Polyester film

Abstract

The present invention addresses the problem of providing a polyester film which has excellent coatability to a composition containing an organic solvent and which has excellent high-speed peelability to a sheet formed on the surface of a peelable layer. The polyester film according to the present invention comprises a release layer and a polyester substrate, the release layer comprising an acrylic resin, the water slip angle on the surface of the release layer being 90 DEG or less, and the thickness of the release layer being less than 200 nm.

Description

Technical Field

[0001] This invention relates to a polyester film. Background Technology

[0002] Polyester film is used for a variety of applications. For example, it is used as a film for touch panels, a film for optical components, a substrate for molding, a substrate for decorative films, and a substrate for photosensitive layers.

[0003] One application of polyester film is as a release film. Specifically, it is used to peel off various parts after manufacturing them by forming a release layer on a polyester substrate and contacting the release layer.

[0004] Here, when a polyester film is used as a release film, a composition containing an organic solvent (e.g., a ceramic slurry) is coated onto the surface of the release layer in the polyester film, forming a sheet (e.g., a ceramic green sheet) on the surface of the release layer. Therefore, it is required that the release layer in the polyester film has excellent coatability to the composition containing the organic solvent.

[0005] However, shrinkage defects sometimes occur when using compositions containing organic solvents, such as those described in Patent Document 1, to form a release layer and coat a ceramic slurry.

[0006] To address this issue, Patent Document 2 discloses a technique for improving coatability by forming a release layer using a composition containing a specified acrylic resin.

[0007] Previous technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2023 / 281972

[0010] Patent Document 2: International Publication No. 2021 / 192896 Summary of the Invention

[0011] The technical problem to be solved by the invention

[0012] According to the technology described in Patent Document 2 above, a release layer forming composition that does not contain silicone resin is used, thus tending to improve coatability. However, when the peeling speed is increased when peeling off the sheet formed on the surface of the release layer (i.e., high-speed peeling of the sheet), the peelability of the sheet is insufficient.

[0013] Thus, it is difficult to achieve a situation in which the release layer contained in the polyester film has both excellent coatability of the composition containing organic solvent and excellent high-speed peelability of the sheet formed on the surface of the release layer.

[0014] Therefore, the objective of this invention is to provide a polyester film that exhibits excellent coatability to compositions containing organic solvents and excellent high-speed peelability of the sheet formed on the surface of the release layer.

[0015] means for solving technical problems

[0016] The present invention was completed as a result of in-depth research conducted by the inventors to solve the aforementioned problems. Specifically, the following structure was discovered to solve the aforementioned problems.

[0017] [1]

[0018] A polyester film comprising a release layer and a polyester substrate,

[0019] The release layer comprises an acrylic resin, the water slip angle on the surface of the release layer is less than 90°, and the thickness of the release layer is less than 200 nm.

[0020] [2]

[0021] According to the polyester film described in [1], wherein,

[0022] The silicon atom content on the surface of the aforementioned release layer is less than 25 atm%.

[0023] [3]

[0024] According to the polyester film described in [1] or [2], wherein,

[0025] The aforementioned polyester substrate is substantially free of particles, and the maximum protrusion height Sp on the surface of the aforementioned release layer is less than 35 nm.

[0026] [4]

[0027] The polyester film according to any one of [1] to [3], wherein,

[0028] The thickness of the aforementioned exfoliation layer is less than 90 nm.

[0029] [5]

[0030] The polyester film according to any one of [1] to [4], wherein,

[0031] The aforementioned stripping layer has a structure represented by -Si(R)3, where R independently represents either an alkyl or an aryl group.

[0032] [6]

[0033] The polyester film according to any one of [1] to [5], wherein,

[0034] The aforementioned release layer comprises a crosslinked polymer of acrylic resin A with siloxane bonds and crosslinking agent B.

[0035] [7]

[0036] According to the polyester film described in [6], wherein,

[0037] The aforementioned acrylic resin A contains a structural unit derived from monomer A1, which is an acrylic monomer having a siloxane bond, and the molecular weight of monomer A1 is less than 4000.

[0038] [8]

[0039] The polyester film according to any one of [1] to [7] is used to manufacture ceramic green sheets.

[0040] Invention Effects

[0041] According to the present invention, a polyester film with excellent coatability to compositions containing organic solvents and excellent high-speed peelability of a sheet formed on the surface of a release layer can be provided. Attached Figure Description

[0042] Figure 1 This is a side view schematically illustrating an example of the polyester film of the present invention.

[0043] Figure 2 This is a schematic diagram showing an example of a stretching machine used to manufacture the polyester film of the present invention. Detailed Implementation

[0044] The present invention will now be described in detail.

[0045] The description of the constituent elements described below is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0046] In this specification, the numerical range indicated by “~” refers to the range encompassed by the values ​​recorded before and after “~” as the lower and upper limits.

[0047] Furthermore, in this specification, when there are two or more components, the “content” of a component refers to the total content of these two or more components.

[0048] In this specification, within the numerical range described in stages, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, within the numerical range described in this specification, the upper or lower limit value recorded in a certain numerical range can be replaced with the value shown in the embodiment.

[0049] In this specification, a combination of two or more preferred methods is a more preferred method.

[0050] In this specification, the term "process" includes not only independent processes, but also processes that perform the intended purpose even when they cannot be clearly distinguished from other processes.

[0051] In this specification, "length direction" refers to the direction of the membrane's elongation during manufacturing, and has the same meaning as "conveying direction" and "mechanical direction".

[0052] In this specification, "width direction" refers to the direction orthogonal to the length direction.

[0053] In this specification, "orthogonal" is not limited to strict orthogonality, 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°.

[0054] The content (mass%) of each structural unit relative to all units contained in acrylic resins was determined by proton nuclear magnetic resonance (NMR). 1 The acrylic resin was determined by analyzing it using ¹H-NMR.

[0055] [Polyester film]

[0056] The polyester film of the present invention will now be described in detail.

[0057] The polyester film of the present invention comprises a release layer and a polyester substrate, wherein the release layer comprises an acrylic resin, the water slip angle on the surface of the release layer is less than 90°, and the thickness of the release layer is less than 200 nm.

[0058] The polyester film of the present invention exhibits excellent coatability to compositions containing organic solvents and excellent high-speed peelability of the sheet formed on the surface of the release layer. While the details of the reasoning are not explicitly stated, it can be roughly inferred as follows.

[0059] It is speculated that in the polyester film of the present invention, the release layer comprises an acrylic resin, thereby providing excellent coatability for compositions containing organic solvents (e.g., ceramic slurries).

[0060] Furthermore, it is speculated that the hardness of the release layer is appropriately controlled by keeping the thickness of the release layer below a specified value, and the high-speed peeling performance of the thin sheet formed on the surface of the release layer is excellent by keeping the water slip angle on the surface of the release layer below a specified value.

[0061] In this specification, "effects of the invention" refers to at least one of the coatability of the composition containing organic solvent and the high-speed peelability of the sheet formed on the surface of the release layer.

[0062] The polyester film of the present invention will now be described in detail.

[0063] Figure 1 This is a side view schematically illustrating an example of the polyester film of the present invention. The polyester film 300 includes a polyester substrate 310 and a release layer 320.

[0064] A polyester substrate 310 is disposed on the surface of one side 321 of the release layer 320.

[0065] The other side 322 of the release layer 320 is the side opposite to the side of the polyester substrate 310 on which the release layer 320 is disposed (i.e., one of the sides 321), and is sometimes referred to as the release layer surface or the release surface.

[0066] <Polyester substrate>

[0067] The polyester substrate is a film-like object containing polyester resin as its main component. Here, "main component" refers to the component with the highest content (by mass) among all the components contained in the film-like object.

[0068] As the polyester substrate, a biaxially oriented polyester substrate is preferred.

[0069] "Biaxial orientation" refers to the property of molecular orientation in two axial directions. Molecular orientation is measured using a microwave transmission molecular orientation analyzer (e.g., MOA-6004, manufactured by Oji Scientific Instruments). The angle between the two axial directions is preferably in the range of 90°±5°, more preferably in the range of 90°±3°, and even more preferably in the range of 90°±1°.

[0070] Molecular orientation changes through stretching, and biaxially oriented polyester substrates can be manufactured through biaxial stretching.

[0071] From the viewpoint of improving the smoothness of the release layer surface, it is preferable that the polyester substrate is substantially free of inorganic particles. "Substantially free of inorganic particles" is defined as follows: when quantitatively analyzing the elements originating from inorganic particles using fluorescence X-ray analysis of the polyester substrate, the content of inorganic particles relative to the total mass of the polyester substrate is 50 ppm by mass or less, 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, sometimes contaminants from foreign matter, raw material resins, or dirt adhering to the production line or equipment during the manufacturing process of the polyester substrate can be shed and mixed into the polyester substrate.

[0072] Here, as inorganic particles, we can list the inorganic particles that the particle-containing layer (including the protrusion layer) can contain, as described later.

[0073] The polyester substrate is preferably substantially free of particles. Examples of particles include the aforementioned inorganic and organic particles.

[0074] The following steps confirm whether the polyester substrate is substantially free of particles.

[0075] Ten different sections of the polyester substrate were observed using a scanning electron microscope to confirm the presence or absence of particles larger than 10 nm and smaller than 10 μm on the cross-section of the polyester substrate. However, the magnification during observation was adjusted to 5000–20000x. The presence of particles in any section indicated the presence of particles in the release layer. Conversely, the absence of particles in any section indicated the absence of particles in the polyester substrate.

[0076] Here, as organic particles, the organic particles contained in the particle-containing layer (including the protrusion layer) described later can be listed.

[0077] (Polyester resin)

[0078] The polyester resin contained in the polyester substrate is a polymer with ester bonds in its main chain. Polyester resins are typically formed by polycondensation of a dicarboxylic acid compound (described later) with a diol compound.

[0079] There are no particular limitations on the polyester resin used, and known polyester resins can be used. Examples of polyester resins include polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalenedicarboxylate (PEN), and copolymers thereof, with PET, PEN, and copolymers thereof being preferred, and PET being more preferred.

[0080] The intrinsic viscosity (IV) of the polyester film of the present invention 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. Regarding the intrinsic viscosity (IV) of the polyester film of the present invention, it can be determined from the solution viscosity at 25°C after dissolving the polyester film of the present invention in a mixed solvent of 1,1,2,2-tetrachloroethane / phenol (=2 / 3 [mass ratio]).

[0081] The amount of terminal carboxyl groups (terminal COOH content, AV; Acid Value) in the polyester film of the present invention 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 amount of terminal COOH in the polyester film of the present invention, the easier it is to reduce the water content. The lower limit is, for example, 0.5 eq / ton or more. Regarding the amount of terminal COOH, it can be calculated based on its appropriate amount by titrating with a standard solution (0.01N KOH-benzyl alcohol mixed solution) using phenol red as an indicator after obtaining a solution in which the polyester film of the present invention is completely dissolved in a mixed solvent of benzyl alcohol / chloroform (=2 / 3; volume ratio). However, in this specification, "eq / ton" means molar equivalent per ton.

[0082] The melting point (Tm) of the polyester resin is preferably 220–270°C, and more preferably 245–265°C.

[0083] The glass transition temperature (Tg) of the polyester resin is preferably 65–90°C, and more preferably 70–85°C.

[0084] The manufacturing method of polyester resin is not particularly limited and can utilize well-known methods. For example, polyester resin can be manufactured by polycondensation of at least one dicarboxylic acid compound with at least one diol compound in the presence of a catalyst.

[0085] ·catalyst

[0086] The catalysts used to manufacture polyester resins are not particularly limited, and known catalysts that can be used for the synthesis of polyester resins can be utilized.

[0087] 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 from the viewpoint that they are less likely to generate foreign matter and voids in the polyester substrate.

[0088] The catalyst may be a single type or a combination of two or more types. 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, along with a phosphorus compound. When using multiple catalysts, it is preferable to use the compounds and contents described in

[0055] to

[0062] of Japanese Patent No. 5575671. Furthermore, in the polyester film, if the content of the titanium compound (converted to Ti element value) is 5 to 15 ppm by mass, the magnesium compound used is preferably 60 to 90 ppm by mass (converted to Mg element value), and the phosphorus compound used is preferably 5 to 35 ppm by mass (converted to P element value).

[0089] As a titanium compound, an organic chelated titanium complex is preferred. An organic chelated titanium complex is a titanium compound having an organic acid as a ligand.

[0090] Examples of organic acids include citric acid, lactic acid, trimellitic acid, and malic acid.

[0091] As the titanium compound, the titanium compounds described in Japanese Patent Nos. 5575671

[0049] to

[0053] can also be used, the contents of which are incorporated herein by reference. The content of the titanium compound, expressed as Ti elemental conversion relative to the total mass of the polyester film, 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. The elemental content can be determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0092] Examples of aluminum compounds include organoaluminum compounds and their partial hydrolysates. Preferably, organoaluminum compounds are carboxylates, inorganic acid salts, or chelates; more preferably, aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum chloride hydroxide, or aluminum acetylacetonate.

[0093] Dicarboxylic acid compounds

[0094] 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 esters and ethyl esters of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or aromatic dicarboxylic acid methyl esters are preferred.

[0095] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, sebacic acid, dodecanoic acid, dimer acid, eicosanoic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid.

[0096] Examples of alicyclic dicarboxylic acid compounds include adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, and decahydronaphthalene dicarboxylic acid.

[0097] 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'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, sodium 5-sulfoisophthalate, phenylindandicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorene acid.

[0098] Preferably, it is terephthalic acid or 2,6-naphthalenedicarboxylic acid, and more preferably terephthalic acid.

[0099] Dicarboxylic acid compounds can be used in combination with one or more. When using terephthalic acid as a dicarboxylic acid compound, terephthalic acid can be used alone or copolymerized with other aromatic or aliphatic dicarboxylic acids such as isophthalic acid.

[0100] Diol compounds

[0101] Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0102] 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.

[0103] Examples of alicyclic diol compounds include cyclohexanediol, spirodiol, and isosorbide.

[0104] Examples of aromatic diol compounds include, for example, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol and 9,9'-bis(4-hydroxyphenyl)fluorene.

[0105] Diol compounds can be used in combination with only one type or in combination with two or more types.

[0106] End-capping agent

[0107] In the manufacture of polyester resin, end-capping agents can be used as needed. By using end-capping agents, a structure derived from the end-capping agent is introduced into the ends of the polyester resin.

[0108] There are no restrictions on the type of capping agent; known capping agents can be used. Examples of capping agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0109] As a capping agent, reference can also be made to the contents described in paragraphs

[0055] to

[0064] of Japanese Patent Application Publication No. 2014-189002, the contents of which are incorporated into this specification.

[0110] Manufacturing conditions

[0111] There is no limitation on the reaction temperature; it can be set appropriately according to the raw materials. The preferred reaction temperature is 260–300°C, and more preferably 275–285°C.

[0112] There is no limit to the pressure; it can be set appropriately based on the raw materials. The preferred pressure is 1.33 × 10⁻⁶. -3 ~1.33×10 - 5 MPa, more preferably 6.67 × 10 MPa. -4 ~6.67×10 -5 MPa.

[0113] As a method for synthesizing polyester resin, the method described in paragraphs

[0033] to

[0070] of Japanese Patent No. 5575671 can also be used, the contents of which are incorporated in this specification.

[0114] As for the synthesis method of polyester resin, reference can also be made to the contents described in International Publication No. 2023 / 149181

[0023] to

[0046] , which are incorporated herein by reference.

[0115] The content of polyester resin in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, relative to the total mass of the polyester substrate.

[0116] There is no upper limit to the content of polyester resin; it can be appropriately set within a range of less than 100% by mass relative to the total mass of the polyester substrate.

[0117] When the polyester substrate contains polyethylene terephthalate, the content of polyethylene terephthalate relative to the total mass of polyester resin in the polyester substrate 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.

[0118] Polyester substrates may also contain components other than polyester resin (e.g., catalysts, unreacted raw material components, particles, and water).

[0119] 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. The lower limit of the thickness is not particularly limited, but from the viewpoint of improving strength and processability, it is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 10 μm or more, and particularly preferably 20 μm or more.

[0120] The thickness of the polyester substrate is set as follows: slices with a cross section perpendicular to the main surface of the polyester film are prepared, and the arithmetic mean of the thickness of the polyester substrate at 5 locations in the slices is measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0121] <Peeling Layer>

[0122] The polyester film of the present invention has a release layer.

[0123] (Physical properties of the peeling layer)

[0124] • Water slip angle on the surface of the peeling layer

[0125] In the polyester film of the present invention, the water slip angle on the surface of the release layer is 90° or less. From the viewpoint of superior high-speed peelability of the sheet formed on the surface of the release layer, the water slip angle on the surface of the release layer is preferably 85° or less, more preferably less than 80°, further preferably 75° or less, and especially preferably 70° or less. From the viewpoint of superior coatability of ceramic slurries, etc., the lower limit of the water slip angle on the surface of the release layer is preferably 5° or more, more preferably 10° or more.

[0126] The water slip angle on the surface of the release layer can be adjusted, for example, by the composition of the release layer (the structure of the acrylic resin contained in the release layer) and the reaction rate with the crosslinking agent.

[0127] The slip angle of water on the surface of the release layer can be measured using a contact angle meter. A droplet is attached to the surface of the release layer, and the glass plate is tilted. The tilt angle at which the droplet begins to move is defined as the slip angle, with a movement determination distance of 50 dots. A more specific measurement method is described in the examples section below. Here, when the tilt angle of the glass plate reaches 90° and the droplet moves within 1 second, it is considered that "the slip angle of water is 90°," thus corresponding to "the slip angle of water is 90° or less." However, if the tilt angle of the glass plate reaches 90° and the droplet still does not move after 1 second, it does not correspond to "the slip angle of water is 90° or less."

[0128] • Thickness of the peel layer

[0129] In the polyester film of the present invention, the thickness of the release layer is less than 200 nm. With a water slip angle of less than 90° across the surface of the release layer and a release layer thickness of less than 200 nm, the sheet formed on the surface of the release layer exhibits excellent high-speed peelability and excellent low-speed peelability.

[0130] From the viewpoint of achieving a better appearance when the polyester film is formed into a roll (hereinafter also referred to as "roll appearance"), the thickness of the release layer is preferably less than 120 nm, more preferably less than 90 nm, and even more preferably less than 70 nm. The lower limit of the release layer thickness can be 3 nm or more, but from the viewpoint of achieving better results from the present invention, it is preferably 6 nm or more, and more preferably 7 nm or more.

[0131] The thickness of the release layer is set as follows: the arithmetic mean of the thickness of the release layer at 5 points in the slice having a cross section perpendicular to the main surface of the polyester film is measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0132] Silicon atom content

[0133] From the viewpoint that compositions containing organic solvents have better coatability, the silicon atom content on the surface of the release layer is preferably 25 atm% or less, more preferably 20 atm% or less, and even more preferably 15 atm% or less.

[0134] Furthermore, from the viewpoint that the sheet formed on the surface of the release layer has superior high-speed and / or low-speed peelability, the silicon atom content on the surface of the release layer is preferably 2 atm% or more, more preferably 3 atm% or more, even more preferably 4 atm% or more, and particularly preferably 6 atm% or more.

[0135] However, the silicon atom content on the surface of the release layer refers to the silicon atom content (atm%) relative to the total number of silicon, carbon, oxygen, nitrogen and sulfur atoms, as determined by X-ray photoelectron spectroscopy (XPS).

[0136] The silicon atom content on the surface of the release layer can be adjusted by the composition of the release layer (the structure of the acrylic resin contained in the release layer) and the thickness of the release layer.

[0137] The silicon atom content mentioned above can be determined using an XPS analysis device.

[0138] More specifically, using an XPS analysis device, the content of the following five elements present on the outermost surface of the release layer was determined under the following conditions, and the silicon atom content (atm%) was calculated when the total of the measured atoms was set as 100 atm%. The arithmetic mean of the values ​​obtained from the above three measurements was taken as the silicon atom content (atm%) on the surface of the release layer.

[0139] (Measurement conditions)

[0140] Analytical apparatus: X-ray photoelectron spectroscopy analyzer, Ulvac-PHI system

[0141] X-ray source: Monochromatic Al-Kα

[0142] Elements measured: Carbon (C), Nitrogen (N), Oxygen (O), Silicon (Si), Sulfur (S)

[0143] Measurement area: 300μm × 300μm

[0144] Number of measurements: n=3

[0145] Sputtered irradiation ions: argon

[0146] Energy: 94 eV (0.1 eV step)

[0147] Surface free energy

[0148] The surface free energy of the peel layer is mostly 60 mJ / m 2 From the viewpoint that the high-speed peelability of the thin film formed on the surface of the release layer is superior, the following condition is preferred: 35 mJ / m 2 The following is more preferably 30 mJ / m 2 The following is a further preferred value: 29 mJ / m 2 the following.

[0149] Furthermore, from the viewpoint that compositions containing organic solvents have superior coatability, the surface free energy of the release layer surface is 15 mJ / m. 2 The preferred value is 17 mJ / m 2 The preferred value is 20 mJ / m 2 The above are further preferred options.

[0150] The surface free energy of the release layer can be adjusted, for example, by the silicon atom content of the release layer surface.

[0151] The method for determining the surface free energy of the peeling layer is described in the Examples section below.

[0152] • Maximum protrusion height Sp and average surface roughness Sa

[0153] When the polyester film of the present invention is used in the manufacture of high-grade ceramic green sheets, the surface of the release layer is preferably smooth. From this viewpoint, the maximum protrusion height Sp on the surface of the release layer is preferably less than 35 nm, more preferably less than 30 nm, further preferably less than 25 nm, and especially preferably less than 20 nm. Furthermore, it is preferably less than 15 nm, more preferably less than 15 nm, further preferably less than 13 nm, and especially preferably less than 10 nm. Moreover, the maximum protrusion height Sp on the surface of the release layer is generally more than 1 nm.

[0154] When using the acrylic resin described later to form the release layer, it is easy to adjust the maximum protrusion height Sp on the surface of the release layer to less than 35 nm.

[0155] The surface average roughness Sa of the release layer is preferably 0 to 10 nm, more preferably 0 to 5 nm, and even more preferably 0 to 2 nm.

[0156] The maximum protrusion height Sp and the average surface roughness Sa of the release layer surface can also be adjusted by methods such as selecting the type of polyester constituting the polyester substrate and the type of additives in a way that the polyester substrate is substantially free of particles and forms a smooth film (e.g., using a polyester resin polymerized from titanium compounds or aluminum compounds).

[0157] The methods for determining the maximum protrusion height Sp and the average surface roughness Sa of the peel layer surface are described in the Examples section below.

[0158] Regarding the polyester film of the present invention, the polyester substrate is substantially free of particles, and the maximum protrusion height Sp on the surface of the release layer is preferably less than 35 nm. This results in a smoother release layer surface, thus enabling the polyester film of the present invention to be preferably used in the manufacture of high-grade ceramic green sheets.

[0159] However, the meaning of "particle-free" in polyester substrate is as stated above.

[0160] Configuration

[0161] The release layer can be disposed directly on the surface of the polyester substrate or via an intermediate layer, but from the viewpoint of better productivity, it is preferable to dispose directly on the surface of the polyester substrate. That is, it is preferable that the polyester substrate and the release layer are adjacent to each other.

[0162] (The structure represented by -Si(R)3)

[0163] From the viewpoint of achieving better results with the present invention, the release layer preferably has a structure represented by -Si(R)3.

[0164] In -Si(R)3, R independently represents either alkyl or aryl groups.

[0165] Examples of alkyl groups in R include linear alkyl groups with 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms), branched alkyl groups with 3 to 12 carbon atoms (preferably 3 to 6 carbon atoms), and cyclic alkyl groups. Specifically, examples include methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, 2-ethylhexyl, tert-butyl, tert-octyl, and cyclohexyl.

[0166] The aryl group in R preferably has 6 to 30 carbon atoms, more preferably 6 to 20, and even more preferably 6 to 12. Specific examples of aryl groups include phenyl, styryl, naphthyl, and biphenyl.

[0167] From the viewpoint of achieving better results in this invention, R is preferably an alkyl group, more preferably a straight-chain alkyl group having 1 to 5 carbon atoms, and even more preferably methyl, ethyl, propyl, n-butyl, isopropyl, isobutyl or tert-butyl, and especially preferably methyl, ethyl, propyl or butyl.

[0168] Multiple R values ​​can be the same or different.

[0169] From the viewpoint of achieving better results with the present invention, the structure represented by -Si(R)3 is preferably a partial structure of the structure represented by -O-Si(R)3, and more preferably -Si[-O-Si(R)3]. n R 1 3-n The structure represented and -[Si(R)₂-O] m -Si(R)3 represents at least one of the partial structures of the structure.

[0170] In the formula, R is as described above. 1 Each can be independently represented by a hydrogen atom, hydroxyl group, alkyl group, or aryl group. R 1 The definitions and preferred methods for alkyl and aryl groups are the same as those for alkyl and aryl groups represented by R. n represents 2 or 3, preferably 3. m represents an integer of 2 or more, preferably an integer from 2 to 100, and more preferably an integer from 5 to 50.

[0171] The structure represented by -Si(R)3 preferably has an acrylic resin contained in the release layer, and more preferably has a crosslinked body of acrylic resin A and crosslinking agent B, which will be described later.

[0172] (Acrylic resin)

[0173] The release layer contains acrylic resin.

[0174] In this specification, "acrylic resin" refers to a resin containing structural units derived from (meth)acrylates. However, in this specification, "(meth)acrylate" refers to the concept of including both methacrylates and acrylates.

[0175] From the viewpoint that the sheet formed on the surface of the release layer has superior high-speed peelability, the acrylic resin contained in the release layer is preferably a cross-linked acrylic resin synthesized by the reaction of acrylic resin A and cross-linking agent B when the release layer is formed by the reaction of acrylic resin A and cross-linking agent B when the release layer is formed by the reaction of acrylic resin A and cross-linking agent B.

[0176] This is because, compared to the case where a release layer is formed using a composition containing acrylic monomers, the case where a release layer is formed using a composition containing acrylic resin A (described later) and crosslinking agent B usually results in sufficient chain polymerization during the formation of the release layer and sufficient curing of the release layer.

[0177] For example, if the residue of a polymerization initiator (e.g., a photopolymerization initiator and a thermal polymerization initiator) is contained in the release layer, it can be determined that the release layer is a layer formed using a composition containing acrylic monomers and containing an acrylic resin synthesized by the chain polymerization reaction of the acrylic monomers.

[0178] The acrylic resin contained in the release layer may or may not be cross-linked. The release layer preferably comprises a cross-linked body formed by the reaction of an acrylic resin A having a reactive group A and a cross-linking agent B having a reactive group B capable of reacting with the reactive group A.

[0179] Furthermore, the acrylic resin contained in the release layer preferably has a structure represented by -Si(R)3, and more preferably has a structure represented by -Si(R)3 on the side chain.

[0180] The cross-linked polymer of acrylic resin A and cross-linking agent B will be described in more detail below.

[0181] Acrylic resin A

[0182] Acrylic resin A is a compound containing structural units derived from (meth)acrylates and having a reactive group A.

[0183] The reactive group A of the acrylic resin A may include, for example, at least one reactive group selected from carboxyl, carboxylic anhydride, carboxylate and hydroxyl groups.

[0184] From the viewpoint of achieving better results in this invention, the reactive group A is preferably a carboxyl group or a carboxylate group that is a salt of a carboxyl group.

[0185] Acrylic resin A preferably has siloxane bonds. The siloxane bonds are preferably represented by the structure -[O-Si(R)2]-. The meaning of R in -[O-Si(R)2]- is the same as the meaning of R in -Si(R)3.

[0186] Acrylic resin A is more preferably found to have two or more siloxane bonds.

[0187] From the viewpoint that the thin sheets formed on the surface of the release layer exhibit superior high-speed peelability, acrylic resin A is further preferably characterized by a linear polysiloxane structure. The linear polysiloxane structure is -[Si(R)₂-O]. m -The structure represented. R and m also include preferred embodiments related to the above-described -[Si(R)₂-O]. m In the structure represented by -Si(R)3, R and m have the same meaning.

[0188] Among them, acrylic resin A has a structure with -Si(R)3 and siloxane bonds, preferably having a structure selected from -Si[-O-Si(R)3]. n R 1 3-n The structure represented and -[Si(R)₂-O] m From the viewpoint that at least one of the structures represented by -Si(R)3 has superior high-speed peelability of the thin sheets on the surface of the formed release layer, it is more preferable to have -[Si(R)2-O]. m -Si(R)3 represents a linear chain structure. R, R 1 , n and m also include preferred methods and are related to the above R, R 1 The meanings of , n, and m are the same.

[0189] • Structural units derived from single A1

[0190] The acrylic resin A preferably contains a structural unit derived from monomer A1, which is an acrylic monomer having a siloxane bond.

[0191] The above-mentioned acrylic monomers represent the concept of including either (meth)acrylate or (meth)acrylic acid. (Meth)acrylic acid represents the concept of including both methacrylic acid and acrylic acid.

[0192] Monomer A1 is preferably a (meth)acrylate having a siloxane bond.

[0193] Furthermore, monomer A1 preferably has a group represented by -Si(R)3.

[0194] Among them, monomer A1 preferably has a composition selected from -Si[-O-Si(R)3]. n R 1 3-nThe radical and -[Si(R)2-O] are represented. m At least one of the groups represented by -Si(R)3, more preferably -[Si(R)2-O] m -Si(R)3 represents the base.

[0195] From the viewpoint that the thin film formed on the surface of the release layer has superior high-speed peelability, the molecular weight of monomer A1 is preferably 5000 or less, more preferably 4000 or less, and even more preferably 3000 or less. Where the lower limit is mostly 100 or more, it is preferably 500 or more, and more preferably 700 or more.

[0196] The detailed method for determining the molecular weight of monomer A1 is described in the Examples section. Here, when monomer A1 is a mixture of monomers with different molecular weights, the molecular weight of the substance with the highest peak intensity detected by MS spectrometry is set as the molecular weight of monomer A1.

[0197] Monomer A1 is preferably a compound represented by the following formula (A1-1).

[0198] CH2=C(R) 11 )C(O)OL 11 -Rh (A1-1)

[0199] In equation (A1-1), R 11 It can be a hydrogen atom or a methyl group.

[0200] In formula (A1-1), L 11 It can be an alkylene group that has substituents.

[0201] L 11 The alkylene group can be any of the following: linear, branched, or cyclic, preferably linear or branched, and more preferably linear.

[0202] L 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.

[0203] Specific examples of substituents that alkylene groups may have include halogen atoms, alkoxy groups (preferably with 1 to 5 carbon atoms), and carboxyl groups.

[0204] Among them, L 11 Preferably, it is an alkylene group without substituents, and more preferably propylene, ethylene, or methylene.

[0205] In formula (A1-1), Rh is a substituent with a siloxane bond.

[0206] Rh is also preferably composed of one or more groups represented by -Si(R)3.

[0207] Rh is preferably -Si[-O-Si(R)3] n R 1 3-n The radical represented is -[Si(R)₂-O]. m The radical represented by -Si(R)3 is more preferably [Si(R)2-O]. m -Si(R)3 represents the base.

[0208] R, R 1 As described above, n and m.

[0209] Specific examples of monomer A1 include propyl 3-[tris(trimethylsiloxy)silyl]methacrylate, SILAPLANE FM-0711 (manufactured by JNC Corporation), SILAPLANE FM-0721 (manufactured by JNC Corporation), SILAPLANE FM-0725 (manufactured by JNC Corporation), SILAPLANE TM-0701T (manufactured by JNC Corporation), X-22-174ASX (manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-174BX (manufactured by Shin-Etsu Chemical Co., Ltd.), KF-2012 (manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2426 (manufactured by Shin-Etsu Chemical Co., Ltd.), and X-22-2404 (manufactured by Shin-Etsu Chemical Co., Ltd.), etc., which contain silyl groups.

[0210] When acrylic resin A has structural units derived from monomer A1, the content of structural units derived from monomer A1 is preferably 10 to 90% by mass relative to all structural units (100% by mass) of acrylic resin A, more preferably 15 to 85% by mass, and even more preferably 20 to 80% by mass.

[0211] When the content of structural 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 superior. Furthermore, when the content of structural units derived from monomer A1 is 90% by mass or less, the coatability of the composition containing organic solvent is superior.

[0212] • Structural units derived from monomer A2

[0213] The acrylic resin A is preferably a structural unit comprising a monomer A2 derived from at least one of a carboxyl group, a carboxylic anhydride group, and a carboxyl salt group. This results in superior water solubility and curability of the resin.

[0214] Monomer A2 preferably does not have siloxane bonds.

[0215] When acrylic resin A contains structural units derived from monomer A2, a crosslinked body of acrylic resin A and crosslinking agent B can be formed by reacting at least one of carboxyl groups, carboxylic anhydride groups and carboxylate groups with crosslinking agent B (preferably reactive group B described later) as described later.

[0216] As carboxylic acid anhydride groups, examples include those based on anhydrides such as maleic anhydride and itaconic anhydride.

[0217] Examples of carboxyl groups include alkali metal salts of carboxyl groups, organic amine salts of carboxyl groups, and ammonium salts of carboxyl groups.

[0218] As monomers A2, examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and other carboxyl-containing monomers and their salts (e.g., sodium salts, potassium salts, ammonium salts, and tertiary amine salts).

[0219] Monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; and

[0220] (Meth)acrylates having a carboxyl or carboxylic acid base.

[0221] Specific examples of (meth)acrylates having a carboxyl or carboxylate group include 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, ω-carboxyl-polycaprolactone monoacrylate, and other carboxyl-containing (meth)acrylates.

[0222] When acrylic resin A has structural units derived from monomer A2, the content of structural units derived from monomer A2 is preferably 1 to 40% by mass relative to all structural units (100% by mass) of acrylic resin A, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass.

[0223] The resin exhibits superior water solubility and curability when the content of structural units derived from monomer A2 is 5% by mass or more. Furthermore, the peelability of the flakes formed on the surface of the release layer is superior when the content of structural units derived from monomer A2 is 30% by mass or less.

[0224] • Structural units derived from the single A3 unit

[0225] The acrylic resin A preferably further comprises structural units derived from monomer A3 with a ClogP value of 0.8 or higher. This results in superior high-speed peelability of the sheet formed on the surface of the release layer.

[0226] Monomer A3 is preferably free of siloxane bonds, carboxyl groups, carboxylic anhydride groups, and carboxylate groups.

[0227] From the viewpoint that the thin film formed on the surface of the release layer has better high-speed peelability, the ClogP value of monomer A3 is preferably 1.0 or more, and more preferably 1.2 or more.

[0228] From the viewpoint of the synthetic suitability of acrylic resin A, the ClogP value of monomer A3 is preferably 6.0 or less, more preferably 5.0 or less, and even more preferably 4.0 or less.

[0229] The ClogP value is obtained by calculating the common logarithm logP of the partition coefficient P between 1-octanol and water. Regarding the method and software used in calculating the ClogP value, well-known methods and software can be used; unless otherwise stated, the ClogP program programmed into ChemBioDraw Ultra 13.0 of Cambridge Soft Corporation is used in this invention.

[0230] From the viewpoint of copolymerization with monomers A1 and A2, monomer A3 preferably has polymerizable groups such as (meth)acryloyloxy and vinyl groups. (meth)acryloyloxy represents the concept of including acryloyloxy and methacryloyloxy.

[0231] Specific examples of monomer A3 can be listed below:

[0232] 2-Methoxyethyl acrylate (MEA), 2-hydroxy-3-phenoxypropyl acrylate (HPPA), ethylene glycol monoacetoacetate monomethacrylate (EGMM), tert-butyl acrylate (tBA), benzyl methacrylate (BnMA), phenoxyethyl acrylate (PEA), n-butyl acrylate (nBA), cyclohexyl acrylate (CyHA), tetrahydrofurfuryl methacrylate (THFMA), cyclohexyl methacrylate (CyHMA), methyl methacrylate (MMA), caprolactone-modified methacrylate, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, dicyclopentyl methacrylate, isobornyl methacrylate, and other (meth)acrylates;

[0233] Styrene (St), α-methylstyrene, etc.

[0234] When acrylic resin A has structural units derived from monomer A3, the content of structural units derived from monomer A3 is preferably 5 to 30% by mass relative to all structural units (100% by mass) of monomer A3, more preferably 7 to 25% by mass, and even more preferably 10 to 20% by mass.

[0235] When the content of structural units derived from monomer A3 is 5% by mass or more, the high-speed peelability of the flakes formed on the surface of the release layer is even better. Furthermore, when the content of structural units derived from monomer A3 is 30% by mass or less, the high-speed peelability of the flakes formed on the surface of the release layer is even better.

[0236] Structural units derived from other monomers

[0237] Acrylic resin A may have structural units derived from monomers other than monomers A1 to A3 (hereinafter also referred to as "other monomers").

[0238] As one specific example of other monomers, (meth)acrylates containing polyepoxide chains can be cited.

[0239] Specific examples of polyepoxide chains include polyepoxide methane, polyepoxide ethylene, polyepoxide propylene, and polyepoxide butane. The number of repeating units in the polyepoxide chain is preferably 3 to 100.

[0240] Examples of (meth)acrylates containing polyepoxide chains include (meth)acrylate methoxy polyethylene glycol, (meth)acrylate ethoxy polyethylene glycol, (meth)acrylate methoxy polypropylene glycol and (meth)acrylate ethoxy polypropylene glycol.

[0241] Specific examples of monomers other than (meth)acrylates containing polyoxyalkylene chains can be listed below:

[0242] Hydroxyl methyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycerol monomethacrylate, 4-hydroxybutyl methacrylate, and other hydroxyl-containing monomers;

[0243] (Meth)acrylate and epoxypropyl ether, etc., are epoxy-containing monomers;

[0244] Monomers containing sulfonic acid groups, such as styrene sulfonic acid, and their salts;

[0245] 2-Methacryloxyethyl phosphate and other phosphate-containing monomers and their salts;

[0246] (Methacrylamide), N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N,N-dialkyl (meth)acrylate (examples of alkyl groups: methyl, ethyl, n-butyl, isobutyl, etc.), acryloylmorpholine, N-hydroxymethyl (meth)acrylamide, N-isopropylacrylamide, diacetone acrylamide, and N-phenyl (meth)acrylamide, etc., are amide-containing monomers;

[0247] Vinyl isocyanate, allyl isocyanate, vinyl methyl ether, vinyl ethyl ether, vinyltrialkoxysilane, alkyl maleic acid monoester, alkyl transbutenedioic acid monoester, alkyl itaconic acid monoester, (meth)acrylonitrile vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate and butadiene.

[0248] When acrylic resin A has structural units derived from other monomers, the content of structural units derived from other monomers is preferably 1 to 30% by mass relative to all structural units (100% by mass) of acrylic resin A, more preferably 2 to 20% by mass, and even more preferably 5 to 15% by mass.

[0249] Preferred method for acrylic resin A

[0250] One preferred embodiment of acrylic resin A is one that includes structural units derived from monomer A1 and structural units derived from monomer A2, and more preferably, one that includes structural units derived from monomer A1, structural units derived from monomer A2, and structural units derived from monomer A3. Therefore, the present invention achieves even better results.

[0251] The structural units derived from the aforementioned monomer A1 are further preferably in the form of siloxane bonds.

[0252] 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 especially preferably 0.5 to 2.5 mmol / g.

[0253] 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.

[0254] As long as the acid value or hydroxyl value is above the lower limit mentioned above, the water solubility and curability of acrylic resin A are superior. As long as the acid value or hydroxyl value is below the lower limit mentioned above, the high-speed and low-speed peelability of the flakes formed on the surface of the release layer are superior.

[0255] The methods for calculating acid value and hydroxyl value are described in the Examples section below.

[0256] 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. When the Mw of acrylic resin A is 5,000 or more, the coating and manufacturing suitability of the release layer is superior. Furthermore, when the Mw of acrylic resin A is 100,000 or less, the high-speed peelability of the flakes formed on the surface of the release layer is superior.

[0257] The method for determining Mw of acrylic resin A is described in the Examples section below.

[0258] Acrylic resin A may contain only one type or two or more types.

[0259] The content of acrylic resin A relative to the total mass of the release layer is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 50 to 80% by mass. However, when the release layer comprises a crosslinked body 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.

[0260] Crosslinking agent B

[0261] Crosslinking agent B is a compound having a reactive group B that can react with the reactive group A of acrylic resin A.

[0262] From the viewpoint that a release layer can be easily formed by online coating, crosslinking agent B is preferably water-soluble.

[0263] Regarding the crosslinked body of acrylic resin A and crosslinking agent B, for example, when forming a release layer using a composition containing acrylic resin A and crosslinking agent B, it can be formed by the reaction of reactive group A of acrylic resin A and reactive group B of crosslinking agent B.

[0264] When the acrylic resin A has a carboxyl group, a carboxylic anhydride group, or a carboxylate group, from the viewpoint of excellent reactivity with the aforementioned carboxyl group, the reactive group B is preferably an oxazoline group, a carbodiimide group, an epoxy group, a hydroxymethyl group, an isocyanate group, or a capped isocyanate group. From the viewpoint of superior high-speed peelability of the sheet formed on the surface of the release layer, an oxazoline group, an epoxy group, or a carbodiimide group is more preferred, and an oxazoline group or an epoxy group is even more preferred, especially an oxazoline group. Here, a capped isocyanate group refers to a group formed by capping an isocyanate group with a capping agent (e.g., a compound having an active hydrogen group).

[0265] When acrylic resin A has hydroxyl groups, from the viewpoint of excellent reactivity with hydroxyl groups, the reactive group B is preferably an isocyanate group, hydroxymethyl group or a capped isocyanate group.

[0266] The crosslinking agent B having the reactive group B is not particularly limited; for example, one or more crosslinking agents selected from oxazoline compounds, isocyanate compounds, carbodiimide compounds, melamine compounds, and epoxy compounds can be listed. However, isocyanate compounds can be compounds having isocyanate groups capped by a capping agent.

[0267] From the viewpoint that the thin film formed on the surface of the release layer has better high-speed peelability, oxazoline compounds, epoxy compounds or carbodiimide compounds are preferred, oxazoline compounds or epoxy compounds are more preferred, and oxazoline compounds are even more preferred.

[0268] ··Oxazoline compounds

[0269] There are no particular limitations as long as the oxazoline compound is a compound with an oxazoline group. It can be a low molecular weight compound with a weight average molecular weight (Mw) of less than 1000 or a high molecular weight compound with a weight average molecular weight (Mw) of more than 1000. From the viewpoint that the sheet formed on the surface of the release layer has better high-speed peelability, a high molecular weight compound is preferred.

[0270] Examples of low-molecular-weight compounds containing 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'-ethylidene-bis-(2-oxazoline), 2,2'- Trimethylene-bis-(2-oxazoline), 2,2'-tetramethylene-bis-(2-oxazoline), 2,2'-hexamethylene-bis-(2-oxazoline), 2,2'-octamethylene-bis-(2-oxazoline), 2,2'-ethylidene-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-oxazolinylnorbornene) sulfide.

[0271] When the oxazoline compound is a polymer, any polymer having an oxazoline group is acceptable. For example, copolymers containing the aforementioned low-molecular-weight compounds having an oxazoline group as structural units can be listed.

[0272] The preferred polymeric compound containing an oxazoline group is an acrylic polymer containing an oxazoline group, and more preferably an acrylic polymer containing both an oxazoline group and a polyepoxide chain. The presence of a polyepoxide chain in the oxazoline-containing polymeric compound improves the water solubility of crosslinking agent B and enhances its suitability for online coating.

[0273] Examples of polyepoxide chains include polyepoxide methane, polyepoxide ethylene, polyepoxide propylene, and polyepoxide butane. The repeating units of the polyepoxide chain are preferably 3 to 100.

[0274] Examples of (meth)acrylates containing polyepoxide chains include (meth)acrylate methoxy polyethylene glycol, (meth)acrylate ethoxy polyethylene glycol, (meth)acrylate methoxy polypropylene glycol and (meth)acrylate ethoxy polypropylene glycol.

[0275] High molecular weight compounds with an oxazoline group may contain structural units derived from the aforementioned low molecular weight compounds with an oxazoline group, as well as structural units derived from monomers other than those derived from (meth)acrylates containing polyoxyalkylene chains.

[0276] Other monomers include, for example, alkyl-containing monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate; hydroxyl-containing monomers such as 2-hydroxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and glycerol monomethacrylate; epoxy-containing monomers such as glycidyl methacrylate and allyl glycidyl ether; styrene sulfonic acid, potassium 3-sulfopropyl methacrylate, and 2-acrylamide-2-methyl methacrylate. sulfonated monomers such as propane sulfonic acid; amide-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, ethyl, n-butyl, isobutyl, etc.), acryloylmorpholine, N-hydroxymethyl (meth)acrylamide and N-phenyl (meth)acrylamide; vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyltrialkoxysilane, alkyl maleic acid monoester, alkyl transbutenedioic acid monoester, alkyl itaconic acid monoester, (meth)acrylonitrile vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene and compounds represented by the above formula (A1-1).

[0277] From the viewpoint of achieving better results in this invention, the other monomers are preferably compounds represented by the above formula (A1-1).

[0278] From an environmental impact perspective, polymers with oxazoline groups are preferably water-soluble.

[0279] The weight-average molecular weight (Mw) of the polymeric compound having an oxazoline group is not particularly limited, but is preferably 3,000 or more, more preferably 5,000 to 200,000, and even more preferably 7,000 to 150,000.

[0280] The weight-average molecular weight (Mw) was determined by the method described in the Examples section below.

[0281] Polymers containing an oxazoline group can be commercially available. Examples of commercially available products include EPOCROS (registered trademark, hereinafter the same) K-2010E, EPOCROS K-2020E, EPOCROS K-2030E, EPOCROS WS-700 and EPOCROS WS-300 (all manufactured by NIPPON SHOKUBAI CO.,LTD.).

[0282] Isocyanate compounds

[0283] Isocyanate compounds are compounds having an isocyanate group or a terminal isocyanate group. Isocyanate compounds are preferably terminal isocyanate compounds (i.e., compounds having a terminal isocyanate group).

[0284] End-capped isocyanate compounds are compounds formed by protecting (i.e., capping) the isocyanate groups of polyisocyanates with an end-capping agent, and are included in the isocyanate compounds in this specification.

[0285] Examples of end-capping agents in isocyanates include ester compounds, phenolic compounds, alcohol compounds, oxime compounds, thiol compounds, lactam compounds, amine compounds, amide compounds, pyrazole compounds, triazole compounds, and metasulfite compounds.

[0286] Examples of ester compounds include dimalonates such as dimethyl malonate and diethyl malonate, and acetoacetate esters such as methyl acetoacetate and ethyl acetoacetate. From the viewpoint of availability, diethyl malonate is preferred.

[0287] Examples of phenolic compounds include phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, and ethylphenol.

[0288] Examples of alcohol compounds include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, propylene glycol monomethyl ether, ethylene glycol, and benzyl alcohol.

[0289] Examples of oxime compounds include acetyl oxime, methyl ethyl ketone oxime, acetone oxime, formaldehyde oxime, diacetyl monooxime, and cyclohexane oxime, with acetyl oxime or methyl ethyl ketone oxime being preferred.

[0290] Examples of thiol compounds include butyl thiol and dodecyl thiol.

[0291] Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam, with ε-caprolactam being preferred.

[0292] Examples of amine compounds include diphenylaniline, aniline, and ethyleneimine.

[0293] Examples of amide compounds include acetanilide and acetamide.

[0294] Examples of pyrazole compounds include methylpyrazole (e.g., 2-methylpyrazole, 3-methylpyrazole, 4-methylpyrazole), dimethylpyrazole (e.g., 2,4-dimethylpyrazole, 2,5-dimethylpyrazole, 3,4-dimethylpyrazole, 3,5-dimethylpyrazole), 4-nitro-3,5-dimethylpyrazole, and 4-bromo-3,5-dimethylpyrazole, with methylpyrazole or dimethylpyrazole being preferred.

[0295] Examples of triazole compounds include 1,2,4-triazole.

[0296] As polyisocyanates that protect the isocyanate groups by end-capping agents, examples include multifunctional polyisocyanates in the form of adducts (also called adducts) obtained by adding 3 moles of diisocyanate to 1 mole of trimethylolpropane, biuret (also called biuret compound) obtained by reacting 1 mole of water with 3 moles of diisocyanate, or isocyanurate (also called isocyanurate compound) obtained by polymerizing 3 moles of diisocyanate.

[0297] Polyisocyanates can be obtained by reacting polyisocyanates with polyols (e.g., polyester polyols, polyether polyols, low molecular weight polyols) to protect the isocyanate groups with end-capping agents, or polyurethane polyisocyanates.

[0298] As diisocyanates, aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates can be listed, but from the viewpoint of manufacturing ceramic green sheets that do not produce concave defects on the peeling surface and whose defects are suppressed, aliphatic diisocyanates are preferred, and hexamethylene diisocyanates are more preferred.

[0299] Examples of diisocyanates include aromatic diisocyanates, such as 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, tetraalkyldiphenylmethane diisocyanate, dialkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, polymeric diphenylmethane diisocyanate, toluene diisocyanate (2,4- or 2,6-toluene diisocyanate), 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,5-naphthylene diisocyanate, and naphthalene diisocyanate.

[0300] Examples of diisocyanates include aliphatic diisocyanates, such as hexamethylene diisocyanate, trimethylene diisocyanate, trimethylhexamethylene diisocyanate (2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate), lysine diisocyanate, xylene diisocyanate, 1,2-propylene diisocyanate, butene diisocyanate, 1,2-butene diisocyanate, 2,3-butene diisocyanate, 1,3-butene diisocyanate, and 1,5-pentamethylene diisocyanate.

[0301] Examples of diisocyanates include alicyclic isocyanates, such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,3- or 1,4-cyclohexane diisocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, methylcyclohexane diisocyanate (-2,4- or -2,6-methylcyclohexane diisocyanate), and norbornene diisocyanate.

[0302] From the viewpoints of availability and ease of synthesis, the preferred options are isocyanurates of hexamethylene diisocyanate, biuret compounds of hexamethylene diisocyanate, or adducts of hexamethylene diisocyanate.

[0303] As a capped isocyanate, commercially available products can be used.

[0304] Examples of commercially available products include the CORONATE series 2554, 2507, and BI-301 manufactured by TOSOH CORPORATION; the Duranate series SBN-70D, SBN-70P, MF-B60B, 17B-60P, TPA-B80E, and E402-B80B manufactured by Asahi Kasei Corporation; and the TAKENATE series B-830, B-815N, B-820NSU, B-842N, B-846N, B870N, B874N, and B882N manufactured by Mitsui Chemicals, Inc.

[0305] Carbodiimide compounds

[0306] Carbodiimide compounds are compounds containing a carbodiimide group.

[0307] Carbodiimide compounds can be synthesized by previously known methods. For example, by condensation reactions of diisocyanate compounds. There are no particular limitations on the diisocyanate compound; it can be any of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Specific examples of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates are the same as those described in the section on isocyanate compounds.

[0308] The carbodiimide equivalent (the mass [g] of the carbodiimide compound used to provide 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.

[0309] Melamine compounds

[0310] In this specification, melamine compounds refer to melamine and melamine derivatives formed by substituting the hydrogen atoms of the -NH2 group in melamine with substituents.

[0311] The term "melamine-based compound" is not particularly limited, but examples include hydroxymethyl melamine compounds obtained by condensing melamine with formaldehyde, wherein one or more hydrogen atoms of the -NH2 group in the melamine are substituted with hydroxymethyl (-CH2OH). Furthermore, etherified hydroxymethyl melamine compounds obtained by dehydrating and condensing the aforementioned hydroxymethyl melamine with an alcohol compound can also be included.

[0312] Specifically, as melamine compounds, examples include tris(hydroxymethyl)melamine, hexa(hydroxymethyl)melamine, trimethoxymethylmelamine, and hexa(methoxymethyl)melamine.

[0313] ··Epoxy compounds

[0314] There are no particular limitations as long as the epoxy compound has epoxy groups. Preferably, the epoxy compound has two or more epoxy groups within the molecule. The epoxy groups in the epoxy compound can be those contained in glycidyl groups or those contained in alicyclic epoxy groups. However, alicyclic epoxy groups refer, for example, to groups such as 3,4-epoxycyclohexyl groups.

[0315] Commercially available epoxy compounds can be used. Examples of commercially available epoxy compounds include CYCLOMER (registered trademark) M100, CELLOXIDE (registered trademark) 2000, CELLOXIDE (registered trademark) 2021P, 2081, EPOLEAD (registered trademark) GT401, and EHPE (registered trademark) 3150 (manufactured by Daicel Corporation).

[0316] There are no particular limitations as long as the epoxy compound is a compound with an epoxy group. It can be a low molecular weight compound with a weight average molecular weight (Mw) of less than 1000 or a high molecular weight compound with a weight average molecular weight (Mw) of more than 1000. However, from the viewpoint that the high-speed peelability of the sheet formed on the surface of the release layer is better, a high molecular weight compound is preferred.

[0317] When the epoxy compound is a low molecular weight compound, examples of low molecular weight compounds include "DENACOL-EX-521" (product name, polyglycerol polyoxypropylene ether), "DENACOL EX-512" (product name, polyglycerol polyoxypropylene ether), and "DENACOL EX-830" (product name, polyethylene glycol dioxypropylene ether) manufactured by Nagase ChemteX Corporation.

[0318] When the epoxy compound is a polymer, any polymer having an epoxy group is acceptable. Examples include polymers polymerized from monomers having epoxy groups. Preferably, acrylic polymers having epoxy groups are preferred, and more preferably, acrylic polymers containing epoxy groups and polyepoxy chains are preferred.

[0319] The epoxy compounds contain polyepoxide chains, which improves the water solubility of crosslinking agent B and enhances its suitability for online coating.

[0320] Specific examples of monomers having epoxy groups include glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, etc., among which glycidyl acrylate and glycidyl methacrylate are preferred.

[0321] In the case where the epoxy compound is an acrylic polymer containing epoxy groups and polyepoxide chains, the acrylic polymer may contain structural units derived from (meth)acrylates containing polyepoxide chains.

[0322] Specific examples of (meth)acrylates containing polyepoxide chains are the same as those described in the above-described polymers having oxazoline groups.

[0323] Polymers with epoxy groups may contain structural units derived from the aforementioned compounds with epoxy groups, as well as structural units derived from monomers other than those derived from (meth)acrylates containing polyoxyalkylene chains.

[0324] Other examples of monomers are the same as those described in the above-described polymers containing oxazoline groups.

[0325] The weight-average molecular weight (Mw) of the epoxy-containing polymer is not particularly limited, but is preferably 3,000 or more, more preferably 4,000 to 100,000, and even more preferably 5,000 to 50,000.

[0326] The weight-average molecular weight (Mw) was determined by the method described in the Examples section below.

[0327] Preferred method for crosslinking agent B

[0328] From the viewpoint that the sheet formed on the surface of the release layer has better high-speed peelability, the crosslinking agent B is preferably an acrylic resin having a reactive group B on the side chain.

[0329] Specific examples of acrylic resins having reactive group B on the side chain include the above-mentioned polymers having an oxazoline group (specifically, copolymers comprising structural units derived from the above-mentioned low molecular weight compounds having an oxazoline group and structural units derived from (meth)acrylates containing polyepoxide chains) and the above-mentioned polymers having an epoxy group (specifically, copolymers comprising structural units derived from compounds having an epoxy group and structural units derived from (meth)acrylates containing polyepoxide chains, etc.).

[0330] From the viewpoint that the sheet formed on the surface of the release layer has superior high-speed peelability, the acrylic resin having a reactive group B on the side chain is preferably the above-mentioned polymer compound having an oxazoline group.

[0331] Crosslinking agent B can be used in one or more forms.

[0332] From the viewpoint of the reactivity of acrylic resin A, the content of crosslinking agent B relative to the total mass of the release layer is preferably 1 to 80% by mass, more preferably 1 to 70% by mass, even more preferably 1 to 60% by mass, and even more preferably 10 to 50% by mass. However, when the release layer contains a crosslinked body 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.

[0333] Preferred method for crosslinking

[0334] The release layer preferably comprises a crosslinker of an acrylic resin A having siloxane bonds and a crosslinking agent B. More preferably, at least one of the above-described preferred embodiment is used, and the crosslinking agent B is also used. Even more preferably, both the above-described preferred embodiment are used, and the crosslinking agent B is also used.

[0335] In the case where the release layer contains a crosslinked body of acrylic resin A and crosslinking agent B, from the viewpoint of having better effects of the present invention, the content of the crosslinked body of acrylic resin A and crosslinking agent B relative to the total mass of the release layer is preferably 98 to 100% by mass, more preferably 98.5 to 100% by mass.

[0336] (additive)

[0337] The release layer may contain additives other than those mentioned above. Examples of additives include light and heavy peeling additives for adjusting peeling force, surfactants, adhesion enhancers, and antistatic agents.

[0338] The release layer preferably contains a surfactant. Specific examples of surfactants are the same as those described later for surfactants that can be contained in the protrusion-containing layer.

[0339] When the release layer contains additives, the content of the additives is preferably 0.1 to 3% by mass relative to the total mass of the release layer, more preferably 0.1 to 2% by mass.

[0340] <Protrusions and layers containing protrusions>

[0341] The polyester film preferably has protrusions on the surface of the polyester substrate side (referring to the surface of the polyester film opposite to the peel side, hereinafter also referred to as the "slippery surface"). If the polyester film has protrusions on the slippery surface, the polyester film has excellent lubricity, which can improve transportability.

[0342] The maximum protrusion height (Sp) of the slippery surface can be 1 nm or more, but from the viewpoint of transportability and reducing winding failures, it is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more.

[0343] Furthermore, the maximum protrusion height (Sp) of the slip-resistant surface is preferably 1.0 μm or less, more preferably 600 nm or less, and even more preferably 300 nm or less. In terms of minimizing winding defects such as slippage during polyester film winding, it is even more preferably 150 nm or less, particularly preferably 100 nm or less, and most preferably less than 60 nm. If the maximum protrusion height (Sp) of the slip-resistant surface is within the above range, the smoothness of the release layer surface can be improved.

[0344] The average surface roughness (Sa) of the slippery surface is preferably 5 nm or less, more preferably 3 nm or less. The lower limit can be 0 nm or more. From the viewpoint of suppressing transfer marks and improving the smoothness of the release layer surface, the average surface roughness (Sa) of the slippery surface is preferably 2 to 3 nm.

[0345] The maximum protrusion height (Sp) and average surface roughness (Sa) of the slippery surface can be measured using the same method as those used for the peeling layer, except for the slippery surface itself.

[0346] The aforementioned protrusions can be formed directly on the polyester substrate, or they can be formed through a layer different from the polyester substrate, namely, a protrusion-containing layer. That is, the polyester film may have a protrusion-containing layer on the side of the polyester substrate opposite to the release layer side. In other words, the polyester film may sequentially have a release layer, a polyester substrate, and a protrusion-containing layer. However, a protrusion-containing layer refers to a layer with protrusions on at least one of its surfaces.

[0347] The protruding layer can be directly disposed on the surface of the polyester substrate or disposed via an intermediate layer, but from the viewpoint of better productivity, it is preferable to dispose of it directly on the surface of the polyester substrate. That is, the polyester film consists of a release layer, a polyester substrate, and a protruding layer, with the release layer and the polyester substrate adjacent to each other, preferably with the polyester substrate and the protruding layer adjacent to each other.

[0348] The maximum protrusion height (Sp) of the slippery surface can be adjusted, for example, by the following methods.

[0349] (1) A particle-containing layer is formed on one of the surfaces of a polyester substrate, and the size and amount of particles contained in the particle-containing layer and the thickness of the particle-containing layer are adjusted. As a method for forming the particle-containing layer, methods for forming a coating layer of a particle-containing composition and methods for co-extruding a second melt containing particles and an adhesive together with a polyester melt can be listed.

[0350] (2) The polyester substrate contains particles, and the size and amount of the particles are adjusted accordingly.

[0351] (3) The surface of one of the polyester substrates is physically treated to roughen it. For example, plasma treatment can be used as a physical treatment.

[0352] The polyester film has a particle-containing layer on one of the surfaces of the polyester substrate, and the exposed surface of the particle-containing layer is preferably a slip-resistant surface. The maximum protrusion height (Sp) of the slip-resistant surface in the manner in which the exposed surface of the particle-containing layer is a slip-resistant surface is preferably adjusted by the method of (1).

[0353] The protruding layer only needs to have protrusions formed on at least one of its surfaces, and the method of forming it is not particularly limited. For example, a method can be described by providing a particle-containing layer (hereinafter also referred to as "particle-containing layer") as a protruding layer on the surface of the polyester film opposite to the peel surface side.

[0354] The following explanation uses a protrusion-containing layer as an example to illustrate a particle-containing layer.

[0355] (Including particle layer)

[0356] The particle-containing layer is not particularly limited as long as it contains particles. In addition to particles, the particle-containing layer preferably contains an adhesive. Furthermore, the particle-containing layer may further contain additives.

[0357] The average particle size of the particles contained in the particle layer is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 40 to 500 nm.

[0358] As particles, both inorganic and organic particles can be listed.

[0359] Examples of inorganic particles include, for example, silicon dioxide particles (colloidal silicon dioxide), titanium dioxide particles (titanium oxide particles), calcium carbonate, barium sulfate, and aluminum oxide particles.

[0360] Examples of organic particles include, for example, resin particles. Examples of resins constituting resin particles include, for example, acrylic resins such as polymethyl methacrylate (PMMA), polyester resins, silicone resins, styrene resins, polyurethane resins, and styrene-acrylic resins. Resin particles may or may not have a cross-linked structure. Specifically, examples include non-cross-linked acrylic resin particles, non-cross-linked styrene resin particles, cross-linked acrylic resin particles, cross-linked polyurethane resin particles, and divinylbenzene cross-linked particles.

[0361] From the viewpoint of transportability, the particle content in the particle-containing layer is preferably 0.1 to 30% by mass relative to the total mass of the particle-containing layer, and more preferably 1 to 25% by mass.

[0362] 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 slippery surface (the surface of the particle-containing layer opposite to the polyester substrate side) can be adjusted.

[0363] As the adhesive that can contain the particle layer, a resin adhesive is preferred. Examples of resin adhesives include acrylic resins, polyurethane resins, polyester resins, and olefin resins, with non-polyester resins being preferred. Specifically, acrylic resins, polyurethane resins, or olefin resins are preferred. Known resins can be used as the adhesive. Furthermore, the resin adhesive can be an acid-modified resin.

[0364] Furthermore, the adhesive contained in the particle-containing layer can have a cross-linked structure. That is, the particle-containing layer can be a cross-linked film.

[0365] The particle layer may contain only one type of adhesive or two or more types of adhesive.

[0366] The content of the adhesive relative to the total mass of the particle layer is preferably 30 to 99.8% by mass, more preferably 50 to 99.5% by mass.

[0367] Additives contained in the particle layer include, for example, surfactants, paraffin wax, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and antibacterial agents.

[0368] From the viewpoint of improving the smoothness of its surface, the particle-containing layer preferably contains a surfactant.

[0369] As a surfactant, there are no particular limitations, and examples include silicone surfactants, fluorinated surfactants and hydrocarbon surfactants, with fluorinated surfactants (especially fluorinated surfactants having a perfluoroalkyl group having 1 to 4 carbon atoms) or hydrocarbon surfactants being preferred.

[0370] A single surfactant can be used, or two or more surfactants can be used in combination.

[0371] The surfactant content is preferably 0.1 to 10% by mass relative to the total mass of the particle layer, and more preferably 0.1 to 5% by mass from the viewpoint of better surface smoothness.

[0372] From the viewpoint of the smoothness of the surface of the release layer, the thickness of the particle-containing layer is preferably 1 nm to 1 μm, more preferably 1 to 500 nm, and even more preferably 1 to 200 nm.

[0373] The thickness of the particle-containing layer is set as follows: slices with a cross-section perpendicular to the main surface of the polyester film are prepared, and the arithmetic mean of the thickness of the particle-containing layer at 5 locations in the slices is measured using a scanning electron microscope (SEM).

[0374] Properties of Polyester Film

[0375] The polyester film of the present invention preferably exhibits various properties. The preferred properties of the polyester film of the present invention will be described.

[0376] From a cost-effectiveness perspective, the thickness of the polyester film is preferably 200 μm or less, more preferably 100 μm or less, further preferably 50 μm or less, especially preferably 40 μm or less, and most preferably 35 μm or less. The lower limit of the thickness is not particularly limited, but from the viewpoint of improving strength and processability, it is preferably 1 μm or more, more preferably 3 μm or more, further preferably 10 μm or more, especially preferably 18 μm or more, and most preferably 20 μm or more.

[0377] Regarding the thickness of the polyester film, the thickness was measured at five randomly selected locations using a stylus-type film thickness gauge, and the arithmetic mean of the measured values ​​was taken as the thickness.

[0378] In polyester films, the coefficient of dynamic friction is preferably 0.2 or higher. The coefficient of dynamic friction in a polyester film refers to the coefficient of friction between the two sides of the polyester film; more specifically, it refers to the coefficient of dynamic friction between the surface of the release layer and the side of the polyester film opposite to the release layer surface (the slippery side, such as the surface containing the protruding layer opposite to the polyester substrate side). If the coefficient of dynamic friction is 0.2 or higher, it is less likely to slip during winding when the polyester film is rolled into a roll.

[0379] Furthermore, the aforementioned coefficient of kinetic friction is preferably less than 1.0. If the coefficient of kinetic friction is less than 1.0, adhesion is less likely to occur when the polyester film is rolled into a roll.

[0380] The coefficient of kinetic friction can be determined according to ASTM D 1894-95. The detailed procedure for determining the coefficient of kinetic friction is to follow the method described in the examples below.

[0381] The thermal shrinkage rate of the polyester film in both the conveying direction and the width direction, measured at a temperature of 150°C, is preferably -1.0 to 3.0%, more preferably -0.5 to 2.0%, and even more preferably 0 to 1.5%.

[0382] If the thermal shrinkage rate of the polyester film is within the above range, the dimensional stability of the ceramic green sheet formed on the surface of the release layer of the polyester film and the dimensional stability during stacking after the ceramic green sheet is peeled off from the polyester film are good, thus making it less likely to cause failure of electronic components.

[0383] The methods for determining the above-mentioned heat shrinkage rates are described in the examples described below.

[0384] The heat shrinkage rate of polyester film can be adjusted by selecting the heating or cooling conditions during the manufacturing of polyester film. More specifically, it can be adjusted by changing at least one of the conditions of the heat setting process, the heat relaxation process, and the cooling process, which will be described later.

[0385] <Manufacturing Method of Polyester Film>

[0386] The polyester film of the present invention can be manufactured according to known methods. The manufacturing method of the polyester film of the present invention preferably includes a step of coating at least one of the above-mentioned polyester substrates with a release layer forming composition (hereinafter also referred to as "composition L").

[0387] (Composition L)

[0388] Composition L is a composition capable of forming the above-described release layer.

[0389] Composition L preferably contains an acrylic resin, and more preferably contains an acrylic resin and a crosslinking agent. Furthermore, composition L more preferably contains an acrylic resin A. Composition L further preferably contains an acrylic resin A (particularly preferably an acrylic resin A having siloxane bonds) and a crosslinking agent B. Details of the acrylic resin A and the crosslinking agent B are as described above.

[0390] However, the statement that composition L contains acrylic resin A means that acrylic resin A already exists in composition L in a resin state. In other words, as acrylic resin A, the substance present in composition L in the form of monomers including (meth)acrylates is not expected to be polymerized during the formation of the release layer.

[0391] The content of acrylic resin A relative to the components (solid components) of composition L excluding solvent is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 50 to 80% by mass.

[0392] From the viewpoint of the reactivity of acrylic resin A, the content of crosslinking agent B is preferably 1 to 70% by mass relative to the components (solid components) of composition L excluding solvent, more preferably 1 to 60% by mass, and even more preferably 10 to 50% by mass.

[0393] The total content of acrylic resin A and crosslinking agent B is preferably 98 to 100 by mass relative to the components (solid components) of composition L excluding solvent.

[0394] Composition L preferably contains a solvent.

[0395] From the viewpoint of excellent online coating properties, the solvent preferably contains water.

[0396] The solvent may contain only water, or it may contain both water and alcohol.

[0397] Specific examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, propylene glycol, and propylene glycol monomethyl ether. One type of alcohol may be used, or two or more may be used.

[0398] The water content relative to the total mass of the solvent is preferably 50-100% by mass, more preferably 70-100% by mass, and even more preferably 80-99% by mass.

[0399] When the solvent contains alcohol, the alcohol content relative to the total mass of the solvent is preferably 0.5 to 50% by mass, more preferably 0.5 to 30% by mass, even more preferably 0.5 to 15% by mass, and particularly preferably 1 to 10% by mass.

[0400] The solvent content is preferably 80 to 99.5% by mass relative to the total mass of composition L, more preferably 90 to 99.0% by mass. That is, in composition L, the total content of solid components is preferably 0.5 to 20% by mass relative to the total mass of composition L, more preferably 1.0 to 10% by mass.

[0401] Composition L may further contain the additives contained in the release layer described above.

[0402] When composition L contains additives, the content of the additives is preferably 0.1 to 20% by mass relative to the total mass of the components (solid components) of composition L excluding solvents, more preferably 0.5 to 10% by mass.

[0403] The coating of composition L is preferably performed using an online coating method. An online coating method refers to a method in which composition L is coated onto at least one surface of the polyester substrate during the manufacturing process of the polyester film.

[0404] The following is shown after use. Figure 2 This is an example of a method for forming a release layer by online coating when a stretching machine is used to manufacture polyester film.

[0405] First, before the polyester substrate is conveyed to the stretching section 20, composition L is coated onto the surface of the polyester substrate to obtain a polyester substrate with a coated film. Here, the polyester substrate to which composition L is coated can be an unstretched polyester substrate or a longitudinally stretched polyester substrate.

[0406] Next, the polyester substrate with the coated film is conveyed to the stretching section 20, where the coated polyester substrate is stretched laterally while the coated film is dried. This yields a stretched polyester substrate with a release layer. However, if the polyester substrate in the coated polyester substrate conveyed to the stretching section 20 is unstretched, longitudinal stretching can be performed in the stretching section 20 before the lateral stretching.

[0407] One of the preferred methods for manufacturing polyester film is as follows: after melt extrusion of polyester resin to produce an unstretched polyester substrate, the unstretched polyester substrate is longitudinally stretched, composition L is coated on one side of the longitudinally stretched polyester substrate, and then the obtained polyester substrate is transversely stretched to produce a polyester film.

[0408] Furthermore, when composition L contains acrylic resin A having reactive group A and crosslinking agent B having reactive group B, a release layer forming step may be included, in which the acrylic resin A contained in the coating film reacts with the crosslinking agent B. As described above, when performing transverse stretching in the stretching portion 20, it is preferable to simultaneously perform the drying of the coating film and the aforementioned release layer forming step.

[0409] The following describes the various steps that can be included in the method for manufacturing the polyester film of the present invention.

[0410] (Stretching process)

[0411] The preferred method for manufacturing polyester film includes a stretching process.

[0412] In the stretching process, biaxial stretching is preferred. Biaxial stretching can be performed simultaneously with longitudinal and transverse stretching, or it can be performed in multiple stages, with longitudinal and transverse stretching in two or more stages. Examples of sequential biaxial stretching include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, longitudinal stretching → longitudinal stretching → transverse stretching, and transverse stretching → longitudinal stretching, with longitudinal stretching → transverse stretching being the most preferred.

[0413] One of the preferred methods for the stretching process is the method that includes both longitudinal stretching and transverse stretching processes, as described later.

[0414] · Stretching machine

[0415] The apparatus used for biaxial tensioning is not particularly limited, and a known tensioning machine can be used. An example of a tensioning machine will be described below with reference to the accompanying drawings.

[0416] Figure 2 This is a top view showing an example of a stretching machine used to manufacture polyester film.

[0417] Figure 2 The stretching machine 100 shown includes a pair of annular guide rails 60a and 60b and holding members 2A to 2L mounted on and movable along the guide rails. The annular guide rails 60a and 60b are arranged symmetrically to each other with respect to the membrane 200. The stretching machine 100 holds the membrane 200 by the holding members 2A to 2L and moves the holding members 2A to 2L along the guide rails, thereby stretching the membrane 200 in the width direction.

[0418] also, Figure 2 The stretching machine 100 shown includes a clamp closure device 3, a support component 4 supporting the clamp closure device 3, and a clamp opener 5.

[0419] The stretching machine 100 has a region consisting of a preheating section 10, a stretching section 20, a heat setting section 30, a heat relaxation section 40 and a cooling section 50, arranged sequentially from the upstream side of the conveying direction.

[0420] The aforementioned areas of the stretching machine 100 are divided by a windproof curtain, and the temperature of each area can be adjusted by means of hot air or the like.

[0421] The preheating section 10 is the area of ​​the preheating film 200.

[0422] The stretching section 20 is the area where the preheated film 200 is stretched by applying tension in a direction orthogonal to the direction of arrow MD (length direction), i.e., the direction of arrow TD (width direction). For example... Figure 2 As shown, in the stretching section 20, the membrane 200 is stretched from width L0 to width L1.

[0423] The heat-setting section 30 is a region that is heated and heat-set while the film 200 is under tension.

[0424] The thermal relaxation section 40 is a region in which the tension of the heat-set film 200 is thermally relaxed by heating the heat-set film 200.

[0425] like Figure 2 As shown, in the thermal relaxation section 40, the membrane 200 shrinks (relaxes) from width L1 to width L2.

[0426] The cooling section 50 is the area for cooling the thermally relaxed film 200. By cooling the film 200, the shape of the film 200 can be fixed.

[0427] Figure 2 The width of the membrane 200 fed into the cooling section 50 is L2, and the width of the membrane 200 fed from the cooling section 50 is L3.

[0428] Holding components 2A, 2B, 2E, 2F, 2I, and 2J, which are movable along the annular guide rail 60a, are mounted on the annular guide rail 60a. Holding components 2C, 2D, 2G, 2H, 2K, and 2L, which are movable along the annular guide rail 60b, are mounted on the annular guide rail 60b.

[0429] Holding components 2A, 2B, 2E, 2F, 2I, and 2J hold one end of the membrane 200 in the direction of arrow TD. Holding components 2C, 2D, 2G, 2H, 2K, and 2L hold the other end of the membrane 200 in the direction of arrow TD. Holding components 2A to 2L are mostly referred to as clamps or clips.

[0430] Holding components 2A, 2B, 2E, 2F, 2I, and 2J move counterclockwise along the annular guide rail 60a. Holding components 2C, 2D, 2G, 2H, 2K, and 2L move clockwise along the annular guide rail 60b.

[0431] While holding the ends of the film 200 in the preheating section 10, the holding members 2A to 2D move along the annular guide rails 60a or 60b, passing through the stretching section 20, the heat-setting section 30, and the heat-relaxing section 40 to the cooling section 50. Next, the holding members 2A and 2B, and the holding members 2C and 2D, move downstream of the cooling section 50 in the direction of arrow MD (e.g., ...). Figure 2 After the holding release points P and Q leave the end of the membrane 200, it moves along the annular guide rails 60a or 60b and returns to the preheating section 10. During the above process, the membrane 200 moves in the direction of arrow MD, thereby performing preheating in the preheating section 10, stretching in the stretching section 20, heat setting in the heat setting section 30, heat relaxation in the heat relaxation section 40, and cooling in the cooling section 50, and thus performing transverse stretching.

[0432] The conveying speed of the membrane 200 can be adjusted by regulating the moving speed of the holding members 2A to 2L. Furthermore, the moving speed of the holding members 2A to 2L can be changed independently.

[0433] As described above, the stretching machine 100 can stretch the film 200 laterally in the direction of arrow TD in the stretching section 20. On the other hand, the stretching machine 100 can also stretch the film 200 in the direction of arrow MD by changing the moving speed of the holding members 2A to 2L. That is, biaxial stretching can also be performed simultaneously using the stretching machine 100.

[0434] In order to support the membrane 200, the stretching machine 100 may further have other holding components (not shown) in addition to the holding components 2A to 2L.

[0435] Longitudinal stretching process

[0436] The preferred method for manufacturing polyester film includes a longitudinal stretching step of longitudinally stretching an unstretched polyester substrate.

[0437] Longitudinal stretching is performed, for example, by applying tension between two or more pairs of stretching rollers arranged along the conveying direction while conveying an unstretched polyester substrate along its length.

[0438] The stretching ratio in the longitudinal stretching process is set appropriately according to the application, 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.

[0439] • Transverse stretching process

[0440] The preferred method for manufacturing polyester film includes a transverse stretching step of transversely stretching the polyester substrate. Transverse stretching refers to the process of stretching the polyester substrate along its width, for example, in the use of... Figure 2 In the case of the stretching machine 100 described herein, the stretching is performed in the stretching section 20.

[0441] The heating temperature in the transverse stretching process is preferably 100-140°C, more preferably 110-135°C, and even more preferably 115-130°C.

[0442] The stretching ratio (transverse stretching ratio) of the polyester substrate in the width direction during the transverse stretching process is not particularly limited, but it is preferably larger than the stretching ratio in the longitudinal stretching process. The stretching ratio in the transverse stretching process is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, and even more preferably 3.5 to 4.5 times.

[0443] (Coating film formation process)

[0444] The preferred method for manufacturing the polyester film includes a coating film forming step for forming a coating film of composition L. Specifically, the coating film forming step is a step of forming a coating film by coating composition L onto at least one surface of a polyester substrate.

[0445] The coating film formation process can be either online or offline, but from the viewpoint of improving the smoothness of the release layer surface, online coating is preferred.

[0446] The above-mentioned online coating is preferably a method of coating composition L onto one surface of a longitudinally stretched polyester substrate.

[0447] In online coating, for example, when using Figure 2 In the case of the stretching machine 100 described herein, the polyester substrate (polyester substrate with a coated film) coated with composition L is stretched laterally in the stretching section 20, but at this time, the coating film is cured simultaneously with the lateral stretching. Here, curing refers to the drying of the coating film, and preferably, curing based on a crosslinking reaction is also performed. That is, when composition L contains acrylic resin A having reactive group A and crosslinking agent B having reactive group B, it is preferable to also perform the reaction between acrylic resin A and crosslinking agent B. More preferably, curing is performed to form a crosslinked structure by reacting the reactive group A of acrylic resin A with the reactive group B of crosslinking agent B.

[0448] In terms of producing a fully cured coated film (release layer), it is preferable to simultaneously perform the drying and crosslinking reactions. Furthermore, the crosslinking reaction is... Figure 2The stretching process is performed on the 20 portion, therefore it is preferable to fully crosslink at the heating temperature of the aforementioned transverse stretching process. For better high-speed peelability, reactive groups A and B, which are fully crosslinked at the heating temperature of the transverse stretching process, are preferably selected.

[0449] The coating method for composition L is not particularly limited and can be any known method. Examples of coating methods include spraying, slot coating, roller coating, doctor blade coating, spin coating, bar coating, and dip coating.

[0450] <Applications>

[0451] Polyester film is suitable for a variety of applications.

[0452] For example, polyester film is preferably used as a release film (carrier film) for the manufacture of ceramic green sheets. Ceramic green sheets manufactured using polyester film can be preferably used to manufacture ceramic capacitors that require multilayer internal electrodes due to miniaturization and increased capacitance.

[0453] The method for manufacturing ceramic green sheets using the aforementioned polyester film is not particularly limited and can be implemented using known methods. For example, a method for manufacturing ceramic green sheets can be described as follows: applying a prepared ceramic slurry to the surface of the release layer of the aforementioned polyester film, and drying to remove the solvent contained in the ceramic slurry.

[0454] The coating method for ceramic slurry is not particularly limited. For example, known methods such as coating ceramic slurry by dispersing ceramic powder and binder in a solvent using a reverse roller method, or removing the solvent by heating and drying, can be applied. There are no particular limitations on the binder; for example, polyvinyl butyral can be used. Similarly, there are no particular limitations on the solvent; for example, ethanol and toluene can be used.

[0455] The produced ceramic green sheet is used to manufacture ceramic capacitors. Known methods can be applied as a method for manufacturing ceramic capacitors using the ceramic green sheet; for example, the following methods can be listed.

[0456] First, internal electrodes are formed on a laminate of polyester film and ceramic green sheet by coating or printing with conductive paste. Next, the polyester film is removed from the laminate, and ceramic green sheets with internal electrodes attached are sequentially laminated. The resulting laminate is then pressed to create an intermediate laminate. The intermediate laminate is cut into the desired shape and fired to obtain a ceramic body. Then, external electrodes, electrically connected to the internal electrodes using a conductive paste such as silver, are formed on the two end faces of the fired intermediate laminate, thereby obtaining a ceramic capacitor.

[0457] Polyester film can also be used as a protective film for dry film photoresist, a decorative layer and a film for forming thin sheets such as resin sheets, a release film for semiconductor manufacturing processes, battery manufacturing processes and polarizer manufacturing processes, as well as a separator for adhesive films used in labels, medical products and stationery.

[0458] Example

[0459] The present invention will now be described in further detail based on embodiments.

[0460] The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the invention should not be interpreted limitedly by the embodiments shown below.

[0461] [Manufacturing of polyester film]

[0462] <Example 1>

[0463] An unstretched polyester substrate was prepared according to the conditions described in International Publication Nos. 2020 / 158316,

[0160] to

[0169] . The obtained unstretched polyester substrate was longitudinally stretched. The following protrusion-forming composition X1 was coated on one side of the longitudinally stretched polyester substrate, and the following composition L1 was coated on the opposite side. The formed coating films were dried with hot air at 100°C to form a protrusion-forming layer and a release layer. That is, the protrusion-forming composition X1 and composition L1 were coated online. At this time, the coating amount of the protrusion-forming composition X1 and composition L1 was adjusted so that the thickness of the protrusion-forming layer was 60 nm and the thickness of the release layer was 15 nm.

[0464] However, during the preparation of each composition, after mixing the components, filtration was performed using a DepthPlus type filter (SHPH010, manufactured by ROKI TECHNO CO.,LTD.) with a pore size of 1 μm, and membrane degassing (2x6 RadialFlow Super Phobic, manufactured by Polypore Japan Co.,Ltd.) was carried out.

[0465] The obtained coated film was stretched laterally to produce a biaxially stretched polyester film with a width of 1500 mm. It was wound in 7000 m sections without knurling. The thickness of the produced biaxially stretched polyester film (the polyester film of Example 1) was 31 μm. The intrinsic viscosity of the biaxially stretched polyester film (the polyester film of Example 1) was 0.63 dl / g, and the terminal COOH content was in the range of 2.6–2.8 eq / ton.

[0466] However, the polyester substrate in polyester film does not actually contain particles.

[0467] Furthermore, relative to the total mass of the biaxially stretched polyester film (the polyester film of Example 1), the Sb content was 0 to 1 ppm by mass, the Ti content was 7 ppm, the Mg content was 75 ppm, and the P content was 65 ppm. However, the determination was performed using an ICP-MS analyzer, an Agilent 7800 ICP-MS (manufactured by Agilent Technologies Japan, Ltd.).

[0468] (Contains composition X1 for forming protrusion layer)

[0469] After mixing the components shown below, the above-described filtration process and membrane degassing were performed to obtain a composition X1 containing a protrusion layer.

[0470] • Water-based primer (HYDRAN AP-40N, manufactured by DIC Corporation) with a solids concentration of 35% by mass: 112.1 parts by mass of aqueous solution

[0471] • Solid content of anionic hydrocarbon surfactant (RAPISOL (registered trademark) A-90, manufactured by NOF CORPORATION) 1% by mass, diluted in water: 55.7 parts by mass

[0472] Colloidal silica (SNOWTEX ZL, manufactured by Nissan Chemical Corporation) solid content concentration 40.5% by mass, aqueous dispersion: 11.1 parts by mass

[0473] ·Water 821.1 parts by mass

[0474] (Preparation method of composition L1)

[0475] After mixing the components shown below, the above-described filtration process and membrane degassing were performed to obtain composition L1 (composition L1 for release layer formation).

[0476] • Acrylic resin A1 (solids concentration 20% by mass): 82.5 parts by mass (16.5 parts by mass based on solids)

[0477] • Crosslinking agent B1 (an aqueous solution containing an oxazoline compound, derived from 48 / 10 / 2 / 40 (mol ratio) of acrylic polymers with structural units derived from 2-isopropenyl-2-oxazoline / methoxy-polyethylene glycol acrylate / ethyl acrylate / methyl methacrylate, 25% by mass aqueous solution, weight-average molecular weight Mw: 23000, oxazoline value = 4.8) (referred to as "B1 (oxazoline)" in the table): 44 parts by mass (11 parts by mass on a solids basis).

[0478] Water: 873.5 parts by weight

[0479] Synthesis method of acrylic resin A1

[0480] 92.83 g of 1-propanol was placed in a 1-liter three-necked flask equipped with a stirrer, thermometer, reflux cooling tube and nitrogen inlet tube, and heated to 80°C under a nitrogen flow.

[0481] Here, a mixed solution consisting of 2.16 g of V-601 (free radical polymerization initiator; manufactured by FUJIFILM Wako Pure Chemical Corporation) and 30.94 g of 1-propanol, 20.00 g of methacrylic acid (MAA), and methacrylic acid-modified silicone oil (CH2=C(CH3)-C(O)OL) was prepared. 11 -[Si(CH3)2-O] m -SiR 1 (CH3)2. L in the formula 11 The definition of R is the same as in the above formula (A1-1). 11 and L 11 The definitions are the same, and m and R in the formula are the same. 1 The definition is the same as above -[Si(R) 3 )2-O] m -SiR 1 (R) 2 The basis represented by )2, m and R 1 The definition is the same. Molecular weight: approximately 1000. In the table below, it is recorded as "SiMA-1". ) 70.00g, methyl methoxy polyethylene glycol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "M-90G"). In the table below, it is recorded as "M-90G". ) 10.00g, dodecyl mercaptan 0.66g, and a mixture of 30.94g propanol added dropwise at a constant rate over 3 hours.

[0482] After the addition of the mixed solution was completed, a mixture of 0.32 g of V-601 and 2 g of 1-propanol was added to the obtained reaction mixture, and the mixture was heated and stirred for 6 hours. Then, 49.39 g of ethanol was added to the obtained reaction mixture, followed by the addition of 16.57 g of dimethylaminoethanol (neutralizing agent) (DMAE) using a dropping funnel. Water was then added to adjust the solid content concentration to 20%, yielding a solution of acrylic resin A1.

[0483] <Examples 2-45>

[0484] Instead of composition L1 used to form the release layer, compositions L2 to L36, with their compositions changed as shown in the table below, were used to obtain biaxially stretched films (polyester films) of Examples 2 to 45. The blending amounts of each component in compositions L2 to L36 were adjusted to achieve the same solids concentration as composition L1. In Examples 20 to 28, the coating amount of composition L2 was adjusted so that the thickness of the release layer was as shown in the table below.

[0485] However, the components used to prepare compositions L2 to L36, excluding those used in composition L1, are as follows. However, the entries in parentheses at the end of each component are abbreviations of the components listed in the table below.

[0486] (Monomers used in the synthesis of acrylic resin A)

[0487] · 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (TrisMA)

[0488] · 3-[tris(trimethylsiloxy)silyl]propyl acrylate (TrisA)

[0489] · Methacrylic acid modified silicone oil (CH2=C(CH3)-C(O)OL) 11 -[Si(CH3)2-O] m -SiR 1 (CH3)2. L in the formula 11 The definition of R is the same as in the above formula (A1-1). 11 and L 11 The definitions are the same, and m and R in the formula are the same. 1 The definition is the same as above -[Si(R) 3 )2-O] m -SiR 1 (R) 2 The basis represented by )2, m and R 1 The definition is the same. The molecular weight is approximately 2000. (SiMA-2)

[0490] • Methacrylic acid modified silicone oil (CH2=C(CH3)-C(O)O-C3H6-[Si(CH3)2-O]) m -Si(CH3)2(C4H9). The definition of m in the formula is the same as that of -[Si(R 3 )2-O] m -SiR 1 (R) 2 The definition of 'm' in the radical represented by '2' is the same. Molecular weight: approximately 5000. (SiMA-3)

[0491] • Methacrylic acid modified silicone oil (CH2=C(CH3)-C(O)O-C3H6-[Si(CH3)2-O]) m -Si(CH3)2(C4H9). The definition of m in the formula is the same as that of -[Si(R 3 )2-O] m -SiR 1 (R) 2 The definition of 'm' in the radical represented by '2' is the same. Molecular weight: approximately 1000. (SiMA-4)

[0492] Acrylic acid (AA)

[0493] ·2-Methacryloxyethyl succinic acid (manufactured by KYOEISHA CHEMICAL Co.,LTD., product name "LIGHT ESTER HO-MS") (HO-MS)

[0494] Hydroxyethyl methacrylate (HEMA)

[0495] • Methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK ESTER M-40G") (M-40G)

[0496] • Methoxylated polyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK ESTER M-230G") (M-230G)

[0497] 2-Methoxyethyl Acrylate (MEA)

[0498] Diacetone Acrylamide (DAAM)

[0499] · Ethylene glycol monoacetoacetate monomethacrylate (EGMM)

[0500] · tert-butyl acrylate (tBA)

[0501] 2-Hydroxy-3-phenoxypropyl acrylate (HPPA)

[0502] ·Hydroxypropyl acrylate (HBA)

[0503] ·Phenoxyethyl acrylate (PEA)

[0504] · Benzyl methacrylate (BnMA)

[0505] Cyclohexyl acrylate (CyHA)

[0506] Cyclohexyl methacrylate (CyHMA)

[0507] Tetrahydrofurfuryl methacrylate (THFMA)

[0508] Styrene (St)

[0509] • n-Butyl acrylate (nBA)

[0510] Methyl methacrylate (MMA)

[0511] Stearyl methacrylate (MMA)

[0512] However, the molecular weight of the monomer was determined by MALDI-MS (matrix-assisted laser deionization mass spectrometry) as follows.

[0513] Specifically, a mixed solution was obtained by adding 10 μL of DHB (2,5-dihydroxybenzoic acid) (10 mg / mL, THF solution) and 5 μL of NaTFA (sodium trifluoroacetate) (1 mg / mL, THF solution) to 10 μL of monomer dilution buffer (1 mg / mL, THF solution).

[0514] For 1 μL of the obtained mixed solution, MS spectra were measured using a Bruker Ultraflextreme mass spectrometer based on the MALDI-MS principle. However, the measurements were performed with n=2. The peak with the strongest intensity in the obtained MS spectra was taken as the molecular weight.

[0515] (Neutralizing agent)

[0516] • Diisopropylethylamine (DIPEA)

[0517] • 28% ammonia solution (NH3aq)

[0518] (Cross-linking agent B)

[0519] • Crosslinking agent B2 (containing an aqueous solution of an oxazoline compound, an acrylic polymer with structural units derived from 2-isopropenyl-2-oxazoline / derived from ethyl acrylate / derived from methyl methacrylate in a 75 / 5 / 20 (mol ratio), a 10% by mass aqueous solution of solids, a weight-average molecular weight Mw of 60,000, and an oxazoline value of 7.5) (B2 (oxazoline))

[0520] • Crosslinking agent B3 (an oxazoline-containing acrylic polymer synthesized by the method described below (a copolymer represented by formula (B3) described below), weight-average molecular weight Mw: 14200) (B3 (oxazoline))

[0521] • Crosslinking agent B4 (an oxazoline-containing acrylic polymer synthesized by the method described below (a copolymer represented by formula (B4) described below), weight-average molecular weight Mw: 12300) (B4 (oxazoline))

[0522] However, the weight-average molecular weight Mw of crosslinking agent B was determined using the same method as that used for the weight-average molecular weight Mw of acrylic resin A1, which will be described later.

[0523] Synthesis method of crosslinking agent B3

[0524] 54.41 g of 1-propanol was placed in a 500 mL three-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, and heated to 80 °C under a nitrogen flow.

[0525] Here, mixed solution 1 and mixed solution 2 were added dropwise at a constant rate under the condition that the addition would end after 3 hours for each. Mixed solution 1 was a mixture of 0.62 g of V-601 (free radical polymerization initiator; manufactured by FUJIFILM Wako PureChemical Corporation) and 15.54 g of 1-propanol. Mixed solution 2 was a mixture of 20.00 g of 2-isopropenyl-2-oxazoline, 10.00 g of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (TrisMA), 20.00 g of methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd. under the product name "M-40G"), 0.88 g of dodecyl mercaptan, and 7.77 g of 1-propanol.

[0526] After the addition of the mixed solution was completed, a mixed solution consisting of 0.60 g of V-601 and 1 g of 1-propanol was added to the obtained reaction mixture, and the mixture was heated and stirred for 5 hours to obtain a solution of crosslinking agent B3. The concentration of the solid component of B3 was 40% by mass.

[0527] [Chemical Formula 1]

[0528]

[0529] The mass ratio of each structural unit of crosslinking agent B3 from left to right is 20:40:40.

[0530] Synthesis method of crosslinking agent B4

[0531] The amounts of each compound were adjusted so that the mass ratio of each structural unit was as described below. In addition, a solution of crosslinking agent B4 was obtained in the same manner as the synthesis of crosslinking agent B3. The solid content concentration of B4 was 40% by mass.

[0532] [Chemical Formula 2]

[0533]

[0534] The mass ratio of each structural unit of crosslinking agent B4 from left to right is 40:20:40.

[0535] <Comparative Example 1>

[0536] Instead of composition L1, the following composition LX1 (release layer forming composition LX1) was used, and otherwise, the biaxially stretched film (polyester film) of Comparative Example 1 was obtained in the same manner as in Example 1.

[0537] Here, composition LX1 is the coating liquid used in Example 14 of Japanese Patent Application Publication No. 2021-11081, which contains silicone (referred to as "CX1" in the table below) and does not contain acrylic resin.

[0538] (Composition LX1 for forming the release layer)

[0539] Emulsion (I) and emulsion (II) were prepared by the following steps.

[0540] Emulsion (I) was prepared by mixing and stirring 50 parts by mass of (A) a vinyl polydimethylsiloxane with dimethyl vinylsilyl groups at both ends, 0.5 parts by mass of (B) a platinum-vinylsiloxane complex solution with a platinum element content of 1% by mass, 0.11 parts by mass of (C) 1-ethynyl-1-cyclohexanol (manufactured by Nissin Chemical Co., Ltd.), 6.6 parts by mass of (D) a nonionic surfactant ("NAROACTY CL-95" manufactured by Sanyo Chemical Industries, Ltd.), and 44 parts by mass of (E) purified water. The platinum content relative to the mass of polydimethylsiloxane (A) was set to 100 ppm by mass.

[0541] Furthermore, emulsion (II) was prepared by mixing and stirring 35 parts by mass of (F) a methylhydropolysiloxane having SiH groups on its side chains and its molecular chains blocked by trimethylsiloxy groups, 5 parts by mass of (G) a nonionic surfactant (SANYO CHEMICALINDUSTRIES, LTD. "NAROACTY CL-95") and 60 parts by mass of (H) purified water.

[0542] Next, emulsions (I) and (II) were mixed and further diluted with purified water to obtain a solids concentration of 40% by mass, thus obtaining the composition. In preparing the composition, the mixing ratio of emulsions (I) and (II) was adjusted so that the ratio of the total number of moles of alkenes in component (A) to the total number of moles of SiH groups in component (F) was 2.9.

[0543] Five parts by mass of a silane coupling agent (KBE-403, manufactured by Shin-Etsu Chemical Co., Ltd.) and two parts by mass of a nonionic surfactant ("NAROACTY CL-95", manufactured by Sanyo Chemical Industries, Ltd.) were added to 92.5 parts by mass of the above composition (37 parts by mass of solids), and the mixture was further diluted with purified water to make the solids concentration 1% by mass, thus obtaining composition LX1.

[0544] <Comparative Example 2>

[0545] Instead of composition L1, composition LX2 (release layer forming composition LX2) was used, and the biaxially stretched film (polyester film) of Comparative Example 2 was obtained according to the steps described in Example 6 of International Publication No. 2018 / 150255. However, the polyester film of Comparative Example 2 was not manufactured using an online coating method.

[0546] Here, composition LX2 is the coating liquid used in Example 6 of International Publication No. 2018 / 150255, containing an acrylic resin having siloxane bonds (hereinafter referred to as "AX1"), the composition of which is shown in the table. Furthermore, the crosslinking agent BX1 (isocyanate) is the isocyanate-based crosslinking agent (SUR200, manufactured by Toyo Ink Co., Ltd.) used in Example 6 of International Publication No. 2018 / 150255. CX2 is an acrylic resin (b) without siloxane bonds (YL455, manufactured by TOYO INK CO.,LTD.) used in Example 6 of International Publication No. 2018 / 150255.

[0547] <Comparative Example 3>

[0548] Instead of composition L1, the following composition LX3 (release layer forming composition LX3) was used, and otherwise, the biaxially stretched film (polyester film) of Comparative Example 3 was obtained in the same manner as in Example 1.

[0549] Here, composition LX3 is the composition with the following composition used in Example 1 of International Publication No. 2021 / 192896.

[0550] However, the acrylic resin AX2 contained in composition LX3 is the acrylic resin A-1 used in Example 1 of International Publication No. 2021 / 192896, and is an acrylic resin synthesized using 100 parts by weight of hydroxyethyl methacrylate (HEMA), 8 parts by weight of methacrylic acid (MAA), 33 parts by weight of stearyl methacrylate (SMA), and 3 parts by weight of methyl methacrylate (MMA) as monomers. Acrylic resin AX2 does not have siloxane bonds.

[0551] Furthermore, the oxazoline crosslinking agent BX2 (oxazoline) contained in composition LX3 is the oxazoline crosslinking agent C-1 used in Example 1 of International Publication No. 2021 / 192896.

[0552] Furthermore, the polyether-modified polydimethylsiloxane DX1 contained in composition LX3 is additive E-1 used in Example 1 of International Publication No. 2021 / 192896.

[0553] (Composition LX3)

[0554] Water: 45.76 parts by weight

[0555] Isopropanol: 28.20 parts by weight

[0556] • Acrylic resin AX2 (solid content concentration 20% by mass): 14.00 parts by mass

[0557] • Oxazoline-based crosslinking agent BX2 (solid component concentration 10% by mass): 12.00 parts by mass

[0558] • Polyether-modified polydimethylsiloxane DX1, 67 Additive (100% by weight solids, manufactured by Dow Corning Toray Co., Ltd.): 0.04 parts by weight

[0559] <Comparative Example 4>

[0560] Instead of composition L1, composition LX4 (release layer forming composition LX4) was used, and the biaxially stretched film (polyester film) of Comparative Example 4 was obtained according to the steps described in Example 8 of International Publication No. 2020 / 050081. However, the polyester film of Comparative Example 4 was not manufactured using an online coating method.

[0561] Here, composition LX4 is the coating liquid used in Example 8 of International Publication No. 2020 / 050081.

[0562] However, the acrylic resin AX3 contained in composition LX4 is the silicone-containing acrylic polyol used in Example 8 of International Publication No. 2020 / 050081.

[0563] However, the melamine-based crosslinking agent BX3 (melamine) contained in composition LX4 is the same crosslinking agent (hexamethoxyhydroxymethyl melamine) used in Example 8 of International Publication No. 2020 / 050081.

[0564] Furthermore, the polyether-modified polydimethylsiloxane DX2 contained in composition LX4 is the silicone-type release agent used in Example 8 of International Publication No. 2020 / 050081.

[0565] [Properties of Acrylic Resin A]

[0566] <Acid value and hydroxyl value>

[0567] The theoretical values ​​for the acid value and hydroxyl value of acrylic resin A, calculated based on the amount of monomers used in the manufacture of acrylic resin A, are shown in the table below.

[0568] However, the acid value of acrylic resin A was determined by the following method, and the measured value was almost the same as the theoretical value mentioned above.

[0569] (Methods for determining acid value)

[0570] 1.0 g of the sample (acrylic resin A) was weighed into a 200 mL beaker, and the precise weight was recorded. 95 mL of a THF / water mixture (5 / 1 volume ratio) was added to dissolve the sample. A potentiometric titration (using an AT-510 automatic titrator, manufactured by KYOTO ELECTRONICS MANUFACTURING CO., LTD.) was performed on this solution (sample solution) with stirring using a magnetic stirrer, and the titration volume was determined based on the endpoint (performed at N=2). A blank test was performed in the same manner, and the acid value was calculated using the following formula.

[0571] Acid value (mmol / g) = 0.1 (mol / L) × f × (sample solution titration volume (mL) - blank titration volume (mL)) × sample weight (g) × solid component concentration (%) × 0.01

[0572] In the formula, f represents the titration factor of the sodium hydroxide aqueous solution.

[0573] <Weight-average molecular weight Mw>

[0574] Weight-average molecular weight (Mw) was determined by gel permeation chromatography (GPC). For the GPC determination, an HLC-8320GPC (manufactured by TOSOH CORPORATION) was used as the measuring apparatus, two TSKgel Super Multipore HZ-M columns (4.6 mm ID × 15 cm, manufactured by TOSOH CORPORATION) were used as the column, and THF (tetrahydrofuran) was used as the eluent. The sample concentration was set to 0.3% by mass, the flow rate to 0.35 mL / min, the sample injection volume to 10 μL, and the measurement temperature to 40 °C. The determination was performed using a RI (Refractive Index) detector. The calibration curves were prepared based on the 12 standard samples "TSK standard, polystyrene" prepared by TOSOH CORPORATION: "F-128", "F-80", "F-40", "F-20", "F-10", "F-4", "F-2", "F-1", "A-5000", "A-2500", "A-1000" and "A-500".

[0575] [Membrane Properties]

[0576] Surface Free Energy

[0577] The surface free energy of the release layer was determined using the following method.

[0578] Using a contact angle meter (Kyowa Interface Science Co., Ltd., DROPMASTER-501), droplets were placed on the surface of the release layer of a polyester film at 25°C, and the contact angle was measured one second after the droplets adhered to the release layer surface. Droplets containing 2 μL of purified water, 1 μL of diiodomethane, and 1 μL of ethylene glycol were used. Based on the measured contact angles, the surface free energy was calculated using the Kitazaki-Hata method.

[0579] <Maximum protrusion height Sp, average surface roughness Sa>

[0580] For the release layer surface of polyester film, the maximum protrusion height Sp and the average surface roughness Sa were measured by the following method.

[0581] The surface of the release layer of the polyester film was measured under the following conditions using an optical interferometer (Vertscan 3300G Lite, manufactured by Hitachi High-Tech Corporation). Then, the maximum protrusion height Sp and the average surface roughness Sa of the release layer surface n were determined by analyzing the data using the built-in data analysis software (VS-Measure5).

[0582] In the determination of the maximum protrusion height Sp, the maximum value obtained from 5 measurements with different measurement positions was used. In the determination of the surface average roughness Sa, the average value obtained from 5 measurements with different measurement positions was used.

[0583] (Measurement conditions)

[0584] • Measurement mode: WAVE mode

[0585] Objective lens: 50x

[0586] • Measurement area: 186μm × 155μm

[0587] The maximum protrusion height Sp of the release layer surface of the polyester film, as measured by the above method, is shown in the table below. Furthermore, the average surface roughness Sa of the release layer surface of the polyester film, as measured by the above method, is in the range of 0.5–2.0 nm in all embodiments.

[0588] The maximum protrusion height Sp and the average surface roughness Sa of the slippery surface of the polyester film were measured in the same manner as described above. As a result, in all embodiments, the maximum protrusion height Sp of the slippery surface was in the range of 10 to 60 nm, and the average surface roughness Sa of the slippery surface was in the range of 2 to 3 nm.

[0589] <Angle of water drop on the surface of the peeling layer>

[0590] Measurements were performed using a contact angle meter (Kyowa Interface Science Co., Ltd., DM-701, fully automated contact angle meter) at 23°C and 50% humidity. Specifically, a polyester film was placed on a flat glass substrate, and 10.0 μL of water was dropped onto the surface of the release layer. One second after the droplet adhered to the release layer surface, the glass plate was tilted from 0° to 90° at a tilting speed of 1.0° / second. The movement judgment distance was set to 50 dots, and the tilt angle at which the droplet began to move was taken as the measured value of the slip angle. Measurements were performed twice, and the arithmetic mean of the measured values ​​was used as the slip angle. The results of the slip angle measurements are shown in the table below. However, if the droplet did not move after one second when the glass plate tilted to 90°, it was recorded as "not falling".

[0591] <Silicon Atom Content>

[0592] For the polyester films of the examples and comparative examples, the silicon atom content (atm%) on the surface of the release layer was calculated using an analytical apparatus based on XPS (X-ray photoelectron spectroscopy) (X-ray photoelectron spectroscopy analyzer, manufactured by Ulvac-PHI) and the method described above. The calculated silicon atom content is shown in the "Surface Si Ratio" column of the table below.

[0593] However, when the silicon atom content is below the detection limit, it is marked as "0" in the table.

[0594] <Heat Shrinkage Rate>

[0595] The polyester films of each embodiment were cut into square-shaped samples with dimensions of 100 mm in the width direction and 100 mm in the direction orthogonal to the width direction.

[0596] Using a measuring microscope (product name "MM-800", manufactured by Nikon Corporation), the dimensions in the length and width directions before heating were measured, and their arithmetic mean was set as Ls. Then, the sample was placed in a sample holder and immersed in a thermostat set to 150°C.

[0597] After 30 minutes of loading, the sample is removed, and its length and width dimensions after heating are measured using a measuring microscope. The arithmetic mean of these dimensions is set as Ll.

[0598] The thermal shrinkage rate of the polyester film was calculated using the following formula (1). However, a positive value of the thermal shrinkage rate indicates shrinkage, while a negative value indicates expansion.

[0599] Thermal shrinkage rate (%) = {(Ls-Ll) / Ls} × 100 (1)

[0600] The heat shrinkage rates of the polyester films manufactured in the examples were all in the range of 0.95% to 1.15%.

[0601] <Coefficient of kinetic friction>

[0602] For the polyester films of each embodiment, the coefficient of friction between the peel surface (the surface of the peel layer) and the raised surface (the surface containing the raised layer) was determined according to ASTM D 1894-95.

[0603] As a testing condition, the distance the flat indenter moved along the length of the fixed test piece was set to 130 mm. The force required for the flat indenter to move (test force) was recorded using a measuring device, and a plot was created with the movement distance (unit: mm) on the horizontal axis and the test force (unit: N) on the vertical axis. The coefficient of kinetic friction was calculated based on the measured values ​​of the test force plotted above.

[0604] The above operation was repeated 5 times, and the average value of the kinetic friction coefficient was calculated for each of the 5 times. The average value of the kinetic friction coefficient is presented as the kinetic friction coefficient in the table below.

[0605] As a result, the coefficient of dynamic friction of the polyester film in each embodiment is in the range of 0.3 to 0.5.

[0606] [performance]

[0607] <Coating Defects>

[0608] The polyester film was cut into 2m lengths, and the surface of the release layer was visually inspected. Coating defects (pinholes) were evaluated based on the following criteria.

[0609] A: Coating defects (pinholes) less than 3

[0610] B: Coating defects (pinholes) number 3 or more but less than 10

[0611] C: Coating defects (pinholes) number more than 10

[0612] <Roll Appearance>

[0613] In the examples and comparative examples, the appearance of the roll-shaped polyester film obtained by winding the polyester film was visually observed and evaluated according to the following criteria.

[0614] A: No wrinkles were detected immediately after winding, and no wrinkles were detected after storage for one week.

[0615] B: Wrinkles were not detected immediately after winding, but they were detected after a week of storage.

[0616] C: Wrinkles were observed immediately after winding.

[0617] <Production Methods and Evaluation of Ceramic Raw Slices>

[0618] (Preparation of ceramic slurry)

[0619] A mixture was prepared by mixing 100 parts by weight of barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 8 parts by weight of polyvinyl butyral resin (manufactured by SEKISUI CHEMICAL CO.,LTD., product name "S-LEC (registered trademark) B·K BM-2") as a binder, 4 parts by weight of dioctyl phthalate (manufactured by Kanto Chemical Co., Inc., dioctyl phthalate, grade 1) as a plasticizer, and 135 parts by weight of toluene and ethanol (mass ratio 5:5). Zirconia beads were added to the above mixture, and the mixture was dispersed in the barium titanate powder mixture using a ball mill to prepare a dispersion. The zirconia beads were removed from the obtained dispersion to obtain a ceramic slurry. The ceramic slurry is a composition containing an organic solvent.

[0620] (Coating properties of ceramic slurry (shrinkage))

[0621] The ceramic slurry was applied to the release layer of the polyester film using a coater, so that the thickness of the dried ceramic green sheets was 1.0 μm, 0.5 μm, and 0.2 μm, respectively. After drying at 80 °C for 1 minute, ceramic green sheets were formed on the release layer of the polyester film.

[0622] The surface condition of the ceramic green sheet was visually inspected, and the coatability was evaluated based on the following criteria.

[0623] A: Coating is possible without craters or other defects at 1.0μm and 0.5μm. Furthermore, coating is also possible without craters or other defects at 0.2μm.

[0624] B: Coating was possible at 1.0μm and 0.5μm without craters. On the other hand, craters were formed in a portion of the 0.2μm area.

[0625] C: Coating is possible without craters or other defects in the 1.0 μm range. On the other hand, craters are formed in some areas at 0.2 μm and 0.5 μm.

[0626] (Low-speed peeling)

[0627] The ceramic slurry was applied to the release layer of the polyester film using a coater to make the thickness of the dried ceramic green sheet 0.2 μm. After drying at 90°C for 1 minute, the ceramic green sheet was formed on the release layer of the polyester film.

[0628] Ceramic green sheets formed on the surface of the release layer were peeled using a peel tester (Kyowa Interface Science Co., Ltd., VPA-2S, force sensor load 1N) at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 0.3 m / min. As the peel direction, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to the SUS (stainless steel) plate provided with the peel tester. The polyester film with the ceramic green sheet attached was fixed to the tape in such a way that the ceramic green sheet side was bonded to the tape. Peeling was performed by stretching the polyester film side. The average peel force was calculated for peel distances of 20 mm to 50 mm and taken as the peel force. A total of 5 measurements were performed, and the average peel force was used as the peel strength of the ceramic green sheet.

[0629] Low-speed peelability was evaluated based on the peel strength of the ceramic green sheet using the following benchmarks.

[0630] AA: Peel strength ≤ 0.10 N / 25 mm

[0631] A: 0.10N / 25mm < peel strength ≤ 0.15N / 25mm

[0632] B: 0.15N / 25mm < peel strength ≤ 0.25N / 25mm

[0633] C: 0.25N / 25mm < peel strength ≤ 0.35N / 25mm

[0634] D: Peel strength exceeds 0.35N / 25mm or the ceramic green sheet breaks during peeling.

[0635] (High-speed peelability)

[0636] The peeling speed was changed from 0.3 m / min to 3 m / min. Otherwise, the high-speed peeling performance was evaluated based on the peeling strength of the ceramic green sheet using the same method as for evaluating low-speed peeling performance.

[0637] AA: Peel strength ≤ 0.10 N / 25 mm

[0638] A: 0.10N / 25mm < peel strength ≤ 0.15N / 25mm

[0639] B: 0.15N / 25mm < peel strength ≤ 0.25N / 25mm

[0640] C: 0.25N / 25mm < peel strength ≤ 0.35N / 25mm

[0641] D: Peel strength exceeds 0.35N / 25mm or the ceramic green sheet breaks during peeling.

[0642] The results of the above physical property measurements and performance evaluations are shown in the table below.

[0643] In the table below, monomers A1 to A4 and neutralizing agents are components used in the synthesis of acrylic resins. The definitions of monomers A1 to A3 are as described above, and monomer A4 refers to a monomer that does not correspond to monomers A1 to A3.

[0644] Furthermore, in the table below, A / B refers to the "content of acrylic resin A / content of crosslinking agent B" in the release layer forming composition. Also, in the table below, A / C / B / D refers to the "content of acrylic resin A / content of other polymer C / content of crosslinking agent B / content of other additive D" in the release layer forming composition.

[0645] Furthermore, the "Maximum Protrusion Height Sp (nm)" column in the table below shows the maximum protrusion height Sp (unit: nm) on the surface of the release layer.

[0646] Through proton nuclear magnetic resonance ( 1 The mass ratio of each structural unit of acrylic resin A was determined by ¹H-NMR, and the result was the same as the loading ratio of the monomer.

[0647] The release layers in the embodiments are all formed from a composition containing an acrylic resin A having structural units derived from monomer A2 and a crosslinking agent B. The release layers are heated during formation, so they can be said to have a crosslinked structure.

[0648] [Table 1]

[0649]

[0650] [Table 2]

[0651]

[0652] [Table 3]

[0653]

[0654] As shown in the table above, the following is illustrated: A polyester film comprising a release layer and a polyester substrate, wherein the release layer comprises an acrylic resin, the polyester film having a water slip angle of less than 90°C on the surface of the release layer and a thickness of less than 200 nm exhibits excellent coatability to compositions (ceramic slurry) containing organic solvents and excellent high-speed peelability of sheets (ceramic green sheets) formed on the surface of the release layer (Example).

[0655] According to the comparison of Examples 1 to 19, when using acrylic resin A with structural units derived from monomer A3 with a ClogP value of 0.8 or higher, the high-speed peelability of the sheet (ceramic green sheet) formed on the surface of the release layer is superior.

[0656] The comparison of Examples 2, 20-28 shows that as long as the thickness of the release layer is 7 nm or more, the high-speed and low-speed peelability of the sheet (ceramic green sheet) formed on the surface of the release layer is superior. Furthermore, the comparison of Examples 2, 20-28 shows that as long as the thickness of the release layer is less than 90 nm, the appearance (roll appearance) of the polyester film when made into a roll is superior; moreover, as long as the thickness of the release layer is less than 70 nm, the roll appearance is further superior.

[0657] The comparison of Examples 1 and 32 shows that as long as the surface Si ratio (silicon atom content on the surface of the release layer) is 2 atm% or more, the high-speed and low-speed peeling properties of the sheet (ceramic green sheet) formed on the surface of the release layer are better.

[0658] The comparisons in Examples 2 and 32-35 show that when acrylic resin A with an acid value of 4.5 mmol / g or less is used, the high-speed peelability of the sheet (ceramic green sheet) formed on the surface of the release layer is better, and when acrylic resin A with an acid value of 3.0 mmol / g or less is used, the low-speed peelability of the sheet (ceramic green sheet) formed on the surface of the release layer is better.

[0659] The comparisons of Examples 1, 36, 37, and 45 show that when using acrylic resin A containing structural units derived from monomer A1 with a molecular weight of less than 4000, the high-speed peelability of the sheet formed on the surface of the release layer is superior.

[0660] The comparisons of Examples 1, 38, 39, and 45 show that when acrylic resin A with a linear polysiloxane structure is used, the high-speed peelability of the sheet formed on the surface of the release layer is superior.

[0661] The comparison of Examples 1, 40, and 41 shows that when acrylic resin A with structural units derived from methacrylic acid is used, the low-speed peelability of the sheet formed on the surface of the release layer is better.

[0662] In contrast, it is shown that when the release layer does not contain acrylic resin or the water slip angle on the surface of the release layer is not 90° or less ("does not slip") or the thickness of the release layer is 200 nm or more, at least one of the coating properties of the composition containing organic solvent (ceramic slurry) and the peelability of the sheet formed on the surface of the release layer (ceramic green sheet) is worse (Comparative Examples 1 to 4).

[0663] Symbol Explanation

[0664] 2A~2L - Holding component, 3 - Clamp closure, 4 - Support component, 5 - Clamp opener, 10 - Preheating section, 20 - Stretching section, 30 - Heat setting section, 40 - Heat relaxation section, 50 - Cooling section, 60a, 60b - Annular guide rail, 100 - Stretching machine, 200 - Film, 300 - Polyester film, 310 - Polyester substrate, 320 - Release layer, 321 - One side, 322 - The other side (release layer surface, release surface), P, Q - Holding release point, MD - Conveying direction (length direction), TD - Width direction, L0, L1, L2, L3 - Film width.

Claims

1. A polyester film comprising a release layer and a polyester substrate, The release layer comprises an acrylic resin. The water slippage angle on the surface of the peeling layer is less than 90°. The thickness of the release layer is less than 200 nm.

2. The polyester film according to claim 1, wherein, The silicon atom content on the surface of the release layer is less than 25 atm%.

3. The polyester film according to claim 1 or 2, wherein, The polyester substrate is essentially free of particles. The maximum protrusion height Sp on the surface of the release layer is less than 35 nm.

4. The polyester film according to claim 1 or 2, wherein, The thickness of the release layer is less than 90 nm.

5. The polyester film according to claim 1 or 2, wherein, The stripping layer has a structure represented by -Si(R)3, where R independently represents either an alkyl or an aryl group.

6. The polyester film according to claim 1 or 2, wherein, The release layer comprises a crosslinker of acrylic resin A with siloxane bonds and crosslinking agent B.

7. The polyester film according to claim 6, wherein, The acrylic resin A contains structural units derived from monomer A1, which is an acrylic monomer with siloxane bonds. The molecular weight of the monomer A1 is below 4000.

8. The polyester film according to claim 1 or 2, used for manufacturing ceramic green sheets.

Images