Method for producing polyester base material, and polyester film

Abstract

The problem addressed by the present invention is to provide a method for producing a polyester base material excellent in removability of the release layer when producing a polyester base material using a polyester film including a polyester base material and a release layer. The present invention also addresses the problem of providing a polyester film. A method for producing a polyester base material according to the present invention comprises bringing a polyester film, which comprises a polyester base material and a release layer that is disposed on at least one surface of the polyester base material, into contact with an alkaline aqueous solution having a pH of 11 or more and removing the release layer from the polyester film to obtain a polyester base material. The release layer contains a silicon atom and an amide bond.

Description

Method for manufacturing polyester substrate and polyester film

[0001] This invention relates to a method for producing a polyester substrate and a polyester film.

[0002] Polyester films are used in a wide range of applications due to their processability, mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. One application of polyester film is as a release film. Specifically, this involves creating a release layer on the surface of a polyester substrate, manufacturing various components on the surface of the release layer, and then peeling off those components.

[0003] In recent years, the recycling of polyester substrates contained in release films has been considered from the perspective of environmental protection. Patent Document 1 discloses the following method as such a recycling method. First, a release film is prepared having, in this order, a release layer obtained by curing a curable silicone resin, an easily soluble resin layer made of polyvinyl alcohol resin, and a polyester substrate. Next, a ceramic green sheet layer is formed on the release layer, and then the ceramic green sheet layer is peeled off the release film. Next, the release film after the ceramic green sheet layer has been peeled off is immersed in a hot water bath, thereby removing the release layer and the easily soluble resin layer from the release film and obtaining the polyester substrate.

[0004] Japanese Patent Publication No. 2004-050681

[0005] In the method described in Patent Document 1 above, it is necessary to sufficiently swell the easily soluble resin layer in order to remove the release layer. However, it may take a long time or a large amount of water to sufficiently swell the easily soluble resin layer. To address this problem, for example, means of adjusting the components contained in the release layer can be considered, but we have found that depending on the type of components contained in the release layer, it may not be possible to sufficiently remove the release layer, indicating room for improvement.

[0006] In view of the above circumstances, the present invention aims to provide a method for manufacturing a polyester substrate that offers excellent removeability of the release layer when manufacturing a polyester substrate using a polyester film containing a polyester substrate and a release layer. The present invention also aims to provide a polyester film.

[0007] The inventors of this invention have diligently studied and, as a result, completed the present invention. Specifically, they have found that the above problems can be solved by the following configuration.

[0008] [1] A method for producing a polyester substrate, comprising: contacting a polyester film containing a polyester substrate and a release layer disposed on at least one side of the polyester substrate with an alkaline aqueous solution with a pH of 11 or higher to remove the release layer from the polyester film, wherein the release layer contains silicon atoms and amide bonds. [2] The method for producing a polyester substrate according to [1], wherein the silicon atom content on the surface of the release layer is greater than 1.0 atm% and less than 15.0 atm%. [3] The method for producing a polyester substrate according to [1] or [2], wherein the nitrogen atom content on the surface of the release layer is greater than 0 atm% and less than 4.0 atm%. [4] The method for producing a polyester substrate according to any one of [1] to [3], wherein the pH of the alkaline aqueous solution is 13 or higher. [5] The method for producing a polyester substrate according to any one of [1] to [4], wherein the release layer has a crosslinked structure. [6] A polyester film comprising a polyester substrate and a release layer disposed on at least one side of the polyester substrate, wherein the release layer comprises silicon atoms and amide bonds, and the maximum shrinkage rate when the polyester film is heat-treated at 150°C for 30 minutes is greater than 0.20% and less than 2.00%. [7] The polyester film according to [6], wherein the release layer comprises siloxane bonds.

[0009] According to the present invention, when manufacturing a polyester substrate using a polyester film containing a polyester substrate and a release layer, a method for manufacturing a polyester substrate with excellent removeability of the release layer can be provided. Furthermore, according to the present invention, a polyester film can also be provided.

[0010] This is a schematic side view showing an example of a polyester film used in the method for manufacturing the polyester substrate of the present invention.

[0011] The present invention will now be described in detail. The following descriptions of the constituent elements may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0012] The following definitions are used to express the meaning of each term used in this specification. In this specification, a numerical range expressed using "~" means a range that includes the numbers before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this specification, the amount of each component in a composition means the total amount of multiple substances present in the composition if there are multiple substances corresponding to each component in the composition, unless otherwise specified. Also, in this specification, the amount of each component in each layer or component means the total amount of multiple substances present in each layer or component if there are multiple substances corresponding to each component in each layer or component, 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" means the longitudinal direction of the film during film manufacturing, and is synonymous with "conveying direction," "MD," and "machine direction." In this specification, "width direction" and "TD" mean the direction perpendicular to the longitudinal direction. In this specification, "orthogonal" is not limited to strictly orthogonal, but includes approximately orthogonal. "Approximately orthogonal" 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] Furthermore, in this specification, each component may be represented by a single substance or by a combination of two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of the combined substances unless otherwise specified.

[0015] In this specification, "(meth)acrylic" is a general term for acrylic and methacrylic, and means "one or more of acrylic and methacrylic." Similarly, "(meth)acrylate" means "one or more of acrylate and methacrylate," and "(meth)acrylic acid" means "one or more of acrylic acid and methacrylic acid." "Acrylic resin" means a resin containing constituent units derived from (meth)acrylate. In this specification, unless otherwise specified, refractive index means the refractive index for light with a wavelength of 550 nm, measured using an Abbe refractometer (NAR-2T, manufactured by Atago Co., Ltd.). In this specification, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are determined by gel permeation chromatography (GPC) analysis using columns of TSKgel GMHxL, TSKgel G4000HxL, TSKgel G2000HxL, and / or TSKgel Super HZM-N (all trade names of Tosoh Corporation), using THF (tetrahydrofuran) as the solvent, detection by differential refractometer, and conversion using polystyrene as the standard substance.

[0016] The content (mass %) of each constituent unit relative to the total units contained in the acrylic resin is used to measure the properties of the acrylic resin in proton nuclear magnetic resonance ( １ It is determined by analysis using the 1H-NMR method.

[0017] [Method for Manufacturing Polyester Substrate] The present invention provides a method for manufacturing a polyester substrate (hereinafter also referred to as "this manufacturing method"), which involves contacting a polyester film containing a polyester substrate and a release layer disposed on at least one side of the polyester substrate with an alkaline aqueous solution with a pH of 11 or higher to remove the release layer from the polyester film and obtain the polyester substrate, wherein the release layer contains silicon atoms and amide bonds.

[0018] This manufacturing method offers excellent removal of the peeling layer. Although the exact reason for this is unclear, it is presumed that the removal efficiency is improved by using a peeling layer containing easily hydrolyzable amide bonds and an alkaline aqueous solution with a pH of 11 or higher, which can increase the hydrolysis rate when removing the peeling layer. Furthermore, this manufacturing method allows for effective removal of the peeling layer without using large amounts of water, thus reducing the environmental impact.

[0019] [Polyester Film] Figure 1 is a schematic side view showing an example of a polyester film used in this manufacturing method. The polyester film 300 includes a polyester substrate 310 and a release layer 320. The polyester substrate 310 is arranged on the surface of one side 322 of the release layer 320. The other side 321 of the release layer 320 is the surface opposite to the side of the release layer 320 on which the polyester substrate 310 is arranged (i.e., the one side 322), and may be called the release layer surface or release surface.

[0020] <Polyester Substrate> A polyester substrate is a film-like material that contains polyester resin as its main component. Here, "main component" refers to the component that is present in the largest quantity (by mass) of all the components contained in the film-like material.

[0021] As the polyester substrate, a biaxially oriented polyester substrate is preferred. "Biaxial orientation" refers to the property of having molecular orientation in two axial directions. Molecular orientation is measured using a microwave transmission type molecular orientation meter (for example, MOA-6004, manufactured by Oji 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°. Molecular orientation changes by stretching, and a biaxially oriented polyester substrate can be manufactured by biaxial stretching.

[0022] It is preferable that the polyester substrate is substantially free of inorganic particles. "Substantially free of inorganic particles" is defined as a polyester substrate in which, when elements derived from inorganic particles are quantitatively analyzed by fluorescent X-ray analysis, the inorganic particle content is 50 ppm by mass or less relative to the total mass of the polyester substrate, preferably 10 ppm by mass or less, and more preferably below the detection limit. This is because even without actively adding inorganic particles to the polyester substrate, contaminants derived from foreign substances, raw material resin, or dirt adhering to the lines or equipment in the manufacturing process of the polyester substrate may detach and become mixed into the polyester substrate. Here, inorganic particles include inorganic particles that may be contained in the particle-containing layer (protrusion-containing layer) described later.

[0023] It is preferable that the polyester substrate is substantially particle-free. Examples of particles include the inorganic particles and organic particles mentioned above. Whether the polyester substrate is substantially particle-free is confirmed by the following procedure. Ten different locations on the cross-section of the polyester substrate are observed using a scanning electron microscope to check for 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 at any location, it means that particles are present in the release layer. On the other hand, if no particles are confirmed at any location on the cross-section, it means that the polyester substrate does not contain particles. Here, examples of organic particles include organic particles contained in the particle-containing layer (protrusion-containing layer) described later.

[0024] (Polyester Resin) The polyester resin contained in the polyester substrate is a polymer having ester bonds in its main chain. Polyester resins are usually formed by polycondensation of a dicarboxylic acid compound and a diol compound, as 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, with PET, PEN, and copolymers thereof being preferred, and PET being more preferred.

[0025] The intrinsic viscosity (IV) of the polyester film is preferably 0.50 dl / g or more and less than 0.80 dl / g, more preferably 0.55 dl / g or more and less than 0.70 dl / g, and even more preferably 0.60 dl / g or more and less than 0.70 dl / g. The intrinsic viscosity (IV) of the polyester film can be determined from the viscosity of the solution at 25°C after obtaining a solution by dissolving the polyester film in a 1,1,2,2-tetrachloroethane / phenol (= 2 / 3 [mass ratio]) mixed solvent. The amount of terminal carboxyl groups (terminal COOH amount, AV; Acid Value) of the polyester film is preferably 3.5 eq / ton or less, more preferably 3.0 eq / ton or less, and even more preferably 2.8 eq / ton or less. The lower the terminal COOH amount, the easier it is for the water content to decrease. The lower limit is, for example, 0.5 eq / ton or more. The amount of COOH at the end of the polyester film can be calculated by completely dissolving the polyester film in a mixed solvent of benzyl alcohol / chloroform (= 2 / 3; volume ratio), obtaining a solution, and then titrating it with a standard solution (0.01 N KOH-benzyl alcohol mixed solution) using phenol red as an indicator, and obtaining the titration volume. In this specification, "eq / ton" represents the molar equivalent per ton. The melting point (Tm) of the polyester resin is preferably 220 to 270°C, 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 polyester resin is not particularly limited, and known methods can be used. For example, polyester resin can be produced by polycondensation of at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.

[0027] The catalyst used in the production of the catalyst polyester resin is not particularly limited, and any known catalyst usable for the synthesis of polyester resin can be used. Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds or aluminum compounds are preferred because they are less likely to generate foreign matter and voids in the polyester substrate. Only one type of catalyst may be used, or two or more types may be used in combination. It is also preferable to use at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds in combination with a phosphorus compound. When using multiple catalysts, it is preferable to adopt the types and contents of each compound described in paragraphs

[0055] to

[0062] of Japanese Patent No. 5575671. In a polyester film, when the titanium compound content is 5 to 15 ppm by mass in terms of Ti element, the magnesium compound content is preferably 60 to 90 ppm by mass in terms of Mg element, and the phosphorus compound content is preferably 5 to 35 ppm by mass in terms of P element.

[0028] As the titanium compound, an organic chelate titanium complex is preferred. An 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. As the titanium compound, the 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. The titanium compound content is preferably 1 to 300 ppm by mass, more preferably 3 to 20 ppm by mass, and even more preferably 5 to 15 ppm by mass, based on the total mass of the polyester film in terms of Ti element value.

[0029] Examples of aluminum compounds include organoaluminum compounds and their partial hydrolysates. Preferred organoaluminum compounds are carboxylates, inorganic acid salts, or chelate compounds, with aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum chloride hydroxide, or aluminum acetylacetonate being more preferred.

[0030] When the polyester substrate contains an antimony compound (e.g., antimony trioxide) as a catalyst, when the release layer is removed by contacting the release layer with an alkaline aqueous solution, the antimony trioxide in the polyester substrate releases antimonate ions (H ２ SbO ３ － ) may change and be released into the environment. Therefore, from the viewpoint of reducing environmental impact, the antimony compound content is preferably 0 to 150 ppm by mass, more preferably 0 to 100 ppm by mass, and even more preferably 0 to 80 ppm by mass, based on the total mass of the polyester film in terms of Sb element. In particular, the antimony compound content is preferably 0 to 30 ppm by mass, more preferably 0 to 10 ppm by mass, and even more preferably 0 to 1 ppm by mass, based on the total mass of the polyester film in terms of Sb element.

[0031] The content of each element can be measured by inductively coupled plasma mass spectrometry (ICP-MS). The Agilent 7800 ICP-MS analyzer from Agilent Technologies can be used.

[0032] Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or methyl aromatic dicarboxylic acids are preferred.

[0033] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, dimer acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of alicyclic dicarboxylic acid compounds include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

[0034] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfisoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorenic acid. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, and terephthalic acid is more preferred.

[0035] Dicarboxylic acid compounds may be used individually or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or copolymerized with other aromatic dicarboxylic acids or aliphatic dicarboxylic acids such as isophthalic acid.

[0036] Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0037] Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred. Examples of alicyclic diol compounds include cyclohexanedimethanol, spiroglycol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. Diol compounds may be used individually or in combination of two or more.

[0038] • In the manufacture of polyester resin with end encapsulants, end encapsulants may be used as needed. By using end encapsulants, structures derived from the end encapsulants are introduced to the ends of the polyester resin. The end encapsulants are not limited, and known end encapsulants can be used. Examples of end encapsulants include oxazoline compounds, carbodiimide compounds, and epoxy compounds. For end encapsulants, refer to paragraphs

[0055] to

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

[0039] • Manufacturing 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, and more preferably 275 to 285°C. The pressure is not limited and may be set appropriately depending on the raw materials. The pressure is 1.33 × 10⁻⁶ －３~1.33 x 10 －５ MPa is preferred, 6.67 × 10 －４ ~6.67 x 10 －５ MPa is more preferable.

[0040] As a method for synthesizing polyester resin, the method described in paragraphs

[0033] to

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

[0023] to

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

[0041] The polyester resin content in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polyester substrate. The upper limit of the polyester resin content is not limited and can be appropriately set within a range of less than 100% by mass of the total mass of the polyester substrate.

[0042] When the polyester substrate contains polyethylene terephthalate, the polyethylene terephthalate content is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 100% by mass, relative to the total mass of polyester resin in the polyester substrate.

[0043] The polyester substrate may contain components other than polyester resin (for example, catalysts, unreacted raw material components, particles, and water).

[0044] 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, even more preferably 40 μm or less, and particularly preferably 35 μm or less. There is no particular lower limit to the thickness, but in terms 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 the arithmetic mean of the thicknesses of five points in the polyester substrate in a section prepared having a cross-section perpendicular to the main surface of the polyester film, measured using a scanning electron microscope (SEM) or transmission electron microscope (TEM).

[0045] <Release Layer> The polyester film has a release layer. The release layer contains silicon atoms and amide bonds. The release layer is formed, for example, as a layer constituting the release surface of the polyester film. After a member such as a ceramic green sheet is formed on the release surface of the polyester film, it is peeled off from the release surface. The release layer may be provided in contact with the polyester substrate without other layers in between, or it may be provided via other layers. It is preferable that the release layer is in contact with the polyester substrate. It is preferable that the release layer is the outermost layer of the polyester film. That is, it is preferable that the surface of the release layer is the release surface.

[0046] The release layer preferably contains a release agent. The release agent is not particularly limited and examples include silicone resins, fluororesins, alkyd resins, acrylic resins, urethane resins, various waxes, and aliphatic olefins. When the polyester film is a release film for manufacturing ceramic green sheets, as described later, silicone resins, acrylic resins, or urethane resins are preferred in terms of the release properties of the ceramic green sheet, and acrylic resins or urethane resins are more preferred.

[0047] (Acrylic resin) The acrylic resin contained in the release layer may be either crosslinked or non-crosslinked. The acrylic resin contained in the release layer is preferably a crosslinked product formed by a reaction between an acrylic resin A having a reactive group A and a crosslinking agent B having a reactive group B capable of reacting with the reactive group A, from the viewpoint of obtaining more excellent release properties of the release surface.

[0048] Also, the acrylic resin contained in the release layer is -Si(R) ３ preferably has a structure represented by , and -Si(R) in the side chain ３ more preferably has a structure represented by . -Si(R) ３ wherein each R independently represents an alkyl group or an aryl group. Examples of the alkyl group for R include linear alkyl groups having 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms), branched alkyl groups having 3 to 12 carbon atoms (preferably 3 to 6 carbon atoms), and cyclic alkyl groups. The number of carbon atoms in the aryl group for R is preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 12. Among these, R is preferably an alkyl group from the viewpoint of more excellent release properties of the release surface, more preferably a linear alkyl group having 1 to 5 carbon atoms, still more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, an isopropyl group, an isobutyl group, or a tert-butyl group, and particularly preferably a methyl group, an ethyl group, a propyl group, or an n-butyl group. A plurality of R groups may be the same or different.

[0049] Also, the acrylic resin contained in the release layer preferably has a silicon atom, and more preferably has a siloxane bond. The siloxane bond is -[O-Si(R) ２ - is preferably a structure represented by . -[O-Si(R) ２ - R in has the same definition as R in -Si(R) ３ , including preferred embodiments. The acrylic resin more preferably has two or more siloxane bonds. From the viewpoint of more excellent release properties of the release surface, the acrylic resin further preferably has a linear polysiloxane structure. The linear polysiloxane structure is -[Si(R) ２ -O] ｍThe structure is represented by -. R and m are, including in preferred embodiments, the above-mentioned -Si(R) ３ In the structure represented by -Si(R), m is synonymous with R, and m represents an integer of 2 or more. Among them, acrylic resin is -Si(R) ３ It is particularly preferable to have both a siloxane bond and a siloxane bond. -Si(R) ３ And as for structures having a siloxane bond, -Si[-O-Si(R) ３ ] ｎ R ３－ｎ A structure represented by -[Si(R) ２ -O] ｍ -Si(R) ３ At least one selected from the group consisting of structures represented by -[Si(R) ２ -O] ｍ -Si(R) ３ A structure represented by is more preferred. R and m are the same as R and m above, including in the preferred embodiment. n is 2 or 3 (preferably 3). As described above, -Si(R) ３ The acrylic resin having at least one (more preferably both) of the siloxane bond may or may not be crosslinked, but it is preferable that it is a crosslinked product of acrylic resin A and crosslinking agent B. In this case, the release layer can be said to be a crosslinked film having a crosslinked structure.

[0050] The following provides a more detailed explanation of the crosslinked product of acrylic resin A and crosslinking agent B.

[0051] Acrylic resin A Acrylic resin A is a compound that contains constituent units derived from (meth)acrylate and has a reactive group A. Examples of reactive group A in acrylic resin A include a reactive group comprising at least one selected from the group consisting of a carboxyl group, a carboxylic acid anhydride group, a carboxylic acid base, and a hydroxyl group. A carboxyl group or a carboxylic acid base, which is a salt of a carboxyl group, is preferred as the reactive group A because it provides better peelability of the peeled surface.

[0052] Acrylic resin A is -Si(R) ３Preferably, it has at least one of the siloxane bond, and -Si(R) ３ It is more preferable to have both -Si(R) and siloxane bonds. ３ For specific examples and preferred embodiments of the siloxane bond, please refer to the -Si(R) bond present in the above-mentioned acrylic resin. ３ And it is similar to a siloxane bond. Thus, -Si(R) ３ By using acrylic resin A having at least one of the siloxane bonds, the release layer will contain silicon atoms. Furthermore, by using acrylic resin A containing siloxane bonds, the release layer will contain siloxane bonds.

[0053] The constituent unit acrylic resin A derived from monomer A1 preferably contains constituent units derived from monomer A1, which is an acrylic monomer having a siloxane bond. The above acrylic monomer refers to a concept that includes both (meth)acrylic acid ester and (meth)acrylic acid. (Meth)acrylic acid refers to a concept that includes methacrylic acid and acrylic acid. Monomer A1 is preferably a (meth)acrylic acid ester having a siloxane bond. Also, monomer A1 is -Si(R) ３ It is also preferable that the monomer A1 has a group represented by -Si[-O-Si(R) ３ ] ｎ R ３－ｎ A group represented by -[Si(R) ２ -O] ｍ -Si(R) ３ Preferably, it has at least one group selected from the group consisting of groups represented by -[Si(R) ２ -O] ｍ -Si(R) ３ It is more preferable to have a group represented by . R, n, and m are as described above.

[0054] The molecular weight of monomer A1 is preferably 5000 or less, more preferably 4000 or less, and even more preferably 3000 or less, in terms of superior peelability of the peeled surface. The lower limit is often 100 or more, preferably 500 or more, and more preferably 700 or more. The molecular weight of monomer A1 can be measured by MALDI-MS (matrix-assisted laser desorption / ionization mass spectrometry). Here, if monomer A1 is a mixture of monomers with different molecular weights, the peak with the highest intensity detected by the MS spectrum (mass spectrometry) is read, and that molecular weight is taken as the molecular weight of monomer A1.

[0055] The monomer A1 is preferably a compound represented by the following formula (A1-1): CH ２ = C(R １１ )C(O)O-L １１ -Rh (A1-1)

[0056] In formula (A1-1), R １１ This is either a hydrogen atom or a methyl group.

[0057] In formula (A1-1), L １１ L is an alkylene group which may have substituents. １１ The alkylene group in this compound may be linear, branched, or cyclic, but linear or branched is preferred, and linear is more preferred. １１ The number of carbon atoms in the alkylene group is preferably 1 to 10, more preferably 1 to 7, and even more preferably 1 to 5. Specific examples of substituents that the alkylene group may have include halogen atoms, alkoxy groups (preferably with 1 to 5 carbon atoms), and carboxyl groups. Among these, L １１ The alkylene group is preferably one without substituents, and a propylene group, an ethylene group, or a methylene group is more preferable.

[0058] In formula (A1-1), Rh is a substituent having a siloxane bond. Rh is -Si(R) ３ It is also preferable to have one or more groups represented by . In particular, Rh is -Si[-O-Si(R) ３ ] ｎ R３－ｎ A group represented by, or -[Si(R) ２ -O] ｍ -Si(R) ３ It is preferable that the group is represented by -[Si(R) ２ -O] ｍ -Si(R) ３ It is more preferable that the group be represented by . R, n, and m are as described above.

[0059] Specific examples of monomer A1 include organosilyl group-containing monomers such as (meth)acrylate 3-[tris(trimethylsilyloxy)silyl]propyl, Cyraprene FM-0711 (manufactured by JNC Corporation), Cyraprene FM-0721 (manufactured by JNC Corporation), Cyraprene FM-0725 (manufactured by JNC Corporation), Cyraprene 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.).

[0060] When acrylic resin A has constituent units derived from monomer A1, the content of constituent units derived from monomer A1 is preferably 10 to 90% by mass, more preferably 15 to 85% by mass, and even more preferably 20 to 80% by mass, relative to the total constituent units (100% by mass) of acrylic resin A. If the content of constituent units derived from monomer A1 is 10% by mass or more, the peelability of the sheet formed on the surface of the release layer is better. Furthermore, if the content of constituent units derived from monomer A1 is 90% by mass or less, the coating properties of the composition containing organic solvents are better.

[0061] The acrylic resin A, which is a constituent unit derived from monomer A2, preferably contains a constituent unit derived from monomer A2 that includes at least one of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid base. This improves the water solubility and curability of the resin. It is preferable that monomer A2 does not have a siloxane bond. When acrylic resin A contains a constituent unit derived from monomer A2, a crosslinked product of acrylic resin A and crosslinking agent B can be formed by the reaction of at least one selected from the group consisting of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid base with a crosslinking agent B (preferably the reactive group B described later). Examples of carboxylic acid anhydride groups include groups based on acid anhydrides such as maleic anhydride and itaconic anhydride. Examples of carboxylic acid bases include alkali metal salts of carboxyl groups, organic amine salts of carboxyl groups, and ammonium salts of carboxyl groups.

[0062] Examples of monomer A2 include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid, and their salts (e.g., sodium salts, potassium salts, ammonium salts, and tertiary amine salts); monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; and (meth)acrylic acid esters having a carboxyl group or a carboxylic acid base.

[0063] Specific examples of (meth)acrylic acid esters having a carboxyl group or a carboxylic acid base include carboxyl group-containing (meth)acrylic acid esters such as 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, and ω-carboxy-polycaprolactone monoacrylate.

[0064] When acrylic resin A has constituent units derived from monomer A2, the content of constituent units derived from monomer A2 is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass, relative to the total constituent units (100% by mass) of acrylic resin A. If the content of constituent units derived from monomer A2 is 5% by mass or more, the water solubility and curability of the resin are improved. Furthermore, if the content of constituent units derived from monomer A2 is 30% by mass or less, the release properties of the sheet formed on the surface of the release layer are improved.

[0065] ...The constituent units of acrylic resin A derived from other monomers may have constituent units derived from monomers other than monomers A1 to A2 (hereinafter also referred to as "other monomers").

[0066] Another specific example of a monomer is a (meth)acrylic acid ester containing a polyalkylene oxide chain. Specific examples of polyalkylene oxide chains include polymethylene oxide, polyethylene oxide, polypropylene oxide, and polybutylene oxide. The number of repeating units in the polyalkylene oxide chain is preferably 3 to 100.

[0067] Examples of (meth)acrylic acid esters containing polyalkylene oxide chains include methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate.

[0068] Specific examples of monomers other than (meth)acrylic acid esters containing polyalkylene oxide chains include: hydroxyl group-containing monomers such as 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol monomethacrylate, and 4-hydroxybutyl (meth)acrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; sulfonic acid group-containing monomers such as styrene sulfonic acid and their salts; phosphate group-containing monomers such as 2-methchloroyloxyethyl acid phosphate and their salts; Examples of amide group-containing monomers include (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N,N-dialkyl(meth)acrylate (examples of alkyl groups: methyl group, ethyl group, n-butyl group, isobutyl group, etc.), acryloylmorpholine, N-methylol(meth)acrylamide, N-isopropylacrylamide, diacetone acrylamide, and N-phenyl(meth)acrylamide; vinyl isocyanates, allyl isocyanates, vinyl methyl ethers, vinyl ethyl ethers, vinyl trialkoxysilanes, alkyl maleic acid monoesters, alkyl fumaric acid monoesters, alkyl itaconic acid monoesters, (meth)acrylonitrile vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene.

[0069] When acrylic resin A has constituent units derived from other monomers, the content of constituent units derived from other monomers is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 5 to 15% by mass, relative to the total constituent units (100% by mass) of acrylic resin A.

[0070] ...Preferred embodiments of acrylic resin A One preferred embodiment of acrylic resin A is an embodiment that includes constituent units derived from monomer A1 and constituent units derived from monomer A2, and more preferably an embodiment that includes constituent units derived from monomer A1, constituent units derived from monomer A2, and constituent units derived from other monomers.

[0071] The acid value of acrylic resin A is preferably 0.3 to 6.0 mmol / g, more preferably 0.5 to 4.5 mmol / g, even more preferably 0.5 to 3.0 mmol / g, and particularly preferably 0.5 to 2.5 mmol / g. The hydroxyl value of acrylic resin A is preferably 0 to 3.0 mmol / g, more preferably 0 to 2.5 mmol / g, and even more preferably 0 to 2.0 mmol / g. If the acid value or hydroxyl value is above the above lower limit, the water solubility and curability of acrylic resin A are better. If the acid value or hydroxyl value is below the above lower limit, the peelability of the peeled surface is better.

[0072] The weight-average molecular weight (Mw) of acrylic resin A is preferably 5,000 to 100,000, more preferably 7,000 to 80,000, and even more preferably 10,000 to 50,000. If the Mw of acrylic resin A is 5,000 or higher, the suitability for coating and manufacturing the release layer is better. Furthermore, if the Mw of acrylic resin A is 100,000 or lower, the peelability of the release surface is better. The weight-average molecular weight (Mw) of acrylic resin A is measured by gel permeation chromatography (GPC).

[0073] Acrylic resin A may consist of only one type or two or more types. The content of acrylic resin A is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 50 to 80% by mass, based on the total mass of the release layer. When the release layer contains a crosslinked product of acrylic resin A and crosslinking agent B described later, it is preferable that the content of the structure derived from acrylic resin A satisfies the above range.

[0074] Crosslinking agent B Crosslinking agent B is a compound having a reactive group B that can react with the reactive group A of acrylic resin A. Crosslinking agent B is preferably water-soluble in order to easily form a release layer by in-line coating. A crosslinked product of acrylic resin A and crosslinking agent B can be formed, for example, by the reaction between the reactive group A of acrylic resin A and the reactive group B of crosslinking agent B when forming a release layer using a composition containing acrylic resin A and crosslinking agent B.

[0075] When acrylic resin A has a carboxyl group, a carboxylic acid anhydride group, or a carboxylic acid base, the reactive group B is preferably an oxazoline group, a carbodiimide group, an isocyanate group, or a blocked isocyanate group, as these have excellent reactivity with the carboxyl group, etc. Among these, the oxazoline group or the carbodiimide group is more preferred, and the oxazoline group is even more preferred, as it provides superior peelability of the peeled surface. Here, a blocked isocyanate group means a group in which an isocyanate group has been blocked by a blocking agent (for example, a compound having an active hydrogen group).

[0076] The crosslinking agent B having the reactive group B is not particularly limited, and examples include one or more crosslinking agents selected from the group consisting of oxazoline compounds, isocyanate compounds, and carbodiimide compounds. The isocyanate compound may be a compound having a blocked isocyanate group in which the isocyanate group is blocked by a blocking agent. Among these, oxazoline compounds or carbodiimide compounds are preferred in that they have better peelability of the peeled surface, and oxazoline compounds are more preferred.

[0077] For example, if acrylic resin A has a carboxyl group as reactive group A, and crosslinking agent B has an oxazoline group as reactive group B, an amide bond is formed by the reaction between the carboxyl group and the oxazoline group, thus obtaining a release layer having an amide bond. The amide bond formed by the reaction between the carboxyl group and the oxazoline group is -CO(O)-L ｂ１ In many cases, the amide bond originates from the -NH-C(O)- structure. ｂ１ L indicates an alkylene group. ｂ１ The alkylene group is preferably an alkylene group having 1 to 6 carbon atoms, more preferably a methylene group, an ethylene group, or a propylene group, and even more preferably an ethylene group. That is, the release layer is -CO(O)-L ｂ１ Preferably, it contains an NH-C(O)- structure, and is more likely to contain a CO(O)-CH ２ CH ２ It is more preferable to include an NH-C(O)- structure.

[0078] ...Oxazoline compounds The oxazoline compounds are not particularly limited as long as they are compounds having an oxazoline group, and may be low molecular weight compounds with a weight-average molecular weight (Mw) of 1000 or less, or high molecular weight compounds with a weight-average molecular weight (Mw) of more than 1000, but high molecular weight compounds are preferred in that they have superior peelability of the peeled surface.

[0079] 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), and 2,2'-trimethylene-bis- Examples include (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.

[0080] When the oxazoline compound is a polymer compound, it can be any polymer compound having an oxazoline group, for example, a copolymer containing the above-mentioned low-molecular-weight compound having an oxazoline group as a constituent unit.

[0081] The polymer compound having an oxazoline group is preferably an acrylic resin having an oxazoline group, and more preferably an acrylic resin containing both an oxazoline group and a polyalkylene oxide chain. The inclusion of a polyalkylene oxide chain in the polymer compound having an oxazoline group improves the water solubility of crosslinking agent B, resulting in superior in-line coating suitability.

[0082] Examples of polyalkylene oxide chains include polymethylene oxide, polyethylene oxide, polypropylene oxide, and polybutylene oxide. The repeating units of the polyalkylene oxide chain are preferably 3 to 100.

[0083] Examples of (meth)acrylic acid esters containing polyalkylene oxide chains include methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate.

[0084] The polymer compound having an oxazoline group may also contain structural units derived from the low molecular weight compound having the oxazoline group, and structural units derived from other monomers other than those derived from (meth)acrylic acid esters containing polyalkylene oxide chains.

[0085] 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; hydroxyl-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (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, potassium 3-sulfopropyl methacrylate, 2-acrylamide Examples include sulfo group-containing monomers such as mido-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 alkyl groups: 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, butadiene, and the compound represented by the above formula (A1-1). Among these, the compound represented by the above formula (A1-1) is preferred as the other monomer because it exhibits superior peelability of the peeled surface.

[0086] High-molecular-weight compounds containing oxazoline groups are preferably water-soluble from an environmental perspective.

[0087] The weight-average molecular weight (Mw) of the polymer compound having an oxazoline group is not particularly limited, but is preferably 3000 or more, more preferably 5000 to 200000, and even more preferably 7000 to 150000. The weight-average molecular weight (Mw) is measured according to the method for measuring the weight-average molecular weight of acrylic resins.

[0088] The polymer compound having an oxazoline group may be a commercially available product. Examples of commercially available products include Epocross (registered trademark, hereinafter the same) K-2010E, Epocross K-2020E, Epocross K-2030E, Epocross WS-700, and Epocross WS-300 (all manufactured by Nippon Shokubai Co., Ltd.).

[0089] ...Isocyanate compounds Isocyanate compounds are compounds having an isocyanate group or a blocked isocyanate group. Blocked isocyanate compounds (i.e., compounds having a blocked isocyanate group) are preferred. Blocked isocyanate compounds are compounds in which the isocyanate group of a polyisocyanate is protected (i.e., blocked) with a blocking agent, and are included in isocyanate compounds in this specification. Examples of blocking agents in blocked isocyanates include ester compounds, phenol compounds, alcohol compounds, oxime compounds, mercaptan compounds, lactam compounds, amine compounds, acid amide compounds, pyrazole compounds, triazole compounds, and bisulfite compounds.

[0090] Carbodiimide compounds are compounds having a carbodiimide group. Carbodiimide compounds can be synthesized by conventionally known methods. For example, the condensation reaction of diisocyanate compounds is used. The diisocyanate compound is not particularly limited and may be any of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Specific examples of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates are the same as the specific examples of diisocyanates described in the section on isocyanate compounds. The carbodiimide equivalent (mass [g] of the carbodiimide compound to give 1 mole of carbodiimide group) is preferably 100 to 1000 g / mol, more preferably 250 to 800 g / mol, and even more preferably 300 to 700 g / mol.

[0091] ...Preference embodiment of crosslinking agent B The crosslinking agent B is preferably an acrylic resin having a reactive group B in its side chain, in that it is superior in terms of peelability of the peeled surface. Specific examples of acrylic resins having a reactive group B in its side chain include the above-mentioned polymer compounds having an oxazoline group (specifically, copolymers comprising a structural unit derived from the above-mentioned low-molecular-weight compound having an oxazoline group and a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain), and the above-mentioned polymer compounds having an epoxy group (specifically, copolymers comprising a structural unit derived from a compound having an epoxy group and a structural unit derived from a (meth)acrylic acid ester containing a polyalkylene oxide chain). Among these, the acrylic resin having a reactive group B in its side chain is preferably the above-mentioned polymer compound having an oxazoline group, in that it is superior in terms of peelability of the peeled surface.

[0092] The crosslinking agent B may be of one type or of two or more types. The content of crosslinking agent B is preferably 1 to 80% by mass, more preferably 1 to 70% by mass, even more preferably 1 to 60% by mass, and still more preferably 10 to 50% by mass, relative to the total mass of the release layer, in terms of the reactivity of the acrylic resin A. When the release layer contains a crosslinked product of acrylic resin A and crosslinking agent B described later, it is preferable that the content of the structure derived from crosslinking agent B satisfies the above range.

[0093] - Preferred embodiment of the crosslinked body: The release layer preferably contains a crosslinked body of acrylic resin A having siloxane bonds and crosslinking agent B. In particular, it is more preferable that the acrylic resin A having siloxane bonds is in the above preferred embodiment, and that at least one of the above preferred embodiment is the case where the acrylic resin A having siloxane bonds is in the above preferred embodiment and the crosslinking agent B is in the above preferred embodiment.

[0094] When the release layer contains a crosslinked acrylic resin A and crosslinking agent B, the content of the crosslinked acrylic resin A and crosslinking agent B is preferably 98 to 100% by mass, and more preferably 98.5 to 100% by mass, relative to the total mass of the release layer, in terms of having superior release properties of the release surface.

[0095] (Urethane Resin) The urethane resin included in the release layer is not limited as long as it is a polymer having a urethane bond in its main chain, and known urethane resins such as the reaction product of polyol and polyisocyanate described later can be used. Here, a urethane bond (-O-C(O)NH-) can be said to be a bond that includes both an amide bond (-NH-C(O)-) and an ester bond (-C(O)O-). Therefore, in this specification, when a urethane bond is present, it is assumed that an amide bond is present. Thus, it can be said that a release layer containing urethane resin contains an amide bond.

[0096] The urethane resin preferably has silicon atoms, preferably has siloxane bonds, and also -Si(R) ３ It is more preferable to have a structure represented by a siloxane bond and -Si(R) ３It is more preferable to have both of the structures represented by . The siloxane bond in the urethane resin is synonymous with the siloxane bond in the acrylic resin, including in the preferred embodiment. -Si(R) in the urethane resin ３ The structure represented by also includes, in preferred embodiments, the acrylic resin possesses -Si(R) ３ This is synonymous with the structure represented by . Thus, -Si(R) ３ By using a urethane resin having at least one of the siloxane bonds, the release layer will contain silicon atoms. Furthermore, by using a urethane resin containing siloxane bonds, the release layer will contain siloxane bonds.

[0097] A urethane resin having siloxane bonds may have siloxane bonds in the main chain of the urethane resin, or it may have siloxane bonds in the side chains of the urethane resin. It is preferable that the siloxane bonds be in the side chains of the urethane resin because the siloxane bonds tend to localize on the surface. Examples of urethane resins having siloxane bonds include reaction products of a polyol, a polyisocyanate, and a compound having a reactive functional group and a siloxane structure (hereinafter also referred to as a "reactive silicone compound").

[0098] Examples of polyols include polyether polyols, polyester polyols, polycaptolactone polyols, polycarbonate polyols, and acrylic polyols. Examples of polyester polyols include polycondensates of dibasic acids such as terephthalic acid, adipic acid, and succinic acid with polyols such as ethylene glycol, polyoxyethylene glycol, and 1,6-hexanediol. Examples of polycaprolactone polyols include compounds obtained by ring-opening polymerization of polyols using captolactones such as ε-caprolactone as initiators. Examples of polycarbonate polyols include reaction products of glycols such as ethylene glycol, 1,6-hexanediol, and bisphenol A with carbonates such as ethylene carbonate and diphenyl carbonate. Examples of acrylic polyols include copolymers of acrylic acid derivatives containing hydroxyl groups, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxybutyl acrylate, with acrylic acid, methacrylic acid, and acrylic acid esters.

[0099] Any compound having two or more isocyanate groups in one molecule can be used as the polyisocyanate. Examples include monomers such as hexamethylene diisocyanate, trimethylene diisocyanate, 1,4-cyclohexane diisocyanate, bis(4-isocyanatophenyl)methane, toluene-2,4-diisocyanate, 4,4'-toluene diisocyanate, p-phenylenediisocyanate, m-phenylenediisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 4,4'-diphenyl isocyanate. In addition, polymers such as dimers, biuretes, and isocyanurates derived from the above monomers, as well as adducts obtained by adding a polyisocyanate monomer to a low molecular weight polyol such as trimethylolpropane, can also be used. As for the polyisocyanate, compounds having two isocyanate groups in the molecule are preferred because the reaction can be easily controlled.

[0100] The reactive silicone compound used in the synthesis of urethane resins having siloxane bonds is a compound having a reactive functional group and a siloxane structure that reacts with a polyol or polyisocyanate. The siloxane bond in the reactive silicone compound is synonymous with the siloxane bond in acrylic resin, including in preferred embodiments. The reactive silicone compound is -Si(R) ３ It is preferable to further have the structure represented by . The reactive silicone compound has -Si(R) ３ The structure represented by, including preferred embodiments, is a structure in which the acrylic resin possesses -Si(R) ３ This is synonymous with the structure represented by .

[0101] The reactive functional groups of the reactive silicone compound can be those that react with polyols or polyisocyanates, such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups. The reactive functional groups react with the hydroxyl groups of the polyol or the isocyanate groups of the polyisocyanate to obtain a urethane resin having siloxane bonds.

[0102] Examples of reactive silicone compounds include amino-modified silicones (such as "DOWSILBY16-205" and "DOWSILFZ-3760" from Dow Toray Industries, Inc., and "X-22-161A" and "PAM-E" from Shin-Etsu Chemical Co., Ltd.), and epoxy-modified silicones (such as "DOWSILBY16-839Fluid" and "DOWSILSF8" from Dow Toray Industries, Inc.) Examples include "421 Fluid," "X-22-163" and "KF-105" manufactured by Shin-Etsu Chemical Co., Ltd., and hydroxyl-modified silicones ("DOWSILBY16-201" and "DOWSILSF8427 Fluid" manufactured by Dow Toray Industries, Ltd., "X-22-176DX" and "X-22-176F" manufactured by Shin-Etsu Chemical Co., Ltd., and "Cylaplane® FM DA-26" and "Cylaplane FM DA-11" manufactured by JNC Corporation).

[0103] In a urethane resin having siloxane bonds, the content of the portion constituting the siloxane bonds is preferably 0.1 to 50% by mass, and more preferably 0.1 to 30% by mass, relative to the total mass of the urethane resin having siloxane bonds. The above content is set appropriately in consideration of the peelability of the peel surface and the ease of forming the peel layer.

[0104] The urethane resin can be manufactured by known methods using the above components. Known catalysts such as organometallic compounds and tertiary amine compounds can be used in the manufacture of the urethane resin. The release layer forming composition used in the manufacture of the release layer containing the urethane resin is preferably an aqueous dispersion of the urethane resin. The aqueous dispersion of the urethane resin is preferably further containing neutralizing agents such as amines and ammonia, as this improves the water dispersibility of the urethane resin.

[0105] The urethane resin contained in the release layer may or may not be crosslinked. Preferably, the urethane resin contained in the release layer is a crosslinked material formed by the reaction of a urethane resin C having a reactive group C and a crosslinking agent D having a reactive group D that can react with the reactive group C, in order to obtain superior release properties of the release surface. In this case, the release layer can be said to be a crosslinked film having a crosslinked structure.

[0106] The urethane resin C is a compound having a urethane bond in its main chain and a reactive group C. The reactive group C of the urethane resin C is, including in preferred embodiments, synonymous with the reactive group A of the acrylic resin A. The urethane resin C is -Si(R) ３ Preferably, it has at least one of the siloxane bond, and -Si(R) ３ It is more preferable to have both and siloxane bonds. The urethane resin C has -Si(R) ３ For specific examples and preferred embodiments of the siloxane bond, please refer to the -Si(R) bond present in the above-mentioned acrylic resin. ３ And it is similar to a siloxane bond.

[0107] The urethane resin C may contain only one type or two or more types. The content of urethane resin C is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 50 to 80% by mass, based on the total mass of the release layer. When the release layer contains a crosslinked product of urethane resin C and crosslinking agent D, it is preferable that the content of the structure derived from urethane resin C satisfies the above range.

[0108] The crosslinking agent D is a compound having a reactive group D that can react with the reactive group C of the urethane resin C. The crosslinking agent D is preferably water-soluble, as this facilitates the formation of a release layer by in-line coating. A crosslinked product of the urethane resin C and the crosslinking agent D can be formed, for example, by the reaction between the reactive group C of the urethane resin C and the reactive group D of the crosslinking agent D when forming a release layer using a composition containing the urethane resin C and the crosslinking agent D.

[0109] When the urethane resin C has a carboxyl group, a carboxylic acid anhydride group, or a carboxylic acid base, the reactive group D is preferably an oxazoline group, a carbodiimide group, an isocyanate group, or a blocked isocyanate group, as these have excellent reactivity with the carboxyl group, etc. Among these, the oxazoline group or the carbodiimide group is more preferable, and the oxazoline group is even more preferable, as these have superior peelability of the peeled surface.

[0110] The crosslinking agent D having the reactive group D is not particularly limited, and examples include one or more crosslinking agents selected from the group consisting of oxazoline compounds, isocyanate compounds, and carbodiimide compounds. The isocyanate compound may also be a compound having a blocked isocyanate group. Among these, oxazoline compounds or carbodiimide compounds are preferred in that they have better peelability of the peeled surface, and oxazoline compounds are even more preferred. For example, when the urethane resin C has a carboxyl group as the reactive group C, and the crosslinking agent D has an oxazoline group as the reactive group D, an amide bond is formed by the reaction between the carboxyl group and the oxazoline group, so a peeled layer having an amide bond is obtained. The amide bond formed by the reaction between the carboxyl group and the oxazoline group is -CO(O)-Lｂ１ In many cases, the amide bond originates from the -NH-C(O)- structure. ｂ１ L indicates an alkylene group. ｂ１ The alkylene group is preferably an alkylene group having 1 to 6 carbon atoms, more preferably a methylene group, an ethylene group, or a propylene group, and even more preferably an ethylene group. That is, the release layer is -CO(O)-L ｂ１ Preferably, it contains an NH-C(O)- structure, and is more likely to contain a CO(O)-CH ２ CH ２ It is more preferable to include an NH-C(O)- structure.

[0111] Details and preferred embodiments of the oxazoline compounds, isocyanate compounds, and carbodiimide compounds are as described above.

[0112] The release layer preferably contains a crosslinked product of a urethane resin C having siloxane bonds and a crosslinking agent D as the urethane resin. In particular, it is more preferable that the urethane resin C having siloxane bonds is in the above-mentioned preferred embodiment, and that at least one of the above-mentioned preferred embodiment is met, and it is even more preferable that the urethane resin C having siloxane bonds is in the above-mentioned preferred embodiment and the crosslinking agent D is in the above-mentioned preferred embodiment.

[0113] When the release layer contains a crosslinked urethane resin C and a crosslinking agent D, the content of the crosslinked urethane resin C and crosslinking agent D is preferably 98 to 100% by mass, and more preferably 98.5 to 100% by mass, relative to the total mass of the release layer, in terms of having superior release properties of the release surface.

[0114] As a release agent included in the release layer, -Si(R) is preferred because it offers superior release properties for the ceramic green sheet. ３ and an acrylic resin having at least one of the siloxane bonds, and -Si(R) ３ Preferably, it contains at least one resin selected from the group consisting of urethane resins having at least one of a siloxane bond, and among them, an acrylic resin having -Si(R) and -Si(R) ３ A urethane resin having the properties of is more preferable.

[0115] The release layer may contain additives other than those listed above. Examples of additives include light and heavy release additives for adjusting the release force, surfactants, photosensitive materials, and adhesion enhancers. Among these, the release layer preferably contains a surfactant. Specific examples of surfactants are the same as those that may be included in the protrusion-containing layer described later. When the release layer contains additives, the additive content is preferably 0.1 to 3% by mass, and more preferably 0.1 to 2% by mass, relative to the total mass of the release layer.

[0116] The content of the release agent (preferably the resin mentioned above) in the release layer is preferably 50 to 99% by mass, and more preferably 60 to 98% by mass, relative to the total mass of the release layer. The remainder of the release layer other than the resin may be the above-mentioned additives and / or residues of solvents and catalysts contained in the release layer forming composition used to form the release layer.

[0117] The photosensitive material in the release layer may include a compound having a structure (specific structure S0) that reduces the amount of acid groups in the resin (e.g., acrylic resin) by exposure, as described in paragraph

[0129] of Japanese Patent Application Publication No. 2023-111491. Specifically, examples include monocyclic aromatic compounds such as pyridine, pyrazine, pyrimidine, and triazine; compounds in which two rings are fused to form an aromatic ring, such as quinoline, isoquinoline, quinoxaline, and quinazoline; and compounds in which three or more rings are fused to form an aromatic ring, such as acridine, benzo[f]quinoline, benzo[h]quinoline, phenanthridine, benzo[h]isoquinoline, phenanthroline, and phenazine. These compounds may further have substituents. Preferred substituents are alkyl groups, aryl groups, halogen atoms, acyl groups, alkoxycarbonyl groups, arylcarbonyl groups, carbamoyl groups, hydroxyl groups, cyano groups, or nitro groups. Furthermore, one or more compounds selected from the group consisting of acridine, benzo[f]quinoline, benzo[h]quinoline, phenanthridine, benzo[h]isoquinoline, phenanthroline, and phenazine are preferred because they have a higher molar extinction coefficient at a wavelength of 365 nm and excellent photosensitivity at a wavelength of 365 nm. These compounds may further have substituents, and preferred substituents are alkyl groups, aryl groups, halogen atoms, acyl groups, alkoxycarbonyl groups, arylcarbonyl groups, carbamoyl groups, hydroxyl groups, cyano groups, or nitro groups. After incorporating such compounds into the release layer, exposure to UV (ultraviolet) light at a wavelength of 300 to 370 nm promotes a decarboxylation reaction, which is expected to improve recyclability by reducing the release strength from the ceramic slurry and reducing the adhesion of the release layer to the polyester substrate.

[0118] (Physical properties of the release layer) The thickness of the release layer can be set according to its intended use and is not particularly limited, but is preferably 0.005 to 2.0 μm, more preferably 0.005 to 1.0 μm, and even more preferably 0.005 to 0.5 μm. Furthermore, in terms of achieving a good balance between release performance and surface smoothness of the release layer, the thickness of the release layer is preferably 2 to 250 nm, more preferably 5 to 100 nm, and even more preferably 5 to 40 nm. The thickness of the release layer is measured in accordance with the method for measuring the thickness of the polyester substrate described above.

[0119] - Maximum protrusion height Sp and average surface roughness Sa In polyester films, the maximum protrusion height Sp on the surface of the release layer is preferably less than 60 nm, more preferably 50 nm or less, even more preferably 30 nm or less, even more preferably less than 20 nm, even more preferably 14 nm or less, and even more preferably less than 10 nm, in terms of making the release layer smoother. The maximum protrusion height Sp on the surface of the release layer may be 1 nm or more, and is preferably 3 nm or more in terms of improving transportability and reducing winding failures. The average surface roughness Sa of the surface of the release layer is, for example, 0 to 5 nm, and is preferably 0 to 2 nm in terms of superior smoothness.

[0120] The maximum protrusion height Sp and average surface roughness Sa of the release layer surface can be adjusted by selecting the type of polyester and additives contained in the polyester substrate (for example, using polyester polymerized with titanium or aluminum compounds), and the type of release agent contained in the release layer.

[0121] ・Silicon atom content and nitrogen atom content The silicon atom content on the release layer surface is preferably 25.0 atm% or less, more preferably 20.0 atm% or less, still more preferably less than 15.0 atm%, particularly preferably 10.0 atm% or less, and most preferably 7.0 atm% or less, from the viewpoint of further improving the coatability of ceramic slurry and the releasability of a ceramic green sheet formed on the release layer surface. Further, the silicon atom content on the release layer surface is preferably 1.0 atm% or more, more preferably more than 1.0 atm%, still more preferably 2.0 atm% or more, and particularly preferably 3.0 atm% or more, from the viewpoint of further improving the removability of the release layer and the releasability of a ceramic green sheet formed on the release layer surface.

[0122] The nitrogen content on the release layer surface is preferably 4.0 atm% or less, more preferably less than 4.0 atm%, and still more preferably 3.0 atm% or less, from the viewpoint of further improving the removability of the release layer. Further, the nitrogen content on the release layer surface is preferably more than 0 atm%, more preferably more than 0.5 atm%, and still more preferably 1.0 atm% or more, from the viewpoint of further improving the releasability of a ceramic green sheet formed on the release layer surface.

[0123] The silicon atom content and nitrogen content on the release layer surface respectively mean the silicon atom content (atm%) and nitrogen content (atm%) relative to the total number of atoms of silicon atoms, carbon atoms, oxygen atoms, nitrogen atoms, and sulfur atoms measured by X-ray photoelectron spectroscopy (XPS). The silicon atom content and nitrogen content on the release layer surface can be adjusted by the composition of the release layer (among others, the structure of an acrylic resin or urethane resin that may be contained in the release layer), the thickness of the release layer, and the like.

[0124] The method for measuring the above silicon atom content and nitrogen content is as described in the Examples section below.

[0125] ・Surface free energy The surface free energy of the release layer surface is 60 mJ / m ２ or less in many cases, and is 35 mJ / m ２ or less is preferable, 30 mJ / m ２ or less is more preferable, and 28 mJ / m ２The following is even more preferable: The surface free energy of the peeled layer surface is 15 mJ / m ２ The above is preferable, and 17 mJ / m ２ The above is more preferable: 20 mJ / m ２ The above is even more preferable. The surface free energy of the delamination layer surface can be adjusted, for example, by the silicon atom content of the delamination layer surface. The method for measuring the surface free energy of the delamination layer surface is as described in the Examples section below.

[0126] The method for forming the release layer is not particularly limited, but it is preferable that the release layer is formed by in-line coating. More specifically, it is preferable that the release layer is formed by curing a release layer-forming composition by in-line coating. The method for forming the release layer will be explained in more detail in the "Method for Manufacturing Polyester Film" described later.

[0127] The polyester film may have layers other than the polyester substrate and the release layer. Examples of other layers include an intermediate layer placed between the release layer and the polyester substrate. Preferably, the polyester film does not have the above-mentioned other layers, and the polyester substrate and the release layer are in contact. That is, the polyester film is preferably a multilayer film consisting of a polyester substrate and a release layer.

[0128] <Protrusions and Protrusion-Containing Layers> It is preferable that the polyester film has protrusions on the surface of the polyester film that is on the polyester substrate side (referring to the surface opposite to the peel-off side of the polyester film, hereinafter also referred to as the "smooth surface"). When the polyester film of the present invention has protrusions on the smooth surface, the slipperiness of the polyester film is excellent and the transportability can be improved.

[0129] The maximum protrusion height (Sp) of the smooth surface is preferably 0.02 μm or more, and more preferably 0.03 μm or more, in terms of excellent transportability. Furthermore, the maximum protrusion height (Sp) of the smooth surface is preferably 1.0 μm or less, more preferably 0.6 μm or less, even more preferably 0.1 μm or less, and particularly preferably less than 0.06 μm. When the maximum protrusion height (Sp) of the smooth surface is within the above range, it is easier to control the coefficient of dynamic friction to 0.2 or more when the release surface of the polyester film and the smooth surface are in contact, and winding failures such as winding misalignment are less likely to occur when the polyester film is wound up. The maximum protrusion height (Sp) of the smooth surface can be measured in the same way as the maximum protrusion height of the release layer, except that the smooth surface is measured.

[0130] The above-mentioned protrusions may be formed directly on the polyester substrate as described above, or they may be formed by a protrusion-containing layer which is a separate layer from the polyester substrate. In other words, the polyester film may have the protrusion-containing layer on the side of the polyester substrate opposite to the release layer side. To put it another way, the polyester film 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 of its surfaces. The protrusion-containing layer may be provided directly on the surface of the polyester substrate, or it may be provided via an intermediate layer, but it is preferable to provide it directly on the surface of the polyester substrate in terms of superior productivity. In other words, the polyester film consists of a release layer, a polyester substrate, and a protrusion-containing layer, and it is preferable that the release layer and the polyester substrate are adjacent to each other, and the polyester substrate and the protrusion-containing layer are adjacent to each other.

[0131] The maximum protrusion height (Sp) of the smooth surface can be adjusted by, for example, the following methods: (1) Forming a particle-containing layer on one surface of the polyester substrate and adjusting the size and amount of particles contained in the particle-containing layer and the thickness of the particle-containing layer. Methods for forming the particle-containing layer include forming a coating layer of a composition containing particles, and co-extruding a second molten body containing particles and a binder together with a molten polyester body. (2) Incorporating particles into the polyester substrate and adjusting the size and amount of particles. (3) Roughening one surface of the polyester substrate by physical treatment. Examples of physical treatments include plasma treatment. The polyester film has a polyester substrate and a particle-containing layer, and it is preferable that the exposed surface of the polyester substrate is a smooth surface and the exposed surface of the particle-containing layer is a smooth surface. This embodiment is preferably adjusted by method (1).

[0132] The protrusion-containing layer only needs to have protrusions formed on at least one of its surfaces, and the method of forming them is not particularly limited. For example, one method is to provide a layer containing particles (hereinafter also referred to as the "particle-containing layer") as the protrusion-containing layer on the surface of the polyester film opposite to the release surface. Below, the particle-containing layer will be described as an example of a protrusion-containing layer.

[0133] (Particle-containing layer) The particle-containing layer is not particularly limited as long as it contains particles. Preferably, the particle-containing layer contains a binder in addition to particles. The particle-containing layer may also further contain additives.

[0134] The average particle diameter of the particles contained in the particle-containing layer is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 40 to 500 nm. Examples of particles include inorganic particles 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 (PMMA), polyester resins, silicone resins, styrene resins, urethane resins, and styrene-acrylic resins. The resin particles may or may not have a crosslinked structure. Specifically, 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 means a resin containing constituent units derived from acrylate or methacrylate.

[0135] From the viewpoint of transportability, the particle content in the particle-containing layer is preferably 0.1 to 30% by mass, and more preferably 1 to 25% by mass, relative to the total mass of the particle-containing layer.

[0136] By adjusting the type, particle size, and content of particles in the particle-containing layer, the coefficient of dynamic friction between the peeling surface and the smooth surface (the surface of the particle-containing layer opposite to the polyester substrate side) can be adjusted.

[0137] A resin binder is preferred as the binder that the particle-containing layer may contain. Examples of resin binders include acrylic resin, urethane resin, polyester resin, and olefin resin, with non-polyester resin being preferred, and specifically, acrylic resin, urethane resin, or olefin resin being preferred. Known resins can be used as the binder. The resin binder may also be an acid-modified resin. Furthermore, the binder contained in the particle-containing layer may have a cross-linked structure. In other words, the particle-containing layer may be a cross-linked film. The particle-containing layer may contain only one type of binder, or it may contain two or more types of binders. The binder content is preferably 30 to 99.8% by mass, and more preferably 50 to 99.5% by mass, relative to the total mass of the particle-containing layer.

[0138] Examples of additives included in the particle-containing layer include surfactants, waxes, antioxidants, UV absorbers, colorants, strengthening agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and mold inhibitors.

[0139] The particle-containing layer preferably contains a surfactant in that it improves the smoothness of its surface. The surfactant is not particularly limited, and examples include silicone-based surfactants, fluorine-based surfactants, and hydrocarbon-based surfactants, with fluorine-based surfactants (particularly fluorine-based surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms) or hydrocarbon-based surfactants being preferred. Only one type of surfactant may be used, or two or more types may be used in combination. The surfactant content is preferably 0.1 to 10% by mass of the total mass of the particle-containing layer, and more preferably 0.1 to 5% by mass in that it provides superior surface smoothness.

[0140] The thickness of the particle-containing layer is preferably 1 nm to 15 μm, as this improves the smoothness of the surface of the release layer. When the particle-containing layer is formed by coating, the thickness is preferably 1 to 500 nm, and more preferably 1 to 200 nm. When the particle-containing layer is formed by extrusion, the thickness is often greater than 500 nm, preferably 1 to 15 μm, and more preferably 1 to 10 μm. The thickness of the particle-containing layer is determined by preparing a section of the polyester film having a cross-section perpendicular to the main surface, and measuring the thickness of the particle-containing layer at five points in the section using a scanning electron microscope (SEM), and taking the arithmetic mean of the thicknesses in the section.

[0141] The preferred range for the maximum protrusion height (Sp) of the protrusion-containing layer is the same as the maximum protrusion height (Sp) indicated above. The surface average roughness (Sa) of the protrusion-containing layer is preferably 5 nm or less, and more preferably 3 nm or less. The lower limit may be 0 nm or more, but the surface average roughness (Sa) of the protrusion-containing layer is preferably 2 to 3 nm from the viewpoint of suppressing transfer marks and improving the smoothness of the release layer surface. The maximum protrusion height and surface average roughness of the protrusion-containing layer can be measured in the same way as the maximum protrusion height and surface average roughness of the release layer, except that the protrusion-containing layer is measured.

[0142] <Properties of Polyester Film> Polyester films preferably exhibit various properties. Preferred properties of polyester films are described below.

[0143] (Thickness) The thickness of the polyester film 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, in terms of cost-effectiveness. There is no particular lower limit to the thickness, but in terms of improved strength and processability, it is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 10 μm or more, particularly preferably 18 μm or more, and most preferably 20 μm or more. The thickness of the polyester film is determined by measuring the thickness at five arbitrarily selected different locations using a stylus-type film thickness gauge, and taking the arithmetic mean of the obtained measurements as the thickness.

[0144] (Coefficient of Dynamic Friction) In polyester films, the coefficient of dynamic friction is preferably 0.2 or higher. The coefficient of dynamic friction in polyester films refers to the coefficient of friction on both sides of the polyester film, and more specifically, the coefficient of dynamic friction between the surface of the release layer and the surface of the polyester film opposite to the surface of the release layer (the smooth surface, for example, the surface opposite to the polyester substrate side of the protrusion-containing layer). When the coefficient of dynamic friction is 0.2 or higher, winding misalignment is less likely to occur when the polyester film is wound into a roll. Furthermore, the coefficient of dynamic friction is preferably less than 1.0. When the coefficient of dynamic friction is less than 1.0, blocking is less likely to occur when the polyester film is wound into a roll. The coefficient of dynamic friction can be measured in accordance with ASTM D 1894-95. The detailed procedure for measuring the coefficient of dynamic friction shall follow the method described in the examples below.

[0145] (Maximum Shrinkage Rate) When a polyester film is heat-treated at 150°C for 30 minutes, the maximum shrinkage rate is preferably greater than 0.20% and less than 2.00%, more preferably 0.30% or more and less than 2.00%, even more preferably 0.70% or more and less than 2.00%, and particularly preferably 1.10% or more and less than 2.00%. When the maximum shrinkage rate of the polyester film is within the above range, the removal of the release layer is superior. The details of this reason are still unknown, but it is presumed to be due to the following reason: When removing the release layer, if there is residual stress between the polyester substrate and the release layer, the residual stress is released when the release layer expands due to the penetration of an alkaline aqueous solution, making it easier for the release layer to detach from the polyester substrate, thus improving the removal of the release layer. The method for measuring the above maximum shrinkage rate will be described in the examples below. The maximum shrinkage rate of the polyester film can be adjusted, for example, by selecting the heating or cooling conditions when manufacturing the polyester film, the relaxation rates of MD and TD by the gripping member (e.g., a tenter) that grips the film, etc. More specifically, this can be adjusted by changing at least one of the conditions of the heat setting process, the heat relaxation process, and the cooling process, which will be described later.

[0146] <Method for Manufacturing Polyester Film> The method for manufacturing a polyester film is not particularly limited as long as it can produce a polyester film having the above-described structure. For example, one method is to produce an unstretched polyester substrate by melt extrusion of polyester, then stretch the unstretched polyester substrate longitudinally, apply a release layer forming composition to one side of the uniaxially stretched polyester substrate, and then stretch the resulting polyester substrate with the coated layer transversely to produce a polyester film. In other words, one method is to have a longitudinal stretching step of stretching an unstretched polyester substrate longitudinally, a release layer forming step of forming a release layer, and a transverse stretching step of stretching the polyester substrate transversely.

[0147] Longitudinal stretching can be performed, for example, by conveying an unstretched polyester substrate in the longitudinal direction while applying tension between two or more stretching rolls installed in the conveying direction. The stretching ratio in the longitudinal stretching process is set appropriately 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.

[0148] The composition for forming the release layer is not particularly limited as long as it is a composition that can form the release layer described above. Examples of compositions for forming the release layer include compositions containing the release agent described above. The composition for forming the release layer may also contain a solvent.

[0149] The method for applying the release layer-forming composition is not particularly limited, and known methods can be used. Examples of application methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating. Preferably, an in-line coating method is applied, in which the release layer-forming composition is applied to one surface of a longitudinally stretched polyester substrate while the longitudinally stretched polyester substrate is being conveyed. Alternatively, an off-line coating method may be applied, in which the release layer-forming composition is applied to one surface of a biaxially stretched polyester substrate.

[0150] Transverse stretching is a process of stretching a longitudinally stretched polyester substrate in the width direction.

[0151] The above manufacturing method may include a step of forming a protrusion-containing layer. When the protrusion-containing layer is formed by coating, for example, the protrusion-containing layer can be provided by coating the surface of the polyester substrate opposite to the surface to which the release layer-forming composition is coated with a particle-containing layer. The particle-containing layer-forming composition may be any composition containing the components included in the particle-containing layer described above. When the protrusion-containing layer is formed by extrusion, for example, a second molten body containing particles and a binder can be co-extruded together with a molten polyester body, and in a laminate consisting of a particle-containing layer and a polyester substrate, the release layer-forming composition can be coated on the surface of the polyester substrate opposite to the particle-containing layer.

[0152] The above manufacturing method may include other steps in addition to the longitudinal stretching step, the layering step, and the transverse stretching step. The manufacturing method according to this embodiment may include, for example, at least one step selected from the group consisting of a heat setting step of heating and heat-fixing a biaxially stretched polyester substrate, a heat relaxation step of heating the polyester substrate heat-fixed in the heat setting step at a lower temperature than the heat setting step to relax it, a cooling step of cooling the polyester substrate that has been relaxed in the heat relaxation step, and an expansion step of expanding the polyester substrate that has been relaxed in the cooling step in the width direction. Specifically, the conditions described in paragraphs

[0085] to

[0165] of International Publication No. 2023 / 281972 are preferred. Also, the conditions described in paragraphs

[0013] to

[0096] of Japanese Patent Application Publication No. 2012-188631 are preferred.

[0153] In the heat relaxation process, heating may be performed while gripping the MD and TD of the heat-fixed film with a gripping member (e.g., a tenter). In this case, the residual stress of the film can be adjusted by adjusting the relaxation rate at the MD and TD of the film. Here, the MD relaxation rate represents the value described in paragraphs

[0088] to

[0091] of Japanese Patent Application Publication No. 2012-188631, and the TD relaxation rate represents the value described in paragraphs

[0092] to

[0094] of Japanese Patent Application Publication No. 2012-188631.

[0154] [Removal Step] This manufacturing method includes a step of removing the release layer from the polyester film by contacting the polyester film with an alkaline aqueous solution with a pH of 11 or higher (hereinafter also referred to as the "removal step"). This yields a polyester substrate from which the release layer has been removed from the polyester film. The polyester substrate thus obtained can be used for various applications.

[0155] The pH of the alkaline aqueous solution used in the removal process is 11 or higher, preferably 12 or higher, and more preferably 13 or higher, as this improves the removal efficiency of the peeled layer. Furthermore, the pH of the alkaline aqueous solution used in the removal process is preferably less than 14, as this suppresses damage to the polyester substrate. The pH value of the alkaline aqueous solution in the removal process refers to the pH at 25°C and can be measured using a known pH meter in accordance with the method compliant with JIS Z8802-1984.

[0156] The alkaline aqueous solution preferably contains a solvent and a basic compound. Examples of the solvent in the alkaline aqueous solution include water, or a mixed solvent of water and an organic solvent (preferably a polar organic solvent), with water being preferred. Specific examples of organic solvents include alcohols (e.g., methanol, ethanol). When the solvent in the alkaline aqueous solution is the above mixed solvent, the content of the organic solvent (preferably a polar organic solvent) is preferably 20% by mass or less, more preferably 10% by mass or less, and preferably 5% by mass or more, based on the total mass of the mixed solvent.

[0157] Specific examples of basic compounds include alkali metal salts such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; and organic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and choline (2-hydroxyethyltrimethylammonium hydroxide). The content of the basic compound should be adjusted as appropriate so that the pH of the alkaline aqueous solution is 11 or higher. For example, in the case of sodium hydroxide, the content is preferably 0.004% by mass or more, more preferably 0.04% by mass or more, and preferably 0.4% by mass or less, relative to the total mass of the alkaline aqueous solution.

[0158] The temperature of the alkaline aqueous solution is preferably above room temperature (25°C), as long as the alkaline aqueous solution does not boil. From the viewpoint of further improving the removal of the peeling layer, a temperature of 40°C or higher is preferable, and 60°C or higher is more preferable. Furthermore, from the viewpoint of suppressing damage to the polyester substrate, the temperature of the alkaline aqueous solution is preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower.

[0159] Methods for bringing a polyester film into contact with an alkaline aqueous solution include immersing the polyester film in the alkaline aqueous solution, spraying the alkaline aqueous solution onto the surface of the release layer of the polyester film, developing the polyester film using the alkaline aqueous solution, and bringing the polyester film into contact with a removal treatment member (described later) that holds the alkaline aqueous solution. Specific examples of methods for developing a polyester film using an alkaline aqueous solution include paddle development, shower development, spin development, and dip development.

[0160] The contact time between the polyester film and the alkaline aqueous solution is not particularly limited, but for example, 10 seconds or more is preferred. From the viewpoint of further improving the removeability of the release layer, 20 seconds or more is preferred, 1 minute or more is preferred, and 5 minutes or more is more preferred. Furthermore, from the viewpoint of suppressing damage to the polyester substrate, the contact time between the polyester film and the alkaline aqueous solution is preferably 30 minutes or less, and more preferably 20 minutes or less.

[0161] The removal process may include a process of physically removing the peeling layer using materials such as abrasive brushes and sponges (hereinafter also referred to as "removal processing materials"), as this improves the removeability of the peeling layer. The physical removal process may be carried out simultaneously with the process of bringing the polyester film into contact with the alkaline aqueous solution. In this case, it is also preferable that the removal processing materials hold the alkaline aqueous solution. Furthermore, the physical removal process may be carried out at a different time from the process of bringing the polyester film into contact with the alkaline aqueous solution, such as after the process of bringing the polyester film into contact with the alkaline aqueous solution.

[0162] [Other steps] The polyester film described above is preferably a film obtained by removing a component (preferably a ceramic green sheet) formed on the surface of the release layer. If the component formed on the surface of the release layer is a ceramic green sheet, the manufacturing method may include a ceramic green sheet manufacturing step and a ceramic green sheet removal step before the removal step described above.

[0163] The manufacturing process for the ceramic green sheet is not particularly limited and can be carried out by known methods. One example is a method in which a ceramic slurry is applied to the surface of the release layer of the polyester film, and the solvent contained in the ceramic slurry is dried and removed. This process yields a laminate comprising a polyester film and a ceramic green sheet formed on the surface of the release layer of the polyester film. The method of applying the ceramic slurry is not particularly limited, and known methods such as applying a ceramic slurry, which is obtained by dispersing ceramic powder and a binder agent in a solvent, by a reverse roll method and removing the solvent by heating and drying can be applied. The binder agent is not particularly limited, and an example is polyvinyl butyral. The solvent is also not particularly limited, and an example is ethanol and toluene.

[0164] The step of removing the ceramic green sheet is the step of removing the ceramic green sheet from the laminate. This yields the polyester film. The method for removing the ceramic green sheet is not particularly limited, and known methods can be used.

[0165] [Polyester Film] The polyester film of the present invention (hereinafter also referred to as "this film") is a polyester film comprising a polyester substrate and a release layer disposed on at least one side of the polyester substrate, wherein the release layer comprises silicon atoms and amide bonds, and the maximum shrinkage rate when the polyester film is heat-treated at 150°C for 30 minutes is greater than 0.20% and less than 2.00%. When this film is used in the above-described manufacturing method, the release layer is easily removable. The reason for this is explained in the section on the maximum shrinkage rate in the above-described manufacturing method.

[0166] The preferred embodiment of this film is the same as that of the polyester film used in the manufacturing method described above. The release layer preferably contains siloxane bonds. The preferred embodiment, measurement method, and adjustment method for the maximum shrinkage rate when this film is heat-treated at 150°C for 30 minutes are the same as those of the polyester film used in the manufacturing method described above.

[0167] <Applications> This film can be applied to a variety of uses. For example, this film is preferably used as a release film (carrier film) for the manufacture of ceramic green sheets. Ceramic green sheets manufactured using this film can be suitably used in the manufacture of ceramic capacitors, where multilayering of internal electrodes is required due to miniaturization and increased capacitance. In particular, this film exhibits less deformation due to foreign matter adhesion and superior smoothness of the release surface. Therefore, when manufacturing ceramic green sheets using this film, variations in the thickness of the ceramic green sheet caused by deformation can be suppressed, and the performance of the multilayer ceramic capacitor manufactured using that ceramic green sheet can be improved.

[0168] The method for producing a ceramic green sheet using this film is not particularly limited and can be carried out by known methods. For example, a method for producing a ceramic green sheet involves applying a prepared ceramic slurry to the release surface of the film and drying off the solvent contained in the ceramic slurry. The method for applying the ceramic slurry is not particularly limited; for example, a known method such as applying a ceramic slurry, which is a dispersion of ceramic powder and a binder agent in a solvent, by a reverse roll method and removing the solvent by heating and drying can be applied. The binder agent is not particularly limited; for example, polyvinyl butyral can be used. The solvent is also not particularly limited; for example, ethanol and toluene can be used.

[0169] The manufactured ceramic green sheet is used to manufacture ceramic capacitors. Known methods can be applied to manufacture ceramic capacitors using the ceramic green sheet, for example, the following method. First, internal electrodes are provided on a laminate of the main film and the ceramic green sheet by applying or printing a conductive paste. Next, the main film is removed from the laminate, and ceramic green sheets with internal electrodes are sequentially laminated, and the resulting laminate is pressed to produce an intermediate laminate. After cutting the intermediate laminate into a desired shape, the cut intermediate laminate is fired to obtain a ceramic body. Next, external electrodes that electrically connect to the internal electrodes are formed on the two end faces of the fired intermediate laminate using a conductive paste such as silver, thereby obtaining a ceramic capacitor. The main film removed from the laminate is suitably used as the polyester film used in the above-described manufacturing method.

[0170] This film can be used as a protective film for dry film resists, a decorative layer and a film for sheet molding such as resin sheets, a release film for process manufacturing such as semiconductor manufacturing processes, polarizing plate manufacturing processes and battery manufacturing processes, and as a separator for adhesive films such as labels, medical and office supplies.

[0171] The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. Unless otherwise specified, "parts" and "%" are based on mass.

[0172] [Physical Property Measurement] <Maximum Protrusion Height Sp, Area Average Roughness Sa> The release layer surface of a polyester film is measured under the following conditions using an optical interferometer (Vertsan 3300G Lite, manufactured by Hitachi High-Tech Corporation), and then analyzed with built-in data analysis software (VS-Measure5) to determine the maximum protrusion height Sp and area average roughness Sa of the release layer surface. For the measurement of maximum protrusion height Sp, the maximum value among the measured values obtained from five measurements at different measurement positions is adopted; for the measurement of area average roughness Sa, the average value of the measured values obtained from five measurements at different measurement positions is adopted. (Measurement conditions) ・Measurement mode: WAVE mode ・Objective lens: 50× ・Measurement area: 186 μm × 155 μm

[0173] <Surface Free Energy> Using a contact angle meter (DROPMASTER-501, manufactured by Kyowa Interface Science Co., Ltd.), a droplet was dropped onto the release layer surface of the polyester film under the condition of 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 are used as test droplets, and the surface free energy is calculated from the respectively measured contact angles by the Kitazaki-Hata method.

[0174] <Presence or Absence of Amide Bonds> The release layer of the polyester film is scraped off, and transmission measurement is carried out under the condition of a wavenumber resolution of 4 cm －１ using a microscopic IR device equipped with a Cassegrain objective lens. Atmospheric correction is performed on the obtained spectrum so that signals derived from water vapor are below the noise level. When a substrate signal is mixed in, the spectrum of only the substrate is measured by the same method as described above, and processing is performed such that the substrate signal is eliminated by means of a difference spectrum. A straight baseline is drawn between 1500 and 1550 cm －１ , and it is confirmed whether a peak near 1525 cm －１ can be observed. When a peak near 1525 cm －１ is observed, it can be determined that the release layer has an amide bond.

[0175] <Silicon and Nitrogen Atom Content> Using the following analytical instrument, which employs XPS (X-ray photoelectron spectroscopy) as its measurement principle, the following five elements present on the outermost surface of the release layer of the polyester film are measured under the following conditions. The silicon atom content (atm%) and nitrogen atom content (atm%) are calculated when the total content of the five elements is set to 100 atm%. The silicon atom content and nitrogen atom content are calculated by averaging the values ​​measured with n=3. The obtained average values ​​are taken as the silicon atom content (atm%) and nitrogen atom content (atm%) on the surface of the release layer. (Measurement conditions) Analytical instrument: X-ray photoelectron spectrometer, manufactured by Ulvac-PHI X-ray source: Monochromatic Al-Kα Measured elements: Carbon (C), Nitrogen (N), Oxygen (O), Silicon (Si), Sulfur (S) Measurement area: 300 μm × 300 μm Number of measurements: n = 3 Sputtering irradiation ions: Argon Energy: 94 eV (0.1 eV step)

[0176] <Maximum Shrinkage Rate> From a polyester film, cut out six samples (12 cm long (in the measurement direction) and 3 cm wide, varying the angle between the film's direction and the measurement direction by 30 degrees each. Place the six samples flat in a 150°C dry oven and heat-treat for 30 minutes. Remove all samples from the dry oven and leave them at room temperature (23°C) for 1 minute. Then, conditioned in an environment adjusted to 23°C and 55% RH for 1 hour. After that, calculate the heat shrinkage rate using the following formula by comparing the dimensions before and after heat treatment, and the largest heat shrinkage rate among the six samples will be taken as the maximum shrinkage rate (%). Dimensional measurement will be performed using the pin gauge method. The dimensions of the samples before and after heat treatment will be measured in the length direction. Heat shrinkage rate (%) = 100 × {(Dimensions of the sample in the measurement direction before heat treatment) - (Dimensions of the sample in the measurement direction after heat treatment)} / (Dimensions of the sample in the measurement direction before heat treatment)

[0177] [Evaluation] <Peel strength> (Preparation of ceramic slurry) Barium titanate powder (BaTiO ３Mix 100 parts by mass of barium titanate powder (product name "BT-03" manufactured by Sakai Chemical Industry Co., Ltd.), 8 parts by mass of polyvinyl butyral resin (product name "Eslec® B・K BM-2" manufactured by Sekisui Chemical Co., Ltd.) as a binder, 4 parts by mass of dioctyl phthalate (product name "Kanto Chemical Co., Ltd." dioctyl phthalate, Grade 1) as a plasticizer, and 135 parts by mass of a mixture of toluene and ethanol (mass ratio 5:5) to make a mixed solution. Add zirconia beads to the above mixed solution and disperse them in the barium titanate powder mixture using a ball mill to make a dispersion. Remove the zirconia beads from the obtained dispersion to obtain a ceramic slurry. The ceramic slurry is a composition containing an organic solvent.

[0178] (Measurement of peel strength) Using an applicator, ceramic slurry is applied to the surface of the release layer of a polyester film so that the thickness of the dried ceramic green sheet is 0.2 μm. After drying at 90°C for 1 minute, the ceramic green sheet is formed on the surface of the release layer of the polyester film. Using a peel tester (VPA-2S, manufactured by Kyowa Interface Chemical Co., Ltd., load cell load 1N), the ceramic green sheet formed on the surface of the release layer is peeled off at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 0.3 m / min. For peeling, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) is attached to a SUS (stainless steel) plate attached to the peel tester, and the polyester film with the ceramic green sheet attached is fixed on top of it with the ceramic green sheet side adhering to the double-sided tape. The polyester film is then peeled off by pulling the polyester film side. The average value of the peel force for peel distances of 20 to 50 mm is calculated from the obtained measurements and this value is taken as the peel force. Measurements were taken a total of five times, and the average value of the peeling force was adopted as the peel strength of the ceramic green sheet.

[0179] <Removability of the release layer> Under conditions of 25°C, the surface of the release layer on a polyester film is rubbed five times with a cotton swab soaked in a 0.01 mol / L sodium hydroxide aqueous solution (pH 12). The state of the release layer is then observed under a microscope (magnification 50x), and the removeability of the release layer (pH 12) is evaluated based on the following evaluation criteria. The removeability of the release layer (pH 13) is evaluated in the same manner as the evaluation method for the release layer (pH 12), except that a cotton swab soaked in a 0.10 mol / L sodium hydroxide aqueous solution (pH 13) is used, based on the following evaluation criteria. (Evaluation criteria) A: All of the release layer in the area rubbed with the cotton swab is removed. B: Part of the release layer in the area rubbed with the cotton swab is removed. C: All of the release layer in the area rubbed with the cotton swab remains.

[0180] [Preparation of Compositions for Forming the Peeling Layer] Each peeling layer-forming composition was prepared as follows. When preparing the peeling layer-forming compositions, each component was mixed and then subjected to filtration and membrane degassing (2x6 radial flow superphobic, manufactured by Polypore Co., Ltd.). When preparing peeling layer-forming composition L2, the above filtration treatment was performed using a depth-splitter type filter (SHPH010, manufactured by Rokitechno Co., Ltd.) with a pore size of 1 μm.

[0181] <Composition L1 for forming a release layer> Composition L1 for forming a release layer was obtained by mixing the following components: • Silicone emulsion (DEHESIVE EM480, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.): 200 parts by mass • Silicone emulsion (CROSSLINKER V72, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.): 30 parts by mass • Silane coupling agent (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.): 1 part by mass • Water: 770 parts by mass

[0182] <Composition L2 for Forming a Release Layer> Composition L2 for forming a release layer was obtained by mixing the following components: ・Acrylic resin A1 (containing constituent units derived from SiMA-1 (described later), methacrylic acid (MAA), and hydroxyethyl methacrylate (HEMA) in a mass ratio of 70 / 20 / 10. Solid content concentration 20% by mass): 82.5 parts by mass (16.5 parts by mass in solids) ・Crosslinking agent X2 (an oxazoline compound made of an acrylic resin without acid groups, containing constituent units derived from 2-isopropenyl-2-oxazoline, methoxypolyethylene glycol acrylate, ethyl acrylate, and methyl methacrylate in a mol ratio of 48 / 10 / 2 / 40. Weight-average molecular weight Mw: 23000. Oxazoline value = 4.8. Solid content concentration 25% by mass): 44 parts by mass (11 parts by mass in solids) ・Water: 873.5 parts by mass

[0183] Acrylic resin A1 was synthesized by the following method: 1-propanol (92.83 g) was placed in a 1-liter three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and the temperature was raised to 80°C under a nitrogen stream. Mixture solution 1, prepared by adding 2.16 g of V-601 (radical polymerization initiator; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 30.94 g of 1-propanol, was added to this mixture, along with 20.00 g of methacrylic acid (MAA) and methacrylic modified silicone oil (CH4). ２ = C(CH ３ )-C(O)O-L １１ -[Si(CH ３ ) ２ -O] ｍ -SiR(CH ３ ) ２ L in the formula １１ The definition is L in the above formula (A1-1). １１ The definition is the same as that of -[Si(R) ２ -O] ｍ -Si(R) ３The definitions of m and R in the group represented by are the same. Molecular weight: approximately 1000. Denoted as "SiMA-1". Mixture solution 2, prepared by mixing 70.00 g of () hydroxyethyl methacrylate (HEMA), 0.66 g of dodecyl mercaptan, and 30.94 g of 1-propanol, was added dropwise at a constant rate under dropping conditions that allowed each dropwise addition to be completed in 3 hours. After the dropwise addition of the mixed solution was completed, a mixed solution prepared by mixing 0.32 g of V-601 and 2 g of 1-propanol was added to the resulting reaction mixture and heated and stirred for 6 hours. After adding 49.39 g of ethanol to the resulting reaction mixture, 16.57 g of dimethylaminoethanol (neutralizing agent) (DMAE) was added dropwise using a dropping funnel, and water was added to adjust the solid content concentration to 20% to obtain a solution of acrylic resin A1.

[0184] <Composition L3 for forming a release layer> Acrylic resin A2 was synthesized by adjusting the amount of each monomer added in the synthesis of the acrylic resin, and containing SiMA-1 derived constituent units, MAA derived constituent units, and HEMA derived constituent units in a mass ratio of 50 / 20 / 30. Composition L3 for forming a release layer was prepared by using acrylic resin A2 in place of acrylic resin A1.

[0185] <Composition L4 for forming a release layer> Acrylic resin A3 was synthesized by adjusting the amount of each monomer added in the synthesis of the acrylic resin, and containing SiMA-1 derived constituent units, MAA derived constituent units, and HEMA derived constituent units in a mass ratio of 30 / 40 / 30. Composition L4 for forming a release layer was prepared by using acrylic resin A3 in place of acrylic resin A1.

[0186] <Composition L5 for forming a release layer> 10.00 parts of hydroxyl-modified silicone (FM DA-11, manufactured by JNC Corporation), 50.87 parts of polycarbonate diol (Duranole T5651, manufactured by Asahi Kasei Corporation), 9.25 parts of dimethylolpropionic acid, 66.66 parts of methyl ethyl ketone, and 29.88 parts of isophorone diisocyanate were charged into a flask. After raising the temperature of the resulting mixture to 70°C, 0.16 parts of inorganic bismuth catalyst (Neostan U-600, manufactured by Nitto Kasei Co., Ltd.) were added to the mixture and the mixture was reacted for 7 hours. 100.00 parts of methyl ethyl ketone and 70.00 parts of 2-propanol were added to the reaction solution and stirred at 70°C for a further 3 hours to obtain solution U1 (30% solids) containing a urethane resin having siloxane bonds. 0.65 parts of dimethylethanolamine were added to 83.22 parts of the obtained solution U1, and a neutralization reaction was carried out. 74.84 parts of water were added to the mixture after the reaction, and the oil phase component and the aqueous phase component were mixed. The obtained mixture was emulsified by stirring at 7000 rpm for 30 minutes using a homogenizer at room temperature (25°C) to obtain an emulsion. Distilled water (26.82 g) was added to the obtained emulsion, and the resulting liquid was heated to 50°C, and the organic solvent was removed from the liquid by distillation while stirring at 50°C for 4 hours. The liquid from which the organic solvent had been removed was diluted with distilled water to a solid content of 25% by mass to obtain a release layer forming composition L5 containing a urethane resin having siloxane bonds.

[0187] <Composition L6 for forming a release layer> Acrylic resin A4 was synthesized by adjusting the amount of each monomer added in the synthesis of the acrylic resin, and containing SiMA-1 derived constituent units, MAA derived constituent units, and HEMA derived constituent units in a mass ratio of 80 / 10 / 10. Composition L6 for forming a release layer was prepared by using acrylic resin A4 in place of acrylic resin A1.

[0188] <Composition L7 for forming a release layer> Composition L7 for forming a release layer was prepared by changing the amount of acrylic resin A4 added in the preparation of composition L6 for forming a release layer to 123 parts by mass (24.6 parts by mass in terms of solid content) and the amount of crosslinking agent X2 to 10.5 parts by mass (2.625 parts by mass in terms of solid content).

[0189] [Example 1-a] An unstretched polyester substrate was prepared with reference to the conditions described in

[0160] to

[0169] of International Publication No. 2020 / 158316. The obtained unstretched polyester substrate was longitudinally stretched. The release layer forming composition L2 was applied to one side of the longitudinally stretched polyester substrate. The formed coating film was dried with hot air at 100°C to form a release layer. That is, the release layer forming composition L2 was applied in-line. At this time, the amount of coating was adjusted so that the thickness of the release layer in the prepared biaxially oriented polyester film was 15 nm.

[0190] The obtained coated film was transversely stretched 4.5 times and heat-set at 230°C. Then, a heat relaxation treatment was performed under the conditions of a relaxation rate in the TD (TD relaxation rate): 4.0% and a relaxation rate in the MD (MD relaxation rate): 0.0% to produce a biaxially oriented polyester film with a width of 1500 mm. Without knurling, it was wound into 7000 m lengths to obtain a roll of polyester film. The thickness of the produced biaxially oriented polyester film (polyester film of Example 1) was 30 μm. The biaxially oriented polyester film (polyester film of Example 1) had an intrinsic viscosity of 0.63 dl / g and a terminal COOH content in the range of 2.6 to 2.8 eq / ton. The polyester substrate in the polyester film contained substantially no particles, and relative to the total mass of the polyester film, the Sb content was 0 to 1 ppm by mass, the Ti content was 7 ppm by mass, the Mg content was 75 ppm by mass, and the P content was 65 ppm by mass. Table 1 shows the physical properties and evaluation results of the polyester film.

[0191] [Comparative Example 1] A biaxially oriented polyester film was prepared in the same manner as in Example 1-a, except that release layer forming composition L1 was used instead of release layer forming composition L2. The physical properties and evaluation results of the polyester film are shown in Table 1.

[0192] [Examples 1-b to 6-c] Biaxially oriented polyester films were prepared in the same manner as in Example 1-a, except that the type of release layer forming composition, MD relaxation rate, and heat setting temperature were changed as shown in Table 1. The physical properties and evaluation results of the polyester films are shown in Table 1.

[0193] In the table, under the "Release Layer" column, the "Composition Number" column indicates the number of the composition for forming the release layer, and the "Sp [nm]" column indicates the "Surface E [mJ / m]" column. ２ The columns "Maximum protrusion height Sp of the peel surface, surface free energy, silicon atom content [atm%]", and "Nitrogen atom content [atm%]" respectively indicate the maximum protrusion height Sp of the peel surface, surface free energy, silicon atom content, and nitrogen atom content. Note that the average surface roughness Sa of the peel surface in the polyester films of all examples is in the range of 0 to 2 nm. Furthermore, except for the use of an aqueous sodium hydroxide solution (pH 11), performing the above evaluation of the peel layer's removeability yields the same evaluation results as when using an aqueous sodium hydroxide solution (pH 12).

[0194]

[0195] As shown in Table 1, when a polyester film having a release layer containing silicon atoms and amide bonds is used, the release layer can be effectively removed with an alkaline aqueous solution with a pH of 11 or higher (Example). On the other hand, when a polyester film having a release layer without amide bonds is used, the release layer cannot be removed with an alkaline aqueous solution with a pH of 11 or higher (Comparative Example).

[0196] Furthermore, a comparison of Examples 1-a to 1-e shows that when the maximum shrinkage rate of the polyester film is greater than 0.30%, the removeability of the release layer (pH 12) is superior (Examples 1-a and 1-c to 1-e). Also, a comparison of Examples 1-d and 1-e, 2-b and 2-c, 3-b and 3-c, 5-b and 5-c, and 6-b and 6-c shows that when the nitrogen atom content on the surface of the release layer is greater than 0 atm% and less than 4.0 atm%, the removeability of the release layer (pH 12) is superior (Examples 1-d and 1-e, 2-b and 2-c, 5-b and 5-c, and 6-b and 6-c). Furthermore, a comparison of Examples 1-d and 1-e, 2-b and 2-c, 4-b and 4-c, 5-b and 5-c, and 6-b and 6-c shows that when the silicon atom content on the surface of the peeled layer is greater than 1.0 atm% and less than 15.0 atm%, the removeability of the peeled layer (pH 12) is superior (Examples 1-d and 1-e, 2-b and 2-c, 5-b and 5-c, and 6-b and 6-c).

[0197] 300 Polyester film 310 Polyester substrate 320 Release layer 321 Other side (Release layer surface, release surface) 322 One side

Claims

1. A method for producing a polyester substrate, comprising: a polyester film including a polyester substrate and a release layer disposed on at least one side of the polyester substrate; and a polyester aqueous solution with a pH of 11 or higher, wherein the release layer contains silicon atoms and amide bonds.

2. The method for producing a polyester substrate according to claim 1, wherein the silicon atom content on the surface of the peeling layer is greater than 1.0 atm% and less than 15.0 atm%.

3. The method for producing a polyester substrate according to claim 1 or 2, wherein the nitrogen atom content on the surface of the peeling layer is greater than 0 atm% and less than 4.0 atm%.

4. The method for producing a polyester substrate according to claim 1 or 2, wherein the pH of the alkaline aqueous solution is 13 or higher.

5. A method for producing a polyester substrate according to claim 1 or 2, wherein the release layer has a crosslinked structure.

6. A polyester film comprising a polyester substrate and a release layer disposed on at least one side of the polyester substrate, wherein the release layer comprises silicon atoms and amide bonds, and the maximum shrinkage rate when the polyester film is heat-treated at 150°C for 30 minutes is greater than 0.20% and less than 2.00%.

7. The polyester film according to claim 6, wherein the release layer contains siloxane bonds.

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