Polyester film, method for producing polyester film, and release agent

Abstract

The present invention addresses the problem of providing a polyester film that has excellent coatability with respect to a composition containing an organic solvent, and is excellent in terms of the peelability of a sheet formed on a surface of a release layer. The present invention also addresses the problem of providing a method for producing a polyester film, and a release agent. The polyester film according to the present invention comprises a release layer and a polyester base material, wherein the release layer contains an acrylic resin having a group represented by -Si(R)3, and has a thickness of 450 nm or less. In -Si(R)3, the multiple R's each independently represent an alkyl group.

Description

Polyester film, polyester film manufacturing method, and release agent

[0001] The present invention relates to a polyester film, a method for producing a polyester film, and a release agent.

[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. Specifically, a release layer is provided on a polyester substrate, various components are produced in contact with the release layer, and then the components are released. For example, Patent Document 1 discloses a release film having a release layer formed from a composition containing a specific acrylic resin, etc.

[0004] International Publication No. 2021 / 192896

[0005] When a polyester film is used as a release film, a composition containing an organic solvent (e.g., a ceramic slurry) is applied to the release layer surface of the polyester film, and a sheet (e.g., a ceramic green sheet) is formed on the release layer surface. In this case, the release layer of the polyester film is required to have excellent coatability with the composition containing an organic solvent. It is also required to have excellent releasability of the sheet formed on the release layer surface. The present inventors have studied the release film described in Patent Document 1 and found that although the coatability of the composition containing an organic solvent is excellent, the releasability of the sheet formed on the release layer surface is insufficient, and there is room for improvement.

[0006] Therefore, an object of the present invention is to provide a polyester film that has excellent coatability with a composition containing an organic solvent and excellent releasability of a sheet formed on the release layer surface. Another object of the present invention is to provide a method for producing a polyester film and a release agent.

[0007] 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.

[0008] [1] A polyester film comprising a release layer and a polyester substrate, wherein the release layer is -Si(R) ３ wherein the thickness of the release layer is 450 nm or less, and the polyester film contains an acrylic resin having a group represented by the formula: ３ [2] In the above formula, each of the plurality of R independently represents an alkyl group. ３ The polyester film according to [1], wherein the polyester film has a group represented by —O—Si(R) ３ In the formula, each of the R's independently represents an alkyl group. [3] The acrylic resin is -Si[-O-Si(R) ３ ] ３ and a group represented by —[Si(R) ２ —O]—Si(R) ３

[0023] The polyester film according to [1] or [2], wherein the polyester film has at least one of the groups represented by —Si[—O—Si(R) ３ ] ３ , and -[Si(R) ２ —O]—Si(R) ３ In the formula (I), each of the R's independently represents an alkyl group. [4] The polyester film according to any one of [1] to [3], wherein the release layer has a maximum protrusion height Sp of less than 35 nm on its surface. [5] The polyester film according to any one of [1] to [4], wherein the release layer has a maximum protrusion height Sp of less than 15 nm on its surface. [6] The polyester film according to any one of [1] to [4], wherein the release layer has a surface free energy of less than 17 mJ / m ２ 30mJ / m or more ２[7] The polyester film according to any one of [1] to [5], wherein the release layer has a thickness of 120 nm or less. [8] The polyester film according to any one of [1] to [7], wherein the polyester substrate is substantially free of particles. [9] The polyester film according to any one of [1] to [8], wherein the release layer has a crosslinked structure.

[10] The polyester film according to any one of [1] to [9], wherein the polyester film is used for producing a ceramic green sheet.

[11] A method for producing a polyester film comprising a release layer and a polyester substrate, the method comprising the steps of: ３ and a solvent containing water, wherein the —Si(R) group is an acrylic resin having the formula: ３

[12] The method for producing a polyester film according to

[11] , wherein the coating step provides a polyester substrate with a coating film, and the method further comprises a step of stretching the polyester substrate with a coating film.

[13] The method for producing a polyester film according to

[11] , wherein the acrylic resin is —O—Si(R) ３ The method for producing a polyester film according to

[11] or

[12] , wherein the polyester film has a group represented by —O—Si(R) ３ In the formula (1), each of the R's independently represents an alkyl group.

[14] The method for producing a polyester film according to any one of the above items (11) to (13), wherein the acrylic resin has at least one selected from the group consisting of an acid group, a hydroxyl group, and a polyalkylene oxide chain.

[15] The method for producing a polyester film according to any one of the above items (11) to (14), wherein the release layer-forming composition contains a crosslinking agent, the acrylic resin has a reactive group capable of reacting with the crosslinking agent, and the method includes a step of reacting the acrylic resin with the crosslinking agent.

[16] A release agent comprising a water-soluble acrylic resin having a structural unit represented by the formula (1) described below and a structural unit derived from acrylic acid or a salt thereof, or methacrylic acid or a salt thereof. In the formula (1) described below, R１１ is a hydrogen atom or a methyl group, and L １１ represents an alkylene group which may have a substituent, and Rh represents —Si(R) ３ wherein each of the plurality of R's is independently an alkyl group.

[17] The release agent according to

[16] , wherein the water-soluble acrylic resin has an acid value of 0.3 to 6.0 mmol / g.

[18] The release agent according to

[16] or

[17] , wherein the water-soluble acrylic resin further has a structural unit derived from an acrylic acid ester containing a polyalkylene oxide chain or a methacrylic acid ester containing a polyalkylene oxide chain.

[0009] According to the present invention, there is provided a polyester film having excellent coatability with a composition containing an organic solvent and excellent releasability of a sheet formed on the release layer surface. The present invention also provides a method for producing a polyester film and a release agent.

[0010] 1 is a side view schematically illustrating an example of a polyester film of the present invention.

[0011] 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.

[0012] 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.

[0013] 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°.

[0014] 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.

[0015] 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.

[0016] [Polyester Film] The polyester film of the present invention includes a release layer and a polyester substrate. Fig. 1 is a side view schematically showing an example of the polyester film of the present invention. The polyester film 1 includes a polyester substrate 10 and a release layer 20. The polyester substrate 10 is disposed on one side 21 of the release layer 20. The other side 22 of the release layer 20 is the surface opposite to the side of the release layer 20 on which the polyester substrate 10 is disposed (i.e., one side 21), and may be referred to as the release layer surface or release surface.

[0017] Hereinafter, preferred embodiments of the polyester film of the present invention will be described in detail.

[0018] [First embodiment] A first embodiment of the polyester film of the present invention is a polyester film comprising a release layer and a polyester substrate, wherein the release layer is -Si(R) ３ In this embodiment, the release layer contains an acrylic resin having a group represented by the formula: ３ In the formula (I), each of the plurality of R's independently represents an alkyl group.

[0019] The polyester film of the first embodiment has excellent coatability with compositions containing organic solvents and excellent releasability of the sheet formed on the release layer surface. The details of the reason for this are not clear, but it is generally assumed as follows. The -Si(R) in the acrylic resin of the release layer ３ It is presumed that the group represented by -Si(R) can reduce the surface free energy on the surface of the release layer, thereby improving the releasability of the sheet (particularly the ceramic green sheet) formed on the surface of the release layer. ３ It is presumed that the presence of a group represented by the formula (I) in the molecule of the acrylic resin adjusts the surface free energy of the release layer within an appropriate range, thereby improving the coatability of a composition containing an organic solvent (e.g., a ceramic slurry). The following describes the components contained in the polyester film of the present invention. Hereinafter, the polyester film of the first embodiment will also be referred to as "Film 1."

[0020] <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.

[0021] 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.

[0022] Preferably, the polyester substrate is substantially free of inorganic particles. "Substantially free of inorganic particles" means that when the polyester substrate is quantitatively analyzed for elements derived from inorganic particles by fluorescent X-ray analysis, the content of inorganic particles is 50 mass ppm or less, preferably 10 mass ppm or less, and more preferably below the detection limit, relative to the total mass of the polyester substrate. This is because, even if inorganic particles are not actively added to the polyester substrate, contaminants derived from foreign matter, raw material resins, or dirt attached to the line or equipment in the polyester substrate manufacturing process may peel off and be mixed into the polyester substrate. Here, examples of inorganic particles include inorganic particles that may be contained in the particle-containing layer (protrusion-containing layer) described below.

[0023] 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.

[0024] (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.

[0025] The intrinsic viscosity of the polyester resin is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g. The melting point (Tm) of the polyester resin is preferably 220 to 270°C, and more preferably 245 to 265°C. The glass transition temperature (Tg) of the polyester resin is preferably 65 to 90°C, and more preferably 70 to 85°C.

[0026] 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.

[0027] -Catalyst- The catalyst used in the production of the polyester resin 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 cause foreign matter or voids in the polyester substrate. Only one 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.

[0028] 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. Titanium compounds described in paragraphs

[0049] to

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

[0029] 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.

[0030] -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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] -Diol Compound- Examples of the diol compound include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0035] 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.

[0036] -End-capping agent- In the production of the polyester resin, an end-capping agent may be used as needed. By using the end-capping agent, a structure derived from the end-capping agent is introduced into the end of the polyester resin. The end-capping agent is not limited, and known end-capping agents can be used. Examples of the end-capping agent include oxazoline compounds, carbodiimide compounds, and epoxy compounds. For end-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.

[0037] -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.

[0038] As a method for synthesizing the 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.

[0039] 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.

[0040] 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.

[0041] The polyester substrate may contain components other than the polyester resin (for example, a catalyst, unreacted raw material components, particles, water, etc.).

[0042] 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).

[0043] <Release Layer> The release layer is a layer disposed on one side of the polyester substrate. When the film 1 is used as a release film, various members are produced in contact with the release layer, and then the members are released. In the film 1, the release layer is a -Si(R) ３ The term "-Si(R)" is used hereinafter to refer to an acrylic resin having a group represented by the formula: ３ The acrylic resin having a group represented by the formula (I) is also referred to as a “specific acrylic resin.” The components contained in the release layer and the components that may be contained therein will be described below.

[0044] (Specific Acrylic Resin) The release layer contains a specific acrylic resin. The specific acrylic resin is a —Si(R) ３ The (meth)acrylic acid ester is a resin having a group represented by the following formula (I): and containing a structural unit derived from a (meth)acrylic acid ester. Note that the (meth)acrylic acid ester represents a concept that includes both a methacrylic acid ester and an acrylic acid ester.

[0045] -Si(R) ３ In the formula (I), each of the multiple R's 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, a 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, or an ethyl group, a propyl group, a 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 multiple R's may be the same or different.

[0046] -Si(R) contained in specific acrylic resin ３ The group represented by —O—Si(R) is more preferably —O—Si(R) ３ It is preferable that the group is a partial structure of a group represented by -Si[-O-Si(R) ３ ]３ and a group represented by —[Si(R) ２ —O]—Si(R) ３ It is more preferable that R is at least one partial structure of a group represented by the following formula: The definition of R in each group is as described above.

[0047] The specific acrylic resin is preferably —Si(R) ３ It is preferable that the copolymer has a structural unit derived from a (meth)acrylic acid ester having a group represented by the formula (1), and it is more preferable that the copolymer has a structural unit represented by the formula (1).

[0048]

[0049] In formula (1), R １１ is a hydrogen atom or a methyl group.

[0050] In formula (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, an alkoxy group (preferably having 1 to 5 carbon atoms), and a carboxy group. １１ is preferably an alkylene group having no substituent, more preferably a propylene group, an ethylene group, or a methylene group.

[0051] In formula (1), Rh is —Si(R) ３ is a substituent having one or more groups represented by -Si(R) ３ The definition of R in is as described above. Specific examples of the substituent in Rh include -Si(R Ａ ) ｎ (R Ｂ ) ３－ｎ , and -Si(R Ｃ ) ２ -[O-Si(R Ｃ ) ２ ]ｍ —O—Si(R Ｄ ) ３ -Si(R Ａ ) ｎ (R Ｂ ) ３－ｎ In this case, R Ａ is the above-mentioned —O—Si(R) ３ is a group represented by R Ｂ is a hydrogen atom, a hydroxyl group, or an alkyl group, and n is 2 or 3 (preferably 3). Ｂ is an alkyl group, R Ｂ Specific examples and preferred embodiments of the alkyl group in the formula (I) are the above-mentioned —Si(R) ３ The same applies to R in the group represented by the formula: Ａ may be the same or different. Ｃ ) ２ -[O-Si(R Ｃ ) ２ ] ｍ —O—Si(R Ｄ ) ３ In the above, a plurality of R Ｃ are each independently an alkyl group, and multiple R Ｄ are each independently an alkyl group, and m represents a number from 1 to 150. Ｃ and R Ｄ Specific examples and preferred embodiments of the above-mentioned -Si(R) ３ It is the same as R in the group represented by the formula:

[0052] Specific examples of monomers from which the structural unit represented by formula (1) is derived include 3-[tris(trimethylsilyloxy)silyl]propyl (meth)acrylate, (trimethoxysilyl)methyl (meth)acrylate, (triethoxysilyl)methyl (meth)acrylate, (tri-n-butoxysilyl)methyl (meth)acrylate, 3-(trimethoxysilyl)propyl (meth)acrylate, (tricyclohexylsilyl)methyl (meth)acrylate, 3-(triethoxysilyl)propyl (meth)acrylate, 3-(tri-n-butoxysilyl)propyl (meth)acrylate, 3-[diethoxy(methyl)silyl]propyl (meth)acrylate, 3-[dimethoxy(methyl)silyl]propyl (meth)acrylate, 3-(triethoxysilyl)propyl (meth)acrylate, and organosilyl group-containing monomers such as (meth)acrylate 3-(tri-n-butoxysilyl)propyl, (meth)acrylate 3-(ethoxydimethylsilyl)propyl, (meth)acrylate 3-(methoxydimethylsilyl)propyl, 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.). The term "(meth)acrylic acid" refers to a concept that includes both methacrylic acid and acrylic acid.

[0053] When the specific acrylic resin has a structural unit represented by formula (1), the content of the structural unit represented by formula (1) 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 specific acrylic resin. If the content of the structural unit represented by formula (1) is 20% by mass or more, the release properties of the sheet formed on the release layer surface are better. Furthermore, if the content of the structural unit represented by formula (1) is 80% by mass or less, the coatability of a composition containing an organic solvent is better.

[0054] The specific acrylic resin preferably contains a structural unit derived from (meth)acrylic acid or a salt thereof. This provides the resin with better water solubility and curability. (Meth)acrylic acid refers to a concept including methacrylic acid and acrylic acid. Here, in the structural unit derived from (meth)acrylic acid or a salt thereof, a carboxy group or a carboxylic acid salt contained in the (meth)acrylic acid or a salt thereof may react with a crosslinking agent described below to form a crosslinked structure. Examples of the carboxylic acid salt include alkali metal salts of a carboxy group, organic amine salts of a carboxy group, and ammonium salts of a carboxy group.

[0055] When the specific acrylic resin has structural units derived from (meth)acrylic acid or a salt thereof, the content of the structural units derived from (meth)acrylic acid or a salt thereof is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, relative to the total structural units (100% by mass) of the specific acrylic resin. If the content of structural units derived from (meth)acrylic acid or a salt thereof is 10% by mass or more, the water solubility and curability of the resin are superior. Furthermore, if the content of structural units derived from (meth)acrylic acid or a salt thereof is 30% by mass or less, the releasability of the release film is superior.

[0056] The specific acrylic resin preferably has a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain, which can improve the smoothness of the release layer surface.

[0057] 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.

[0058] 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.

[0059] When the specific acrylic resin has structural units derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain, the content of the structural units derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain is preferably 5 to 80% by mass, more preferably 7 to 70% by mass, and even more preferably 10 to 60% by mass, relative to the total structural units (100% by mass) contained in the specific acrylic resin. If the content of the structural units derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain is 10% by mass or more, the water solubility of the resin will be superior. Furthermore, if the content of the structural units derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain is 60% by mass or less, the solubility of the resin will be superior.

[0060] The specific acrylic resin may have a structural unit derived from a monomer other than the above structural units. Specific examples of the other monomers include: 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; hydroxyl group-containing monomers such as 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; aromatic group-containing monomers such as benzyl (meth)acrylate, styrene, and α-methylstyrene; Carboxy group-containing monomers such as itaconic acid, maleic acid, fumaric acid, crotonic acid, and styrenesulfonic acid, and salts thereof (for example, sodium salts, potassium salts, ammonium salts, and tertiary amine salts); 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, diacetoneacrylamide, and N-phenyl(meth)acrylamide; acid anhydride monomers such as maleic anhydride and itaconic anhydride; Examples of suitable vinyl isocyanates include 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.

[0061] When the other monomer has an acid group or a hydroxyl group, the acid group or the hydroxyl group may react with a crosslinking agent described later to form a crosslinked structure. Specific examples of the acid group include a carboxyl group, a sulfo group, a phosphonic acid group, and a phosphoric acid group, with a carboxyl group being preferred. The acid group may also form an acid anhydride group. The acid group may also be in the form of a salt such as an alkali metal salt, an organic amine salt, or an ammonium salt.

[0062] When the specific acrylic resin has structural units derived from other monomers, the content of the structural units derived from other monomers is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 5 to 10% by mass, relative to all structural units (100% by mass) contained in the specific acrylic resin.

[0063] The content of the specific acrylic resin is preferably from 20 to 90% by mass, more preferably from 30 to 80% by mass, based on the total mass of the release layer.

[0064] (Additives) The release layer may contain additives as components other than the specific acrylic resin. Examples of additives include light release additives and heavy release additives for adjusting the release force, surfactants, adhesion improvers, and antistatic agents. In particular, 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. When the release layer contains an additive, the content of the additive is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, relative to the total mass of the release layer.

[0065] 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.

[0066] The release layer preferably has a crosslinked structure from the viewpoint of preventing the generation of foreign matter in the polyester substrate and solvent resistance. The crosslinked structure may be, for example, a crosslinking agent and a reactive group X and —Si(R) ３When a release layer is formed using a release layer-forming composition containing an acrylic resin having a group represented by the formula (I), the release layer is formed by reacting the reactive group X of the acrylic resin with a crosslinking agent (specifically, the reactive group Y described below). That is, the crosslinked structure of the release layer is preferably a structure derived from the reactive group X of the acrylic resin and the reactive group Y of the crosslinking agent (preferably a structure formed by the reaction of the reactive group X of the acrylic resin and the reactive group Y of the crosslinking agent). Specific examples of the reactive group X include the above-mentioned acid group and hydroxyl group.

[0067] The release layer is preferably a layer formed by an addition reaction between the reactive group X of the acrylic resin and the reactive group Y of the crosslinking agent, 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.

[0068] (Thickness of release layer) The thickness of the release layer is 450 nm or less, and is preferably 200 nm or less, more preferably less than 150 nm, more preferably 120 nm or less, particularly preferably 50 nm or less, and most preferably 40 nm or less, in order to improve the releasability of the sheet formed on the surface of the release layer.The thickness of the release layer is preferably 2 nm or more, more preferably 10 nm or more.The thickness of the release layer is measured by preparing a slice having a cross section perpendicular to the main surface of the polyester film and using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and is the arithmetic average value of the thicknesses of five locations of the release layer in the slice.

[0069] (Surface free energy) The surface free energy of the release layer surface is 40 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, less than 29 mJ / m２ 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 surface free energy of the release layer surface is preferably -Si(R) in the specific acrylic resin. ３ The surface free energy of the release layer surface can be adjusted by adjusting the content of the structural unit having a group represented by the formula (I). The method for measuring the surface free energy of the release layer surface is as described in the Examples section below. The "surface free energy" measured by the method described below is the sum of the polar component and the hydrogen bond component of the surface free energy.

[0070] (Maximum protrusion height and average surface roughness) When the film 1 is used to manufacture 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. Furthermore, it is 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 the release layer is formed using the above-mentioned specific acrylic resin, 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. 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 particle-free and forms a smooth film (for example, by using a polyester resin polymerized with a titanium compound or an aluminum compound). The maximum protrusion height and average surface roughness of the release layer surface are determined by measuring the release layer surface of the polyester film using an optical interferometer (for example, Hitachi High-Tech Corporation's "Vertscan 3300G Lite" etc.) under the conditions described in the Examples section, and then analyzing the data using the built-in data analysis software. In measuring the maximum protrusion height, measurements are taken five times at different measurement positions, and the maximum value of the obtained measured values ​​is taken as the measured value of the maximum protrusion height (represented as P in the built-in data analysis software). In measuring the average surface roughness, measurements are taken five times at different measurement positions, and the average value of the obtained measured values ​​is taken as the measured value of the average surface roughness.

[0071] <Protrusions and protrusion-containing layer> The film 1 preferably has protrusions on the surface of the polyester film facing the polyester substrate (the surface of the polyester film opposite the release surface, hereinafter also referred to as the "smooth surface"). When the film 1 has protrusions on the smooth surface, the polyester film has excellent slip properties and can be improved in transportability.

[0072] The height of the protrusions is preferably 0.02 μm or more, more preferably 0.03 μm or more, from the viewpoint of excellent transportability. Furthermore, the height of the protrusions 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 height of the protrusions 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 film 1 is brought into contact with the slippery surface, and winding problems such as winding slippage are less likely to occur when the film 1 is wound up.

[0073] 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 film 1 may have a protrusion-containing layer on the side opposite the release layer of the polyester substrate. In other words, the film 1 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 provided directly on the surface of the polyester substrate or via an intermediate layer, but is preferably provided directly on the surface of the polyester substrate from the viewpoint of superior productivity. That is, the film 1 may be composed of a release layer, a polyester substrate, and a protrusion-containing layer, and the release layer and the polyester substrate may be adjacent to each other, and the polyester substrate and the protrusion-containing layer may be adjacent to each other.

[0074] 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 film 1. Hereinafter, the particle-containing layer will be described as an example of the protrusion-containing layer.

[0075] (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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] The thickness of the particle-containing layer is preferably 1 nm to 1 μm, more preferably 1 to 500 nm, and even more preferably 1 to 200 nm, from the viewpoint of achieving low haze. 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).

[0083] The maximum protrusion height (Sp) of the protrusion-containing layer is preferably 20 nm or more. The maximum protrusion height of the protrusion-containing layer is preferably 800 nm or less, more preferably 300 nm or less. The maximum protrusion height of the protrusion-containing layer can be measured in the same manner as the maximum protrusion height of the release layer, except that the protrusion-containing layer is measured.

[0084] <Characteristics of Film 1> It is preferable that the film 1 exhibits various characteristics. Preferred characteristics of the film 1 will be described.

[0085] The thickness of the film 1 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 film 1 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.

[0086] In film 1, the dynamic friction coefficient is preferably 0.2 or more. The dynamic friction coefficient in film 1 refers to the friction coefficient on both sides of film 1, and more specifically refers to the dynamic friction coefficient between the release layer surface and the surface of film 1 opposite the release layer surface (a smooth surface, for example, the surface opposite the polyester substrate side of the protrusion-containing layer). If the dynamic friction coefficient is 0.2 or more, film 1 is less likely to slip when wound into a roll. Furthermore, the dynamic friction coefficient is preferably less than 1.0. If the dynamic friction coefficient is less than 1.0, blocking is less likely to occur when film 1 is wound into a roll. The dynamic friction coefficient can be measured in accordance with ASTM D 1894-95. A detailed procedure for measuring the dynamic friction coefficient shall follow the method described in the Examples below.

[0087] The thermal shrinkage of film 1 in the machine direction measured at 150°C is preferably 0 to 3.0%, more preferably 0 to 2.0%, and even more preferably 0 to 1.5%. Furthermore, the thermal shrinkage of film 1 in the width direction measured at 150°C is preferably 0 to 2.0%, more preferably 0 to 1.5%, and even more preferably 0 to 1.0%. When the thermal shrinkage of film 1 is within the above range, the dimensional stability of the ceramic green sheet formed on the release layer surface of film 1 and the dimensional stability when the ceramic green sheet is peeled from film 1 and then laminated is good, reducing the likelihood of failure of electronic components. The method for measuring each of the above thermal shrinkages is described in the Examples section below. The thermal shrinkage of film 1 can be adjusted by selecting the heating or cooling conditions during the production of film 1. More specifically, the thermal shrinkage can be adjusted by changing at least one of the conditions of the heat setting process, heat relaxation process, and cooling process described below.

[0088] <Method for producing film 1> A method for producing a polyester film in a first embodiment is a method for producing a polyester film including a release layer and a polyester substrate, and the method comprises the steps of: ３ The polyester film manufacturing method of the first embodiment includes a step of applying a release layer-forming composition (hereinafter also referred to as "composition M") containing an acrylic resin having a group represented by the formula (I) and a solvent containing water to at least one surface of the polyester substrate. The polyester film manufacturing method of the first embodiment preferably further includes a step of stretching (preferably a transverse stretching step described below) the polyester substrate with the coating film obtained by the above-mentioned coating step (i.e., a polyester substrate having a coating film of composition M formed on one surface thereof). According to the polyester film manufacturing method of the first embodiment, the above-mentioned film 1 can be manufactured. Hereinafter, the polyester film manufacturing method of the first embodiment will also be referred to as the "method for manufacturing film 1."

[0089] One preferred embodiment of the method for producing film 1 involves melt-extruding a polyester resin to produce an unstretched polyester substrate, stretching the unstretched polyester substrate longitudinally, applying composition M to one side of the longitudinally stretched polyester substrate, and then stretching the resulting polyester substrate transversely to produce a polyester film. Furthermore, if composition M further contains a crosslinking agent and the acrylic resin has a reactive group X that can react with the crosslinking agent, the method may include a step of reacting the acrylic resin with the crosslinking agent. In this case, one preferred embodiment of the method for producing film 1 includes a longitudinal stretching step in which the unstretched polyester substrate is longitudinally stretched, a coating film formation step in which a coating film of composition M is formed, a release layer formation step in which the acrylic resin contained in the coating film is reacted with the crosslinking agent to form a release layer, and a transverse stretching step in which the polyester substrate is transversely stretched. The coating film formation step may be performed before the longitudinal stretching step, i.e., on the unstretched polyester substrate. The release layer forming step may be performed as a separate step from the stretching step (longitudinal stretching step or transverse stretching step), or may be performed in the same step as the stretching step. It is particularly preferable to perform the release layer forming step together with the transverse stretching step, i.e., to react the acrylic resin contained in the coating film with the crosslinking agent when performing transverse stretching. When the release layer forming step is performed together with the stretching step, it is preferable to select a material suitable for the stretching conditions, and it is more preferable to select a combination of the reactive group X of the acrylic resin and the crosslinking agent suitable for the stretching conditions. Hereinafter, each step that may be included in the method for producing film 1 will be described.

[0090] The method for producing the film 1 preferably includes the longitudinal stretching step. The longitudinal stretching can be performed, for example, by conveying an unstretched polyester substrate in the machine direction while applying tension between two or more pairs of stretching rolls arranged in the conveying direction. The stretching 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.

[0091] The method for producing the film 1 preferably includes the above-mentioned coating film forming step. The composition M used in the coating film forming step is —Si(R) ３ and a solvent containing water. Preferably, composition M further contains a crosslinking agent, and the acrylic resin has a reactive group X that can react with the crosslinking agent.

[0092] -Si(R) ３ The acrylic resin having a group represented by the formula (I) includes the specific acrylic resins described above, and the preferred embodiments are also the same. However, the —Si(R) ３ In the case where the acrylic resin having a group represented by the formula (I) has a reactive group X, the reactive group X has not reacted with the crosslinking agent and has not formed a crosslinked structure before the release layer forming step. ３ The acrylic resin having a group represented by the formula (I) preferably has at least one selected from the group consisting of a reactive group X and a polyalkylene oxide chain. Specific examples of the reactive group X include an acid group and a hydroxyl group, and specific examples of the acid group are as described above. The reactive group X is preferably a carboxy group contained in the structural unit derived from the above-mentioned (meth)acrylic acid. Specific examples of the polyalkylene oxide chain are as described above. The polyalkylene oxide chain is preferably a polyalkylene oxide chain contained in the structural unit derived from the above-mentioned (meth)acrylic acid ester containing the polyalkylene oxide chain. -Si(R) ３ When the acrylic resin having a group represented by the formula (R) 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 water-soluble acrylic resin described below) having excellent solubility in a solvent (particularly water) is used in this way, the coating uniformity of the composition M on the polyester substrate is improved, and a release layer having excellent surface smoothness (a release layer with few coating defects) can be obtained. In particular, when the acrylic resin having a group represented by the formula (R) 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 having an excellent solubility in a solvent (particularly water) is used, the coating uniformity of the composition M on the polyester substrate is improved, and a release layer having excellent surface smoothness (a release layer with few coating defects) can be obtained. ３When the acrylic resin having a group represented by the formula (I) has high solubility in water, it is suitable for a production method in which composition M is applied before the stretching step (so-called in-line coating method), and since the in-line coating method improves the uniformity of application, a release layer having excellent surface smoothness can be obtained.

[0093] -Si(R) ３ The acrylic resin having a group represented by —Si(R) may be contained alone or in combination with two or more thereof. ３ The content of the acrylic resin having a group represented by the formula (I) is preferably 20 to 90 mass %, more preferably 30 to 80 mass %, based on the total mass of the components (solid content) other than the solvent of the composition M.

[0094] -Si(R) ３ The acid value of the acrylic resin having a group represented by —Si(R) 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 0.7 to 4.0 mmol / g, and most preferably 1.0 to 3.8 mmol / g. ３ The hydroxyl value of the acrylic resin having a group represented by the formula (I) 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 lower limit, the water solubility and curability of the resin are superior. When the acid value or hydroxyl value is equal to or less than the above lower limit, the releasability of the release film is superior. The methods for calculating the acid value and hydroxyl value are as described in the Examples section below.

[0095] The solvent includes water and —Si(R) ３An acrylic resin having a group represented by the formula (I) is dissolved in composition M. 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. The water content is preferably 70 to 100% by mass, and more preferably 80 to 99% by mass, relative to the total mass of the solvent. When the solvent contains an alcohol, the alcohol content is preferably 0.5 to 30% by mass, and more preferably 0.5 to 15% by mass, and 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 M. That is, the total solid content in composition M is preferably 0.5 to 20% by mass, and more preferably 1.0 to 10% by mass, relative to the total mass of composition M.

[0096] Composition M preferably contains a crosslinking agent. The crosslinking agent is preferably water-soluble in view of suitability for in-line application. The crosslinking agent preferably has a reactive group Y capable of reacting with the reactive group X. The reactive group Y is not particularly limited as long as it is a group capable of reacting with the reactive group X. However, when the reactive group X is an acid group, an oxazoline group, a carbodiimide group, an epoxy group, a methylol group, an isocyanate group, or a blocked isocyanate group is preferred in view of excellent reactivity with the acid group. Here, a 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 reactive group X is a hydroxyl group, the reactive group Y is preferably an isocyanate group, a methylol group, or a blocked isocyanate group in view of excellent reactivity with the hydroxyl group. Examples of crosslinking agents having a reactive group Y include oxazoline-based compounds, carbodiimide-based compounds, epoxy-based compounds, melamine-based compounds, and isocyanate-based compounds. The isocyanate compound may be a compound having a blocked isocyanate group in which the isocyanate group is blocked with a blocking agent. Commercially available crosslinking agents having a reactive group Y include, for example, Carbodilite V-02-L2 (manufactured by Nisshinbo Chemical Inc.), Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.), Epocross K-2020E (manufactured by Nippon Shokubai Co., Ltd.), Denacol-EX-521 (manufactured by Nagase ChemteX Corporation), and Duranate (registered trademark) WM44-L70G (manufactured by Asahi Kasei Corporation). For details on epoxy compounds, melamine compounds, and isocyanate compounds, please refer to the descriptions of

[0081] to

[0083] in JP 2015-163457 A. The crosslinking agents described in

[0082] to

[0084] in WO 2017 / 169844 A can also be preferably used. For carbodiimide compounds, reference can be made to the descriptions in paragraphs

[0038] to

[0040] of JP 2017-087421 A. For oxazoline compounds, carbodiimide compounds, and isocyanate compounds, the crosslinking agents described in paragraphs

[0074] to

[0075] of WO 2018 / 034294 A can also be preferably used.

[0097] The oxazoline-based compound is not particularly limited as long as it is a compound having an oxazoline group, and may be a low molecular weight compound having a weight average molecular weight of 1,000 or less, or a high molecular weight compound having a weight average molecular weight of more than 1,000. However, a high molecular weight compound is preferred in that the release layer has better solvent resistance.

[0098] 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.

[0099] 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.

[0100] The polymer compound having an oxazoline group is preferably a copolymer containing a structural unit derived from the low molecular weight compound having an oxazoline group and a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain. By including a polyalkylene oxide chain in the polymer compound having an oxazoline group, the water solubility of the crosslinking agent can be improved.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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, 2- Examples of the monomer include sulfo group-containing monomers such as acrylamido-2-methylpropanesulfonic 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, 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.

[0105] The polymer compound having an oxazoline group is preferably water-soluble in view of suitability for in-line coating.

[0106] The weight-average molecular weight 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) of the polymer compound having an oxazoline group can be measured by gel permeation chromatography (GPC). Measurement by gel permeation chromatography (GPC) is performed using an HLC (registered trademark)-8320GPC (manufactured by Tosoh Corporation) as the measuring device, two TSKgel (registered trademark) Super Multipore HZ-M columns (4.6 mm ID x 15 cm, manufactured by Tosoh Corporation) as the columns, and THF (tetrahydrofuran) as the eluent. Furthermore, measurements are performed using a sample concentration of 0.3% by mass, a flow rate of 0.35 mL / min, a sample injection volume of 10 μL, and a measurement temperature of 40°C, and an RI (Refractive Index) detector. The calibration curve is 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".

[0107] 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.).

[0108] The isocyanate compound is a compound having an isocyanate group or a blocked isocyanate group. The isocyanate compound is preferably a blocked isocyanate compound (i.e., a compound having a blocked isocyanate group). A blocked isocyanate compound is a compound in which the isocyanate group of a polyisocyanate is protected (i.e., blocked) with a blocking agent, and is included in the isocyanate compound 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] The carbodiimide compound is a compound having a carbodiimide group. The carbodiimide compound 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 an aromatic diisocyanate, an aliphatic diisocyanate, and an alicyclic diisocyanate. Specific examples of the aromatic diisocyanate, the aliphatic diisocyanate, and the alicyclic diisocyanate are the same as the specific examples of the diisocyanate described in the section on isocyanate compounds.

[0118] 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.

[0119] In this specification, the melamine-based compound refers to 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 ２Examples 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.

[0120] The epoxy compound is not particularly limited as long as it has an epoxy group. The epoxy compound preferably 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. The alicyclic epoxy group refers to a group such as a 3,4-epoxycyclohexyl group, for example.

[0121] 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).

[0122] 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.

[0123] 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.

[0124] 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 can be improved.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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) of the polymer compound having an epoxy group is measured in the same manner as the weight average molecular weight (Mw) of the polymer compound having an oxazoline group described above.

[0129] The crosslinking agent may be used alone or in combination with two or more other agents. When the composition M contains a crosslinking agent, the content of the crosslinking agent is preferably 1 to 50 mass %, and more preferably 10 to 40 mass %, based on the total mass of the components (solid content) other than the solvent of the composition M, in terms of the reactivity of the acrylic resin.

[0130] Composition M may contain the additives that can be contained in the release layer described above. When composition M contains the additives, the content of the additives is preferably 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, based on the total mass of the components (solid content) other than the solvent of composition M.

[0131] The method for applying composition M is not particularly limited, and known methods can be used. Examples of the application method include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating. As the application method, it is preferable to use an in-line coating method (in-line application method) in which composition M is applied to one surface of the longitudinally stretched polyester substrate while the longitudinally stretched polyester substrate is being transported.

[0132] When producing a polyester film having a protrusion-containing layer, for example, a particle-containing layer-forming composition may be applied to the surface of the polyester substrate opposite to the surface coated with composition M. The particle-containing layer-forming composition may be any composition as long as it contains the components contained in the particle-containing layer described above.

[0133] The method for producing film 1 preferably includes a release layer-forming step. When composition M includes the crosslinking agent and the acrylic resin has a reactive group X that can react with the crosslinking agent, the release layer-forming step is a step of reacting the acrylic resin with the crosslinking agent. Specifically, the release layer-forming step is a step of reacting the reactive group X of the acrylic resin with the reactive group Y of the crosslinking agent to form a release layer having a crosslinked structure. To promote the reaction, the release layer-forming step preferably includes a treatment of heating the coating film obtained in the coating film-forming step. In this case, the heating temperature is preferably 60 to 250°C, more preferably 80 to 230°C.

[0134] The method for producing the film 1 preferably includes the transverse stretching step. The transverse stretching refers to a process of stretching the polyester substrate in the width direction.

[0135] The method for producing the film 1 may include other steps in addition to the longitudinal stretching step, the coating film forming step, the release layer forming step, and the transverse stretching step. The production method according to this embodiment 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 and heat relaxing the polyester substrate heat-set in the heat setting step at a temperature lower than that in the heat setting step, 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.

[0136] Although the polyester film manufacturing method described above involves applying the composition M to one surface of the polyester substrate between the longitudinal stretching step and the transverse stretching step, the manufacturing method of the film 1 is not limited to the above method. For example, the composition M may be applied to one surface of the polyester substrate after the transverse stretching step.

[0137] <Applications> Film 1 can be used in a variety of applications. For example, Film 1 is preferably used as a release film (carrier film) for producing ceramic green sheets. Ceramic green sheets produced using Film 1 can be suitably used for producing ceramic capacitors, which require multilayer internal electrodes in response to miniaturization and increased capacitance.

[0138] The method for producing a ceramic green sheet using the film 1 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 release layer surface of the film 1 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 applied, 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.

[0139] The produced ceramic green sheets are used to manufacture ceramic capacitors. Known methods can be used to manufacture ceramic capacitors using ceramic green sheets, including, for example, the following method. First, internal electrodes are provided on a laminate of film 1 and ceramic green sheets by coating or printing a conductive paste. Next, film 1 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 the cut intermediate laminate is 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.

[0140] Film 1 can also be used as a protective film for dry film resist, 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.

[0141] [Second embodiment] A second embodiment of the polyester film of the present invention is a polyester film comprising a release layer containing an acrylic resin and a polyester substrate, wherein the surface free energy of the release layer surface is 17 mJ / m ２ 30mJ / m or more ２ This is an embodiment in which the number of units is less than 1.

[0142] The polyester film of the second embodiment has excellent coatability with compositions containing organic solvents and excellent releasability of the sheet formed on the release layer surface. The details of the reason for this are not clear, but it is generally assumed as follows: The surface free energy of the release layer surface is 30 mJ / m ２ It is presumed that the release layer contains an acrylic resin and the surface free energy of the release layer surface is less than 17 mJ / m, thereby improving the release property of the sheet (particularly the ceramic green sheet) formed on the release layer surface. ２ It is presumed that the above-mentioned conditions have improved the coatability of compositions containing organic solvents (e.g., ceramic slurries). The components contained in the polyester film of the present invention will be described below. Hereinafter, the polyester film of the second embodiment will also be referred to as "film 2."

[0143] <Polyester Base> The polyester base in Film 2 is the same as the polyester base in Film 1, including the preferred embodiment, and therefore a description thereof will be omitted.

[0144] <Release Layer> In the film 2, the surface of the release layer (the surface of the polyester film opposite to the polyester substrate; in the example of FIG. 1, the other surface 22; the same applies below) has a surface free energy of 30 mJ / m ２ and the peelability of the sheet formed on the surface of the release layer is superior, ２ In addition, the surface free energy of the release layer of the film 2 is preferably 17 mJ / m or less. ２ and the coating property of the composition containing the organic solvent is superior, and ２ More than 24 mJ / m is preferable. ２The surface free energy of the release layer surface can be determined according to the method described in the Examples section below.

[0145] The release layer of film 2 contains an acrylic resin. For the release layer of film 2, one method for adjusting the surface free energy of the release layer surface within the above-mentioned range is to use the specific acrylic resin contained in the release layer of film 1. That is, the release layer of film 2 preferably contains the specific acrylic resin as the acrylic resin. When the release layer of film 2 contains the specific acrylic resin, the specific acrylic resin is the same as the specific acrylic resin contained in film 1, including preferred embodiments, and therefore a description thereof will be omitted. The content of the acrylic resin (preferably the specific acrylic resin described above) is preferably 20 to 90% by mass, and more preferably 30 to 80% by mass, relative to the total mass of the release layer.

[0146] The release layer of film 2 may contain an additive. The additive is the same as the additive that may be contained in film 1, including the preferred embodiment, and therefore a description thereof will be omitted. When the release layer contains an additive, the content of the additive is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total mass of the release layer.

[0147] The release layer of the film 2 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.

[0148] The release layer of the film 2 preferably has a cross-linked structure, which is the same as the cross-linked structure in the release layer of the film 1, and therefore a description thereof will be omitted.

[0149] The thickness of the release layer in film 2 is the same as that of the release layer in film 1, and therefore a description thereof will be omitted.

[0150] The maximum projection height (Sp) and average surface roughness of the release layer surface of film 2 are similar to those of film 1, and therefore will not be described here.

[0151] <Protrusions and protrusion-containing layer> Film 2 preferably has protrusions on the surface of the polyester film facing the polyester substrate (this refers to the surface of the polyester film opposite the release surface, hereinafter also referred to as the "smooth surface"). The protrusions are the same as the protrusions in Film 1, and therefore a description thereof will be omitted. The protrusions may be formed directly on the polyester substrate described above, or may be formed by a protrusion-containing layer that is a layer separate from the polyester substrate. The protrusion-containing layer is the same as the protrusion-containing layer in Film 1, and therefore a description thereof will be omitted.

[0152] <Characteristics of Film 2> The various characteristics of Film 2 (thickness, dynamic friction coefficient, etc.) are the same as those of Film 1, and therefore description thereof will be omitted.

[0153] <Method for producing film 2> The method for producing the polyester film in the second embodiment is the same as the method for producing film 1, and therefore, the description thereof will be omitted.

[0154] [Release Agent] The release agent of the present invention contains a water-soluble acrylic resin having a structural unit represented by the above formula (1) and a structural unit derived from the above (meth)acrylic acid or a salt thereof. The release agent of the present invention is suitably used for forming the release layer described above.

[0155] <Water-Soluble Acrylic Resin> The water-soluble acrylic resin is a (meth)acrylic resin that has a structural unit represented by the above formula (1) and a structural unit derived from the above (meth)acrylic acid or a salt thereof and is water-soluble. Here, the (meth)acrylic resin being water-soluble means that, after mixing 2 g (solid content: 0.2 g) of a composition consisting of the (meth)acrylic resin and a mixed solution of ethanol and water (ethanol:water=53:47 (mass ratio)) with 30 g of water at 25°C, and stirring the mixture at 25°C for 10 minutes using a mix rotor at 60 rpm, no particle size is observed using a particle size analyzer.

[0156] Specific examples and preferred embodiments of the structural unit represented by formula (1) are the same as those of the structural unit represented by formula (1) in the specific acrylic resin. The content of the structural unit represented by formula (1) 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 all structural units (100% by mass) contained in the water-soluble acrylic resin.

[0157] Specific examples and preferred embodiments of the structural units derived from (meth)acrylic acid or a salt thereof are the same as those of the structural units derived from (meth)acrylic acid or a salt thereof in the specific acrylic resin. The content of the structural units derived from (meth)acrylic acid or a salt thereof is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, relative to all structural units (100% by mass) possessed by the water-soluble acrylic resin.

[0158] It is preferable that the water-soluble acrylic resin further contains a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain. This allows the water-soluble acrylic resin to exhibit good water solubility. Specific examples and preferred embodiments of the structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain are the same as those of the structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain in the specific acrylic resin. When the water-soluble acrylic resin contains a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain, the content of the structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain is preferably 5 to 80% by mass, more preferably 7 to 70% by mass, and even more preferably 10 to 60% by mass, relative to all structural units (100% by mass) contained in the water-soluble acrylic resin.

[0159] The acid value of the water-soluble acrylic resin 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 0.7 to 4.0 mmol / g, and most preferably 1.0 to 3.8 mmol / g. The hydroxyl value of the water-soluble acrylic resin 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. The methods for calculating the acid value and hydroxyl value are as described in the Examples section below.

[0160] The content of the water-soluble acrylic resin is preferably 20 to 90% by mass, more preferably 25 to 85% by mass, and even more preferably 30 to 80% by mass, based on the total mass of the release agent.

[0161] <Method for producing water-soluble acrylic resin> The method for producing the water-soluble acrylic resin is not particularly limited, and the resin can be produced according to a conventional method for producing an acrylic resin. For example, the water-soluble acrylic resin can be produced by reacting the above-mentioned monomers (—Si(R) ３ Examples of suitable methods include polymerizing a (meth)acrylic acid ester having a group represented by the formula (I), (meth)acrylic acid or a salt thereof, or a (meth)acrylic acid ester containing a polyalkylene oxide chain. Examples of the polymerization initiator include known radical polymerization initiators. Examples of the polymerization solvent include alcohols (e.g., ethanol, 1-propanol, 2-propanol). In the production of a water-soluble acrylic resin, additives used in conventional acrylic resin production may be used, examples of which include chain transfer agents (e.g., dodecyl mercaptan), neutralizing agents (e.g., dimethylaminoethanol, aqueous ammonia, diisopropylethylamine, dipropylamine), and the like. Polymerization of the monomer is preferably carried out under heating, and specifically, the heating temperature (polymerization temperature) is preferably 70 to 85°C.

[0162] <Additives> The release agent may contain additives as components other than the water-soluble acrylic resin. Specific examples of additives include surfactants, antifoaming agents, and silane coupling agents. When the release agent contains additives, the content of the additives is preferably 0.1 to 10 mass %, more preferably 0.5 to 7 mass %, and even more preferably 1 to 5 mass %, relative to the total mass of the release agent.

[0163] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, and treatment procedures 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.

[0164] [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 obtained film with the coating was stretched transversely to produce a biaxially stretched polyester film with a width of 1500 mm, which was then wound up every 7000 m without knurling. The thickness of the produced biaxially stretched polyester film (polyester film of Example 1) was 31 μm. The polyester substrate in the polyester film was substantially free of particles.

[0165] (Protrusion-Containing Layer Forming Composition X1) The components shown below were mixed, and then subjected to the above-mentioned filtration treatment and membrane degassing to obtain protrusion-containing layer forming composition X1. - Aqueous dispersion of urethane resin (Superflex (registered trademark) 210, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) with a solid content of 35% by mass: 115 parts by mass - Aqueous dilution of anionic hydrocarbon surfactant (Rapisol (registered trademark) A-90, manufactured by NOF Corporation) with a solid content of 1% by mass: 48 parts by mass - Aqueous dispersion of non-crosslinked styrene resin particles (Nipol (registered trademark) UFN1008, manufactured by Zeon Corporation) with a solid content of 20% by mass: 11.2 parts by mass - Aqueous dispersion of particles (PMMA resin particles, MP1000, manufactured by Soken Chemical & Engineering Co., Ltd.) with a solid content of 5% by mass: 224 parts by mass - Aqueous solution of crosslinker (oxazoline compound, Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd.) with a solid content of 25% by mass: 32.2 parts by mass - Water: 570 parts by mass

[0166] (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 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) Oxazoline crosslinking agent D1 (aqueous solution containing an oxazoline compound, EPOCROS (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., aqueous solution with a solid content of 25% by mass) (referred to as oxazoline in the table): 44 parts by mass (11 parts by mass in terms of solid content) Water: 873.5 parts by mass

[0167] -Method for synthesizing acrylic resin A1- Ethanol (42.20 g) was placed in a 500 ml three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75°C under a nitrogen stream. To this, mixed solution 1, which was a mixture of 0.39 g of V-601 (radical polymerization initiator; manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 13.30 g of ethanol, and mixed solution 2, which was a mixture of 10.00 g of methacrylic acid (MAA), 30.00 g of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TrisMA), 10.00 g of polyethylene glycol monomethyl ether methacrylate (Blemmer PME1000; manufactured by NOF Corporation; referred to as "PME1000" in the table below), 0.57 g of dodecyl mercaptan, and 47.51 g of ethanol, were each added dropwise at a constant rate under conditions such that the dropwise addition was completed within 3 hours. After completion of the dropwise addition of the mixed solution, a mixed solution of 0.20 g of V-601 and 1 g of ethanol was added to the resulting reaction mixture, and the mixture was heated and stirred for 5 hours. To the resulting reaction mixture was added 7.08 g of ethanol, and then 8.28 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.

[0168] Examples 2 to 27 Compositions L2 to L25 were prepared by changing the components as shown in the table below instead of composition L1 used to form the release layer, and biaxially stretched films (polyester films) of Examples 2 to 27 were obtained. The amount of each component in compositions L2 to L25 was adjusted so that the solids concentration was the same as that of composition L1. Of the components used in preparing compositions L2 to L25, 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.

[0169] (Monomers used in the synthesis of acrylic resin A) 3-[tris(trimethylsilyloxy)silyl]propyl acrylate (TrisA) Methacrylic-modified silicone oil (manufactured by JNC Corporation, trade name "Silaplane FM-0711", CH ２ =C(CH ３ )-C(O)O-C ３H ６ -Si(CH ３ ) ２ -[O-Si(CH ３ ) ２ ] ｍ —O—Si(CH ３ ) ２ (C ４ H ９ The definition of m in the formula is the same as in the above formula (1).) (SiMA-1) Methacrylic-modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-22-174ASX", CH ２ = C(R １１ )-C(O)O-L １１ -Si(CH ３ ) ２ -[O-Si(CH ３ ) ２ ] ｍ —O—Si(CH ３ ) ２ (R Ｄ ). R in the formula １１ The definitions of and m are the same as those in the above formula (1), and R Ｄ The definition is as above. ) (SiMA-2) Acrylic acid (AA) Polyethylene glycol monomethyl ether methacrylate (manufactured by NOF Corporation, trade name "Blemmer PME400") (PME400) Methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "M-90G") (M-90G) Polyethylene glycol monomethyl ether methacrylate (manufactured by NOF Corporation, trade name "Blemmer PME200") (PME200) Methoxypolyethylene glycol #400 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "AM-90G") (AM-90G) Methyl methacrylate (MMA) Styrene (St) Benzyl methacrylate (BZMA) n-Butyl acrylate (nBA) 2-Methacryloyloxyethyl acid phosphate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Ester P-1M") (P-1M) Hydroxyethyl methacrylate (HEMA) N-isopropylacrylamide (manufactured by KJ Chemicals Co., Ltd., trade name "NIPAM") (NIPAM) Diacetone acrylamide (DAAM)

[0170] (Neutralizing agent) Diisopropylethylamine (DIPEA) Dipropylamine (DPA) 28% aqueous ammonia (NH3aq)

[0171] (Crosslinking Agents) Epoxy crosslinking agent resin composition: Denacol-EX-521 (water-soluble) (manufactured by Nagase ChemteX Corporation) (epoxy) Carbodiimide crosslinking agent (aqueous solution containing a carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Inc., aqueous solution with a solid content of 25% by mass) (carbodiimide) Isocyanate crosslinking agent (solution containing a blocked isocyanate compound, Duranate (registered trademark) WM44-L70G, manufactured by Asahi Kasei Corporation, dipropylene glycol dimethyl ether solution with a solid content of 70% by mass) (blocked isocyanate)

[0172] Comparative Example 1 A biaxially stretched 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 is the coating liquid used in Example 14 of JP 2021-11081 A, and contains silicone (referred to as "AX1" in the table below), and has the above-mentioned -Si(R ３ The present invention does not include an acrylic resin having a group represented by the formula:

[0173] <Comparative Example 2> A biaxially stretched 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 a composition of the following composition used in Example 1 of WO 2021 / 192896. The acrylic resin AX2 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). The acrylic resin AX2 is -Si(R ３The composition does not have a group represented by the formula: In addition, the oxazoline crosslinking agent CX2 (oxazoline) contained in the composition LX2 is the oxazoline crosslinking agent C-1 used in Example 1 of WO 2021 / 192896. (Composition LX2) Water: 45.76 parts by mass Isopropyl alcohol: 28.20 parts by mass Acrylic resin AX2 (solid content concentration 20% by mass): 14.00 parts by mass Oxazoline crosslinking agent CX2 (solid content concentration 10% by mass): 12.00 parts by mass Polyether-modified polydimethylsiloxane, 67 Additive (solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.): 0.04 parts by mass

[0174] [Physical Properties of Acrylic Resin] <Acid Value and Hydroxyl Value> The theoretical values ​​of the acid value and hydroxyl value of the acrylic resin, calculated from the amounts of the monomers used in producing the acrylic resin, are shown in Table 1. When the acid value of the acrylic resin was measured by the following measurement method, the measured value was almost the same as the theoretical value described above.

[0175] (Method for Measuring Acid Value) 1.0 g of sample (acrylic resin) 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.

[0176] <Water Solubility> 2 g of a composition (0.2 g solids) consisting of the acrylic resin used in preparing each release layer-forming composition in the Examples and Comparative Examples and a mixed solution of ethanol and water (ethanol:water = 53:47 (mass ratio)) was mixed with 30 g of water at 25°C, and the mixed solution at 25°C was stirred for 10 minutes at 60 rpm using a mix rotor. The mixed solution after stirring was evaluated for water solubility based on the following evaluation criteria. A: When the mixed solution after stirring is visually observed, it is colorless and transparent. B: When the mixed solution after stirring is visually observed, it is cloudy. Furthermore, when an attempt was made to measure the particle size of the mixed solution after stirring using a concentrated particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), particle size measurement was not possible for the mixed solution rated "A" above, but particle size measurement was possible for the mixed solution rated "B" above.

[0177] [Film Properties] <Heat Shrinkage> The heat shrinkage of the polyester films obtained in Examples 1 to 27 in the machine direction and width direction at a temperature of 150°C was measured by the following method. Rectangular samples measuring 350 mm in the measurement direction (machine direction or width direction) and 50 mm in the direction perpendicular to the measurement direction were cut out at five points in the width direction of each polyester film. Two gauge marks were marked at 300 mm intervals near both ends of the measurement direction of the obtained samples. The obtained samples were left in an oven adjusted to a temperature of 150°C for 30 minutes and then allowed to cool to room temperature. The distance between the gauge marks on the sample at room temperature was measured, and this length was designated L (mm). The heat shrinkage of each of the five samples was calculated using the following formula, and the maximum and minimum values ​​of the obtained heat shrinkage were expressed as the 150°C heat shrinkage in each measurement direction, as "minimum value to maximum value %." Heat shrinkage rate at 150°C (%) = 100 × (300 - L) / 300 For each polyester film, the heat shrinkage rate in the machine direction was in the range of 1.29 to 1.61%, and the heat shrinkage rate in the width direction was in the range of 0.83 to 1.03%.

[0178] <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. Droplets of 2 μL of purified water, 1 μL of methylene iodide, and 1 μL of ethylene glycol were used, and the surface free energy was calculated from the measured contact angles using the Kitazaki-Hata method.

[0179] <Maximum protrusion height Sp> The maximum protrusion height Sp of the release layer surface of the polyester film was measured by the following method. The release layer surface of the polyester film was measured under the following conditions using an optical interferometer (Vertscan 3300G Lite, manufactured by Hitachi High-Tech Corporation), and then analyzed using the built-in data analysis software (VS-Measure5) to determine the maximum protrusion height Sp of the release layer surface. In measuring the maximum protrusion height Sp, the maximum value of the measured values ​​obtained from five measurements at different measurement positions was used. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x Measurement area: 186 μm × 155 μm

[0180] [Performance] <Coating Defects> A 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)

[0181] <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.

[0182] (Coatability (Cleaning) of Ceramic Slurry) 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, and 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 confirmed, 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.

[0183] (Releasability) The 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 180°, a peel temperature of 25°C, and a peel speed of 3 m / min. The peeling 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 peel the sheet. The average peel force of the measured values ​​obtained over peel distances of 20 mm to 50 mm was calculated, and this value was used as the peel force. The measurement was performed five times, and the average value of the peel force was used as the peel strength of the ceramic green sheet. Based on the peel strength of the ceramic green sheet, the releasability was evaluated according to the following criteria: A: Peel strength ≦ 0.15 N / 25 mm B: 0.15 N / 25 mm < peel strength ≦ 0.25 N / 25 mm C: Peel strength exceeds 0.25 N / 25 mm, or the ceramic green sheet breaks during peeling.

[0184] 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 1 to 4 and the neutralizing agent are the components used in the synthesis of the acrylic resin. Monomer 1 is -Si(R) ３ Monomer 2 refers to a monomer containing a reactive group (an acid group or a hydroxyl group), Monomer 3 refers to a monomer containing a polyalkylene oxide chain, and Monomer 4 refers to a monomer that does not fall under Monomers 1 to 3. In the table below, A / Y refers to the mass ratio of the acrylic resin content to the crosslinking agent content in the release layer-forming composition (acrylic resin content / crosslinking agent content).

[0185] The ratio (mass ratio) of the constituent units of each acrylic resin 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 having units (monomer 2) based on a monomer having a reactive group and a crosslinking agent, and since heating was performed during the formation of the release layer, it can be said that they have a crosslinked structure.

[0186]

[0187]

[0188] As shown in the table above, the release layer is -Si(R) ３ It was shown that when the composition contains an acrylic resin (specific acrylic resin) having a group represented by the formula (I), the composition exhibits excellent coatability with respect to a composition (ceramic slurry) containing an organic solvent, and also exhibits excellent releasability of a sheet (ceramic green sheet) formed on the surface of the release layer (Examples). A comparison of Examples 1 to 3 showed that when the thickness of the release layer is 120 nm or less, the releasability of a sheet (ceramic green sheet) formed on the surface of the release layer is even better (Examples 1 and 2). A comparison of Examples 1, 4 to 19, and 21 to 27, in which the release layer thickness is the same, showed that the surface free energy of the release layer surface was 17 mJ / m ２ 30mJ / m or more ２ It was shown that if the thickness is within the range of less than 1000 nm, the release properties of the sheet (ceramic green sheet) formed on the surface of the release layer are superior (Examples 1, 4 to 15, 17 to 19, and 21 to 27).

[0189] In contrast, the release layer is -Si(R) ３ When the composition did not contain an acrylic resin (specific acrylic resin) having a group represented by the formula (I), at least one of the coatability with respect to a composition (ceramic slurry) containing an organic solvent and the releasability of a sheet (ceramic green sheet) formed on the surface of the release layer was shown to be inferior (Comparative Example).

[0190] Example 28 A polyester film was produced in the same manner as in Example 1, except that protrusion-containing layer-forming composition X1 was replaced with protrusion-containing layer-forming composition X2. (Protrusion-containing layer-forming composition X2) 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 X2. - 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

[0191] The polyester film of Example 28 was subjected to the same performance evaluations (coating defects, ceramic slurry coatability, and peelability) as in Examples 1 to 27, and the results were similar to those of Example 1. The maximum protrusion height Sp of the release layer surface and the protrusion-containing layer surface of the polyester film obtained in Example 28 was measured under the same conditions as those used to measure the release layer surfaces of the polyester films of Examples 1 to 27. The average surface roughness Sa of the protrusion-containing layer surface was also measured under the same measurement conditions. The average surface roughness Sa was measured by taking five measurements at different measurement positions. The maximum protrusion height Sp of the release layer surface of the polyester film obtained in Example 28 was 8 nm, the average surface roughness Sa of the protrusion-containing layer surface was 2 nm, and the maximum protrusion height Sp of the protrusion-containing layer surface was 26 nm. The thermal shrinkage was also measured in the same manner as in Examples 1 to 27, and the thermal shrinkage in the conveyance direction was within the range of 1.29 to 1.61%, and the thermal shrinkage in the width direction was within the range of 0.83 to 1.03%.

[0192] REFERENCE SIGNS LIST 1 Polyester film 10 Polyester substrate 20 Release layer 21 One side 22 Other side (release layer surface, release surface)

Claims

1. A polyester film comprising a release layer and a polyester substrate, wherein the release layer is -Si(R) ３ The polyester film contains an acrylic resin having a group represented by the formula: ３ In the formula (I), each of the R's independently represents an alkyl group.

2. The acrylic resin is -O-Si(R) ３ The polyester film according to claim 1, wherein the polyester film has a group represented by the formula: ３ In the formula (I), each of the R's independently represents an alkyl group.

3. The acrylic resin is -Si[-O-Si(R) ３ ] ３ and -[Si(R) ２ -O]-Si(R) ３ The polyester film according to claim 1 or 2, wherein the —Si[—O—Si(R) ３ ] ３ , and -[Si(R) ２ -O]-Si(R) ３ In the formula (I), each of the R's independently represents an alkyl group.

4. The polyester film according to claim 1 or 2, wherein the maximum protrusion height Sp of the release layer surface is less than 35 nm.

5. The polyester film according to claim 1 or 2, wherein the maximum protrusion height Sp of the release layer surface is less than 15 nm.

6. The surface free energy of the release layer surface is 17 mJ / m ２ 30mJ / m or more ２ The polyester film according to claim 1 or 2, wherein the viscosity is less than 100 MPa.

7. The polyester film according to claim 1 or 2, wherein the release layer has a thickness of 120 nm or less.

8. The polyester film of claim 1 or 2, wherein the polyester substrate is substantially free of particles.

9. The polyester film according to claim 1 or 2, wherein the release layer has a crosslinked structure.

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

11. A method for producing a polyester film comprising a release layer and a polyester substrate, the method comprising the steps of: ３ The method for producing a polyester film includes a step of applying a release layer-forming composition, the release layer-forming composition including an acrylic resin having a group represented by the formula: ３ In the formula (I), each of the R's independently represents an alkyl group.

12. The method for producing a polyester film according to claim 11, further comprising the step of: obtaining a polyester substrate with a coating film by the coating step; and stretching the polyester substrate with the coating film.

13. The acrylic resin is -O-Si(R) ３ The method for producing a polyester film according to claim 11, wherein the polyester film has a group represented by the formula: ３ In the formula (I), each of the R's independently represents an alkyl group.

14. The method for producing a polyester film according to claim 11 or 12, wherein the acrylic resin has at least one group selected from the group consisting of an acid group, a hydroxyl group, and a polyalkylene oxide chain.

15. A method for producing a polyester film according to claim 11 or 12, comprising the steps of: the composition for forming a release layer contains a crosslinking agent; the acrylic resin has a reactive group capable of reacting with the crosslinking agent; and reacting the acrylic resin with the crosslinking agent.

16. A release agent comprising a water-soluble acrylic resin having a structural unit represented by formula (1) and a structural unit derived from acrylic acid or a salt thereof, or methacrylic acid or a salt thereof. In formula (1), R １１ is a hydrogen atom or a methyl group; L １１ is an alkylene group which may have a substituent, Rh is -Si(R) ３ Each of the multiple R's is independently an alkyl group.

17. The stripping agent according to claim 16, wherein the water-soluble acrylic resin has an acid value of 0.3 to 6.0 mmol / g.

18. The release agent according to claim 16 or 17, wherein the water-soluble acrylic resin further has a structural unit derived from an acrylic acid ester containing a polyalkylene oxide chain or a methacrylic acid ester containing a polyalkylene oxide chain.

Images