Demolding film

Abstract

Provided is a release film which is capable of reducing the amount of an organic solvent, has good wettability and lightly peelable properties of a thin resin sheet, particularly a thin ceramic green sheet, and has excellent adhesion between a base film and a release layer. The present invention relates to a mold release film having a mold release layer on at least one surface of a polyester film, the mold release layer being a layer formed from an aqueous coating composition, the aqueous coating composition containing a silicone emulsion, the amount of the silicone emulsion being less than or equal to the total weight of the solid content in the aqueous coating composition, and the amount of the silicone emulsion being less than or equal to the total weight of the solid content in the aqueous coating composition. And (c) a resin C containing a silicone having both a Q unit represented by SiO4 / 2 and an alkenyl group in an amount of 20% by mass or more in terms of solid content, the surface elastic modulus of the mold release layer being 20 MPa or more as calculated from a force curve obtained by AFM measurement.

Description

Technical Field

[0001] The present invention relates to a release film comprising a base film and a release layer, and relates to a release film useful as a film for various processes. Background Art

[0002] Conventionally, release films, which have a release layer laminated on a polyester film substrate, have high heat resistance and mechanical properties and are used as process films for forming resin sheets such as adhesive sheets, cover films, ceramic green sheets, and polymer electrolyte membranes. Furthermore, due to their excellent heat resistance and releasability, release layers formed from coating compositions containing silicone have been proposed (e.g., Patent Documents 1 to 5).

[0003] The aforementioned release film is also used as a process film for forming ceramic green sheets that require high smoothness, such as for laminated ceramic capacitors and ceramic substrates. In recent years, with the miniaturization and increased capacity of laminated ceramic capacitors, the thickness of ceramic green sheets has also tended to decrease. Ceramic green sheets are formed by applying a slurry containing a ceramic component such as barium titanate and a binder resin to the release layer of a release film and drying it. The electrode-bearing ceramic green sheets, obtained by printing electrodes on the formed ceramic green sheets and peeling them from the release film, are then stacked, pressed, fired, and coated with external electrodes to produce laminated ceramic capacitors.

[0004] Patent Documents 1 and 2 propose a release film produced by the following method: a coating composition comprising a polysiloxane having an unsaturated group, a polysiloxane having a hydrogen group, a platinum group metal catalyst, and an organic solvent is applied to one side of a biaxially stretched polyester, followed by heat treatment to dry and cure the coating composition to form a release layer (hereinafter referred to as "offline coating").

[0005] Patent Document 3 proposes a release film in which a release layer is formed by applying an aqueous coating composition containing an alkenyl-containing organosilicon and a hydrogen- and phenyl-containing organosilicon to one side of a polyester film and then stretching the polyester film (hereinafter referred to as "in-line coating").

[0006] Patent Document 4 proposes a release film having a release layer formed by off-line coating using a coating composition containing an organosilicon having an aromatic group. Furthermore, Patent Document 5 proposes a release film having a release layer formed by in-line coating using a coating composition containing an organosilicon having a Q unit.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-292894

[0010] Patent Document 2: International Publication No. WO2017 / 200056

[0011] Patent Document 3: Japanese Patent No. 5735278

[0012] Patent Document 4: Japanese Patent No. 5756315

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 2021-11081 Summary of the Invention

[0014] Problems to be solved by the invention

[0015] In recent years, as ceramic green sheets have become thinner, there has been a trend toward requiring release films to have light peeling properties that allow them to be peeled off with a low and uniform force. Furthermore, release films are required to have good wettability to the ceramic slurry applied to the release layer. In order to thin the ceramic green sheets, for example, an organic solvent is required to be used in an amount greater than the amount of resin, and the diluted ceramic slurry with a low solid content concentration is uniformly applied to the release layer. When a ceramic slurry containing such a composition is applied to the release layer, the wettability of the release film to the ceramic slurry sometimes becomes insufficient. Due to slight shrinkage cavities and uneven coating generated during application, there is a concern that pinholes and uneven thickness may be generated on the ceramic green sheets, and there is a concern that the yield of laminated ceramic capacitors may deteriorate.

[0016] Patent Documents 1 and 2, in particular, show insufficient releasability and wettability of thin-layer ceramic green sheets, necessitating a balance between easy releasability and good wettability. Furthermore, the use of coating compositions containing organic solvents as their main component poses concerns about adverse effects on the human body caused by contact with the organic solvent and absorption of vapors, as well as the environmental impact of the release of organic solvent vapors into the atmosphere.

[0017] Furthermore, the drying equipment for organic solvents needs to be explosion-proof, which incurs initial installation costs and requires a large amount of energy for operation, resulting in high CO2 emissions and a heavy environmental impact.

[0018] The release film described in Patent Document 3 forms a release layer by in-line coating, but its application in ceramic green sheet molding was not anticipated, and in particular, it presented challenges in terms of releasability for thin ceramic green sheets. Furthermore, a phenyl-containing crosslinking agent was used to improve the adhesion between the substrate and the release layer, but the effect of the phenyl group on the release strength was not confirmed, making it unsuitable as a release film exhibiting easy releasability.

[0019] The release film described in Patent Document 4 forms a release layer based on a siloxane having an aromatic group and a crosslinking agent. However, in the invention of Patent Document 4, adverse effects on the human body and a high environmental load are issues during the manufacturing process. In addition, due to the presence of bulky substituents such as aromatic groups, the curing reaction of the release layer is difficult to proceed due to steric hindrance. As described in the examples, when the coating composition is cured at 135°C, the curing heat of the release layer becomes insufficient, and there is concern that it will adversely affect the releasability. In order to further cure the release layer, it is necessary to cure the release layer at a higher temperature. However, in the invention of Patent Document 4, there is a concern that thermal deformation of the base film will occur during the manufacturing process, and it is necessary to manufacture at a lower temperature.

[0020] The release film described in Patent Document 5 forms a release layer that exhibits both releasability and wettability through in-line coating. For example, technological development related to thin ceramic green sheets continues to advance, and there is a demand for further improved releasability and adaptability to thin ceramic green sheets compared to the time of the application of Patent Document 5. Furthermore, there is a demand for further improvement in the adhesion of the release layer to the substrate, and for reducing adverse effects such as heavy peeling caused by the release layer falling off the substrate film during the release film manufacturing process or the molding process of resin sheets, such as ceramic green sheets.

[0021] The present invention was completed against the backdrop of the aforementioned problems in the prior art. Specifically, the present invention aims to provide a release film that reduces the use of organic solvents that are harmful to the human body and have adverse effects on the environment, while achieving both easy release properties and good wettability for thin resin sheets, particularly thin ceramic green sheets, and further enhancing the adhesion between the base film and the release layer.

[0022] Solutions for solving problems

[0023] The present inventors have conducted intensive studies to solve the above-mentioned problems and, as a result, have found that the above-mentioned object can be achieved by a release film having the following structure, thereby completing the present invention.

[0024] That is, the present invention is formed by the following configuration.

[0025] [1] A release film comprising a release layer on at least one side of a polyester film,

[0026] The release layer is a layer formed by reacting and solidifying the aqueous coating composition.

[0027] The aforementioned aqueous coating composition comprises a silicone emulsion,

[0028] The silicone emulsion contains 20% by mass or more of (c) resin C in terms of solid content relative to the total weight of the solid content in the aqueous coating composition, wherein the resin C contains SiO4 / 2 The Q unit and alkenyl silicone represented by

[0029] The surface elastic modulus of the release layer calculated from the force curve obtained by measurement using AFM is 20 MPa or more.

[0030] [2] The release film according to [1], wherein

[0031] The silicone emulsion in the aforementioned aqueous coating composition comprises:

[0032] (a) a resin A having an alkenyl group and no aromatic group; and

[0033] (b) Resin B having a hydrogen group and an aromatic group.

[0034] [3] The release film according to [1] or [2], wherein the resin B has a structure represented by Chemical Formula 2 and has a number average molecular weight of 1000 or more and less than 5000.

[0035]

[0036] (In Chemical Formula 2, l is 1 to 50, m is 1 to 50, and n is 0 to 5.)

[0037] [4] The release film according to any one of [1] to [3], wherein the release film is formed as follows:

[0038] The aqueous coating composition is applied to a substrate film before the crystal orientation is completed, stretched in at least one direction, and then heat-treated to complete the crystal orientation of the substrate film.

[0039] [5] The release film according to any one of [1] to [4], wherein the polyester film has a surface layer substantially free of inorganic particles, and the release layer is formed on the surface layer.

[0040] [6] The release film according to any one of [1] to [5], wherein the release film is a release film for producing a laminated ceramic capacitor or a resin sheet.

[0041] Effects of the Invention

[0042] The release film of the present invention can improve the releasability and wettability of the release layer, and can suppress the occurrence of defects in thin resin sheets, particularly ceramic green sheets.

[0043] Furthermore, the harmfulness to human body and the environmental load in the manufacturing process can be reduced.

[0044] A release layer can be formed without worrying about deterioration of the adhesion between the base film and the release layer. DETAILED DESCRIPTION

[0045] The present invention has the features described in this specification, and therefore can further solve the problems described below and achieve the desired effects.

[0046] In particular, it is possible to achieve both easy peelability and good wettability of thin-layer ceramic green sheets. Furthermore, compared to coating compositions containing organic solvents as their main component, the amount of organic solvent can be significantly reduced, or the composition can be substantially free of organic solvents. As a result, the adverse effects on the human body caused by contact with organic solvents and absorption of vapors, as well as the environmental burden caused by the release of organic solvent vapors into the atmosphere, can be significantly reduced.

[0047] Furthermore, since the drying equipment for organic solvents does not need to be explosion-proof, compared to conventional production equipment, energy consumption can be reduced during operation. Consequently, CO2 emissions can be reduced, thus reducing the environmental impact.

[0048] Furthermore, according to the present invention, by using a silicone emulsion containing a silicone resin with a specific structure and composition, a release film with superior releasability compared to release films produced by conventional in-line coating can be provided. In particular, by forming a release layer containing a cured product of a silicone containing Q units, a release film with excellent releasability and wettability can be produced. Furthermore, by forming a release layer containing a cured product of a silicone containing an alkenyl group, the elastic modulus of the release layer is increased, thereby improving releasability. Furthermore, a release film with excellent substrate adhesion can be produced.

[0049] Hereinafter, the present invention will be described in detail.

[0050] The present invention provides a release film having a release layer on at least one side of a polyester film, wherein the release layer is formed by reacting and solidifying an aqueous coating composition, wherein the aqueous coating composition comprises a silicone emulsion. The silicone emulsion comprises 20% by weight or more of (c) a resin C, based on the total weight of the solids in the aqueous coating composition, wherein the resin C comprises SiO 4 / 2 The release film has a surface elastic modulus of 20 MPa or more of the release layer calculated from a force curve measured using an AFM.

[0051] The present invention having such a configuration can achieve both easy releasability and good wettability of the release layer, can provide a thin resin sheet such as a thin ceramic green sheet with a uniform thickness without defects, and can suppress defects such as pinholes.

[0052] Furthermore, the present invention can achieve the following effects: In the present invention, since an aqueous coating composition containing a significantly reduced amount of organic solvent compared to conventional methods or an aqueous coating composition containing substantially no organic solvent is used, the present invention reduces toxicity to the human body and environmental burden, and can produce a release film while suppressing the generation of CO2.

[0053] Furthermore, in one embodiment, the release film of the present invention forms a release layer by applying an aqueous coating composition containing a silicone emulsion having a predetermined composition in an in-line coating process. This allows for a release layer that exhibits both excellent releasability and wettability, as well as excellent substrate adhesion. More specifically, the inclusion of a silicone emulsion containing silicones having Q units allows for a structure in which siloxane bonds are three-dimensionally expanded. This allows for a dense crosslinked structure to be achieved through crosslinking reactions via the alkenyl groups in the silicone molecules having Q units, resulting in a release layer with excellent solvent resistance and easy releasability. Furthermore, the inclusion of Q units reduces the hydrophobicity of the release layer surface, allowing for a release layer with excellent wettability.

[0054] Furthermore, when containing organosilicon containing hydrogen and aryl groups, the aryl groups can be evenly distributed throughout the release layer, rather than being localized, thereby increasing the elastic modulus of the release layer. This increased elastic modulus of the release layer can suppress erosion of the release layer by organic solvents when applying ceramic slurry to the release layer and / or deformation of the release layer during peeling, resulting in a release layer that exhibits easy peelability.

[0055] In addition, when a release layer is formed containing an aromatic group, the adhesion can be improved through the intermolecular interaction between the substrate film and the aromatic group in the release layer. Furthermore, by using a bulky substituent such as an aromatic group, the curing reaction of the release layer can be delayed, and the curing reaction can be prevented from proceeding during the stretching of the substrate film after the coating composition is applied, and the curing reaction can be carried out after the crystal orientation is completed after stretching. By preventing the curing reaction from proceeding during the stretching of the substrate film, the stress generated by the difference in stretchability between the substrate film and the coating composition can be reduced, and a decrease in substrate adhesion can be prevented.

[0056] (Polyester film)

[0057] The polyester constituting the polyester film used as a substrate film is not particularly limited, and a film formed from a polyester commonly used as a substrate for release films can be used. Preferably, it is a crystalline, linear saturated polyester formed from an aromatic dibasic acid component and a glycol component. For example, polyethylene terephthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, polypropylene terephthalate, or copolymers primarily composed of these resins are more preferably preferred. A polyester film formed from polyethylene terephthalate is particularly preferred. In polyethylene terephthalate, the repeating unit content of ethylene terephthalate is preferably 90 mol% or more, more preferably 95 mol% or more. Small amounts of other dicarboxylic acid components or glycol components may also be copolymerized. For example, from a cost perspective, it is preferably produced from only terephthalic acid and ethylene glycol. Furthermore, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizing agents may be added to the release film of the present invention, provided that they do not hinder the effectiveness of the release film. The polyester film is preferably a biaxially oriented polyester film because of reasons such as the high elastic modulus in two directions.

[0058] The intrinsic viscosity of the polyester film is preferably 0.50 dl / g to 0.70 dl / g, more preferably 0.52 dl / g to 0.62 dl / g. An intrinsic viscosity of 0.50 dl / g or higher is preferred because it prevents significant breakage during the stretching process. Conversely, an intrinsic viscosity of 0.70 dl / g or lower is preferred because it provides excellent cuttability when cut to a specified product width and prevents dimensional defects. The raw material pellets are preferably thoroughly vacuum-dried.

[0059] In addition, in this specification, when it is described simply as "polyester film", it may mean the polyester film which has (is laminated with) the surface layer A and the surface layer B.

[0060] The polyester film of the present invention is not particularly limited in its production method, and conventional methods may be used. For example, the polyester film may be produced by melting the polyester in an extruder, extruding the film into a film, cooling the film using a rotating cooling drum to obtain an unstretched film, and then biaxially stretching the unstretched film. Biaxially stretched films may be produced by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in both the longitudinal and transverse directions.

[0061] In the present invention, the stretching temperature during stretching of the polyester film is preferably set to be equal to or higher than the secondary phase transition temperature (Tg) of the polyester. The stretching is preferably performed at a ratio of 1 to 8 times, particularly preferably 2 to 6 times, in both the longitudinal and transverse directions.

[0062] The thickness of the polyester film is preferably 12 μm or more and 50 μm or less, more preferably 15 μm or more and 38 μm or less, and even more preferably 19 μm or more and 33 μm or less. A film thickness of 12 μm or more is preferred because there is no concern about thermal deformation during film production, processing, or molding. On the other hand, a film thickness of 50 μm or less prevents an extreme increase in the amount of film discarded after use, which is preferred for reducing environmental impact.

[0063] The polyester film substrate may be a single layer or a multilayer of two or more layers. For example, the substrate film may be a polyester film having a surface layer A substantially free of particles having a particle size of 1.0 μm or greater and a surface layer B containing particles. Preferably, the surface layer A substantially free of inorganic particles having a particle size of 1.0 μm or greater.

[0064] In this embodiment, particles with a particle size of less than 1.0 μm and 1 nm or larger may be present in the surface layer A. By substantially not containing particles with a particle size of 1.0 μm or larger, such as inorganic particles, the particle shape in the substrate can be transferred to the resin sheet, thereby reducing the occurrence of defects.

[0065] In one embodiment, the surface layer A also does not contain particles having a particle diameter of less than 1.0 μm, thereby more effectively suppressing the transfer of particle shapes in the substrate to the resin sheet and the generation of defects.

[0066] In one embodiment, the polyester film substrate is preferably a laminated film having a surface layer A substantially free of inorganic particles on at least one surface. This can more effectively prevent the particle shape in the substrate from being transferred to the resin sheet and causing problems.

[0067] For example, the surface layer A that does not substantially contain particles having a particle size of less than 1.0 μm is preferably a form that does not substantially contain particles having a particle size of 1.0 μm or more.

[0068] In the present invention, "substantially free of particles" means, for example, that in the case of inorganic particles smaller than 1.0 μm, the content of inorganic elements is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit, when quantified by fluorescent X-ray analysis. This is because, even if particles are not intentionally added to the film, contaminants from foreign matter or stains from production lines and equipment during the raw resin or film manufacturing process may peel off and enter the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or larger" means that particles with a particle size of 1.0 μm or larger are not intentionally contained.

[0069] In the case of a laminated polyester film having a multilayer structure of two or more layers, it is preferred that a surface layer B containing inorganic particles and the like is provided on the opposite side of a surface layer A containing substantially no inorganic particles.

[0070] As laminated structure, if the layer on one side of the coating release layer is set to the A layer, the layer on its opposite side is set to the B layer, the core layer in addition is set to the C layer, then the layer structure in thickness direction can enumerate laminated structures such as release layer / A / B or release layer / A / C / B. Of course, the C layer can also be a multilayer structure. In addition, the surface layer B also can not contain inorganic particles. At this point, in order to give the slippage for film being wound into a roll, it is preferred that a coating comprising at least inorganic particles and a binding agent is provided on the surface layer B.

[0071] In the polyester film substrate of the present invention, from the perspective of film slip and ease of air release, the surface layer B on the surface opposite to the surface to be coated with the release layer preferably contains inorganic particles, particularly preferably silica particles and / or calcium carbonate particles. The content of the inorganic particles contained in the surface layer B is preferably 5000 ppm or more and 15000 ppm or less based on the total amount of the inorganic particles.

[0072] At this moment, the regional surface average roughness (Sa) of the film of surface layer B is preferably the scope of more than 1nm and below 40nm.More preferably the scope of more than 5nm and below 35nm.When silicon dioxide particles and / or calcium carbonate particles amount to more than 5000ppm, Sa is more than 1nm, when film is rolled into roll, air can be made to escape evenly, winding form is good and planarity is good, is thus applicable to the manufacture of ultra-thin layer ceramic green sheet.In addition, when silicon dioxide particles and / or calcium carbonate particles amount to less than 15000ppm, Sa is less than 40nm, is difficult to produce the gathering of lubricant, can't form thick protrusion, therefore stable quality when manufacturing the ceramic green sheet of ultra-thin layer, so preferred.

[0073] As the particles contained in the above-mentioned B layer, in addition to silicon dioxide and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used. From the viewpoint of transparency and cost, silicon dioxide particles and / or calcium carbonate particles are more preferably used. In addition, as other usable inorganic particles, aluminum oxide-silicon dioxide composite oxide particles, hydroxyapatite particles, etc. can be listed. In addition, as heat-resistant organic particles, cross-linked polyacrylic acid particles, cross-linked polystyrene particles, benzoguanamine particles, etc. can be listed. In addition, when using silicon dioxide particles, porous colloidal silica is preferred. When using calcium carbonate particles, from the viewpoint of preventing the lubricant from falling off, light calcium carbonate having been surface-treated with a high molecular compound of a polyacrylic acid system is preferred.

[0074] The average particle size of the inorganic particles added to the surface layer B is preferably 0.1 μm to 2.0 μm, particularly preferably 0.5 μm to 1.0 μm. An average particle size of 0.1 μm or greater is preferred because it improves the slip properties of the release film. An average particle size of 2.0 μm or less is preferred because it minimizes the risk of adversely affecting the surface smoothness of the release layer and, consequently, reduces the risk of pinholes forming in the ceramic green sheet.

[0075] In the surface layer A, which is the layer on the side where the release layer is provided, it is preferred not to use recycled materials or the like in order to prevent the incorporation of inorganic particles such as lubricants from the viewpoint of reducing pinholes.

[0076] The thickness ratio of surface layer A, the layer on the side where the release layer is provided, is preferably 20% to 50% of the total thickness of the base film. A thickness ratio of 20% or greater is preferred because the film is less susceptible to the effects of particles contained in surface layer B and other materials from within, and the regional surface average roughness Sa tends to fall within the above range. A thickness ratio of 50% or less of the total thickness of the base film is preferred because it increases the use of recycled materials in surface layer B, resulting in a lower environmental impact.

[0077] Furthermore, from an economical perspective, layers other than the surface layer A (surface layer B or the intermediate layer C) may contain 50% to 90% by mass of recycled film scraps or plastic bottles. In this case, the type, amount, particle size, and regional surface average roughness (Sa) of the lubricant contained in layer B preferably fall within the above-mentioned ranges.

[0078] In addition, in order to improve the adhesion of the release layer to be applied later, prevent static electricity, etc., a coating can be provided on the surface of the surface layer A and / or the surface layer B before stretching or after uniaxial stretching in the film forming process, or surface treatment can be performed.

[0079] In one embodiment, in order to improve the adhesion with release layer, surface treatment and easy bonding layer can be set on the release layer forming face of coating aqueous coating composition.As surface treatment, plasma treatment, corona discharge treatment, ultraviolet treatment, flame treatment and electron beam / radiation treatment etc. can be listed, and as easy bonding layer, resin containing the same as substrate film can be listed, and then the layer containing antistatic agent, pigment, surfactant, lubricant, antiblocking agent etc. can be listed.In the case of the adhesion improving agent of coupling agent etc. being added in aqueous coating composition, even if easy bonding layer etc. are not set, release layer can also have sufficient adhesion to substrate film.

[0080] (Release layer)

[0081] In the present invention, the release layer is laminated on the surface layer A of the substrate film. The release layer in the present invention is a layer formed by reacting and solidifying an aqueous coating composition, wherein the aqueous coating composition contains an organic silicone emulsion, and the organic silicone emulsion contains 20% by mass or more of (c) resin C in terms of solid content relative to the total weight of the solid content in the aqueous coating composition, wherein the resin C contains SiO 4 / 2 The Q unit and the alkenyl group represented by the silicone.

[0082] By having these characteristics in the release layer, a release film with excellent releasability and wettability can be provided. This prevents the occurrence of defects such as pinholes in resin sheets and ceramic green sheets, and enables the formation of sheets with uniform film thickness. Furthermore, a release layer with excellent substrate adhesion can be provided, preventing the release layer from falling off during the production process of the release film or the production process of the resin sheet or ceramic green sheet.

[0083] Furthermore, the silicone emulsion preferably contains the following substances.

[0084] (a) Resin A, which has an alkenyl group and no aromatic group, preferably has a siloxane structure represented by Structural Formula 1.

[0085]

[0086] (In Structural Formula 1, R1 is an alkenyl group having 2 to 8 carbon atoms, R2 is an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and k is 1 to 50.)

[0087] (b) Resin B contains a hydrogen group and an aromatic group, and preferably has a siloxane bond in the main chain.

[0088] By including the resin A in the release layer, the resin A is easily localized on the surface of the release layer during drying and curing of the coating composition, and the release layer can be provided with excellent releasability.

[0089] Furthermore, by including a resin B containing hydrogen and aromatic groups, preferably a silicone with siloxane bonds in its main chain, in the release layer, the aromatic groups with a rigid molecular skeleton in the release layer are evenly distributed throughout the release layer, rather than being localized, thereby increasing the elastic modulus of the release layer. Furthermore, the interaction between the π electrons of the aromatic groups and the interaction between the C-H bonds and the π electrons of the alkyl groups in the silicone can form a stronger release layer coating. The increased elastic modulus of the release layer, resulting in a stronger coating, can suppress erosion of the release layer caused by organic solvents when applying ceramic slurry to the release layer and / or deformation of the release layer during peeling, resulting in a release layer that exhibits easy peelability.

[0090] The aqueous coating composition of the present invention is a composition comprising a silicone emulsion. The silicone emulsion comprises a resin C and, if necessary, at least one of a resin A, a resin B, and a resin D.

[0091] Silicone emulsions are emulsions made by dispersing these water-insoluble resins in water using a surfactant. The aqueous coating composition may contain one or more silicone emulsions. Furthermore, the silicone emulsion may contain only one selected from Resin A, Resin B, Resin C, and Resin D, two or more, or all of Resin A, Resin B, Resin C, and Resin D in a single silicone emulsion.

[0092] The aqueous coating composition preferably contains substantially no organic solvent and uses water as the dispersion medium. Substantially no organic solvent improves the stability of the silicone emulsion, preventing changes in the composition of the aqueous coating composition due to emulsion breakdown, and preventing aggregation and gelation of the resin in the silicone emulsion.

[0093] Substantially free of organic solvents means, for example, a content of 10,000 ppm or less, preferably 5,000 ppm or less, more preferably 3,000 ppm or less, and most preferably below the detection limit, relative to the total weight of the aqueous coating composition. This is because, even if organic solvents are not intentionally used, small amounts of organic solvents used in the polymerization process of the resin contained in the silicone emulsion or the emulsification process of the emulsion may remain.

[0094] (Resin A)

[0095] The resin A contained in the silicone emulsion preferably has the following structure.

[0096]

[0097] (In Structural Formula 1, R1 is an alkenyl group having 2 to 8 carbon atoms, R2 is an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and k is 1 to 50.)

[0098] By having the structural formula 1, a cross-linking reaction with the organosilicon having a hydrogen group proceeds to form a release layer having a high cross-linking density and excellent solvent resistance, and exhibiting easy releasability.

[0099] Examples of the alkenyl group include vinyl group, allyl group, butenyl group, pentenyl group, and hexenyl group. Among them, vinyl group is particularly preferred.

[0100] As the resin A, for example, the structure represented by the following Chemical Formula 1 can be exemplified.

[0101]

[0102] In Chemical Formula 1, R1 is an alkenyl group having 2 or more and 8 or less carbon atoms, and R2 is an alkyl group having 1 or more and 4 or less carbon atoms, or an alkenyl group having 2 or more and 8 or less carbon atoms. R1 is preferably a vinyl group, and R2 is preferably a methyl group. R2 may be the same or different, for example, R2 at both ends is a methyl group, or it is also preferred that only R2 in the side chain has a vinyl group. k is a structure that contributes to the cross-linking reaction, and is preferably 1 or more and 50 or less. o is a structure that contributes to the stripping property, and is preferably 1 or more and 500 or less. Since k is 1 or more, the cross-linking reaction proceeds, so it is preferred. If it is 50 or less, the unreacted alkenyl group is not easily left in the release layer, and the stripping property is excellent, so it is preferred. If o is 1 or more, stripping property is exhibited, so it is preferred. If it is 500 or less, there is no concern about a decrease in cross-linking density, so it is preferred.

[0103] As shown in Chemical Formula 1, from the viewpoint of exfoliation, it is preferred that the SiO 2 / 2 Generally speaking, the siloxane bonds of silicones formed from D units tend to have a helical structure. For example, in the case of polydimethylsiloxane, both methyl groups present in the siloxane bonds are arranged on the outside of the molecular chain, thereby exhibiting hydrophobicity and forming a release layer with excellent releasability, which is preferred.

[0104] In one embodiment, resin A may contain an aromatic group. The aromatic group is preferred because it maintains the stretchability of the coating composition and eliminates concerns about reduced adhesion due to stress differences between the substrate film and the release layer. Furthermore, the resulting release layer is free of defects such as film rupture during stretching, resulting in excellent releasability, which is preferred.

[0105] Examples of the aryl group include a phenyl group, a benzyl group, a tolyl group, and a xylyl group, and a phenyl group is particularly preferred.

[0106] The number average molecular weight of resin A is preferably 1000 or more and less than 30000, more preferably 2000 or more and less than 15000, and further preferably 3000 or more and less than 10000. If the number average molecular weight is 1000 or more, it is easy to be locally present on the surface of the release layer, and it is easy to obtain sufficient peeling properties. On the other hand, if the number average molecular weight is less than 30000, there is a tendency that the emulsification characteristics of the silicone emulsion become good and the uniform coating property also becomes good. It should be noted that the number average molecular weight in the present invention refers to the molecular weight obtained by 1 H NMR and 29 The peaks observed by Si NMR were used to identify the siloxane structure, and the value was calculated from the integrated ratio of the peaks derived from each siloxane structure.

[0107] When the total solid content in the coating composition is set to 100, the content of resin A contained in the silicone emulsion in the aqueous coating composition is preferably 5% by mass or more and 70% by mass or less, more preferably 7% by mass or more and 60% by mass or less, and further preferably 10% by mass or more and 55% by mass or less. If it is 5% by mass or more, the amount of resin A that exhibits peelability by being locally present on the surface of the release layer becomes sufficient, and the peelability is excellent, so it is preferred. If it is 70% by mass or less, there is no concern about the increase of uncrosslinked components and causing heavy peeling, so it is preferred. The amount of silicone emulsion in the aqueous coating composition can be appropriately adjusted in such a way that resin A is within the above range.

[0108] In the present invention, the total solid content in the coating composition refers to the total solid content of the resin C containing silicone containing both Q units and alkenyl groups, and the resins A, B, and D added as needed.

[0109] (Resin B)

[0110] Resin B may contain hydrogen groups and aryl groups, preferably with siloxane bonds in the main chain. It is preferably a polyorganosiloxane having hydrogen groups and aryl groups at the terminals or in the side chains, and more preferably comprises a polydimethylsiloxane structure. The terminal silicon atom may have a hydrogen group, preferably a trialkylsilane structure such as trimethylsilane, preferably with 2 or more and 50 or fewer hydrogen groups per molecule. Having two or more hydrogen groups allows for a highly crosslinked release layer during curing, resulting in easy release properties.

[0111] In one embodiment, the resin B may have a structure represented by the following Chemical Formula 2.

[0112]

[0113] In Chemical Formula 2, l is 1 or more and 50 or less, m is 1 or more and 50 or less, and n is 0 or more and 5 or less. If l is 1 or more and 50 or less, the cross-linking reaction between the alkenyl group and the hydrogen group in the coating composition proceeds, forming a release layer with a high cross-linking density and excellent solvent resistance, so it is preferred. By making m 1 or more and 50 or less, the reaction delay during curing of the release layer caused by the bulky phenyl group occurs, and a release layer with good tensile followability and excellent adhesion can be obtained, so it is preferred. In addition, the π electrons of the phenyl group interact with the substrate film, so the adhesion is more excellent, so it is preferred. Furthermore, by including the phenyl group as a rigid molecular skeleton, the elastic modulus of the release layer is improved, and the stripping property is excellent, so it is preferred.

[0114] When n is 0 or more and 5 or less, compatibility with the resin A or the resin D described later in the coating composition decreases, and the resin A or the resin D tends to be localized on the surface side of the release layer. As a result, the release layer has excellent releasability, which is preferred.

[0115] The number average molecular weight of the resin B in the present invention is preferably 1000 or more and less than 10000, more preferably 1000 or more and less than 5000, and further preferably 1500 or more and less than 3000. If the number average molecular weight is 1000 or more, sufficient peeling properties are easily obtained. On the other hand, if the number average molecular weight is less than 10000, there is a tendency that the emulsification properties of the silicone emulsion become good and the coating uniformity also becomes good. In addition, the cross-linking reaction is easy to proceed efficiently, the residual hydrogen groups in the release layer are reduced, and the peeling properties become good. It should be noted that the number average molecular weight in the present invention refers to the molecular weight obtained by 1 H NMR and 29 The peaks observed by SiNMR were used to identify the siloxane structure, and the value was calculated from the integrated ratio of the peaks derived from each siloxane structure.

[0116] When the total solid content in the coating composition is set to 100, the content of resin B contained in the silicone emulsion in the aqueous coating composition is preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 40% by mass or less, and even more preferably 5% by mass or more and 35% by mass or less. If it is 1% by mass or more, the crosslinking reaction proceeds sufficiently, which is preferred. If it is 50% by mass or less, there is no concern about the increase of unreacted components and the resulting heavy peeling, which is preferred.

[0117] The amount of the silicone emulsion in the aqueous coating composition can be appropriately adjusted so that the content of the resin B falls within the above-mentioned range.

[0118] For example, when resin B contains an aromatic group represented by structural formula 2, the content of resin B is equal to or less than the content of resin C described below, with the total solid content in the coating composition being 100. Preferably, the content of resin B is 5% by mass or less than the content of resin C described below. By satisfying such conditions, the crosslinking reaction proceeds sufficiently, and there is no concern of heavy peeling caused by an increase in unreacted components, which is preferable.

[0119] The structure containing an aryl group represented by Structural Formula 2 is preferably included in Resin B because it provides a high elastic modulus and excellent releasability of the release layer. Specifically, by including an aryl group in Resin B, which acts as a crosslinking agent, the aryl group can be evenly distributed in the release layer. This allows for the formation of a stronger release layer coating film due to the rigidity of the aryl group's own skeleton and the interaction of the aryl group's π electrons.

[0120] Furthermore, the inclusion of an aromatic group in Resin B reduces its compatibility with Resin A, making it easier for Resin A to localize on the surface of the release layer during stretching of the substrate film or drying and curing of the coating composition, thereby improving releasability. Furthermore, the aromatic group contained in Resin B, acting as a crosslinking agent, delays the curing reaction and enhances the interaction between the substrate film and the release layer, thereby improving adhesion. Thus, the present invention solves the problem of the release layer requiring time to cure due to excessively delayed curing reaction, thereby resolving conventional issues such as the inability to obtain a desired release layer due to rapid curing reaction.

[0121] (Resin C)

[0122] The organic silicone emulsion in the aqueous coating of the present invention comprises (c) resin C, wherein the resin C contains SiO 4 / 2 The Q unit and the alkenyl group represented by the silicone.

[0123] Resin C is a water-dispersed emulsion, colloid, or similar form of an organosilicon having this structure. While any organosilicon having this structure can be a compound containing siloxane bonds in its main chain, polyorganosiloxanes containing alkenyl groups at the terminals and / or in its side chains are preferred. Copolymers containing dialkylsiloxane units or alkylphenylsiloxane units are preferred because they exhibit releasability and allow for easy adjustment of the alkenyl group content per molecule. The terminal silicon atom preferably has an alkenyl group, but a trialkylsilane structure such as trimethylsilane is also acceptable.

[0124] As a SiO 4 / 2 The organosilicon of the Q unit represented by can be exemplified by the structure shown in the following Chemical Formula 3.

[0125] R4 a R5 b SiO (4-a-b) / 2 …(Chemical Formula 3)

[0126] (In Chemical Formula 3, R4 is an alkenyl group having 2 to 8 carbon atoms, R5 is a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, a represents 0 to 3, and b represents 0 to 3, and each represents an integer satisfying a+b≤3.)

[0127] Here, Chemical Formula 3 represents a general formula. Structural units with a=0 and b=0 are Q units, and structural units with a=1 or a=2 are siloxane structures having alkenyl groups. Resin C contains these structural units. Furthermore, structural units with b=2 are siloxane structures having only alkyl or aryl groups in their side chains, but these structures may also be present. Furthermore, structural units with a+b=3 represent siloxane structures having terminal groups.

[0128] Examples of the alkenyl group having 2 to 8 carbon atoms represented by R4 include vinyl, allyl, butenyl, pentenyl, and hexenyl, among which vinyl is particularly preferred. Examples of the alkyl group represented by R5 include methyl, ethyl, propyl, and butyl, and examples of the aryl group include phenyl and tolyl. From the perspective of reactivity with hydrogen groups, it is preferred that the alkenyl group having 2 to 8 carbon atoms represented by R4 is contained in the resin C. The fewer carbon atoms, the less steric hindrance and the better the reactivity, so a vinyl group having 2 carbon atoms is preferred, and the most preferred is vinyl group having 2 carbon atoms. From the perspective of easy strippability, it is preferred that 50 mol% or more of the substituents of R5 be methyl.

[0129] The organosilicon with Q units can obtain a structure with three-dimensional expansion of siloxane bonds, so the alkenyl groups in the molecule can also exist in a three-dimensional expansion. Therefore, by reacting the resin B, which is an organosilicon with hydrogen groups, with the alkenyl groups in the molecules of the resin C, a dense cross-linked structure can be obtained, and a release layer with excellent solvent resistance can be obtained. Generally speaking, if the release layer contains SiO 2 / 2 As the ratio of D units increases, the siloxane bonds tend to adopt a helical structure. For example, in the case of polydimethylsiloxane, both methyl groups present in the siloxane bonds are arranged on the outside of the molecular chain, resulting in hydrophobicity. On the other hand, if the ratio of Q units in the release layer increases, the helical structure of the siloxane bonds formed by the D units collapses, reducing hydrophobicity. While not particularly limited in theory, a release layer containing silicone containing Q units can achieve both easy release due to increased crosslinking density and reduced hydrophobicity due to the collapse of the helical structure of the siloxane bonds, i.e., excellent wettability.

[0130] The content of Resin C in the silicone emulsion in the aqueous coating composition is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 65% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less, relative to the total solids content in the coating composition. A content of 10% by mass or more is preferred because the helical structure of the silicone containing D units in the release layer is destroyed by the silicone containing Q units, resulting in a release layer with excellent wettability. A content of 70 parts by mass or less is preferred because the helical structure of the silicone containing D units in the release layer is not excessively destroyed by the silicone containing Q units, resulting in a release layer with excellent releasability.

[0131] The content of Si atoms in the Q units is 0.05 to 60 mol%, preferably 0.1 to 55 mol%, and more preferably 1.0 to 50 mol%, relative to the total Si atoms in the resin C. A content of 0.05 mol% or more of Si atoms in the Q units is preferred because it allows for a fully three-dimensionally extended siloxane bond structure, resulting in an increased crosslink density. A content of 60 mol% or less is preferred because there is no concern of severe peeling even when excessive wettability is imparted.

[0132] Furthermore, from the viewpoint of forming a dense crosslinked structure by reaction with the resin B, the content of Si atoms contained in the alkenyl-containing siloxane structure is preferably 0.05 to 30 mol %, more preferably 1.0 to 20 mol %, relative to all Si atoms in the resin C.

[0133] Silicones containing Q units are preferably solid at room temperature. This solidity means that the Q units within the molecule are present in large numbers in the form of continuous bonds, resulting in a rigid molecular skeleton and physical properties similar to glass. A release layer containing such a silicone with a rigid molecular skeleton improves the elastic modulus of the release layer, making it less likely to deform when peeling off a release object such as a ceramic green sheet, resulting in a release layer that exhibits easy peelability.

[0134] As mentioned above, silicones containing Q units lack stretching properties due to their rigid molecular skeletons, leading to concerns about coating film cracking and reduced substrate adhesion due to stretching. However, in the present invention, since a silicone emulsion containing an aromatic group represented by Structural Formula 2 is used as the coating composition, the reaction retardation effect makes it difficult for a crosslinking reaction to proceed during stretching of the substrate film. This allows the release layer to be formed without adhesion or coating defects, even when containing silicones containing Q units.

[0135] (Resin D)

[0136] By including (d) the resin D having alkenyl groups only at both ends in the silicone emulsion in the aqueous coating composition of the present invention, a release film having both releasability and wettability and excellent substrate adhesion can be obtained.

[0137] Examples of the resin D include resins shown in the following chemical formula 4.

[0138]

[0139] In Chemical Formula 4, R1 is an alkenyl group having 2 to 8 carbon atoms, and p is greater than 1 and less than 300. When p is within the above range, excellent peeling properties are exhibited, so it is preferred. Since resin D has alkenyl groups only at both ends, it becomes a structure in which D units are connected in a straight chain, so the helical structure will not collapse due to the cross-linking reaction, and it exhibits better peeling properties than resin A. However, the amount of alkenyl groups is less than that of resin A, so the cross-linking density may be reduced, but at the same time, by undergoing a cross-linking reaction with resin A having alkenyl groups in the side chain present in the release layer, the solvent resistance can be prevented from deteriorating. Although there is no particular limitation in theory, the release film of the present invention forms a release layer bonded to resin C having both Q units and alkenyl groups through resin A having alkenyl groups in the side chain by allowing resin D having alkenyl groups only at both ends to be locally present in the surface layer of the release layer, thereby achieving a release layer with excellent peeling properties.

[0140] The number average molecular weight of the resin D contained in the silicone emulsion of the present invention is preferably 1000 or more and less than 10000, more preferably 1000 or more and less than 5000, and further preferably 1500 or more and less than 3000. If the number average molecular weight is 1000 or more, sufficient peeling properties can be easily obtained. On the other hand, if the number average molecular weight is less than 10000, there is a tendency that the emulsification properties of the silicone emulsion become good and the coating uniformity also becomes good. The cross-linking reaction is easy to proceed efficiently, the residual hydrogen groups in the release layer are reduced, and the peeling properties become good. It should be noted that the number average molecular weight in the present invention refers to the molecular weight obtained by 1 H NMR and 29 The peaks observed by Si NMR were used to identify the siloxane structure, and the value was calculated from the integrated ratio of the peaks derived from each siloxane structure.

[0141] The content of resin D in the silicone emulsion in the aqueous coating composition, relative to the total solids content in the coating composition as 100, is preferably from 1% by mass to 50% by mass, more preferably from 5% by mass to 40% by mass, and even more preferably from 10% by mass to 35% by mass. A content of 1% by mass or greater is preferred because it allows for localization on the surface of the release layer, thereby exhibiting releasability. A content of 50% by mass or less is preferred because there is no concern about a decrease in the crosslinking density of the release layer, which could lead to heavy releasability.

[0142] The amount of the silicone emulsion in the aqueous coating composition can be appropriately adjusted so that the content of the resin D falls within the above range.

[0143] (Other ingredients)

[0144] The aqueous coating composition of the present invention preferably contains at least a surfactant. The inclusion of a surfactant provides excellent coating properties when applied to a polyester film serving as a substrate film, eliminating concerns about coating defects such as craters. Furthermore, the stability of the emulsion in the coating composition is not compromised, eliminating concerns about aggregates or gels of the coating composition being incorporated into the release layer. This allows for the suppression of unevenness and / or uneven coating of the release layer, thus being preferred.

[0145] The aqueous coating composition of the present invention requires a platinum-based catalyst to allow the addition reaction of the organosilicon having an alkenyl group with the organosilicon having a hydrogen group. Known platinum-based catalysts can be used, such as platinum chlorides and chloroplatinic acid. Considering dispersibility in the organosilicon, a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0) complex (Karstedt catalyst) can be used as the platinum-based catalyst. By dispersing the platinum-based catalyst simultaneously with emulsification of the organosilicon, uniform dispersibility can be ensured.

[0146] Regarding the amount of platinum-based catalyst, the weight of platinum element is preferably contained in the range of 10 to 800 ppm relative to the total solid content forming the release layer. By setting it to this range, the curing of the silicone can be fully carried out, and the generation of aggregates can be suppressed, and a release film with excellent smoothness can be obtained. If the weight ratio of the platinum element is 800 ppm or less, there is no concern that the addition reaction of the alkenyl group and the hydrogen group will be accelerated to produce silicone aggregates, so it is preferred. The amount of platinum-based catalyst is more preferably 600 ppm or less, further preferably 500 ppm or less, and more preferably 300 ppm or less. In addition, if it is 10 ppm or more, the silicone addition reaction proceeds efficiently, the curing of the release layer becomes sufficient, and light peeling properties are exhibited, so it is preferred.

[0147] The aqueous coating composition of the present invention preferably contains a reaction inhibitor to suppress the activity of the platinum-based catalyst at room temperature. The content of the reaction inhibitor is preferably 5 to 1000 ppm, more preferably 10 to 700 ppm, and even more preferably 20 to 500 ppm, relative to the total weight of the aqueous coating composition. A content of 5 ppm or more is preferred because it effectively suppresses the activity of the platinum-based catalyst. A content of 1000 ppm or less is preferred because there is no concern that the reaction inhibitor, which volatilizes during heat treatment, may contaminate the interior of the oven.

[0148] The aqueous coating composition of the present invention may further contain an adhesion-imparting agent, a colorant, an ultraviolet absorber, particles, and the like within a range that does not impair the objects of the present invention.

[0149] (Other release layer features)

[0150] For the release layer of the present invention, the surface elastic modulus calculated from the force curve obtained by force mapping measurement using an AFM (atomic force microscope) is preferably 20 MPa or more, more preferably 50 MPa or more, further preferably 70 MPa or more, and can also be 100 MPa or more, with larger surface elastic modulus values ​​being more preferred. If it is 20 MPa or more, it can suppress the erosion of the release layer by organic solvents during the molding of resin sheets and ceramic green sheets and / or the deformation of the release layer during peeling, thereby exhibiting light peelability, so it is preferred. The detailed measurement method is described below.

[0151] The surface elastic modulus may be, for example, 1000 MPa or less, 750 MPa or less, or 500 MPa or less.

[0152] The film thickness of the release layer in the present invention, measured after drying and curing, is preferably 0.001 to 0.2 μm, more preferably 0.005 to 0.1 μm. A thickness of 0.001 μm or greater is preferred because it provides a release layer with excellent releasability. A thickness of 0.2 μm or less is preferred because it eliminates the need to increase the solids concentration of the release layer components of the aqueous coating composition or the coating weight, resulting in excellent coating properties when applied to a substrate film.

[0153] (Method for producing release film)

[0154] In one embodiment, a release layer is formed on at least one side of a substrate film. The release layer is formed by applying an aqueous coating composition to the substrate film and then heating and drying the composition to form a release layer by reacting and solidifying the components of the aqueous coating composition. The release layer is preferably formed during the film forming step.

[0155] When applying the aqueous coating composition on the substrate film, with the composition in the aqueous coating composition, i.e. solid component as a benchmark, its solid component concentration is preferably below 20 mass %, more preferably more than 1 mass % and below 10 mass %. If the solid component concentration of the release layer component in the aqueous coating composition is more than the lower limit, then there is a tendency for film forming to become good. In addition, if the solid component concentration is below the upper limit, then the stability of the aqueous coating composition, the outward appearance of the release layer easily become good. As the aqueous solvent for adjusting solid component concentration, preferably water is used.

[0156] To form a release layer, the aqueous coating composition can be applied to the substrate film at any stage, preferably during the polyester film production process, and more preferably before the polyester film has been oriented and crystallized. The film is then stretched in at least one direction and then heat-treated to complete the crystallization.

[0157] Here, the polyester film before the completion of crystal orientation refers to an unstretched film, or a uniaxially oriented film in which the unstretched film is oriented in any direction in the longitudinal direction (hereinafter sometimes referred to as the film continuous film forming direction, the length direction, the MD direction) or the transverse direction (hereinafter sometimes referred to as the direction orthogonal to the longitudinal direction, the width direction, the TD direction), and a film oriented by low-ratio stretching in both the longitudinal and transverse directions (a biaxially stretched film that is finally stretched in the longitudinal or transverse direction before the completion of oriented crystallization).

[0158] Among them, it is preferred to apply the aqueous coating composition to an unstretched film or a uniaxially stretched film oriented in one direction, and to maintain this state to perform longitudinal stretching and / or transverse stretching and to perform so-called online coating by heat setting. The release layer can be dried by a stretching step or heat setting treatment after coating, and a drying step can be added as needed. In addition, when a catalyst is used to solidify the composition to obtain a solidified coating, it can be solidified by a stretching step or heat setting treatment, and a curing step can be added as needed.

[0159] Regarding the release layer in the present invention, specifications such as "a water-based coating composition is applied to an unstretched film or a uniaxially stretched film oriented in one direction, and longitudinal stretching and / or transverse stretching is performed while maintaining this state, and heat setting is performed" and specifications such as "the release layer is formed by an online coating method" determine the structure of the object by the manufacturing method, but as described below, there are cases where it is impossible or generally impractical to directly determine the object by its structure or characteristics.

[0160] It is speculated that the aqueous coating composition for forming the release layer of the present invention is longitudinally stretched and / or transversely stretched together with the coated film, so that the resins A, B, C, and optionally D contained in the silicone emulsion are oriented and interact with each other.

[0161] For example, it is speculated that during the drying process of the water in the aqueous coating composition, the stretching of the substrate film, or the curing of the release layer, due to the difference in compatibility and molecular weight among resins A, B, and C, resin A tends to be localized on the surface side of the release layer, thereby improving the releasability.

[0162] On the other hand, in the present invention, the curing reaction caused by the aromatic group contained in the resin B functioning as a crosslinking agent can be appropriately controlled, and the adhesion between the substrate film and the release layer is improved by increasing the interaction between the substrate film and the release layer.

[0163] However, it is difficult to structurally determine the orientation and distribution of the resin component in the release layer, the distribution of the substituents contributing to releasability on the surface of the release layer, and other states.

[0164] Furthermore, given the measurement technology available at the time of filing this application, it is also impossible or impractical to measure the structure or properties of the release film of the present invention and analyze and determine the physical properties based on these results. Therefore, with respect to the present invention, at the time of filing this application, there are cases where it is impossible or largely impractical to directly determine the object based on its structure or properties.

[0165] As a method for applying the aqueous coating composition, any known coating method can be applied, for example, roll coating, gravure coating, roller brush coating, spray coating, air knife coating, dipping, curtain coating, etc. can be used alone or in combination.

[0166] In one embodiment, the manufacturing method of the present invention provides a method for manufacturing a release film, which is used for manufacturing a resin sheet and a laminated ceramic capacitor.

[0167] (resin sheet)

[0168] The resin sheet in the present invention is not particularly limited as long as it is a sheet formed on the surface of the release layer opposite to the substrate. For example, a resin sheet formed by curing a resin sheet-forming composition containing a resin component and a crosslinking agent, a resin sheet formed by molding a film-forming organic component by melt film forming or solution film forming, etc. In one embodiment, the release film of the present invention is a release film for molding a resin sheet containing an inorganic compound. As inorganic compounds, metal particles, metal oxides, minerals, etc. can be exemplified, for example, calcium carbonate, silica particles, aluminum particles, barium titanate particles, etc. can be exemplified. Since the present invention has a release layer with high smoothness, even if these inorganic compounds are included in the resin sheet, defects that may be caused by inorganic compounds, such as damage to the resin sheet and difficulty in peeling the resin sheet from the release layer, can be suppressed.

[0169] The resin component forming the resin sheet can be appropriately selected depending on the intended use. In one embodiment, the resin sheet containing an inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. Alternatively, the resin component may contain, for example, a polyvinyl butyral resin.

[0170] (Ceramic Green Sheets and Ceramic Capacitors)

[0171] Typically, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. First and second internal electrodes are alternately arranged within the ceramic body along the thickness direction. The first internal electrode is exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0172] In one embodiment, the release film of the present invention is a release film for producing ceramic green sheets, and is used for producing such a laminated ceramic capacitor.

[0173] For example, if the release film for manufacturing ceramic green sheets of the present invention is used, the ceramic green sheets are manufactured, for example, in the following manner. First, the release film of the present invention is used as a carrier film, and the ceramic slurry for constituting the ceramic body is applied and dried. A conductive layer for constituting the first or second internal electrode is printed on the ceramic green sheet after coating and drying. The ceramic green sheet, the ceramic green sheet printed with the conductive layer for constituting the first internal electrode, and the ceramic green sheet printed with the conductive layer for constituting the second internal electrode are appropriately stacked and pressed to obtain a mother laminate. The mother laminate is divided into a plurality of pieces to produce unprocessed ceramic bodies. The ceramic body is obtained by firing the unprocessed ceramic body. Thereafter, the first and second external electrodes are formed to complete the stacked ceramic capacitor.

[0174] Example

[0175] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples. The characteristic values ​​used in the present invention were evaluated using the following methods.

[0176] (Release layer thickness)

[0177] After cutting the release film into triangular pieces, a Pt (platinum) layer with a thickness of 2nm is formed on the surface of the release layer by coating. The obtained sample is fixed in a multi-axis embedding capsule, embedded with epoxy resin, and sliced ​​in a direction perpendicular to the surface direction of the film using a microtome ULTRACUT-S to obtain an ultra-thin sample with a height of 50nm. Next, the obtained ultra-thin sample is placed on a grid and steam-stained with 2% osmium acid at 60°C for 2 hours. Using the ultra-thin sample after steam staining, the film cross-section is observed using a transmission electron microscope LEM-2000 at an acceleration voltage of 100kV to measure the thickness of the release layer. Measurements are performed on any 10 points, and their average value is taken as the thickness of the release layer.

[0178] (Coating uniformity of release layer)

[0179] The roll-formed release film was unwound and cut into A4 sheets. The release layer was visually observed using a fluorescent lamp and a halogen lamp. The number of aggregated coating defects (per A4 sheet) was compared and evaluated based on the following criteria.

[0180] ◎: No coating defects

[0181] ○: 1 to 2 coating defects

[0182] △: 3 to 5 coating defects

[0183] ×: 6 or more coating defects

[0184] (Adhesion to substrate)

[0185] The release surface of the release film was rubbed 10 times with the thumb at a load of approximately 500 gf. To confirm the detachment of the silicone in this area, an adhesive tape (manufactured by Nitto Denko Corporation, trade name "No. 31B Tape") was attached. The peeling state of the adhesive tape was confirmed and evaluated based on the following criteria.

[0186] ○: No peeling change when the adhesive tape is peeled off

[0187] △: There is a slight change in the peeling of the adhesive tape

[0188] ×: There is a change in the peeling of the adhesive tape.

[0189] (Surface free energy)

[0190] For samples humidified at 23°C and 50% RH for 24 hours, the static contact angle was measured using a contact angle meter (DMo-501 manufactured by Kyowa Interface Chemical Co., Ltd.) when water was added and allowed to stand for 30 seconds. Similarly, the static contact angles of ethylene glycol and diiodomethane were measured. Using the surface tension components of the following liquids, the following simultaneous equations related to the surface tension components of the release layer were established (the measured liquids for water, ethylene glycol, and diiodomethane are 1, 2, and 3, respectively; γLD represents the dispersion force component of the liquid, γLP represents the polar force component of the liquid, γLH represents the hydrogen bonding component of the liquid, and γL represents the total value of the surface tension components in the liquid. γSD represents the dispersion force component of the release layer, γSP represents the polar force component of the release layer, and γSH represents the hydrogen bonding component of the release layer. In addition, θ represents the contact angle).

[0191] (γSD·γLD1) 1 / 2 +(γSP·γLP1) 1 / 2 +(γSH·γLH1) 1 / 2 =γL1(1+cosθ1)) / 2

[0192] (γSD·γLD2) 1 / 2 +(γSP·γLP2) 1 / 2 +(γSH·γLH2) 1 / 2 =γL2(1+cosθ2)) / 2

[0193] (γSD·γLD3) 1 / 2 +(γSP·γLP3) 1 / 2 +(γSH·γLH3) 1 / 2 =γL3(1+cosθ3)) / 2

[0194] It should be noted that γLD, γLP, γLH, and γL of water, ethylene glycol, and diiodomethane are shown in Table 1.

[0195] [Table 1]

[0196]

[0197] Next, the surface free energy γS of the release layer surface is calculated using the following formula from the numerical values ​​of γSD, γSP, and γSH obtained above.

[0198] γS=γSD+γSP+γSH

[0199] (Ceramic sheet peeling properties)

[0200] Slurry composition I containing the following materials was stirred and mixed for 10 minutes, and then dispersed using zirconia beads with a diameter of 0.5 mm using a bead mill for 10 minutes to obtain a primary dispersion. Slurry composition II containing the following materials was then added to the primary dispersion at a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0, and a secondary dispersion was performed using zirconia beads with a diameter of 0.5 mm using a bead mill for 10 minutes to obtain a ceramic slurry.

[0201] (Slurry composition I)

[0202]

[0203]

[0204] Next, the release surface of the obtained release film sample was coated with the dried slurry to a thickness of 2.0 μm using a film applicator, and dried at 60°C for 1 minute to obtain a release film with a ceramic green sheet. The obtained release film with a ceramic green sheet was de-electrified using a de-electrifier (SJ-F020 manufactured by KEYENCE CORPORATION), and then peeled using a peel tester (VPA-3 manufactured by Kyowa Interface Science Co., Ltd., load cell load 0.1N) at a peel angle of 90 degrees, a peel temperature of 60°C, and a peel speed of 0.3 m / min. As the peeling direction, a double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was adhered to the SUS plate attached to the peel tester, and the release film was fixed thereon in a manner such that the release film side was bonded to the double-sided adhesive tape, and peeled in a manner such that the ceramic green sheet side was stretched. From the obtained measured values, the average value of the peeling force at a peeling distance of 20 mm to 70 mm was calculated, and this value was used as the peeling force. The measurement was performed 5 times in total, and the average value of the peeling force was used for evaluation. The obtained peeling force values ​​were judged based on the following criteria.

[0205] ◎: less than 1.0mN / mm

[0206] ○: less than 1.5mN / mm

[0207] △: less than 2.0mN / mm

[0208] ×: 2.0mN / mm or more

[0209] (Surface elastic modulus of release layer)

[0210] The surface of the release layer of the release film was measured using an AFM (NX10 manufactured by Park Systems) in PinPoint mode. The elastic modulus was determined by analysis based on JKR contact theory. The elastic modulus was calculated as the average of 100 or more measurements taken on the smooth surface, excluding the lubricant portion. The elastic modulus was calculated using a Poisson's ratio of 0.4, a cantilever tip diameter (R) of 30 nm, and a cantilever with a spring constant of 0.3-0.6 N / m.

[0211] Specifically, the force curve slope (Force Slope), sensitivity (Sensitivity) and spring constant (Spring Constant) were evaluated according to the manual of the PinPoint mode, and then the measurement was performed under the following conditions.

[0212] The measurement conditions are as follows.

[0213] ·Measurement device: Atomic force microscope (NX10) manufactured by Park Systems

[0214] Measurement mode: PinPoint mode

[0215] Cantilever: NSC36 / Pt-C manufactured by Makro Masch (Pt coating on both sides)

[0216] ·Measurement atmosphere: 23℃, air

[0217] Setpoint: 1 (nN)

[0218] Cantilever speed: 25μm / s

[0219] (Silicone emulsion: a-1)

[0220] Using an emulsifier capable of stirring the entire container (manufactured by NPLABO Co., Ltd., "Ultra Planetary Mixer"), a raw material comprising 98% by mass of an alkenyl-containing silicone represented by the chemical formula (a-1) (o=125, k=4, number average molecular weight 9756) and 2% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "EMULGEN 109P") as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (a-1) having a solids content of 20% by mass. The emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification.

[0221]

[0222] (Silicone emulsion: a-2)

[0223] Using an emulsifier capable of stirring the entire container (manufactured by NPLABO Co., Ltd., device name "Ultra Planetary Mixer"), a raw material containing 98% by mass of an organosilicon containing alkenyl and phenyl groups represented by chemical formula (a-2) (o=115, k=4, m=5, number average molecular weight 9696) and 2% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "EMULGEN 109P") as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (a-2) having a solid content of 20% by mass.

[0224] In addition, the particle size of the emulsion can be adjusted by adjusting the stirring speed and stirring time during emulsification.

[0225]

[0226] (Silicone emulsion: b-1)

[0227] Using an emulsifier capable of stirring the entire container (manufactured by NPLABO Co., Ltd., "Ultra Planetary Mixer"), a raw material comprising 98% by mass of a hydrogen- and phenyl-containing organosilicon (l=21, m=8, n=4, number average molecular weight 2806) represented by the chemical formula (b-1) and 2% by mass of polyoxyethylene lauryl ether (trade name "EMULGEN 109P" manufactured by Kao Corporation) as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (b-1) having a solids content of 20% by mass. The particle size of the emulsion was adjusted by adjusting the stirring speed and stirring time during emulsification.

[0228]

[0229] (Silicone emulsion: b-2)

[0230] Using an emulsifier capable of stirring the entire container (manufactured by NPLABO Co., Ltd., "Ultra Planetary Mixer"), a raw material comprising 98% by mass of a hydrogen- and phenyl-containing organosilicon (l=40, n=40, number average molecular weight 5522) represented by the chemical formula (b-2) and 2% by mass of polyoxyethylene lauryl ether (trade name "EMULGEN 109P" manufactured by Kao Corporation) as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (b-2) having a solids content of 20% by mass. The emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification.

[0231]

[0232] (Silicone emulsion: c-1)

[0233] An emulsifying device capable of stirring the entire container (manufactured by NPLABO Co., Ltd., device name "Ultra planetary mixer") was used to mix the emulsifying device containing SiO 4 / 2 A raw material comprising 98% by mass of silicone having Q units and 2% by mass of polyoxyethylene lauryl ether (trade name "EMULGEN 109P" manufactured by Kao Corporation) as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (c-1) containing silicone having Q units and having a solid content of 20% by mass. 4 / 2 The organosilicon of Q unit represented by the general formula 3 is represented by R4 is a vinyl group, R5 is a methyl group, and only one vinyl group is bonded to the Si atom to which the vinyl group is directly bonded. 4 / 2 The total Si atoms in the silicone of the Q unit represented by the formula (3) were 5 mol% of Si atoms bonded to vinyl groups, and the content of Si atoms contained in the Q unit was 40 mol%. Specifically, the composition included: a siloxane structure in which R4 is a vinyl group, R5 is a methyl group, a=1, and b=1, 5 mol% of the structure, a=0, b=0, 40 mol% of the structure, and 55 mol% of the structure in which R5 is a methyl group, a=0, and b=2 or 3. The emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification. The number average molecular weight was adjusted to 200,000.

[0234] R4 a R5 b SiO (4-a-b) / 2 …(Chemical Formula 3)

[0235] (In Chemical Formula 3, R4 is an alkenyl group having 2 to 8 carbon atoms, R5 is a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, a represents 0 to 3, and b represents 0 to 3, and each represents an integer satisfying a+b≤3.)

[0236] (Silicone emulsion: d-1)

[0237] Using an emulsifier capable of stirring the entire container (manufactured by NPLABO Co., Ltd., "Ultra Planetary Mixer"), a raw material comprising 98% by mass of an organosilicon (p=23, number average molecular weight 1888) having alkenyl groups only at both ends represented by the chemical formula (d-1) and 2% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "EMULGEN 109P") as a surfactant was mechanically emulsified in an aqueous medium to obtain a silicone emulsion (d-1) having a solids content of 20% by mass. The emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification.

[0238]

[0239] <Production Example 1 of Aqueous Coating Composition>

[0240] Silicone emulsion (a-1), silicone emulsion (b-1), silicone emulsion (c-1), silicone emulsion (d-1), and water were mixed at the ratios shown in Table 2 to a solid content concentration of 4% by mass to obtain an aqueous coating composition. At this time, 0.02% by mass of a platinum-based catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: CAT-PM-10A) and 150 ppm of a cross-linking reaction inhibitor (1-ethynylcyclohexanol) were mixed with each other based on the total weight of the aqueous coating composition.

[0241] <Production Examples 2 to 8 of Aqueous Coating Compositions>

[0242] Except for mixing according to the types and ratios described in Table 2, an aqueous coating composition was obtained in the same manner as in Production Example 1.

[0243] <Example 1>

[0244] Polyethylene terephthalate ([η] = 0.63dl / g, Tg = 78 ° C) containing 0.25% by mass of calcium carbonate particles with an average particle size of 0.6 μm was melted by an extruder, passed through a filter with a filtration accuracy of 10 μm, extruded from a die, and cooled with a cooling drum by a conventional method to form an unstretched film. Then, after being stretched to 3.2 times at 80 ° C in the longitudinal direction, the aqueous coating composition obtained in Manufacturing Example 1 was evenly applied to one surface of the polyester film with a roll coater. Then, the coated film was dried at 115 ° C, stretched to 4.0 times in the transverse direction at 145 ° C, and then heat-set at 230 ° C for about 10 seconds. After completing the crystal orientation of the substrate film, it was wound into a roll, thereby obtaining a roll of a release film (thickness 25 μm) with a release layer shown in Table 2. The evaluations described in Table 2 were performed using samples obtained by rolling out the release film from the release film roll obtained and cutting it into A4 versions. The amount of the aqueous coating composition applied was such that the thickness of the release layer after curing and stretching would be the thickness described in Table 2.

[0245] <Examples 2 to 6>

[0246] A release film was obtained by the same method as in Example 1 except that the aqueous coating composition obtained in the Production Example described in Table 2 was used.

[0247] <Comparative Example 1>

[0248] A release film was obtained by the same method as in Example 1 except that the aqueous coating composition obtained in the Production Example described in Table 2 was used.

[0249] As shown in Table 2, Examples 1 to 6 produced release films with excellent release layer coating uniformity, substrate adhesion, and ceramic sheet releasability. Furthermore, the release films had a surface free energy of 17 mN / m or greater and excellent ceramic slurry wettability.

[0250] In contrast, in Comparative Example 1, since the release layer was formed using the aqueous coating composition containing no resin C, the surface elastic modulus of the release layer was low, and the releasability of the ceramic sheet was insufficient.

[0251] <Reference Example 1>

[0252] The aqueous coating composition obtained in Production Example 1 was applied to one surface of a 25 μm thick biaxially oriented polyester film (Toyobo Ester Film E5100, manufactured by Toyobo Co., Ltd.) using a reverse gravure plate to a release layer thickness of 0.1 μm after drying. The film was dried at 135°C for 60 seconds and then wound into a roll to obtain a release film roll. Samples cut into A4 sizes from the resulting release film roll were used for the evaluations listed in Table 2.

[0253] <Reference Example 2>

[0254] A release film was obtained by the same method as in Example 1 except that the aqueous coating composition obtained in the Production Example described in Table 2 was used.

[0255] In Reference Example 1, since the release layer is formed by an off-line coating method, the drying and curing heat of the aqueous coating composition is insufficient, resulting in deformation of the release layer when wound into a roll. Therefore, the coating uniformity, substrate adhesion, and ceramic sheet peelability of the release layer are poor. In addition, the deviation of the contact angle value of the release layer is large, making it difficult to accurately measure the surface free energy. In Reference Example 2, since the release layer is formed by using an organosilicon having no aromatic group and a hydrogen group as a crosslinking agent, the tensile followability of the coating composition is poor and the substrate adhesion is poor. In addition, compared with the use of the resin B of the present invention having an aromatic group, the surface elastic modulus is reduced, and some deterioration trends are also observed for the peelability.

[0256] [Table 2]

[0257]

[0258] Industrial applicability

[0259] The release layer of the release film of the present invention has high releasability and wettability, and the adhesion between the substrate film and the release layer is high. The release layer is difficult to fall off, thereby suppressing the occurrence of defects when molding thin resin sheets, especially ceramic green sheets.

Claims

1. A release film comprising a release layer on at least one side of a polyester film, The release layer is a layer formed by reacting and solidifying the aqueous coating composition. The aqueous coating composition comprises a silicone emulsion, The silicone emulsion contains 20% by mass or more of (c) resin C in terms of solid content relative to the total weight of the solid content in the aqueous coating composition, wherein the resin C contains SiO 4 / 2 The Q unit and alkenyl silicone represented by The surface elastic modulus of the release layer calculated from the force curve obtained by measurement using AFM is 20 MPa or more.

2. The release film according to claim 1, wherein The silicone emulsion in the aqueous coating composition comprises: (a) a resin A having an alkenyl group and no aromatic group; and (b) Resin B having a hydrogen group and an aromatic group.

3. The release film according to claim 1, wherein The resin B has a structure shown in Chemical Formula 2, and a number average molecular weight of 1000 or more and less than 5000. In Chemical Formula 2, l is 1 to 50, m is 1 to 50, and n is 0 to 5.

4. The release film according to claim 1, wherein The release film is formed as follows: The aqueous coating composition is coated on a substrate film before the crystal orientation is completed, and then stretched in at least one direction and heat-treated to complete the crystal orientation of the substrate film, thereby forming the substrate film.

5. The release film according to claim 1, wherein The polyester film has a surface layer substantially free of inorganic particles, and a release layer is formed on the surface layer.

6. The release film according to claim 1, wherein The release film is a release film for producing ceramic capacitors or resin sheets.

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