atoms. It is more preferable to contain structural units derived from.
The acrylic resin may have an acid-modified component. The acrylic resin may contain a structural unit derived from (meth)acrylic acid as an acid-modified component. In addition, (meth)acrylic acid may form an acid anhydride, or may be neutralized with at least one selected from alkali metals, organic amines and ammonia.

The acid value of the acrylic resin is preferably 30 mgKOH/g or less, more preferably 20 mgKOH/g or less. The lower limit of the acid value is not particularly limited, and is, for example, 0 mgKOH/g, but is preferably 2 mgKOH/g or more from the viewpoint of coating as an aqueous dispersion.
When an acrylic resin having a solubility parameter (SP value) different from that of the polyester resin is used, the compatibility between the acrylic resin and the polyester resin becomes insufficient, and as a result, defect suppression during long-term storage can be further improved. Such an acrylic resin, for example, to have an acid value within the above range, and to contain a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, so as to satisfy at least one of can be obtained by adjusting to When adjusted to satisfy both the acid value within the above range and the inclusion of a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, defect suppression performance in long-term storage can be further improved.

The olefin resin may be any resin containing a structural unit derived from an olefin in its main chain. Having an olefin structure in the main chain results in insufficient compatibility with the polyester resin, and as a result, it is possible to further improve defect suppression performance during long-term storage.
The olefin is not particularly limited, but is preferably an alkene having 2 to 6 carbon atoms, more preferably ethylene, propylene or hexene, and still more preferably ethylene.
The olefin-derived structural units of the polyolefin are preferably 50 to 99 mol %, more preferably 60 to 98%, of all the structural units of the polyolefin.

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

Examples of commercially available acid-modified olefin resins include Zaixen (registered trademark) series such as Zaixen AC, A, L, NC, and N (manufactured by Sumitomo Seika Co., Ltd.), Chempearl S100, S120, S200, S300, and S650. , Chemipearl (registered trademark) series such as SA100 (manufactured by Mitsui Chemicals Co., Ltd.), Hitech S3121, S3148K and other high tech (registered trademark) series (manufactured by Toho Chemical Co., Ltd.), Arrow Base SE-1013, SE-1010, Arrowbase (registered trademark) series such as SB-1200, SD-1200, SD-1200, DA-1010, DB-4010 (manufactured by Unitika Ltd.), Hardren AP-2, NZ-1004, NZ-1005 (Toyobo (manufactured by Sumitomo Seika Co., Ltd.), and Sepulsion G315 and VA407 (manufactured by Sumitomo Seika Chemicals Co., Ltd.).
Acid-modified olefin resins described in [0022] to [0034] of JP-A-2014-076632 can also be preferably used.

The urethane resin is not limited as long as it is a polymer having a urethane bond, and known urethane resins such as reaction products of polyisocyanate compounds and polyol compounds can be used.
When an aqueous dispersion containing a urethane resin is used to produce a particle-containing coating layer, the aqueous dispersion may contain a urethane resin having an acidic group (for example, a carboxyl group), or may contain a urethane resin and a dispersant. preferable. Thereby, the film formability of the particle-containing coating layer is improved.
The urethane resin has, for example, the structure of the polyol compound as the raw material, the hydrophobicity or hydrophilicity of the polyol as the raw material, the structure of the polyisocyanate compound as the raw material, and the hydrophobicity or hydrophilicity of the polyisocyanate compound as the raw material. , to obtain a desired SP value. 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. can.
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.
Commercially available urethane resins include, for example, Hydran (registered trademark) AP-20, AP-40N and AP-201 (manufactured by DIC Corporation), Takelac (registered trademark) W-605, W-5030 and W-5920. (above, manufactured by Mitsui Chemicals), Superflex (registered trademark) 210 and 130, and Elastron (registered trademark) H-3-DF, E-37 and H-15 (above, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) ).

The binder contained in the particle-containing coating layer may have a crosslinked structure. That is, the particle-containing coating layer may be a crosslinked film.
In order to form a binder having a crosslinked structure, a method of forming a particle-containing coating layer using a particle-containing coating layer-forming composition containing a cross-linking agent can be used, as described later.

The particle-containing coating layer may contain a single binder, or may contain two or more binders.
When the particle-containing coating layer contains a binder, the content of the binder is preferably 30 to 99.8% by mass, more preferably 50 to 99.5% by mass, based on the total mass of the particle-containing coating layer, from the viewpoint of suppressing defects. % is more preferred.

(other additives)
The particle-containing coating layer may contain additives other than the particles, surfactant and binder described above.
Additives contained in the particle-containing coating layer include, for example, cross-linking agents, waxes, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, antirust agents, and , antifungal agents.

The wax is not particularly limited, and may be natural wax or synthetic wax. Natural waxes include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, a slip agent described in [0087] of International Publication No. 2017/169844 can also be used.
The wax content is preferably 0 to 10% by mass with respect to the total mass of the particle-containing coating layer.

[Properties of 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 has a fluorine atom concentration of 0 to 1.0 atomic % and a silicon atom concentration of 0 to 3.0 atomic % when measured by XPS. It is characterized by
By setting the fluorine atom concentration and silicon atom concentration on the surface of the particle-containing coating layer to the above ranges, the fluorine atoms and silicon atoms in the extreme surface layer region of the particle-containing coating layer can be reduced, and the polyester film before the release layer is coated. It is thought that the ability to suppress the separation electrification suppresses the contamination of the release layer with foreign matter, thereby further improving the coatability of the release layer.

In this specification, the fluorine atom concentration and silicon atom concentration on the surface of the particle-containing coating layer are measured by XPS according to the following method. The analysis area of the particle-containing coating layer is set to 100 μm×100 μm, the surface of the particle-containing coating layer is irradiated with X-rays from a direction of 20 degrees, and the atomic concentrations of all detected atoms are measured. The atomic concentration (atomic %) of fluorine atoms is calculated from the content of fluorine atoms with respect to all detected atoms (fluorine atoms/total atoms). Similarly, the atomic concentration (atomic %) of silicon atoms is calculated from the content of silicon atoms with respect to all detected atoms (silicon atoms/total atoms). The atomic concentration is measured five times by XPS, and the calculated average values of the five atomic concentrations are taken as the fluorine atomic concentration and the silicon atomic concentration, respectively. If the concentration is below the detection limit, it is assumed to be 0 atomic %.
As described above, by performing XPS measurement under the condition of irradiating the surface of the particle-containing coating layer with X-rays from a direction of 20 degrees, the distance from the surface of the particle-containing coating layer to a distance of about 2 nm in the depth direction The content of fluorine atoms and silicon atoms in the extreme surface layer region is determined.

In the spectrum obtained by the XPS measurement, a peak derived from silica is preferably observed as the peak derived from the silicon-containing compound.

The fluorine atom concentration is preferably 0 to 0.5 atomic %, more preferably 0 to 0.1 atomic %, from the viewpoint that the effect of the present invention is more excellent.
The silicon atom concentration is preferably 0 to 2.5 atomic %, more preferably 0 to 0.1 atomic %, from the viewpoint that the effect of the present invention is more excellent.

The fluorine atom concentration and silicon atom concentration on the surface of the particle-containing coating layer can be adjusted by adjusting the types and blending amounts of binders, surfactants and/or cross-linking agents to be described later used for preparing the particle-containing coating layer. Specifically, by reducing the use of raw materials containing fluorine atoms and/or silicon atoms as binders, surfactants, and/or cross-linking agents described later, the fluorine atom concentration and silicon atom concentration are within the above ranges. can be adjusted to be included.

(Content of dimethylsiloxane)
The total secondary ion intensity (T The ratio (P / T) of the secondary ion intensity (P) of the highest fragment peak derived from dimethylsiloxane to ) is preferably less than 0.01, preferably less than 0.001 more preferred. When the above ratio (P/T) on the surface of the particle-containing coating layer is within the above range, the amount of components containing dimethylsiloxane such as silicone compounds on the surface of the particle-containing coating layer is small, so that the effects of the present invention are more excellent. A polyester film is obtained. Fragments derived from dimethylsiloxane include, but are not limited to, SiC ₃ H ₉ ⁺ , Si ₂ C ₅ H ₁₅ O ⁺ , and Si ₃ C ₅ H ₁₅ O ₃ ⁺ ; The secondary ion intensity of the fragment peak having the highest secondary ion intensity among the fragment peaks derived from the compound having the compound is adopted as the secondary ion intensity (P).
The details of the method for analyzing the surface of the particle-containing coating layer by TOF-SIMS will be described in Examples below.

(thickness)
The thickness of the particle-containing coating layer is not particularly limited, but is preferably 1 nm to 3 μm. ~150 nm is particularly preferred.
The thickness of the particle-containing coating layer is determined by preparing a section having a cross section perpendicular to the main surface of the release film, and examining it with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Arithmetic mean value of five thicknesses of the above section measured using

(Surface free energy)
The surface free energy on the surface of the particle-containing coating layer is preferably 25-65 mJ/m ² , more preferably 25-50 mJ/m ² , still more preferably 25-45 mJ/m ² , and particularly preferably 30-45 mJ/m ² . .
When the surface free energy on the surface of the particle-containing coating layer is within the above range, impurities such as oligomers contained in the polyester base material will not precipitate on the particle-containing coating layer (particularly after long-term storage of the polyester film or release film). ) can be suppressed, and defects in the ceramic green sheet can be suppressed.
The oligomer is a low-molecular-weight by-product produced during the polymerization of polyester, and is a component contained as an impurity in the polyester base material.

The surface free energy on the surface of the particle-containing coating layer was measured using a contact angle meter (for example, "DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.) at 25 ° C. on the peeling surface with purified water and methylene iodide. And ethylene glycol droplets are dropped, the contact angle is measured 1 second after the droplets adhere to the surface, and the obtained contact angle is calculated according to the method of Kitazaki and Hata.
The "surface free energy" obtained by the above method is the sum of the polar and hydrogen bonding components of the surface free energy.

(Maximum protrusion height Sp, surface average roughness Sa)
It is preferable that the particles contained in the particle-containing coating layer form projections (projections) on the surface of the particle-containing coating layer.
The maximum protrusion height Sp on the surface of the particle-containing coating layer is preferably 600 nm or less in order to further suppress defects in the ceramic green sheet during the production of the ceramic green sheet. 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. Although the lower limit of the maximum protrusion height Sp is not particularly limited, it is preferably 10 nm or more.
The average surface roughness Sa of the surface of the particle-containing coating layer is preferably 0 to 10 nm, more preferably 0 to 5 nm.

The maximum protrusion height Sp and surface average roughness Sa of the surface of the particle-containing coating layer were measured using an optical interferometer ("Vertscan 3300G Lite" manufactured by Hitachi High-Tech Co., Ltd.) as follows. It is obtained by measuring under the conditions and then analyzing with the built-in data analysis software.
In the measurement of the maximum protrusion height Sp, the measurement position is changed and measured five times, and the maximum value of the obtained measurement values is taken as the measurement value of the maximum protrusion height Sp (in the built-in data analysis software, it is written as P ). In addition, in the measurement of the surface average roughness Sa, the measurement position is changed and the measurement is performed five times, and the average value of the obtained measurement values is used as the measurement value of the surface average roughness Sa. Specific measurement conditions are as follows.
Measurement mode: WAVE mode Objective lens: 50x Measurement area: 186 μm × 155 μm

<Particle-free layer>
The polyester film may have a particle-free layer containing no particles on the surface of the polyester substrate opposite the particle-containing coating layer.
The particle-free layer can be the same as the particle-containing coating layer, including preferred embodiments thereof, except that it does not contain particles. Particle-free layers include, for example, non-polyester resin layers and antistatic layers. 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, more preferably the hydrocarbon surfactant. The antistatic layer is not particularly limited as long as it contains an antistatic agent as an additive. A known antistatic agent can be used in the antistatic layer. More preferably, the antistatic layer is a non-polyester resin layer.

<Properties of polyester film>
[Amount of peeling charge]
The polyester film was measured by the following measurement method in an environment of a temperature of 23 ° C. and a relative humidity (RH) of 20%. The absolute value of the peel charge amount of the surface) is preferably 0 to 0.12 nC (nanocoulomb), more preferably 0 to 0.11 nC, even more preferably 0 to 0.1 nC. Here, the unit nC (nanocoulomb) is 10 ⁻⁹ coulomb.
When the total value of the peel charge amount is within the above range, the effects of the present invention are more excellent, and the peel layer coatability is improved.

The method for measuring the amount of peeling charge on both sides of the polyester film is as follows.
As a measurement device, a stand for placing a reference sample of polyester film (the peeling layer forming surface is the upper surface) and a measurement sample of polyester film (the surface of the particle-containing coating layer is the lower surface) are held along the vertical direction. A head capable of repeatedly pressing and peeling the lower surface of the measurement sample against the upper surface of the reference sample by ascending and descending, and an electrometer connected to the head and capable of measuring the charge amount of the measurement sample. use the device.
More specifically, a polyester film was cut into a circle with a diameter of 1.5 cm to prepare a measurement sample for measuring the peel charge amount, and a rectangle of 13 cm × 4 cm was cut to measure the peel charge amount. Prepare a reference sample for measurement. Next, the obtained polyester film sample is allowed to stand in an environment of the above measured temperature and humidity for 2 hours or longer. After that, the reference sample is placed on the table of the measurement device, and the measurement sample is attached to the head. At this time, the peeling layer forming surface of the reference sample placed on the stand faces the upper side so that the peeling layer forming surface of the reference sample and the surface of the particle-containing coating layer of the measurement sample face each other. The surface of the particle-containing coating layer is placed on the bottom side, respectively.
After neutralizing the measurement sample, the head is lifted or lowered to repeatedly press and peel the reference film against the measurement sample (contact pressure: 566 g/cm ² , contact time: 2 seconds). Using the same measurement sample, the charge amount of the measurement sample is measured after each of the first to fifth peelings, and the average value of the measured values is calculated. While changing the measurement sample, the contact position of the measurement sample on the reference sample is changed for each measurement sample, measurement is performed with a total of four measurement samples, and the peel charge amount is obtained by averaging all of them. The measurement is performed in an environment with a temperature of 23° C. and a relative humidity (RH) of 20%.
Regarding the method for measuring the peeling charge amount of the polyester film, the contents described in JP-A-2003-194865 (especially [0053] to [0067]) can also be referred to, and the contents described in the above publications are incorporated herein. .

The amount of peeling charge can be adjusted by selecting the polyester base material and the types and amounts of components such as binders and surfactants contained in the particle-containing coating layer. More specifically, for two selected from the group consisting of a polyester base material, a binder and a surfactant, by selecting materials closer in the electrification series, the peel electrification amount can be adjusted within the above range.

[Thermal shrinkage]
The polyester film preferably has a heat shrinkage rate in the transport direction measured in an environment at a temperature of 150 ° C. of 0 to 3.0%, more preferably 0 to 2.0%, and 0 to 1 0.5% is more preferred. In addition, the polyester film preferably has a widthwise heat shrinkage of 0 to 2.0%, more preferably 0 to 1.5%, as measured in an environment at a temperature of 150°C. More preferably ~1.0%.
When the heat shrinkage 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 the release layer, and the ceramic green sheet after peeling from the release film, are laminated. Since the dimensional stability is good when it is pressed, the failure of the electronic member is less likely to occur.
The method for measuring each of the above thermal contraction rates will be described in the examples below.

The heat shrinkage rate of the polyester film can be adjusted by selecting heating or cooling conditions when producing the polyester film. More specifically, it can be adjusted by changing at least one of the conditions of the heat setting process, the heat relaxation process, and the cooling process, which will be described later.

<Method for producing polyester film>
A method for producing a polyester film will be described.
The method for producing the polyester film is not particularly limited as long as the polyester film having the properties described above can be obtained, and known methods can be used.
Among them, in terms of being able to produce a polyester film having the above-described properties with good productivity, the method for producing a polyester film includes:
An extrusion molding step of forming an unstretched polyester base material by extrusion;
A first stretching step of stretching an unstretched polyester substrate in one of the transport direction and the width direction to form a uniaxially oriented polyester substrate, and a uniaxially oriented polyester substrate in the transport direction and a stretching step in which a second stretching step of stretching in the other width direction to form a biaxially oriented polyester substrate is performed stepwise or simultaneously,
Between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, the particle-containing coating layer-forming composition is applied to one surface side of the polyester substrate. and a particle-containing coating layer forming step of forming a particle-containing coating layer.
Hereinafter, embodiments of the preferred manufacturing method will be described in detail.

[Extrusion process]
The extrusion molding step is a step of forming an unstretched polyester base material by extrusion molding. More specifically, it is a step of extruding a molten resin containing a raw material polyester resin into a film to form an unstretched polyester base material. The polyester resin as a raw material is synonymous with the polyester resin described in the item of the polyester resin above.
In addition, in order to produce a polyester base material that does not substantially contain particles, it is preferable to use polyester pellets that do not contain particles at the time of extrusion molding.

The extrusion molding method is, for example, a method of molding a raw material resin into a desired shape by extruding a melt of the raw material resin using an extruder.
The melt extruded from the extrusion die is cooled to form a film. For example, the melt can be formed into a film by contacting the melt with a casting roll and cooling and solidifying the melt on the casting roll. In cooling the melt, it is preferable to blow air (preferably cool air) to the melt.

[Stretching process]
The stretching step includes a first stretching step of stretching an unstretched polyester substrate in either the transport direction or the width direction to form a uniaxially oriented polyester substrate, and a uniaxially oriented polyester substrate. in the other of the machine direction and the width direction to form a biaxially oriented polyester base material.
One of the first stretching step and the second stretching step is a longitudinal stretching step of stretching the polyester base material in the conveying direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first stretching step and the second stretching step. is a lateral stretching step of stretching the polyester base material in the width direction (hereinafter also referred to as “lateral stretching”). During stretching, the polyester polymer is aligned in each direction.

The stretching step may be simultaneous biaxial stretching in which longitudinal stretching and lateral stretching are performed simultaneously, or sequential biaxial stretching in which longitudinal stretching and lateral stretching are performed in stages. Examples of the form of sequential biaxial stretching include longitudinal stretching→lateral stretching, longitudinal stretching→lateral stretching→longitudinal stretching, and longitudinal stretching→longitudinal stretching→lateral stretching, with longitudinal stretching→lateral stretching being preferred.
Hereinafter, the mode of longitudinal stretching→transverse stretching will be described, but the production method is not limited to this mode.

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

In the lateral stretching step, it is preferable to preheat the uniaxially oriented polyester base material before lateral stretching. By preheating the uniaxially oriented polyester base material, the uniaxially oriented polyester base material can be easily laterally stretched.
The draw ratio in the width direction of the uniaxially oriented polyester substrate (lateral draw ratio) in the transverse drawing step is not particularly limited, but is preferably larger than the draw ratio in the longitudinal drawing step. The draw ratio in the transverse drawing step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, even more preferably 3.5 to 4.5 times.
The stretching speed in the lateral stretching step is preferably 8 to 45%/second, more preferably 10 to 30%/second, even more preferably 15 to 20%/second.

[Particle-containing coating layer forming step]
The particle-containing coating layer forming step is a step of forming a particle-containing coating layer by applying a particle-containing coating layer-forming composition to one surface of the polyester substrate.
The particle-containing coating layer forming step is performed between the extrusion molding step and the first stretching step, between the first stretching step and the second stretching step, or after the stretching step.
The particle-containing coating layer formed on one surface of the polyester base material in the particle-containing coating layer forming step is synonymous with the layer described in the item of the particle-containing coating layer.
Hereinafter, the mode of applying the particle-containing coating layer-forming composition will be described.

First, the particle-containing coating layer-forming composition will be described.
The composition for forming a particle-containing coating layer can be prepared by mixing the particles contained in the particle-containing coating layer, an optional binder, an optional additive, and a solvent. .
Solvents include, for example, water and alcohol solvents.

The particle-containing coating layer-forming composition may contain a single solvent, or may contain two or more solvents.
The content of the solvent is preferably 80 to 99.5% by mass, more preferably 90 to 99% by mass, based on the total mass of the particle-containing coating layer-forming composition.
That is, in the particle-containing coating layer-forming composition, the total content of components (solid content) other than the solvent is preferably 0.5 to 20% by mass with respect to the total mass of the particle-containing coating layer-forming composition. , 1 to 10 mass % is more preferred.

The particles contained in the composition for forming a particle-containing coating layer, the optionally added binder, and the optionally added additive, including their preferred embodiments, are described in the above particle-containing coating layer. It is as described in the item.
Among them, the composition for forming a particle-containing coating layer preferably contains particles and a hydrocarbon surfactant in terms of excellent suitability for producing the polyester film of the present invention. It is more preferable to contain a binder.
Regarding each component other than the solvent in the composition for forming a particle-containing coating layer, the content of each component relative to the total mass of the solid content of the composition for forming a particle-containing coating layer is It is preferable to adjust the content of each component in the particle-containing coating layer-forming composition so as to be the same as the preferred content of the component.

Moreover, the composition for forming a particle-containing coating layer may contain a cross-linking agent.
The cross-linking agent is not particularly limited, and known ones can be used.
Examples of cross-linking agents include melamine-based compounds, oxazoline-based compounds, epoxy-based compounds, isocyanate-based compounds, and carbodiimide-based compounds, with oxazoline-based compounds and carbodiimide-based compounds being preferred. Examples of commercially available products include Carbodilite V-02-L2 (manufactured by Nisshinbo Corp.) and Epocross K-2020E (manufactured by Nippon Shokubai Co., Ltd.). For details of the epoxy-based compound, the isocyanate-based compound, and the melamine-based compound, reference can be made to [0081] to [0083] of JP-A-2015-163457. The cross-linking agents described in [0082] to [0084] of WO2017/169844 can also be preferably used. As for the carbodiimide compound, the descriptions in [0038] to [0040] of JP-A-2017-087421 can be referred to.
For oxazoline-based compounds, carbodiimide-based compounds, and isocyanate-based compounds, cross-linking agents described in [0074] to [0075] of WO 2018/034294 can also be preferably used.
The content of the cross-linking agent is preferably 0 to 50% by mass with respect to the total mass of the particle-containing coating layer.
The mass ratio of the crosslinking agent to the binder in the particle-containing coating layer-forming composition is preferably 2 to 50% by mass.

The coating method of the particle-containing coating layer-forming composition is not particularly limited, and known methods can be used. Examples of coating methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating and dip coating.
A method for drying the particle-containing coating layer-forming composition is not particularly limited, and a known method can be used. For example, drying by heating in a high-temperature atmosphere drying furnace, a method of blowing hot air from a nozzle (for example, the method described in JP-A-2018-155482 and JP-A-2003-106767), a method of heating with an infrared heater (for example, , JP-A-2014-129909, and the method described in JP-A-2013-062066), a method of drying by heat transfer heating with an induction heating conveying roller, and a drying method by reduced pressure.

The particle-containing coating layer forming 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.

In addition, in order to improve the adhesion between the polyester base material and the particle-containing coating layer, before providing the particle-containing coating layer, the release layer forming surface of the polyester base material is subjected to anchor coating, corona treatment, and plasma treatment. Pretreatment such as treatment may be performed.

[Heat setting process]
The method for producing a polyester film may have a heat setting step as a heat treatment for the polyester film obtained in the stretching step after the stretching step.
In the heat-setting step, the polyester film obtained by the stretching step can be heated and heat-set. By crystallizing the polyester resin by heat setting, shrinkage of the polyester base material can be suppressed.
The surface temperature (heat setting temperature) of the polyester film in the heat setting step 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. Although the lower limit is not particularly limited, it 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 step is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, even more preferably 5 to 10 seconds.

[Thermal relaxation step]
The method for producing a polyester film may have a heat relaxation step after the heat setting step.
In the thermal relaxation step, it is preferable to thermally relax the polyester film heat-set in the heat-setting step by heating at a temperature lower than that in the heat-setting step. Thermal relaxation can relax the residual strain of the polyester film.
The surface temperature (thermal relaxation temperature) of the polyester film in the heat relaxation step is preferably 5°C or more lower than the heat setting temperature, more preferably 15°C or more lower, still more preferably 25°C or more lower, and 30°C or higher. Low temperatures are particularly preferred. That is, the thermal relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, still 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.

[Cooling process]
The method of manufacturing the polyester film may comprise a cooling step of cooling the heat-relaxed polyester film.
In the above production 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 2000 to 3500° C./min, more than 2200° C./min and less than 3000° C./min. Preferably, 2300-2800° C./min is particularly preferred.
In order to reduce heat shrinkage and impart dimensional stability, the cooling rate of the polyester film in the cooling step is preferably more than 500 ° C./min and less than 4000 ° C./min, more preferably 700 to 3000 ° C./min, and 1000 ° C. /min and less than 2500°C/min is more preferable. Within the above range, streak-like wrinkles occurring on the surface of the release layer of the release film can be easily suppressed, and a ceramic green sheet with suppressed thickness unevenness can be produced.
The cooling step preferably includes a step (expansion step) of expanding the thermally relaxed polyester film in the width direction.
The expansion rate of the polyester film in the width direction by the expansion step, 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, and more preferably 0.001% or more. Preferably, 0.01% or more is more preferable.
Although the upper limit of the expansion rate is not particularly limited, it is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

In the manufacturing method described above, the method of forming the particle-containing coating layer by applying the particle-containing coating layer-forming composition in the particle-containing coating layer forming step was described. is not limited to, and a known method can be used.

[Winding process]
The production method may have a winding step of obtaining a roll-shaped polyester film by winding the polyester film obtained through the above steps.

[Trimming process]
The manufacturing method further comprises a trimming step of cutting at least one end in the width direction of the polyester film by continuously cutting the polyester film along the transport direction before performing the winding step. good too.

[Particle-free layer forming step]
A polyester film having a particle-free layer can be obtained, for example, by applying a particle-free layer-forming composition to the surface of the polyester substrate opposite to the surface on which the particle-containing coating layer is to be formed, in the above polyester film production method. It can be manufactured by carrying out a particle-free layer forming step of forming a particle-free layer.
The particle-free layer forming step is the same as the particle-containing coating layer forming step described above, including preferred embodiments thereof, except that the particle-free layer-forming composition is used in place of the particle-containing coating layer-forming composition. It can be. The composition for forming a particle-free layer may be the same as the composition for forming a particle-containing coating layer described above, including its preferred embodiments, except that it does not contain particles, and the composition and/or properties thereof may be changed as appropriate. By doing so, the desired particle-free layer can be formed.

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

In the manufacturing method specifically described above, a combination of two or more preferred aspects is a more preferred aspect.

[Release film]
The release film of the present invention comprises the above polyester film and a release layer laminated on the surface of the polyester film opposite to the particle-containing coating layer (release layer forming surface).
The release film can be produced, 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 base material, or may be provided on the polyester base material via another layer.
The release layer is preferably provided directly on the surface of the polyester base material in terms of better smoothness. Also preferred is a mode in which a release layer is laminated on a polyester substrate via a non-polyester resin layer or an antistatic layer. By laminating the release layer on the polyester substrate via the non-polyester resin layer, precipitation of the oligomer from the polyester substrate can be suppressed, and the smoothness of the release layer can be further improved. In addition, by laminating the release layer on the polyester substrate with the antistatic layer interposed therebetween, the separation electrification after the surface of the particle-containing layer and the release layer formation surface are in contact with each other is suppressed, and the composition for forming the release layer is It is possible to suppress electrification of the entire release film when applying a substance, and further suppress contamination of the release layer with foreign matter.

A functional layer such as a ceramic green sheet is releasably formed on the surface of the release layer of the release film opposite to the polyester substrate (hereinafter also referred to as "release surface").
The release film is preferably for ceramic green sheet production. In other words, it is preferable that the ceramic green sheet is detachably formed on the release surface of the release film.
The release film will be described below using a release film for producing a ceramic green sheet as an example, but the application of the release film of the present invention is not limited to the production of a ceramic green sheet.

<Release layer>
The composition of the release layer is not particularly limited as long as the ceramic green sheet can be manufactured to be peelable as described above, but the release layer preferably contains a release agent.
The release agent is preferably resin. The resin contained in the release layer as a release agent is not particularly limited, but examples thereof include silicone resins, fluororesins, alkyd resins, acrylic resins, various waxes, and aliphatic olefins. Therefore, silicone resins are preferred.

A silicone resin means a resin having a silicone structure in its molecule. Examples of silicone resins include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified silicone resins, with reactive curable silicone resins being preferred.
Examples of reactive curable silicone resins include addition reaction silicone resins, condensation reaction silicone resins, and ultraviolet or electron beam curable silicone resins.

Examples of addition reaction silicone resins include resins obtained by reacting and curing polydimethylsiloxane having a terminal or side chain introduced with a vinyl group and hydrogen siloxane using a platinum catalyst.
As the condensation reaction silicone resin, for example, a three-dimensional polydimethylsiloxane having terminal OH groups and a polydimethylsiloxane having terminal H groups are subjected to a condensation reaction using an organotin catalyst. Examples thereof include resins having a crosslinked structure.
Examples of UV-curing silicone resins include those that use the same radical reaction as silicone rubber cross-linking, those that introduce photo-curing by introducing unsaturated groups, those that generate strong acids by decomposing onium salts with ultraviolet rays or electron beams, and epoxy resins. Those that crosslink by cleaving the groups and those that crosslink by the addition reaction of thiol to vinyl siloxane are included. More specific examples include acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane.

The resin contained as the release agent preferably has a crosslinked structure. In other words, the release layer is preferably a crosslinked film. A release layer containing a resin having a cross-linked structure as a release agent can be formed by using a release layer-forming composition containing a cross-linking agent, as described later.

The release layer may contain a resin other than the release agent (hereinafter also referred to as "another resin") in addition to the resin as the release agent.
Known resins can be used as other resins, and examples thereof include ultraviolet curable resins and thermosetting resins. More specifically, acrylic resins, unsaturated polyester resins, melamine resins, epoxy resins, phenol resins, and urethane resins can be used. The release layer-forming composition, which will be described later, may contain another resin and a polymerization initiator and/or catalyst, and the release layer may contain a residue of the polymerization initiator and/or catalyst. .

The release layer may contain additives in addition to the resin as the release agent and other resins. Additives include light and heavy release additives to adjust release force, adhesion improvers, and antistatic agents.

One type of resin may be used as the release agent contained in the release layer, or two or more types may be used.
The content of the resin as the release agent in the release layer is preferably 0.1 to 99.9% by mass, more preferably 0.5 to 98% by mass, based on the total mass of the release layer.
When the release layer contains the other resin, the content of the other resin is preferably 0 to 98% by mass, more preferably 1 to 95% by mass, based on the total mass of the release layer. The remainder other than the resin as a release agent in the release layer and other resins is the above additives and/or the solvent and polymerization initiator contained in the release layer forming composition (described later) used to form the release layer. , and residues such as catalysts.

<Properties of release film>
[Thickness of release layer]
The thickness of the release layer is preferably from 10 to 1000 nm, more preferably from 30 to 700 nm, in terms of excellent balance between release performance and smoothness of the release layer surface.
The thickness of the release layer is measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) by preparing a section having a cross section perpendicular to the main surface of the release film. Arithmetic mean value of the thickness at each point.

[Surface free energy of peeled surface]
The surface free energy of the release surface of the release film is preferably 5-50 mJ/m ² , more preferably 10-35 mJ/m ² .
When the surface free energy of the release surface is within the above range, the ceramic green sheet formed on the release surface is more easily separated, and the ceramic slurry can be applied more smoothly when producing the ceramic green sheet.
The surface free energy of the release surface can be adjusted by the type of resin forming the release layer and additives.
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 surface of the particle-containing coating layer described above.

[Maximum protrusion height Sp of peeled surface, surface average roughness Sa]
The release surface is preferably as smooth as possible in order to make the ceramic green sheet formed on the release surface smoother. Specifically, the maximum protrusion height Sp of the peeled surface is preferably 1 to 60 nm, more preferably 1 to 40 nm, and even more preferably 1 to 30 nm.
The surface average 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 surface average roughness Sa of the release surface can be adjusted by not including particles in the release layer when providing the release layer, and by selecting the resin and additives forming the release layer.
The method for measuring the maximum projection height Sp and the average surface roughness Sa of the peeled surface is the same as the method for measuring the maximum projection height Sp and the average surface roughness Sa of the surface of the particle-containing coating layer described above.

[Thickness of 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 better releasability. Moreover, the thickness of the release film is preferably 3 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more, in order to improve strength and workability.

<Manufacturing method of release film>
The method for producing the release film of the present invention is not particularly limited as long as it is a method of forming a release layer on the surface of the polyester film on the polyester substrate side. A step of forming a release layer (release layer forming step) is performed by applying a release layer forming composition to the surface, drying the coating film to remove the solvent, and optionally heating or irradiating with light. method.

The release layer forming step can be carried out, for example, on a polyester film produced by the polyester film production method described above.
The release layer formed on one surface of the polyester substrate in the release layer forming step has the same meaning as the layer described in the above item of the release layer.

The release layer forming composition used in the release layer forming step will be described.
The composition for forming a release layer can be prepared by mixing a release agent, additives added as necessary, and a solvent.
Examples of solvents include water, alcohol solvents, ether solvents, ketone solvents, and aromatic hydrocarbon solvents.

The release layer-forming composition may contain a single solvent, or may contain two or more solvents.
The content of the solvent is preferably 80 to 99.5% by mass, more preferably 90 to 99% by mass, based on the total mass of the release layer-forming composition.
That is, in the release layer-forming composition, the total content of components (solid content) other than the solvent is preferably 0.5 to 20% by mass, preferably 1 to 10% by mass, based on the total mass of the release layer-forming composition. % by mass is more preferred.

The release agent contained in the release layer-forming composition and additives added as necessary are as described in the above release layer section, including their preferred embodiments.
The release layer-forming composition contains the above resin and solvent, and if necessary, may contain the above additives and/or the above catalyst used for curing the resin.
In addition, the composition for forming a release layer may contain a cross-linking agent. The cross-linking agent is not particularly limited, and known ones can be used.
The release layer-forming composition may also contain a polymerization initiator. Examples of the polymerization initiator include photopolymerization initiators, and known ones can be used.
For each component other than the solvent in the release layer-forming composition, the content of each component relative to the total mass of solids in the release layer-forming composition is the preferred content of each component relative to the total mass of the release layer. It is preferable to adjust the content of each component in the release layer-forming composition so as to be the same.

The method of applying the release layer-forming composition is not particularly limited, and known methods can be used. Specific examples of the coating method include the coating method mentioned in the particle-containing coating layer forming step in the method for producing a polyester film.
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.

In addition, in order to improve the adhesion between the polyester base material and the release layer, the surface of the polyester base material is subjected to pretreatment such as anchor coating, corona treatment, and plasma treatment before providing the release layer. may

<Application of release film>
Since the release film can suppress defects in the ceramic green sheet formed on the release surface, it is preferably used as a release film (carrier film) for producing a ceramic green sheet for a ceramic capacitor.
A method for manufacturing a ceramic green sheet using the release film is not particularly limited, and a known method can be used. As a method for producing a ceramic green sheet, for example, a prepared ceramic slurry is applied to the release surface of the release film, and the solvent contained in the ceramic slurry is removed by drying, thereby forming a ceramic green sheet on the release surface. are mentioned.
The method of applying the ceramic slurry is not particularly limited. For example, a known method such as applying a ceramic slurry obtained by dispersing ceramic powder and a binder in a solvent by a reverse roll method and removing the solvent by heating and drying. method can be applied. The binder agent is not particularly limited, and examples thereof include polyvinyl butyral. Also, the solvent is not particularly limited, and examples thereof include ethanol and toluene.

The ceramic green sheets thus produced are used to produce ceramic capacitors. As a method of manufacturing a ceramic capacitor using a ceramic green sheet, a known method can be applied, and examples thereof include the following methods.
First, internal electrodes are provided on the laminate of the release film and the ceramic green sheets produced by the above method by applying or printing a conductive paste. Next, the release film is removed from the laminate of ceramic green sheets, the ceramic green sheets with internal electrodes are sequentially laminated, and the resulting laminate is pressed to produce an intermediate laminate. After cutting the intermediate laminate into a desired shape, the cut intermediate laminate is fired to obtain a ceramic body. Next, a ceramic capacitor is obtained by forming external electrodes electrically connected to the internal electrodes on the two end surfaces of the fired intermediate laminate using a conductive paste such as silver.

In addition, the release film of the present invention includes a protective film for dry film resist, a film for sheet molding such as a decorative layer and a resin sheet, a release film for process manufacturing such as a semiconductor manufacturing process, and a release film for a polarizing plate manufacturing process. , and can also be used as a separator for pressure-sensitive adhesive films for labels, medical and office supplies.

EXAMPLES The present disclosure will be described more specifically with reference to examples below. Materials, usage amounts, proportions, processing details, and processing procedures shown in the following examples can be changed as appropriate without departing from the scope of the present disclosure. Accordingly, the scope of the present disclosure is not limited to the specific examples provided below. "Parts" and "%" are based on mass unless otherwise specified.

〔raw materials〕
Raw materials used for forming the particle-containing coating layer are shown below.

(resin)
Acrylic resin 1: 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 Acrylic resin 2: methyl methacrylate , stearyl methacrylate, 2-hydroxyethyl methacrylate and methacrylic acid at a mass ratio of 47:26:20:7 Olefin resin: Zaixen (registered trademark) NC (manufactured by Sumitomo Seika Co., Ltd., acid-modified polyolefin)
Urethane resin 1: ADEKA BONDITTER (registered trademark) HUX-370 (manufactured by ADEKA Corporation, polyurethane)
Urethane resin 2: Hydran (registered trademark) AP-40N (manufactured by DIC Corporation, polyurethane)

(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)

(particle)
Particle 1: Snowtex (registered trademark) MP-2040 (manufactured by Nissan Chemical Co., Ltd., colloidal silica, average particle size 200 nm)
Particle 2: Snowtex (registered trademark) ZL (manufactured by Nissan Chemical Industries, Ltd., colloidal silica, average particle size 80 nm)
Particle 3: Eposter (registered trademark) MX050W (manufactured by Nippon Shokubai Co., Ltd., crosslinked PMMA particles, average particle size 70 nm)
Particle 4: Nipol (registered trademark) UFN1008 (manufactured by Nippon Zeon Co., Ltd., non-crosslinked styrene resin particles (styrene copolymer), average particle size 1.9 μm)

(Surfactant)
W-1: nonionic hydrocarbon surfactant (Naroacty (registered trademark) CL95, manufactured by Sanyo Chemical Industries, Ltd.)
W-2: Anionic hydrocarbon surfactant (Rapisol (registered trademark) A-90, manufactured by NOF Corporation)
W-3: Fluorine-based surfactant (Surflon (registered trademark) S-211, manufactured by AGC Seimi Chemical Co., Ltd., structure containing a linear perfluoroalkyl group having 6 or more carbon atoms)
W-4: Silicone surfactant (BYK-346, manufactured by BYK)
W-5: Fluorine-based surfactant (Ftergent (registered trademark) 215M, manufactured by Neos Co., Ltd., structure containing a perfluoroisopropyl group and not containing a linear perfluoroalkyl group having 6 or more carbon atoms)

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

[Longitudinal stretching process]
The unstretched polyester base material was subjected to a longitudinal stretching step by the following method.
A preheated unstretched polyester substrate is passed between two pairs of rolls having different peripheral speeds under the following conditions and stretched in the machine direction (conveyance direction) to form a uniaxially oriented polyester substrate. made.
(Longitudinal stretching conditions)
Preheating temperature: 75°C
Stretching temperature: 90°C
Stretch ratio: 3.4 times Stretching speed: 1300%/sec

[Particle-containing coating layer forming step]
On one side of the longitudinally stretched uniaxially oriented polyester substrate, the following composition A1 (particle-containing coating layer forming composition) was applied with a bar coater, and the formed coating film was dried with hot air at 100°C. to form a particle-containing coating layer. That is, composition A1 was in-line coated onto a uniaxially oriented polyester substrate. At this time, the coating amount of composition A1 was adjusted so that the thickness of the particle-containing coating layer formed after lateral stretching was 100 nm.

(Composition A1)
Composition A1 was prepared by mixing each component shown below. The prepared composition A1 was subjected to filtration treatment using a filter with a pore size of 6 μm (F20, manufactured by Mahle Filter Systems Co., Ltd.), and membrane degassing (2x6 radial flow superphobic, manufactured by Polypore Co., Ltd.). was carried out to obtain composition A1.
・ Acrylic resin 1 (aqueous dispersion of copolymer obtained by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate and acrylic acid at a mass ratio of 59: 8: 26: 5: 2, solid component concentration 25% by mass, acid value 16 mgKOH/g) 167 parts by mass Crosslinking agent 1 (carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Co., Ltd., solid concentration 10% by mass dilution) 16.8 parts by mass・ Surfactant W-2 (Rapisol (registered trademark) A-90, di-2-ethylhexyl sodium sulfosuccinate, manufactured by NOF Corporation, solid content concentration 1% by mass water dilution) 56 parts by mass Particle 1 (Snow Tex (registered trademark) MP-2040, manufactured by Nissan Chemical Co., Ltd., colloidal silica, average particle diameter 200 nm, solid content concentration 40% by mass aqueous dispersion) 11 parts by mass, water 776 parts by mass

[Lateral stretching process]
A biaxially oriented polyester base material was produced by stretching the polyester base material, which had undergone the longitudinal stretching step and the particle-containing coating layer forming step, in the width direction using a tenter under the following conditions.
(Lateral stretching conditions)
Preheating temperature: 100°C
Stretching temperature: 120°C
Stretch ratio: 4.2 times Stretching speed: 50%/sec

[Heat setting process]
The polyester film obtained by the lateral stretching step was heated using a tenter under the following conditions to perform a heat setting step of heat setting the polyester film.
(Heat fixation conditions)
Heat setting temperature: 227°C
Heat fixation time: 6 seconds

[Thermal relaxation step]
Then, the heat-set polyester film was heated under the following conditions to perform a thermal relaxation step for relaxing the tension of the polyester film. Also, in the heat relaxation step, the film width was reduced compared to the time when the heat setting step was completed by narrowing the distance (tenter width) between the gripping members of the tenter that grips both ends of the polyester film. The following thermal relaxation rate Lr was obtained from the film width L2 at the end of the thermal relaxation process with respect to the film width L1 at the start of the thermal relaxation process by the formula Lr=(L1−L2)/L1×100.
(Thermal relaxation conditions)
Thermal relaxation temperature: 190°C
Thermal relaxation rate Lr: 4%

[Cooling process]
A cooling step was performed on the thermally relaxed polyester film under the following conditions.
The following cooling rate is the cooling time ta, which is the residence time from when the polyester film is carried into the cooling unit of the stretching machine until it is carried out. It was obtained by dividing the temperature difference ΔT (°C) from the measured film surface temperature by the cooling time ta.
(Cooling condition)
Cooling rate: 2500°C/min

[Winding process]
With respect to the polyester film cooled in the cooling step, the trimming device is used to continuously cut the polyester film along the conveying direction at a position of 20 cm from both ends in the width direction of the film, and trim both ends of the film. bottom. Then, an area extending from both ends of the trimmed polyester film to 10 mm in the width direction was subjected to extrusion processing (knurling), and then the polyester film was wound up at a tension of 40 kg/m.
A biaxially stretched film (polyester film of Example 1) was produced by the above method. The obtained biaxially stretched film had a thickness of 31 μm, a width of 1.5 m, and a winding length of 7000 m.

[Peeling layer forming step]
The obtained biaxially stretched film was unwound at a transport speed of 30 m/min, and the surface of the biaxially stretched film opposite to the particle-containing coating layer (the surface without the particle-containing coating layer) was coated with the following formulation B. After applying the coating liquid by a slot die method, the coating film is dried using a hot air dryer at 120°C and wound up to prepare a roll-shaped release film (a biaxially oriented film provided with a release layer). bottom. The thickness of the release layer after drying was 0.5 μm, the surface free energy of the release surface was 15 mJ/m ² , and the surface average roughness Sa was 2 nm.

(Prescription B: Coating liquid for forming release layer)
・Addition reaction type silicone compound (manufactured by Dow Corning Toray 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 (SRX-212, manufactured by Dow Corning Toray Co., Ltd.): 0.1 part A coating solution for forming a release layer was prepared by stirring and mixing the above components.

[Examples 2 to 16, Comparative Examples 1 to 2]
As shown in Table 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, the same method as in Example 1 was performed. Polyester films (biaxially stretched films) of Examples 2 to 16 and Comparative Examples 1 and 2 were produced, and a release layer was provided on the surface of the produced biaxially stretched film to produce a release film.
In Example 7, a polyester film was produced in the same manner as in Example 6, except that the amount of surfactant was doubled. Further, in Example 10, 5 parts by mass of a fluorosurfactant (Futergent 215M, manufactured by Neos Co., Ltd., solid content 1% by mass diluted with water) was further added to the particle-containing coating layer-forming composition. A polyester film was produced in the same manner as in Example 9 except for the above. In Example 11, 0.7 parts by mass of a nonionic surfactant (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd., solid content 100% by mass) was further added to the particle-containing coating layer forming composition. A polyester film was produced in the same manner as in Example 1, except that
In the release films of Examples 2 to 16, as in Example 1, the thickness of the release layer after drying was 0.5 μm, the surface free energy of the release layer surface was 15 mJ / m ² , and the surface average Roughness Sa was 2 nm.

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

The thickness of the particle-containing coating layer was measured by cutting the release film using a microtome and exposing the cross section according to the method described above, then etching with Ar ions to deposit Pt, followed by SEM (S-4800, Hitachi Measured by observing with a high-tech product.

The surface free energy (unit: mJ/m ² ) of the surface of the particle-containing coating layer was measured at 25° C. using a contact angle meter ("DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.) as described above. , was calculated from the measured values of the contact angles obtained by dropping droplets of purified water, methylene iodide and ethylene glycol on the surface of the particle-containing coating layer.

The fluorine atom concentration and silicon atom concentration on the surface of the particle-containing coating layer were measured using an XPS device (PHI Quantera II, manufactured by ULVAC-Phi, Inc.) according to the method described above. In the above measurements, monochromatic Al-Kα rays (25 W/15 kV) were used as the X-ray light source, and X-rays were directed at the surface of the particle-containing coating layer from a direction of 20 degrees with respect to the surface of the particle-containing coating layer. irradiated. Also, in the measurement, an electron gun and a low speed ion gun were used together for charging correction.
In addition, in the spectrum obtained by analyzing the surface of the particle-containing coating layer by XPS according to the above method, when peaks derived from silicon or silicon-containing compounds were confirmed, only peaks derived from silica were observed, and silicone compounds and the like were observed. No peak derived from a compound having a siloxane bond was observed. Therefore, the silicon atom concentration on the surface of the particle-containing coating layer obtained by the above method is the ratio of the content of silicon atoms derived from the peak derived from silica to the content of all atoms detected. was a calculated value.

The maximum protrusion height Sp and surface average roughness Sa on the surface of the particle-containing coating layer were measured using an optical interferometer (“Vertscan 3300G Lite” manufactured by Hitachi High-Tech Co., Ltd.) according to the above-described methods.

In each example and each comparative example, the polyester film before forming the release layer corresponds to a circle with a diameter of 1.5 cm under an environment of a temperature of 23 ° C. and a relative humidity (RH) of 20% according to the above-described measurement method. The peel charge amount (unit: nC) of the surface of the particle-containing coating layer and the surface of the polyester substrate was measured.

〔evaluation〕
[Contamination of Foreign Matter in the Release Layer]
A sample was prepared by cutting the release film obtained in each example and each comparative example into a length of 30 m in the longitudinal direction. Under a three-wavelength fluorescent lamp, the reflected light reflected by the release layer side surface of the obtained sample was observed, and the ability to suppress foreign matter contamination during formation of the release layer was evaluated according to the following criteria.
(Evaluation criteria)
A: No foreign matter was observed.
B: Foreign matter was observed.

[Convex defect (evaluation 1)]
Barium titanate powder (BaTiO ₃ ; manufactured by Sakai Chemical Industry Co., Ltd., product name “BT-03”) 100 parts by mass, polyvinyl butyral resin as a binder (manufactured by Sekisui Chemical Co., Ltd., product name “S-Lec (registered trademark) B · K BM-2") and 4 parts by mass of dioctyl phthalate as a plasticizer (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate deer 1st grade), a mixed solution of toluene and ethanol (mass ratio 6: 4) 135 parts by mass were mixed. The obtained 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 each comparative example were stored under a normal temperature and normal humidity environment for one week. The ceramic slurry was applied to the surface of the release layer of the release film after storage over a width of 250 mm and a length of 10 m using a die coater so that the film thickness after drying was 1 μm. After that, the coating film was dried in a dryer at 80° C. for 1 minute. The release film with the ceramic green sheet produced by the above method was cut into a width of 250 mm and a length of 250 mm. The obtained 10 release films with ceramic green sheets were superimposed so that the surface of the ceramic green sheet and the surface of the particle-containing coating layer were in contact, and a load of 1 kg/cm ² was applied to the obtained laminate for 10 minutes. rice field. After that, the release film was peeled off from the release film with the ceramic green sheet, and the ceramic green sheet for uneven defect evaluation was obtained.
Light from a three-wavelength fluorescent lamp was reflected on the surface of the resulting ceramic green sheet, and the surface of the ceramic green sheet was visually inspected. bottom.
(Evaluation criteria)
A: No defect was found in the ceramic green sheet.
B: One or more defects occurred in the ceramic green sheet.

[Convex defect (evaluation 2)]
The release film obtained in each example and each comparative example was stored for 3 months in a normal temperature and humidity environment, and in the same manner as for the uneven defect (evaluation 1), except that each release film after storage was used. A ceramic green sheet for unevenness defect evaluation was produced.
Using the produced ceramic green sheet, the unevenness defect was evaluated in the same manner as the unevenness defect (Evaluation 1).

〔result〕
Table 1 lists the characteristics of the particle-containing coating layer in each example and each comparative example and each evaluation result.

In the table, the "resin" column, the "crosslinking agent" column, the "particle" column and the "surfactant" column of the "composition" of the "particle-containing coating layer" are the particle-containing coating layer in each example and each comparative example. The types of raw materials contained in the composition for forming the particle-containing coating layer used in the formation of (1) and used as each component constituting the particle-containing coating layer are shown. In addition, "-" in Table 1 indicates that the component is not included.

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

(TOF-SIMS analysis of particle-containing coating layer surface)
Using TOF-SIMS (time-of-flight secondary ion mass spectrometry), the composition of the surface of the particle-containing coating layer side of the polyester film of each example and each comparative example was analyzed. The measuring device and measuring range were as follows. The measurement conditions were appropriately set according to the object to be measured from the conditions described in the instruction manuals attached to the following devices.
Apparatus: (PHI nanoTOF II, manufactured by ULVAC-Phi, Inc.)
Mass range: m/z = 0 to 1000
Measurement range: 100 μm×100 μm
From the analysis results of the surface of the particle-containing coating layer, T is the sum of the secondary ion intensities of all fragment peaks detected by TOF-SIMS analysis, and the fragment with the highest secondary ion intensity among the fragment peaks derived from dimethylsiloxane. The secondary ion intensity of the peak (peak of SiCH ₃ ⁺ fragment ions (M/Z=43)) was defined as P, and the ratio P/T was calculated. As a result, the surface ratio P/T of the particle-containing coating layer of the polyester films produced in Examples 1 to 16 was all less than 0.001. Since the peak intensity of the fragment derived from dimethylsiloxane is small as described above, the particle-containing coating layer included in the polyester film produced in each example and each comparative example was judged not to substantially contain a silicone compound. rice field.

As described above, the polyester films of Examples 1 to 16 according to the present invention are Comparative Example 1 in which the particle-containing coating layer contains a silicone surfactant, and Comparative Example 2 in which the particle-containing coating layer contains a fluorine-based surfactant. It was confirmed that the effect of suppressing the contamination of foreign matter when forming the release layer on the surface of the polyester base material is more excellent than the above.

Further, when the surface free energy of the surface of the particle-containing coating layer is 50 or less, after long-term storage of the release film obtained by forming the release layer on the surface of the particle-containing coating layer, the ceramic formed on the release surface It was confirmed that the green sheet has an effect of suppressing the occurrence of uneven defects (comparison of Examples 1 to 16).

The polyester films obtained in Examples 1 to 16 were measured for thermal shrinkage in the transport direction and width direction at a temperature of 150° C. according to the measurement method described later. As a result, the thermal shrinkage rate in the conveying direction was in the range of 1.29 to 1.61%, and the thermal shrinkage rate in the width direction was in the range of 0.85 to 1.03%. rice field.

[Examples 21 to 26]
Among the components contained in composition A1 (particle-containing coating layer forming composition) used in the particle-containing coating layer forming step of Example 1, components other than particle 1 were mixed, and then the resulting mixture was Then, filtration treatment and membrane degassing were performed in the same manner as composition A1 to prepare composition B1 (particle-free layer-forming composition).
In the [particle-containing coating layer forming step] of Example 1, when the composition A1 was applied to one side of the longitudinally stretched uniaxially oriented polyester base material with a bar coater, a coating film of the composition A1 on the polyester base material was formed. A coating film of composition B1 was formed by applying the above composition B1 to the surface opposite to the coated surface with a bar coater, and the formed coating film of composition A1 was blown with hot air at 100 ° C. Consists of a particle-containing coating layer, a polyester substrate and a particle-free layer according to the method described in Example 1, except that the coating film of composition B1 was also dried with hot air at 100 ° C. when drying at A polyester film (biaxially stretched film) of Example 21 having a layer structure was produced. At this time, the coating amount of composition B1 was adjusted so that the thickness of the formed particle-free layer was 100 nm.

Further, among the components contained in the particle-containing coating layer forming compositions used in the particle-containing coating layer forming steps of Examples 2 to 5 and 13, components other than the particles were mixed, and then the resulting mixture was A particle-free layer-forming composition was prepared by carrying out filtration treatment and membrane degassing in the same manner.
In the same manner as in Example 21, in the [particle-containing coating layer forming step], the surface of the polyester substrate opposite to the surface on which the coating film of the particle-containing coating layer forming composition was formed was coated with a bar coater. Except for forming a coating film of the particle-free layer-forming composition prepared in , and drying the formed coating film of the particle-free layer-forming composition with hot air at 100 ° C. According to the methods described in Examples 2-5 and 13, polyester films (biaxially stretched films) of Examples 22-26 each having a layer structure consisting of a particle-containing coating layer, a polyester base material and a particle-free layer were produced. bottom. The thickness of the formed particle-free layer was 100 nm.

According to the above measurement method, the particle-containing coating layers of the polyester films prepared in Examples 21 to 26 were measured, resulting in thickness, surface free energy, surface fluorine atom concentration and silicon atom concentration, and maximum protrusions on the surface. The height Sp and surface average roughness Sa were the same as the measured values of the polyester films produced in Examples 1 to 5 and 13, respectively. Further, as a result of analyzing the surface of the particle-containing coating layer of the polyester film of Examples 21 to 26 by XPS by the above method, only a peak derived from silica was observed as a peak derived from silicon or a silicon-containing compound, No peak derived from a compound having a siloxane bond such as a silicone compound was observed. Furthermore, as a result of analyzing the composition of the surface of the particle-containing coating layer side of the polyester films of Examples 21 to 26 using TOF-SIMS, the above ratio P/T was all less than 0.001.

According to the method described in Example 1, a release layer was provided on the surface of the particle-free layer side of the polyester films of Examples 21 to 26 to prepare release films of Examples 21 to 26, respectively.
In each of the obtained release films of Examples 21 to 26, the thickness of the release layer after drying was 0.5 μm, the surface free energy of the release layer surface was 15 mJ/m ² , and the surface average roughness Sa was 2 nm.
In addition, as a result of evaluating the release films of Examples 21 to 26 according to the above evaluation method, the performance of suppressing foreign matter contamination during the formation of the release layer, the uneven defect (evaluation 1), and the uneven defect (evaluation 2) were all "A". there were.
In addition, according to the measurement method described later, the thermal shrinkage rate in the transport direction and the width direction at a temperature of 150 ° C. for the polyester films obtained in Examples 21 to 26 was measured. The rates were within the same range as Examples 1-16.

[Examples 31 to 46]
In the above [cooling step], the cooling step of cooling the polyester film thermally relaxed in the thermal relaxation step at a cooling rate of 1500 ° C./min was performed. According to the method, polyester films (biaxially stretched 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 produced.
According to the above measurement method, the particle-containing coating layers of the polyester films produced in Examples 31 to 46 were measured, resulting in thickness, surface free energy, surface fluorine atom concentration and silicon atom concentration, and maximum protrusions on the surface. Each of the height Sp and surface average roughness Sa was the same as the measured values of the polyester films produced in Examples 1-16.

[Measurement of heat shrinkage]
The polyester film obtained in Example 31 was measured for thermal shrinkage in the transport direction and width direction at a temperature of 150° C. according to the following measuring method. As a result, the heat shrinkage rate in the conveying direction was 1.38 to 1.50%, and the heat shrinkage rate in the width direction was 0.83 to 0.90%.
The method for measuring the thermal shrinkage of the polyester film is as follows.
Rectangular samples having a length of 350 mm in the measurement direction (conveying direction or width direction) and a length of 50 mm in the direction perpendicular to the measurement direction were cut out from five points in the width direction of each polyester film. Two reference points were attached at intervals of 300 mm near both ends of the obtained sample in the measurement direction. The resulting sample was left in an oven adjusted to a temperature of 150° C. for 30 minutes and then allowed to cool to room temperature. The distance between gauge points in the sample at room temperature was measured, and this length was defined as L (mm). Calculate the thermal shrinkage rate for each of the five samples using the following formula, and use the maximum and minimum values of the obtained thermal shrinkage rate as the 150 ° C thermal shrinkage rate in each measurement direction as "minimum to maximum %". displayed on
150°C heat shrinkage (%) = 100 x (300-L)/300

The polyester films obtained in Examples 32 to 46 were measured for thermal shrinkage in the transport direction and width direction at a temperature of 150° C. according to the above measuring method. As a result, the thermal shrinkage rate in the conveying direction was in the range of 1.38 to 1.50%, and the thermal shrinkage rate in the width direction was in the range of 0.83 to 0.90%. rice field.

According to the method described in [Release layer forming step] above, a release layer was provided on the opposite side of the particle-containing coating layer of the biaxially stretched films of Examples 31 to 46 (the side without the particle-containing coating layer). Then, release films of Examples 31 to 46 were produced.
For the release films of Examples 31 to 46 obtained, the ability to suppress foreign matter contamination during the formation of the release layer, uneven defects (evaluation 1), and uneven defects (evaluation 2) were evaluated by the above methods. were the same as the evaluation results of the release films of Examples 1 to 16, respectively.

Claims (16)

comprising a polyester base material and a particle-containing coating layer,
A polyester film used for producing a release film by forming a release layer on the surface of the polyester substrate,
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 %, and the silicon atom concentration is 0 to 0. 3.0 atomic percent polyester film. The silicon-containing compound-derived 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 the silica-derived peak. The polyester film according to claim 1, wherein When analyzing the surface of the particle-containing coating layer side by time-of-flight secondary ion mass spectrometry, among the fragment peaks derived from dimethylsiloxane with respect to the total secondary ion intensity (T) of all the fragment peaks detected The polyester film according to claim 1, wherein the ratio (P/T) of the secondary ion strength (P) of the highest fragment peak is less than 0.001. 2. The polyester film of claim 1, wherein said polyester substrate is substantially free of particles. The polyester film according to claim 1, wherein the surface free energy of the surface of the particle-containing coating layer opposite to the polyester substrate is 25 to 50 mJ/m ² . The polyester film according to claim 1, wherein the particle-containing coating layer has a thickness of 1 to 500 nm. The polyester film of claim 1, wherein the particle-containing coating layer comprises at least one binder selected from the group consisting of acrylic resins, urethane resins, and olefin resins. 2. The polyester film according to claim 1, wherein the absolute value of the peeling charge amount on both sides of the polyester film corresponding to a circle with a diameter of 1.5 cm is 0.12 nC or less. A release film comprising the polyester film according to any one of claims 1 to 8 and a release layer laminated on the surface of the polyester film opposite to the particle-containing coating layer. The release film according to claim 9, which is used for producing ceramic green sheets. 10. The release film of Claim 9, wherein the release layer comprises a silicone resin. 10. The release film according to claim 9, wherein the release layer has a surface free energy of 10 to 35 mJ/m ² and an average surface roughness of 0 to 5 nm on the surface opposite to the polyester substrate. The release film according to claim 9, wherein the release film has a thickness of 40 µm or less. 10. The release film of Claim 9, wherein the particle-containing coating layer comprises particles and a hydrocarbon surfactant. A method for producing a polyester film comprising a polyester substrate and a particle-containing coating layer, comprising:
The polyester film is a polyester film used for producing a release film by forming a release layer on the surface of the polyester substrate side,
A step of applying a particle-containing coating layer-forming composition containing particles and a hydrocarbon surfactant to the surface of the polyester substrate opposite to the surface on which the release layer is formed,
A method for producing a polyester film. A ceramic capacitor manufactured using a ceramic green sheet formed on the surface of the release layer of the release film according to claim 9 .