Release film

Abstract

To provide a release film for ceramic green sheet production capable of suppressing the defects of a ceramic green sheet upon ceramic green sheet production and having excellent releasability of the ceramic green sheet.SOLUTION: A release film for ceramic green sheet production comprises: a release layer; a polyester substrate not substantially comprising particles; and a particle-comprising layer in this order. In the surface on the side opposite to the polyester substrate of the release layer, an indentation elastic modulus measured by a nanoindentation method is 3.0 GPa or more, the surface on the side opposite to the polyester substrate of the particle-comprising layer has a protrusion part, and, in a region other than the protrusion part of the surface on the side opposite to the polyester substrate of the particle-comprising layer, an indentation elastic modulus measured by an atomic force microscope is 8.0 GPa or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a release film. [Background technology]

[0002] As electronic devices become more high-performance and smaller, there is a growing demand for higher performance and smaller size in the electronic components used in them. Among electronic components, multilayer ceramic capacitors, for example, are seeing an increase in the number of points they can be mounted on a circuit board, and there is a strong demand for miniaturization. In the manufacture of multilayer ceramic capacitors, a common method involves applying a ceramic slurry onto a release film having a release layer and drying it to form a ceramic green sheet. Furthermore, to prevent the front and back surfaces of the release film from sticking together (blocking) when the film is wound up, it is common practice to create irregularities on the surface of the side of the release film opposite the release layer, for example, by incorporating particles.

[0003] In the release film used for the above-mentioned ceramic green sheet manufacturing, a technique is known to improve release properties by increasing the elastic modulus of the release layer. For example, Patent Document 1 discloses a release film that uses a polyester film substantially free of inorganic particles as a base material, has a release coating layer on one surface of the base material, and has a smooth coating layer containing particles on the other surface of the base material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2019 / 065214 [Overview of the project] [Problems that the invention aims to solve]

[0005] On the other hand, with the recent miniaturization of ceramic capacitors, there is a demand for thinner ceramic green sheets. Thinner ceramic green sheets have been required to suppress even minute defects.

[0006] The present inventors have found that when they manufacture ceramic green sheets using the release film for manufacturing ceramic green sheets described in Patent Document 1, defects may occur in the ceramic green sheets. Furthermore, the release film is required to exhibit excellent release properties for the manufactured ceramic green sheet.

[0007] In view of the above circumstances, the present invention aims to provide a release film for manufacturing ceramic green sheets that can suppress defects in ceramic green sheets during manufacturing and has excellent release properties for ceramic green sheets. [Means for solving the problem]

[0008] The inventors of this invention have diligently studied and developed the present invention to solve the above problems. Specifically, they have found that the above problems can be solved by the following configuration.

[0009] [1] A release film for manufacturing ceramic green sheets, having in this order a release layer, a polyester substrate substantially free of particles, and a particle-containing layer, On the surface of the above-mentioned release layer opposite to the above-mentioned polyester substrate, the indentation modulus measured by nanoindentation is 3.0 GPa or higher. The surface of the particle-containing layer opposite to the polyester substrate has a convex portion. A release film in which the indentation modulus measured by atomic force microscopy is 8.0 GPa or less in the region other than the convex portion on the surface of the particle-containing layer opposite to the polyester substrate. [2] The release film according to [1], wherein the indentation modulus measured by nanoindentation on the surface of the release layer opposite to the polyester substrate is 6.0 GPa or less. [3] The release film according to [1] or [2], wherein the particle-containing layer contains inorganic particles, and the maximum protrusion height on the surface of the particle-containing layer opposite to the polyester substrate is 300 nm or less. [4] The release film according to [1] or [2], wherein the particle-containing layer contains organic particles. [5] The surface free energy of the surface of the release layer opposite to the polyester substrate is 10 to 35 mJ / cm². 2 The release film is one of the following: [1] to [4]. [6] The release film according to any one of [1] to [5], wherein the release layer contains a silicone resin. [7] The release film described in any one of [1] to [6], wherein the thickness of the release film is 40 μm or less. [8] A release film according to any one of [1] to [7], wherein the thickness of the particle-containing layer is 1 to 500 nm. [9] The release film according to any one of [1] to [8], wherein the particle-containing layer contains at least one surfactant selected from the group consisting of hydrocarbon surfactants and fluorine-based surfactants having a perfluoroalkyl group having 1 to 4 carbon atoms. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress defects in ceramic green sheets during manufacturing and provide a release film for manufacturing ceramic green sheets that has excellent peelability. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing an example of the structure of the release film according to the present invention. [Modes for carrying out the invention]

[0012] Hereinafter, the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0013] In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical ranges described in other stepwise descriptions. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In this specification, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In this specification, the term "step" includes not only an independent step but also cases where it cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0014] In this specification, the "longitudinal direction" means the longitudinal direction of the release film during the production of the release film, and is synonymous with the "transport direction" and the "machine direction". In this specification, the "width direction" means a direction perpendicular to the longitudinal direction. In this specification, "orthogonal" is not limited to strict orthogonality, but includes substantially orthogonal. "Substantially orthogonal" means intersecting within the range of 90° ± 5°, preferably intersecting within the range of 90° ± 3°, and more preferably intersecting within the range of 90° ± 1°. Also, in this specification, the "film width" means the distance between both ends in the width direction of the release film.

[0015] <构 <Configuration><00001><006>The structure of the release film of the present invention (hereinafter also simply referred to as "release film") will be described with reference to the drawings. Figure 1 is a cross-sectional view showing an example of the structure of a release film. The release film 1 has a release layer 2, a polyester substrate 4, and a particle-containing layer 6 in that order. The release film of the present invention is not limited to the embodiment shown in Figure 1, and may have an intermediate layer between the release layer 2 and the polyester substrate 4, and / or between the polyester substrate 4 and the particle-containing layer 6.

[0016] The characteristic features of the release film of the present invention are that it has the above configuration, the indentation modulus measured by nanoindentation on the surface of the release layer opposite to the polyester substrate is 3.0 GPa or more, the surface of the particle-containing layer opposite to the polyester substrate has a convex portion, and the indentation modulus measured by atomic force microscope (AFM) is 8.0 GPa or less in the region of the surface of the particle-containing layer opposite to the polyester substrate other than the convex portion. The mechanism by which defects are suppressed and the ceramic green sheet exhibits excellent peelability when using a release film that satisfies the above characteristics is not entirely clear, but the inventors speculate as follows. During use, the release film undergoes handling, such as during transport and winding. During this handling (especially during the transport of the release film), a part of the handling equipment may come into contact with particles in the particle-containing layer, causing force to act on the particles in the particle-containing layer, which can cause the particles to detach from the particle-containing layer and eventually adhere to the surface of the release layer. If a ceramic green sheet is formed on the release layer with particles adhering to its surface, defects are likely to occur in the ceramic green sheet due to the adhering particles. Here, if the indentation modulus measured by AFM on the surface of the particle-containing layer opposite the polyester substrate is 8.0 GPa or less, it is thought that even if force is applied to the particles in the particle-containing layer, the particle-containing layer will deform easily, making it less likely for the particles to fall off. As a result, defects in the ceramic green sheet during manufacturing can be suppressed. Furthermore, the indentation modulus of elasticity measured by nanoindentation on the surface of the release layer opposite the polyester substrate is 3.0 GPa or higher, resulting in excellent release properties for the ceramic green sheet, and preventing particles detached from the particle-containing layer from adhering to the release layer. In addition, because the indentation modulus of elasticity in both the particle-containing layer and the release layer is within the above range, even if the particles in the particle-containing layer come into contact with the release layer during winding of the release film, deformation of the release layer is suppressed, preventing the transfer of particle shapes to the release layer, and further suppressing defects in the ceramic green sheet during manufacturing. Furthermore, the release film of the present invention has a structure comprising a polyester substrate that substantially does not contain particles and a coating layer that contains particles, which improves the smoothness of the film. This suppresses the formation of transfer marks on the surface of the release layer, thereby suppressing defects in the ceramic green sheet during manufacturing.

[0017] The following describes each layer of the release film of the present invention. The manufacturing method of the release film and the manufacturing method of each layer will be described later.

[0018] <Exfoliation layer> The release layer is a layer provided on the side of the polyester substrate opposite to the side where the particle-containing layer is provided, and the ceramic green sheet is manufactured on the release layer. On the release layer, the ceramic green sheet is manufactured in a way that allows it to be peeled off. The release layer may be provided directly on the surface of the polyester substrate, or it may be provided on the polyester substrate via another layer, but it is preferable to provide it directly on the surface of the polyester substrate in terms of superior smoothness.

[0019] The composition of the release layer is not particularly limited as long as it can be manufactured in a way that allows the ceramic green sheet to be peeled off as described above, but it is preferable that it contains a release agent. The components contained in the exfoliation layer are described in detail below.

[0020] [Removal agent] The release agent is preferably a resin. The resin used as a release agent is not particularly limited, but examples include silicone resin, fluororesin, alkyd resin, acrylic resin, various waxes, and aliphatic olefin. Silicone resin is preferred because it offers superior release properties for ceramic green sheets. The release agent preferably has a cross-linked structure. In other words, the release layer is preferably a cross-linked film. To form a release agent having a crosslinked structure, one method is to form a release layer using a release layer-forming composition containing a crosslinking agent, as described later.

[0021] Silicone resin refers to a resin that has a silicone structure within its molecule. Examples of silicone resins include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified resins, with reactive curable silicone resins being preferred. Examples of reactive curable silicone resins include addition reaction-type silicone resins, condensation reaction-type silicone resins, and ultraviolet or electron beam curable silicone resins.

[0022] Examples of silicone resins used in addition reactions include resins obtained by reacting polydimethylsiloxane, which has vinyl groups introduced to its terminals or side chains, with hydrodienesiloxane using a platinum catalyst and then curing the reaction. Examples of silicone resins used in condensation reactions include resins having a three-dimensional crosslinked structure, formed by condensing polydimethylsiloxane having OH groups at its ends with polydimethylsiloxane having H groups at its ends using an organotin catalyst. Examples of UV-curable silicone resins include those that utilize the same radical reaction as silicone rubber crosslinking, those that are photocured by introducing unsaturated groups, those that decompose onium salts with ultraviolet light or electron beams to generate strong acids, which then cleave epoxy groups and cause crosslinking, and those that are crosslinked by the addition reaction of thiols to vinylsiloxane. More specifically, examples include acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane.

[0023] [Other resins] The release layer may contain resins other than the release agent (hereinafter also referred to as "other resins") in addition to the resin used as a release agent. Other resins that are known can be used. Examples of other resins include UV-curable resins and thermosetting resins. Specifically, examples include acrylic resins, unsaturated polyester resins, melamine resins, epoxy resins, phenolic resins, and urethane resins. In the release layer forming composition described later, other resins may be included along with a polymerization initiator and / or catalyst, and the release layer may contain residues of the polymerization initiator and / or catalyst.

[0024] [Additives] The release layer may contain additives in addition to the resin and other resins used as release agents. These additives may include light and heavy release additives for adjusting the release force, adhesion enhancers, and antistatic agents.

[0025] The resin used as a release agent in the release layer may be used alone or in combination of two or more types. The content of the resin used as a release agent in the release layer is preferably 0.1 to 98% by mass, and more preferably 0.5 to 50% by mass, relative to the total mass of the release layer. The content of other resins in the release layer is preferably 0 to 98% by mass, and more preferably 1 to 95% by mass, relative to the total mass of the release layer. The remainder of the release layer other than the resin used as a release agent and other resins may be the additives and / or residues of solvents, polymerization initiators, and catalysts contained in the release layer forming composition (described later) used to form the release layer.

[0026] [Properties of the release layer] (Indentation modulus) On the surface opposite the polyester substrate of the release layer, the indentation modulus measured by nanoindentation is 3.0 GPa or higher. By achieving an indentation modulus of 3.0 GPa or higher, as described above, defects in the ceramic green sheet during manufacturing can be suppressed, and the release properties of the ceramic green sheet are considered to be excellent. The upper limit of the indentation modulus is preferably 6.0 GPa or less. The indentation modulus of the release layer is obtained by measuring it using the nanoindentation method on the surface of the release layer opposite to the polyester substrate of the release film. A detailed measurement method will be described later. The indentation modulus of the release layer can be adjusted by the type and amount of resin, other resins, and / or additives used as the release agent.

[0027] (Thickness) The thickness of the release layer is preferably 10 to 1000 nm, and more preferably 30 to 700 nm, in order to achieve a good balance between release performance and surface smoothness of the release layer. The thickness of the release layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM). The arithmetic mean of these thicknesses is then used.

[0028] (Surface free energy of the delamination surface) The surface free energy of the surface of the release layer opposite the polyester substrate (hereinafter also referred to as the "release surface") is 5 to 50 mJ / m 2 Preferably, 10-35 mJ / m 2 This is preferable. Because the surface free energy of the peeling surface is within the above range, the ceramic green sheet is easily peeled off, and the coating properties of the ceramic slurry when manufacturing the ceramic green sheet are good. The surface free energy of the delamination surface can be adjusted by the type of resin and additives used to form the delamination layer.

[0029] The surface free energy of the peeled surface can be determined by using a contact angle meter (for example, "DROPMASTER-501" manufactured by Kyowa Interface Chemical Co., Ltd.) at 25°C, dropping droplets of purified water, methylene iodide, and ethylene glycol onto the peeled surface, measuring the contact angle 1 second after the droplets adhere to the surface, and calculating the energy from the obtained contact angles according to the Kitazaki-Hata method. The "surface free energy" obtained by the above method is the sum of the polar component and the hydrogen bonding component of the surface free energy.

[0030] (Maximum protrusion height Sp on the peeled surface, average surface roughness Sa) In order to ensure a smooth ceramic green sheet is formed on the peel surface, it is preferable that the peel surface be as smooth as possible. Specifically, the maximum protrusion height Sp of the peel surface is preferably 1 to 60 nm, and more preferably 1 to 40 nm. Furthermore, the average surface roughness Sa of the peeled surface is preferably 0 to 10 nm, more preferably 0 to 5 nm, and even more preferably 0 to 2 nm. The maximum protrusion height Sp and average surface roughness Sa of the release surface can be adjusted by not incorporating particles into the release layer when forming it, and by selecting the resin and additives that form the release layer.

[0031] The maximum protrusion height Sp and average surface roughness Sa of the delamination surface are determined by measuring the surface of the delamination surface using an optical interferometer (Hitachi High-Tech Corporation's "Vertscan 3300G Lite") under the following conditions, and then analyzing the data using the built-in data analysis software. For measuring the maximum protrusion height Sp, five measurements are taken at different positions, and the maximum value obtained is taken as the maximum protrusion height Sp (indicated as P in the built-in data analysis software). Similarly, for measuring the average surface roughness Sa, five measurements are taken at different positions, and the average value obtained is taken as the average surface roughness Sa. The specific measurement conditions are as follows: Measurement mode: WAVE mode Objective lens: 50x Measurement area: 186μm×155μm

[0032] <Polyester base material> A polyester substrate is a film-like object containing polyester resin as its main polymer component. Here, "main polymer component" refers to the polymer that is present in the largest quantity (by mass) of all polymers contained in the film-like object. The polyester substrate may contain one type of polyester resin, or it may contain two or more types of polyester resins.

[0033] [Polyester resin] Polyester resins are polymers having ester bonds in their main chain. Polyester resins are usually formed by polycondensation of dicarboxylic acid compounds and diol compounds, as described later. The polyester resin is not particularly limited, and known polyester resins can be used. Examples of polyester resins include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), and copolymers thereof. Among these, at least one selected from the group consisting of polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), and copolymers thereof is preferred, with PET being preferred.

[0034] The intrinsic viscosity of the polyester resin is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g. The melting point (Tm) of the polyester resin is preferably 220 to 270°C, and more preferably 245 to 265°C. The glass transition temperature (Tg) of the polyester resin is preferably 65 to 90°C, and more preferably 70 to 85°C.

[0035] The method for producing polyester resin is not particularly limited, and known methods can be used. For example, polyester resin can be produced by polycondensation of at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst. The following describes the materials used in the manufacture of polyester and the manufacturing conditions.

[0036] (Dicarboxylic acid compounds) Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or methyl aromatic dicarboxylic acids are preferred.

[0037] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, dimer acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of alicyclic dicarboxylic acid compounds include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

[0038] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfisoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorenic acid, as well as their methyl esters. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, with terephthalic acid being more preferred.

[0039] Dicarboxylic acid compounds may be used individually or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or copolymerized with other aromatic dicarboxylic acids such as isophthalic acid, or with aliphatic dicarboxylic acids.

[0040] (Diol compounds) Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0041] Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred. Examples of alicyclic diol compounds include cyclohexanedimethanol, spiroglycol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. Diol compounds may be used individually or in combination of two or more.

[0042] (catalyst) The catalyst used in the production of polyester resin is not particularly limited, and any known catalyst usable for the synthesis of polyester resin can be used. Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds are preferred from the viewpoint of catalytic activity and cost. The catalyst may be used alone or in combination of two or more. It is preferable to use at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds in combination with a phosphorus compound, and more preferably to use a titanium compound and a phosphorus compound in combination.

[0043] As the titanium compound, organic chelate titanium complexes are preferred. Organic chelate titanium complexes are titanium compounds that have an organic acid as a ligand. Examples of organic acids include citric acid, lactic acid, trimellitic acid, and malic acid. As a titanium compound, the titanium compounds described in paragraphs

[0049] to

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

[0044] (Terminal encapsulant) In the manufacture of polyester resin, end encapsulants may be used as needed. By using end encapsulants, structures derived from the end encapsulant are introduced to the ends of the polyester resin. The end-captive agent is not limited, and known end-captive agents can be used. Examples of end-captive agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds. As end-capturing agents, refer to the contents described in paragraphs

[0055] to

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

[0045] (Manufacturing conditions) The reaction temperature is not limited and can be set appropriately depending on the raw materials. A reaction temperature of 260 to 300°C is preferred, and 275 to 285°C is more preferred. The pressure is not limited and should be set appropriately according to the raw materials. The pressure is 1.33 × 10⁻⁶. -3 ~1.33 × 10 -5 MPa is preferred, 6.67 × 10 -4 ~6.67×10 -5 MPa is more preferable.

[0046] As a method for synthesizing polyester resin, the method described in paragraphs

[0033] to

[0070] of Japanese Patent Publication No. 5575671 can also be used, and the contents of the above publication are incorporated herein.

[0047] [Orientation] The polyester substrate is preferably a biaxially oriented polyester substrate. "Biaxial orientation" refers to the property of having molecular orientation in two axial directions. Molecular orientation is measured using a microwave transmission molecular orientation meter (e.g., MOA-6004, manufactured by Oji Instruments Co., Ltd.). The angle between the two axial directions is preferably within the range of 90°±5°, more preferably within the range of 90°±3°, and even more preferably within the range of 90°±1°. The biaxially oriented polyester substrate in the release film of the present invention preferably has molecular orientation in the longitudinal direction and the width direction. The biaxially oriented polyester substrate can be manufactured by the method described later.

[0048] [Polyester resin content] The polyester resin content in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polymer in the polyester substrate. There is no particular upper limit to the polyester resin content, and it can be appropriately set within a range of, for example, 100% by mass or less relative to the total mass of the polymer in the polyester substrate. When the polyester substrate contains polyethylene terephthalate, the polyethylene terephthalate content is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 100% by mass, relative to the total mass of polyester resin in the polyester substrate.

[0049] The polyester substrate may contain components other than polyester resin (for example, catalysts, unreacted raw material components, particles, and water). From the viewpoint of improving the smoothness of the release film, it is preferable that the polyester substrate is substantially free of particles. Examples of particles include those contained in the particle-containing layer described later. "Substantially free of particles" means that for a polyester base material, when quantitatively analyzing elements derived from particles by fluorescent X-ray analysis, the content of particles is defined as 50 mass ppm or less with respect to the total mass of the polyester base material, preferably 10 mass ppm or less, and more preferably below the detection limit. This is because even if particles are not actively added to the polyester base material, contamination components derived from foreign matter, raw resin, or dirt adhering to the line or equipment in the manufacturing process of the polyester base material may peel off and mix into the polyester base material.

[0050] [Density] The density of the polyester base material is preferably 1.39 - 1.41 g / cm 3 more preferably 1.395 - 1.405 g / cm 3 even more preferably 1.398 - 1.400 g / cm 3 is even more preferred. The density of the polyester base material can be measured using an electronic specific gravity meter (product name "SD - 200L", manufactured by Alpha Mirage Co., Ltd.).

[0051] [Thickness] The thickness of the polyester base material is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less in terms of controlling peelability. The lower limit of the thickness is not particularly limited, but in terms of improving strength and workability, 3 μm or more is preferred, 4 μm or more is more preferred, and 10 μm or more is even more preferred. The thickness of the polyester base material shall be measured using a continuous stylus type thickness gauge. Specifically, the thickness of the polyester base material is measured with a continuous stylus type thickness gauge over 10 m along the longitudinal direction. This measurement is performed at 5 different positions in the width direction. The arithmetic mean value of the obtained measurement values is taken as the thickness. In addition, the thickness of the polyester base material may be obtained by measuring the thickness of the release film by the above method and then subtracting the thickness of the release layer obtained by the above method and the thickness of the particle-containing layer obtained by the method described below from the obtained thickness of the release film.

[0052] [Particle-containing layer] A particle-containing layer refers to a layer that contains particles. The particle-containing layer is a layer provided on the surface of the polyester substrate opposite to the side where the release layer is provided, and it can improve the transportability of the release film. Specifically, it can improve winding quality (suppress blocking), suppress the occurrence of scratches and defects during transport, and reduce transport wrinkles during high-speed transport. Furthermore, in the particle-containing layer, the surface of the particle-containing layer opposite to the polyester substrate has a convex portion. Here, the convex portion refers to a protruding part formed by the particles contained in the particle-containing layer. Furthermore, in the region of the particle-containing layer opposite the polyester substrate, excluding the convex portion, the indentation modulus measured by atomic force microscopy is 8.0 GPa or less. The particle-containing layer may be provided directly on the surface of the polyester substrate, or it may be provided on the surface of the polyester substrate via another layer, but it is preferable to provide it directly on the surface of the polyester substrate in terms of superior productivity.

[0053] Furthermore, the particle-containing layer preferably contains a binder. In addition to the binder, the particle-containing layer may also contain additives. The particles and additives are described below.

[0054] (particle) The average particle size of the particles contained in the particle-containing layer is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 50 to 500 nm in terms of superior transportability and suppression of transfer marks. Furthermore, in terms of superior transportability and suppression of transfer marks, it is preferable that the average particle diameter of the particles contained in the particle-containing layer is 50 to 500 nm, the thickness of the particle-containing layer is 1 to 200 nm (more preferably 30 to 130 nm), and the average particle diameter of the particles is greater than the thickness of the particle-containing layer. When the particle-containing layer is formed by coating, by making the average particle diameter of the particles greater than the thickness of the particle-containing layer, a protrusion can be formed on the surface of the particle-containing layer opposite to the polyester substrate.

[0055] The particles contained in the particle-containing layer may be one type alone, or two or more types of particles may be used. When the particle-containing layer contains two or more particles with different particle sizes, it is preferable that the particle-containing layer contains at least one particle whose average particle size is within the above range, and it is more preferable that all two or more particles with different particle sizes have an average particle size within the above range.

[0056] Examples of particles contained in the particle-containing layer include organic particles and inorganic particles. As organic particles, resin particles are preferred. Examples of resins constituting the resin particles include acrylic resins such as polymethyl methacrylate (PMMA), polyester resins, silicone resins, and styrene-acrylic resins. The resin particles may or may not have a crosslinked structure. Specifically, examples include non-crosslinked acrylic resin particles, crosslinked acrylic resin particles, and divinylbenzene crosslinked particles. In this specification, "acrylic resin" means a resin containing constituent units derived from acrylate or methacrylate. Examples of inorganic particles include silica particles (silicon dioxide particles, colloidal silica), titania particles (titanium oxide particles), calcium carbonate, barium sulfate, and alumina particles (aluminum oxide particles). Among these, silica particles are preferred from the viewpoint of improving haze and durability.

[0057] The shape of the particles is not particularly limited and can be, for example, rice grain-shaped, spherical, cubic, spindle-shaped, flaky, aggregated, or irregular. Aggregated means a state in which primary particles are aggregated. The shape of the aggregated particles is not limited, but spherical or irregular shapes are preferred.

[0058] As the aggregated particles, fumed silica particles are preferred. A commercially available example is the Aerosil series from Nippon Aerosil Co., Ltd. Colloidal silica particles are preferred as non-aggregated particles. Examples of commercially available products include the Snowtex series manufactured by Nissan Chemical Corporation.

[0059] From the viewpoint of transportability and coatability of the release layer, the particle content in the particle-containing layer is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, and even more preferably 1 to 15% by mass, relative to the total mass of the particle-containing layer. Furthermore, the particle content is preferably 0.0001 to 0.01% by mass, and more preferably 0.0005 to 0.005% by mass, relative to the total mass of the polyester substrate.

[0060] (binder) The particle-containing layer preferably contains a binder. A resin binder is preferred as the binder. A non-polyester resin is preferred as the resin binder, and examples include acrylic resin, urethane resin, polyester resin, and olefin resin. The binder is preferably formed by coating it with an aqueous dispersion. Furthermore, acrylic resin, urethane resin, or olefin resin is preferred as the binder. The acrylic resin, urethane resin, or olefin resin is not particularly limited, and known resins can be used. Furthermore, the resin binder may be an acid-modified resin. In other words, the resin binder may be a resin having acid groups or acid anhydride groups.

[0061] Acrylic resin is a resin containing structural units derived from (meth)acrylate, and may also be copolymerized with vinyl monomers such as styrene. The acrylic resin is not particularly limited, but it is preferable to contain structural units derived from (meth)acrylate having alkyl groups having 1 to 12 carbon atoms, and more preferable to contain structural units derived from (meth)acrylate having alkyl groups having 1 to 8 carbon atoms. The acrylic resin may contain an acid-modified component. The acrylic resin may contain constituent units derived from (meth)acrylic acid as the acid-modified component. Furthermore, the (meth)acrylic acid may form an acid anhydride or be neutralized with at least one selected from alkali metals, organic amines, and ammonia.

[0062] The acid value of the acrylic resin is preferably 30 mg KOH / g or less, and more preferably 20 mg KOH / g or less. The lower limit of the acid value is not particularly limited, for example, 0 mg KOH / g, but from the perspective of coating as an aqueous dispersion, 2 mg KOH / g or more is preferred. When an acrylic resin with a solubility parameter (SP value) far removed from that of a polyester resin is used, the compatibility between the acrylic resin and the polyester resin becomes insufficient, resulting in improved defect suppression during long-term storage. Such an acrylic resin can be obtained, for example, by adjusting it to satisfy at least one of the following: setting the acid value within the above range, and including constituent units derived from (meth)acrylate having an alkyl group with 1 to 12 carbon atoms. Adjusting it to satisfy both of the above conditions—setting the acid value within the above range and including constituent units derived from (meth)acrylate having an alkyl group with 1 to 12 carbon atoms—further improves defect suppression during long-term storage.

[0063] The olefin resin can be any resin that contains olefin-derived structural units in its main chain. Having an olefin structure in the main chain results in insufficient compatibility with polyester resins, which in turn improves the suppression of defects during long-term storage. The olefin is not particularly limited, but alkenes having 2 to 6 carbon atoms are preferred, ethylene, propylene, or hexene are more preferred, and ethylene is even more preferred. The olefin-derived structural units in the polyolefin are preferably 50 to 99 mol%, and more preferably 60 to 98%, relative to the total structural units of the polyolefin.

[0064] As the olefin resin, an acid-modified olefin resin is preferred. Examples of acid-modified olefin resins include copolymers obtained by modifying the above-mentioned olefin resin with an acid-modifying component such as an unsaturated carboxylic acid or its anhydride.

[0065] Examples of commercially available acid-modified olefin resins include the Zaixen® series (manufactured by Sumitomo Seika Co., Ltd.), such as Zaixen AC, A, L, NC, and N; the Chemipearl® series (manufactured by Mitsui Chemicals, Inc.), such as Chemipearl S100, S120, S200, S300, S650, and SA100; and the Hitec® series (manufactured by Toho Chemicals, Inc.), such as Hitec S3121 and S3148K. Examples include the Arrowbase (registered trademark) series (manufactured by Unitika Ltd.), such as Arrowbase SE-1013, SE-1010, SB-1200, SD-1200, SD-1200, DA-1010, DB-4010, Hardlen AP-2, NZ-1004, NZ-1005 (manufactured by Toyobo Co., Ltd.), and Sepolsion G315, VA407 (manufactured by Sumitomo Seika Co., Ltd.). Furthermore, the acid-modified olefin resin described in paragraphs

[0022] to

[0034] of Japanese Patent Publication No. 2014-076632 can also be preferably used.

[0066] The urethane resin is not limited as long as it is a polymer having urethane bonds, and known urethane resins such as reaction products of polyisocyanate compounds and polyol compounds can be used. When using an aqueous dispersion containing urethane resin in the production of a particle-containing layer, it is preferable that the aqueous dispersion contains a urethane resin having an acidic group (e.g., a carboxyl group), or contains a urethane resin and a dispersant. This improves the film-forming properties of the particle-containing layer. The desired SP value of the urethane resin can be achieved by adjusting, for example, at least one of the following: the structure of the raw material polyol compound, the hydrophobicity or hydrophilicity of the raw material polyol, the structure of the raw material polyisocyanate compound, and the hydrophobicity or hydrophilicity of the raw material polyisocyanate compound. By using a urethane resin adjusted to be hydrophobic in this way, the compatibility between the urethane resin and the polyester resin becomes insufficient, and as a result, defect suppression during long-term storage can be further improved. Among urethane resins, urethane resins having a polyester structure (polyester-based urethane resins) are preferred because they are hydrophobic and can further improve the suppression of defects during long-term storage. Examples of commercially available urethane resins include Hydran® AP-20, AP-40N, and AP-201 (all manufactured by DIC Corporation), Takelac® W-605, W-5030, and W-5920 (all manufactured by Mitsui Chemicals, Inc.), Superflex® 210 and 130, and Elastron® H-3-DF, E-37, and H-15 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0067] The binder contained in the particle-containing layer may have a cross-linked structure. In other words, the particle-containing layer may be a cross-linked film. To form a binder having a crosslinked structure, one method is to form a particle-containing layer using a particle-containing layer-forming composition containing a crosslinking agent, as described later.

[0068] The particle-containing layer may contain one type of binder or two or more types of binders. The binder content is preferably 30 to 99.8% by mass, and more preferably 50 to 99.5% by mass, relative to the total mass of the particle-containing layer, in terms of suppressing defects.

[0069] (Additives) The particle-containing layer may contain additives other than the above-mentioned particles and binder. Examples of additives included in the particle-containing layer include surfactants, waxes, antioxidants, UV absorbers, colorants, strengthening agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and mold inhibitors.

[0070] The particle-containing layer preferably contains a surfactant, as this improves the smoothness of the areas on its surface other than those where protrusions formed by the particles exist. The surfactant is not particularly limited and includes silicone-based surfactants, fluorine-based surfactants, and hydrocarbon-based surfactants, among which fluorine-based surfactants (especially fluorine-based surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms) and hydrocarbon-based surfactants are preferred.

[0071] The silicone-based surfactant is not particularly limited as long as it is a surfactant having a silicon-containing group as a hydrophobic group, and examples include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Examples of commercially available silicone-based surfactants include BYK(registered trademark)-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, and BYK-349 (all manufactured by BYK), as well as KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0072] The fluorine-based surfactant is not particularly limited as long as it is a surfactant having a fluorine-containing group as a hydrophobic group, and examples include perfluorooctanesulfonic acid and perfluorocarboxylic acid. Examples of commercially available fluorine-based surfactants include Megafac® F-114, F-410, F-440, F-447, F-553, and F-556 (all manufactured by DIC Corporation), and Surflon® S-211, S-221, S-231, S-233, S-241, S-242, S-243, S-420, S-661, S-651, and S-386 (manufactured by AGC Seimi Chemical Co., Ltd.). Furthermore, as a fluorine-based surfactant, from the viewpoint of improving environmental suitability, it is preferable to use a surfactant derived from a substitute material for a compound having a linear perfluoroalkyl group with 7 or more carbon atoms, such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

[0073] Furthermore, as a fluorine-based surfactant, it is preferable to use a surfactant having a perfluoroalkyl group with 1 to 4 carbon atoms compared to a surfactant having a linear perfluoroalkyl group with 6 or more carbon atoms, in order to improve the applicability of the release layer. The perfluoroalkyl group with 1 to 4 carbon atoms may be linear or branched. Among these, surfactants having a linear perfluoroalkyl group with 1 to 4 carbon atoms or a branched perfluoroalkyl group with 3 carbon atoms are more preferable, and surfactants having a perfluoroalkyl group with 1 or 2 carbon atoms or a branched perfluoroalkyl group with 3 carbon atoms are even more preferable. Examples of the above-mentioned perfluoroalkyl groups include CF3-*, C2F5-*, C3F7-*, n-C4F9-*, and (CF3)2CF-*. Here, * indicates the bonding position with carbon atoms other than those substituted with fluorine atoms. It is preferable that the carbon atoms bonded to these perfluoroalkyl groups either have hydrogen atoms or are bonded only to carbon atoms.

[0074] Examples of commercially available fluorine-based surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms include Futergent® 100, 100C, 110, 150, 150H, 212M, 215M, 250, 251, 222F, 245F, 208G, FTX-218, DFX-18, 300, 310, 320, 400SW, 710FL, 683, 601AD, 602A, and 681 (all manufactured by Neos Co., Ltd.), as well as PF-136A, PF-156A, PF-151N, PF-636, PF-6320, PF-656, PF-6520, and PF-652-NF (all manufactured by OMNOVA).

[0075] The reason why using surfactants with 1-4 carbon atoms in a perfluoroalkyl group improves the coating properties of the release layer compared to using surfactants with 6 or more carbon atoms in a linear perfluoroalkyl group is not entirely clear. However, surfactants with 1-4 carbon atoms in a perfluoroalkyl group contain a large number of CF3 groups per unit weight, which have low surface tension. Therefore, a small amount of additive can lower the surface tension of the coating solution. This is thought to suppress the release charging described later and improve the coating properties of the release layer.

[0076] Examples of hydrocarbon-based surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include alkyl sulfates, alkylbenzene sulfons, alkyl phosphates, and fatty acid salts. Examples of nonionic surfactants include polyalkylene glycol mono- or dialkyl ethers, polyalkylene glycol mono- or dialkyl esters, and polyalkylene glycol monoalkyl esters / monoalkyl ethers. Examples of cationic surfactants include primary to tertiary alkylamine salts and quaternary ammonium compounds. Examples of amphoteric surfactants include surfactants that have both anionic and cationic sites within their molecule.

[0077] Examples of commercially available anionic surfactants include Rapizole® A-90, A-80, BW-30, B-90, and C-70 (all manufactured by NOF Corporation), Nikkol® OTP-100 (all manufactured by Nikko Chemical Co., Ltd.), Kohacool® ON, L-40, and Phosphanol® 702 (all manufactured by Toho Chemical Industry Co., Ltd.), and Viewlight® A-5000 and SSS (all manufactured by Sanyo Chemical Industries, Ltd.). Examples of commercially available nonionic surfactants include Naroacty® CL-95 and HN-100 (product name: manufactured by Sanyo Chemical Industries, Ltd.), Risolex BW400 (product name: manufactured by Kofu Alcohol Industry Co., Ltd.), EMALEX® ET-2020 (all manufactured by Nippon Emulsion Co., Ltd.), and Surfinol® 104E, 420, 440, 465, and Dynol® 604, 607 (all manufactured by Nisshin Chemical Industry Co., Ltd.).

[0078] Among hydrocarbon-based surfactants, anionic surfactants and / or nonionic surfactants are preferred, and anionic surfactants are more preferred.

[0079] Anionic hydrocarbon surfactants are preferable to have multiple hydrophobic end groups in that they have improved smoothness. The hydrophobic end groups may be some of the hydrocarbon groups that the hydrocarbon surfactant has. For example, a hydrocarbon surfactant having a branched-chain hydrocarbon group at its end will have multiple hydrophobic end groups. Examples of anionic hydrocarbon surfactants having multiple hydrophobic end groups include sodium di-2-ethylhexyl sulfosuccinate (having four hydrophobic end groups), sodium di-2-ethyloctyl sulfosuccinate (having four hydrophobic end groups), and branched-chain alkylbenzene sulfonates (having two hydrophobic end groups).

[0080] One type of surfactant may be used, or two or more types may be used in combination. The surfactant content is preferably 0.1 to 10% by mass relative to the total mass of the particle-containing layer, more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 2% by mass, for superior surface smoothness.

[0081] The wax is not particularly limited and may be either natural or synthetic. Examples of natural waxes include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, the lubricants described in section

[0087] of International Publication No. 2017 / 169844 may also be used. The wax content is preferably 0 to 10% by mass relative to the total mass of the particle-containing layer.

[0082] [Properties of the particle-containing layer] (Indentation modulus) In the region of the particle-containing layer opposite the polyester substrate, excluding the convex portion, the indentation modulus measured by atomic force microscopy (AFM) is 8.0 GPa or less. By keeping the indentation modulus at 8.0 GPa or less, it is believed that defects in the ceramic green sheet during manufacturing can be suppressed, as described above. The indentation modulus of the particle-containing layer is preferably 7.0 GPa or less, and more preferably 5.5 GPa or less. The lower limit of the indentation modulus of the particle-containing layer is not particularly limited, but is 0.1 GPa or more, preferably 0.5 GPa or more, and more preferably 1.0 GPa or more. The indentation modulus of the particle-containing layer can be adjusted by the type and amount of binder, additives, and / or crosslinking agent used, as described later. In this specification, the method for measuring the indentation modulus of a particle-containing layer by AFM is as follows: In a region of the particle-containing layer other than the convex portion, the force exerted on the probe when it is brought close to the surface of the particle-containing layer, and the force exerted on the probe when it is moved away from the surface of the particle-containing layer, are measured to obtain a force curve that represents the relationship between the force exerted on the probe and the distance between the probe and the surface of the particle-containing layer. The modulus is determined from the slope of the force curve using the Hertz contact theory. The above measurement is performed five times in a 3.0 μm square field of view, and the indentation modulus of the particle-containing layer is determined from the arithmetic mean of the five fields of view. Details will be described later in the Examples section.

[0083] (Thickness) The particle-containing layer is often formed by coating a particle-containing composition onto one surface of a polyester substrate, resulting in a thickness of 1 μm or less. The particle-containing layer may also be formed by co-extruding the polyester resin forming the polyester substrate and the resin forming the particle-containing layer containing the particles, in which case the thickness of the particle-containing layer is often 1 to 10 μm. The thickness of the particle-containing layer is preferably 1 nm to 3 μm, more preferably 1 to 500 nm, even more preferably 10 to 200 nm, and particularly preferably 40 to 150 nm, from the viewpoint of suitability for manufacturing the particle-containing layer and haze reduction. The thickness of the particle-containing layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM), and taking the arithmetic mean of the thicknesses of these sections. If the particle-containing layer is soft and it is difficult to reliably prepare cross-sectional sections, measurement may be performed using a spectrophotometer. Specifically, the thickness of the particle-containing layer can be determined by fitting the measured reflectance spectrum to the thickness and refractive index of the particle-containing layer and the refractive index of the polyester substrate.

[0084] (Surface free energy of the particle-containing layer) The surface free energy on the surface of the particle-containing layer opposite the polyester substrate (hereinafter also simply referred to as the "surface of the particle-containing layer") is 25-65 mJ / m². 2 Preferably, 25-45 mJ / m 2 More preferably, 30-45 mJ / m 2 That is even more preferable. By keeping the surface free energy at the surface of the particle-containing layer within the above range, impurities such as oligomers contained in the polyester substrate are suppressed from precipitation on the particle-containing layer, thereby suppressing defects in the ceramic green sheet. Oligomers are low-molecular-weight by-products generated during the polymerization of polyesters and are present as impurities in polyester substrates.

[0085] (Maximum protrusion height Sp of the particle-containing layer, average surface roughness Sa) In order to further suppress defects in the ceramic green sheet during manufacturing, the maximum protrusion height Sp on the surface of the particle-containing layer is preferably 300 nm or less. In particular, when the particle-containing layer contains inorganic particles, the maximum protrusion height Sp on the surface of the particle-containing layer is preferably 300 nm or less. There is no particular lower limit to the maximum protrusion height Sp, but it is preferably 10 nm or more. Furthermore, the surface average roughness Sa on the surface of the particle-containing layer is preferably 0 to 10 nm, more preferably 0 to 5 nm, and even more preferably 1 to 3 nm. The method for measuring the maximum protrusion height Sp and average surface roughness Sa on the surface of the particle-containing layer is the same as the method for measuring the maximum protrusion height Sp and average surface roughness Sa on the delamination surface described above.

[0086] <Properties of the release film> [thickness] The thickness of the release film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less, in terms of superior release properties. Furthermore, the thickness of the release film is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, in terms of improved strength and processability. The thickness of the release film shall be the arithmetic mean of the thicknesses measured at five locations using a continuous stylus-type film thickness gauge.

[0087] [Amount of separation and falling charge] For polyester substrates with a particle-containing layer that do not have a release layer, the absolute value of the release charge between the surface of the particle-containing layer, which corresponds to a circle with a diameter of 1.5 cmφ, and the surface of the polyester substrate, measured by the following measurement method at a temperature of 23°C and a relative humidity (RH) of 20%, is preferably 0 to 0.12 nC (nanocoulombs), more preferably 0 to 0.11 nC, and even more preferably 0 to 0.1 nC. Here, the unit nC (nanocoulomb) is 10 -9 It is Coulomb. When the total value of the peeling charge is within the above range, foreign matter adhesion is less likely to occur when applying the peeling layer forming composition, which will be described later, resulting in good peeling layer application properties.

[0088] The method for measuring the amount of electrostatic charge on a polyester substrate with a particle-containing layer is as follows. The measuring device used comprises a platform on which a reference sample of a polyester substrate with a particle-containing layer (with the surface of the polyester substrate facing upwards) is placed, a head that can repeatedly press and peel the lower surface of the measurement sample against the upper surface of the reference sample by raising and lowering it vertically while holding the measurement sample of the polyester substrate with a particle-containing layer (with the surface of the particle-containing layer facing downwards), and an electrometer connected to this head that can measure the amount of charge of the measurement sample. More specifically, a polyester substrate with a particle-containing layer is cut into a circle with a diameter of 1.5 cm to prepare a measurement sample for measuring the amount of charge removed from the surface, and a rectangle measuring 13 cm x 4 cm is cut to prepare a reference sample for measuring the amount of charge removed from the surface. Next, the obtained samples of the polyester substrate with the particle-containing layer are left for at least two hours in the environment of the measurement temperature and humidity described above. After that, the reference sample is placed on the stand of the measuring device, and the measurement sample is attached to the head. At this time, the surface of the polyester substrate of the reference sample and the surface of the particle-containing layer of the measurement sample are positioned so that they face each other, with the surface of the polyester substrate on the stand facing upwards and the surface of the particle-containing layer of the measurement sample attached to the head facing downwards. After discharging static electricity from the measurement sample, the head is raised or lowered to repeatedly press and peel the reference film against the measurement sample (contact pressure is 566 g / cm²). 2 (Contact time 2 seconds). Using the same sample, measure the charge of the sample after each of the 1st to 5th peelings, and calculate the average of the measured values. Change the sample and the contact position of the sample with the reference sample for each sample, and perform measurements on a total of 4 samples. The average of all measurements is taken as the peeling charge. Measurements are performed in an environment with a temperature of 23°C and a relative humidity (RH) of 20%. Regarding the method for measuring the amount of electrostatic charge generated when peeling a polyester film, refer to the contents described in Japanese Patent Publication No. 2003-194865 (especially in sections

[0053] to

[0067] ), and the contents described in the above publication are incorporated herein by reference.

[0089] The amount of electrostatic charge on the peel can be adjusted by selecting the type and amount of the polyester substrate and the binder and surfactant components contained in the particle-containing layer. More specifically, the amount of electrostatic charge on the peel can be adjusted to the above range by selecting two materials that are closer in the triboelectric series from the group consisting of the polyester substrate, binder, and surfactant.

[0090] <Method for manufacturing release film> The method for producing the release film of the present invention will be described below. The method for producing the release film of the present invention is not particularly limited as long as a release film with the above-described properties can be obtained, and known methods can be used. In particular, the method for manufacturing the release film of the present invention is one that allows for the productive production of the release film, An extrusion molding process to form an unstretched polyester substrate by extrusion molding, The process includes a first stretching step of stretching an unstretched polyester substrate in either the conveying direction or the width direction to form a uniaxially oriented polyester substrate, and a second stretching step of stretching the uniaxially oriented polyester substrate in the other direction, the conveying direction or the width direction to form a biaxially oriented polyester substrate, performed either in stages or simultaneously. The process includes a particle-containing layer formation step, which is performed between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, by applying a particle-containing layer formation composition to one surface side of the polyester substrate to form a particle-containing layer. A manufacturing method is provided which includes a release layer forming step, performed between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, in which a release layer forming composition is applied to the other surface side of the polyester substrate to form a release layer. The preferred manufacturing method described above will be explained in detail below.

[0091] [Extrusion molding process] The extrusion molding process is a process of forming an unstretched polyester substrate by extrusion molding. More specifically, it is a process of extruding a molten resin containing the raw polyester resin into a film to form an unstretched polyester substrate. The raw polyester resin is the same as the polyester resin described in the (Polyester Resin) section above. Furthermore, in order to produce a polyester substrate that is substantially free of particles, it is preferable to use particle-free polyester pellets during the extrusion molding process.

[0092] Extrusion molding is a method of molding raw material resin into a desired shape by, for example, using an extruder to push out a molten raw material resin. The molten material extruded from the extrusion die is formed into a film by cooling. For example, the molten material can be formed into a film by bringing it into contact with a casting roll and cooling and solidifying it on the casting roll. In cooling the molten material, it is preferable to further apply air (preferably cold air) to the molten material.

[0093] [Stretching process] The stretching process is a process that involves performing, either in stages or simultaneously, a first stretching step in which an unstretched polyester substrate is stretched in either the conveying direction or the width direction to form a uniaxially oriented polyester substrate, and a second stretching step in which the uniaxially oriented polyester substrate is stretched in the other direction, either the conveying direction or the width direction, to form a biaxially oriented polyester substrate. One of the first and second stretching steps is a longitudinal stretching step in which the polyester substrate is stretched in the transport direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first and second stretching steps is a transverse stretching step in which the polyester substrate is stretched in the width direction (hereinafter also referred to as "transverse stretching"). During stretching, the polyester polymers are arranged in each respective direction.

[0094] The stretching process described above may be simultaneous biaxial stretching, where longitudinal stretching and transverse stretching are performed at the same time, or it may be sequential biaxial stretching, where longitudinal stretching and transverse stretching are performed in stages. Examples of sequential biaxial stretching include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, and longitudinal stretching → longitudinal stretching → transverse stretching, with longitudinal stretching → transverse stretching being preferred. The following describes the process of longitudinal stretching followed by transverse stretching, but the above manufacturing method is not limited to this process.

[0095] The stretching ratio in the longitudinal stretching process is set as appropriate, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 4.0 times. The stretching speed in the longitudinal stretching process is preferably 800 to 1500% / second, more preferably 1000 to 1400% / second, and even more preferably 1200 to 1400% / second. Here, "stretching speed" is the value obtained by dividing the length Δd of the polyester substrate stretched in the transport direction per second in the longitudinal stretching process by the length d0 of the polyester substrate in the transport direction before stretching, expressed as a percentage. In the longitudinal stretching process, it is preferable to heat the unstretched polyester substrate. This is because heating facilitates longitudinal stretching.

[0096] In the transverse stretching process, it is preferable to preheat the uniaxially oriented polyester substrate before transverse stretching. Preheating the uniaxially oriented polyester substrate allows for easy transverse stretching. The stretching ratio in the width direction (lateral stretching ratio) of the uniaxially oriented polyester substrate in the transverse stretching process is not particularly limited, but it is preferably greater 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. The stretching speed in the transverse stretching process is preferably 8 to 45% / second, more preferably 10 to 30% / second, and even more preferably 15 to 20% / second.

[0097] [Particle-containing layer formation process] The particle-containing layer formation process involves applying a particle-containing layer formation composition to one surface side of a polyester substrate to form a particle-containing layer. The particle-containing layer formation process is performed between the extrusion molding process and the first stretching process, between the first stretching process and the second stretching process, or after the stretching process. The particle-containing layer formed on one surface of the polyester substrate by the particle-containing layer formation process is synonymous with the layer described in the section on particle-containing layers above. The following describes how to apply the particle-containing layer-forming composition.

[0098] First, we will describe the composition for forming a particle-containing layer. A particle-containing layer-forming composition can be prepared by mixing particles contained in the particle-containing layer, a binder added as needed, an additive added as needed, and a solvent. Examples of solvents include water and alcoholic solvents.

[0099] The particle-containing layer-forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass, based on the total mass of the particle-containing layer-forming composition. In other words, in the particle-containing layer-forming composition, the total content of components other than the solvent (solids) is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass, relative to the total mass of the particle-containing layer-forming composition.

[0100] The particles contained in the particle-containing layer forming composition, the binder added as needed, and the additives added as needed, including their preferred embodiments, are as described in the section on particle-containing layers above. With respect to each component other than the solvent in the particle-containing layer-forming composition, it is preferable to adjust the content of each component in the particle-containing layer-forming composition so that the content of each component relative to the total mass of solids in the particle-containing layer-forming composition is the same as the preferred content of each component relative to the total mass of the particle-containing layer.

[0101] Furthermore, the particle-containing layer-forming composition may also contain a crosslinking agent. There are no particular restrictions on the crosslinking agent; known agents can be used. Examples of crosslinking agents include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds, with oxazoline compounds and carbodiimide compounds being preferred. Examples of commercially available products include Carbodilite V-02-L2 (manufactured by Nisshinbo Inc.) and Epocross K-2020E (manufactured by Nippon Shokubai Inc.). For details on epoxy compounds, isocyanate compounds, and melamine compounds, refer to sections

[0081] to

[0083] of Japanese Patent Application Publication No. 2015-163457. Crosslinking agents described in sections

[0082] to

[0084] of International Publication No. 2017 / 169844 can also be preferably used. For carbodiimide compounds, refer to sections

[0038] to

[0040] of Japanese Patent Application Publication No. 2017-087421. For oxazoline compounds, carbodiimide compounds, and isocyanate compounds, the crosslinking agents described in sections

[0074] to

[0075] of International Publication No. 2018 / 034294 can also be preferably used. The crosslinking agent content is preferably 0 to 50% by mass relative to the total mass of the particle-containing layer. In a particle-containing layer-forming composition, the preferred mass ratio of the crosslinking agent to the binder is 2 to 50% by mass.

[0102] The method for applying the particle-containing layer-forming composition is not particularly limited, and known methods can be used. Examples of application methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating.

[0103] The particle-containing layer formation step is preferably performed between the first stretching step and the second stretching step. The heating temperature for forming the particle-containing layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0104] Furthermore, in order to improve the adhesion between the polyester substrate and the particle-containing layer, pretreatment such as anchor coating, corona treatment, and plasma treatment may be applied to the surface of the polyester substrate before the particle-containing layer is provided.

[0105] Furthermore, the indentation modulus of the particle-containing layer can be adjusted by the type of binder, the type of crosslinking agent, the type of additive, and their mixing ratios when the particle-containing layer is formed using the above-mentioned particle-containing layer forming composition. The indentation modulus of the particle-containing layer can also be adjusted by the thickness of the particle-containing layer. Specific methods for achieving the indentation modulus of the particle-containing layer within the above range include using a binder with a low glass transition temperature, using a crosslinking agent with a low glass transition temperature (for example, using the oxazoline compound (such as Epocross K2020E (manufactured by Nippon Shokubai Co., Ltd.)) and the carbodiimide compound), reducing the crosslinking density (for example, reducing the amount of crosslinking agent used, reducing the number of reaction sites in the binder etc. that react with the crosslinking agent), adding a plasticizer (for example, adding a polyethylene oxide compound), and increasing the thickness of the particle-containing layer.

[0106] [Exfoliation layer formation process] The release layer formation process involves applying a release layer formation composition to the surface of the polyester substrate opposite to the particle-containing layer to form a release layer. The release layer formation process is performed between the extrusion molding process and the first stretching process, between the first stretching process and the second stretching process, or after the stretching process. When the peeling layer formation process is performed after the stretching process, it is preferable to perform it after the cooling process described later, and more preferable to perform it after the winding process and trimming process described later. The release layer formed on one surface of the polyester substrate by the release layer formation process is the same as the layer described in the section on release layers above.

[0107] First, we will describe the composition for forming the release layer. A composition for forming a release layer can be prepared by mixing a release agent, additives as needed, and a solvent. Examples of solvents include water, alcohol-based solvents, ether-based solvents, ketone-based solvents, and aromatic hydrocarbon-based solvents.

[0108] The release layer forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass, based on the total mass of the release layer forming composition. In other words, in the release layer forming composition, the total content of components other than the solvent (solids) is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass, based on the total mass of the release layer forming composition.

[0109] The release agent contained in the release layer forming composition, and any additives added as needed, are as described in the section on the release layer above, including their preferred embodiments. The release layer forming composition includes the above-mentioned resin and solvent, and may optionally include the above-mentioned additives and / or the above-mentioned catalyst used for curing the resin. Furthermore, the composition for forming the release layer preferably contains a crosslinking agent. The crosslinking agent is not particularly limited, and known agents can be used. Furthermore, the release layer-forming composition may also contain a polymerization initiator. Examples of polymerization initiators include photopolymerization initiators, and known ones can be used. With respect to each component other than the solvent in the release layer forming composition, it is preferable to adjust the content of each component in the release layer forming composition so that the content of each component relative to the total mass of solids in the release layer forming composition is the same as the preferred content of each component relative to the total mass of the release layer.

[0110] The method for applying the release layer-forming composition is not particularly limited, and known methods can be used. Specific examples of application methods are described in the particle-containing layer formation step.

[0111] The heating temperature for forming the release layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0112] Furthermore, in order to improve the adhesion between the polyester substrate and the release layer, pretreatment such as anchor coating, corona treatment, and plasma treatment may be applied to the surface of the polyester substrate before applying the release layer.

[0113] Furthermore, the indentation modulus of the release layer can be adjusted by the type of release agent, the type of additives, and their mixing ratios. Specific methods for achieving the indentation modulus of the release layer within the above range include the use of polyfunctional crosslinking agents (e.g., isocyanate compounds with three or more functions, epoxy compounds, and acrylic acrylate compounds, melamine compounds, alkoxysilane compounds, etc.), the use of resins and crosslinking agents with high glass transition temperatures (e.g., the use of low molecular weight crosslinking agents and crosslinking agents with high glass transition temperatures), and the addition of fillers (e.g., the addition of colloidal silica, etc.). Examples of low molecular weight crosslinking agents include isocyanate compounds, epoxy compounds, and melamine compounds, and examples of crosslinking agents with high glass transition temperatures include oxazoline compounds (e.g., Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.)).

[0114] [Heat setting process] The above method for manufacturing the release film may include a heat-setting step as a heat treatment for the polyester film obtained in the stretching step, after the stretching step. In the heat-setting process, the polyester film obtained in the stretching process can be heated and heat-set. By crystallizing the polyester resin through heat-setting, shrinkage of the polyester substrate can be suppressed. The surface temperature of the polyester film in the heat-setting process (heat-setting temperature) is not particularly limited, but is preferably less than 240°C, more preferably 235°C or less, and even more preferably 230°C or less. The lower limit is not particularly limited, but is preferably 190°C or higher, more preferably 200°C or higher, and even more preferably 210°C or higher. The heating time in the heat setting process is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

[0115] [Thermal relaxation process] The above method for manufacturing the release film may include a heat relaxation step after the heat setting step. In the thermal relaxation process, it is preferable to thermally relax the polyester film, which has been thermally fixed in the thermal fixing process, by heating it at a lower temperature than that of the thermal fixing process. Thermal relaxation can alleviate residual strain in the polyester film. In the heat relaxation process, the surface temperature of the polyester film (heat relaxation temperature) is preferably 5°C or more lower than the heat fixing temperature, more preferably 15°C or more lower, even more preferably 25°C or more lower, and particularly preferably 30°C or more lower. That is, the heat relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, even more preferably 210°C or lower, and particularly preferably 200°C or lower. The lower limit of the thermal relaxation temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

[0116] [Cooling process] The above method for manufacturing the release film may include a cooling step for cooling the heat-relaxed polyester film. In the above manufacturing method, the cooling rate of the polyester film in the cooling step is preferably more than 2000°C / min and less than 4000°C / min, more preferably 2000 to 3500°C / min, even more preferably more than 2200°C / min and less than 3000°C / min, and particularly preferably 2300 to 2800°C / min. To reduce thermal shrinkage and impart dimensional stability, the cooling rate of the polyester film in the cooling step is preferably more than 500°C / min and less than 4000°C / min, even more preferably 700 to 3000°C / min, and particularly preferably 1000 to 2500°C / min. By being within the above range, it becomes easier to suppress streak-like wrinkles that occur on the surface of the release layer of the release film, and it is possible to manufacture a ceramic green sheet with suppressed thickness unevenness. In the above cooling process, it is also preferable to include a step (expansion step) of expanding the heat-relaxed polyester film in the width direction. The expansion rate in the width direction of the polyester film due to the expansion process, that is, the ratio of the polyester film width at the end of the cooling process to the polyester film width before the start of the cooling process, is preferably 0% or more, more preferably 0.001% or more, and even more preferably 0.01% or more. There is no particular upper limit to the expansion rate, but it is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

[0117] In addition, the above-described method for manufacturing the release film involves applying a particle-containing layer formation composition in the particle-containing layer formation step to form a particle-containing layer. However, the particle-containing layer formation method is not limited to the above embodiment, and known methods can be used. For example, one method is to form an unstretched polyester substrate with a laminated particle-containing layer by co-extrusion molding.

[0118] [Winding process] The above manufacturing method may include a winding step to obtain a roll of polyester film by winding up the polyester film obtained through the above steps.

[0119] [Trimming process] The above manufacturing method may further include a trimming step, before carrying out the above winding step, in which the polyester film is continuously cut along the conveying direction to cut off at least one end of the polyester film in the width direction.

[0120] [Other conditions] The conveying speed of the polyester film in each step of this manufacturing method other than the longitudinal stretching step is not particularly limited, but in the transverse stretching step, heat setting step, heat relaxation step, and cooling step, 50 to 200 m / min is preferred, and 80 to 150 m / min is more preferred in terms of productivity and quality.

[0121] In the method for manufacturing the release film described in detail above, a combination of two or more preferred embodiments is a more preferred embodiment.

[0122] <Application> The release film of the present invention can suppress defects in the ceramic green sheet formed on the release film, and is therefore preferably used as a release film (carrier film) for manufacturing ceramic green sheets (preferably for manufacturing thin-layer ceramic green sheets). The ceramic green sheet manufactured using the above release film can be suitably used for ceramic capacitors and multilayer inductors, where multilayering of internal electrodes is required due to miniaturization and increased capacitance. The method for producing a ceramic green sheet using the above-mentioned release film is not particularly limited and can be carried out by known methods. For example, a method for producing a ceramic green sheet may involve applying a prepared ceramic slurry to the surface of the release layer of the release film and drying off the solvent contained in the ceramic slurry. The method for applying the ceramic slurry is not particularly limited. For example, known methods such as applying a ceramic slurry, which is prepared by dispersing ceramic powder and a binder agent in a solvent, using a reverse roll method and removing the solvent by heating and drying can be applied. The binder agent is not particularly limited, and an example is polyvinyl butyral. The solvent is also not particularly limited, and an example is ethanol and toluene.

[0123] Furthermore, the release film of the present invention can also be used as a protective film for dry film resists, a film for sheet molding such as decorative layers and resin sheets, a release film for process manufacturing such as semiconductor manufacturing processes, a release film for polarizing plate manufacturing processes, and a separator for adhesive films such as labels, medical and office supplies. [Examples]

[0124] The present invention will be described in more detail below based on examples. The materials, quantities, proportions, processing details, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0125] First, we will explain the method for preparing the release films used in each example and comparative example.

[0126] <Example 1> [Extrusion molding process] A titanium compound (titanium citrate chelate complex, VERTEC AC-420, manufactured by Johnson Matthey) described in Japanese Patent No. 5575671 was used as a polymerization catalyst to produce polyethylene terephthalate pellets. The obtained pellets were dried until the moisture content was 50 ppm or less, then placed into the hopper of a 30 mm diameter single-screw kneading extruder, and subsequently melted and extruded at 280°C. The molten material was passed through a filter (pore size 3 μm) and then extruded from the die into a cooling drum at 25°C to obtain an unstretched polyester substrate made of polyethylene terephthalate. The extruded molten material was then brought into close contact with the cooling drum by electrostatic application. The melting point (Tm) of polyethylene terephthalate, which constitutes the unstretched polyester substrate, was 258°C, and the glass transition temperature (Tg) was 80°C.

[0127] [Longitudinal stretching process] The above unstretched polyester substrate was subjected to a longitudinal stretching process using the following method. A uniaxially oriented polyester substrate was produced by passing a preheated, unstretched polyester substrate between two pairs of rolls with different peripheral speeds under the following conditions and stretching it in the longitudinal direction (conveying direction). (Longitudinal extension conditions) Preheating temperature: 75℃ Stretching temperature: 90℃ Stretching ratio: 3.4 times Stretching speed: 1300% / sec

[0128] [Particle-containing layer formation process] A particle-containing layer was formed by applying the following composition A1 (composition for forming a particle-containing layer) to one side of a longitudinally stretched uniaxially oriented polyester substrate using a bar coater, and then drying the formed coating film with hot air at 100°C. In other words, composition A1 was in-line coated onto the uniaxially oriented polyester substrate. At this time, the amount of composition A1 applied was adjusted so that the thickness of the particle-containing layer and the release layer formed in the transversely stretched state was 100 nm.

[0129] (Composition A1) Composition A1 was prepared by mixing the components listed below. The prepared composition A1 was subjected to filtration using a filter with a pore size of 6 μm (F20, manufactured by MAHLE FILES SYSTEMS, Inc.) and membrane degassing (2x6 radial flow superphobic, manufactured by POLIPORE, Inc.) to obtain composition A1. • Acrylic resin 1 (aqueous dispersion of a copolymer obtained by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2, solid content concentration 25% by mass, acid value 16 mg KOH / g) 167 parts by mass • Crosslinking agent 1 (carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Co., Ltd., diluted to 10% by mass) 16.8 parts by mass W-1: Nonionic surfactant (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd., solid content 100% by mass) 0.7 parts by mass W-2: Anionic hydrocarbon surfactant (Rapizol® A-90, sodium di-2-ethylhexyl sulfosuccinate, manufactured by NOF Corporation, 1% solids by mass diluted with water) 56 parts by mass • Particle 1 (Snowtex® MP-2040, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 200 nm, solid content concentration 40% by mass aqueous dispersion) 11 parts by mass ·Water 776 parts by mass

[0130] [Horizontal stretching process] A polyester substrate that had undergone a longitudinal stretching process and a particle-containing layer formation process was stretched in the width direction using a tenter under the following conditions to produce a biaxially oriented polyester substrate. (lateral stretching conditions) Preheating temperature: 100℃ Stretching temperature: 120℃ Stretching ratio: 4.2x Stretching speed: 50% / sec

[0131] [Heat setting process] The polyester film obtained by the above transverse stretching process was subjected to a heat setting process by heating it using a tenter under the following conditions to heat-set the polyester film. (Heat fixation conditions) Heat fixing temperature: 227℃ Thermal fixation time: 6 seconds

[0132] [Thermal relaxation process] Next, a thermal relaxation process was performed on the heat-fixed polyester film to relieve tension by heating it under the following conditions. In addition, during the thermal relaxation process, the film width was reduced compared to the end of the thermal fixing process by narrowing the distance between the gripping members of the tenter that grips both ends of the polyester film (tenter width). The thermal relaxation rate Lr shown below was calculated using the formula Lr = (L1 - L2) / L1 × 100, where Lr is the film width at the end of the thermal relaxation process and L1 is the film width at the start of the thermal relaxation process. (Thermal relaxation conditions) Thermal relaxation temperature: 190℃ Thermal relaxation rate Lr: 4%

[0133] [Cooling process] A cooling process was performed on the heat-relaxed polyester film under the following conditions. The cooling rate shown below was calculated by dividing the temperature difference ΔT (°C) between the film surface temperature measured when the film was loaded into the cooling section of the stretcher and the film surface temperature measured when it was removed from the cooling section by the cooling time ta, with the cooling time ta being the time the polyester film stayed in the cooling section from when it was loaded into the cooling section until it was removed from the cooling section. (Cooling conditions) Cooling rate: 2500℃ / min

[0134] [Winding process] After the polyester film was cooled in the cooling process, a trimming device was used to continuously cut the polyester film along the conveying direction at a position 20 cm from both ends in the width direction of the film, thereby trimming both ends of the film. Next, an extrusion process (knurling) was performed on the area from both ends of the polyester film up to 10 mm in the width direction, and then the polyester film was wound up with a tension of 40 kg / m. A biaxially oriented film was prepared using the method described above. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m, and a roll length of 7000 m.

[0135] [Exfoliation layer formation process] The obtained biaxially oriented film was unwound at a transport speed of 30 m / min, and composition B1 described below was applied to the side of the biaxially oriented film opposite to the particle-containing layer (the side without the particle-containing layer) using a bar coater and dried at 90°C to obtain a coated layer of composition B1. The amount of composition B1 applied was adjusted so that the thickness of the resulting release layer was 500 nm. Subsequently, 70 mJ / cm 2 The coating layer of composition B1 was cured by irradiation with ultraviolet light to form a release layer. The resulting biaxially oriented film with the release layer was wound up at a tension of 40 kg / m to obtain a release film. (Composition B1) Composition B1 was prepared by mixing the components listed below. The prepared composition B1 was subjected to filtration using a filter with a pore size of 6 μm (F20, manufactured by MAHLE FILES SYSTEMS, Inc.) and membrane degassing (2x6 radial flow superphobic, manufactured by POLIPORE, Inc.) to obtain composition B1. • Silicone resin (GL-04R, manufactured by Kyoeisha Chemical Co., Ltd., solid content concentration 20% by mass) 2 parts by mass • Polymerizable compound (dipentaerythritol polyacrylate, A-DPH, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., solids content 100% by mass) 38 parts by mass ·Photopolymerization initiator (Omnirad127, manufactured by IGM Resins BV, solid content 100% by mass) 1.6 parts by mass • Isopropyl alcohol 74 parts by mass • Methyl ethyl ketone 18 parts by mass

[0136] <Example 2> A release film was prepared in accordance with the method described in Example 1, except that in the particle-containing layer formation step, composition A2 was used instead of composition A1, and the amount of composition A2 applied was adjusted so that the thickness of the particle-containing layer was 50 nm. (Composition A2) Composition A2 was prepared in the same manner as composition A1, except that acrylic resin 1 in composition A1 was replaced with the following olefin resin. • Olefin resin (Zyxen NC, manufactured by Sumitomo Seika Co., Ltd.)

[0137] <Example 3> A release film was prepared according to the method described in Example 1, except that in the particle-containing layer formation step, composition A3 was used, which was obtained by changing the content of crosslinking agent 1 in composition A1 to 50.4 parts by mass, and the amount of composition A3 applied was adjusted so that the thickness of the particle-containing layer was 50 nm.

[0138] <Example 4> A release film was prepared according to the method described in Example 1, except that in the particle-containing layer formation process, composition A4 was used instead of composition A1, and the amount of composition A4 applied was adjusted so that the thickness of the particle-containing layer was 50 nm. (Composition A4) Composition A4 was prepared by mixing the components listed below, in the same manner as composition A1. • The above acrylic resin 1,167 parts by mass • 50.4 parts by mass of the above crosslinking agent • 0.7 parts by mass of the above nonionic surfactant (W-1) • 56 parts by mass of the above anionic hydrocarbon surfactant (W-2) • Particle 2 (Snowtex® XL, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 50 nm, solid content concentration 40% by mass aqueous dispersion) 2.2 parts by mass • Particle 3 (Snowtex® MP-4540M, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 450 nm, solid content concentration 40% by mass aqueous dispersion) 0.6 parts by mass ·Water 776 parts by mass

[0139] <Example 5> A release film was prepared according to the method described in Example 3, except that in the particle-containing layer formation step, composition A5 was used, which was obtained by changing the content of crosslinking agent 1 in composition A3 to 79.8 parts by mass.

[0140] <Example 6> A release film was prepared according to the method described in Example 1, except that in the release layer formation step, composition B2 was used instead of composition B1, the coating layer was dried at 90°C to obtain a coating layer, and then the formed coating film was heat-cured at 120°C for 1 minute to form a release layer. (Composition B2) Composition B2 was prepared in the same manner as composition B1 by mixing the components listed below. • Polyester-modified silicone resin (BYK-370, manufactured by Bic Chemie Japan Co., Ltd., solid content concentration 25% by mass) 4 parts by mass • Thermopolymerizable compound (hexamethoxymelamine, manufactured by Tokyo Chemical Industry Co., Ltd., solids content 100% by mass) 36 parts by mass • Acid catalyst (p-toluenesulfonic acid, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., solid content 100% by mass) 2 parts by mass • Isopropyl alcohol 74 parts by mass • Isobutyl alcohol 18 parts by mass

[0141] <Example 7> A release film was prepared according to the method described in Example 6, except that in the particle-containing layer formation process, composition A4 was used instead of composition A1, and the amount of composition A4 applied was adjusted so that the thickness of the particle-containing layer was 50 nm.

[0142] <Example 8> A release film was prepared according to the method described in Example 6, except that in the particle-containing layer formation step, composition A5 was used instead of composition A1, and the amount of composition A5 applied was adjusted so that the thickness of the particle-containing layer was 50 nm.

[0143] <Example 9> A release film was prepared according to the method described in Example 1, except that composition B3 was used instead of composition B1 in the release layer formation step. (Composition B3) Composition B3 was prepared by mixing the components listed below, in the same manner as composition B1. • Silicone resin (UV POLY215, manufactured by Arakawa Chemical Industries, Ltd., solids content 100% by mass) 3.2 parts by mass • Polymerizable compound (epoxy compound, celloxide 2021P, manufactured by Daicel Corporation, solids content 100% by mass) 28 parts by mass • Photopolymerization initiator (UV CATA211, manufactured by Arakawa Chemical Industries, Ltd., solids content 100% by mass) 8.3 parts by mass • Isopropyl alcohol 74 parts by mass • Isobutyl alcohol 18 parts by mass

[0144] <Example 10> A release film was prepared according to the method described in Example 9, except that composition A4 was used instead of composition A1 in the particle-containing layer formation step.

[0145] <Example 11> A release film was prepared according to the method described in Example 9, except that in the particle-containing layer formation step, composition A5 was used instead of composition A1, and the amount of composition A5 applied was adjusted so that the thickness of the particle-containing layer was 50 nm.

[0146] <Example 12> A release film was prepared according to the method described in Example 9, except that in the particle-containing layer formation process, composition A12 was used instead of composition A1, and the amount of composition A12 applied was adjusted so that the thickness of the particle-containing layer was 50 nm. (Composition A12) Composition A12 was prepared in the same manner as composition A4, except that crosslinking agent 1 in composition A4 was replaced with crosslinking agent 2 below, and the amount added was changed to 45.9 parts by mass. • Crosslinking agent 2 (Epocross® WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content concentration 39% by mass dilution)

[0147] <Example 13> A release film was prepared according to the method described in Example 12, except that in the particle-containing layer formation step, composition A13 was used in which the particles in composition A12 were replaced with particle 1.

[0148] <Example 14> A release film was prepared according to the method described in Example 13, except that composition A14 was used instead of composition A13 in the particle-containing layer formation process. (Composition A14) Composition A14 was prepared in the same manner as composition A13, except that particle 1 in composition A13 was replaced with particle 4 below. • Particle 4 (MP-1000, manufactured by Soken Chemical Co., Ltd., non-crosslinked acrylic resin particles, average particle diameter 400 nm)

[0149] <Examples 15-20> A release film was prepared in the same manner as in Example 1, except that the particle-containing layer forming composition was changed as shown in Table 1 during the particle-containing layer formation process. In the table, surfactants W-1 to W-5 are as described below. Composition A15 is the same as composition A12 except that the surfactant used is changed to surfactant W-2 only. Composition A16 is the same as composition A2 except that it does not use surfactant W-1. Composition A17 is the same as composition A16 except that the amount of surfactant W-2 used is doubled. Composition A18 is the same as composition A16 except that surfactant W-2 is replaced with surfactant W-3. Composition A19 is the same as composition A16 except that surfactant W-2 is replaced with surfactant W-4. Composition A20 was prepared by adding 5 parts by mass of surfactant W-5 (diluted in a 1% by mass aqueous solution) to composition A16.

[0150] <Comparative Example 1> A release film was prepared according to the method described in Example 12, except that composition AC1 was used instead of composition A1 in the particle-containing layer formation step. (Composition AC1) • Acrylic resin 2 (Acrylic resin 2: an aqueous dispersion obtained by neutralizing a copolymer of methyl methacrylate, 2-hydroxyethyl methacrylate, and methacrylic acid polymerized in a mass ratio of 28:48:24 with triethylamine, solid content concentration 20% by mass) 165.7 parts by mass • Crosslinking agent 2 (Epocross® WS-700, manufactured by Nippon Shokubai Co., Ltd., diluted to a solid content concentration of 25% by mass) 56.8 parts by mass • Fluorine-based surfactant (Surflon S-211, manufactured by AGC Seimi Chemical Co., Ltd., 1% solid content by mass, diluted with water) 56 parts by mass • The above particles 2: 2.2 parts by mass • 0.6 parts by mass of the above particles 3 ·Water 776 parts by mass

[0151] <Comparative Example 2> A release film was prepared according to the method described in Example 8, except that composition BC1 was used instead of composition B2 in the release layer formation step, and composition AC2 was used instead of composition A5 in the particle-containing layer formation step. (Composition BC1) Composition BC1 was prepared by mixing the components listed below, in the same manner as composition B1. • Silicone resin (CF-2152, manufactured by Toray Dow Corning Co., Ltd., solid content 100% by mass) 8 parts by mass Platinum catalyst (SRX-212, manufactured by Toray Dow Corning Co., Ltd., solid content 100% by mass) 0.16 parts by mass • Toluene 99 parts by mass • Methyl ethyl ketone 230 parts by mass (Composition AC2) • The above acrylic resin 1,167 parts by mass • 50.4 parts by mass of the above crosslinking agent • Fluorine-based surfactant (Surflon S-211, manufactured by AGC Seimi Chemical Co., Ltd., 1% solid content by mass, diluted with water) 56 parts by mass • 11 parts by mass of the above particles ·Water 776 parts by mass

[0152] <Rating> The evaluation methods for each example and comparative example will be described below.

[0153] [Defect Assessment] In each example and comparative example, the following ceramic slurry was applied to the surface of the release layer side of the release film using a die coater over a width of 250 mm and a length of 10 m. The amount applied was adjusted so that the film thickness after drying was 0.5 μm. Then, it was dried in a dryer at 90°C for 1 minute to obtain a release film with a ceramic green sheet. The release film with the ceramic green sheet prepared by the above method is cut to a length of 250 mm, and the layers are stacked so that the surface of the ceramic green sheet and the surface of the particle-containing layer are in contact, and the density is 1 kg / cm². 2 The load was applied for 10 minutes. After that, the release film was peeled off from the ceramic green sheet to obtain the ceramic green sheet. The surface of the obtained ceramic green sheet was illuminated with light from a three-wavelength fluorescent lamp, and the surface of all the obtained ceramic green sheets was visually inspected over a distance of 2m. 2 The inspection was conducted, and the number of defects was evaluated according to the following criteria. (Ceramic slurry) The ceramic slurry was obtained by mixing the components listed below, adding zirconia beads, dispersing them in a ball mill, and then removing the beads. • Barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03") 100 parts by mass • Polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name "Esrec B·K BM-2") 8 parts by mass • Dioctyl phthalate (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate) 4 parts by mass • Mixture of toluene and ethanol (mass ratio 6:4) 135 parts by mass (Evaluation Criteria) A: The ceramic green sheet was not defective. B: 1 to 5 defects were found in the ceramic green sheet. C: More than six defects were found in the ceramic green sheet.

[0154] [Evaluation of peelability] A release film with a ceramic green sheet was obtained in the same manner as for defect evaluation, except that the thickness of the ceramic green sheet (slurry coating film after drying) was adjusted to 3 μm. Polyester adhesive tape No. 31B (manufactured by Nitto Denko Corporation) was attached to the surface of the ceramic green sheet in the release film with the ceramic green sheet. After standing at room temperature for 24 hours in this state, the release film with the ceramic green sheet was cut to a width of 20 mm to prepare a sample. The adhesive tape side of the sample was fixed to a glass plate, and the release film was peeled from the ceramic green sheet using an A&D Tensilon universal tester under the conditions of a peel angle of 180° and a peel speed of 100 mm / min, and the force required to peel was measured. Peelability was evaluated according to the following criteria. (Evaluation Criteria) A: When peeling from the ceramic green sheet, it is possible to peel it off with a force of 45 mN or less. B: A force exceeding 45 mN is required to peel it off the ceramic green sheet.

[0155] [Applicability of the release layer] The release films obtained in each example and comparative example were cut to a length of 30 m in the longitudinal direction. The surface of the release layer side of the obtained samples was observed by reflected light under a three-wavelength fluorescent lamp, and the coatability of the release layer was evaluated according to the following criteria. (Evaluation Criteria) A: No defects caused by foreign objects were observed. B: Defects caused by foreign objects were observed.

[0156] [Measurement of the indentation modulus of the delamination layer] The release films obtained in each example and comparative example were cut to a size of 10 mm x 10 mm. Next, the side of the cut release film with the particle-containing layer and the glass plate were bonded and fixed with epoxy adhesive to obtain a test specimen. The indentation modulus of the surface of the test specimen (the surface on the release layer side of the release film) was measured using a microhardness evaluation device (Burker Nano Triboindenter TI-950). The detailed measurement conditions were as follows. Indenter: Triangular pyramidal diamond indenter (Berkovich indenter, interior angle of the indenter: 142.35°, angle between the center line and the face: 65.35°) Maximum indentation depth of the indenter: 50nm Measurement temperature: 23℃

[0157] [Measurement of the indentation modulus of the particle-containing layer] The release films obtained in each example and comparative example were cut to a size of 10 mm x 10 mm. Next, the release layer side of the cut release film and the glass plate were bonded and fixed with epoxy adhesive to obtain a test specimen. Measurements were taken in the region of the particle-containing layer of the test specimen, excluding the protrusions, using an AFM (Burker, DimensionIcon) in peak force tapping mode. Force curves were obtained, and the indentation modulus was determined. The specific procedure is described below. First, preliminary measurements were taken, and the cantilever and probe were calibrated. The cantilever's warp sensitivity was calculated by measuring the force curve of the quartz substrate and analyzing the slope of the curve. The cantilever's warp sensitivity was 75.57 nm / V. The spring constant was calculated by measuring the thermal fluctuations of the probe. Specifically, it was calculated using the Thermal Tune method included in the software for Bruker AFM. The spring constant was 12.88 N / m. The tip curvature of the probe was measured by measuring the shape of the tip curvature calibration sample (RM-12M: Ti Roughness Sample) and calculated using the image analysis mode (Tip Qualification) attached to the software of the AFM manufactured by Bruker. The tip curvature of the probe was 10.4 nm. Next, with a scanning area of 3 μm × 3 μm and a maximum indentation load of 25 nN, the surface shape of the specimen was obtained. Referring to the obtained surface shape, for one point in the region other than the convex part (resin layer region), with a maximum indentation load of 180 nN, a force curve was obtained. The elastic modulus was determined using Hertz contact theory from the slope of the return force curve (in the region of 20% to 90% of the maximum load). The elastic modulus in the resin layer region was measured until five points were obtained within the same scanning area. Thereafter, the scanning area was changed and the elastic modulus was obtained in the same procedure. For one specimen, measurements were performed at five scanning areas, and the arithmetic mean of the values obtained from 25 measurements of the elastic modulus was taken as the indentation elastic modulus of the particle-containing layer. Details of the measurement conditions are shown below. Cantilever: RTESPA-300 manufactured by Bruker (Manufacturer catalog value: Material: Si, spring constant K: 40 (N / m), resonance frequency f: 300 (kHz), tip curvature R: 8 (nm)) Measurement atmosphere: 23°C, in air Resolution: 256 × 256 Scan Rate: 1.5 Hz

[0158] <Results> The evaluation results are described in Table 1 below. In Table 1, the definitions of "maximum protrusion height Sp" and "surface mean roughness Sa" are as described above, and the measurement method is also as described above, and it was measured using an optical interferometer ("Vertscan 3300G Lite" manufactured by Hitachi High-Tech Corporation). In Table 1, the "surface free energy" is as described above, and the measurement method is also as described above. From the results of dropping droplets of purified water, methylene iodide, and ethylene glycol on the peeling surface at 25°C using a contact angle meter ("DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.). In Table 1, the measurement method for "thickness" is as described above. The cross-section of the release film was obtained using a microtome, then etched with Ar ions, and Pt was deposited. The thickness was then observed and measured using an SEM (S-4800, Hitachi High-Tech). In Table 1, the "Crosslinking Agent / Resin" column represents the weight (mass %) of the crosslinking agent relative to the solid content of the resin excluding the solvent. In Table 1, the definition of "extraction charge" is as described above, and the measurement method is also as described above. The measurement was performed on polyester film (polyester substrate with particle-containing layer) before the release layer was applied.

[0159] In Table 1, the materials listed in the "Resin," "Surfactant," "Additive," and "Particle" columns indicate the use of the following components, respectively. (resin) A copolymer or aqueous dispersion obtained by polymerizing acrylic resin 1, methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2. A copolymer obtained by polymerizing acrylic resin 2, methyl methacrylate, 2-hydroxyethyl methacrylate, and methacrylic acid in a mass ratio of 28:48:24, is neutralized with triethylamine and then dispersed in aqueous solution. Olefin resin: Zyxene NC (manufactured by Sumitomo Seika Co., Ltd., acid-modified polyolefin, aqueous dispersion) (Additives) Crosslinking agent 1: Carbodiimide compound, Carbodilite V-02-L2, manufactured by Nisshinbo Chemical Co., Ltd. Crosslinking agent 2: Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., Tg 50℃ (particle) Particle 1: Snowtex (registered trademark) MP-2040, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 200 nm Particle 2: Snowtex® XL, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 50 nm Particle 3: Snowtex (registered trademark) MP-4540M, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 450 nm Particle 4: MP-1000, manufactured by Soken Chemical Co., Ltd., non-crosslinked acrylic resin particles, average particle size 400 nm (Surfactants) W-1: Nonionic hydrocarbon surfactant (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd.) W-2: Anionic hydrocarbon surfactant (Rapizol A-90, manufactured by NOF Corporation) W-3: Fluorine-based surfactant (Surflon S-211, manufactured by AGC Seimi Chemical Co., Ltd., structure containing a linear perfluoroalkyl group with 6 or more carbon atoms) W-4: Silicone-based surfactant (BYK-346, manufactured by BYK) W-5: Fluorine-based surfactant (Futergent 215M, manufactured by Neos Co., Ltd., contains a perfluoroisopropyl group and does not contain a linear perfluoroalkyl group with 6 or more carbon atoms)

[0160] [Table 1]

[0161] [Table 2]

[0162] The results in Table 1 confirm that the release film of the present invention can suppress defects in ceramic green sheets during manufacturing and exhibits excellent release properties for ceramic green sheets. A comparison of Example 12 with Examples 1-11 and 13 confirmed that defects in the ceramic green sheet are further suppressed when the particle-containing layer contains inorganic particles and the maximum protrusion height on the surface of the particle-containing layer is 300 nm or less. A comparison of Example 12 and Example 14 confirmed that defects in the ceramic green sheet are more suppressed when the particle-containing layer contains organic particles. From a comparison of Examples 18 and 19 with other examples, it was confirmed that when the particle-containing layer contains at least one surfactant selected from the group consisting of hydrocarbon surfactants and fluorine-based surfactants having a perfluoroalkyl group with 1 to 4 carbon atoms, the coating properties of the release layer are improved.

[0163] Furthermore, a release film was obtained in the same manner as in Example 1, except that the cooling rate in the cooling process was set to 1500°C / min, and the same evaluation as in Example 1 was performed, resulting in the same evaluation results as in Example 1. [Explanation of Symbols]

[0164] 1: Release film 2: Exfoliation layer 4: Polyester base material 6: Particle-containing layer

Claims

1. A release film for manufacturing ceramic green sheets, comprising a release layer, a polyester substrate substantially free of particles, and a particle-containing layer in this order, On the surface of the release layer opposite to the polyester substrate, the indentation modulus measured by nanoindentation is 3.0 to 6.0 GPa. The surface of the particle-containing layer opposite to the polyester substrate has a convex portion. A release film in which the indentation modulus measured by an atomic force microscope is 0.1 to 8.0 GPa in the region other than the protrusions on the surface of the particle-containing layer opposite to the polyester substrate.

2. The release film according to claim 1, wherein the particle-containing layer contains inorganic particles, and the maximum protrusion height on the surface of the particle-containing layer opposite to the polyester substrate is 300 nm or less.

3. The release film according to claim 1, wherein the particle-containing layer contains organic particles.

4. The surface free energy of the surface of the release layer opposite to the polyester substrate is 10 to 35 mJ / cm². ２ The release film according to claim 1 or 2.

5. The release film according to claim 1 or 2, wherein the release layer contains a silicone resin.

6. The release film according to claim 1 or 2, wherein the thickness of the release film is 40 μm or less.

7. The release film according to claim 1 or 2, wherein the thickness of the particle-containing layer is 1 to 500 nm.

8. The release film according to claim 1 or 2, wherein the particle-containing layer contains at least one surfactant selected from the group consisting of hydrocarbon surfactants and fluorine-based surfactants having a perfluoroalkyl group having 1 to 4 carbon atoms.

Images