Release film, method for manufacturing release film, and laminate

Abstract

To provide a release film that does not cause concave imperfections on the release surface and is capable of producing a ceramic green sheet with reduced imperfections, a method for producing the release film, or a laminate including the release film.SOLUTION: A release film includes a polyester substrate, and a release layer disposed on the polyester substrate. The release layer includes a crosslinked body formed by crosslinking a blocked isocyanate with a dissociation temperature of higher than 100°C and 220°C or lower and a composition including non-polyester resin. There are also provided a method for producing the release film, and a laminate including the release film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a release film, a method for manufacturing a release film, and a laminate. [Background technology]

[0002] As electronic devices become more high-performance and smaller, there is a growing demand for higher performance and smaller size in the electronic components used in them. Among electronic components, multilayer ceramic capacitors, for example, are seeing an increase in the number of points they can be mounted on a circuit board, and there is a strong demand for miniaturization. In the manufacturing of multilayer ceramic capacitors, it is common to include a step of applying a ceramic slurry onto the release layer of a release film and drying it to form a ceramic green sheet.

[0003] Patent Document 1 describes a laminated polyester film characterized by having a coating layer on at least one side of a polyester film, formed from a coating solution containing a crosslinking agent and a release agent, and further containing other polymers in an amount of 30% by weight or less as nonvolatile components. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-030378 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In a release film comprising a substrate and a release layer placed on the substrate, minute concave defects (hereinafter also referred to as concave defects) may occur on the release surface, which is the surface to which the ceramic slurry is applied. These defects on the release surface may be transferred, resulting in minute defects on the ceramic green sheet.

[0006] This disclosure has been made in view of these circumstances, and one embodiment of this disclosure aims to solve the problem of producing a ceramic green sheet in which no concave defects occur on the peel surface and minute defects are suppressed. Another embodiment of the present disclosure aims to solve the problem of providing a laminate including the above-mentioned release film. Furthermore, another embodiment of this disclosure aims to solve the problem of providing a method for manufacturing a release film that can produce a ceramic green sheet in which no concave defects occur on the release surface and in which defects are suppressed. [Means for solving the problem]

[0007] The means for solving the above problems include the following embodiments. <1> It comprises a polyester substrate and a release layer, A release film comprising a crosslinked body formed by crosslinking a composition containing a blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less, and a non-polyester resin, wherein the release layer described above includes a crosslinked body. <2> The above-mentioned blocked isocyanate is a compound in which, at temperatures lower than the above-mentioned dissociation temperature in the DSC curve obtained by differential scanning calorimetry, the temperature at which it exhibits a heat flow value of 1 / 3 of the heat flow value at the above-mentioned dissociation temperature is 80°C or higher. <1> The release film described above. <3> The blocking agent in the above-mentioned blocked isocyanate is an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound. <1> or <2> The release film described above. <4> The above composition contains a silicone compound. <1> ~ <3> The release film described in any one of the following. <5> It comprises a polyester substrate and a release layer, A release film in which the above-mentioned release layer contains a crosslinked isocyanate and a non-polyester resin, and a compound containing residues derived from an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound. <6> For the manufacture of ceramic green sheets, <1> ~ <5> The release film described in any one of the following. <7> The above polyester substrate is substantially particle-free. <1> ~ <6> The release film described in any one of the following. <8> The above non-polyester resin is at least one resin selected from the group consisting of urethane resin, acrylic resin, polyvinyl alcohol resin, olefin resin, and silicone resin. <1> ~ <7> The release film described in any one of the following. <9> The thickness of the above-mentioned peeling layer is 0.001 μm to 0.2 μm. <1> ~ <8> The release film described in any one of the following. <10> It further contains a particle-containing layer, The above release layer, the above polyester substrate, and the above particle-containing layer are included in this order. <1> ~ <9> The release film described in any one of the following. <11> The above particle-containing layer contains a non-polyester resin. <10> The release film described above. <12> The above non-polyester resin is at least one resin selected from the group consisting of acrylic resin, urethane resin, and olefin resin. <10> or <11> The release film described above.

[0008] <13> A method for manufacturing a release film comprising a polyester substrate and a release layer, A method for producing a release film, comprising the step of forming a release layer using a release layer-forming composition containing a blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less, and a non-polyester resin. <14> The step of forming the above-mentioned release layer is a step of applying the above-mentioned release layer forming composition to one side of an unstretched polyester film or a uniaxially stretched polyester film to form a release layer. <13> A method for manufacturing the release film described above. <15> <1> ~ <12> A laminate comprising a release film described in any one of the above, and a layer containing ceramic. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, there is provided a release film capable of manufacturing a ceramic green sheet in which concave defects do not occur on the release surface and defects are suppressed. According to another embodiment of the present disclosure, there is provided a laminate including the release film. Further, according to another embodiment of the present disclosure, there is provided a method for manufacturing a release film capable of manufacturing a ceramic green sheet in which concave defects do not occur on the release surface and defects are suppressed.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the release film, the method for manufacturing the release film, and the laminate of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0011] In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In this specification, the amount of each component in the composition means the total amount of a plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In this specification, the term "step" includes not only an independent step but also a step included in this term if the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In this specification, the "longitudinal direction" means the long direction of the release film during the manufacture of the release film, and is synonymous with the "transport direction" and the "machine direction". In this specification, the "width direction" means a direction perpendicular to the longitudinal direction. In this specification, "orthogonal" is not limited to strict orthogonality and includes approximate orthogonality. "Approximate orthogonality" means intersecting within a range of 90° ± 5°, preferably intersecting within a range of 90° ± 3°, and more preferably intersecting within a range of 90° ± 1°. Also, in this specification, the "film width" means the distance between both ends in the width direction of the release film.

[0013] In this specification, the weight average molecular weight (Mw) means a value measured by gel permeation chromatography (GPC). When the molecular weight is 1000 or less, the molecular weight is calculated based on the types and numbers of atoms constituting the compound. The measurement by GPC is performed using HLC (registered trademark)-8020GPC (Tosoh Corporation) as the measurement device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, Tosoh Corporation) columns, and THF (tetrahydrofuran) as the eluent. The measurement conditions are a sample concentration of 0.45 mass%, a flow rate of 0.35 ml / min, a sample injection volume of 10 μL, and a measurement temperature of 40°C, and it is performed using a RI detector. The calibration curve is prepared from eight samples of "Standard Sample TSK standard, polystyrene" of Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0014] In this specification, unless otherwise specified, when simply referring to "the release film of the present disclosure", it shall describe both the first embodiment and the second embodiment described below.

[0015] 〔Release Film〕 The release film of the first embodiment of the present disclosure includes a polyester base material and a release layer, and the release layer includes a crosslinked body formed by crosslinking a composition containing a blocked isocyanate having a dissociation temperature exceeding 100°C and not exceeding 220°C and a non-polyester resin.

[0016] The release film of the second embodiment of the present disclosure comprises a polyester substrate and a release layer, the release layer containing a compound comprising a crosslinked isocyanate and a non-polyester resin, and residues derived from an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound.

[0017] Release films, which include a polyester substrate and a release layer, may develop minute concave defects (i.e., concave defects) on the release surface. The cause of these concave defects on the release surface is not clear, but the inventors of this invention hypothesize the following. In the manufacturing process of release films containing a polyester substrate and a release layer, the composition used to obtain the crosslinked material in the release layer may be heated to around 100°C during stretching of the polyester substrate and formation of the release layer. Therefore, if the composition for obtaining the crosslinked material contains a blocked isocyanate compound with a dissociation temperature of 100°C or lower, the blocking agent will detach due to the heating, and the crosslinking reaction will proceed. If the polyester substrate is stretched after heating, the areas where the crosslinking reaction has progressed due to heating may not be able to follow the stretching, and cracks (i.e., fissures) may occur on the release surface, which is considered to be the cause of concave defects on the release surface. In fields that require a high level of surface smoothness on the release surface, such as in the manufacture of ceramic green sheets where even minute defects affect capacitor performance, concave defects on the release surface may be unacceptable. For example, in the case of release films for the manufacture of ceramic green sheets, concave defects on the release surface may be transferred, causing defects (mainly minute convex defects) in the manufactured ceramic green sheets.

[0018] On the other hand, in the release film of the first embodiment of this disclosure, the release layer includes a crosslinked body obtained by crosslinking a composition containing a blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, and a non-polyester resin. This crosslinked body is obtained by the detachment of the blocking agent of the blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, and by crosslinking with the non-polyester resin contained in the above composition. In this way, by using a blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, and a non-polyester resin in the composition for obtaining the crosslinked body contained in the release layer, even if such a composition is heated to about 100°C during the manufacturing process of the release film, the detachment of the blocking agent can be suppressed, and the crosslinking reaction can be made less likely to proceed. As a result, it is presumed that the occurrence of concave defects caused by cracks occurring on the release surface as described above can be suppressed. Furthermore, it is presumed that defects in the ceramic green sheet can be suppressed by manufacturing a ceramic green sheet using the release film of the first embodiment of this disclosure which does not have concave defects on the release surface.

[0019] Furthermore, in the release film of the second embodiment of this disclosure, the release layer contains a compound comprising a crosslinked isocyanate and a non-polyester resin, and residues derived from an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound. The compound comprising residues derived from an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound contained in the release layer coexists with the crosslinked isocyanate and a non-polyester resin, and from the structure of the residues contained within the molecule (i.e., residues derived from an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound), it is inferred that all of them are derived from blocked isocyanates with a dissociation temperature exceeding 100°C. In other words, it is inferred that the release film of the second embodiment of this disclosure contains a crosslinked compound formed by crosslinking a composition comprising a blocked isocyanate with a dissociation temperature exceeding 100°C and a non-polyester resin. For this reason, it is inferred that the release film of the second embodiment of this disclosure can suppress the occurrence of concave defects on the release surface for the same reasons as the release film of the first embodiment of this disclosure. Furthermore, it is presumed that defects in the ceramic green sheet can be suppressed by manufacturing the ceramic green sheet using the release film of the second embodiment of this disclosure, which does not have minute concave defects on the release surface.

[0020] In contrast, Patent Document 1 describes the use of blocked isocyanates with a dissociation temperature of 100°C or less, and does not describe blocked isocyanates protected with a blocking agent containing an oxime group, a pyrazole group, or an amide group.

[0021] <Polyester base material> The release film of this disclosure includes a polyester substrate. A polyester substrate is a film-like object containing polyester resin as its main polymer component. Here, "main polymer component" refers to the polymer that is present in the largest quantity (by mass) of all polymers contained in the film-like object. The polyester substrate may contain one type of polyester resin, or it may contain two or more types of polyester resins.

[0022] [Polyester resin] Polyester resins are polymers having ester bonds in their main chain. Polyester resins are usually formed by polycondensation of dicarboxylic acid compounds and diol compounds, as described later. In this disclosure, "main chain" means the relatively longest bonding chain in the polymer compound that constitutes the resin. The polyester resin is not particularly limited, and known polyester resins can be used. Examples of polyester resins include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), and copolymers thereof. Among these, at least one selected from the group consisting of PET, PEN, and copolymers thereof is preferred, with PET being more preferred.

[0023] The intrinsic viscosity of the polyester resin is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g. The melting point (Tm) of the polyester resin is preferably 220°C to 270°C, and more preferably 245°C to 265°C. The glass transition temperature (Tg) of the polyester resin is preferably 65°C to 90°C, and more preferably 70°C to 85°C.

[0024] The method for producing polyester resin is not particularly limited, and known methods can be used. For example, polyester resin can be produced by polycondensation of at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst. The following describes the materials used in the manufacture of polyester and the manufacturing conditions.

[0025] (Dicarboxylic acid compounds) Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, as well as dicarboxylic acid esters such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. Among these, aromatic dicarboxylic acids or methyl aromatic dicarboxylic acids are preferred.

[0026] Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, dimer acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid. Examples of alicyclic dicarboxylic acid compounds include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

[0027] Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfisoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, and 9,9'-bis(4-carboxyphenyl)fluorenic acid, as well as their methyl esters. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred, with terephthalic acid being more preferred.

[0028] Dicarboxylic acid compounds may be used individually or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or in combination with other aromatic dicarboxylic acids such as isophthalic acid, or with aliphatic dicarboxylic acids.

[0029] (Diol compounds) Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

[0030] Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred. Examples of alicyclic diol compounds include cyclohexanedimethanol, spiroglycol, and isosorbide. Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. Diol compounds may be used individually or in combination of two or more.

[0031] (catalyst) The catalyst used in the production of polyester resin is not particularly limited, and any known catalyst usable for the synthesis of polyester resin can be used. Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds are preferred from the viewpoint of catalytic activity and cost. The catalyst may be used alone or in combination of two or more. Preferably, the catalyst is a combination of 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, and a phosphorus compound; more preferably, a combination of a titanium compound and a phosphorus compound is used.

[0032] As the titanium compound, organic chelate titanium complexes are preferred. Organic chelate titanium complexes are titanium compounds that have an organic acid as a ligand. Examples of organic acids include citric acid, lactic acid, trimellitic acid, and malic acid. As a titanium compound, the titanium compounds described in paragraphs

[0049] to

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

[0033] (Terminal encapsulant) In the manufacture of polyester resin, end encapsulants may be used as needed. By using end encapsulants, structures derived from the end encapsulant are introduced to the ends of the polyester resin. The end-captive agent is not limited, and known end-captive agents can be used. Examples of end-captive agents include oxazoline compounds, carbodiimide compounds, and epoxy compounds. As end-capturing agents, refer to the contents described in paragraphs

[0055] to

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

[0034] (Manufacturing conditions) The reaction temperature when manufacturing polyester resin is not limited and can be set appropriately depending on the raw materials. The reaction temperature is preferably 260°C to 300°C, and more preferably 275°C to 285°C. The pressure used when manufacturing polyester resin is not limited and should be set appropriately according to the raw materials. The pressure is 1.33 × 10⁻⁶. -3 ~1.33 × 10 -5 MPa is preferred, 6.67 × 10 -4 ~6.67×10 -5 MPa is more preferable.

[0035] As a method for producing polyester resin (for example, a synthesis method), the method described in paragraphs

[0033] to

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

[0036] [Content of each ingredient] The polyester resin content in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polymer in the polyester substrate. There is no particular upper limit to the polyester resin content, and it can be appropriately set within a range of, for example, 100% by mass or less relative to the total mass of the polymer in the polyester substrate. When the polyester substrate contains polyethylene terephthalate, the polyethylene terephthalate content is preferably 90% to 100% by mass, more preferably 95% to 100% by mass, even more preferably 98% to 100% by mass, and particularly preferably 100% by mass, based on the total mass of polyester resin in the polyester substrate.

[0037] The polyester substrate may contain components other than polyester resin (for example, catalysts, unreacted raw material components, particles, water, etc.).

[0038] From the viewpoint of improving the smoothness of the release film, it is preferable that the polyester substrate is substantially free of particles. Examples of particles include those contained in the particle-containing layer described later. In this specification, "substantially particle-free" means that, when quantitative analysis of elements derived from particles is performed on the polyester substrate by X-ray fluorescence analysis, the particle content is 50 ppm by mass or less relative to the total mass of the polyester substrate, preferably 10 ppm by mass or less, and more preferably below the detection limit. This is because even without actively adding particles to the polyester substrate, contaminants derived from foreign substances, raw resins, or dirt adhering to the lines or equipment in the manufacturing process of the polyester substrate may detach and become mixed into the polyester substrate.

[0039] [Properties of polyester substrates] (Orientation) The polyester base material is preferably a biaxially oriented polyester base material. "Biaxially oriented" means having molecular orientation in two axial directions. The molecular orientation is measured using a microwave transmission type molecular orientation meter (for example, MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The angle formed by the two axial directions is preferably within the range of 90° ± 5°, more preferably within the range of 90° ± 3°, and even more preferably within the range of 90° ± 1°. The biaxially oriented polyester base material in the release film of the present disclosure preferably has molecular orientation in the longitudinal direction and the width direction. The biaxially oriented polyester base material can be manufactured by the method described later (specifically, the stretching process).

[0040] (Density) The density of the polyester base material is 1.39 g / cm 3 ~1.41 g / cm 3 is preferable, and 1.395 g / cm 3 ~1.405 g / cm 3 is more preferable, and 1.398 g / cm 3 ~1.400 g / cm 3 is even more preferable. The density of the polyester base material can be measured using an electronic specific gravity meter (product name "SD-200L", manufactured by Alpha Mirage Co., Ltd.).

[0041] (Thickness) The thickness of the polyester base material is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less in terms of controlling the peelability. The lower limit of the thickness is not particularly limited, but in terms of improving strength and workability, it is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. The thickness of the polyester base material is the arithmetic average value of the thicknesses of five locations of the above-mentioned section, which is measured by preparing a section having a cross-section perpendicular to the main surface of the release film and using a scanning electron microscope (SEM: Scanning Electron Microscope) or a transmission electron microscope (TEM: Transmission Electron Microscope).

[0042] <Release layer> The release layer is provided to allow the release film to be peeled off. When a release film is used to manufacture a ceramic green sheet, the ceramic green sheet is formed on the release surface, which is the surface opposite to the polyester substrate of the release layer. That is, the ceramic green sheet is provided in a removable manner on the release surface of the release film. The release layer may be provided directly on the surface of the polyester substrate, or it may be provided on the polyester substrate via another layer, but it is preferable to provide it directly on the surface of the polyester substrate in terms of superior smoothness.

[0043] The release layer includes a crosslinked body formed by crosslinking a composition containing a blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less, and a non-polyester resin. Hereinafter, the blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less will also be referred to as the "specific blocked isocyanate," and the composition containing the blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less, and a non-polyester resin will also be referred to as the "composition for forming the release layer." In particular, the release layer is preferably formed by crosslinking a composition containing a blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, and a non-polyester resin.

[0044] [Specific Blocked Isocyanates] The specific blocked isocyanate has a dissociation temperature between 100°C and 220°C. The specific blocked isocyanate is a compound used as a crosslinking agent. Using the specific blocked isocyanate can suppress the formation of concave defects on the delamination surface. In this specification, the dissociation temperature of a blocked isocyanate means "the temperature of the endothermic peak in the DSC curve obtained by differential scanning calorimetry (DSC), which is associated with the deprotection reaction of the blocked isocyanate (i.e., the reaction in which the blocking agent is removed from the isocyanate group)." Examples of differential scanning calorimeters used for differential scanning calorimetry include, but are not limited to, the Seiko Instruments Inc. model DSC6200.

[0045] From the viewpoint of producing a ceramic green sheet with suppressed defects and without causing concave defects on the peeled surface, the dissociation temperature of the specific block isocyanate is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher. Furthermore, the dissociation temperature of the specific block isocyanate is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower, from the viewpoint of ease of manufacturing the crosslinked material contained in the release layer.

[0046] The specified block isocyanate is preferably a compound in which the temperature at which the heat flow value (hereinafter also referred to as temperature X) is 80°C or higher, when the DSC curve obtained by differential scanning calorimetry shows a heat flow value of 1 / 3 of the heat flow value at the dissociation temperature, on the lower side of the dissociation temperature. A specified block isocyanate having such physical properties means that the blocking agent is less likely to desorb on the lower side of the dissociation temperature. If the above temperature X is below 80°C, the endothermic peak associated with the deprotection reaction of the block isocyanate is often broad, and the blocking agent desorbs on the lower side of the dissociation temperature compared to when the above temperature X is 80°C or higher. Therefore, by using a compound in which the above temperature X is 80°C or higher as the specified block isocyanate, the progress of the crosslinking reaction on the lower side of the dissociation temperature can be suppressed, and the occurrence of concave defects on the delamination surface can be more effectively suppressed. As a result, a ceramic green sheet with suppressed defects can be manufactured.

[0047] A specific blocked isocyanate is a compound in which the isocyanate group of a polyisocyanate is protected (i.e., blocked) with a blocking agent, and there are no particular restrictions as long as the dissociation temperature is in the range of over 100°C and 220°C or less. The dissociation temperature of a specific blocked isocyanate is mainly determined by the type of blocking agent.

[0048] (Blocking agent) Examples of blocking agents in specific blocked isocyanates include phenol compounds, alcohol compounds, oxime compounds, mercaptan compounds, lactam compounds, amine compounds, acid amide compounds, pyrazole compounds, triazole compounds, and bisulfite compounds.

[0049] Examples of phenolic compounds include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, and ethylphenol. Examples of alcohol compounds include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, propylene glycol monomethyl ether, ethylene glycol, and benzyl alcohol. Examples of oxime compounds include acetoxime, methyl ethyl ketone oxime, acetaldehyde, formaldehyde, diacetyl monooxime, and cyclohexane oxime. Among these, acetoxime and methyl ethyl ketone oxime are preferred from the viewpoint of ease of synthesis and adjustment of dissociation temperature.

[0050] Examples of mercaptan compounds include butyl mercaptan and dodecyl mercaptan. Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam. Among these, ε-caprolactam is preferred from the viewpoint of ease of synthesis and control of dissociation temperature. Examples of amine compounds include diphenylaniline, aniline, and ethyleneimine. Examples of acid amide compounds include acetanilide and acetic acid amide. Examples of pyrazole compounds include methylpyrazole (e.g., 2-methylpyrazole, 3-methylpyrazole, 4-methylpyrazole), dimethylpyrazole (e.g., 2,4-dimethylpyrazole, 2,5-dimethylpyrazole, 3,4-dimethylpyrazole, 3,5-dimethylpyrazole), 4-nitro-3,5-dimethylpyrazole, and 4-bromo-3,5-dimethylpyrazole. Among these, methylpyrazole and dimethylpyrazole are preferred from the viewpoint of ease of synthesis and adjustment of dissociation temperature. Examples of triazole compounds include 1,2,4-triazole.

[0051] In particular, the blocking agent in a specific blocked isocyanate is preferably an oxime compound, a lactam compound, an acid amide compound, or a pyrazole compound, from the viewpoint of setting the dissociation temperature of the blocked isocyanate to over 100°C and 220°C or less.

[0052] (Polyisocyanate) Examples of polyisocyanates whose isocyanate groups are protected by a blocking agent include polyfunctional polyisocyanates having the form of an adduct (also called an adduct) obtained by adding 3 moles of diisocyanate to 1 mole of trimethylolpropane, a burette (also called a burette) obtained by reacting 3 moles of diisocyanate with 1 mole of water, or an isocyanurate (also called an isocyanurate) obtained by polymerization of 3 moles of diisocyanate. The polyisocyanate whose isocyanate groups are protected by a blocking agent may also be a polyurethane polyisocyanate obtained by reacting a polyisocyanate with a polyol (e.g., polyester polyol, polyether polyol, low molecular weight polyol). Examples of diisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic isocyanates. However, from the viewpoint of producing a ceramic green sheet with suppressed defects and without causing concave defects on the peeled surface, aliphatic diisocyanates are preferred, and among them, hexamethylene diisocyanate is preferred.

[0053] Examples of diisocyanates include aromatic diisocyanates such as 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyle diisocyanate, tetraalkyldiphenylmethane diisocyanate, dialkyldiphenylmethane diisocyanate, 1,3-phenylenediisocyanate, polymeric diphenylmethane diisocyanate, tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate), 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,5-naphthylene diisocyanate, and naphthalene diisocyanate.

[0054] Examples of aliphatic diisocyanates include hexamethylene diisocyanate, trimethylene diisocyanate, trimethylhexamethylene diisocyanate (2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate), lysine diisocyanate, xylylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and 1,5-pentamethylene diisocyanate.

[0055] Examples of diisocyanates include alicyclic isocyanates such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,3- or 1,4-cyclohexane diisocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, methylcyclohexane diisocyanate (-2,4- or -2,6-methylcyclohexane diisocyanate), and norbornane diisocyanate.

[0056] In particular, from the viewpoint of ease of availability, ease of synthesis, and the ability to produce ceramic green sheets with suppressed defects without creating concave defects on the peeled surface, isocyanurate, burette, and adduct forms of hexamethylene diisocyanate are preferred.

[0057] Specific examples of specific blocked isocyanates include compounds in which the isocyanurate of hexamethylene diisocyanate is blocked with an oxime compound, lactam compound, acid amide compound, or pyrazole compound; compounds in which the isocyanate of the biuret of hexamethylene diisocyanate is blocked with an oxime compound, lactam compound, acid amide compound, or pyrazole compound; and compounds in which the isocyanate of the adduct of hexamethylene diisocyanate is blocked with an oxime compound, lactam compound, acid amide compound, or pyrazole compound.

[0058] Commercially available products may be used as the specific blocked isocyanate. Examples of commercially available products include the Coronate series from Tosoh Corporation (2554, 2507, BI-301), the Duranate series from Asahi Kasei Corporation (SBN-70D, SBN-70P, MF-B60B, 17B-60P, TPA-B80E, E402-B80B), and the Takenate series from Mitsui Chemicals, Inc. (B-830, B-815N, B-820NSU, B-842N, B-846N, B870N, B874N, B882N).

[0059] In the composition for forming the release layer, there may be only one specific block isocyanate, or there may be two or more.

[0060] In the release layer forming composition, the content of specific blocked isocyanates may be 1% to 90% by mass, preferably 5% to 35% by mass, relative to the total solid content of the release layer forming composition, and more preferably 10% to 25% by mass, from the viewpoint of excellent release properties and the production of a ceramic green sheet with suppressed defects that do not cause concave defects on the release surface. Here, total solid content refers to the total mass excluding the solvent contained in the release layer forming composition.

[0061] In the release layer forming composition, the content ratio of the specific blocked isocyanate to the non-polyester resin is preferably 0.01 to 1, and more preferably 0.1 to 1 in terms of excellent solvent resistance.

[0062] [Non-polyester resin] The release layer forming composition contains a non-polyester resin. Non-polyester resins refer to resins other than polyester resins. Specifically, non-polyester resins include at least one selected from the group consisting of urethane resins, olefin resins, fluororesins, alkyd resins, acrylic resins, polyester resins, polyvinyl alcohol resins, melamine resins, epoxy resins, phenolic resins, styrene-butadiene copolymers, and silicone resins.

[0063] As the non-polyester resin, a non-polyester resin having a functional group that can crosslink with an isocyanate group (hereinafter also referred to as functional group R) is preferred. When the release layer-forming layer composition contains a non-polyester resin having functional group R, a crosslinked product is obtained through a crosslinking reaction with a specific blocked isocyanate, improving solvent resistance. Examples of functional groups R found in non-polyester resins include hydroxyl groups, carboxyl groups, amino groups, thiol groups, and amide groups. Among these, hydroxyl groups and carboxyl groups are preferred from the viewpoint of availability and crosslinkability with specific blocked isocyanates.

[0064] From the viewpoint of suppressing defects in ceramic green sheets, the non-polyester resin is preferably at least one selected from the group consisting of urethane resin, acrylic resin, polyvinyl alcohol resin, olefin resin, and silicone resin. In particular, the non-polyester resin is preferably at least one selected from the group consisting of urethane resin having a functional group R, acrylic resin having a functional group R, polyvinyl alcohol resin, olefin resin having a functional group R, and silicone resin having a functional group R.

[0065] The urethane resin is not particularly limited as long as it is a polymer having urethane bonds in its main chain, and known urethane resins such as reaction products of polyisocyanates and polyols can be used. As described above, the urethane resin is preferably a urethane resin having a functional group R, and more preferably a urethane resin having a carboxyl group. The solvent resistance of urethane resin can be improved by adjusting the crosslinking reaction with oxazoline compounds, for example, by adjusting the structure and flexibility of the polyol and polyisocyanate used as raw materials. For superior solvent resistance, it is preferable that the urethane resin contains a polyester structure. Examples of commercially available urethane resins include Hydran® AP-20, AP-40N, and AP-201 (all manufactured by DIC Corporation), Takelac® W-605, W-5030, and W-5920 (all manufactured by Mitsui Chemicals, Inc.), Superflex® 210 and 130, and Elastron® H-3-DF, E-37, and H-15 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0066] Acrylic resin is a resin containing constituent units derived from (meth)acrylate, and may be copolymerized with vinyl monomers such as styrene. As mentioned above, the acrylic resin is preferably an acrylic resin having a functional group R. The acrylic resin is not particularly limited, but it is preferable that it contains structural units derived from (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and more preferably that it contains structural units derived from (meth)acrylate having an alkyl group having 1 to 8 carbon atoms. The acrylic resin may contain an acid-modified component. The acrylic resin may contain a structural unit derived from (meth)acrylic acid as the acid-modified component. By containing a structural unit derived from (meth)acrylic acid, a carboxyl group as a functional group R is introduced into the acrylic resin. Furthermore, the (meth)acrylic acid may form an acid anhydride or be neutralized with at least one selected from alkali metals, organic amines, and ammonia. The acid value of the acrylic resin is preferably 30 mg KOH / g or less, and more preferably 20 mg KOH / g or less. The lower limit of the acid value is not particularly limited, for example, 0 mg KOH / g, but from the point of application as an aqueous dispersion, 2 mg KOH / g or more is preferred. By setting the acid value of the acrylic resin within the above range and / or including constituent units derived from (meth)acrylate having alkyl groups with 1 to 12 carbon atoms, a resin that is poorly compatible with polyester resin can be made. By making the resin poorly compatible with the polyester resin of the polyester substrate, the precipitation of impurities such as oligomers contained in the polyester substrate into the release layer can be suppressed, and as a result, defects in the ceramic green sheet can be further suppressed.

[0067] Polyvinyl alcohol resin is a resin that contains constituent units derived from vinyl alcohol in its main chain and has a hydroxyl group as a functional group R. Polyvinyl alcohol resin may also have a group other than a hydroxyl group as a functional group R, such as a carboxyl group. Polyvinyl alcohol resin may be copolymerized with vinyl alcohol or vinyl acetate, among other monomers. Examples of monomers that may be copolymerized with vinyl alcohol include vinyl acetate and vinyl butyral. The polyvinyl alcohol resin may be partially saponified or fully saponified. Specifically, the degree of saponification of the polyvinyl alcohol resin is preferably 80 to 100, and more preferably 90 to 100.

[0068] The olefin resin can be any resin that contains structural units derived from olefins in its main chain. By having structural units derived from olefins in its main chain, the crosslinking reaction with oxazoline compounds can be controlled, and solvent resistance can be improved. As described above, the olefin resin is preferably an olefin resin having a functional group R. The olefin is not particularly limited, but alkenes having 2 to 6 carbon atoms are preferred, ethylene, propylene, or hexene are more preferred, and ethylene is even more preferred. The olefin-derived structural units in the polyolefin are preferably 50 mol% to 99 mol%, and more preferably 60 mol% to 98 mol%, relative to all structural units of the polyolefin.

[0069] As the olefin resin, acid-modified olefin resins are preferred, and carboxy-modified olefin resins are 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.

[0070] Examples of commercially available olefin resins include the Zaichsen® series (manufactured by Sumitomo Seika Co., Ltd.), such as Zaichsen AC, A, L, NC, and N; the Chemipearl® series (manufactured by Mitsui Chemicals, Inc.), such as Chemipearl S100, S120, S200, S300, S650, and SA100; and the Hi-Tec® series (manufactured by Toho Chemicals, Inc.), such as Hi-Tec S3121 and S3148K. Examples include the Arrowbase (registered trademark) series (manufactured by Unitika Ltd.), such as Arrowbase SE-1013, SE-1010, SB-1200, SD-1200, SD-1200, DA-1010 and DB-4010; Hardlen AP-2, NZ-1004 and NZ-1005 (manufactured by Toyobo Co., Ltd.); and Sepolsion G315 and VA407 (manufactured by Sumitomo Seika Co., Ltd.). Furthermore, the acid-modified olefin resin described in paragraphs

[0022] to

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

[0071] Silicone resin refers to a silicone compound with a weight-average molecular weight of 1000 or more, which has a silicone structure (a main chain consisting of polysiloxane bonds) within its molecule. The silicone resin is preferably a compound having a dimethylsiloxane structure. Alternatively, the silicone resin may be an organic-inorganic composite resin formed by a compound of an inorganic component consisting of polysiloxane and an organic component. In this case, it is preferable that the silicone resin contains a structural unit having a functional group R and a structural unit having dimethylsiloxane, and more preferably a structural unit having a carboxyl group and a structural unit having dimethylsiloxane. Furthermore, the silicone resin is preferably a compound in which a functional group R is introduced into at least one of the terminal and side chains of the main chain consisting of polysiloxane bonds. When using silicone resin as a non-polyester resin, the silicone resin can serve as both a non-polyester resin and a silicone compound.

[0072] In the release layer forming composition, there may be only one type of non-polyester resin, or there may be two or more types.

[0073] In the release layer forming composition, the content of non-polyester resin may be 10% to 99% by mass, preferably 25% to 80% by mass, relative to the total solid content of the release layer forming composition. From the viewpoint of excellent release properties and the production of a ceramic green sheet with suppressed defects that do not cause concave defects on the release surface, it is preferably 30% to 65% by mass.

[0074] Furthermore, the content ratio of the specific blocked isocyanate to the non-polyester resin in the release layer forming composition may be 0.01 to 1, but from the viewpoint of excellent release properties and the production of a ceramic green sheet with suppressed defects that do not cause minute concave defects on the release surface, it is preferably 0.1 to 0.5.

[0075] [Silicone compounds] The release layer-forming composition preferably contains a silicone compound. The presence of a silicone compound results in a release layer with excellent release properties.

[0076] The silicone compound is not particularly limited as long as it is a compound having a siloxane bond in its molecule. The silicone compound is preferably a compound having a dimethylsiloxane structure because it exhibits superior release properties. The silicone compound may be a low molecular weight compound or an oligomer, and is preferably an oligomer.

[0077] The molecular weight of the silicone compound is preferably 150 or higher, more preferably 350 or higher, and even more preferably 650 or higher. The upper limit of the molecular weight of the silicone compound is less than 1000.

[0078] In particular, crosslinkable silicone compounds are preferred as silicone compounds because they have superior solvent resistance. The component that the silicone compound crosslinks may be a specific blocked isocyanate or a component included in other release layer forming compositions. Furthermore, it is preferable that the crosslinkable portion is introduced to at least one of the terminal and side chains of the silicone compound.

[0079] Examples of silicone compounds include polydimethylsiloxane and hydrodienesiloxane, which have a vinyl group introduced to at least one of their terminal and side chains. These silicone compounds exhibit superior solvent resistance because crosslinked products are obtained by reacting them with a platinum catalyst. Examples of silicone compounds include polydimethylsiloxanes having hydroxyl groups at their ends and polydimethylsiloxanes having hydrogen atoms at their ends. These silicone compounds exhibit superior solvent resistance because crosslinked products are obtained by condensation reactions using organotin catalysts. Furthermore, the silicone compound may be a silicone compound that can be crosslinked by ultraviolet light or electron beams. Examples of silicone compounds that can be crosslinked by ultraviolet light or electron beams include radical polymerizable silicone compounds and silicone compounds having epoxy groups, and more specifically, acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane.

[0080] In particular, from the viewpoint of crosslinkability with specific block isocyanates, the silicone compound is more preferably a silicone compound having a functional group that can crosslink with isocyanate groups. More specifically, the silicone compound is more preferably a functional group that can crosslink with isocyanate groups at least one of the terminal and side chains of the silicone compound.

[0081] Functional groups that can crosslink with the isocyanate group of a silicone compound include, for example, the same functional groups R found in non-polyester resins. In particular, from the viewpoint of availability and crosslinkability with specific blocked isocyanates, the functional group R of the silicone compound is preferably a hydroxyl group and a carboxyl group. That is, the silicone compound is preferably a silicone compound having a hydroxyl group and a silicone compound having a carboxyl group.

[0082] The composition for forming the release layer may contain only one silicone compound, or two or more.

[0083] In the release layer forming composition, the content of the silicone compound is preferably 1% to 90% by mass, and more preferably 5% by mass or more, based on the total solid content of the release layer forming composition.

[0084] [Preferred conditions] In the release film of this disclosure, it is preferable that the release layer forming composition satisfies at least one of the following conditions (1) to (3). (1) Contains a specific blocked isocyanate and a non-polyester resin having a functional group R other than a silicone resin, and further contains a silicone compound. (2) The material contains a specific block isocyanate and a non-polyester resin, wherein the non-polyester resin is a silicone resin having a functional group R. (3) Contains a specific blocked isocyanate and a non-polyester resin having a functional group R other than a silicone resin, and further contains a silicone resin. In the cases of conditions (1) and (3), the specific blocked isocyanate reacts with at least a non-polyester resin having a functional group R other than a silicone resin to obtain a crosslinked product. Furthermore, the release properties of the release layer are obtained by the silicone compound or silicone resin. In the case of condition (1), the silicone compound and silicone resin do not necessarily have a functional group R, but it is preferable that they have a functional group R from the viewpoint of solvent resistance. In the case of condition (2), the specific blocked isocyanate reacts with at least a silicone resin having a functional group R to obtain a crosslinked product. In the case of condition (2), the release layer forming composition may further contain a silicone compound. The silicone compound in this case does not have to have a functional group R, but it is preferable that it has a functional group R from the viewpoint of solvent resistance.

[0085] [Additives] The composition for forming the release layer may contain additives in addition to the above components. Examples of additives include surfactants, light release additives and heavy release additives for adjusting the release force, adhesion enhancers, antistatic agents, and catalysts for promoting the crosslinking reaction.

[0086] From the viewpoint of improving the smoothness of the peeling layer, the composition for forming the peeling layer preferably contains a surfactant. The surfactant is not particularly limited, and examples include silicone-based surfactants, fluorine-based surfactants, and hydrocarbon-based surfactants. Among these, hydrocarbon-based surfactants are preferred.

[0087] The silicone-based surfactant is not particularly limited as long as it is a surfactant having a silicon-containing group as a hydrophobic group, and examples include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Examples of commercially available silicone-based surfactants include BYK(registered trademark)-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, and BYK-349 (all manufactured by BYK), as well as KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0088] The fluorine-based surfactant is not particularly limited as long as it is a surfactant having a fluorine-containing group as a hydrophobic group, and examples include perfluorooctanesulfonic acid and perfluorocarboxylic acid. Examples of commercially available fluorine-based surfactants include Megafac® F-114, F-410, F-440, F-447, F-553, and F-556 (all manufactured by DIC Corporation), and Surflon® S-211, S-221, S-231, S-233, S-241, S-242, S-243, S-420, S-661, S-651, and S-386 (manufactured by AGC Seimi Chemical Co., Ltd.). Furthermore, as a fluorine-based surfactant, from the viewpoint of improving environmental suitability, it is preferable to use a surfactant derived from a substitute material for a compound having a linear perfluoroalkyl group with 7 or more carbon atoms, such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

[0089] Examples of hydrocarbon-based surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include alkyl sulfates, alkylbenzene sulfons, alkyl phosphates, and fatty acid salts. Examples of nonionic surfactants include polyalkylene glycol mono- or dialkyl ethers, polyalkylene glycol mono- or dialkyl esters, and polyalkylene glycol monoalkyl esters / monoalkyl ethers. Examples of cationic surfactants include primary to tertiary alkylamine salts and quaternary ammonium compounds. Examples of amphoteric surfactants include surfactants that have both anionic and cationic sites within their molecule.

[0090] Examples of commercially available anionic surfactants include Rapizole® A-90, A-80, BW-30, B-90, and C-70 (all manufactured by NOF Corporation), Nikkol® OTP-100 (all manufactured by Nikko Chemical Co., Ltd.), Kohacool® ON, L-40, and Phosphanol® 702 (all manufactured by Toho Chemical Industry Co., Ltd.), and Viewlight® A-5000 and SSS (all manufactured by Sanyo Chemical Industries, Ltd.). Examples of commercially available nonionic surfactants include Naroacty® CL-95 and HN-100 (product name: manufactured by Sanyo Chemical Industries, Ltd.), Risolex BW400 (product name: manufactured by Kofu Alcohol Industry Co., Ltd.), EMALEX® ET-2020 (all manufactured by Nippon Emulsion Co., Ltd.), and Surfinol® 104E, 420, 440, 465, and Dynol® 604, 607 (all manufactured by Nisshin Chemical Industry Co., Ltd.).

[0091] Among hydrocarbon-based surfactants, anionic surfactants and / or nonionic surfactants are preferred, and anionic surfactants are more preferred.

[0092] Anionic hydrocarbon surfactants are preferable to have multiple hydrophobic end groups in that they have improved smoothness. The hydrophobic end groups may be some of the hydrocarbon groups that the hydrocarbon surfactant has. For example, a hydrocarbon surfactant having a branched-chain hydrocarbon group at its end will have multiple hydrophobic end groups. Examples of anionic hydrocarbon surfactants having multiple hydrophobic end groups include sodium di-2-ethylhexyl sulfosuccinate (having four hydrophobic end groups), sodium di-2-ethyloctyl sulfosuccinate (having four hydrophobic end groups), and branched-chain alkylbenzene sulfonates (having two hydrophobic end groups).

[0093] One type of surfactant may be used, or two or more types may be used in combination. If the composition for forming the release layer contains a surfactant, the surfactant content is preferably 0.1% to 10% by mass relative to the total solid content of the composition for forming the release layer, more preferably 0.1% to 5% by mass, and even more preferably 0.5% to 2% by mass, from the viewpoint of further improving the smoothness of the release layer.

[0094] Furthermore, the composition for forming the release layer may also contain other crosslinking agents other than the specific blocked isocyanate as additives. Other crosslinking agents are not particularly limited and known ones can be used. Other crosslinking agents include, for example, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and oxazoline compounds. For details on the melamine compound, epoxy compound, and isocyanate compound, refer to sections

[0081] to

[0083] of Japanese Patent Publication No. 2015-163457. For carbodiimide compounds, refer to the descriptions in paragraphs

[0038] to

[0040] of Japanese Patent Publication No. 2017-087421. For carbodiimide compounds and isocyanate compounds, refer to sections

[0074] to

[0075] of International Publication No. 2018 / 034294. For oxazoline compounds, refer to sections

[0111] to

[0117] of Japanese Patent Publication No. 2013-058746 and sections

[0038] to

[0048] of Japanese Patent Publication No. 2015-160434. For other crosslinking agents, see sections

[0082] to

[0084] of International Publication No. 2017 / 169844.

[0095] If the release layer forming composition contains other crosslinking agents, the content of the other crosslinking agents is preferably 0% to 30% by mass relative to the total solid content of the release layer forming composition.

[0096] [Content of each ingredient] The content of the crosslinked material (specifically, a crosslinked material of isocyanate and non-polyester resin) in the release layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the release layer. The upper limit of the crosslinking agent content can be set as appropriate, within a range of less than 100% by mass of the total mass of the release layer.

[0097] The exfoliated layer contains compounds that include residues derived from the blocking agent of the blocked isocyanate (for example, compounds that include residues derived from oxime compounds, pyrazole compounds, acid amide compounds, or lactam compounds). The content of compounds containing residues derived from the blocking agent of the blocked isocyanate in the exfoliation layer is preferably 0.0001% to 1% by mass, and more preferably 0.0001% to 0.5% by mass, relative to the total mass of the exfoliation layer.

[0098] (Compounds containing residues derived from blocking agents) Compounds containing residues derived from blocking agents are often at least one selected from compounds that are blocking agents for blocking isocyanates, their derivatives, and their degradation products. Specifically, compounds containing residues derived from oxime compounds are often at least one selected from oxime compounds, their derivatives, and their degradation products; compounds containing residues derived from pyrazole compounds are often at least one selected from pyrazole compounds, their derivatives, and their degradation products; compounds containing residues derived from acid amide compounds are often at least one selected from acid amide compounds, their derivatives, and their degradation products; and compounds containing residues derived from lactam compounds are often at least one selected from lactam compounds, their derivatives, and their degradation products.

[0099] [Properties of the release layer] (Thickness) The thickness of the release layer can be set according to its intended use and is not particularly limited, but 0.001 μm to 0.2 μm is preferred, 0.01 μm to 0.2 μm is more preferred, and 0.03 μm to 0.1 μm is even more preferred, as it provides a good balance between release performance and smoothness of the release surface. The thickness of the release layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM), and taking the arithmetic mean of the thicknesses of these sections.

[0100] <Particle-containing layer> The release film of this disclosure preferably further comprises a particle-containing layer, and more preferably comprises the release layer, polyester substrate, and particle-containing layer in this order.

[0101] A particle-containing layer refers to a layer that contains particles. The presence of a particle-containing layer in the release film improves its transportability. Specifically, it improves the winding quality of the release film (suppresses blocking), reduces the occurrence of scratches and defects during transport, and reduces transport wrinkles during high-speed transport.

[0102] The particle-containing layer may be provided directly on the surface of the polyester substrate, or it may be provided on the surface of the polyester substrate via another layer, but it is preferable to provide it directly on the surface of the polyester substrate in terms of superior adhesion.

[0103] Furthermore, the particle-containing layer preferably contains particles and a binder, and may also contain additives.

[0104] The following describes the particles, binder, and additives.

[0105] (particle) The average particle size of the particles contained in the particle-containing layer is not particularly limited, but is preferably 10 nm to 2 μm, more preferably 30 nm to 1.5 μm, and even more preferably 30 nm to 500 nm, in terms of superior transportability and suppression of transfer marks. Furthermore, in terms of superior transportability and suppression of transfer marks, it is preferable that the average particle diameter of the particles contained in the particle-containing layer is 10 nm to 200 nm (more preferably 30 nm to 130 nm), the thickness of the particle-containing layer is 1 nm to 200 nm (more preferably 10 nm to 100 nm), and the average particle diameter of the particles is greater than the thickness of the particle-containing layer.

[0106] The particles contained in the particle-containing layer may be one type alone, or two or more types of particles may be used. When the particle-containing layer contains two or more particles with different particle sizes, it is preferable that the particle-containing layer contains at least one particle whose average particle size is within the above range, and it is more preferable that all two or more particles with different particle sizes have an average particle size within the above range.

[0107] Examples of particles included in the particle-containing layer include organic particles and inorganic particles. Among these, organic particles are preferred from the viewpoint of suppressing the defect rate of ceramic capacitors manufactured using the obtained ceramic green sheet when the ceramic green sheet is manufactured. As organic particles, resin particles are preferred. Examples of resins constituting the resin particles include acrylic resins such as polymethyl methacrylate (PMMA), polyester resins, silicone resins, styrene resins, and styrene-acrylic resins. The resin particles may have a crosslinked structure. Examples of resin particles having a crosslinked structure include divinylbenzene crosslinked particles. In this disclosure, "acrylic resin" means a resin containing constituent units derived from acrylate or methacrylate. Examples of inorganic particles include silica particles (also called silicon dioxide particles), titania particles (also called titanium oxide particles), calcium carbonate, barium sulfate, and alumina particles (also called aluminum oxide particles). Among these, silica particles are preferred as the inorganic particles from the viewpoint of further improving haze and durability.

[0108] The shape of the particles is not particularly limited and can be, for example, rice grain-shaped, spherical, cubic, spindle-shaped, flaky, aggregated, or irregular. Aggregated means a state in which primary particles are aggregated. The shape of the aggregated particles is not limited, but spherical or irregular shapes are preferred.

[0109] As the aggregated particles, fumed silica particles are preferred. A commercially available example is the Aerosil series manufactured by Nippon Aerosil Co., Ltd. Colloidal silica particles are preferred as non-aggregated particles. Examples of commercially available products include the Snowtex® series manufactured by Nissan Chemical Corporation.

[0110] From the viewpoint of transportability and suppression of transfer marks, the particle content in the particle-containing layer is preferably 0.1% to 30% by mass, more preferably 1% to 25% by mass, and even more preferably 1% to 15% by mass, relative to the total mass of the particle-containing layer. Furthermore, the particle content is preferably 0.0001% to 0.01% by mass, and more preferably 0.0005% to 0.005% by mass, relative to the total mass of the release film.

[0111] (Non-polyester resin (binder)) The particle-containing layer preferably contains a non-polyester resin. The non-polyester resin contained in the particle-containing layer functions as a binder.

[0112] Non-polyester resins refer to resins other than polyester resins. Specifically, non-polyester resins are preferably at least one selected from the group consisting of acrylic resins, urethane resins, olefin resins, polyvinyl alcohol resins, and acrylonitrile butadiene resins, and are preferably at least one selected from the group consisting of acrylic resins, urethane resins, and olefin resins, in order to obtain superior effects from this disclosure.

[0113] Here, the solubility parameters (SP values) of non-polyester resins (especially acrylic resins, urethane resins, and olefin resins) and polyester resins are far apart. In other words, the compatibility between acrylic resins, urethane resins, and olefin resins and polyester resins is insufficient, so impurities such as oligomers are less likely to precipitate from the polyester substrate through the particle-containing layer onto the transport surface. As a result, it is presumed that protrusions caused by impurities contained in the polyester substrate are less likely to form on the transport surface.

[0114] The non-polyester resins mentioned above, such as acrylic resins, urethane resins, and olefin resins, are not particularly limited, and known resins can be used. The non-polyester resin is preferably an acid-modified resin, i.e., an acid group-containing resin. Furthermore, the particle-containing layer may also contain polyester resin.

[0115] The acrylic resin is the same as the acrylic resin listed as an example of a non-polyester resin contained in the above-mentioned release layer forming composition, and the preferred embodiment is also the same.

[0116] The olefin resin is the same as the olefin resin listed as an example of a non-polyester resin contained in the above-mentioned release layer forming composition, and the preferred embodiment is also the same. Olefin resins, by having structural units derived from olefins in their main chain, can be made less compatible with polyester resins. This suppresses the precipitation of impurities such as oligomers contained in the polyester substrate into the particle-containing layer, thereby suppressing defects in ceramic green sheets.

[0117] The urethane resin is the same as the urethane resin listed as an example of a non-polyester resin contained in the above-mentioned release layer forming composition, and the preferred embodiment is also the same. In terms of ease of film formation by coating, the urethane resin is preferably a urethane resin having an acidic group, or a form containing a urethane resin and a dispersant. Examples of acidic groups include carboxyl groups. For example, by adjusting the structure and hydrophobicity (hydrophilicity) of the polyol and isocyanate used as raw materials, the urethane resin can be made less compatible with polyester resin. This suppresses the precipitation of impurities such as oligomers contained in the polyester substrate into the particle-containing layer, thereby suppressing defects in the ceramic green sheet. It is preferable that the urethane resin contains a polyester structure in order to further improve defect suppression.

[0118] The non-polyester resin contained in the particle-containing layer may have a cross-linked structure. In other words, the particle-containing layer may be a cross-linked film. To form a non-polyester resin having a crosslinked structure, one method is to form a particle-containing layer using a particle-containing layer-forming composition containing a crosslinking agent, as described later.

[0119] The particle-containing layer may contain one type of binder or two or more types of binders. Furthermore, the particle-containing layer may contain one type of non-polyester resin or two or more types of non-polyester resins. From the viewpoint of suppressing defects, the binder (preferably a non-polyester resin) content is preferably 30% to 99.8% by mass, and more preferably 50% to 99.5% by mass, relative to the total mass of the particle-containing layer.

[0120] (Additives) The particle-containing layer may contain additives other than the above-mentioned particles and binder. Examples of additives included in the particle-containing layer include surfactants, waxes, antioxidants, UV absorbers, colorants, strengthening agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and mold inhibitors.

[0121] The particle-containing layer preferably contains a surfactant, as this improves the smoothness of areas on the transport surface other than those where protrusions formed by the particles exist. The surfactant is not particularly limited, but the same surfactants as those listed as examples of surfactants contained in the above-mentioned peeling layer forming composition can be used.

[0122] One type of surfactant may be used, or two or more types may be used in combination. If the particle-containing layer contains a surfactant, the surfactant content is preferably 0.1% to 10% by mass relative to the total mass of the particle-containing layer, more preferably 0.1% to 5% by mass, and even more preferably 0.5% to 2% by mass, in terms of superior surface smoothness.

[0123] The wax is not particularly limited and may be either natural or synthetic. Examples of natural waxes include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, the lubricants described in

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

[0124] [Properties of the particle-containing layer] (Thickness) When a particle-containing layer is formed, for example, by coating a composition containing particles and a non-polyester resin onto one surface of a polyester film, the thickness of the particle-containing layer is often 1 μm or less. Furthermore, when a polyester film with a particle-containing layer is formed by co-extrusion molding, the thickness of the particle-containing layer is often between 1 μm and 10 μm. The thickness of the particle-containing layer is preferably 1 nm to 3 μm. When manufactured by coating, from the viewpoint of manufacturability and haze reduction, it is preferably 1 nm to 500 nm, more preferably 1 nm to 250 nm, even more preferably 10 nm to 100 nm, and particularly preferably 20 nm to 100 nm. The thickness of the particle-containing layer is determined by preparing a section of the release film with a cross-section perpendicular to the main surface, and measuring the thickness at five points on the section using a scanning electron microscope (SEM) or transmission electron microscope (TEM), and taking the arithmetic mean of the thicknesses of these sections.

[0125] <Properties of release film> [thickness] The thickness of the release film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less, in terms of superior release properties. Furthermore, the thickness of the release film is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, in terms of improved strength and processability. The thickness of the release film shall be measured using a continuous stylus-type film thickness gauge. Specifically, measurements shall be taken at five arbitrary locations on the release film that differ in position. The arithmetic mean of the measurements obtained from these five locations shall be taken as the thickness of the release film.

[0126] [Method for manufacturing release film] A method for manufacturing the release film described herein will be explained. The method for manufacturing the release film described herein is not particularly limited as long as the above-described release film is obtained, and known methods can be used.

[0127] For example, the method for manufacturing a release film according to the present disclosure is a method for manufacturing a release film comprising a polyester substrate and a release layer, and includes the step of forming a release layer using a release layer forming composition containing a blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, and a non-polyester resin.

[0128] In particular, a preferred method for manufacturing release films, in terms of being able to produce release films with high productivity, is: An extrusion molding process to form an unstretched polyester film by extrusion molding, The stretching process includes a first stretching step of stretching an unstretched polyester film in either the conveying direction or the width direction to form a uniaxially stretched polyester film, and a second stretching step of stretching the uniaxially stretched polyester film in the other direction of the conveying direction and the width direction to form a biaxially stretched polyester film, which are performed either in stages or simultaneously. A manufacturing method is provided which includes a release layer forming step, performed between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, in which a release layer forming composition is applied to one side of the polyester film to form a release layer.

[0129] The above manufacturing method yields a release film comprising a polyester substrate and a release layer disposed on the polyester substrate. In other words, it is preferable that the polyester substrate in the release film is obtained by stretching an unstretched polyester film in both the transport direction and the width direction.

[0130] Furthermore, the method for manufacturing the release film of this disclosure may further include a particle-containing layer forming step, which involves applying a particle-containing layer forming composition to the other side of the polyester film between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, to form a particle-containing layer.

[0131] The above manufacturing method yields a release film comprising a polyester substrate, a release layer disposed on one surface of the polyester substrate, and a particle-containing layer disposed on the surface of the polyester substrate opposite to the side on which the release layer is located.

[0132] The following describes each step in a preferred embodiment of the manufacturing method of the present disclosure. However, the manufacturing method of the present disclosure is not limited to this preferred embodiment, and the following steps may be omitted as appropriate.

[0133] [Extrusion molding process] The extrusion molding process is a process in which an unstretched polyester film is formed by extrusion molding. More specifically, this process involves extruding a molten resin containing the raw polyester resin into a film to form an unstretched polyester film. The raw polyester resin is the same as the polyester resin described in the (Polyester Resin) section above. Furthermore, in order to produce a polyester film that is substantially free of particles, it is preferable to use particle-free polyester pellets during the extrusion molding process.

[0134] Extrusion molding is a method of molding raw material resin into a desired shape by, for example, using an extruder to push out a molten raw material resin. The molten material extruded from the extrusion die is formed into a film by cooling. For example, the molten material can be formed into a film by bringing it into contact with a casting roll and cooling and solidifying it on the casting roll. In cooling the molten material, it is preferable to further apply air (preferably cold air) to the molten material.

[0135] [Stretching process] The stretching process is a process that involves performing, either in stages or simultaneously, a first stretching process in which an unstretched polyester film is stretched in either the conveying direction or the width direction to form a uniaxially stretched polyester film, and a second stretching process in which the uniaxially stretched polyester film is stretched in the other direction (conveying direction or width direction) to form a biaxially stretched polyester film. One of the first and second stretching steps is a longitudinal stretching step in which the polyester film is stretched in the transport direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first and second stretching steps is a transverse stretching step in which the polyester film is stretched in the width direction (hereinafter also referred to as "transverse stretching"). During stretching, the polyester polymers are arranged in each respective direction.

[0136] The stretching process described above may be simultaneous biaxial stretching, in which longitudinal stretching and transverse stretching are performed at the same time, or it may be sequential biaxial stretching, in which longitudinal stretching and transverse stretching are performed in stages. Examples of sequential biaxial stretching include stretching in the order of longitudinal stretching followed by transverse stretching; stretching in the order of longitudinal stretching, transverse stretching, and longitudinal stretching; and stretching in the order of longitudinal stretching, longitudinal stretching, and transverse stretching. Among these, the sequential biaxial stretching method in which the stretching is performed in the order of longitudinal stretching followed by transverse stretching is preferred. The following describes a method in which the stretching is performed in the order of longitudinal stretching followed by transverse stretching, but the above manufacturing method is not limited to this method.

[0137] The stretching ratio in the longitudinal stretching process is set as appropriate, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 4.0 times. The stretching speed in the longitudinal stretching process is preferably 800% / second to 1500% / second, more preferably 1000% / second to 1400% / second, and even more preferably 1200% / second to 1400% / second. Here, "stretching speed" is the value obtained by dividing the length Δd of the polyester film stretched in the transport direction per second in the longitudinal stretching process by the length d0 of the polyester film in the transport direction before stretching, expressed as a percentage. In the longitudinal stretching process, it is preferable to heat the unstretched polyester film. This is because heating facilitates longitudinal stretching.

[0138] In the transverse stretching process, it is preferable to preheat the uniaxially stretched polyester film before transverse stretching. Preheating the uniaxially stretched polyester substrate allows for easy transverse stretching. The stretching ratio in the width direction (transverse stretching ratio) of the uniaxially stretched polyester film in the transverse stretching process is not particularly limited, but it is preferably greater than the stretching ratio in the longitudinal stretching process. The stretching ratio in the transverse stretching process is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, and even more preferably 3.5 to 4.5 times. The stretching speed in the transverse stretching process is preferably 8% / second to 45% / second, more preferably 10% / second to 30% / second, and even more preferably 15% / second to 20% / second.

[0139] [Particle-containing layer formation process] The particle-containing layer formation process involves applying a particle-containing layer formation composition to one side of a polyester film to form a particle-containing layer. The particle-containing layer formation step is performed, for example, between the extrusion molding step and the first stretching step, between the first stretching step and the second stretching step, or after the stretching step. In particular, it is preferable that the particle-containing layer formation step is performed between the first stretching step and the second stretching step. The particle-containing layer, which is placed on one surface of the polyester substrate by the particle-containing layer formation process, is the same as the layer described in the section on particle-containing layers above. The following describes embodiments for providing the particle-containing layer-forming composition.

[0140] First, we will describe the composition for forming a particle-containing layer. A composition for forming a particle-containing layer can be prepared by mixing the components described in the section on particle-containing layers and a solvent. Examples of solvents include water and alcohol.

[0141] The particle-containing layer-forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80% to 99.5% by mass, and more preferably 90% to 99% by mass, based on the total mass of the particle-containing layer-forming composition. In other words, in the particle-containing layer-forming composition, the total content of components other than the solvent (solids) is preferably 0.5% to 20% by mass, and more preferably 1% to 10% by mass, relative to the total mass of the particle-containing layer-forming composition.

[0142] With respect to each component other than the solvent in the particle-containing layer-forming composition, it is preferable to adjust the content of each component in the particle-containing layer-forming composition so that the content of each component relative to the total mass of solids in the particle-containing layer-forming composition is the same as the preferred content of each component relative to the total mass of the particle-containing layer.

[0143] Furthermore, the particle-containing layer-forming composition may also contain a crosslinking agent. Examples of crosslinking agents include the above-mentioned specific blocked isocyanates and the above-mentioned other crosslinking agents. The crosslinking agent content is preferably 0% to 50% by mass relative to the total mass of the particle-containing layer. In a particle-containing layer-forming composition, the preferred mass ratio of the crosslinking agent to the binder is 2% to 50% by mass.

[0144] The method for applying the particle-containing layer-forming composition is not particularly limited, and known methods can be used. Examples of application methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating.

[0145] The heating temperature for forming the particle-containing layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0146] Furthermore, in order to improve the adhesion between the polyester film and the particle-containing layer, the surface of the polyester film may be pre-treated with an anchor coat, corona treatment, or plasma treatment before the particle-containing layer is applied.

[0147] [Exfoliation layer formation process] The release layer formation process involves applying a release layer formation composition to one side of a polyester film to form a release layer. The release layer formation process is performed between the extrusion molding process and the first stretching process, between the first stretching process and the second stretching process, or after the stretching process.

[0148] In particular, from the viewpoint of adhesion between the release layer and the polyester substrate, it is preferable that the release layer formation process be carried out between the extrusion molding process and the first stretching process, or between the first stretching process and the second stretching process. In other words, it is preferable that the release layer formation step is a step of applying a release layer formation composition to one side of an unstretched polyester film or a uniaxially stretched polyester film to form a release layer.

[0149] When the peeling layer formation process is performed after the stretching process, it is preferable to perform it after the cooling process described later, and more preferably after the winding process and trimming process described later. The release layer formed on one side of the polyester film during the release layer formation process is the same as the layer described in the section on release layers above.

[0150] First, let's describe the composition for forming the release layer. The composition for forming the release layer preferably contains the components described in the section on the release layer above, as well as a solvent. Examples of solvents include water, alcohols, ethers, ketones, and aromatic hydrocarbons.

[0151] The release layer forming composition may contain one solvent or two or more solvents. The solvent content is preferably 80% to 99.5% by mass, and more preferably 90% to 99% by mass, based on the total mass of the release layer forming composition. In other words, in the release layer forming composition, the total content of components other than the solvent (solids) is preferably 0.5% to 20% by mass, and more preferably 1% to 10% by mass, based on the total mass of the release layer forming composition.

[0152] With respect to each component other than the solvent in the release layer forming composition, it is preferable to adjust the content of each component in the release layer forming composition so that the content of each component relative to the total mass of solids in the release layer forming composition is the same as the preferred content of each component relative to the total mass of the release layer.

[0153] The method for applying the release layer-forming composition is not particularly limited, and known methods can be used. Specific examples of application methods are described in the particle-containing layer formation step.

[0154] The heating temperature for forming the release layer is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited and may be 60°C or higher.

[0155] Furthermore, in order to improve the adhesion between the polyester film and the release layer, pretreatment such as anchor coating, corona treatment, and plasma treatment may be applied to the surface of the polyester film before applying the release layer.

[0156] [Heat setting process] The method for manufacturing the release film according to this disclosure may include a heat-setting step as a heat treatment of the polyester film obtained in the stretching step, after the stretching step. In the heat-setting process, the polyester film obtained in the stretching process can be heated and heat-set. By crystallizing the polyester resin through heat-setting, shrinkage of the polyester substrate can be suppressed. The surface temperature of the polyester film in the heat-setting process (heat-setting temperature) is not particularly limited, but is preferably less than 240°C, more preferably 235°C or less, and even more preferably 230°C or less. The lower limit is not particularly limited, but is preferably 190°C or higher, more preferably 200°C or higher, and even more preferably 210°C or higher. The heating time in the heat setting process is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

[0157] [Thermal relaxation process] The method for manufacturing the release film of this disclosure may include a heat relaxation step after the heat setting step. In the thermal relaxation process, it is preferable to thermally relax the polyester film, which has been thermally fixed in the thermal fixing process, by heating it at a lower temperature than that of the thermal fixing process. Thermal relaxation can alleviate residual strain in the polyester film. In the heat relaxation process, the surface temperature of the polyester film (heat relaxation temperature) is preferably 5°C or more lower than the heat fixing temperature, more preferably 15°C or more lower, even more preferably 25°C or more lower, and particularly preferably 30°C or more lower. That is, the heat relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, even more preferably 210°C or lower, and particularly preferably 200°C or lower. The lower limit of the thermal relaxation temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

[0158] [Cooling process] The method for manufacturing the release film of this disclosure may include a cooling step of cooling the heat-relaxed polyester film. The cooling rate of the polyester film in the cooling process is preferably more than 2000°C / min and less than 4000°C / min, more preferably between 2000°C / min and 3500°C / min, even more preferably more than 2200°C / min and less than 3000°C / min, and particularly preferably between 2300°C / min and 2800°C / min. In the above cooling process, it is also preferable to include a step (expansion step) of expanding the heat-relaxed polyester film in the width direction. The expansion rate in the width direction of the polyester film due to the expansion process, that is, the ratio of the polyester film width at the end of the cooling process to the polyester film width before the start of the cooling process, is preferably 0% or more, more preferably 0.001% or more, and even more preferably 0.01% or more. There is no particular upper limit to the expansion rate, but it is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

[0159] [Winding process] The method for manufacturing the release film of this disclosure may include a winding step to obtain a roll of polyester film by winding up the polyester film obtained through the above steps.

[0160] [Trimming process] The manufacturing method of the present disclosure may include a trimming step, before performing the winding step, in which the polyester film is continuously cut along the transport direction to cut off at least one end of the polyester film in the width direction.

[0161] [Other conditions] The conveying speed of the polyester film in each step of the method for manufacturing the release film of this disclosure, other than the longitudinal stretching step, is not particularly limited, but in the transverse stretching step, heat setting step, heat relaxation step, and cooling step, 50 m / min to 200 m / min is preferred, and 80 m / min to 150 m / min is more preferred in terms of productivity and quality.

[0162] In the method for manufacturing a release film described herein, a method for forming a particle-containing layer is described in which a particle-containing layer is formed by applying a particle-containing layer-forming composition in the particle-containing layer formation step. However, the method for forming the particle-containing layer is not limited to the above embodiment, and known methods can be used. For example, one method is to form an unstretched polyester film with a laminated particle-containing layer by co-extrusion molding.

[0163] In particular, the method for manufacturing the release film of this disclosure is A longitudinal stretching process in which an unstretched polyester film is stretched in the transport direction, A step of forming a particle-containing layer by applying a particle-containing layer-forming composition to one side of a uniaxially stretched polyester film obtained in a longitudinal stretching step, A step of forming a release layer on the other side of a uniaxially stretched polyester film obtained in a longitudinal stretching step, Preferably, the process includes a transverse stretching step in which a uniaxially stretched polyester film having a particle-containing layer and a release layer is stretched in the width direction while being heated.

[0164] [Uses of release film] The release film of this disclosure is preferably a release film (carrier film) used in the manufacture of ceramic green sheets. The ceramic green sheet manufactured using the above release film can be suitably used in the manufacture of ceramic capacitors, where multilayering of internal electrodes is required due to miniaturization and increased capacitance.

[0165] Furthermore, the release film of this disclosure can also be used as a protective film for dry film resists, a film for sheet molding such as decorative layers and resin sheets, a release film for process manufacturing such as semiconductor manufacturing processes, a release film for polarizing plate manufacturing processes, and a separator for adhesive films such as labels, medical and office supplies.

[0166] [Laminate] The laminate of this disclosure comprises the release film of this disclosure and a layer containing ceramic.

[0167] Details of the release film are as described above. The ceramic-containing layer may be provided directly on the surface of the release film, or it may be provided on the release film via another layer, but it is preferable to provide it directly on the surface of the release film in terms of superior smoothness.

[0168] The ceramics included in the ceramic-containing layer are not particularly limited as long as they are ceramics included in the ceramic green sheet. Examples include ferroelectric materials such as barium titanate, and paraelectric materials such as titanium oxide and calcium titanate.

[0169] The ceramic-containing layer preferably contains a binder. The binder is not particularly limited as long as it is a binder contained in the ceramic green sheet, for example, polyvinyl butyral.

[0170] The laminate of this disclosure can be manufactured, for example, by applying a ceramic slurry containing ceramics and a solvent to the release surface of a release film, and drying the solvent contained in the ceramic slurry. Examples of solvents include ethanol and toluene.

[0171] The method for applying the ceramic slurry is not particularly limited, and known methods such as the reverse roll method can be applied.

[0172] Furthermore, a ceramic green sheet can be obtained by peeling off the release film from the laminate of this disclosure. In other words, the layer containing ceramic powder in the laminate of this disclosure becomes the ceramic green sheet. [Examples]

[0173] The present disclosure will be further described with reference to the following examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples may be modified as appropriate, as long as they do not deviate from the spirit of the present disclosure. Accordingly, the scope of the present disclosure is not limited to the following specific examples.

[0174] <Synthesis of blocked isocyanates> -Synthesis Example 1- A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was placed under a nitrogen atmosphere. 600 parts by mass of HDI (hexamethylene diisocyanate) were charged, and the reactor temperature was maintained at 70°C under stirring. Tetramethylammonium caprylate was added as an isocyanuration catalyst, and when the yield reached 40%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate (HDI trimer, isocyanurate of HDI). The obtained polyisocyanate had an isocyanate group concentration of 23.0%, a number-average molecular weight of 670, an average number of isocyanate groups of 3.3, and an unreacted HDI concentration of 0.2% by mass. Using the same apparatus as described above, 100 parts by mass of the obtained polyisocyanate and 50 parts by mass of dipropylene glycol monomethyl ether were charged under a nitrogen atmosphere and mixed at 50°C until a homogeneous solution was formed. Then, 52.7 parts by mass of methoxypolyethylene glycol (number average molecular weight 680, resin hydroxyl value 82 mg KOH / g) was added, and the temperature was raised to 120°C and held for 2 hours. After that, the reaction solution was cooled to 70°C, and 40.2 parts by mass of methyl ethyl ketone oxime was added. After 1 hour, the absence of absorption of the isocyanate group was confirmed by measuring the infrared spectrum of the reaction solution, and a solution containing aqueous blocked isocyanate A was obtained. This solution was adjusted with methanol to a concentration of aqueous blocked isocyanate A of 10% by mass.

[0175] -Synthesis Examples 2 and 3- The procedure was carried out in the same manner as in Synthesis Example 1, except that methyl ethyl ketone oxime was replaced with the blocking agent shown in Table 1, to obtain blocked isocyanates B to C.

[0176] <Example 1> (Extrusion molding process) A titanium compound (titanium citrate chelate complex, VERTEC AC-420, manufactured by Johnson Matthey) described in Japanese Patent No. 5575671 was used as a polymerization catalyst to produce polyethylene terephthalate pellets. The obtained pellets were dried until the moisture content was 50 ppm or less, and then fed into the hopper of a twin-screw compounding extruder. Next, they were melted at 280°C and extruded. The molten material was passed through a filter (pore size 3 μm) and then extruded from the die into a cooling drum at 25°C to obtain a film made of unstretched polyethylene terephthalate (unstretched film). The extruded molten material was then brought into close contact with the cooling drum by electrostatic application.

[0177] (Longitudinal stretching process) Uniaxially stretched polyester film was produced by stretching the above unstretched film in the longitudinal direction (conveying direction) under conditions of 90°C and 3.4 times its original length.

[0178] (Particle-containing layer formation process, peel-off layer formation process) A particle-containing layer-forming composition A1, as shown below, was applied to one side of a uniaxially stretched polyester film using a bar coater. A release layer-forming composition L1, as shown below, was applied to the side of the uniaxially stretched polyester film opposite to the side coated with the particle-containing layer using a bar coater. The formed coating film was dried with hot air at 100°C to form a particle-containing layer and a release layer. In other words, the particle-containing layer-forming composition A1 and the release layer-forming composition L1 were in-line coated onto a uniaxially stretched polyester film. At this time, the amount of particle-containing layer-forming composition A1 and the release layer-forming composition L1 applied was adjusted so that the thickness of the particle-containing layer after transverse stretching, as described later, would be 40 nm and the thickness of the release layer would be 100 nm.

[0179] A polyester film that had undergone longitudinal stretching, particle-containing layer formation, and release layer formation processes was stretched in the width direction using a tenter under the conditions of a stretching temperature of 120°C, a stretching ratio of 4.2 times, and a stretching speed of 50% / second to produce a biaxially stretched polyester film. Next, it was heat-set at 227°C for 6 seconds, and then heat-relaxed by 4% at 190°C. After that, it was cooled at a rate of 2500°C / min, trimmed at both ends of the film, extruded (knurled), and then wound up with a tension of 40 kg / m. The resulting release film had a thickness of 31 μm, a width of 1.5 m, and a winding length of 7000 m.

[0180] [Preparation of composition A1 for forming a particle-containing layer] • Cross-linked PMMA particles (Epostor® MX050W, manufactured by Nippon Shokubai Co., Ltd., average particle size 70 nm, solid content concentration 10% by mass aqueous dispersion) ... 8 parts by mass • Urethane resin B (product name "Hydran (registered trademark) AP-40N", manufactured by DIC Corporation, aqueous dispersion with solid content concentration adjusted to 25% by mass) ... 157 parts by mass • Surfactant B (product name "Rapizol (registered trademark) A-90", sodium di-2-ethylhexyl sulfosuccinate, manufactured by NOF Corporation, solid content concentration 1% by mass, diluted with water) ... 56 parts by mass ·Water…779 parts by mass

[0181] [Preparation of Composition L1 for Forming the Release Layer] • Solution containing aqueous blocked isocyanate A (dissociation temperature 120°C, solid content concentration 10% by mass) ... 60 parts by mass • Silicone compound: Silicone compound A (product name "X-22-3701E", manufactured by Shin-Etsu Chemical Co., Ltd., a silicone compound containing a carboxyl group, 10% by mass diluted with water) ... 96 parts by mass • Non-polyester resin: Urethane resin A (product name "Superflex (registered trademark) 210", manufactured by Daiichi Kogyo Seiyaku Co., Ltd., ester-based urethane aqueous dispersion, solid content concentration 35% by mass adjusted to solid content 25% by mass with water) ... 96 parts by mass • Surfactant A (product name "Naroacty (registered trademark) CL-95", manufactured by Sanyo Chemical Industries, Ltd., nonionic surfactant, 1% by mass aqueous solution) ... 20 parts by mass • Surfactant B (product name "Rapizol (registered trademark) A-90", sodium di-2-ethylhexyl sulfosuccinate, manufactured by NOF Corporation, solid content concentration 1% by mass, diluted with water) ... 20 parts by mass • Distilled water…708 parts

[0182] <Examples 2-15, Comparative Example 1> A release film was prepared in the same manner as in Example 1, except that the type and content (mass%) of each component in the release layer forming composition were changed to those listed in Table 1, and the type of resin in the particle-containing layer forming composition was also changed to those listed in Table 1.

[0183] The details of each component listed in Table 1 are as follows: The crosslinking agents are the blocked isocyanates A to C obtained in the above-mentioned synthesis steps 1 to 3.

[0184] (Silicone compounds) • Silicone compound A: Silicone compound containing a carboxyl group (product name "X-22-3701E", manufactured by Shin-Etsu Chemical Co., Ltd.)

[0185] (Other crosslinking agents) • Oxazoline: Oxazoline crosslinking agent (product name "Epocross (registered trademark) WS-700", manufactured by Nippon Shokubai Co., Ltd.) • Carbodiimide: Carbodiimide crosslinking agent (product name "Carbodilite V-02-L2", manufactured by Nisshinbo Chemical Co., Ltd.)

[0186] (resin) • Urethane resin A: Product name "Superflex (registered trademark) 210", manufactured by Daiichi Kogyo Seiyaku Co., Ltd. • Urethane resin B: Product name "Hydran (registered trademark) AP-40N", manufactured by DIC Corporation. Polyester-based urethane resin formed from urethane resin C: isophorone diisocyanate: terephthalic acid: isophthalic acid: ethylene glycol: diethylene glycol: dimethylolpropanoic acid = 12:19:18:21:25:5 (mol%) • Acrylic resin: A copolymer obtained by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid in a mass ratio of 59:8:26:5:2. • Olefin resin: Product name "Zyxen (registered trademark) NC", manufactured by Sumitomo Seika Co., Ltd. • Polyester resin: Product name "Vaironal (registered trademark) MD-1245", manufactured by Toyobo Co., Ltd. • PVA resin: Product name "Kuraray Poval (registered trademark) PVA-117H", manufactured by Kuraray Co., Ltd. • Silicone resin B: Acrylic silicone composite resin formed by compounding polysiloxane and acrylic resin (product name "Ceranate WSA-1070", manufactured by DIC Corporation, solid content concentration 40% by mass) • Long-chain alkyl compounds: Long-chain alkyl-containing compounds synthesized according to the method described in

[0082] of Japanese Patent Publication No. 2014-151481.

[0187] (Surfactants) • Surfactant A: Product name "Naroacty (registered trademark) CL-95", manufactured by Sanyo Chemical Industries, Ltd. • Surfactant B: Product name "Rapizol (registered trademark) A-90", manufactured by NOF Corporation.

[0188] The prepared release film was used to evaluate the minute concave defects on the release surface, release properties, solvent resistance, and defects in the ceramic green sheet. The evaluation method is as follows.

[0189] <Concave defects on the delamination surface> The release surfaces of the release films prepared in the examples and comparative examples, i.e., the exposed surfaces of the release layer, were observed using an optical microscope at a magnification of 200x to check for the presence and number of extremely minute concave defects (i.e., cracks). The evaluation criteria were as follows. A: No concave defects are observed at all. B: 1 to 9 concave defects are visible. C: Ten or more concave defects, or even if there are fewer than ten, concave defects are observed across the entire observation surface.

[0190] <Removability> 100 parts by mass of barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03") as a ceramic powder, 8 parts by mass of polyvinyl butyral resin (product name "Eslec® B·K BM-2", manufactured by Sekisui Chemical Co., Ltd.) as a binder, 4 parts by mass of dioctyl phthalate (product name "Dioctyl Phthalate Grade 1", manufactured by Kanto Chemical Co., Ltd.) as a plasticizer, and 135 parts by mass of a mixture of toluene and ethanol (mass ratio 6:4) were mixed. The mixture was dispersed using a ball mill in the presence of zirconia beads, and a ceramic slurry was prepared by removing the beads from the resulting dispersion. The release films prepared in the examples and comparative examples were cut to a width of 250 mm and a length of 10 m. The cut release films were stored for one week in a normal temperature and humidity environment (25°C, 50% RH). After storage, the prepared ceramic slurry was coated onto the entire release surface of the release films using a die coater so that the film thickness after drying was 3 μm. The resulting coating was then dried in a dryer at 100°C for 2 minutes. In this way, release films with ceramic green sheets were obtained. A polyester adhesive tape (model number "No. 31B", manufactured by Nitto Denko Corporation) was attached to the surface of the ceramic green sheet in a release film with a ceramic green sheet. After standing at room temperature (25°C) for 24 hours, the release film with the ceramic green sheet was cut to a width of 20 mm to prepare test samples. The adhesive tape side of the test sample was fixed to the surface of a glass plate, and the release film was peeled from the release film with the ceramic green sheet using an A&D Tensilon universal tester under the conditions of a peel angle of 180° and a peel speed of 100 mm / min, and the force required for peeling was measured. The peelability was evaluated based on the force required for peeling. The evaluation criteria are as follows. A: The force required for peeling was 45 mN or less. B: The force required for peeling was between 45 mN and 100 mN. C: The force required for peeling was over 100 mN.

[0191] <Solvent resistance> For the release films prepared in the examples and comparative examples, a cloth soaked in a mixed solution of methyl ethyl ketone and toluene (mass ratio 1:1) was used to apply a load of 1000 g / cm² to the surface of the release layer. 2 The surface was polished five times vertically and five times horizontally. Afterwards, the surface of the peeled layer was visually observed, and the solvent resistance was evaluated based on the dissolution state of the peeled layer. The evaluation criteria are as follows: A: The exfoliated layer has not dissolved at all. B: Part of the peeled layer has dissolved. C: The peeled layer has completely dissolved.

[0192] <Defect Assessment 1> A release film with a ceramic green sheet was obtained using the same method as the method used for evaluating release properties, except that the amount of ceramic slurry applied was adjusted so that the film thickness after drying of the ceramic slurry was 1 μm. After being wound into a roll, a fluorescent lamp was shone from the release film side of the unwound ceramic green sheet release film, and the surface of the ceramic green sheet was measured at 1 μm. 2The area was visually observed to confirm the presence or absence of minute uneven shapes such as pinholes (hereinafter referred to as uneven defects). Based on the number of confirmed defects, the defects were evaluated. The evaluation criteria are as follows. A: No uneven defects were confirmed in the ceramic green sheet. B: One to ten uneven defects were confirmed in the ceramic green sheet. C: Eleven or more uneven defects were confirmed in the ceramic green sheet.

[0193] <Defect Evaluation 2> The release films obtained in each of the examples and comparative examples were stored in a normal temperature and normal humidity environment for three months. Using the release film stored for three months, a release film with a ceramic green sheet was obtained in the same manner as the method described for the evaluation of peelability, except that the coating amount of the ceramic slurry was adjusted so that the film thickness after drying of the ceramic slurry was 1 μm. The obtained release film with a ceramic green sheet was evaluated in the same manner as in Defect Evaluation 1. The evaluation criteria are as follows. A: No uneven defects were confirmed in the ceramic green sheet. B: One to ten uneven defects were confirmed in the ceramic green sheet. C: Eleven or more uneven defects were confirmed in the ceramic green sheet.

[0194] The evaluation results are shown in Table 1. In Table 1, in the column of the release layer, the types and contents (mass%) of each component contained in the composition for forming the release layer are described. The content is the content of the solid component of each component. In the column of the particle-containing layer, the type of resin contained in the composition for forming the particle-containing layer is described. In the silicone compound and non-polyester resin, when it has a functional group capable of crosslinking with an isocyanate group, that is, when it has a functional group R, "Y" is described, and when it does not have a functional group capable of crosslinking with an isocyanate group, "N" is described. In the column of temperature X, the temperature showing a heat flow value one-third of the heat flow value at the dissociation temperature was described for each of the blocked isocyanates A to C, on the lower temperature side than the dissociation temperature of the DSC curve obtained by differential scanning calorimetry.

[0195]

Table 1

[0196] For the release films of Examples 1 to 15, no concave defects were observed on the release surface, and no defects were observed in the produced ceramic green sheet. In addition, regarding the release layers of the release films of Examples 1 to 15, since no dissolution of the release layer was observed in the evaluation of solvent resistance, it was confirmed that a crosslinked body was contained. Further, regarding the release layers of the release films of Examples 1 to 15, by applying pyrolysis gas chromatography / mass spectrometry (pyrolysis GC / MS) and Fourier transform infrared spectroscopy (FT-IR), the presence of a crosslinked body of isocyanate and non-polyester resin was confirmed. Furthermore, regarding the release layers of the release films of Examples 1 to 15, by applying gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) and comparing with standards, it was confirmed that the release layer contained a compound containing residues derived from the blocking agent described in Table 1.

[0197] On the other hand, for the release film of Comparative Example 1, since the composition for forming the release layer contained a blocked isocyanate having a dissociation temperature of 100°C or lower, concave defects were observed on the release surface. In addition, in the laminate (release film with a ceramic green sheet) using the release film of Comparative Example 1, uneven defects were confirmed on the surface of the ceramic green sheet.

[0198] From the comparison of Examples 1, 12, and 13, it was found that when the content of the silicone compound was 5% by mass or more based on the total solid content of the composition for forming the release layer, the releasability was excellent.

[0199] A comparison of Examples 1, 8, and 9 revealed that when the content ratio of a specific blocked isocyanate to the non-polyester resin in the release layer forming composition is 0.1 or higher, it exhibits excellent solvent resistance.

[0200] In Examples 8 and 15, since the particle-containing layer contains a non-polyester resin, it was found that the occurrence of unevenness defects in defect evaluation 2 was suppressed compared to Example 14.

Claims

1. It comprises a polyester substrate and a release layer, The release layer comprises a crosslinked body obtained by crosslinking a composition containing a blocked isocyanate having a dissociation temperature of more than 100°C and 220°C or less, a non-polyester resin, and a silicone compound having a molecular weight of less than 1000. The non-polyester resin is at least one resin selected from the group consisting of urethane resin, acrylic resin, polyvinyl alcohol resin, olefin resin, and silicone resin with a weight-average molecular weight of 1000 or more. A release film in which the content of the silicone compound is 1% by mass to 90% by mass relative to the total solid content of the composition.

2. The release film according to claim 1, wherein the blocked isocyanate is a compound in which the temperature at which the heat flow value is 1 / 3 of the heat flow value at the dissociation temperature is 80°C or higher, on the lower temperature side of the DSC curve obtained by differential scanning calorimetry than the dissociation temperature.

3. The release film according to claim 1 or claim 2, wherein the blocking agent in the blocked isocyanate is an oxime compound, a pyrazole compound, an acid amide compound, or a lactam compound.

4. It comprises a polyester substrate and a release layer, The release layer contains a compound comprising a crosslinked isocyanate and non-polyester resin, an oxime compound, a pyrazole compound, an acid amide compound, or a residue derived from a lactam compound, and a silicone compound with a molecular weight of less than 1000. The non-polyester resin is at least one resin selected from the group consisting of urethane resin, acrylic resin, polyvinyl alcohol resin, olefin resin, and silicone resin with a weight-average molecular weight of 1000 or more. A release film in which the content of the silicone compound is 1% by mass to 90% by mass relative to the mass of the release layer.

5. A release film according to claim 1 or claim 4, for use in manufacturing ceramic green sheets.

6. The release film according to claim 1 or claim 4, wherein the polyester substrate is substantially free of particles.

7. The release film according to claim 1 or claim 4, wherein the thickness of the release layer is 0.001 μm to 0.2 μm.

8. It further contains a particle-containing layer, The release film according to claim 1 or claim 4, comprising the release layer, the polyester substrate, and the particle-containing layer in this order.

9. The release film according to claim 8, wherein the particle-containing layer comprises a non-polyester resin.

10. The release film according to claim 9, wherein the non-polyester resin is at least one resin selected from the group consisting of acrylic resin, urethane resin, and olefin resin.

11. A method for manufacturing a release film comprising a polyester substrate and a release layer, The process includes forming a release layer using a release layer-forming composition containing a blocked isocyanate having a dissociation temperature greater than 100°C and 220°C or less, a non-polyester resin, and a silicone compound with a molecular weight of less than 1000. The non-polyester resin is at least one resin selected from the group consisting of urethane resin, acrylic resin, polyvinyl alcohol resin, olefin resin, and silicone resin with a weight-average molecular weight of 1000 or more. A method for producing a release film, wherein the content of the silicone compound is 1% by mass to 90% by mass relative to the total solid content of the release layer forming composition.

12. The method for manufacturing a release film according to claim 11, wherein the step of forming the release layer is a step of applying the release layer forming composition to one side of an unstretched polyester film or a uniaxially stretched polyester film to form a release layer.

13. A laminate comprising a release film according to claim 1 or claim 4 and a layer containing ceramic.

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