Polyester film

Abstract

The present invention addresses the problem of providing a polyester film having excellent coating properties for a composition containing an organic solvent and excellent high-speed release properties of a sheet formed on the surface of a release layer. This polyester film according to the present invention comprises a release layer and a polyester base material, wherein the release layer is obtained by curing a release layer-forming composition that is coated in-line, and the release layer-forming composition contains an acrylic resin A having a siloxane bond.

Description

Polyester film

[0001] The present invention relates to a polyester film.

[0002] Polyester films are used in a variety of applications, such as films for touch panels, films for optical components, substrates for molding, substrates for decorative films, and substrates for photosensitive layers.

[0003] One application of polyester films is as a release film, which is a polyester substrate having a release layer formed thereon, various components being produced in contact with the release layer, and then the components are released.

[0004] Here, when providing a release layer on a polyester substrate, an offline coating method is mainly used to coat a polyester substrate, which is a commercially available polyester film, with a release layer-forming composition containing an organic solvent as the main solvent (see, for example, Patent Document 1). However, in this manufacturing method, the film substrate forming process and the release layer forming process are separate processes, which leads to increased costs. Therefore, Patent Document 2 adopts a so-called in-line coating method in which a release layer-forming composition containing water as the main solvent is coated during the film forming process of the polyester substrate.

[0005] Here, when a polyester film is used as a release film, a composition containing an organic solvent (for example, a ceramic slurry) is applied to the release layer surface of the polyester film, and a sheet (for example, a ceramic green sheet) is formed on the release layer surface.Therefore, the release layer of the polyester film is required to have excellent coating properties for the composition containing an organic solvent.However, as described in Patent Document 2, when a release layer is formed using a composition for forming a release layer containing a silicone resin (i.e., a resin whose polymer main chain is a siloxane bond), the wettability of the composition containing an organic solvent, such as a ceramic slurry, on the release layer may be insufficient, resulting in repellency defects.

[0006] In response to such problems, Patent Document 3 discloses a technique for improving coatability without using a silicone resin as the resin contained in a release layer-forming composition containing water as the main solvent.

[0007] International Publication No. 2018 / 150255 International Publication No. 2023 / 281972 International Publication No. 2021 / 192896

[0008] According to the technology described in the above-mentioned Patent Document 3, since a composition for forming a release layer that does not contain a silicone resin is used, the coating property tends to be improved. However, when the peeling speed when peeling off the sheet formed on the surface of the release layer is increased (i.e., when the sheet is peeled off at high speed), the sheet's peelability is insufficient. Thus, in the release layer contained in the polyester film, it is difficult to achieve both excellent coating property of the composition containing an organic solvent and excellent high-speed peelability of the sheet formed on the surface of the release layer.

[0009] Therefore, an object of the present invention is to provide a polyester film that has excellent coatability with compositions containing organic solvents and also has excellent high-speed peelability of a sheet formed on the release layer surface.

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, they have found that the above problems can be solved by the following configuration.

[0011] [1] A polyester film comprising a release layer and a polyester substrate, wherein the release layer is a layer obtained by curing an in-line applied composition for forming a release layer, and the composition for forming a release layer comprises an acrylic resin A having a siloxane bond. [2] The polyester film according to [1], wherein the acrylic resin A comprises a structural unit derived from a monomer A1, which is an acrylic monomer having a siloxane bond, and the molecular weight of the monomer A1 is 100 to 4,000. [3] The polyester film according to [1] or [2], wherein the content of silicon atoms on the surface of the release layer is 2 atm% or more relative to the total element content on the surface of the release layer. [4] The polyester film according to any one of [1] to [3], wherein the polyester substrate is substantially free of particles, and the maximum projection height Sp on the surface of the release layer is less than 35 nm. [5] The polyester film according to any one of [1] to [4], wherein the release layer-forming composition contains a crosslinking agent B; the acrylic resin A has a reactive group A containing at least one selected from the group consisting of a carboxy group, a carboxylic acid anhydride group, a carboxylate group, and a hydroxyl group; and the crosslinking agent B has a reactive group B capable of reacting with the reactive group A. [6] The polyester film according to [5], wherein the reactive group B contains at least one selected from the group consisting of an oxazoline group, a carbodiimide group, an epoxy group, a methylol group, an isocyanate group, and a blocked isocyanate group. [7] The polyester film according to [5] or [6], wherein the crosslinking agent B is an acrylic resin having the reactive group B in a side chain. [8] The polyester film according to any one of [5] to [7], wherein the total content of the acrylic resin A and the crosslinking agent B is 98 to 100 mass % based on the total mass of the solid content of the release layer-forming composition. [9] The polyester film according to any one of [1] to [8], wherein the acid value of the acrylic resin A is 0.5 to 4.5 mmol / g.

[10] The polyester film according to any one of [1] to [9], wherein the thickness of the release layer is less than 90 nm.

[11] The polyester film according to any one of [1] to

[10] , wherein the acrylic resin A further contains a structural unit derived from a monomer A3 having a ClogP value of 0.8 or more.

[12] The polyester film according to any one of [1] to

[11] , which is used for producing a ceramic green sheet.

[0012] According to the present invention, a polyester film can be provided which has excellent coatability with compositions containing organic solvents and excellent high-speed peelability of a sheet formed on the release layer surface.

[0013] 1 is a side view schematically illustrating an example of a polyester film of the present invention. 2 is a schematic view illustrating an example of a stretching machine used in producing the polyester film of the present invention.

[0014] The present invention will be described in detail below. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0015] The meaning of each description in this specification is explained below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another staged numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0016] In this specification, "longitudinal direction" refers to the longitudinal direction of the film during film production, and is synonymous with "conveyance direction" and "machine direction." In this specification, "width direction" refers to a direction perpendicular to the longitudinal direction. In this specification, "perpendicular" is not limited to strictly perpendicular, but also includes approximately perpendicular. "Approximately perpendicular" means intersecting within a range of 90°±5°, preferably within a range of 90°±3°, and more preferably within a range of 90°±1°.

[0017] In addition, in this specification, for each component, a substance corresponding to the component may be used alone or in combination of two or more. Here, when two or more substances for each component are used in combination, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.

[0018] The content (mass%) of each structural unit relative to the total units contained in the acrylic resin was determined by measuring the acrylic resin with proton nuclear magnetic resonance ( １ It is determined by analysis using a H-NMR method.

[0019] [Polyester Film] The polyester film of the present invention comprises a release layer and a polyester substrate, wherein the release layer is a layer formed by curing an in-line applied release layer-forming composition, and the release layer-forming composition comprises an acrylic resin A having a siloxane bond. Hereinafter, the release layer-forming composition will also be referred to as "composition L." FIG. 1 is a side view schematically illustrating an example of the polyester film of the present invention. The polyester film 300 comprises a polyester substrate 310 and a release layer 320. The polyester substrate 310 is disposed on one side 321 of the release layer 320. The other side 322 of the release layer 320 is the surface opposite to the side of the release layer 320 on which the polyester substrate 310 is disposed (i.e., one side 321), and may be referred to as the release layer surface or release surface.

[0020] The polyester film of the present invention exhibits excellent coatability with compositions containing organic solvents and excellent high-speed peelability of sheets formed on the release layer surface. While the details of the reasons for this are unclear, it is generally assumed as follows. Since the release layer is formed using composition L containing acrylic resin A having siloxane bonds, the release layer contains siloxane bonds derived from acrylic resin A. It is presumed that the siloxane bonds in the release layer reduce the surface free energy of the release layer surface, thereby improving the peelability of sheets (particularly ceramic green sheets) formed on the release layer surface. Furthermore, it is presumed that the release layer is formed using composition L containing acrylic resin A having siloxane bonds in its molecules, thereby adjusting the surface free energy of the release layer within an appropriate range, thereby improving the coatability of compositions containing organic solvents (e.g., ceramic slurries).

[0021] <Polyester substrate> The polyester substrate is a film-like object containing a polyester resin as a main component. Here, the "main component" refers to the component that is contained in the largest amount (by mass) of all the components contained in the film-like object.

[0022] The polyester substrate is preferably a biaxially oriented polyester substrate. "Biaxial orientation" refers to the property of having molecular orientation in two axial directions. The molecular orientation is measured using a microwave transmission molecular orientation meter (for example, MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The angle between the two axial directions is preferably within the range of 90°±5°, more preferably within the range of 90°±3°, and even more preferably within the range of 90°±1°. The molecular orientation changes when stretching is performed, and a biaxially oriented polyester substrate can be produced by performing biaxial stretching.

[0023] Preferably, the polyester substrate is substantially free of inorganic particles. In-line application of composition L to a polyester substrate free of inorganic particles can improve the smoothness of the release layer surface. "Substantially free of inorganic particles" is defined as the content of inorganic particles being 50 ppm by mass or less, preferably 10 ppm by mass or less, and more preferably below the detection limit, relative to the total mass of the polyester substrate when quantitatively analyzing elements derived from inorganic particles using fluorescent X-ray analysis. This is because, even if inorganic particles are not actively added to the polyester substrate, contaminants derived from foreign matter, raw resins, or dirt attached to the line or equipment during the polyester substrate manufacturing process may peel off and be mixed into the polyester substrate. Examples of inorganic particles include inorganic particles that may be contained in the particle-containing layer (protrusion-containing layer) described below.

[0024] Preferably, the polyester substrate is substantially free of particles. Examples of particles include the inorganic particles and organic particles described above. Whether or not the polyester substrate is substantially free of particles can be confirmed by the following procedure. Ten different locations on the cross section of the polyester substrate are observed using a scanning electron microscope to confirm the presence or absence of particles with a size of 10 nm to 10 μm in the cross section of the polyester substrate. The magnification during observation is adjusted to 5,000 to 20,000 times. If particles are observed in any location, this means that particles are contained in the release layer. On the other hand, if particles are not observed in any cross section, this means that particles are not contained in the polyester substrate. Here, examples of organic particles include organic particles contained in the particle-containing layer (protrusion-containing layer) described below.

[0025] (Polyester Resin) The polyester resin contained in the polyester base material is a polymer having an ester bond in the main chain. The polyester resin is usually formed by polycondensation of a dicarboxylic acid compound and a diol compound, which will be described later. There are no particular limitations on the polyester resin, and known polyester resins can be used. Examples of polyester resins include polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), and copolymers thereof. PET, PEN, and copolymers thereof are preferred, and PET is more preferred.

[0026] The intrinsic viscosity (IV) of the present film is preferably 0.50 dl / g or more but less than 0.80 dl / g, more preferably 0.55 dl / g or more but less than 0.70 dl / g, and even more preferably 0.60 dl / g or more but less than 0.70 dl / g. The intrinsic viscosity (IV) of the present film can be determined by dissolving the present film in a mixed solvent of 1,1,2,2-tetrachloroethane / phenol (=2 / 3 [mass ratio]) to obtain a solution, and then measuring the solution viscosity of the solution at 25°C. The amount of terminal carboxyl groups (terminal COOH amount, AV; Acid Value) of the present film is preferably 3.5 eq / ton or less, more preferably 3.0 eq / ton or less, and even more preferably 2.8 eq / ton or less. The lower the terminal COOH amount, the more likely the water content is to decrease. The lower limit is, for example, 0.5 eq / ton or more. The amount of terminal COOH groups in the present film can be calculated from the titration amount obtained by completely dissolving the present film in a mixed solvent of benzyl alcohol / chloroform (=2 / 3; volume ratio) to obtain a solution, and then titrating the solution with a reference solution (0.01 N KOH-benzyl alcohol mixed solution) using phenol red as an indicator. In this specification, "eq / ton" represents the molar equivalent per ton. 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 to 90°C, more preferably 70 to 85°C.

[0027] The method for producing the polyester resin is not particularly limited, and any known method can be used. For example, the 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.

[0028] Catalyst The catalyst used in the production of polyester resins is not particularly limited, and known catalysts that can be used in the synthesis of polyester resins can be used. Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds or aluminum compounds are preferred because they are less likely to produce foreign matter or voids in the polyester substrate. A single catalyst may be used, or two or more catalysts may be used in combination. It is also preferable to use at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds in combination with a phosphorus compound. When using a combination of catalysts, it is preferable to adopt the types and amounts of each compound described in paragraphs 0055 to 0062 of Japanese Patent Publication No. 5,575,671. In the present film, when the content of the titanium compound is 5 to 15 mass ppm in terms of Ti element, the content of the magnesium compound is preferably 60 to 90 mass ppm in terms of Mg element, and the content of the phosphorus compound is preferably 5 to 35 mass ppm in terms of P element.

[0029] The titanium compound is preferably an organic chelate titanium complex. The organic chelate titanium complex is a titanium compound having an organic acid as a ligand. Examples of organic acids include citric acid, lactic acid, trimellitic acid, and malic acid. The titanium compounds described in paragraphs

[0049] to

[0053] of Japanese Patent No. 5575671 can also be used, and the contents of this publication are incorporated herein by reference. The content of the titanium compound is preferably 1 to 300 ppm, more preferably 3 to 20 ppm, and even more preferably 5 to 15 ppm, in terms of elemental Ti relative to the total mass of the film. The content of each element can be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0030] Examples of the aluminum compound include organoaluminum compounds and partial hydrolysates thereof. The organoaluminum compound is preferably a carboxylate, an inorganic acid salt, or a chelate compound, and more preferably aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, or aluminum acetylacetonate.

[0031] Dicarboxylic Acid Compound Examples of the dicarboxylic acid compound include dicarboxylic acids such as aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or aromatic methyl dicarboxylates are preferred.

[0032] Examples of the aliphatic dicarboxylic acid compound include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of the alicyclic dicarboxylic acid compound include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

[0033] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorene acid. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, and terephthalic acid is more preferred.

[0034] The dicarboxylic acid compound may be used alone or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, terephthalic acid may be used alone or may be copolymerized with other aromatic dicarboxylic acids such as isophthalic acid or aliphatic dicarboxylic acids.

[0035] Diol Compound Examples of the diol compound include an aliphatic diol compound, an alicyclic diol compound, and an aromatic diol compound, and an aliphatic diol compound is preferred.

[0036] Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred. Examples of alicyclic diol compounds include cyclohexanedimethanol, spiroglycol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. Only one type of diol compound may be used, or two or more types may be used in combination.

[0037] Terminal Capping Agent In the production of the polyester resin, a terminal capping agent may be used as needed. By using the terminal capping agent, a structure derived from the terminal capping agent is introduced into the terminal of the polyester resin. The terminal capping agent is not limited, and known terminal capping agents can be used. Examples of terminal capping agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds. For terminal capping agents, reference can also be made to the contents of paragraphs

[0055] to

[0064] of JP 2014-189002 A, the contents of which are incorporated herein by reference.

[0038] Production Conditions The reaction temperature is not limited and may be set appropriately depending on the raw materials. The reaction temperature is preferably 260 to 300°C, more preferably 275 to 285°C. The pressure is not limited and may be set appropriately depending on the raw materials. The pressure is not limited and may be set appropriately depending on the raw materials. －３ ~1.33 x 10 －５ MPa is preferred, and 6.67 × 10 －４ ~6.67 x 10 －５ MPa is more preferred.

[0039] As a method for synthesizing a polyester resin, the method described in paragraphs

[0033] to

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

[0023] to

[0046] of International Publication No. 2023 / 149181 can also be referenced, and the contents of this publication are incorporated herein by reference.

[0040] The content of the polyester resin in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polyester substrate. The upper limit of the content of the polyester resin is not limited and can be appropriately set within a range of less than 100% by mass based on the total mass of the polyester substrate.

[0041] When the polyester base material contains polyethylene terephthalate, the content of polyethylene terephthalate is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, still more preferably 98 to 100 mass%, and particularly preferably 100 mass%, relative to the total mass of the polyester resin in the polyester base material.

[0042] The polyester substrate may contain components other than the polyester resin (for example, a catalyst, unreacted raw material components, particles, water, etc.).

[0043] The thickness of the polyester substrate is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, and particularly preferably 35 μm or less. There is no particular lower limit to the thickness, but from the viewpoint of improving strength and processability, it is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 10 μm or more, and particularly preferably 20 μm or more. The thickness of the polyester substrate is determined by preparing a slice having a cross section perpendicular to the main surface of the polyester film and measuring the thickness of the polyester substrate at five points in the slice using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0044] <Release layer> The release layer is a layer obtained by curing an in-line applied release layer-forming composition, and is disposed on one side of the polyester substrate. The method for forming the release layer will be described later in the section on the method for producing a polyester film. When the polyester film of the present invention is used as a release film, various members are produced in contact with the release layer, and then the members are peeled off.

[0045] (Release Layer-Forming Composition) The release layer contained in the polyester film of the present invention is a layer obtained by curing an in-line applied release layer-forming composition (composition L). Composition L also contains an acrylic resin A having a siloxane bond.

[0046] Acrylic Resin A The acrylic resin A is a resin having a siloxane bond and containing a structural unit derived from a (meth)acrylic acid ester. In this specification, the term "(meth)acrylic acid ester" refers to a concept including a methacrylic acid ester and an acrylic acid ester. The acrylic resin A is already present in the form of a polymer in the composition for forming a release layer. In other words, the acrylic resin A is not intended to be a polymer that exists as a monomer consisting of a (meth)acrylic acid ester in the composition L and is polymerized when forming the release layer.

[0047] The siloxane bond is —[O—Si(R) ２ ]- is preferably a structure represented by -[O-Si(R) ２ In the formula (I), each of the plurality of R independently represents an alkyl group. Examples of the alkyl group represented by R include a linear alkyl group having 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms) and a branched or cyclic alkyl group having 3 to 12 carbon atoms (preferably 3 to 6 carbon atoms). Specific examples include a methyl group, an ethyl group, a propyl group, an n-butyl group, a hexyl group, an octyl group, an isopropyl group, an isobutyl group, a 2-ethylhexyl group, a tert-butyl group, a tert-octyl group, and a cyclohexyl group. Among these, in terms of achieving superior effects of the present invention, R is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, an isopropyl group, an isobutyl group, or a tert-butyl group, and even more preferably a methyl group, an ethyl group, a propyl group, or a butyl group. The plurality of R may be the same or different.

[0048] Monomer A1 The acrylic resin A preferably contains a structural unit derived from a radically polymerizable monomer having a siloxane bond, and from the viewpoint of achieving superior effects of the present invention, it preferably contains a structural unit derived from Monomer A1, which is an acrylic monomer having a siloxane bond. Monomer A1 is preferably a (meth)acrylic acid ester having a siloxane bond. Preferred embodiments of the siloxane bond in Monomer A1 are as described above.

[0049] Monomer A1 is —Si[—O—SiR １ (R ２ ) ２ ] ３ and a group represented by —[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ In the formula, R １ represents an alkyl group or an aryl group, and a plurality of R ２ and multiple R ３ each independently represents an alkyl group, and m represents an integer of 2 or more. １ is an alkyl group, R １ Specific examples and preferred embodiments of the alkyl group in the formula (I) are the above-mentioned —[O—Si(R) ２ ]- is the same as R in the group represented by R １ When R is an aryl group, the number of carbon atoms in the aryl group is preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 12. Specific examples of the aryl group include a phenyl group, a styryl group, a naphthyl group, and a biphenyl group. ２ and R ３ Specific examples and preferred embodiments of the alkyl group in the formula (I) are the above-mentioned —[O—Si(R) ２ m is an integer of 2 or more, preferably an integer of 2 to 100, and more preferably an integer of 5 to 50.

[0050] The molecular weight of monomer A1 is preferably 100 to 4000, more preferably 500 to 3000, and even more preferably 700 to 2000, from the viewpoint of achieving superior high-speed releasability of the sheet formed on the surface of the release layer. Details of the method for measuring the molecular weight of monomer A1 are as described in the Examples section. Here, when monomer A1 is a mixture of monomers with different molecular weights, the peak with the greatest intensity detected by MS spectrometry is read, and this molecular weight is taken as the molecular weight of monomer A1.

[0051] Monomer A1 is preferably a compound represented by the following formula (A1-1).

[0052] CH ２ = C(R １１ ) C(O)O-L １１ -Rh (A1-1)

[0053] In formula (A1-1), R １１ is a hydrogen atom or a methyl group.

[0054] In formula (A1-1), L １１ is an alkylene group which may have a substituent. １１ The alkylene group in may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear. １１ The number of carbon atoms in the alkylene group in the formula (I) is preferably 1 to 10, more preferably 1 to 7, and even more preferably 1 to 5. Specific examples of the substituent that the alkylene group may have include a halogen atom, a hydroxy group, an alkoxy group (preferably having 1 to 5 carbon atoms), a carboxy group, and the like. １１ is preferably an alkylene group having no substituent, more preferably a propylene group, an ethylene group, or a methylene group.

[0055] In formula (A1-1), Rh is a substituent having a siloxane bond. The substituent in Rh is —Si[—O—SiR １ (R ２ ) ２ ] ３ or a group represented by —[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ In view of the superior high-speed releasability of the sheet formed on the surface of the release layer, it is preferable to use a group represented by -[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ It is more preferable that R １ ~R３ The definitions of , and m are as described above.

[0056] Specific examples of Monomer A1 include organosilyl group-containing monomers such as 3-[tris(trimethylsilyloxy)silyl]propyl (meth)acrylate, Silaplane FM-0711 (manufactured by JNC Corporation), Silaplane FM-0721 (manufactured by JNC Corporation), Silaplane FM-0725 (manufactured by JNC Corporation), Silaplane TM-0701T (manufactured by JNC Corporation), X-22-174ASX (manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-174BX (manufactured by Shin-Etsu Chemical Co., Ltd.), KF-2012 (manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2426 (manufactured by Shin-Etsu Chemical Co., Ltd.), and X-22-2404 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0057] When the acrylic resin A has a structural unit derived from monomer A1, the content of the structural unit derived from monomer A1 is preferably 10 to 90% by mass, more preferably 15 to 85% by mass, and even more preferably 20 to 80% by mass, relative to the total structural units (100% by mass) of the acrylic resin A. When the content of the structural unit derived from monomer A1 is 10% by mass or more, the release properties of the sheet formed on the release layer surface are superior. Furthermore, when the content of the structural unit derived from monomer A1 is 90% by mass or less, the coatability of the composition containing an organic solvent is superior.

[0058] Monomer A2 The acrylic resin A preferably contains a structural unit derived from monomer A2 containing at least one selected from the group consisting of a carboxy group, a carboxylic acid anhydride group, and a carboxylic acid salt group. This results in superior water solubility and curability of the resin. Monomer A2 preferably does not contain a siloxane bond. When composition L contains acrylic resin A containing a structural unit derived from monomer A2 and crosslinking agent B described below, a crosslinked structure can be formed in the release layer by reaction of at least one selected from the group consisting of a carboxy group, a carboxylic acid anhydride group, and a carboxylic acid salt group with crosslinking agent B (preferably reactive group B described below) during the formation of the release layer. Examples of carboxylic acid anhydride groups include groups based on acid anhydrides such as maleic anhydride and itaconic anhydride. Examples of carboxylic acid salt groups include alkali metal salts of carboxy groups, organic amine salts of carboxy groups, and ammonium salts of carboxy groups.

[0059] Examples of the monomer A2 include carboxy group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid, and salts thereof (for example, sodium salts, potassium salts, ammonium salts, and tertiary amine salts); acid anhydride monomers such as maleic anhydride and itaconic anhydride; and (meth)acrylic acid esters having a carboxy group or a carboxylic acid salt group.

[0060] Specific examples of the (meth)acrylic acid ester having a reactive group A include carboxy group-containing (meth)acrylic acid esters such as 2-methacryloyloxyethyl succinate, 2-acryloyloxyethyl hexahydrophthalate, and ω-carboxy-polycaprolactone monoacrylate.

[0061] When the acrylic resin A has a structural unit derived from monomer A2, the content of the structural unit derived from monomer A2 is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass, relative to the total structural units (100% by mass) of the acrylic resin A. When the content of the structural unit derived from monomer A2 is 5% by mass or more, the water solubility and curability of the resin are superior. Furthermore, when the content of the structural unit derived from monomer A2 is 30% by mass or less, the releasability of the release film is superior.

[0062] Monomer A3: It is preferable that the acrylic resin A further contains a structural unit derived from Monomer A3 having a ClogP value of 0.8 or more. This improves the high-speed releasability of the sheet formed on the surface of the release layer. It is preferable that Monomer A3 does not have a siloxane bond, a carboxy group, a carboxylic anhydride group, or a carboxylic acid salt group.

[0063] The ClogP value of Monomer A3 is 0.8 or more, and from the viewpoint of superior high-speed releasability of the sheet formed on the surface of the release layer, it is preferably 1.0 or more, more preferably 1.2 or more. From the viewpoint of polymer synthesis suitability, the ClogP value of Monomer A3 is preferably 6.0 or less, more preferably 5.0 or less, and even more preferably 4.0 or less. Here, the ClogP value is the value obtained by calculating the common logarithm logP of the partition coefficient P between 1-octanol and water. Known methods and software can be used to calculate the ClogP value, but unless otherwise specified, the ClogP program incorporated into Cambridgesoft's ChemBioDraw Ultra 13.0 will be used in the present invention.

[0064] From the viewpoint of copolymerizability with Monomer A1 and Monomer A2, Monomer A3 preferably has a polymerizable group such as a (meth)acryloyloxy group or a vinyl group. The (meth)acryloyloxy group represents a concept including an acryloyloxy group and a methacryloyloxy group.

[0065] Specific examples of Monomer A3 include (meth)acrylic acid esters such as 2-methoxyethyl acrylate (MEA), 2-hydroxy-3-phenoxypropyl acrylate (HPPA), ethylene glycol monoacetoacetate monomethacrylate (EGMM), t-butyl acrylate (tBA), benzyl methacrylate (BnMA), phenoxyethyl acrylate (PEA), n-butyl acrylate (nBA), cyclohexyl acrylate (CyHA), tetrahydrofurfuryl methacrylate (THFMA), cyclohexyl methacrylate (CyHMA), methyl methacrylate (MMA), caprolactone-modified methacrylate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, dicyclopentanyl methacrylate, and isobornyl methacrylate; styrene (St), α-methylstyrene; and the like.

[0066] When the acrylic resin A has a structural unit derived from monomer A3, the content of the structural unit derived from monomer A3 is preferably 5 to 30% by mass, more preferably 7 to 25% by mass, and even more preferably 10 to 20% by mass, relative to the total structural units (100% by mass) possessed by monomer A3. When the content of the structural unit derived from monomer A3 is 5% by mass or more, the high-speed releasability of the sheet formed on the surface of the release layer is superior. Furthermore, when the content of the structural unit derived from monomer A3 is 30% by mass or less, the high-speed releasability of the sheet formed on the surface of the release layer is superior.

[0067] Other Monomers The acrylic resin A may contain structural units derived from monomers other than the monomers A1 to A3 (hereinafter also referred to as "other monomers").

[0068] A specific example of the other monomer is a (meth)acrylic acid ester containing a polyalkylene oxide chain. Specific examples of the polyalkylene oxide chain include polymethylene oxide, polyethylene oxide, polypropylene oxide, and polybutylene oxide. The number of repeating units of the polyalkylene oxide chain is preferably 3 to 100.

[0069] Examples of (meth)acrylic acid esters containing a polyalkylene oxide chain include methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate.

[0070] Specific examples of monomers other than (meth)acrylic acid esters containing a polyalkylene oxide chain include: hydroxyl group-containing monomers such as 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol monomethacrylate, and 4-hydroxybutyl (meth)acrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; sulfo group-containing monomers such as styrene sulfonic acid and salts thereof; phosphate group-containing monomers such as 2-methacryloyloxyethyl acid phosphate and salts thereof; Amide group-containing monomers such as (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N,N-dialkyl(meth)acrylate (examples of the alkyl group: methyl group, ethyl group, n-butyl group, isobutyl group, etc.), acryloylmorpholine, N-methylol(meth)acrylamide, N-isopropylacrylamide, diacetone acrylamide, and N-phenyl(meth)acrylamide; vinyl isocyanate, allyl isocyanate, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, (meth)acrylonitrile vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene.

[0071] When the acrylic resin A has a structural unit derived from another monomer, the content of the structural unit derived from the other monomer is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 5 to 15% by mass, relative to all structural units (100% by mass) contained in the acrylic resin A.

[0072] Preferred embodiment of acrylic resin A One preferred embodiment of the acrylic resin A is an embodiment containing a structural unit derived from monomer A1 and a structural unit derived from monomer A2, and more preferably an embodiment containing a structural unit derived from monomer A1, a structural unit derived from monomer A2, and a structural unit derived from monomer A3. This provides better effects of the present invention.

[0073] One preferred embodiment of the acrylic resin A is one having a reactive group A containing at least one selected from the group consisting of a carboxy group, a carboxylic anhydride group, a carboxylate salt group, and a hydroxyl group. When the composition L contains the acrylic resin A having the reactive group A and the crosslinking agent B described below, a crosslinked structure can be formed in the release layer by the reaction of the reactive group A with the crosslinking agent B (preferably the reactive group B described below) when forming the release layer. This allows for a release layer with excellent curability to be obtained. In terms of better effects of the present invention, the reactive group A is preferably a carboxy group or a carboxylate salt group, which is a salt of a carboxy group.

[0074] When the acrylic resin A has at least one selected from the group consisting of an acid group, a hydroxyl group, and a polyalkylene oxide chain, the acrylic resin has excellent solubility in a solvent (particularly water). When an acrylic resin A having excellent solubility in a solvent (particularly water) is used, the coating uniformity of the composition L on the polyester substrate is improved, and a release layer with excellent surface smoothness (a release layer with few coating defects) is obtained. In particular, when the acrylic resin A has high solubility in water, it is suitable for a manufacturing method in which the composition L is coated before the stretching step (a so-called in-line coating method), and the in-line coating method improves the uniform coating property, thereby obtaining a release layer with excellent surface smoothness.

[0075] The acid value of acrylic resin A is preferably 0.3 to 6.0 mmol / g, more preferably 0.4 to 5.5 mmol / g, even more preferably 0.5 to 4.5 mmol / g, particularly preferably 0.5 to 3.0 mmol / g, and most preferably 0.5 to 2.5 mmol / g. The hydroxyl value of acrylic resin A is preferably 0 to 3.0 mmol / g, more preferably 0 to 2.5 mmol / g, and even more preferably 0 to 2.0 mmol / g. When the acid value or hydroxyl value is equal to or greater than the above-mentioned lower limit, the water solubility and curability of acrylic resin A are superior. When the acid value or hydroxyl value is equal to or less than the above-mentioned lower limit, the high-speed releasability of the release film is superior. The calculation methods for the acid value and hydroxyl value are as described in the Examples section below. In this specification, "excellent water solubility" of acrylic resin A means that the acrylic resin A receives a rating of "B" or higher when subjected to the water solubility evaluation test described in the Examples section below.

[0076] The weight average molecular weight (Mw) of the acrylic resin A is preferably 5,000 to 100,000, more preferably 7,000 to 80,000, and even more preferably 10,000 to 50,000. If the Mw of the acrylic resin A is 5,000 or more, the release layer has better coating suitability for production. Furthermore, if the Mw of the acrylic resin A is 100,000 or less, the release film has better high-speed releasability. The method for measuring the Mw of the acrylic resin A is as described in the Examples section below.

[0077] The composition L may contain only one type of acrylic resin A, or may contain two or more types of acrylic resin A. The content of the acrylic resin A is preferably 20 to 90 mass %, more preferably 30 to 80 mass %, based on the total mass of the solid content (components other than the solvent; the same applies hereinafter) of the composition L.

[0078] Crosslinking Agent B Composition L preferably contains crosslinking agent B. Crosslinking agent B is preferably water-soluble in view of suitability for in-line application. Crosslinking agent B preferably has a reactive group B capable of reacting with the above-mentioned reactive group A. When acrylic resin A has a reactive group A and crosslinking agent has a reactive group B, a crosslinked structure can be formed in the release layer by the reaction between reactive group A and reactive group B when forming the release layer, resulting in better curability of the release layer.

[0079] When the acrylic resin A has an acid group, the reactive group B is preferably an oxazoline group, a carbodiimide group, an epoxy group, a methylol group, an isocyanate group, or a blocked isocyanate group, because of its excellent reactivity with a carboxy group. Among these, from the viewpoint of superior high-speed releasability of the sheet formed on the release layer surface, an oxazoline group, an epoxy group, or a carbodiimide group is more preferred, an oxazoline group or an epoxy group is even more preferred, and an oxazoline group is particularly preferred. Here, the blocked isocyanate group refers to a group in which an isocyanate group is blocked with a blocking agent (e.g., a compound having an active hydrogen group). When the acrylic resin A has a hydroxyl group, the reactive group B is preferably an isocyanate group, a methylol group, or a blocked isocyanate group, because of its excellent reactivity with a hydroxyl group.

[0080] The crosslinking agent B having a reactive group B is not particularly limited, and examples thereof include one or more crosslinking agents selected from the group consisting of oxazoline compounds, isocyanate compounds, carbodiimide compounds, melamine compounds, and epoxy compounds. The isocyanate compound may be a compound having a blocked isocyanate group in which the isocyanate group is blocked with a blocking agent. Among these, oxazoline compounds, epoxy compounds, and carbodiimide compounds are more preferred, oxazoline compounds and epoxy compounds are even more preferred, and oxazoline compounds are particularly preferred, in view of the superior high-speed releasability of the sheet formed on the release layer surface.

[0081] Oxazoline-based compounds The oxazoline-based compounds are not particularly limited as long as they are compounds having an oxazoline group, and may be low-molecular-weight compounds having a weight-average molecular weight (Mw) of 1,000 or less, or high-molecular-weight compounds having a weight-average molecular weight (Mw) of more than 1,000. However, high-molecular-weight compounds are preferred because they provide superior high-speed releasability for the sheet formed on the surface of the release layer.

[0082] Examples of low molecular weight compounds having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2'-bis-(2-oxazoline), 2,2'-methylene-bis-(2-oxazoline), 2,2'-ethylene-bis-(2-oxazoline), 2,2'-trimethylene-bis- (2-oxazoline), 2,2'-tetramethylene-bis-(2-oxazoline), 2,2'-hexamethylene-bis-(2-oxazoline), 2,2'-octamethylene-bis-(2-oxazoline), 2,2'-ethylene-bis-(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis-(2-oxazoline), 2,2'-m-phenylene-bis-(2-oxazoline), 2,2'-m-phenylene-bis-(4,4'-dimethyl-2-oxazoline), bis-(2-oxazolinylcyclohexane)sulfide, and bis-(2-oxazolinylnorbornane)sulfide are examples of the oxazolinyl compounds.

[0083] When the oxazoline compound is a polymer compound, it is sufficient that the polymer compound has an oxazoline group, and examples thereof include copolymers containing the above-mentioned low molecular weight compound having an oxazoline group as a constituent unit.

[0084] The polymer compound having an oxazoline group is preferably an acrylic polymer having an oxazoline group, and more preferably an acrylic polymer containing an oxazoline group and a polyalkylene oxide chain. When the polymer compound having an oxazoline group contains a polyalkylene oxide chain, the water solubility of the crosslinking agent B can be improved, and the in-line coating suitability can be further improved.

[0085] Examples of the polyalkylene oxide chain include polymethylene oxide, polyethylene oxide, polypropylene oxide, and polybutylene oxide. The number of repeating units of the polyalkylene oxide chain is preferably 3 to 100.

[0086] Examples of (meth)acrylic acid esters containing a polyalkylene oxide chain include methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate.

[0087] The polymer compound having an oxazoline group may contain a constituent unit derived from a low molecular weight compound having an oxazoline group and a constituent unit derived from a monomer other than the constituent unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain.

[0088] Other monomers include, for example, alkyl group-containing monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate; hydroxy-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and glycerol monomethacrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; styrene sulfonic acid, 3-sulfopropyl potassium methacrylate, and 2-acrylamido-2-methylpropional; Examples of the other monomer include sulfo group-containing monomers such as phenylsulfonic acid; amide group-containing monomers such as (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N,N-dialkyl(meth)acrylate (examples of the alkyl group: methyl group, ethyl group, n-butyl group, isobutyl group, etc.), acryloylmorpholine, N-methylol(meth)acrylamide, and N-phenyl(meth)acrylamide; vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyltrialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, (meth)acrylonitrile vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, and the compound represented by formula (A1-1) above. Among these, the compound represented by formula (A1-1) above is preferred as the other monomer in terms of achieving better effects of the present invention.

[0089] The polymer compound having an oxazoline group is preferably water-soluble in view of suitability for in-line coating.

[0090] The weight average molecular weight (Mw) of the polymer compound having an oxazoline group is not particularly limited, but is preferably 3,000 or more, more preferably 5,000 to 200,000, and even more preferably 7,000 to 150,000. The weight average molecular weight (Mw) is measured by the method described in the Examples section below.

[0091] The polymer compound having an oxazoline group may be a commercially available product, such as EPOCROS (registered trademark, the same applies hereinafter) K-2010E, EPOCROS K-2020E, EPOCROS K-2030E, EPOCROS WS-700, and EPOCROS WS-300 (all manufactured by Nippon Shokubai Co., Ltd.).

[0092] Isocyanate Compounds The isocyanate compounds are compounds having an isocyanate group or a blocked isocyanate group. The isocyanate compounds are preferably blocked isocyanate compounds (i.e., compounds having a blocked isocyanate group). Blocked isocyanate compounds are compounds in which the isocyanate group of a polyisocyanate is protected (i.e., blocked) with a blocking agent, and are included in the isocyanate compounds in this specification. Examples of blocking agents in blocked isocyanates include ester compounds, phenol compounds, alcohol compounds, oxime compounds, mercaptan compounds, lactam compounds, amine compounds, acid amide compounds, pyrazole compounds, triazole compounds, and bisulfite compounds.

[0093] Examples of ester compounds include malonic acid diesters such as dimethyl malonate and diethyl malonate, and acetoacetic acid esters such as methyl acetoacetate and ethyl acetoacetate. Among these, diethyl malonate is preferred due to its availability. Examples of phenolic compounds include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, and ethylphenol. Examples of alcohol compounds include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, propylene glycol monomethyl ether, ethylene glycol, and benzyl alcohol. Examples of oxime compounds include acetoxime, methyl ethyl ketone oxime, acetaldoxime, formaldoxime, diacetyl monooxime, and cyclohexane oxime, with acetoxime or methyl ethyl ketone oxime being preferred.

[0094] Examples of mercaptan compounds include butyl mercaptan and dodecyl mercaptan. Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam, with ε-caprolactam being preferred. Examples of amine compounds include diphenylaniline, aniline, and ethyleneimine. Examples of acid amide compounds include acetanilide and acetic acid amide. Examples of pyrazole compounds include methylpyrazole (e.g., 2-methylpyrazole, 3-methylpyrazole, 4-methylpyrazole), dimethylpyrazole (e.g., 2,4-dimethylpyrazole, 2,5-dimethylpyrazole, 3,4-dimethylpyrazole, 3,5-dimethylpyrazole), 4-nitro-3,5-dimethylpyrazole, and 4-bromo-3,5-dimethylpyrazole, with methylpyrazole or dimethylpyrazole being preferred. An example of the triazole compound is 1,2,4-triazole.

[0095] Examples of polyisocyanates whose isocyanate groups are protected by a blocking agent include polyfunctional polyisocyanates in the form of an adduct (also called an adduct body) obtained by adding 3 moles of diisocyanate to 1 mole of trimethylolpropane, a biuret (also called a biuret body) obtained by reacting 3 moles of diisocyanate with 1 mole of water, or an isocyanurate (also called an isocyanurate body) obtained by polymerizing 3 moles of diisocyanate. The polyisocyanate whose isocyanate groups are protected by a blocking agent may also be a polyurethane polyisocyanate obtained by reacting a polyisocyanate with a polyol (e.g., polyester polyol, polyether polyol, low molecular weight polyol). Examples of diisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic isocyanates. From the viewpoint of producing ceramic green sheets with reduced defects and without generating recessed defects on the peeled surface, aliphatic diisocyanates are preferred, and hexamethylene diisocyanate is more preferred.

[0096] Examples of aromatic diisocyanates include 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, tetraalkyldiphenylmethane diisocyanate, dialkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, polymeric diphenylmethane diisocyanate, tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate), 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,5-naphthylene diisocyanate, and naphthalene diisocyanate.

[0097] Examples of aliphatic diisocyanates that are examples of diisocyanates include hexamethylene diisocyanate, trimethylene diisocyanate, trimethylhexamethylene diisocyanate (2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate), lysine diisocyanate, xylylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and 1,5-pentamethylene diisocyanate.

[0098] Examples of diisocyanates, such as alicyclic isocyanates, include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,3- or 1,4-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, methylcyclohexane diisocyanate (-2,4- or -2,6-methylcyclohexane diisocyanate), and norbornane diisocyanate.

[0099] Among these, from the viewpoints of availability and ease of synthesis, an isocyanurate of hexamethylene diisocyanate, a biuret of hexamethylene diisocyanate, or an adduct of hexamethylene diisocyanate is preferred.

[0100] As the blocked isocyanate, commercially available products may be used, examples of which include 2554, 2507, and BI-301 from the Coronate series manufactured by Tosoh Corporation, SBN-70D, SBN-70P, MF-B60B, 17B-60P, TPA-B80E, and E402-B80B from the Duranate series manufactured by Asahi Kasei Corporation, and B-830, B-815N, B-820NSU, B-842N, B-846N, B870N, B874N, and B882N from the Takenate series manufactured by Mitsui Chemicals, Inc.

[0101] Carbodiimide Compounds Carbodiimide compounds are compounds having a carbodiimide group. Carbodiimide compounds can be synthesized by a conventionally known method. For example, a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and may be any of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Specific examples of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates are the same as the specific examples of diisocyanates described in the section on isocyanate compounds.

[0102] The carbodiimide equivalent (the mass [g] of the carbodiimide compound required to provide 1 mole of carbodiimide groups) is preferably 100 to 1,000 g / mol, more preferably 250 to 800 g / mol, and even more preferably 300 to 700 g / mol.

[0103] Melamine-based compounds In this specification, the melamine-based compounds include melamine and —NH ２ The melamine compound is not particularly limited, but may be obtained by condensing melamine with formaldehyde, and may be a melamine derivative in which the hydrogen atom of the -NH ２ One or more of the hydrogen atoms of the group is a methylol group (-CH ２ Examples of the melamine compounds include methylol melamine compounds substituted with hydroxyl groups (OH). Examples of the melamine compounds also include etherified methylol melamine compounds obtained by etherifying the above-mentioned methylol melamine with an alcohol compound through dehydration condensation. Specific examples of the melamine compounds include trimethylol melamine, hexamethylol melamine, trimethoxymethyl melamine, and hexamethoxymethyl melamine.

[0104] Epoxy Compounds There are no particular limitations on the epoxy compound as long as it is a compound having an epoxy group. It is preferable that the epoxy compound has two or more epoxy groups in the molecule. The epoxy group in the epoxy compound may be an epoxy group contained in a glycidyl group, or an epoxy group contained in an alicyclic epoxy group. An alicyclic epoxy group refers to, for example, a group such as a 3,4-epoxycyclohexyl group.

[0105] The epoxy compound may be a commercially available product, such as Cyclomer (registered trademark) M100, Celloxide (registered trademark) 2000, Celloxide (registered trademark) 2021P, 2081, Epolead (registered trademark) GT401, or EHPE (registered trademark) 3150 (manufactured by Daicel Corporation).

[0106] The epoxy-based compound is not particularly limited as long as it is a compound having an epoxy group, and may be a low molecular weight compound having a weight average molecular weight (Mw) of 1000 or less, or a high molecular weight compound having a weight average molecular weight (Mw) of more than 1000. However, a high molecular weight compound is preferred because it provides superior high-speed releasability for the sheet formed on the surface of the release layer.

[0107] When the epoxy compound is a low molecular weight compound, examples of the low molecular weight compound include "Denacol-EX-521" (trade name, polyglycerol polyglycidyl ether), "Denacol EX-512" (trade name, polyglycerol polyglycidyl ether), and "Denacol EX-830" (trade name, polyethylene glycol diglycidyl ether), all of which are manufactured by Nagase ChemteX Corporation.

[0108] When the epoxy compound is a polymer compound, it may be any polymer compound having an epoxy group, such as a polymer compound obtained by polymerizing a monomer having an epoxy group, and among these, an acrylic polymer having an epoxy group is preferred, and an acrylic polymer having an epoxy group and a polyalkylene oxide chain is more preferred. When the epoxy compound contains a polyalkylene oxide chain, the water solubility of the crosslinking agent B can be improved, and the in-line coating suitability is further improved.

[0109] Specific examples of the monomer having an epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, and among these, glycidyl acrylate and glycidyl methacrylate are preferred.

[0110] When the epoxy compound is an acrylic polymer containing an epoxy group and a polyalkylene oxide chain, the acrylic polymer may contain a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain. Specific examples of the (meth)acrylic acid ester containing a polyalkylene oxide chain are the same as the (meth)acrylic acid ester containing a polyalkylene oxide chain described above in connection with the polymer compound having an oxazoline group.

[0111] The polymer compound having an epoxy group may contain a constituent unit derived from a monomer other than the constituent unit derived from the compound having an epoxy group and the constituent unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain. Specific examples of the other monomers are the same as those described above for the polymer compound having an oxazoline group.

[0112] The weight average molecular weight (Mw) of the polymer compound having an epoxy group is not particularly limited, but is preferably 3,000 or more, more preferably 4,000 to 100,000, and even more preferably 5,000 to 50,000. The weight average molecular weight (Mw) is measured by the method described in the Examples section below.

[0113] - Preferred embodiment of crosslinking agent The crosslinking agent B is preferably an acrylic resin having a reactive group B on the side chain, from the viewpoint of providing superior high-speed releasability of the sheet formed on the surface of the release layer. Specific examples of acrylic resins having a reactive group B on the side chain include the above-mentioned polymeric compounds having an oxazoline group (specifically, copolymers containing a structural unit derived from the low molecular weight compound having the above-mentioned oxazoline group and a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain), and the above-mentioned polymeric compounds having an epoxy group (specifically, copolymers containing a structural unit derived from a compound having an epoxy group and a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain). Among them, the acrylic resin having a reactive group B on the side chain is preferably a polymeric compound having an oxazoline group, from the viewpoint of providing superior high-speed releasability of the sheet formed on the surface of the release layer.

[0114] Only one type of crosslinking agent B may be used, or two or more types may be used. When composition L contains crosslinking agent B, the content of crosslinking agent B is preferably 1 to 80 mass %, more preferably 1 to 70 mass %, still more preferably 1 to 60 mass %, and particularly preferably 10 to 50 mass %, relative to the total mass of the solid content of composition L, from the viewpoint of the reactivity of acrylic resin A.

[0115] The total content of the acrylic resin A and the crosslinking agent B is preferably 98 to 100 mass %, more preferably 98.5 to 100 mass %, based on the total mass of the solid content of the composition L, in order to obtain better effects of the present invention.

[0116] Solvent Composition L preferably contains a solvent. The solvent preferably contains water in terms of suitability for in-line application. Acrylic resin A may be dissolved or dispersed in composition L, but is preferably dissolved in terms of improving the smoothness of the release layer surface. The solvent may contain only water, or may contain water and an alcohol. Specific examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, propylene glycol, and propylene glycol monomethyl ether. Only one type of alcohol may be used, or two or more types may be used.

[0117] The water content is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 99% by mass, relative to the total mass of the solvent. When the solvent contains alcohol, the alcohol content is preferably 0.5 to 50% by mass, more preferably 0.5 to 30% by mass, preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass, relative to the total mass of the solvent. The solvent content is preferably 80 to 99.5% by mass, and more preferably 90 to 99.0% by mass, relative to the total mass of Composition L. That is, the total solid content in Composition L is preferably 0.5 to 20% by mass, and more preferably 1.0 to 10% by mass, relative to the total mass of Composition L.

[0118] Additives Composition L may contain additives. Examples of additives include light release additives and heavy release additives for adjusting the release force, surfactants, adhesion improvers, and antistatic agents. Of these, it is preferable that the release layer contains a surfactant. Specific examples of surfactants are the same as the specific examples of surfactants that can be contained in the protrusion-containing layer described below. When the release layer contains an additive, the content of the additive is preferably 0.1 to 3 mass %, and more preferably 0.1 to 2 mass %, relative to the total mass of the release layer.

[0119] Physical Properties of the Release Layer, etc. Thickness of the Release Layer The thickness of the release layer is preferably 450 nm or less, more preferably 200 nm or less, and even more preferably less than 150 nm, in order to improve the high-speed peelability of the sheet formed on the surface of the release layer.Furthermore, it is preferably 120 nm or less, and from the viewpoint of improving the appearance when the polyester film is rolled, it is more preferably less than 90 nm, particularly preferably 50 nm or less, and most preferably 40 nm or less.Furthermore, the thickness of the release layer is preferably 2 nm or more, and from the viewpoint of improving the high-speed peelability of the sheet formed on the surface of the release layer, it is more preferably 6 nm or more, more preferably 10 nm or more, and especially preferably 15 nm or more.The thickness of the release layer is determined by preparing a slice having a cross section perpendicular to the main surface of the polyester film and measuring it using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the arithmetic average value of the thicknesses of five locations on the release layer in the slice is taken.

[0120] Surface free energy The surface free energy of the release layer surface is 60 mJ / m ２ The peel strength is often less than 35 mJ / m, and the peel strength of the sheet formed on the release layer surface is excellent. ２ Preferably, 30 mJ / m or less ２ More preferably, 29 mJ / m or less ２ The surface free energy of the release layer surface is more preferably 17 mJ / m or less, in view of better coatability of a composition containing an organic solvent. ２ More than 20 mJ / m is preferable. ２ More preferably, 24 mJ / m or more ２ The method for measuring the surface free energy of the release layer surface is as described in the Examples section below.

[0121] Maximum protrusion height and average surface roughness: When the polyester film of the present invention is used to produce high-end ceramic green sheets, it is desirable that the release layer surface be smooth. From this perspective, the maximum protrusion height (Sp) of the release layer surface is preferably less than 35 nm, more preferably 30 nm or less, even more preferably 25 nm or less, and particularly preferably 20 nm or less. It is further preferably 15 nm or less, more preferably less than 15 nm, even more preferably 13 nm or less, and particularly preferably less than 10 nm. Furthermore, the maximum protrusion height of the release layer surface is often 1 nm or more. When a release layer is formed using the above-mentioned acrylic resin A, it is easy to adjust the maximum protrusion height (Sp) of the release layer surface to less than 35 nm. The average surface roughness (Sa) of the release layer 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 and average surface roughness of the release layer surface can be adjusted by selecting the type of polyester and additives constituting the polyester substrate so that the polyester substrate is substantially free of particles and forms a smooth film (for example, by using a polyester resin polymerized with a titanium compound or an aluminum compound). The method for measuring the maximum protrusion height and average surface roughness of the release layer surface is as described in the Examples section below.

[0122] In the polyester film of the present invention, it is preferable that the polyester substrate is substantially free of particles and the maximum protrusion height (Sp) of the release layer surface is less than 35 nm. This makes the release layer surface smoother, making the polyester film of the present invention suitable for use in the production of high-end ceramic green sheets. The meaning of the polyester substrate being substantially free of particles is as described above.

[0123] The content of silicon atom in the surface of release layer is preferably 1 atm% or more with respect to the total element content in the surface of release layer, and from the viewpoint that the releasability of the sheet formed on the surface of release layer is more excellent, more preferably 2 atm% or more, more preferably 3 atm% or more, particularly preferably 4 atm% or more.In addition, the content of silicon atom in the surface of release layer is preferably 25 atm% or less with respect to the total element content in the surface of release layer, preferably 20 atm% or less, more preferably 18 atm% or less, particularly preferably 15 atm% or less.The method for measuring the content of silicon atom in the surface of release layer is as described in the example section below.

[0124] The release layer may be provided directly on the surface of the polyester substrate or via an intermediate layer, but it is preferable to provide it directly on the surface of the polyester substrate from the viewpoint of superior productivity. In other words, it is preferable that the polyester substrate and the release layer are adjacent to each other.

[0125] - Crosslinked structure The release layer preferably has a crosslinked structure in terms of solvent resistance and high-speed peelability.For example, when forming a release layer using a composition L containing an acrylic resin A having a reactive group A and a crosslinking agent B having a reactive group B, the crosslinked structure is formed by reacting the reactive group A of the acrylic resin A with the reactive group B of the crosslinking agent B.That is, the crosslinked structure of the release layer is preferably a structure derived from the reactive group A of the acrylic resin A and the reactive group B of the crosslinking agent B (preferably, a structure formed by the reaction of the reactive group A of the acrylic resin A with the reactive group B of the crosslinking agent B).Thereby, a release layer with excellent curing properties can be obtained.

[0126] The release layer is preferably a layer formed by an addition reaction between a reactive group A of an acrylic resin A and a reactive group B of a crosslinking agent B, rather than a layer formed by chain polymerization of a monomer, in order to improve the releasability of the sheet formed on the surface of the release layer. This is because a release layer formed by chain polymerization of a monomer may undergo an insufficient chain reaction during production of the release layer, resulting in insufficient curing. For example, if residues of a polymerization initiator (e.g., a photopolymerization initiator and a thermal polymerization initiator) are contained in the release layer, it can be determined that the release layer is a layer formed by chain polymerization of a monomer.

[0127] <Protrusions and protrusion-containing layer> The polyester film of the present invention preferably has protrusions on the surface of the polyester film on the polyester substrate side (the surface of the polyester film opposite to the release surface, hereinafter also referred to as the "smooth surface"). When the polyester film of the present invention has protrusions on the smooth surface, the polyester film has excellent slip properties and can be improved in transportability.

[0128] The maximum protrusion height (Sp) of the smooth surface is preferably 0.02 μm or more, more preferably 0.03 μm or more, from the viewpoint of excellent transportability. Furthermore, the maximum protrusion height (Sp) of the smooth surface is preferably 1.0 μm or less, more preferably 0.6 μm or less, even more preferably 0.1 μm or less, and particularly preferably less than 0.06 μm. When the maximum protrusion height (Sp) of the smooth surface is within the above range, it is easy to control the dynamic friction coefficient to 0.2 or more when the release surface of the polyester film of the present invention is brought into contact with the smooth surface, and winding problems such as winding slippage are less likely to occur when the polyester film of the present invention is wound up. The maximum protrusion height (Sp) of the smooth surface can be measured in the same manner as the maximum protrusion height of the release layer, except that the smooth surface is measured.

[0129] The protrusions may be formed directly on the polyester substrate, or may be formed by a protrusion-containing layer that is a separate layer from the polyester substrate. That is, the polyester film of the present invention may have a protrusion-containing layer on the side of the polyester substrate opposite the release layer. In other words, the polyester film of the present invention may have a release layer, a polyester substrate, and a protrusion-containing layer in this order. The protrusion-containing layer refers to a layer having protrusions on at least one surface thereof. The protrusion-containing layer may be formed directly on the surface of the polyester substrate or via an intermediate layer, but is preferably formed directly on the surface of the polyester substrate from the viewpoint of superior productivity. That is, the polyester film of the present invention comprises a release layer, a polyester substrate, and a protrusion-containing layer, and it is preferred that the release layer and the polyester substrate are adjacent to each other, and that the polyester substrate and the protrusion-containing layer are adjacent to each other.

[0130] The maximum protrusion height (Sp) of the smooth surface can be adjusted, for example, by the following methods: (1) A particle-containing layer is formed on one surface of a polyester substrate, and the size and amount of particles contained in the particle-containing layer and the thickness of the particle-containing layer are adjusted. Methods for forming the particle-containing layer include forming a coating layer of a particle-containing composition and co-extruding a polyester melt with a second melt containing particles and a binder. (2) Particles are incorporated into the polyester substrate, and the size and amount of the particles are adjusted. (3) One surface of the polyester substrate is physically treated to make it rough. Examples of physical treatments include plasma treatment. The polyester film of the present invention has a polyester substrate and a particle-containing layer, and it is preferable that the exposed surface of the polyester substrate is a smooth surface and the exposed surface of the particle-containing layer is a smooth surface. This embodiment is preferably adjusted by method (1).

[0131] The method for forming the protrusion-containing layer is not particularly limited as long as protrusions are formed on at least one surface of the protrusion-containing layer. For example, a method may be used in which a layer containing particles (hereinafter also referred to as a "particle-containing layer") is provided as the protrusion-containing layer on the surface opposite to the release surface of the polyester film of the present invention. Hereinafter, the particle-containing layer will be described as an example of the protrusion-containing layer.

[0132] (Particle-Containing Layer) The particle-containing layer is not particularly limited as long as it contains particles. The particle-containing layer preferably contains a binder in addition to the particles. The particle-containing layer may further contain an additive.

[0133] The average particle size of the particles contained in the particle-containing layer is not particularly limited, but is preferably 1 to 1,000 nm, and more preferably 40 to 500 nm. Examples of the particles include inorganic and organic particles. 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). Examples of organic particles include resin particles. Examples of resins constituting the resin particles include acrylic resins such as polymethyl methacrylate resin (PMMA), polyester resins, silicone resins, styrene resins, urethane resins, and styrene-acrylic resins. The resin particles may or may not have a crosslinked structure. Specific examples include non-crosslinked acrylic resin particles, non-crosslinked styrene resin particles, crosslinked acrylic resin particles, crosslinked urethane resin particles, and divinylbenzene crosslinked particles. In this specification, "acrylic resin" refers to a resin containing a structural unit derived from acrylate or methacrylate.

[0134] The content of particles in the particle-containing layer is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, based on the total mass of the particle-containing layer, from the viewpoint of transportability.

[0135] By adjusting the type, particle size, content, etc. of particles in the particle-containing layer, the coefficient of dynamic friction between the release surface and the slippery surface (the surface of the particle-containing layer opposite the polyester substrate side) can be adjusted.

[0136] The binder that the particle-containing layer may contain is preferably a resin binder. Examples of resin binders include acrylic resins, urethane resins, polyester resins, and olefin resins. Non-polyester resins are preferred, specifically acrylic resins, urethane resins, or olefin resins. Known resins can be used as binders. The resin binder may also be an acid-modified resin. The binder contained in the particle-containing layer may have a crosslinked structure. In other words, the particle-containing layer may be a crosslinked film. The particle-containing layer may contain only one type of binder, or may contain two or more types of binders. The binder content 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 layer.

[0137] Examples of additives contained in the particle-containing layer include surfactants, waxes, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and antifungal agents.

[0138] The particle-containing layer preferably contains a surfactant in order to improve the surface smoothness. The surfactant is not particularly limited, and examples thereof include silicone-based surfactants, fluorine-based surfactants, and hydrocarbon-based surfactants. Fluorine-based surfactants (particularly, fluorine-based surfactants having a perfluoroalkyl group having 1 to 4 carbon atoms) or hydrocarbon-based surfactants are preferred. Only one type of surfactant may be used, or two or more types may be used in combination. The content of the surfactant is preferably 0.1 to 10% by mass, based on the total mass of the particle-containing layer, and more preferably 0.1 to 5% by mass in order to achieve better surface smoothness.

[0139] The thickness of the particle-containing layer is preferably 1 nm to 15 μm from the viewpoint of improving the smoothness of the release layer surface. When the particle-containing layer is formed by coating, the thickness is preferably 1 to 500 nm, more preferably 1 to 200 nm. When the particle-containing layer is formed by extrusion, the thickness is often greater than 500 nm, and is preferably 1 to 15 μm, more preferably 1 to 10 μm. The thickness of the particle-containing layer is determined by preparing a slice having a cross section perpendicular to the main surface of the polyester film and measuring the thickness of the particle-containing layer at five points on the slice using a scanning electron microscope (SEM).

[0140] The preferred range of the maximum protrusion height (Sp) of the protrusion-containing layer is the same as the maximum protrusion height (Sp) shown above for the protrusion height. The surface average roughness (Sa) of the protrusion-containing layer is preferably 5 nm or less, more preferably 3 nm or less. The lower limit may be 0 nm or more, but from the viewpoint of suppressing transfer marks and improving the smoothness of the release layer surface, the surface average roughness (Sa) of the protrusion-containing layer is preferably 2 to 3 nm. The maximum protrusion height and surface average roughness of the protrusion-containing layer can be measured in the same manner as the maximum protrusion height and surface average roughness of the release layer, except that the protrusion-containing layer is measured.

[0141] <Characteristics of Polyester Film> The polyester film of the present invention preferably exhibits various characteristics, which will now be described.

[0142] The thickness of the polyester film of the present invention is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, particularly preferably 40 μm or less, and most preferably 35 μm or less, from the viewpoint of excellent cost efficiency. There is no particular lower limit on the thickness, but from the viewpoint of improved strength and improved processability, it is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 10 μm or more, particularly preferably 18 μm or more, and most preferably 20 μm or more. The thickness of the polyester film of the present invention is measured at five different arbitrarily selected locations using a stylus film thickness meter, and the arithmetic mean of the measured values ​​obtained is defined as the thickness.

[0143] The dynamic friction coefficient of the polyester film of the present invention is preferably 0.2 or more. The dynamic friction coefficient of the polyester film of the present invention refers to the friction coefficient of both surfaces of the polyester film of the present invention, more specifically, the dynamic friction coefficient between the release layer surface and the surface of the polyester film of the present invention opposite the release layer surface (a slippery surface, for example, the surface of the protrusion-containing layer opposite the polyester substrate side). When the dynamic friction coefficient is 0.2 or more, the polyester film of the present invention is less likely to slip when wound into a roll. Furthermore, the dynamic friction coefficient is preferably less than 1.0. When the dynamic friction coefficient is less than 1.0, the polyester film of the present invention is less likely to block when wound into a roll. The dynamic friction coefficient can be measured in accordance with ASTM D 1894-95. The detailed procedure for measuring the dynamic friction coefficient follows the method described in the Examples below.

[0144] The heat shrinkage of the polyester film of the present invention, measured in an environment at 150°C, in both the machine direction and width direction is preferably -1.0 to 3.0%, more preferably -0.5 to 2.0%, and even more preferably 0 to 1.5%. When the heat shrinkage of the polyester film of the present invention is within the above range, the dimensional stability of the ceramic green sheet formed on the release layer surface of the polyester film of the present invention, as well as the dimensional stability when the ceramic green sheet is peeled from the polyester film of the present invention and then laminated, is good, thereby reducing the risk of failure of electronic components. The method for measuring each of the above heat shrinkage rates is described in the Examples below. The heat shrinkage rate of the polyester film of the present invention can be adjusted by selecting the heating or cooling conditions during production of the polyester film of the present invention. More specifically, it can be adjusted by changing at least one of the conditions of the heat setting step, heat relaxation step, and cooling step described below.

[0145] <Applications> The polyester film of the present invention can be used in various applications. For example, the polyester film of the present invention is preferably used as a release film (carrier film) for producing ceramic green sheets. The ceramic green sheets produced using the polyester film of the present invention can be suitably used for producing ceramic capacitors, which require multilayer internal electrodes in response to miniaturization and increased capacitance.

[0146] The method for producing a ceramic green sheet using the polyester film of the present invention is not particularly limited and can be carried out by a known method. Examples of methods for producing a ceramic green sheet include a method in which a prepared ceramic slurry is applied to the surface of the release layer of the polyester film of the present invention and the solvent contained in the ceramic slurry is dried and removed. The method for applying the ceramic slurry is not particularly limited, and known methods can be used, such as a method in which a ceramic slurry obtained by dispersing ceramic powder and a binder in a solvent is applied by a reverse roll method and the solvent is removed by heating and drying. The binder is not particularly limited, and examples thereof include polyvinyl butyral. The solvent is also not particularly limited, and examples thereof include ethanol and toluene.

[0147] The produced ceramic green sheet is used to manufacture a ceramic capacitor. Known methods can be used to manufacture a ceramic capacitor using the ceramic green sheet, including, for example, the following method. First, internal electrodes are provided on a laminate of the polyester film of the present invention and ceramic green sheets by coating or printing a conductive paste. Next, the polyester film of the present invention is removed from the laminate, and ceramic green sheets with internal electrodes are sequentially stacked. The resulting laminate is pressed to produce an intermediate laminate. The intermediate laminate is cut into a desired shape and then fired to obtain a ceramic element. Next, external electrodes electrically connected to the internal electrodes are formed on each of the two end faces of the fired intermediate laminate using a conductive paste such as silver, thereby obtaining a ceramic capacitor.

[0148] The polyester film of the present invention can also be used as a protective film for dry film resists, a film for sheet molding such as decorative layers and resin sheets, a release film for process manufacturing such as semiconductor manufacturing processes, battery manufacturing processes, and polarizing plate manufacturing processes, and a separator for adhesive films for labels, medical and office supplies, etc.

[0149] <Method for Producing a Polyester Film> The method for producing a polyester film of the present invention includes a step of in-line coating a release layer-forming composition and a step of curing the coated layer. The polyester film includes a release layer and a polyester substrate, and the release layer-forming composition includes an acrylic resin A having a siloxane bond. An example of the method for producing a polyester film of the present invention includes a step of in-line coating the composition L on at least one surface of the polyester substrate. Here, the in-line coating method in the present invention refers to coating the composition L on at least one surface of the polyester substrate during the polyester film production process. When the polyester film is produced using the stretching machine shown in Figure 2 below, an example of a method for forming a release layer by the in-line coating method is described below. First, before the polyester substrate is transported to the stretching section 20, the composition L is applied to the surface of the polyester substrate to obtain a polyester substrate with a coating film. Here, the polyester substrate to which the composition L is applied may be an unstretched polyester substrate or a longitudinally stretched polyester substrate. Next, the polyester substrate with the coating film is transported to the stretching section 20, where the polyester substrate with the coating film is stretched laterally while the coating film is dried. In this manner, a stretched polyester substrate with a release layer is obtained. Note that if the polyester substrate in the polyester substrate with the coating film transported to the stretching section 20 is unstretched, it may be subjected to longitudinal stretching in the stretching section 20 before transverse stretching.

[0150] In one preferred embodiment of the method for producing a polyester film of the present invention, a polyester resin is melt-extruded to prepare an unstretched polyester substrate, the unstretched polyester substrate is then longitudinally stretched, composition L is applied to one side of the longitudinally stretched polyester substrate, and the resulting polyester substrate is then transversely stretched to produce a polyester film. Furthermore, when composition L contains an acrylic resin A having a reactive group A and a crosslinking agent B having a reactive group B, it is preferred that drying of the coating film and a crosslinking reaction are simultaneously carried out when transverse stretching is performed in stretching section 20 as described above. Hereinafter, each step that may be included in the method for producing a polyester film of the present invention will be described.

[0151] (Stretching step) The present production method preferably includes a stretching step. In the stretching step, biaxial stretching is preferably performed. The biaxial stretching may be simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed simultaneously, or may be sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed in two or more stages. Examples of sequential biaxial stretching include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, longitudinal stretching → longitudinal stretching → transverse stretching, and transverse stretching → longitudinal stretching, with longitudinal stretching → transverse stretching being preferred. One suitable embodiment of the stretching step is an embodiment including the longitudinal stretching step and transverse stretching step described below.

[0152] - Stretching Machine The device used for biaxial stretching is not particularly limited, and a known stretching machine can be used. An example of the stretching machine will be described below with reference to the drawings.

[0153] FIG. 2 is a plan view showing an example of a stretching machine used in the production of polyester films. The stretching machine 100 shown in FIG. 2 includes a pair of annular rails 60a and 60b and gripping members 2A to 2L attached to each annular rail and movable along the rails. The annular rails 60a and 60b are arranged symmetrically with respect to each other, sandwiching the film 200. The stretching machine 100 can stretch the film 200 in the width direction by gripping the film 200 with the gripping members 2A to 2L and moving the gripping members 2A to 2L along the rails. Furthermore, the stretching machine 100 shown in FIG. 2 includes a clip closer 3, a support member 4 that supports the clip closer 3, and a clip opener 5.

[0154] The stretching machine 100 has zones consisting of, in order from the upstream side in the conveying direction, a preheating zone 10, a stretching zone 20, a heat setting zone 30, a heat relaxing zone 40, and a cooling zone 50. The zones in the stretching machine 100 are separated by windshield curtains, and the temperature in each zone can be adjusted individually by hot air or the like.

[0155] The preheating section 10 is an area where the film 200 is preheated.

[0156] The stretching section 20 is a region where the preheated film 200 is stretched by applying tension in the direction of the arrow TD (width direction), which is perpendicular to the direction of the arrow MD (longitudinal direction). As shown in Figure 2, in the stretching section 20, the film 200 is stretched from width L0 to width L1.

[0157] The heat fixing section 30 is an area where the tensioned film 200 is heated and heat fixed while still being tensioned.

[0158] The thermal relaxation section 40 is a region where the tension of the heat-set film 200 is thermally relaxed by heating the heat-set film 200. As shown in Fig. 2, in the thermal relaxation section 40, the film 200 is reduced (relaxed) from width L1 to width L2.

[0159] Cooling section 50 is an area for cooling thermally relaxed film 200. By cooling film 200, the shape of film 200 can be fixed. In Fig. 2, the width of film 200 fed into cooling section 50 is L2, and the width of film 200 fed out of cooling section 50 is L3.

[0160] Gripping members 2A, 2B, 2E, 2F, 2I, and 2J are attached to the circular rail 60a and are movable along the circular rail 60a. Gripping members 2C, 2D, 2G, 2H, 2K, and 2L are attached to the circular rail 60b and are movable along the circular rail 60b. Gripping members 2A, 2B, 2E, 2F, 2I, and 2J grip one end of the film 200 in the direction of arrow TD. Gripping members 2C, 2D, 2G, 2H, 2K, and 2L grip the other end of the film 200 in the direction of arrow TD. Gripping members 2A to 2L are often referred to as chucks, clips, or the like. Gripping members 2A, 2B, 2E, 2F, 2I, and 2J move counterclockwise along the circular rail 60a. The gripping members 2C, 2D, 2G, 2H, 2K, and 2L move clockwise along the circular rail 60b.

[0161] Gripping members 2A-2D move along annular rail 60a or 60b while gripping the end of film 200 in preheating section 10, passing through stretching section 20, heat-setting section 30, and heat-relaxing section 40, and then proceeding to cooling section 50. Next, gripping members 2A and 2B, and gripping members 2C and 2D, in that order in the conveying direction, release the end of film 200 at the end downstream of cooling section 50 in the direction of arrow MD (e.g., grip release points P and Q in FIG. 2), and then move further along annular rail 60a or 60b, returning to preheating section 10. In the above process, as film 200 moves in the direction of arrow MD, it is preheated in preheating section 10, stretched in stretching section 20, heat-set in heat-setting section 30, heat-relaxed in heat-relaxing section 40, and cooled in cooling section 50, and then transversely stretched.

[0162] The transport speed of film 200 can be adjusted by adjusting the movement speed of gripping members 2A to 2L. Furthermore, the movement speed of gripping members 2A to 2L can be changed independently of each other.

[0163] As described above, the stretching machine 100 enables transverse stretching in which the film 200 is stretched in the direction of the arrow TD in the stretching section 20. On the other hand, the stretching machine 100 can also stretch the film 200 in the direction of the arrow MD by changing the moving speed of the gripping members 2A to 2L. In other words, simultaneous biaxial stretching can also be performed using the stretching machine 100.

[0164] In addition to the gripping members 2A to 2L, the stretching machine 100 may further include other gripping members (not shown) to support the film 200.

[0165] Longitudinal Stretching Step The method for producing a polyester film of the present invention preferably includes a longitudinal stretching step in which an unstretched polyester substrate is longitudinally stretched. Longitudinal stretching can be performed, for example, by conveying the unstretched polyester substrate in the machine direction while applying tension between two or more pairs of stretching rolls arranged in the conveying direction. The heating temperature in the longitudinal stretching step is preferably 70 to 120°C, more preferably 80 to 110°C, and even more preferably 85 to 100°C. The stretch ratio in the longitudinal stretching step is appropriately set depending on the application, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 4.0 times.

[0166] Transverse Stretching Step The polyester film manufacturing method of the present invention preferably includes a transverse stretching step in which the polyester substrate is transversely stretched. Transverse stretching refers to a process in which the polyester substrate is stretched in the width direction. For example, when using the stretching machine 100 shown in FIG. 2, transverse stretching is performed in the stretching section 20. The heating temperature in the transverse stretching step is preferably 100 to 140°C, more preferably 110 to 135°C, and even more preferably 115 to 130°C. The stretch ratio in the width direction of the polyester substrate in the transverse stretching step (transverse stretching ratio) is not particularly limited, but is preferably larger than the stretch ratio in the longitudinal stretching step. The stretch ratio in the transverse stretching step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, and even more preferably 3.5 to 4.5 times.

[0167] (In-line Coating Process) In the polyester film manufacturing method of the present invention, a release layer is formed by in-line coating of a release layer-forming composition. Specifically, composition L is in-line coated on at least one surface of a polyester substrate. In-line coating is preferably a method of coating composition L on one surface of a polyester substrate that has been longitudinally stretched. In the in-line coating process, for example, when using the stretching machine 100 shown in FIG. 2, the polyester substrate coated with composition L (polyester substrate with a coating film) is transversely stretched in the stretching section 20. At this time, the coating film is cured simultaneously with the transverse stretching. Here, "curing" refers to drying of the coating film, but it is also preferable that curing by a crosslinking reaction proceed. In other words, when composition L contains an acrylic resin A having a reactive group A and a crosslinking agent B having a reactive group B, it is also preferable that the reaction between the acrylic resin A and the crosslinking agent B proceed. In particular, it is more preferable that curing proceed in which the reactive group A of the acrylic resin A reacts with the reactive group B of the crosslinking agent B to form a crosslinked structure. In order to form a coating film into a sufficiently hardened film (release layer), it is preferable that drying and crosslinking reaction proceed simultaneously. Furthermore, since the crosslinking reaction is carried out in the stretching section 20 of FIG. 2, it is preferable that sufficient crosslinking occurs at the heating temperature of the transverse stretching step described above. In order to achieve superior high-speed releasability, it is preferable to select reactive groups A and B that are sufficiently crosslinked at the heating temperature of the transverse stretching step. The coating method for composition L 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.

[0168] When the protrusion-containing layer is formed by coating, for example, the protrusion-containing layer can be provided by coating a particle-containing layer-forming composition on the surface of the polyester substrate opposite to the surface on which composition L is applied. The particle-containing layer-forming composition may be any composition containing the components contained in the particle-containing layer described above. When the protrusion-containing layer is formed by extrusion, for example, a second melt containing particles and a binder is co-extruded together with a polyester melt, and composition L can be applied in-line to the surface of the polyester substrate opposite to the particle-containing layer in a laminate consisting of the particle-containing layer and the polyester substrate.

[0169] The method for producing a polyester film of the present invention may include, in addition to the longitudinal stretching step, the coating film forming step, the release layer forming step, and the transverse stretching step, other steps. The method for producing a polyester film of the present invention may include, for example, one or more steps selected from the group consisting of a heat setting step of heating and heat setting a biaxially stretched polyester substrate, a heat relaxing step of heating the polyester substrate heat-set in the heat setting step at a temperature lower than that in the heat setting step and heat relaxing the polyester substrate, a cooling step of cooling the polyester substrate heat-relaxed in the heat relaxing step, and an expansion step of expanding the heat-relaxed polyester substrate in the width direction during the cooling step.

[0170] Although the polyester film is produced by in-line coating of composition L onto one surface of a polyester substrate between the longitudinal stretching step and the transverse stretching step in the above-described method, the method for producing the present film is not limited to the above-described method. For example, composition L may be coated onto an unstretched polyester substrate, followed by stretching.

[0171] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0172] [Production of Polyester Film] Example 1 An unstretched polyester substrate was produced with reference to the conditions described in paragraphs

[0160] to

[0169] of WO 2020 / 158316. The obtained unstretched polyester substrate was longitudinally stretched. The following protrusion-containing layer-forming composition X1 was applied to one side of the longitudinally stretched polyester substrate, and the following composition L1 was applied to the opposite side. Each of the formed coating films was dried with hot air at 100°C to form a protrusion-containing layer and a release layer. That is, protrusion-containing layer-forming composition X1 and composition L1 were applied in-line. At this time, the application amounts of protrusion-containing layer-forming composition X1 and composition L1 were adjusted so that the thickness of the protrusion-containing layer was 60 nm and the thickness of the release layer was 15 nm. When preparing each composition, the components were mixed and then filtered using a depth-pleated filter (SHPH010, manufactured by Roki Techno Co., Ltd.) with a pore size of 1 μm, followed by membrane degassing (2x6 Radial Flow Superphobic, manufactured by Polypore Co., Ltd.). The resulting coated film was stretched transversely to produce a biaxially oriented polyester film with a width of 1500 mm, which was then wound up at 7000 m intervals without knurling. The thickness of the produced biaxially oriented polyester film (polyester film of Example 1) was 31 μm. The biaxially oriented polyester film (polyester film of Example 1) had an intrinsic viscosity of 0.63 dl / g and a terminal COOH content in the range of 2.6 to 2.8 eq / ton. The polyester substrate in the polyester film was substantially free of particles. Furthermore, the biaxially stretched polyester film (polyester film of Example 1) had an Sb content of 0 to 1 mass ppm, a Ti content of 7 ppm, an Mg content of 75 ppm, and a P content of 65 ppm, based on the total mass of the biaxially stretched polyester film (polyester film of Example 1). The measurements were carried out using an ICP-MS analyzer "Agilent 7800 ICP-MS" (manufactured by Agilent Technologies).

[0173] (Protrusion-Containing Layer-Forming Composition X1) The components shown below were mixed, and then the above-mentioned filtration treatment and membrane degassing were carried out to obtain protrusion-containing layer-forming composition X1. - Aqueous solution of aqueous primer (Hydran AP-40N, manufactured by DIC Corporation) with a solids concentration of 35% by mass: 112.1 parts by mass - Water-diluted solution of anionic hydrocarbon surfactant (Rapisol (registered trademark) A-90, manufactured by NOF Corporation) with a solids concentration of 1% by mass: 55.7 parts by mass - Aqueous dispersion of colloidal silica (Snowtex ZL, manufactured by Nissan Chemical Industries, Ltd.) with a solids concentration of 40.5% by mass: 11.1 parts by mass - Water: 821.1 parts by mass

[0174] (Method for preparing composition L1) The components shown below were mixed, and then subjected to the above-mentioned filtration and membrane degassing to obtain composition L1 (composition L1 for forming a release layer). Acrylic resin A1 (solid content concentration 20% by mass): 82.5 parts by mass (16.5 parts by mass in terms of solid content) Crosslinker B1 (aqueous solution containing an oxazoline compound, an acrylic polymer with 2-isopropenyl-2-oxazoline-derived structural units / methoxypolyethylene glycol acrylate-derived structural units / ethyl acrylate-derived structural units / methyl methacrylate-derived structural units = 48 / 10 / 2 / 40 (molar ratio), solid content concentration 25% by mass aqueous solution, weight average molecular weight Mw: 23,000, oxazoline value = 4.8) (referred to as "B1 (oxazoline)" in the table): 44 parts by mass (11 parts by mass in terms of solid content) Water: 873.5 parts by mass

[0175] - Method for synthesizing acrylic resin A1 1-propanol (92.83 g) was placed in a 1-liter three-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 80°C under a nitrogen stream. Mixed solution 1, which was a mixture of 2.16 g of V-601 (a radical polymerization initiator; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 30.94 g of 1-propanol, 20.00 g of methacrylic acid (MAA), methacrylic-modified silicone oil (CH ２ =C(CH ３ )-C(O)O-L １１ -[Si(CH ３ ) ２ -O] ｍ -SiR １ (CH ３ ) ２L in the formula １１ The definition of is defined as R in the above formula (A1-1). １１ and L １１ The definitions of m and R in the formula are the same as those of １ The definition of -[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ m and R in the group represented by １ The definition is the same as that of the above. Molecular weight: approximately 1000. In the tables below, this is referred to as "SiMA-1." Mixed solution 2, which was a mixture of 70.00 g of methyl methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "M-90G"; in the tables below, this is referred to as "M-90G"), 10.00 g of methoxypolyethylene glycol methacrylate, 0.66 g of dodecyl mercaptan, and 30.94 g of 1-propanol, was added dropwise at a constant rate under conditions such that the dropwise addition was completed within 3 hours. After the dropwise addition of the mixed solution was completed, a mixed solution of 0.32 g of V-601 and 2 g of 1-propanol was added to the resulting reaction mixture, and the mixture was heated and stirred for 6 hours. To the resulting reaction mixture was added 49.39 g of ethanol, and then 16.57 g of dimethylaminoethanol (neutralizing agent) (DMAE) was added dropwise using a dropping funnel, and water was added to adjust the solid content to 20%, thereby obtaining a solution of acrylic resin A1.

[0176] Examples 2 to 50 Compositions L2 to L41 were prepared by changing the components as shown in the table below instead of composition L1 used to form the release layer, and biaxially oriented polyester films (polyester films) of Examples 2 to 50 were obtained. The amount of each component in compositions L2 to L41 was adjusted so that the solids concentration was the same as that of composition L1. Of the components used in preparing compositions L2 to L41, the components other than those used in composition L1 are as follows. The notation in parentheses at the end of each component is the abbreviation for each component listed in the table below.

[0177] (Monomers used in the synthesis of acrylic resin A) 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TrisMA) 3-[tris(trimethylsilyloxy)silyl]propyl acrylate (TrisA) Methacrylic-modified silicone oil (CH ２ =C(CH ３ )-C(O)O-L １１ -[Si(CH ３ ) ２ -O] ｍ -SiR １ (CH ３ ) ２ L in the formula １１ The definition of is defined as R in the above formula (A1-1). １１ and L １１ The definitions of m and R in the formula are the same as those of １ The definition of -[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ m and R in the group represented by １ The definition is the same as above. Mixture of molecular weight 700 to 3200, molecular weight is about 2000.) (SiMA-2) Methacrylic modified silicone oil (CH ２ =C(CH ３ )-C(O)O-C ３ H ６ -[Si(CH ３ ) ２ -O] ｍ -Si(CH ３ ) ２ (C ４ H ９ The definition of m in the formula is the same as that of —[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ The definition of m is the same as that of the group represented by the formula (1). Molecular weight: about 5000.) (SiMA-3) Methacrylic-modified silicone oil (CH ２ =C(CH ３ )-C(O)O-C ３ H ６ -[Si(CH ３) ２ -O] ｍ -Si(CH ３ ) ２ (C ４ H ９ The definition of m in the formula is the same as that of —[Si(R ３ ) ２ -O] ｍ -SiR １ (R ２ ) ２ The definition of m is the same as that of the group represented by the formula: Molecular weight: about 1,000. ) (SiMA-4) Acrylic acid (AA) 2-methacryloyloxyethyl succinate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Ester HO-MS") (HO-MS) Hydroxyethyl methacrylate (HEMA) Methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Ester M-40G") (M-40G) Methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Ester M-230G") (M-230G) 2-Methoxyethyl acrylate (MEA) Diacetone acrylamide (DAAM) Ethylene glycol monoacetoacetate monomethacrylate (EGMM) t-Butyl acrylate (tBA) 2-Hydroxy-3-phenoxypropyl acrylate (HPPA) 4-Hydroxybutyl acrylate (HBA) Phenoxyethyl acrylate (PEA) Benzyl methacrylate (BnMA) Cyclohexyl acrylate (CyHA) Cyclohexyl methacrylate (CyHMA) Tetrahydrofurfuryl methacrylate (THFMA) Styrene (St) n-Butyl acrylate (nBA)

[0178] The molecular weight of Monomer A1 was measured by MALDI-MS (matrix-assisted laser desorption / ionization mass spectrometry) as follows. Specifically, 10 μL of a diluted monomer solution (1 mg / mL, THF (tetrahydrofuran) solution) was mixed with 10 μL of DHB (2,5-dihydroxybenzoic acid) (10 mg / mL, THF solution) and 5 μL of NaTFA (sodium trifluoroacetate) (1 mg / mL, THF solution) to obtain a mixed solution. 1 μL of the resulting mixed solution was subjected to MS spectrum measurement using a mass spectrometer (Ultraflextreme manufactured by Bruker) employing MALDI-MS as the measurement principle. The measurement was performed with n=2. The peak with the strongest intensity in the obtained MS spectrum was taken as the molecular weight.

[0179] (Neutralizing agent) Diisopropylethylamine (DIPEA) 28% aqueous ammonia (NH3aq)

[0180] (Crosslinking Agents) Crosslinking agent B2 (aqueous solution containing an oxazoline compound, an acrylic polymer having a molar ratio of 2-isopropenyl-2-oxazoline-derived structural units / ethyl acrylate-derived structural units / methyl methacrylate-derived structural units of 75 / 5 / 20, an aqueous solution with a solids concentration of 10% by mass, a weight-average molecular weight Mw: 60,000, and an oxazoline value of 7.5) (B2 (oxazoline)). Crosslinking agent B3 (an acrylic polymer having an oxazoline group synthesized by the method described below (a copolymer represented by formula (B3) described below), a weight-average molecular weight Mw: 14,200) (B3 (oxazoline)). Crosslinking agent B4 (an acrylic polymer having an oxazoline group synthesized by the method described below (a copolymer represented by formula (B4) described below), a weight-average molecular weight Mw: 12,300) (B4 (oxazoline)). Crosslinking agent B5 (an acrylic polymer having epoxy groups synthesized by the method described below (a copolymer represented by formula (B5) described below), weight average molecular weight Mw: 12,200) (B5 (epoxy)) Crosslinking agent B6 (an acrylic polymer having epoxy groups synthesized by the method described below (a copolymer represented by formula (B6) described below), weight average molecular weight Mw: 12,400) (B6 (epoxy)) Crosslinking agent B7 (an aqueous solution containing a carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Inc., an aqueous solution with a solids content of 40% by mass) (B7 (carbodiimide)) Crosslinking agent B8 (Denacol EX-521 (water-soluble), manufactured by Nagase ChemteX Corporation, molecular weight 334.37) (B8 (epoxy, oligomer))

[0181] The weight average molecular weight Mw of the crosslinking agent B was determined in the same manner as the weight average molecular weight Mw of the acrylic resin A1 described below.

[0182] Synthesis Method of Crosslinking Agent B3 1-propanol (54.41 g) was placed in a 500-milliliter three-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 80° C. under a nitrogen stream. To this, mixed solution 1, which was a mixture of 0.62 g of V-601 (radical polymerization initiator; manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 15.54 g of 1-propanol, and mixed solution 2, which was a mixture of 20.00 g of 2-isopropenyl-2-oxazoline, 10.00 g of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TrisMA), 20.00 g of methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "M-40G"), 0.88 g of dodecyl mercaptan, and 7.77 g of 1-propanol, were each added dropwise at a constant rate under conditions such that the dropwise addition was completed within 3 hours. After the dropwise addition of the mixed solution was completed, a mixed solution of 0.60 g of V-601 and 1 g of 1-propanol was added to the resulting reaction mixture, and the mixture was heated and stirred for 5 hours to obtain a solution of crosslinker B3. The solid content of B3 was 40% by mass.

[0183]

[0184] Crosslinking agent B3 has a mass ratio of the structural units, from left to right, of 20:40:40.

[0185] Synthesis of Crosslinker B4: A solution of crosslinker B4 was obtained in the same manner as for synthesis of crosslinker B3, except that the amounts of the compounds added were adjusted so that the mass ratios of the structural units were as shown below. The solid content of B4 was 40 mass%.

[0186]

[0187] Crosslinking agent B4 has a mass ratio of the structural units, from left to right, of 40:20:40.

[0188] Synthesis Method of Crosslinker B5 Ethanol (66.29 g) was charged into a 500 mL three-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and the temperature was raised to 75°C under a nitrogen stream. Mixed Solution 1, which was a mixture of 0.34 g of V-601 (radical polymerization initiator; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 18.94 g of ethanol, and Mixed Solution 2, which was a mixture of 10.00 g of glycidyl methacrylate, 10.00 g of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TrisMA), 30.00 g of methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "M-90G"), 0.49 g of dodecyl mercaptan, and 9.47 g of ethanol, were added dropwise at a constant rate under conditions such that the dropwise addition was completed within 3 hours. After the dropwise addition of the mixed solution was completed, a mixed solution of 0.20 g of V-601 and 1 g of ethanol was added to the obtained reaction mixture, and the mixture was heated and stirred for 5 hours to obtain a solution of crosslinking agent B5. The solid content concentration of B5 was 35% by mass.

[0189]

[0190] The numerical values ​​in parentheses for the structural units in formula (B5) indicate the mass proportion of each structural unit.

[0191] Synthesis of Crosslinker B6: A solution of crosslinker B6 was obtained in the same manner as for synthesis of crosslinker B5, except that the amount of each compound added was adjusted so that the mass ratio of each structural unit was as shown below. The solid content concentration of B6 was 35 mass%.

[0192]

[0193] The numerical values ​​in parentheses for each structural unit in formula (B6) indicate the mass proportion of each structural unit.

[0194] <Comparative Example 1> A biaxially oriented polyester film (polyester film) of Comparative Example 1 was obtained in the same manner as in Example 1, except that the following composition LX1 (composition LX1 for forming a release layer) was used instead of composition L1. Here, composition LX1 contains silicone (referred to as "CX1" in the table below) and does not contain the above-mentioned acrylic resin A having a siloxane bond. (Composition LX1 for forming a release layer) Emulsion (I) and emulsion (II) were prepared according to the following procedure. (A) 50 parts by mass of a vinyl group-containing polydimethylsiloxane in which both ends are each blocked with a dimethylvinylsilyl group, (B) 0.5 parts by mass of a platinum-vinylsiloxane complex solution having a platinum content of 1% by mass, (C) 0.11 parts by mass of 1-ethynyl-1-cyclohexanol (manufactured by Nissin Chemical Industry Co., Ltd.), (D) 6.6 parts by mass of a nonionic surfactant (manufactured by Sanyo Chemical Industries, Ltd., "Naroacty CL-95"), and (E) 44 parts by mass of purified water were mixed and stirred to prepare emulsion (I). The platinum content was 100 ppm by mass relative to the mass of polydimethylsiloxane (A). Furthermore, 35 parts by mass of (F) a methylhydrogenpolysiloxane having SiH groups in its side chains and both molecular chain terminals blocked with trimethylsiloxy groups, 5 parts by mass of (G) a nonionic surfactant ("Naroacty CL-95" manufactured by Sanyo Chemical Industries, Ltd.), and 60 parts by mass of (H) purified water were mixed and stirred to prepare emulsion (II). Next, emulsion (I) and emulsion (II) were mixed and further diluted with purified water to a solids concentration of 40% by mass, thereby obtaining a composition. When preparing the composition, the mixing ratio of emulsion (I) and emulsion (II) was adjusted so that the ratio of the total number of moles of SiH groups in component (F) to the total number of moles of alkenyl groups in component (A) was 2.9. To 92.5 parts by mass of the above composition (37 parts by mass in terms of solid content), 5 parts by mass of a silane coupling agent (KBE-403, manufactured by Shin-Etsu Chemical Co., Ltd.) and 2 parts by mass of a nonionic surfactant ("Naloacty CL-95" manufactured by Sanyo Chemical Industries, Ltd.) were added and mixed, and the mixture was further diluted with purified water to a solid content concentration of 1% by mass, thereby obtaining composition LX1.

[0195] <Comparative Example 2> A biaxially oriented polyester film (polyester film) of Comparative Example 2 was obtained in the same manner as in Example 1, except that the following composition LX2 (composition LX2 for forming a release layer) was used instead of composition L1. Here, composition LX2 is the composition of the following composition used in Example 1 of WO 2021 / 192896. The acrylic resin CX2 contained in composition LX2 is the acrylic resin A-1 used in Example 1 of WO 2021 / 192896, and is an acrylic resin synthesized using 100 parts by mass of hydroxyethyl methacrylate (HEMA), 8 parts by mass of methacrylic acid (MAA), 33 parts by mass of stearyl methacrylate (SMA), and 3 parts by mass of methyl methacrylate (MMA). Acrylic resin CX2 does not fall under the category of acrylic resin A having a siloxane bond. Further, the oxazoline-based crosslinking agent BX2 (oxazoline) contained in composition LX2 is the oxazoline-based crosslinking agent C-1 used in Example 1 of WO 2021 / 192896. Further, the polyether-modified polydimethylsiloxane DX1 contained in composition LX2 is the additive E-1 used in Example 1 of WO 2021 / 192896. (Composition LX2) Water: 457.6 parts by mass Isopropyl alcohol: 282.0 parts by mass Acrylic resin CX2 (solid content concentration 20% by mass): 140.0 parts by mass Oxazoline-based crosslinking agent BX2 (solid content concentration 10% by mass): 120.0 parts by mass Polyether-modified polydimethylsiloxane DX1, 67 Additive (solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.): 0.4 parts by mass

[0196] [Physical Properties of Acrylic Resin A] <Acid Value and Hydroxyl Value> Table 1 shows the theoretical values ​​of the acid value and hydroxyl value of Acrylic Resin A calculated from the amounts of monomers charged in the production of Acrylic Resin A. When the acid value of Acrylic Resin A was measured by the following measurement method, the measured value was almost the same as the theoretical value described above.

[0197] (Method for Measuring Acid Value) 1.0 g of sample (acrylic resin A) was weighed into a 200 mL beaker, and the weight was recorded. 95 mL of a mixed solvent of THF (tetrahydrofuran) / water (5 / 1 (volume ratio)) was added to dissolve the sample. This solution (sample solution) was subjected to potentiometric titration (automatic titration apparatus AT-510, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) with 0.1 N aqueous sodium hydroxide while stirring with a magnetic stirrer, and the titration volume was determined from the endpoint (performed with N=2). A blank test was conducted in the same manner, and the acid value was calculated using the following formula: Acid value (mmol / g) = 0.1 (mol / L) × f × (titration volume of sample solution (mL) - titration volume of blank (mL)) × weighed value of sample (g) × solids concentration (%) × 0.01 In the formula, f represents the titrant factor of the aqueous sodium hydroxide solution.

[0198] <Water Solubility> 2 g (solid content 0.4 g) of a composition consisting of acrylic resin A or other polymer C used in preparing each release layer-forming composition in the Examples and Comparative Examples, and a mixed solution of 1-propanol, ethanol, and water (1-propanol:ethanol:water=41:12:47 (mass ratio)), and 30 g of water at 25°C were mixed, and the mixed solution at 25°C was stirred for 10 minutes at 60 rpm with a mix rotor. After stirring, the mixed solution was evaluated for water solubility based on the following evaluation criteria. If the evaluation result is B or higher, the water solubility is excellent. A: When the mixed solution is visually observed after stirring, it is colorless and transparent. B: When the mixed solution is visually observed after stirring, it is cloudy but uniform. C: Precipitation or separation into two layers has occurred.

[0199] <Weight average molecular weight Mw of acrylic resin A1> The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC). Measurement by gel permeation chromatography (GPC) was performed using a measuring device, HLC (registered trademark) -8320GPC (manufactured by Tosoh Corporation), and two TSKgel (registered trademark) Super Multipore HZ-M (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) columns, and THF (tetrahydrofuran) as the eluent. The measurement was performed using a sample concentration of 0.3% by mass, a flow rate of 0.35 mL / min, a sample injection amount of 10 μL, and a measurement temperature of 40 ° C., using an RI (Refractive Index) detector. The calibration curve was prepared from 12 samples of "Standard Sample TSK Standard, Polystyrene" manufactured by Tosoh Corporation: "F-128", "F-80", "F-40", "F-20", "F-10", "F-4", "F-2", "F-1", "A-5000", "A-2500", "A-1000", and "A-500".

[0200] [Film Properties] <Surface Free Energy> The surface free energy of the release layer surface was measured by the following method. Using a contact angle meter (DROPMASTER-501, manufactured by Kyowa Interface Science Co., Ltd.), a droplet was dropped onto the release layer surface of a polyester film at 25°C, and the contact angle was measured 1 second after the droplet adhered to the release layer surface. 2 μL of purified water, 1 μL of methylene iodide, and 1 μL of ethylene glycol were used as droplets, and the surface free energy was calculated from the measured contact angles using the Kitazaki-Hata method.

[0201] <Maximum protrusion height Sp, average surface roughness Sa> The maximum protrusion height Sp and average surface roughness Sa were measured for both surfaces of the biaxially oriented polyester films produced in the Examples and Comparative Examples using the following method. Both surfaces of the biaxially oriented polyester film were measured using an optical interferometer (Vertscan 3300G Lite, manufactured by Hitachi High-Tech Corporation) under the following conditions, and then analyzed using the built-in data analysis software (VS-Measure5) to determine the maximum protrusion height Sp and average surface roughness Sa of the release layer surface. For the measurement of the maximum protrusion height Sp, the maximum value of the measurements obtained from five measurements at different measurement positions was used, and for the measurement of the average surface roughness Sa, the average value of the measurements obtained from five measurements at different measurement positions was used. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x magnification Measurement area: 186 μm × 155 μm The maximum protrusion height Sp of the release layer surface of the polyester film measured using the above method is shown in Table 3 below. The surface average roughness Sa of the release layer surface was in the range of 0 to 2 nm in all Examples. Furthermore, when the maximum protrusion height Sp and surface average roughness Sa of the protrusion-containing layer surface of the polyester film were measured using the method described above, Sp was in the range of 10 to 60 nm and Sa was in the range of 2 to 3 nm in all Examples.

[0202] <Surface Si Ratio> For the biaxially oriented polyester films produced in the Examples and Comparative Examples, the total element content present on the outermost surface of the release layer was measured under the following conditions using the following analyzer based on XPS (X-ray photoelectron spectroscopy). The silicon atom content was calculated when the total element content was taken as 100 atm%. The silicon atom content was calculated to one decimal place, and the average value of the values ​​measured with n = 3 was calculated and rounded off. The obtained value was taken as the silicon atom content (atm%) on the surface of the release layer. Note that when the value was below the detection limit, it was indicated as "N.D." in the table. (Measurement conditions) Analysis equipment: X-ray photoelectron spectrometer, manufactured by Ulvac-PHI X-ray source: monochromated Al-Kα Measurement elements: carbon (C), nitrogen (N), oxygen (O), silicon (Si), sulfur (S) Measurement area: 300 μm × 300 μm Number of measurements: n = 3 Sputtering irradiation ions: argon Energy: 94 eV (0.1 eV step)

[0203] [Performance] <Coating Defects> In the examples and comparative examples, the biaxially oriented polyester film was cut into a length of 2 m, and the surface of the release layer was visually observed to evaluate coating defects (cissing) according to the following criteria: A: Less than 3 coating defects (cissing) B: 3 to less than 10 coating defects (cissing) C: 10 or more coating defects (cissing)

[0204] <Roll Appearance> The appearance of the rolled polyester film obtained by winding the biaxially oriented polyester film in the Examples and Comparative Examples was visually observed and evaluated according to the following criteria: A: No wrinkles were observed immediately after winding, and no wrinkles were observed even after one week of storage. B: No wrinkles were observed immediately after winding, but wrinkles were observed after one week of storage. C: Wrinkles were observed immediately after winding.

[0205] [Film Properties] <Heat Shrinkage> The biaxially oriented polyester film produced in each example was cut to a dimension of 100 mm in the width direction and 100 mm in the direction perpendicular to the width direction to obtain a square sample. The longitudinal and width dimensions before heating were measured using a measuring microscope (product name "MM-800", manufactured by Nikon Corporation), and the arithmetic mean value was designated Ls. The sample was then placed on a sample holder and placed in a thermostatic chamber set to 150°C. After 30 minutes had passed since placement, the sample was removed, and the longitudinal and width dimensions after heating were measured using the measuring microscope, and the arithmetic mean value was designated Ll. The heat shrinkage of the biaxially oriented polyester film was calculated using the following formula (1). A positive value for the heat shrinkage indicates shrinkage, and a negative value indicates expansion. Heat shrinkage rate (%)={(Ls−Ll) / Ls}×100 (1) The heat shrinkage rates of the biaxially oriented polyester films produced in the examples were all in the range of 0.95 to 1.15%.

[0206] <Dynamic Friction Coefficient> For the biaxially oriented polyester films produced in each example, the coefficient of friction between the release surface (surface of the release layer) and the protrusion surface (surface of the protrusion-containing layer) was measured in accordance with ASTM D 1894-95. As a measurement condition, the distance over which the flat indenter was moved in the longitudinal direction of the fixed test specimen was set to 130 mm. The force (test force) required to move the flat indenter was recorded using a measuring instrument, and a plot was created with the movement distance (unit: mm) on the horizontal axis and the test force (unit: N) on the vertical axis. The dynamic friction coefficient was calculated from the measured values ​​of the test force plotted above. The above operation was repeated five times, and the average value of the dynamic friction coefficients for each of the five measurements was calculated. The average value of the dynamic friction coefficient is shown in the table below as the dynamic friction coefficient. As a result, the dynamic friction coefficients of the biaxially oriented polyester films produced in each example were all in the range of 0.3 to 0.5.

[0207] [Method for producing ceramic green sheets and evaluation] <Preparation of ceramic slurry> Barium titanate powder (BaTiO ３A mixed solution was prepared by mixing 100 parts by mass of a binder (manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 8 parts by mass of a polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC (registered trademark) B.K BM-2") as a binder, 4 parts by mass of dioctyl phthalate (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate, Deer Grade 1) as a plasticizer, and 135 parts by mass of a mixed solution of toluene and ethanol (mass ratio 5:5). Zirconia beads were added to the mixed solution, and the mixture was dispersed in the barium titanate powder mixed solution using a ball mill to prepare a dispersion. The zirconia beads were removed from the resulting dispersion to obtain a ceramic slurry.

[0208] <Coatability of Ceramic Slurry (Cleaning)> The ceramic slurry was applied to the surface of the release layer of a polyester film using an applicator so that the thickness of the dried ceramic green sheets would be 1.0 μm, 0.5 μm, or 0.2 μm, respectively. After drying at 80° C. for 1 minute, a ceramic green sheet was formed on the surface of the release layer of the polyester film. The surface condition of the ceramic green sheet was visually inspected, and the coatability was evaluated according to the following criteria. A: Coating was successful at both 1.0 μm and 0.5 μm without cissing or the like. Furthermore, coating was successful at 0.2 μm without cissing or the like. B: Coating was successful at both 1.0 μm and 0.5 μm without cissing or the like. However, cissing occurred in some areas at 0.2 μm. C: Coating was successful at 1.0 μm without cissing or the like. However, cissing occurred in some areas at 0.2 μm and 0.5 μm.

[0209] <Low-Speed ​​Removal> Ceramic slurry was applied to the release layer surface of a polyester film using an applicator so that the thickness of the dried ceramic green sheet would be 0.2 μm. After drying at 90°C for 1 minute, a ceramic green sheet was formed on the release layer surface of the polyester film. Using a peel tester (VPA-2S, manufactured by Kyowa Interface Science Co., Ltd., load cell load 1N), the ceramic green sheet formed on the release layer surface was peeled at a peel angle of 90°, a peel temperature of 25°C, and a peel speed of 0.3 m / min. The peel direction was as follows: double-sided adhesive tape (No. 535A, manufactured by Nitto Denko Corporation) was attached to a stainless steel (SUS) plate attached to the peel tester, and the polyester film with the ceramic green sheet was fixed on the double-sided tape by adhering the ceramic green sheet side to the tape. The polyester film side was then pulled to release the sheet. The average peel force value for peel distances of 20 mm to 50 mm was calculated from the obtained measurements, and this value was used as the peel force. The measurement was performed five times, and the average peel strength was used as the peel strength of the ceramic green sheet. Based on the peel strength of the ceramic green sheet, the low-speed peelability was evaluated according to the following criteria: AA: Peel strength ≦ 0.10 N / 25 mm; A: 0.10 N / 25 mm < peel strength ≦ 0.15 N / 25 mm; B: 0.15 N / 25 mm < peel strength ≦ 0.25 N / 25 mm; C: 0.25 N / 25 mm < peel strength ≦ 0.35 N / 25 mm; D: Peel strength exceeds 0.35 N / 25 mm, or the ceramic green sheet breaks during peeling.

[0210] <High-Speed ​​Removal Property> The high-speed removability was evaluated based on the peel strength of the ceramic green sheet in the same manner as in the evaluation method for low-speed removability, except that the peel speed was changed from 0.3 m / min to 3 m / min, and according to the following criteria: AA: Peel strength ≦ 0.10 N / 25 mm A: 0.10 N / 25 mm < peel strength ≦ 0.15 N / 25 mm B: 0.15 N / 25 mm < peel strength ≦ 0.25 N / 25 mm C: 0.25 N / 25 mm < peel strength ≦ 0.35 N / 25 mm D: Peel strength exceeds 0.35 N / 25 mm, or the ceramic green sheet breaks during peeling.

[0211] The measurement results of the above physical properties and the evaluation results of the performance are shown in the table below. In the table below, monomers A1 to A4 and neutralizing agent are components used in the synthesis of the acrylic resin. Monomers A1 to A3 are defined as above, and monomer A4 refers to a monomer that does not fall under the category of monomers A1 to A3. In addition, in the table below, A / B means "content of acrylic resin A / content of crosslinking agent B" in the composition for forming a release layer. In addition, in the table below, A / C / B / D means "content of acrylic resin A / content of other polymer C / content of crosslinking agent B / content of other additive D" in the composition for forming a release layer.

[0212] The ratio (mass ratio) of the constituent units of each acrylic resin A was measured by proton nuclear magnetic resonance ( １ The ratio of the amount of the monomers charged was determined by H-NMR, and was found to be equivalent to the ratio of the amount of the monomers charged. All of the release layers in the examples were formed from a composition containing an acrylic resin A having structural units derived from monomer A2 and a crosslinking agent B, and since heating was performed during the formation of the release layer, it can be said that they have a crosslinked structure.

[0213]

[0214]

[0215]

[0216] As shown in the table above, when a release layer formed using a release layer-forming composition containing an acrylic resin A having a siloxane bond was used, it was shown that the coating property of the composition containing an organic solvent (ceramic slurry) was excellent, and the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was also excellent (Examples). Comparison of Examples 1 to 50 showed that when an acrylic resin A having a structural unit derived from monomer A3 with a ClogP value of 0.8 or more was used, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was even better (Examples 7, 9 to 11, 13 to 19). Comparison of Examples 2 and 20 to 28 showed that when the thickness of the release layer was 10 nm or more, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was even better (Examples 2, 21 to 28). Furthermore, comparison of Examples 2 and 20 to 28 showed that when the thickness of the release layer was less than 90 nm, the appearance (roll appearance) of the polyester film when rolled was even better (Examples 2, 20 to 27). Comparison of Examples 1, 29 to 31 showed that when the weight average molecular weight (Mw) of acrylic resin A was 60,000 or less, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Examples 1, 29 to 30). Comparison of Examples 1, 32 showed that when the surface Si ratio (the content of silicon atoms on the surface of the release layer relative to the total element content on the surface of the release layer) was 2 atm% or more, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Example 1). Comparison of Examples 2, 33 to 36 showed that when acrylic resin A with an acid value of 0.5 to 4.5 mmol / g was used, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Examples 2, 33 to 35). Comparison of Examples 1, 37 to 40 showed that when an acrylic resin A containing a constituent unit derived from monomer A1, which is an acrylic monomer having a siloxane bond, and in which the molecular weight of monomer A1 is 100 to 4000, was used, the high-speed peelability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Examples 1, 37).Comparison of Examples 1, 43 to 47, and 49 to 50 showed that when an acrylic resin having a reactive group B in the side chain was used as crosslinking agent B, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Examples 1, 43 to 47). In particular, when reactive group B was an oxazoline group, the high-speed releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was superior (Examples 1, 43 to 45).

[0217] In contrast, when a release layer-forming composition containing an acrylic resin A having a siloxane bond was not used, it was shown that at least one of the coatability of a composition containing an organic solvent (ceramic slurry) and the releasability of the sheet (ceramic green sheet) formed on the surface of the release layer was inferior (Comparative Examples 1 to 2).

[0218] 2A to 2L: Gripping member 3: Clip closer 4: Support member 5: Clip opener 10: Preheating section 20: Stretching section 30: Heat setting section 40: Heat relaxation section 50: Cooling section 60a, 60b: Circular rail 100: Stretching machine 200: Film 300 Polyester film 310 Polyester base material 320 Release layer 321 One side 322 Other side (release layer surface, release surface) P, Q: Gripping release point MD: Machine direction (longitudinal direction) TD: Width direction L0, L1, L2, L3: Film width

Claims

1. A polyester film comprising a release layer and a polyester substrate, wherein the release layer is a layer formed by curing an in-line applied composition for forming a release layer, and the composition for forming a release layer comprises an acrylic resin A having a siloxane bond.

2. The polyester film according to claim 1, wherein the acrylic resin A contains a structural unit derived from a monomer A1 which is an acrylic monomer having a siloxane bond, and the molecular weight of the monomer A1 is 100 to 4,000.

3. The polyester film according to claim 1 or 2, wherein the content of silicon atoms on the surface of the release layer is 2 atm % or more based on the total element content on the surface of the release layer.

4. The polyester film according to claim 1 or 2, wherein the polyester substrate is substantially free of particles and the release layer has a maximum peak height (Sp) of less than 35 nm on the surface.

5. The polyester film according to claim 1 or 2, wherein the release layer forming composition contains a crosslinking agent B, the acrylic resin A has a reactive group A containing at least one selected from the group consisting of a carboxy group, a carboxylic anhydride group, a carboxylate group, and a hydroxyl group, and the crosslinking agent B has a reactive group B capable of reacting with the reactive group A.

6. The polyester film according to claim 5, wherein the reactive group B comprises at least one selected from the group consisting of an oxazoline group, a carbodiimide group, an epoxy group, a methylol group, an isocyanate group, and a blocked isocyanate group.

7. The polyester film according to claim 5, wherein the crosslinking agent B is an acrylic resin having the reactive group B in a side chain.

8. The polyester film according to claim 5, wherein the total content of the acrylic resin A and the crosslinking agent B is 98 to 100% by mass based on the total mass of the solid content of the composition for forming the release layer.

9. The polyester film according to claim 1 or 2, wherein the acid value of the acrylic resin A is 0.5 to 4.5 mmol / g.

10. The polyester film of claim 1 or 2, wherein the release layer has a thickness of less than 90 nm.

11. The polyester film according to claim 1 or 2, wherein the acrylic resin A further contains a structural unit derived from a monomer A3 having a ClogP value of 0.8 or more.

12. The polyester film according to claim 1 or 2, which is used for producing a ceramic green sheet.

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