Release film, method for producing release film, and ceramic capacitor

Abstract

The present invention addresses the need for a release film that exhibits excellent peelability of ceramic green sheets and superior performance in suppressing the defect rate of ceramic capacitors during high-speed transport, a method for manufacturing the release film, and a ceramic capacitor. The release film of the present invention sequentially comprises a release layer, a polyester substrate, and a particle-containing layer, wherein the particle-containing layer comprises particles and a non-polyester resin, the particles comprising organic particles, and the release layer comprising a polysiloxane compound.

Description

[Technical Field]

[0001] This invention relates to a release film, a method for manufacturing the release film, and a ceramic capacitor. [Previous Technology]

[0002] With the increasing performance and miniaturization of electronic devices, the electronic components used in these devices also require higher performance and smaller size. For example, the number of mounting points on a substrate is increasing in multilayer ceramic capacitors, creating a strong demand for miniaturization. The manufacturing of ceramic capacitors generally involves coating a ceramic slurry onto a release film with a release layer and then drying it to form a ceramic green sheet. Furthermore, to prevent the surface of the release film from adhering (bonding) to the back surface when the release film is wound up, unevenness is typically created on the surface of the side of the release film opposite to the release layer by incorporating particles or similar methods.

[0003] Regarding the release film used in the above-mentioned ceramic green sheet manufacturing, it is known to improve the release stability by setting the surface of the release layer to a specific Si element ratio. For example, Patent Document 1 discloses a release film having a surface layer A on which a polyester film is used as a substrate, and the substrate is substantially free of particles on at least one side. A release layer is deposited on the surface of the surface layer A on at least one side, wherein the release layer is formed by hardening a composition containing an adhesive component and a silicone-based release agent, and the surface of the release layer has a specific Si element ratio, maximum protrusion height (P), and regional average roughness (Sa).

[0004] [Patent Document 1] International Publication No. 2020 / 050081

[0005] On the other hand, with the rapid miniaturization of ceramic capacitors in recent years, there is a demand for further thinning of ceramic green sheets. Furthermore, it is believed that the more advanced the thin film of the ceramic green sheet, the greater the impact of the surface shape of the release film on the performance of the ceramic green sheet. For example, if there is an uneven shape on the release surface of the release film, this uneven shape will be transferred to the ceramic green sheet, causing changes in the thickness of the ceramic green sheet, which may reduce the performance of the ceramic capacitor product.

[0006] The inventors manufactured ceramic green sheets using the release film for manufacturing ceramic green sheets described in Patent Document 1, and used the obtained ceramic green sheets to manufacture ceramic capacitors. They found that the ceramic green sheets exhibited excellent release properties. However, during the high-speed transport of the release film in the manufacturing or transport process of the release film, such as the release layer coating process, defects sometimes occurred, resulting in reduced electrical characteristics of the obtained ceramic capacitors. There is room for further improvement. Furthermore, when the aforementioned release film is stored for a long period and then used in the manufacture of ceramic green sheets, unevenness defects sometimes occurred on the obtained ceramic green sheets. There is room for further improvement. Additionally, excellent release properties are required for the manufactured ceramic green sheets. [Summary of the Invention]

[0007] In view of the above-mentioned circumstances, the object of the present invention is to provide a release film that, even when manufacturing ceramic green sheets using a release film with excellent release properties and high-speed transport, can suppress the defect rate of ceramic capacitors manufactured using the obtained ceramic green sheets, and can suppress the occurrence of unevenness defects in the obtained ceramic green sheets even when using a release film that has been stored for a long time to manufacture ceramic green sheets. Furthermore, the object of the present invention is to provide a method for manufacturing a release film and a ceramic capacitor.

[0008] As a result of in-depth research conducted by the inventors in order to solve the above-mentioned problems, they discovered that the above-mentioned problems can be solved by the following structure.

[0009] (1) A release film comprising, in sequence, a release layer, a polyester substrate and a particle-containing layer, wherein the particle-containing layer comprises particles and a non-polyester resin, the particles comprising organic particles, and the release layer comprising a polysiloxane compound. (2) The release film of (1) is used to manufacture ceramic green sheets. (3) The release film of (1) or (2) wherein the polyester substrate substantially does not contain particles. (4) The release film of any one of (1) to (3) wherein the surface of the particle-containing layer opposite to the polyester substrate has protrusions, wherein the proportion of protrusions formed by organic particles is 50 to 100%. (5) The release film of any one of (1) to (4) wherein the surface of the particle-containing layer opposite to the polyester substrate has protrusions, wherein the protrusion that becomes the maximum protrusion height Sp is a protrusion formed by organic particles. (6) A release film as described in any one of (1) to (5), wherein the surface free energy of the surface of the release layer opposite to the polyester substrate is 10 to 30 mJ / m², and the maximum protrusion height Sp is 1 to 30 nm. (7) A release film as described in any one of (1) to (6), wherein the organic particles comprise at least one selected from the group consisting of styrene resin, polyurethane resin, acrylic resin and divinylbenzene resin. (8) A release film as described in any one of (1) to (7), wherein the surface free energy of the surface of the particle-containing layer opposite to the polyester substrate is 25 to 45 mJ / m², and the maximum protrusion height Sp is 25 to 1000 nm. (9) A release film as described in any one of (1) to (8), wherein the non-polyester resin is at least one selected from the group consisting of acrylic resin, polyurethane resin and olefin resin. (10) A release film as described in any one of (1) to (9), wherein the thickness of the release film is 40 μm or less. (11) A release film as described in any one of (1) to (10), wherein the thickness of the particle-containing layer is 1 to 500 nm. (12) A method for manufacturing a release film, comprising: coating a particle-containing layer forming composition comprising organic particles and a non-polyester resin onto a surface of a polyester substrate. (13) A ceramic capacitor manufactured using a release film as described in any one of (1) to (11). [Effects of the Invention]

[0010] According to the present invention, a release film can be provided that, even when manufacturing ceramic green sheets using a release film with excellent release properties and high-speed transport, can suppress the defect rate of ceramic capacitors manufactured using the obtained ceramic green sheets, and can suppress the occurrence of unevenness defects in the obtained ceramic green sheets even when manufacturing ceramic green sheets using a release film that has been stored for a long time. Furthermore, according to the present invention, a method for manufacturing a release film and a ceramic capacitor can be provided.

Implementation Method

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

[0013] In this specification, the numerical range indicated by "~" refers to the range including the values ​​recorded before and after "~" as the lower and upper limits. Within the numerical range recorded in this specification, the upper or lower limit of a certain numerical range can be replaced by the upper or lower limit of another numerical range recorded in a different stage. Furthermore, within the numerical range recorded in this specification, the upper or lower limit of a certain numerical range can also be replaced by the values ​​shown in the embodiments. In this specification, when a plurality of substances conforming to each component are present in the composition, unless otherwise specified, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition. In this specification, the term "process" not only includes independent processes, but also includes processes that cannot be clearly distinguished from other processes, as long as the desired purpose of the process is achieved. In this specification, a combination of two or more preferred states constitutes a more preferred state.

[0014] In this specification, "long side direction" refers to the direction of the strip of the release film during manufacturing, and has the same meaning as "conveyance direction" and "mechanical direction". In this specification, "width direction" refers to a direction orthogonal to the long side direction. In this specification, "orthogonal" is not limited to strict orthogonality, but includes approximately orthogonality. "Approximately orthogonal" means intersecting within a range of 90°±5°, preferably within a range of 90°±3°, and even more preferably within a range of 90°±1°. Furthermore, in this specification, "film width" refers to the distance between the two ends of the width direction of the release film.

[0015] [Release Film] The release film of the present invention (hereinafter also simply referred to as "release film") sequentially comprises a release layer, a polyester substrate and a particle-containing layer, wherein the particle-containing layer comprises particles and a non-polyester resin, the particles comprising organic particles, and the release layer comprising a polysiloxane compound.

[0016] Hereinafter, the structure of the release film will be described with reference to the figures. Figure 1 is a cross-sectional view showing an example of the structure of the release film. The release film 1 sequentially comprises a release layer 2, a polyester substrate 4, and a particle-containing layer 6. In the release film 1 shown in Figure 1, there are two main surfaces formed by the surface 21 (hereinafter also referred to as the "release surface") of the release layer 2 opposite to the polyester substrate 4 and the surface 61 (hereinafter also referred to as the "conveying surface") of the particle-containing layer 6 opposite to the polyester substrate 4. In addition, the release film of the present invention is not limited to the form shown in Figure 1. For example, the release film 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.

[0017] As a characteristic feature of the release film of the present invention, the following points can be cited: the particle-containing layer contains particles and a non-polyester resin, the particles contain organic particles, and the release layer contains a polysiloxane compound. While the release film, by having the above-mentioned characteristics, exhibits excellent performance in suppressing the defect rate of ceramic capacitors manufactured using the obtained ceramic green sheets, even when using a release film with excellent release properties and high-speed transport to manufacture ceramic green sheets, and also exhibits excellent performance in suppressing the occurrence of unevenness defects in the obtained ceramic green sheets, even when using a release film that has been stored for a long time to manufacture ceramic green sheets, the detailed mechanism of which is not yet determined, but the inventors speculate as follows.

[0018] When the release layer contains polysiloxane, it is believed that the surface free energy of the release film is reduced, thus the release properties of the ceramic green sheet are excellent. However, if the release film is transported under high-speed transport conditions, particles that form protrusions on the transport surface may detach and adhere to the transport rollers due to friction caused by contact with the transport rollers. Since the release layer contains polysiloxane, the release surface is easily charged, causing particles adhering to the transport rollers to adhere to the release film. Furthermore, when the release film is stored in roller form during high-speed transport, particles adhering to the transport surface also adhere to the release surface facing the transport surface. Thus, if a release film with particles adhering to its release surface is used to manufacture the ceramic green sheet, a ceramic green sheet is formed that contacts the release surface with adhering particles, causing particles to transfer to the surface of the ceramic green sheet. When such a ceramic green sheet is used to manufacture a ceramic capacitor, tiny depressions or protrusions are formed in the ceramic layers due to particles being trapped between the ceramic layers. It is speculated that these tiny depressions or protrusions formed between the ceramic layers in this way are the main cause of the reduced capacitor characteristics. To address this problem, the release film of the present invention is characterized by containing organic particles on its transport surface. This ensures that even if the particles detach and become trapped between the ceramic green sheet layers during the aforementioned process, the organic particles burn during the calcination process. Therefore, no tiny depressions or protrusions are formed between the ceramic layers. Consequently, the degradation of the electrical characteristics of the multilayer ceramic capacitor can be suppressed, and the rate of defective products (defect rate) in the manufactured multilayer ceramic capacitors whose electrical characteristics do not meet practical standards can be reduced.

[0019] Furthermore, the polyester substrate of the release film contains impurities such as oligomers. When the release film is stored for an extended period, precipitates caused by these impurities may sometimes appear on the conveying surface and / or the release surface of the release film. These oligomers are low-molecular-weight byproducts generated during the polymerization of the polyester resin and are components contained as impurities in the polyester substrate. As described above, it is presumed that the precipitates appearing on the release surface, or the particles of the precipitates appearing on the conveying surface, may be transferred to the release surface during the release film's conveying or roller storage via the same mechanism as described above, thereby causing minute unevenness defects in the ceramic green sheet formed on the release surface. To address this problem, in the release film of the present invention, the particle-containing layer constituting the conveying surface comprises a non-polyester resin, and the release layer constituting the release surface comprises a polysiloxane compound. Therefore, it is believed that the precipitation of impurities such as oligomers from the polyester substrate to the conveying surface and / or the release surface of the release film can be suppressed, and the generation of unevenness defects in the ceramic green sheet formed on the release surface can be suppressed. Hereinafter, in this specification, the following performance is sometimes simply described as “the invention is excellent”: even when using a high-speed conveying release film to manufacture ceramic green sheets, it is excellent at suppressing the defect rate of ceramic capacitors manufactured using the obtained ceramic green sheets and / or even when using a release film that has been stored for a long time to manufacture ceramic green sheets, it is excellent at suppressing the occurrence of unevenness defects in the obtained ceramic green sheets.

[0020] Hereinafter, the layers of the release film will be described. In addition, the manufacturing method of the release film and the manufacturing method of each layer will be described later.

[0021] <Release Layer> The release layer is the layer on the side opposite to the side of the polyester substrate where the particle-containing layer is disposed. The ceramic green sheet is formed on the surface of the release layer opposite to the polyester substrate, i.e., the release surface. That is, the ceramic green sheet is manufactured so that it can be peeled off from the release surface of the release film. In addition, the release layer can be disposed directly on the surface of the polyester substrate, or it can be disposed on the polyester substrate in between other layers, but from the viewpoint of better smoothness, it is better to be disposed directly on the surface of the polyester substrate. As a method for forming a release layer with a crosslinked structure, as described later, a method of forming a release layer using a release layer forming composition containing a crosslinking agent can be cited.

[0022] [Polysiloxane Compound] From the viewpoint of excellent peelability, the release layer contains a polysiloxane compound. There are no particular limitations on the polysiloxane compound contained in the release layer, as long as it is a compound with siloxane bonds in its molecule; polysiloxane resin is preferred, and polysiloxane resin with a cross-linked structure is even more preferred. Polysiloxane resin refers to a resin that has a polysiloxane structure (a main chain composed of siloxane bonds) in its molecule. Examples of polysiloxane resins include curing polysiloxane resins, polysiloxane grafted resins, and alkyl-modified polysiloxane resins, with reactive curing polysiloxane resins being preferred. Examples of reactive curing polysiloxane resins include addition-reaction polysiloxane resins, condensation-reaction polysiloxane resins, and ultraviolet or electron beam curing polysiloxane resins. Among them, addition-reaction polysiloxane resins with low-temperature curing properties, or ultraviolet or electron beam curing polysiloxane resins, are preferred because they can form a release layer at low temperatures.

[0023] Examples of addition-reaction polysiloxanes include resins obtained by reacting and curing polydimethylsiloxanes with vinyl groups introduced at the ends or side chains using a platinum catalyst. Examples of condensation-reaction polysiloxanes include resins having a three-dimensional cross-linked structure formed by condensing polydimethylsiloxanes with OH groups at the ends and polydimethylsiloxanes with H groups at the ends using an organotin catalyst. Examples of UV- or electron-beam curable polysiloxanes include resins that utilize the same free radical reaction as polysiloxane cross-linking in polysiloxanes, resins that introduce unsaturated groups for photocuring, resins that cross-link by decomposing onium salts with UV or electron beams to generate strong acids and cleaving epoxy groups, and resins that cross-link by the addition reaction of thiols and vinyl siloxanes. More specifically, examples include acrylate-modified polydimethylsiloxane and epoxy-propylene-modified polydimethylsiloxane.

[0024] The polysiloxane resin contained in the release layer may be a single type or two or more types. The content of polysiloxane resin in the release layer relative to the total mass of the release layer is preferably 0.1% to 99.9% by mass, and more preferably 0.5% to 99.5% by mass.

[0025] [Resins other than polysiloxanes] The release layer may contain resins other than the aforementioned polysiloxanes (hereinafter also referred to as "other resins"). There are no particular limitations on the other resins contained in the release layer, but from the viewpoint of further improving release properties, it is preferable to further contain fluoropolymers, alkyd resins, acrylic resins, various paraffins, and aliphatic olefins. Furthermore, unsaturated polyester resins, melamine resins, epoxy resins, phenolic resins, and polyurethane resins may be used in combination.

[0026] The other resins included in the release layer may be used alone or in combination with two or more. When the release layer includes other resins, the content of the aforementioned other resins in the release layer is preferably 50-99% by mass relative to the total mass of the release layer, and more preferably 60-98% by mass. The remainder in the release layer, excluding polysiloxane and other resins, may be at least one of the additives described later, and residues such as solvents, polymerization initiators, and catalysts included in the release layer forming composition (described later) used in the formation of the release layer.

[0027] [Additives] In addition to the resin mentioned above, the release layer may also contain additives. As additives, light release additives and heavy release additives for adjusting the release force, adhesion improvers, and antistatic agents may also be added.

[0028] [Characteristics of the release layer] (Thickness) The thickness of the release layer can be set according to its intended use and is not particularly limited. From the viewpoint of excellent balance between release performance and smoothness of the release surface, 5–2000 nm is preferred, 10–1000 nm is better, 30–300 nm is further preferred, and 50–200 nm is particularly preferred. The thickness of the release layer is defined as the arithmetic mean of the thickness at five points on a section having a cross-section perpendicular to the main surface of the release film, measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0029] (Surface Free Energy of the Release Surface) From the viewpoint of superior release properties of ceramic green sheets, it is preferable that the surface free energy of the surface of the release layer opposite to the polyester substrate side (release surface) is 30 mJ / m² or less, more preferably 10–30 mJ / m², further preferably 10–24 mJ / m², and especially preferably 10–20 mJ / m². The surface free energy of the release surface can be adjusted by the type of resin and additives used to form the release layer. In particular, since the release layer of the release film of the present invention contains a polysiloxane compound, it has a low surface free energy and excellent release properties of ceramic green sheets.

[0030] Furthermore, the surface free energy of the peeled surface can be determined by using a contact angle meter (e.g., the "DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.), at 25°C, by adding droplets of purified water, diiodomethane, and ethylene glycol to the peeled surface, measuring the contact angle after the droplets adhere to the surface for 1 second, and calculating from the obtained contact angles using the method of Kitazaki and Hata. Additionally, the "surface free energy" obtained by the above method is the sum of the polar component and the hydrogen bond component of the surface free energy.

[0031] (Maximum protrusion height Sp and average surface roughness Sa of the release surface) From the viewpoint of making the functional layer such as ceramic green sheets formed on the release layer smooth, the release surface is preferably as smooth as possible. Specifically, the maximum protrusion height Sp of the release surface is preferably 1 to 60 nm, more preferably 1 to 40 nm, and further preferably 1 to 30 nm. Furthermore, the average surface roughness Sa of the release surface is preferably 0 to 10 nm, more preferably 0 to 5 nm, further preferably 0 to 2 nm, and especially preferably 0 to 1 nm. The maximum protrusion height Sp and the average surface roughness Sa of the release surface can be adjusted, for example, by not adding particles to the release layer when setting it, and by selecting the resin and additives that form the release layer. In particular, by setting a release layer containing polysiloxane on a polyester substrate that substantially does not contain particles, the smoothness can be improved and Sp and Sa can be reduced.

[0032] Furthermore, the maximum protrusion height Sp and the average surface roughness Sa of the peeled surface can be determined by measuring the peeled surface using an optical interferometer (Hitachi High-Technologies Corporation's "Vertscan R3300G Lite") under the following conditions, and then analyzing the results using the built-in data analysis software. In the measurement of the maximum protrusion height Sp, the measurement position is changed and the measurement is performed 5 times. The maximum value obtained is taken as the measured value of the maximum protrusion height Sp (marked as P in the built-in data analysis software). Similarly, in the measurement of the average surface roughness Sa, the measurement position is changed and the measurement is performed 5 times. The average value obtained is taken as the measured value of the average surface roughness Sa. The specific measurement conditions are as follows: Measurement mode: WAVE mode; Objective lens: 50x; Measurement area: 186μm × 155μm

[0033] <Polyester Substrate> The polyester substrate is a film-like object containing polyester resin as the main polymer component. Here, "main polymer component" refers to the polymer with the highest content (by mass) among all polymers contained in the film-like object. The polyester substrate may contain only one type of polyester resin, or it may contain two or more types of polyester resin.

[0034] [Polyester Resin] Polyester resin is a polymer having ester bonds in its main chain. Polyester resin is usually formed by polycondensation of a dicarboxylic acid compound (described later) and a diol compound. There are no particular limitations on the polyester resin, and known polyester resins can be used. Examples of polyester resins include, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), and copolymers thereof, wherein at least one selected from the group consisting of PET, PEN, and copolymers thereof is preferred, with PET being more preferred.

[0035] The intrinsic viscosity of the polyester resin is preferably 0.50 dl / g or higher and less than 0.80 dl / g, and more preferably 0.55 dl / g or higher and less than 0.70 dl / g. The melting point (Tm) of the polyester resin is preferably 220–270 °C, and more preferably 245–265 °C. The glass transition temperature (Tg) of the polyester resin is preferably 65–90 °C, and more preferably 70–85 °C.

[0036] There are no particular limitations on the manufacturing method of polyester resin, and known methods can be used. For example, polyester resin can be manufactured by polycondensation of at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst. The materials used in the manufacture of polyester and the manufacturing conditions are described below.

[0037] (Dicarboxylic acid compound) Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl esters and ethyl esters. Among these, aromatic dicarboxylic acids or aromatic dicarboxylic acid methyl esters are preferred.

[0038] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, sebacic acid, dodecanoic acid, dimer acid, eicosanoic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of alicyclic dicarboxylic acid compounds include adamantane dicarboxylic acid, norcamphene dicarboxylic acid, cyclohexane dicarboxylic acid, and decahydronaphthalene dicarboxylic acid.

[0039] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, sodium 5-sulfoisophthalate, phenylindandicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)perylic acid, as well as methyl esters of the like. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, with terephthalic acid being more preferred.

[0040] A dicarboxylic acid compound may be used alone or in combination with two or more. When using terephthalic acid as a dicarboxylic acid compound, terephthalic acid may be used alone or copolymerized with other aromatic or aliphatic dicarboxylic acids such as isophthalic acid.

[0041] (Diol compound) Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0042] 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 cyclohexanediol, spirodiol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)benzene. Only one diol compound may be used, or two or more may be used in combination.

[0043] (Catalyst) There are no particular restrictions on the catalyst used in the manufacture of polyester resin, and any known catalyst that can be used in 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 catalyst activity and cost. Only one catalyst may be used, or two or more catalysts may be used in combination. It is preferred 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 with a phosphorus compound, and it is even more preferred to use a titanium compound with a phosphorus compound.

[0044] As a titanium compound, an organic chelate titanium complex is preferred. An organic chelate titanium complex is a titanium compound having an organic acid as a ligand. Examples of organic acids include citric acid, lactic acid, 1,2,4-benzenetricarboxylic acid, and malic acid. As a titanium compound, the titanium compounds described in

[0049] to

[0053] of Japanese Patent No. 5575671 may also be used, the contents of which are incorporated herein by reference.

[0045] (End-capping agent) An end-capping agent may be used as needed during the manufacture of polyester resin. By using an end-capping agent, a structure derived from the end-capping agent is introduced into the end of the polyester resin. There are no restrictions on the end-capping agent, and known end-capping agents can be used. Examples of end-capping agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds. As for end-capping agents, the contents described in Japanese Patent Application Publication No. 2014-189002

[0055] to

[0064] can also be referred to, the contents of which are incorporated herein by reference.

[0046] (Manufacturing Conditions) There are no restrictions on the reaction temperature during the manufacture of polyester resin; it can be set appropriately based on the raw materials. A reaction temperature of 260–300°C is preferred, and 275–285°C is even more preferred. There are no restrictions on the pressure during the manufacture of polyester resin; it can be set appropriately based on the raw materials. A pressure of 1.33 × 10⁻³ to 1.33 × 10⁻⁵ MPa is preferred, and 6.67 × 10⁻⁴ to 6.67 × 10⁻⁵ MPa is even more preferred.

[0047] As a method for synthesizing polyester resin, the methods described in

[0033] to

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

[0048] [Content of each component] The content of polyester resin in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and especially preferably 98% by mass or more, relative to the total mass of the polymer in the polyester substrate. There is no particular upper limit to the content of polyester resin; it can be appropriately set, for example, within a range of 100% by mass or less, relative to the total mass of the polymer in the polyester substrate. When the polyester substrate contains polyethylene terephthalate (PET), the content of PET is preferably 90-100% by mass, more preferably 95-100% by mass, further preferably 98-100% by mass, and especially preferably 100% by mass, relative to the total mass of the polyester resin in the polyester substrate.

[0049] The polyester substrate may also contain components other than polyester resin (e.g., 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 does not substantially contain particles. Examples of particles include those contained in the particle-containing layer described later. "Substantially does not contain particles" means that, for the polyester substrate, when the elemental composition from the particles is quantitatively analyzed by fluorescence X-ray analysis, the particle content relative to the total mass of the polyester substrate is less than 50 ppm by mass, preferably less than 10 ppm by mass, and more preferably less than the detection limit. This is because, even without actively adding particles to the polyester substrate, contaminants from foreign matter, raw material resins, or dirt adhering to the production line or equipment during the manufacturing process of the polyester substrate may sometimes peel off and mix into the polyester substrate.

[0050] [Properties of the Polyester Substrate] (Orientation) It is preferable that the polyester substrate is a biaxially oriented polyester substrate. "Biaxial orientation" refers to the property of molecular orientation in a biaxial direction. Molecular orientation is measured using a microwave transmission molecular orientation meter (e.g., MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The angle formed by the biaxial directions is preferably in the range of 90°±5°, more preferably in the range of 90°±3°, and further preferably in the range of 90°±1°. The biaxially oriented polyester substrate in the release film of the present invention preferably has molecular orientation in both the length and width directions. The biaxially oriented polyester substrate can be manufactured by the method described later.

[0051] (Density) The density of the polyester substrate is preferably 1.39 to 1.41 g / cm³, more preferably 1.395 to 1.405 g / cm³, and even more preferably 1.398 to 1.400 g / cm³. The density of the polyester substrate can be measured using an electronic hydrometer (product name "SD-200L", manufactured by ALFA MIGAGE Co., Ltd.).

[0052] (Thickness) From the viewpoint of controlling peelability, a polyester substrate thickness of 100 μm or less is preferred, 50 μm or less is more preferred, and 40 μm or less is further preferred. There is no particular limitation on the lower limit of the thickness, but from the viewpoint of improving strength and processability, 3 μm or more is preferred, 10 μm or more is more preferred, and 20 μm or more is further preferred. The thickness of the polyester substrate is assumed to be measured using a continuous stylus-type film thickness gauge. Specifically, the thickness of the polyester substrate is measured along a length of 10 μm using a continuous stylus-type film thickness gauge. This measurement is performed at 5 different locations in the width direction. The arithmetic mean of the obtained measurements is taken as the thickness.

[0053] <Particle-containing layer> The particle-containing layer refers to a layer containing particles. The particle-containing layer is a layer disposed on the surface opposite to the side where the release layer containing the polyester substrate is disposed, and it can improve the transportability of the release film. Specifically, it can improve winding quality (inhibit adhesion), suppress the generation of scratches and defects during transport, and reduce transport wrinkles during high-speed transport. The particle-containing layer can be disposed directly on the surface of the polyester substrate, or it can be disposed on the surface of the polyester substrate in between other layers, but from the viewpoint of superior adhesion, it is preferable to dispose directly on the surface of the polyester substrate.

[0054] Furthermore, it is preferable that the particle-containing layer contains a binder, and it may further contain additives. The particles, binder, and additives will be described below.

[0055] (Particles) The particle-containing layer contains organic particles. This helps to suppress the defect rate of ceramic capacitors. The particle-containing layer may also contain inorganic particles. When manufacturing ceramic capacitors using ceramic green sheets formed on the release surface, fewer inorganic particles are preferable from the viewpoint of reducing non-combustible detached particles and excellent suppression of the defect rate of ceramic capacitors. Specifically, the particle-containing layer has protrusions on the surface opposite to the polyester substrate, i.e., the transport surface. Of the protrusions observed on this transport surface, the proportion of protrusions formed by organic particles is preferably 50-100%, and more preferably 70-100%.

[0056] Furthermore, the transport surface was observed using a scanning electron microscope (SEM, "S-4800", manufactured by Hitachi High-Technologies Corporation) to analyze the particles forming the protrusions. Specifically, the transport surface was observed using an SEM at a magnification that brought 15 to 20 protrusions into the field of view (where 20,000x was used as the upper limit, and when more than 15 protrusions were present, any 15 were distinguished as organic or inorganic particles). At this time, even if dust and / or coarse condensed particles larger than 1 μm were present, the dust and coarse condensed particles were not counted. Regarding the particles observed in this area, an EDS (Energy Dispersive X-ray Spectroscopy) analysis device was used to analyze the elemental composition of each particle to determine whether it was an organic or inorganic particle. The ratio of the number of organic particles to the total number of particles observed in the aforementioned measurement area was calculated. This calculation was performed across 10 fields of view, and the arithmetic mean was set as the ratio of the bulges formed by the organic particles. Furthermore, based on the elemental analysis results of the particles, particles were classified as inorganic if the total content of inorganic elements (e.g., Si, etc.) with a valence of 1, excluding Na, was 1% by mass or more; otherwise, they were classified as organic particles.

[0057] Furthermore, similarly to the above, from the viewpoint of excellent defect rate suppression of ceramic capacitors, it is preferable that the transport surface has protrusions, and among the protrusions observed in the transport surface, the protrusion with the maximum protrusion height Sp is formed by organic particles. The method for determining whether the protrusion with the maximum protrusion height Sp on the transport surface of the peel film is formed by organic particles will be specifically described in the embodiments described later.

[0058] Resin particles are preferred as the organic particles contained in the particle layer. Examples of resins constituting the resin particles include acrylic resins such as polymethyl methacrylate (PMMA), polyester resins, polysiloxane resins, and styrene-acrylic resins. The resin particles may have a cross-linked structure. Examples of resin particles with a cross-linked structure include polyurethane cross-linked particles, acrylic cross-linked particles, and divinylbenzene cross-linked particles. It is preferred that the organic particles include at least one selected from the group consisting of styrene resins, polyurethane resins, acrylic resins, and divinylbenzene resins, and it is even more preferred that they include at least one selected from the group consisting of styrene resins, polyurethane resins, and acrylic resins. Furthermore, in this specification, acrylic resin refers to a resin containing constituent units derived from acrylates or methacrylates.

[0059] Commercially available acrylic resin particles include, for example, Eposter (registered trademark) MX020W, MX030W, MX050W, MX100W, MX200W and MX300W (manufactured by NIPPON SHOKUBAI CO., LTD.) and the Techpolymer (registered trademark) series (manufactured by Sekisui Kasei Co., Ltd.). Commercially available styrene resin particles include, for example, Nipol (registered trademark) UFN1008 (manufactured by Zeon Corporation). Commercially available polyurethane resin particles include, for example, Artpearl (registered trademark) C-1000T and MM110SMA (manufactured by Negami Chemical Industrial Co., Ltd.).

[0060] The average particle size of the organic particles contained in the particle layer is not particularly limited, but 1 nm to 3 μm is preferred, 40 nm to 2 μm is more preferred, and 50 nm to 1 μm is even more preferred. The shape of the particles is not particularly limited, and examples include rice-grain-shaped, spherical, cubic, spindle-shaped, scaly, aggregated, and amorphous shapes. Aggregate refers to the state of primary particle aggregation. The shape of aggregated particles is not limited, but spherical or amorphous shapes are preferred.

[0061] The particles contained in the particle layer may be of one type or two or more types. When the particle layer contains two or more types of particles with different particle sizes, it is preferable that the particle layer contains at least one type of particle with an average particle size within the above-mentioned range, and it is even more preferable that the two or more types of particles with different particle sizes are all particles with an average particle size within the above-mentioned range.

[0062] From the viewpoint of conveyability 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 further 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.

[0063] (Non-polyester resin (adhesive)) The particle-containing layer contains a non-polyester resin. The non-polyester resin contained in the particle-containing layer functions as an adhesive. There are no particular limitations on the non-polyester resin, as long as it is a resin other than polyester resin. Examples include acrylic resin, polyurethane resin, olefin resin, polyvinyl alcohol resin, and acrylonitrile butadiene resin. From the viewpoint of superior performance of the present invention, acrylic resin, polyurethane resin, or olefin resin is preferred. The non-polyester resin (especially acrylic resin, polyurethane resin, and olefin resin) has a different solubility parameter (SP value) than the polyester resin. That is, because the compatibility of acrylic resin, polyurethane resin, and olefin resin with polyester resin is insufficient, impurities such as oligomers are less likely to precipitate from the polyester substrate to the transport surface via the particle-containing layer. Therefore, it is anticipated that protrusions caused by impurities contained in the polyester substrate are less likely to form on the transport surface.

[0064] There are no particular limitations on the non-polyester resins such as acrylic resin, polyurethane resin, and olefin resin mentioned above; known resins can be used. The non-polyester resin can be an acid-modified resin. Furthermore, the particle layer can contain a polyester resin.

[0065] The acrylic resin is a resin containing constituent units derived from (meth)acrylates, and may also be copolymerized with vinyl monomers such as styrene. There are no particular limitations on the acrylic resin, but it is preferable to contain constituent units derived from (meth)acrylates having alkyl groups having 1 to 12 carbon atoms, and even more preferable to contain constituent units derived from (meth)acrylates having alkyl groups having 1 to 8 carbon atoms. The acrylic resin may contain an acid-modifying component. The acrylic resin may also contain constituent units derived from (meth)acrylic acid as an acid-modifying component. Furthermore, (meth)acrylic acid can form an anhydride, and may also be neutralized by at least one selected from alkali metals, organic amines, and ammonia.

[0066] The acid value of the acrylic resin is preferably below 30 mg KOH / g, and more preferably below 20 mg KOH / g. There is no particular limitation on the lower limit of the acid value, for example, 0 mg KOH / g, but from the point of view of coating as an aqueous dispersion, 2 mg KOH / g or above is preferred. By setting the acid value of the acrylic resin to the above range and / or including (meth)acrylate constituent units derived from alkyl groups having 1 to 12 carbon atoms, it is possible to make it a resin that is less compatible with polyester resin, further suppressing the precipitation of impurities such as oligomers contained in the polyester substrate into the particle-containing layer, and further suppressing defects in ceramic green sheets.

[0067] Any olefin resin can be a resin whose main chain contains olefin-derived structural units. By having olefin-derived structural units in the main chain, it is possible to make it a resin that is not easily compatible with polyester resin, thereby suppressing the precipitation of impurities such as oligomers contained in the polyester substrate into the particle-containing layer and suppressing defects in ceramic green sheets. There are no particular limitations on the olefin, but alkenes with 2 to 6 carbon atoms are preferred, ethylene, propylene, or hexene are more preferred, and ethylene is even more preferred. Relative to all the structural units of the polyolefin, it is preferred that the polyolefin contains 50 to 99 moles of olefin-derived structural units, and more preferably 60 to 98%.

[0068] As an 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.

[0069] Commercially available acid-modified olefin resins include, for example, the ZAIKTHENE (registered trademark) series such as ZAIKTHENE AC, A, L, NC, and N (manufactured by SUMITOMO SEIKA CHEMICALS CO.,LTD.), the CHEMIPEARL (registered trademark) series such as CHEMIPEARL S100, S120, S200, S300, S650, and SA100 (manufactured by Mitsui Chemicals, Inc.), the Hi-tech (registered trademark) series such as Hi-tech S3121 and S3148K (manufactured by TOHO Chemical Industry Co.,Ltd.), the ARROW BASE (registered trademark) series such as ARROW BASE SE-1013, SE-1010, SB-1200, SD-1200, SD-1200, DA-1010, and DB-4010 (manufactured by UNITIKA LTD.), and HARDLEN. AP-2, NZ-1004, and NZ-1005 (manufactured by TOYOBO CO., LTD.) and Seporjon G315 and VA407 (manufactured by SUMITOMO SEIKA CHEMICALS CO., LTD.) are also preferred. Furthermore, the acid-modified olefin resins described in

[0022] to

[0034] of Japanese Patent Application Publication No. 2014-076632 are also preferred.

[0070] As for the polyurethane resin, there are no restrictions as long as it is a polymer containing polyurethane bonds, and known polyurethane resins such as the reaction products of isocyanate compounds and polyol compounds can be used. From the viewpoint of easy film formation by coating, it is preferable that the polyurethane resin is a polyurethane resin with acidic groups or in the form of polyurethane resin and dispersant. Examples of acidic groups include carboxyl groups. For example, the polyurethane resin can be made into a resin that is not easily compatible with polyester resin by adjusting the individual structures and hydrophobicity (hydrophilicity) of the polyol compound and / or isocyanate compound used as raw materials, which can suppress the precipitation of impurities such as oligomers contained in the polyester substrate into the particle-containing layer and suppress defects in ceramic green sheets. From the viewpoint of further improving defect suppression, it is preferable that the polyurethane resin contains a polyester structure. Commercially available polyurethane resins include, for example, HYDRAN (registered trademark) AP-20, AP-40N and AP-201 (all manufactured by DIC Corporation), TAKELAC (registered trademark) W-605, W-5030 and W-5920 (all manufactured by Mitsui Chemicals, Inc.), SUPERFLEX (registered trademark) 210 and 130, and ELASTRON (registered trademark) H-3-DF, E-37 and H-15 (all manufactured by DKS Co. Ltd.).

[0071] The non-polyester resin contained in the particle-containing layer may have a cross-linked structure. That is, the particle-containing layer may be a cross-linked film. In order to form a non-polyester resin with a cross-linked structure, a method for forming a particle-containing layer using a particle-containing layer forming composition containing a cross-linking agent, as described later, can be cited.

[0072] The particle-containing layer may contain only one type of binder, or it may contain two or more types of binders. Furthermore, the particle-containing layer may contain only one type of non-polyester resin, or it may contain two or more types of non-polyester resin. From the viewpoint of suppressing defects, the content of the binder (preferably a non-polyester resin) relative to the total mass of the particle-containing layer is preferably 30–99.8% by mass, and more preferably 50–99.5% by mass.

[0073] (Additives) The particle-containing layer may contain additives other than the particles and binders mentioned above. Examples of additives included in the particle-containing layer include surfactants, paraffin wax, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and mildew inhibitors.

[0074] Regarding the particle-containing layer, from the viewpoint of improving the smoothness of the area on the transport surface other than the portion where there are protrusions formed by particles, it is preferable to include a surfactant. There are no particular limitations on the surfactant, and examples include polysiloxane-based surfactants, fluorinated surfactants, and hydrocarbon-based surfactants, among which hydrocarbon-based surfactants are preferred.

[0075] As a polysiloxane surfactant, there are no particular restrictions as long as it has a silicone group as a hydrophobic group. Examples include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Commercially available polysiloxane surfactants include, for example, 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 Co., Ltd.), and 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.). (Manufactured by Ltd.)

[0076] As a fluorinated surfactant, there are no particular limitations as long as it has a fluorinated group as a hydrophobic group. Examples include perfluorooctane sulfonic acid and perfluorocarboxylic acid. Commercially available fluorinated surfactants include MEGAFACE (registered trademark) F-114, F-410, F-440, F-447, F-553 and F-556 (manufactured by DIC Corporation), and Surflon (registered trademark) 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, from the viewpoint of improving environmental adaptability, it is preferable to use surfactants derived from perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), which are straight-chain perfluoroalkyl compounds with 7 or more carbon atoms.

[0077] Examples of hydrocarbon-based surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include alkyl sulfates, alkylbenzene sulfonates, 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 having both anionic and cationic sites within the molecule.

[0078] Commercially available anionic surfactants include, for example, RAPISOL (registered trademark) A-90, A-80, BW-30, B-90 and C-70 (and above, manufactured by NOF CORPORATION), NIKKOL (registered trademark) OTP-100 (and above, manufactured by Nikko Chemicals Co., Ltd.), Kohacool (registered trademark) ON, L-40 and PHOSPHANOL (registered trademark) 702 (and above, manufactured by TOHO Chemical Industry Co., Ltd.), and BEAULIGHT (registered trademark) A-5000 and SSS (and above, manufactured by Sanyo Chemical Industries, Ltd.). Commercially available nonionic surfactants include, for example, NAROACTY (registered trademark) CL-95 and HN-100 (product name, manufactured by Sanyo Chemical Industries, Ltd.), Risorex BW400 (product name, manufactured by Kokyu Alcohol Kogyo Co., Ltd.), EMLEX (registered trademark) ET-2020 (and above, manufactured by NIHON EMULSION Co., Ltd.), SURFINOL (registered trademark) 104E, 420, 440, 465, and Dynol (registered trademark) 604, 607 (and above, manufactured by Nissin Chemical Industry CO.,Ltd.).

[0079] Among hydrocarbon-based surfactants, anionic surfactants and / or nonionic surfactants are preferred, with anionic surfactants being even more preferred.

[0080] From the viewpoint of further improving smoothness, it is preferable that anionic hydrocarbon surfactants have a plurality of hydrophobic terminal groups. The hydrophobic terminal group can be part of the hydrocarbon group of the hydrocarbon surfactant. For example, hydrocarbon surfactants having a hydrocarbon group containing a branched structure at the end have a plurality of hydrophobic terminal groups. Examples of anionic hydrocarbon surfactants having a plurality of hydrophobic terminal groups include sodium di-2-ethylhexyl sulfosuccinate (having 4 hydrophobic terminal groups), sodium di-2-ethyloctyl sulfosuccinate (having 4 hydrophobic terminal groups), and branched alkylbenzene sulfonates (having 2 hydrophobic terminal groups).

[0081] One type of surfactant may be used, or two or more types may be used in combination. When the particulate layer contains a surfactant, the surfactant content is preferably 0.1 to 10% by mass relative to the total mass of the particulate layer. From the viewpoint of superior surface smoothness, 0.1 to 5% by mass is more preferred, and 0.5 to 2% by mass is even more preferred.

[0082] There are no particular limitations on the type of paraffin wax used; it can be either natural or synthetic. Examples of natural waxes include palm wax, candelilla wax, beeswax, lignite wax, solid paraffin wax, and petroleum wax. Furthermore, lubricants described in

[0087] of International Publication No. 2017 / 169844 can also be used. A paraffin wax content of 0 to 10% by mass relative to the total mass of the particle layer is preferred.

[0083] [Properties of the Particle-Containing Layer] (Thickness) The particle-containing layer is formed, for example, by coating a composition containing organic particles and a non-polyester resin onto a surface of a polyester substrate, and its thickness is generally less than 1 μm. Alternatively, it can be formed by co-extruding the polyester substrate and the particle-containing layer, as described later, in which case the thickness of the particle-containing layer is generally 1 to 10 μm. A thickness of 1 nm to 3 μm is preferred. In the case of manufacturing by coating, from the viewpoint of manufacturing suitability and haze reduction, 1 to 500 nm is preferred, 1 to 250 nm is more preferred, 10 to 100 nm is further preferred, and 20 to 100 nm is particularly preferred. The thickness of the particle-containing layer is defined as the arithmetic mean of the thickness at five points on a section having a cross-section perpendicular to the main surface of the release film, measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0084] (Surface Free Energy of the Conveying Surface) The surface free energy of the surface (conveying surface) on the opposite side of the polyester substrate containing the particle layer is preferably 25-60 mJ / m², more preferably 25-45 mJ / m², and even more preferably 30-45 mJ / m². By having the surface free energy of the conveying surface within the above range, the precipitation of impurities such as oligomers contained in the polyester substrate onto the conveying surface can be further suppressed, and defects in the ceramic green sheet can be further suppressed.

[0085] (Maximum protrusion height Sp and average surface roughness Sa of the conveying surface) Regarding the particle-containing layer, a maximum protrusion height Sp of 10–5000 nm is preferred. From the viewpoint of excellent high-speed conveying performance of the release film, better suppression of defects in ceramic green sheets, and superior winding performance even with high-speed conveying of the release film, 25–1000 nm is more preferred, 25–600 nm is further preferred, and 30–500 nm is especially preferred. Furthermore, an average surface roughness Sa of 0–10 nm is preferred, 0–5 nm is more preferred, and 1–3 nm is further preferred. The measurement methods for the maximum protrusion height Sp and average surface roughness Sa of the conveying surface are the same as those for the maximum protrusion height Sp and average surface roughness Sa of the release surface described above.

[0086] <Properties of the release film> [Thickness] From the viewpoint of superior peelability, a release film thickness of 100 μm or less is preferred, 50 μm or less is more preferred, and 40 μm or less is even more preferred. Furthermore, from the viewpoint of improving strength and processability, a release film thickness of 3 μm or more is preferred, 10 μm or more is more preferred, and 20 μm or more is even more preferred.

[0087] <Method for Manufacturing Release Film> A method for manufacturing a release film will be described. There are no particular limitations on the method for manufacturing the release film, as long as it yields a release film with the aforementioned characteristics; known methods can be cited. From the viewpoint of being able to manufacture the release film with good productivity, a preferred method for manufacturing the release film includes: an extrusion molding process, forming an unstretched polyester substrate by extrusion molding; and a stretching process, performing a first stretching process and a second stretching process in stages or simultaneously, wherein the first stretching process stretches the unstretched polyester substrate along either the conveying direction or the width direction to form a uniaxially aligned polyester substrate, and the second stretching process stretches the uniaxially aligned polyester substrate along the other direction, either the conveying direction or the width direction, to form a biaxially aligned polyester substrate, further including: A particle-containing layer forming process involves coating a particle-containing layer forming composition onto one surface of a polyester substrate between an extrusion molding process and a stretching process, between a first stretching process and a second stretching process, or after a stretching process, to form a particle-containing layer. A release layer forming process involves coating a release layer forming composition onto the other surface of a polyester substrate between an extrusion molding process and a stretching process, between a first stretching process and a second stretching process, or after a stretching process, to form a release layer. The preferred manufacturing methods described above will be described in detail below.

[0088] [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 molten resin containing raw material polyester resin into a film to form an unstretched polyester substrate. Regarding the raw material polyester resin, it has the same meaning as polyester resin described in the above (polyester resin) item. In addition, in order to produce a polyester substrate that is substantially free of particles, it is preferable to use polyester granules that do not contain particles during extrusion molding.

[0089] Extrusion molding is a method, for example, of shaping a raw material resin into a desired shape by extruding a melt of the raw material resin using an extruder. The melt extruded from the die is shaped into a film by cooling. For example, by contacting the melt with a casting roll, cooling and solidifying the melt on the casting roll, the melt can be shaped into a film. Further blowing air (preferably cold air) onto the melt during cooling is preferable.

[0090] [Stretching Process] The stretching process is a process in which a first stretching process and a second stretching process are performed in stages or simultaneously. The first stretching process stretches an unstretched polyester substrate along either the conveying direction or the width direction to form a uniaxially oriented polyester substrate. The second stretching process stretches the uniaxially oriented polyester substrate along 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 processes is a longitudinal stretching process that stretches the polyester substrate along the conveying direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first and second stretching processes is a transverse stretching process that stretches the polyester substrate along the width direction (hereinafter also referred to as "transverse stretching"). During stretching, the polyester polymers align in all directions.

[0091] The above-described stretching process can be biaxial stretching performed simultaneously with longitudinal and transverse stretching, or it can be sequential biaxial stretching performed in stages, where longitudinal 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 description focuses on the longitudinal stretching → transverse stretching configuration, but the manufacturing method described above is not limited to this configuration.

[0092] The stretching ratio in the longitudinal stretching process is appropriately set, preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and further 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 further preferably 1200 to 1400% / second. Here, "stretching speed" is a percentage value obtained by dividing the length Δd of the polyester substrate stretched in the conveying direction in 1 second in the longitudinal stretching process by the length d0 of the polyester substrate in the conveying direction before stretching. In the longitudinal stretching process, it is preferable to heat the unstretched polyester substrate. This is because longitudinal stretching is facilitated by heating.

[0093] In the transverse stretching process, it is preferable to preheat the uniaxially oriented polyester substrate before transverse stretching. By preheating the uniaxially oriented polyester substrate, transverse stretching of the uniaxially oriented polyester substrate can be easily performed. There is no particular limitation on the stretching ratio (transverse stretching ratio) in the width direction of the uniaxially oriented polyester substrate in the transverse stretching process, but it is preferable to have a higher stretching ratio than that in the longitudinal stretching process described above. A stretching ratio of 3.0 to 6.0 times is preferable, 3.5 to 5.0 times is more preferable, and 3.5 to 4.5 times is even more preferable. A stretching speed of 8 to 45% / second is preferable, 10 to 30% / second is more preferable, and 15 to 20% / second is even more preferable.

[0094] [Particle-containing layer formation process] The particle-containing layer formation process is a process in which a particle-containing layer forming composition comprising organic particles and non-polyester resin is coated onto one surface of a polyester substrate to form a particle-containing layer. The particle-containing layer formation process is performed, for example, between an extrusion molding process and a first stretching process, between a first stretching process and a second stretching process, or after a stretching process. The particle-containing layer formed on one surface of the polyester substrate by the particle-containing layer formation process has the same meaning as the layer described in the above-mentioned particle-containing layer item. Hereinafter, the forms of the particle-containing layer forming composition will be described.

[0095] First, the composition for forming a particle-containing layer will be described. The composition for forming a particle-containing layer can be prepared by mixing organic particles contained in the particle-containing layer, a non-polyester resin, additives added as needed, and a solvent. For example, water and alcohol solvents can be used as solvents.

[0096] The composition for particle layer formation may contain only one solvent or two or more solvents. The solvent content is preferably 80-99.5% by mass, and more preferably 90-99% by mass, relative to the total mass of the composition for particle layer formation. That is, in the composition for particle layer formation, the total content of components other than solvents (solid components) relative to the total mass of the composition for particle layer formation is preferably 0.5-20% by mass, and more preferably 1-10% by mass.

[0097] Regarding the organic particles, non-polyester resins, and additives added as needed contained in the composition for forming a particle layer, the preferred embodiments of these components are as described in the section on particle-containing layers above. For each component in the composition for forming a particle layer other than the solvent, it is preferable to adjust the content of each component in the composition for forming a particle layer such that the content of each component relative to the total mass of the solid components of the composition for forming a particle layer is the same as the preferred content of each component relative to the total mass of the particle-containing layer.

[0098] Furthermore, the composition for forming particle layers may include a crosslinking agent. There are no particular limitations on the crosslinking agent, and known crosslinking agents can be used. Examples of crosslinking agents include melamine-based compounds, oxazoline-based compounds, epoxy-based compounds, isocyanate-based compounds, and carbodiimide-based compounds, with oxazoline-based compounds and carbodiimide-based compounds being preferred. Examples of commercially available products include CARBODILITE V-02-L2 (manufactured by Nisshinbo Co., Ltd.) and EPOCROS K-2020E (manufactured by NIPPON SHOKUBAI CO.,LTD.). For details regarding epoxy-based compounds, isocyanate-based compounds, and melamine-based compounds, please refer to

[0081] to

[0083] of Japanese Patent Application Publication No. 2015-163457. The crosslinking agent described in

[0082] to

[0084] of International Patent Application Publication No. 2017 / 169844 can also be used more preferably. For carbodiimide compounds, the descriptions in

[0038] to

[0040] of Japanese Patent Application Publication No. 2017-087421 can be consulted. Regarding oxazoline compounds, carbodiimide compounds, and isocyanate compounds, the crosslinking agent described in

[0074] to

[0075] of International Patent Application Publication No. 2018 / 034294 is also more preferably used. The content of the crosslinking agent is preferably 0 to 50% by mass relative to the total mass of the particle layer. The mass ratio of the crosslinking agent to the binder in the particle layer forming composition is preferably 2 to 50% by mass.

[0099] There are no particular limitations on the coating method for the composition containing the particle layer, and known methods can be used. Examples of coating methods include spraying, slot coating, roller coating, blade coating, spin coating, bar coating, and dip coating.

[0100] It is preferable that the particle-containing layer formation process is performed between the first stretching process and the second stretching process. It is preferable that the heating temperature for forming the particle-containing layer is below 180°C, more preferably below 150°C, and further preferably below 120°C. There is no particular limitation on the lower limit, and it can be above 60°C.

[0101] Furthermore, in order to improve the adhesion between the polyester substrate and the particle-containing layer, the surface of the polyester substrate may be pretreated with adhesive coating, corona treatment and plasma treatment before the particle-containing layer is applied.

[0102] [Release Layer Forming Process] The release layer forming process is a process in which a release layer forming composition is coated on the surface of a polyester substrate opposite to the particle-containing layer to form a release layer. The release layer forming 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 release layer forming process is performed after the stretching process, it is preferable to perform it after the cooling process described later, and even more preferably after the winding process and the finishing process described later. The release layer formed on one surface of the polyester substrate by the release layer forming process has the same meaning as the layer described in the release layer section above.

[0103] First, the composition for forming the release layer will be described. The composition for forming the release layer can be prepared by mixing a polysiloxane compound, other resins as needed, 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.

[0104] The composition for forming the release layer may contain only one solvent or two or more solvents. The solvent content is preferably 80-99.5% by mass, and more preferably 90-99% by mass, relative to the total mass of the composition for forming the release layer. That is, in the composition for forming the release layer, the total content of components other than solvents (solid components) relative to the total mass of the composition for forming the release layer is preferably 0.5-20% by mass, and more preferably 1-10% by mass.

[0105] Regarding the polysiloxane, other resins, and additives added as needed contained in the composition for forming the release layer, preferred embodiments of these are included as described in the section on the release layer. Furthermore, the composition for forming the release layer contains the aforementioned resin and solvent, and may, as needed, contain the aforementioned catalyst used for curing the aforementioned additives and / or resins. Also, it is preferable that the composition for forming the release layer contains a crosslinking agent. There are no particular limitations on the crosslinking agent, and known crosslinking agents can be used. Furthermore, the composition for forming the release layer may contain a polymerization initiator. For example, photopolymerization initiators can be used, and known initiators can be used. For each component in the composition for forming the release layer other than the solvent, it is preferable to adjust the content of each component in the composition for forming the release layer such that the content of each component is the same as the content of each component relative to the total mass of the solid components of the composition for forming the release layer relative to the total mass of the release layer.

[0106] There are no particular limitations on the coating method for the composition used to form the release layer, and known methods can be used. Specific examples of coating methods include those described in the particle layer formation process.

[0107] The heating temperature for forming the release layer is preferably below 180°C, more preferably below 150°C, and even more preferably below 120°C. There is no particular limitation on the lower limit, and it can be above 60°C.

[0108] Furthermore, in order to improve the adhesion between the polyester substrate and the release layer, the surface of the polyester substrate may be pretreated with adhesive coating, corona treatment and plasma treatment before the release layer is applied.

[0109] [Heat Setting Process] The above-described method for manufacturing a release film may include a heat setting process as a heat treatment of the polyester film obtained in the stretching process after the stretching process. In the heat setting process, the polyester film obtained by the stretching process is heated and heat-set. Heat setting causes the polyester resin to crystallize, thereby suppressing the shrinkage of the polyester substrate. The surface temperature (heat setting temperature) of the polyester film in the heat setting process is not particularly limited, but it is preferable to be below 240°C, more preferably below 235°C, and further preferably below 230°C. There is no particular limitation on the lower limit, but 190°C or higher is preferable, 200°C or higher is more preferably, and 210°C or higher is further preferably. The heating time in the heat setting process is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and further preferably 5 to 10 seconds.

[0110] [Heat Relief Process] The above-described method for manufacturing the release film can include a heat relief process after the heat setting process. In the heat relief process, it is preferable to perform heat relief by heating the polyester film heat-set by the heat setting process at a temperature lower than that of the heat setting process. Heat relief can mitigate residual strain in the polyester film. The surface temperature of the polyester film in the heat relief process (heat relief temperature) is preferably at least 5°C lower than the heat setting temperature, more preferably at least 15°C lower, further preferably at least 25°C lower, and especially preferably at least 30°C lower. That is, a heat relief temperature of 235°C or lower is preferable, 225°C or lower is more preferable, 210°C or lower is even more preferable, and 200°C or lower is especially preferable. The lower limit of the heat relief temperature is preferably 100°C or higher, more preferably 110°C or higher, and further preferably 120°C or higher.

[0111] [Cooling Process] The above-described method for manufacturing the release film may include a cooling process for cooling a heat-mitigated polyester film. In the above manufacturing method, it is preferable that the cooling rate of the polyester film in the cooling process is greater than 2000°C / min but less than 4000°C / min, more preferably 2000–3500°C / min, further preferably greater than 2200°C / min but less than 3000°C / min, and especially preferably 2300–2800°C / min. It is also preferable that the cooling process includes a process for extending the heat-mitigated polyester film along its width (an extension process). It is preferable that the width extension rate of the polyester film in the extension process, i.e., the ratio of the width of the polyester film at the end of the cooling process to the width of the polyester film before the start of the cooling process, is 0% or more, more preferably 0.001% or more, and further preferably 0.01% or more. There is no particular limit to the upper limit of the expansion rate, but below 1.3% is better, below 1.2% is even better, and below 1.0% is even better.

[0112] [Rolling process] The above manufacturing method may include a winding process of obtaining a roll-shaped polyester film by winding the polyester film obtained through the above process.

[0113] [Trimming Process] The manufacturing method may further include a trimming process of continuously cutting at least one end of the polyester film in the width direction along the conveying direction before performing the winding process described above.

[0114] [Other conditions] There are no particular restrictions on the conveying speed of the polyester film in the processes other than the longitudinal stretching process of this manufacturing method. In the transverse stretching process, heat setting process, heat tempering process and cooling process, from the point of view of productivity and quality, 50 to 200 m / min is preferred, and 80 to 150 m / min is even better.

[0115] In the above-described method for manufacturing a release film, a combination of two or more preferred states is a more preferred state.

[0116] Furthermore, regarding the above-described method for manufacturing the release film, a method for forming a particle-containing layer by coating a particle-containing layer forming composition in a particle-containing layer forming process has been described. However, the method for forming the particle-containing layer is not limited to the above-described form, and known methods can be used. For example, a method for forming an unstretched polyester substrate with a particle-containing layer laminated by co-extrusion molding can be cited. As a method for manufacturing the release film, a process including coating the above-described particle-containing layer forming composition onto one surface of the polyester substrate is preferred.

[0117] Furthermore, in the above-described method for manufacturing a release film, a release layer forming process is shown to be performed simultaneously with, before, or after a stretching process of stretching an unstretched polyester substrate and / or a particle-containing layer forming process of forming a particle-containing layer on one surface of the polyester substrate. However, the timing of the release layer forming process is not limited to the above-described manner. For example, after performing the above-described extrusion molding process, the above-described stretching process, and the above-described particle-containing layer forming process, and after producing a laminated film having a polyester substrate and a particle-containing layer formed on one surface of the polyester substrate, a release layer forming composition is coated on the surface of the polyester substrate opposite to the particle-containing layer as a release layer forming process relative to the produced laminated film, thereby forming a release layer. This allows the manufacture of a release film that sequentially comprises a particle-containing layer, a polyester substrate, and a release layer.

[0118] [Application of the release film] The release film is preferably used as a release film (carrier film) for the manufacture of ceramic green sheets. Ceramic green sheets manufactured using the above-mentioned release film can be better used in the manufacture of ceramic capacitors that require multilayer internal electrodes due to miniaturization and increased capacitance. There are no particular limitations on the method for manufacturing ceramic green sheets using the above-mentioned release film; known methods can be implemented. For example, a method for manufacturing ceramic green sheets can be: coating a prepared ceramic slurry onto the release surface of the release film, and drying to remove the solvent contained in the ceramic slurry. There are no particular limitations on the coating method of the ceramic slurry; for example, known methods such as coating a ceramic slurry by means of a reverse roller method to disperse ceramic powder and binder in a solvent, and removing the solvent by heating and drying, can be used. There are no particular limitations on the binder; for example, polyvinyl butyral can be used. Furthermore, there are no particular limitations on the solvent; for example, ethanol and toluene can be used.

[0119] Ceramic green sheets manufactured in this manner are used to manufacture ceramic capacitors. As a method for manufacturing ceramic capacitors using ceramic green sheets, known methods can be applied; for example, the following method can be used. First, internal electrodes are formed by coating or printing a release film and a conductive paste onto a laminate of ceramic green sheets manufactured by the above method. Next, the release film is removed from the laminate of ceramic green sheets, and ceramic green sheets with internal electrodes attached are sequentially laminated. An intermediate laminate is formed by pressing the resulting laminate. After cutting the intermediate laminate into a desired shape, the cut intermediate laminate is calcined. Then, external electrodes, electrically connected to the internal electrodes using a conductive paste such as silver, are formed on the two end faces of the calcined intermediate laminate, thereby obtaining a ceramic capacitor.

[0120] Furthermore, the release film of the present invention can also be used as a protective film for dry film photoresist, a film for sheet forming such as a decorative layer and a resin sheet, a release film for manufacturing processes such as semiconductor manufacturing processes, a release film for polarizer manufacturing processes, and a separator for adhesive films such as labels, medical devices, and office supplies. [Example]

[0121] Hereinafter, embodiments will be provided to further illustrate the present invention. The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. Furthermore, unless otherwise specified, "parts" and "%" are based on mass.

[0122] [Example 1] <Extrusion Molding Process> Polyethylene terephthalate (PET) particles were manufactured using a titanium compound (citric acid chelate titanium complex, VERTEC AC-420, manufactured by Johnson Matthey PLC) as a polymerization catalyst, as disclosed in Japanese Patent No. 5575671. Specifically, the mixture was prepared in an amount of 390 kg of ethylene glycol relative to 1 ton (1000 kg) of phthalic acid and 9 ppm by mass of Ti atoms relative to the PET that produced the titanium compound. The resulting mixture was continuously fed into a reaction apparatus for esterification. Furthermore, magnesium acetate tetrahydrate in an amount of 81 ppm by mass relative to the PET produced and trimethyl phosphate in an amount of 73 ppm by mass relative to the PET produced were added to the mixture to carry out a polycondensation reaction and produce PET particles. The obtained granules were dried to a moisture content of less than 50 ppm and then fed into the hopper of a 30 mm diameter single-shaft compounding extruder. The mixture was then melted and extruded at 280°C. The melt was passed through a filter (3 μm pore size) and extruded from a die into a cooling roller at 25°C, thereby obtaining an unstretched polyester substrate made of polyethylene terephthalate (PET). The extruded melt was then brought into close contact with the cooling roller using an electrostatic application method. The PET constituting the unstretched polyester substrate has a melting point (Tm) of 258°C and a glass transition temperature (Tg) of 80°C.

[0123] <Longitudinal Stretching Process】The above-mentioned unstretched film is subjected to a longitudinal stretching process by the following method. The preheated unstretched film is stretched longitudinally (in the conveying direction) between two pairs of rollers with different circumferential speeds under the following conditions to produce a uniaxially aligned film. (Longitudinal stretching conditions) Preheating temperature: 75℃ Stretching temperature: 90℃ Stretching ratio: 3.4 times Stretching speed: 1300% / second

[0124] <Particle-containing layer formation process and release layer formation process> A component A1 (a component for forming a particle layer) is coated on one side of a longitudinally stretched uniaxially aligned polyester substrate using a doctor blade coater. A component L1 (a component for forming a release layer) is coated on the side opposite to the particle-containing surface of the uniaxially aligned polyester substrate using the same doctor blade coater. The resulting coating film, dried with hot air at 100°C, forms a particle-containing layer and a release layer. In other words, component A1 and component L1 are machine-coated onto the uniaxially aligned polyester substrate. At this time, the coating amounts of component A1 and component L1 are adjusted so that the thickness of the particle-containing layer in the transversely stretched state is 40 nm and the thickness of the release layer is 100 nm.

[0125] (Composition A1) Composition A1 was prepared by mixing the components shown below. After the prepared composition A1 was subjected to filtration treatment using a filter with a pore size of 6 μm (F20, manufactured by Mahle Filter Systems Japan Corp) and membrane degassing (2x6 Radial Flow SuperPhobic, manufactured by Polypore), the obtained composition A1 was coated on the surface of a uniaxially aligned thin film. • Polyurethane resin 1 (HYDRAN AP-40N, manufactured by DIC CORPORATION, aqueous dispersion with solids concentration adjusted to 25% by mass): 157 parts by mass • Anionic hydrocarbon surfactant (RAPISOL A-90, sodium di-2-ethylhexyl sulfosuccinate, manufactured by NOF CORPORATION, aqueous dispersion with solids concentration of 1% by mass): 56 parts by mass • Organic particles O1 (crosslinked PMMA particles, EPOSTAR MX050W, manufactured by NIPPON SHOKUBAI CO., LTD., average particle size 70 nm, aqueous dispersion with solids concentration of 10% by mass): 8 parts by mass • Water: 779 parts by mass

[0126] (Composition L1) Composition L1 was prepared by mixing the components shown below. The prepared composition L1 was subjected to the same filtration and membrane degassing process as composition A1 to obtain composition L1. • Polysiloxane emulsion (DEHESIVE EM480, manufactured by Wacker Asahikasei Silicon Co., Ltd.): 20 parts by mass • Polysiloxane emulsion (CROSSLINKER V72, manufactured by Wacker Asahikasei Silicon Co., Ltd.): 3 parts by mass • Silicate coupling agent (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.1 parts by mass • Water: 77 parts by mass

[0127] <Transverse Stretching Process> A biaxially aligned film was manufactured by stretching a polyester substrate that had undergone longitudinal stretching, release layer formation, and particle-containing layer formation processes in the width direction using a tenter frame under the following conditions. (Transverse Stretching Conditions) Preheating temperature: 100℃ Stretching temperature: 120℃ Stretching ratio: 4.2 times Stretching speed: 50% / second

[0128] <Heat Setting Process> A heat setting process is performed by heating the biaxially aligned film that has undergone the above-described transverse stretching process using a tenter frame under the following conditions. (Heat Setting Conditions) Heat setting temperature: 227°C Heat setting time: 6 seconds

[0129] <Heat Relief Process> Next, the heat-set film is heated under the following conditions to perform a heat relief process that eases the tension of the film. Furthermore, during the heat relief process, the film width is reduced compared to the end of the heat-setting process by decreasing the distance between the holding members of the tenter frame holding both ends of the film (tenting frame width). The heat relief rate Lr is calculated using the formula Lr = (L1-L2) / L1×100, based on the film width L2 at the end of the heat relief process relative to the film width L1 at the beginning of the heat relief process. (Heat Relief Conditions) Heat Relief Temperature: 190℃ Heat Relief Rate Lr: 4%

[0130] <Cooling Process and Extended Process> A cooling process is performed to cool a thermally moderated film under the following conditions. Furthermore, during the cooling process, an extended process is implemented to expand the film width compared to the end of the thermally moderated process by increasing the width of the tenter frame. The following cooling rate is calculated as follows: the residence time of the film from when it enters the cooling section of the stretching machine to when it exits is taken as the cooling time ta, and the temperature difference ΔT (°C) between the film surface temperature measured when it enters the cooling section and the film surface temperature measured when it exits the cooling section is divided by the cooling time ta. Furthermore, the following extended rate ΔL is calculated based on the film width L3 at the end of the cooling process relative to the film width L2 of the polyester film at the beginning of the cooling process, using the formula ΔL = (L3 - L2) / L2 × 100. (Cooling Conditions) Cooling Rate: 2500°C / min (Extended Conditions) Extended Rate ΔL: 0.6%

[0131] <Roll-up Process> The film cooled by the cooling process is continuously cut along the conveying direction at a distance of 20 cm from both ends in the width direction of the film using a trimming device, and the two ends of the film are trimmed. Next, the area from both ends of the film to 10 mm in the width direction is extruded (knurled) and then the film is wound up at a tension of 40 kg / m. A release film is produced by the above method. The thickness of the obtained release film is 31 μm, the width is 1.5 m, and the winding length is 7000 m.

[0132] [Examples 2-9 and 12-13] As described in Table 1, except for changing the types of particles and resin in the particle-containing layer and the thickness of each layer, the release films of Examples 2-9 and 12-13 were prepared in the same manner as in Example 1. In addition, except that the organic particles O1 in Example 4 were replaced with 6.7 parts by mass of organic particles O2 (EPOSTAR (registered trademark) MX100W, average particle size 150nm, aqueous dispersion with a solid content concentration of 10% by mass) and 1.3 parts by mass of organic particles O4 (EPOSTAR (registered trademark) MX300W, average particle size 450nm, aqueous dispersion with a solid content concentration of 10% by mass), composition A6 of Example 6 was prepared in the same manner as composition A4 of Example 4. Furthermore, except that organic particles O1 in Example 4 were replaced with 2.7 parts by mass of organic particles O3 (EPOSTAR (registered trademark) MX200W, average particle size 350 nm, aqueous dispersion with a solid content concentration of 10% by mass) and 5.3 parts by mass of inorganic particles I1 (SNOWTEX (registered trademark) MP-2040, manufactured by Nissan Chemical Corporation, colloidal silicon dioxide, average particle size 200 nm, aqueous dispersion with a solid content concentration adjusted to 10% by mass), composition A7 of Example 7 was prepared in the same manner as composition A4 of Example 4. Furthermore, except that organic particles O1 in Example 4 were replaced with 6.7 parts by mass of organic particles O2 (EPOSTAR (registered trademark) MX100W, average particle size 150 nm, aqueous dispersion with a solid content concentration of 10% by mass) and 1.3 parts by mass of organic particles O5 (Techpolymer (registered trademark) MB-4, manufactured by Sekisui Kasei Co., Ltd., average particle size 4 μm, aqueous dispersion with a solid content concentration adjusted to 10% by mass), composition A8 of Example 8 was prepared in the same manner as composition A4 of Example 4.

[0133] Composite A12 of Example 12 was prepared in the same manner as composition A4 of Example 4, except that the organic particles O1 in Example 4 were replaced with 7.0 parts by mass of organic particles O2 (EPOSTAR (registered trademark) MX100W, average particle size 150 nm, aqueous dispersion with a solid content concentration of 10% by mass) and 1.0 parts by mass of inorganic particles I1 (SNOWTEX (registered trademark) MP-2040, manufactured by Nissan Chemical Corporation, colloidal silicon dioxide, average particle size 200 nm, aqueous dispersion with a solid content concentration adjusted to 10% by mass). Except that organic particles O1 in Example 4 were replaced with 6.0 parts by mass of organic particles O3 (EPOSTAR (registered trademark) MX200W, average particle size 350 nm, aqueous dispersion with a solid content concentration of 10% by mass) and inorganic particles I2 (SNOWTEX (registered trademark) ZL, manufactured by Nissan Chemical Corporation, colloidal silicon dioxide, particle size 70-100 nm, adjusted to an aqueous dispersion with a solid content concentration of 10% by mass) in 2.0 parts by mass, composition A13 of Example 13 was prepared in the same manner as composition A4 of Example 4.

[0134] [Example 10] A biaxially aligned film was prepared according to the method described in Example 1, except that no release layer was formed. The obtained film was unwound, and the following composition L2 was coated on the side of the polyester substrate opposite to the particle-containing layer, so that the cured thickness was 500 nm. After drying the coated film at 90°C, a release layer was formed by heating at 120°C for 1 minute and performing thermosetting, thus preparing a release film.

[0135] (Composition L2) · Acrylic resin 2 (a copolymer of methyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate and methacrylic acid in a mass ratio of 47:26:20:7, in a toluene solution with a solid content of 40% by mass): 1.75 parts by mass · Polyester-modified polysiloxane resin (BYK-370, manufactured by BYK Japan KK, with a solid content concentration of 25% by mass): 0.05 parts by mass · Thermopolymerizable compound (hexamethoxymelamine, manufactured by Tokyo Chemical Industry Co.,LTD., with a solid content of 100% by mass): 0.25 parts by mass · Acid catalyst (p-toluenesulfonic acid, manufactured by FUJIFILM Wako Pure Chemical Corporation, with a solid content of 100% by mass): 0.02 parts by mass · Methyl ethyl ketone: 58 parts by mass · Toluene: 40 parts by mass

[0136] [Example 11] In the release layer formation process, a release film was prepared according to the method described in Example 10, except that composition L3 was used instead of composition L2. (Composition L3) · Amino alkyd resin (Tesfine 305, SHOWA DENKO MATERIALS CO., LTD., solid content 50% by mass): 2.0 parts by mass · Polyester modified polysiloxane resin (BYK-370, manufactured by BYK Japan KK, solid content concentration 25% by mass): 0.01 parts by mass · Acid catalyst (p-toluenesulfonic acid, manufactured by FUJIFILM Wako Pure Chemical Corporation, solid content 100% by mass): 0.02 parts by mass · Methyl ethyl ketone: 58 parts by mass · Toluene: 40 parts by mass

[0137] 〔Comparative Example 1〕 Except that 11 parts by mass of inorganic particles I1 (SNOWTEX MP-2040, manufactured by Nissan Chemical Corporation, colloidal silica, average particle size 200 nm, aqueous dispersion with a solid content concentration of 40% by mass) were used instead of organic particles O1, and "Surflon S-211" (manufactured by AGC SEIMI CHEMICAL CO., LTD., fluorinated surfactant) was used instead of "RAPISOL A-90" as a surfactant, composition CA1 was prepared according to the preparation method of composition A2 in Example 2. In the particle-containing layer formation process, except that composition CA1 was used instead of composition A1 and the thickness of the particle-containing layer was changed, and in the release layer formation process, the thickness of the release layer was changed, a release film was prepared according to the method described in Example 10.

[0138] [Comparative Example 2] Except that 8 parts by mass of organic particles O2 (crosslinked PMMA particles, EPOSTAR (registered trademark) MX100W, manufactured by NIPPON SHOKUBAI CO., LTD., with an average particle size of 150 nm and a solid content concentration of 40% by mass, an aqueous dispersion) was used to replace inorganic particles I1, and the copolymerized polyester resin contained in the polyester aqueous dispersion (Aw-1) prepared according to the method described in International Publication No. 2017 / 199774 was used to replace polyurethane resin 2, composition CA2 was prepared according to the preparation method of composition CA1 in Comparative Example 1. In the particle-containing layer formation process, except that composition CA2 was used to replace composition CA1, a release film was prepared according to the method described in Comparative Example 1.

[0139] [Comparative Example 3] In the release layer formation process, a release film was prepared according to the method described in Example 10, except that composition L4 was used instead of composition L2. (Composition L4) • Amino alkyd resin (Tesfine 305, SHOWA DENKO MATERIALS CO., LTD., solids 50% by mass): 2.0 parts by mass • Acid catalyst (p-toluenesulfonic acid, manufactured by FUJIFILM Wako Pure Chemical Corporation, solids 100% by mass): 0.02 parts by mass • Methyl ethyl ketone: 58 parts by mass • Toluene: 40 parts by mass

[0140] [Evaluation] The release films prepared in each embodiment and each comparative example were evaluated as follows.

[0141] <Defect Evaluation of Ceramic Green Sheets 1> 100 parts by weight of barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 8 parts by weight of polyvinyl butyral resin (manufactured by SEKISUI CHEMICAL CO., LTD., product name "S-LEC (registered trademark) B·K BM-2") as a binder, 4 parts by weight of dioctyl phthalate (manufactured by Kanto Chemical Co., Inc., dioctyl phthalate, grade I) as a plasticizer, and 135 parts by weight of a mixture of toluene and ethanol (mass ratio 6:4). The mixture was dispersed using a ball mill in the presence of zirconia beads, and the beads were removed from the resulting dispersion to prepare a ceramic slurry.

[0142] The release films obtained in each embodiment and comparative example were stored for one week under normal temperature and humidity (25°C, 50%RH). Using a die-coating machine, the aforementioned ceramic slurry was applied to the release surface of the stored release film over a width of 250 mm and a length of 10 m to achieve a film thickness of 1 μm after drying. The resulting coating was then dried at 100°C for 2 minutes using a dryer and then rolled into a roll. For the laminated film of ceramic green sheet and release film, a fluorescent lamp was shone from the release film side, and a 1 m² area on the surface of all formed ceramic green sheets was visually inspected to check for the presence of pinholes or other minor irregularities. Based on the number of identified defects, the defects on the surface of the ceramic green sheet were evaluated according to the following evaluation criteria.

[0143] (Evaluation Criteria) A: No uneven or concave defects were found on the surface of the ceramic green sheet. B: Uneven or concave defects were found on the surface of the ceramic green sheet.

[0144] <Defect Evaluation of Ceramic Green Sheets 2> Under normal temperature and humidity conditions, the release films obtained in each embodiment and comparative example were stored for 3 months. Except for using the release films after 3 months of storage, the defects on the surface of the ceramic green sheets were evaluated in the same manner as in Defect Evaluation 1. (Evaluation Criteria) A: No unevenness defects were found on the ceramic green sheet. B: 1 to 10 unevenness defects were found on the ceramic green sheet. C: 11 or more unevenness defects were found on the ceramic green sheet.

[0145] <High-speed winding performance (high-speed winding performance)> A high-speed winding test was conducted by winding the release films produced in the various embodiments and comparative examples under the following conditions. The release films were conveyed at a linear speed of 80 m / min and a tension of 7 kg / m, and while being pressed with a contact roller at a pressure of 30 kg / m, the release films were wound into a roll shape with a length of 6,000 m in the longitudinal direction using ABS (acrylonitrile-butadiene-styrene) resin core with a diameter of 6 inches (1 inch = 2.54 cm). The hardness of the contact roller was 60 degrees. The roll of the wound release film was visually observed, and the winding performance under high-speed conveying was evaluated based on the following evaluation criteria from the observation results.

[0146] (Coilability Evaluation Criteria) A: No winding offset was observed. B: Winding offset was confirmed.

[0147] <Defect Evaluation of Ceramic Layer During High-Speed ​​Transport> As a release film, in addition to using a release film wound under high-speed transport conditions according to the method described in the above-described method for evaluating the rollability during high-speed transport, a ceramic green sheet was provided on the release surface of the release film in the same manner as described in the method for evaluating the defects of ceramic green sheets 1. The obtained release film with the attached ceramic green sheet was unwound, and a ceramic green sheet formed on the release film was deposited on a glass substrate with an attached electrode, so that the ceramic green sheet was in contact with the glass substrate. The obtained laminate was hot-pressed (100°C, 0.5 MPa) using a heated roller. Then, the release film was peeled off from the laminate, and the glass substrate with the pressed ceramic green sheet was calcined at 400°C for 20 minutes. The calcination temperature was further increased to 580°C at a rate of 10°C per minute, and then calcined at 580°C for 30 minutes to obtain a glass substrate with a ceramic layer formed on its surface. The presence of uneven defects in the observation area (100mm × 100mm) of the obtained ceramic layer surface was observed using an optical microscope. Based on the number of defects identified in the observation area, the defects of the calcined ceramic layer were evaluated using the following evaluation criteria. It is believed that when the number of defects in the calcined ceramic layer identified by the above evaluation method is low, the formation of small uneven shapes that can affect the characteristics of the capacitor can be suppressed in multilayer ceramic capacitors manufactured using ceramic green sheets formed on the same release film release surface, thereby improving the performance of multilayer ceramic capacitors in suppressing the defect rate.

[0148] (Evaluation Criteria) A: No defects were found in the calcined ceramic layer. B: 1 to 3 defects were found in the calcined ceramic layer. C: More than 4 defects were found in the calcined ceramic layer.

[0149] <Peelability Evaluation> Except for adjusting the coating amount of the ceramic slurry to make the thickness of the ceramic green sheet (the dried slurry coating film) 3 μm, a release film attached to the ceramic green sheet was obtained in the same manner as described in the defect evaluation of the ceramic green sheet 1. Polyester adhesive tape No. 31B (manufactured by Nitto Denko Corporation) was attached to the surface of the ceramic green sheet in the release film attached to the ceramic green sheet. After standing at room temperature (25°C) for 24 hours in this state, the release film attached to the ceramic green sheet was cut into 20 mm widths to make samples. The adhesive tape side of the sample was fixed to the surface of a glass plate, and the release film was peeled from the ceramic green sheet using a Tensilon universal testing machine (manufactured by A&D Company, Limited) at a peel angle of 180° and a peel speed of 100 mm / min. The peeling force required was measured.

[0150] The peelability was evaluated based on the following criteria. (Evaluation Criteria) A: Peeling from the ceramic green sheet can be performed with a force of less than 45 mN. B: Peeling from the ceramic green sheet requires a force exceeding 45 mN and 100 mN. C: Peeling from the ceramic green sheet requires a force exceeding 100 mN.

[0151] The composition and characteristics of the particle layer and the release layer, as well as the evaluation results based on the above evaluation tests, of the release films manufactured in each embodiment and each comparative example are described in Table 1 below.

[0152] Table 1 shows the following ingredients used in the “Particles” and “Binder” columns, respectively. (Particles) • O1: Cross-linked PMMA particles, EPOSTAR (registered trademark) MX050W, manufactured by NIPPON SHOKUBAI CO., LTD., average particle size 70nm • O2: Cross-linked PMMA particles, EPOSTAR (registered trademark) MX100W, manufactured by NIPPON SHOKUBAI CO., LTD., average particle size 150nm • O3: Cross-linked PMMA particles, EPOSTAR (registered trademark) MX200W, manufactured by NIPPON SHOKUBAI CO., LTD., average particle size 350nm • O4: Cross-linked PMMA particles, EPOSTAR (registered trademark) MX300W, manufactured by NIPPON SHOKUBAI CO., LTD., average particle size 450nm • O5: Non-cross-linked PMMA particles, Techpolymer (registered trademark) MB-4, Sekisui Kasei Co., Ltd., average particle size 4.0μm • I1: Colloidal silicon dioxide, SNOWTEX (registered trademark) MP-2040, manufactured by Nissan Chemical Corporation, average particle size 200nm

[0153] (Adhesive) • Polyurethane resin 1: Manufactured by HYDRAN (registered trademark) AP-40N, DIC CORPORATION. • Polyurethane resin 2: Manufactured by ADEKA BONTITER (registered trademark) HUX-524, ADEKA Corporation. • Olefin resin: Manufactured by ZAIKTHENE (registered trademark) NC, SUMITOMO SEIKA CHEMICALS CO.,LTD. • Acrylic resin 1: A copolymer formed by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2. • Polyester resin: A copolymer formed by polymerizing dimethyl terephthalate, dimethyl isophthalate, 5-sodium sulfonyl isophthalate, ethylene glycol, and neopentyl glycol in a mass ratio of 194.2:184.5:14.8:185.1:185.1.

[0154] In Table 1, the “Thickness” column shows the thickness of the particle layer and the release layer, respectively. The thickness of each layer was measured as described above. After cutting the cross-section of the release film with a slicing machine, it was etched with Ar ions, Pt was deposited by vapor deposition, and the thickness was measured by observation with SEM (S-4800, manufactured by Hitachi High-Technologies Corporation).

[0155] In Table 1, the "Sp" column shows the maximum protrusion height Sp of the particle layer and the peeling layer, respectively, and the "Sa" column shows the average surface roughness Sa of the peeling layer. The definitions of the "maximum protrusion height Sp" and "average surface roughness Sa" of each layer are as described above, and the measurement method is also as described above, using an optical interferometer ("Vertscan R3300G Lite" manufactured by Hitachi High-Technologies Corporation). In Table 1, the "Surface E" column shows the surface free energy of the conveying surface and the peeling surface, respectively. The definition and measurement method of the surface free energy of each layer are as described above, obtained from the results of adding droplets of purified water, diiodomethane, and ethylene glycol to the peeling surface at 25°C using a contact angle meter ("DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.).

[0156] In Table 1, the column “Proportion of Organic Particle Protrusions” shows the proportion (number ratio) of protrusions formed by organic particles among the protrusions present on the conveying surface. The method for measuring the proportion of protrusions formed by organic particles is as described above. Among the protrusions present on the conveying surface, a case where the proportion of protrusions formed by organic particles is 50% or more is recorded as “P”, and a case where the proportion of protrusions formed by organic particles is less than 50% is recorded as “N”.

[0157] Table 1 shows whether the protrusion with the maximum protrusion height Sp among the protrusions present on the transport surface is formed by organic particles. The analysis of whether the particles forming the maximum protrusion height Sp are organic particles was performed on the protrusions of the transport surface as follows: The transport surface of the peeling film was marked with a felt pen, and the maximum protrusion height Sp near the marked area was measured using an optical interferometer (Vertscan R3300G Lite, manufactured by Hitachi High-Technologies Corporation) under the following measurement conditions. Furthermore, when measuring the maximum protrusion height Sp, coarse agglomerated particles larger than 1 μm present on the transport surface were not counted. (Measurement Conditions) • Measurement Mode: WAVE Mode • Objective Lens: 50x • Measurement Area: 186μm × 155μm Next, platinum vapor deposition was performed on the sample. Using a SEM (“S4700”, manufactured by Hitachi High-Technologies Corporation), the area near the markings on the transport surface was photographed at low magnification with the lens tilted at 15° relative to the horizontal plane. Among the protrusions present in the 100μm × 100μm observation area (measurement field of view), protrusions suitable for the maximum protrusion height Sp were selected. Elemental distribution analysis was performed using an EDS analyzer to determine whether the particles forming the protrusions suitable for the maximum protrusion height were organic or inorganic. The method for determining organic and inorganic particles was as described above. In 10 different observation areas on the transport surface of the sample, it was determined whether the particles forming the protrusions representing the maximum protrusion height Sp were organic or inorganic. The case where the ratio of organic particles to the number of particles forming the protrusion representing the maximum protrusion height Sp is 50% or more is defined as "O", and other cases are defined as "I". When the determination result based on the above method is "O", the release film is evaluated as having a transport surface formed by organic particles for the protrusion representing the maximum protrusion height Sp.

[0158] [Table 1] Table 1 Contains a particle layer (convergence surface) Composition particle adhesive thickness [nm] Sp [nm] Organic particles protruding Proportion Sp forming particles Surface E [mJ / m 2 ] Example 1 A1 O1 Polyurethane resin 1 40 42 P O 44 Example 2 A2 O1 Polyurethane resin 2 40 38 P O 55 Example 3 A3 O1 Olefin resin 40 44 P O 43 Example 4 A4 O1 Acrylic resin 1 40 40 P O 33 Example 5 A5 O2 Acrylic resin 1 60 106 P O 33 Example 6 A6 O2 / O4 Acrylic resin 1 40 420 P O 32 Example 7 A7 O3 / I1 Acrylic resin 1 40 352 N O 33 Example 8 A8 O2 / O5 Acrylic resin 1 100 3509 P O 33 Example 9 A1 O1 Polyurethane resin 1 100 twenty one P O 45 Example 10 A1 O1 Polyurethane resin 1 40 41 P O 44 Example 11 A1 O1 Polyurethane resin 1 40 41 P O 44 Example 12 A12 O2 / I1 Acrylic resin 1 40 158 P I 33 Example 13 A13 O3 / I2 Acrylic resin 1 40 348 P O 33 Comparative Example 1 CA1 I1 Polyurethane resin 2 100 111 N I 55 Comparative Example 2 CA2 O2 Polyester resin 100 88 P O 50 Comparative Example 3 CA3 O2 Polyester resin 100 88 P O 50

[0159] [Table 2] Table 1 (Continued) Peeling layer (peeling surface) evaluate Composition thickness [nm] Sp [nm] Sa [nm] Surface E [mJ / m 2 ] Defect evaluation of ceramic layer (High-speed conveying) Defect evaluation of ceramic green chips 1 Defect evaluation of ceramic green chips 2 Peelability high speed Contraction Example 1 L1 100 25 1.0 13 A A A A A Actual example 2 L1 100 twenty five 0.9 12 A B B A A Actual example 3 L1 100 twenty five 0.9 13 A A A A A Actual example 4 L1 100 twenty five 0.9 12 A A A A A Actual example 5 L1 100 twenty five 0.9 13 A A A A A Actual example 6 L1 100 twenty five 0.9 13 A A A A A Actual example 7 L1 100 twenty five 0.9 12 B A A A A Actual example 8 L1 100 twenty five 1.0 13 A B B A A Actual example 9 L1 100 twenty five 1.0 13 A A A A B Actual example 10 L2 500 36 2.1 twenty three A A A A A Actual example 11 L3 500 35 2.8 32 A A A B A Actual example 12 L1 100 twenty five 0.9 12 B A A A A Actual example 13 L1 100 twenty five 0.9 12 A A A A A Comparative Example 1 L2 100 36 1.0 twenty three C B B A A Comparative Example 2 L2 100 36 1.0 twenty three A B C A A Comparative Example 3 L4 100 36 3.0 33 A B C C A

[0160] As shown in Table 1, it was confirmed that when ceramic green sheets were manufactured using the release films of Examples 1-13 of the present invention, the occurrence of defects on the surface of the ceramic layer obtained by calcining the ceramic green sheets during high-speed transport could be suppressed compared to Comparative Example 1. From this result, it is believed that when ceramic green sheets were manufactured using the release films of Examples 1-13, and then multilayer ceramic capacitors were manufactured using the obtained ceramic green sheets, the manufacturing rate of multilayer ceramic capacitors with low electrical characteristics was reduced compared to the case where the release film of Comparative Example 1 was used.

[0161] Furthermore, as shown in Table 1, it was confirmed that in the release films of Examples 1 to 13 of the present invention, even when used in the manufacture of ceramic green sheets after long-term storage, the occurrence of defects in the manufactured ceramic green sheets could be suppressed compared with Comparative Example 2, which contained a particle layer but did not contain non-polyester resin.

[0162] In the release film, it was found that if the maximum protrusion height Sp of the surface containing the particle layer opposite to the polyester substrate is 25 nm or more, the release film has excellent rollability during high-speed transport, and it was found that if the maximum protrusion height Sp is 1000 nm or less, the defect suppression performance of the ceramic green sheet is even better (comparison of Examples 1 to 13).

[0163] It was confirmed that if the surface containing the particle layer on the opposite side of the polyester substrate has protrusions, and among these protrusions, the proportion of protrusions formed by organic particles is 50% to 100%, then the defect suppression performance of the ceramic layer surface during high-speed transport is even better (comparison of Examples 5 to 7). It was confirmed that if the surface containing the particle layer on the opposite side of the polyester substrate has protrusions, and among these protrusions, the protrusion with the largest protrusion height Sp is a protrusion formed by organic particles, then the defect suppression performance of the ceramic layer surface during high-speed transport is even better (comparison of Examples 5 to 6 and 12 to 13).

[0164] It was confirmed that if the surface free energy of the surface of the release layer opposite to the polyester substrate is 30 mJ / m2 or less, the release properties are excellent (comparison of Examples 1 and 10-11). It was confirmed that if the surface free energy of the surface of the particle layer opposite to the polyester substrate is 45 mJ / m2 or less, the defect suppression performance of the ceramic green sheet is even better (comparison of Examples 1-4). [Simplified Explanation of the Diagram]

[0011] FIG1 is a cross-sectional view showing an example of the structure of the peeling film of the present invention.

Claims

1. A release film comprising, sequentially, a release layer, a polyester substrate and a particle-containing layer, wherein the particle-containing layer comprises particles and a non-polyester resin, the particles comprise organic particles, the release layer comprises a polysiloxane compound, and the surface free energy of the surface of the release layer opposite to the polyester substrate is 10 to 30 mJ / m2.

2. The release film as described in claim 1, used for manufacturing ceramic green sheets.

3. The release film as described in claim 1 or claim 2, wherein the aforementioned polyester substrate substantially does not contain particles.

4. The release film as described in claim 1 or claim 2, wherein the surface of the aforementioned particle-containing layer opposite to the aforementioned polyester substrate has protrusions, wherein the proportion of the protrusions formed by organic particles is 50 to 100% in terms of number.

5. The release film as described in claim 1 or claim 2, wherein the surface of the aforementioned particle-containing layer opposite to the aforementioned polyester substrate has protrusions, wherein the protrusion that becomes the maximum protrusion height Sp is a protrusion formed by organic particles.

6. The peeling film as described in claim 1 or claim 2, wherein the maximum protrusion height Sp is 1 to 30 nm.

7. The release film as claimed in claim 1 or claim 2, wherein the aforementioned organic particles comprise at least one selected from the group consisting of styrene resin, polyurethane resin, acrylic resin and divinylbenzene resin.

8. The release film as claimed in claim 1 or claim 2, wherein the surface free energy of the surface of the particle layer opposite to the polyester substrate is 25 to 45 mJ / m2, and the maximum protrusion height Sp is 25 to 1000 nm.

9. The release film as claimed in claim 1 or claim 2, wherein the aforementioned non-polyester resin is selected from at least one resin selected from the group consisting of acrylic resins, polyurethane resins and olefin resins.

10. The release film as described in claim 1 or claim 2, wherein the thickness of the release film is less than 40 μm.

11. The release film as described in claim 1 or claim 2, wherein the thickness of the aforementioned particle-containing layer is 1 to 500 nm.

12. A method for manufacturing a release film, comprising the method of manufacturing the release film according to any one of claims 1 to 11, the method comprising: A process of coating a particle-containing layer-forming composition, which includes organic particles and non-polyester resin, onto a surface of a polyester substrate.

13. A ceramic capacitor manufactured using a release film as described in any one of claims 1 to 11.

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