Release film for ceramic green sheet production

Abstract

Provided is a release film for ceramic green sheet production that can be peeled off with low and uniform force even when the thickness of the ceramic green sheet is 1 μm or less, and that does not have to worry about the occurrence of defects due to foreign matter adhering to the film due to electrification. A release film for ceramic green sheet production in which, when a polyester film is used as a base material, a layer formed on one surface of the base material is a surface layer A, and a layer formed on the other surface is a surface layer B, a release layer is directly laminated on the surface layer A or is laminated on the surface layer A with other layers interposed, and the release layer is brought into contact with the surface layer B, and the amount of electrification of the release layer when the release layer and the surface layer B are peeled off after being left in an atmosphere at 50°C under a pressure of 10 kPa for 48 hours is ±5 kV or less.

Description

[0001] This application is a divisional application of the application with the application number 2020800471179, the title of "Release Film for Green Sheet Manufacturing of Ceramic", and the filing date of June 3, 2020. TECHNICAL FIELD

[0002] The present application relates to a release film for green sheet manufacturing of ceramic, and more particularly, to a release film for green sheet manufacturing of ceramic, which can suppress occurrence of process defects such as planar defects and peeling defects when manufacturing a green sheet of an ultra-thin layer, and which has a low charge amount, thereby reducing attachment of foreign matter to the release film and suppressing mixing of the foreign matter into the green sheet of the ultra-thin layer. BACKGROUND

[0003] In the past, a release film in which a release layer is laminated on a polyester film as a base material has been used for a green sheet molding use such as a laminated ceramic capacitor, a ceramic substrate, and the like. In recent years, with the miniaturization and large capacity of the laminated ceramic capacitor, there is a tendency that the thickness of the green sheet is also thinned. The green sheet is molded by coating a slurry containing a ceramic component such as barium titanate and a binder resin on the release film and drying it. After the molding, an electrode is printed on the green sheet, and after peeling from the release film, the green sheet is laminated, pressed, and fired, and an external electrode is applied, thereby manufacturing a laminated ceramic capacitor. In the case where the release layer surface of the polyester film is molded into a green sheet, the minute protrusions on the release layer surface affect the molded green sheet, and there is a problem that defects such as depressions and pinholes are easily generated. Therefore, various methods for achieving a release layer surface having excellent flatness have been developed (for example, Patent Literature 1).

[0004] However, in recent years, further thinning of the green sheet has been promoted, and there is a gradual demand for a green sheet having a thickness of 1.0 μm or less, and more particularly, 0.2 μm to 1.0 μm. Therefore, the extremely small unevenness present on the release layer surface is also transferred to the molded green sheet, causing unevenness in thickness, and there is a concern that this leads to defects.

[0005] Therefore, in recent years, various methods for achieving smoothing of the release layer have been developed. For example, there is a method in which a smoothing layer is provided between the release layer and the base material to fill the unevenness generated by the particles contained in the base material, thereby improving the flatness of the release layer surface (for example, Patent Literature 2). In addition, a scheme has been proposed in which the surface of the base material on the side on which the release layer is provided is a layer substantially containing no particles, thereby improving the flatness of the release layer surface (for example, Patent Literature 3).

[0006] However, in the methods of Patent Documents 2 and 3, the release layer becomes smooth, which raises the issue that the release film becomes more prone to becoming charged. More specifically, when the film is rolled into a roll, the contact area between the release layer and the opposite surface (back side) increases. Therefore, due to the film's curling edges, vibrations during transport, etc., the release layer and the opposite surface (back side) rub against each other, making it more prone to becoming charged. If the release film becomes charged, minute environmental foreign matter during the process and film debris generated during cutting can easily adhere due to static electricity, mixing into the ceramic green sheet and potentially causing defects.

[0007] Methods for suppressing static electricity in the release film include: containing an antistatic agent in the release layer; providing an antistatic coating layer on the side opposite to the release layer, in the intermediate layer between the release layer and the substrate film; etc. (e.g., Patent Documents 4 and 5). However, as in Patent Document 4, when the release layer contains an antistatic agent, there is a concern that the antistatic agent, which has poor compatibility with the release components, may aggregate and become large protrusions. Furthermore, there are concerns that it may adversely affect surface properties and curing properties, and that the peelability of ultra-thin ceramic green sheets may become insufficient. Additionally, as in Patent Document 5, when an antistatic layer is provided on the side opposite to the release layer, in the intermediate layer between the release layer and the substrate film, the processing steps increase, and antistatic agents are generally expensive, thus increasing costs and posing a significant economic challenge.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2000-117899

[0011] Patent Document 2: Japanese Patent Application Publication No. 2009-208236

[0012] Patent Document 3: Japanese Patent Application Publication No. 2015-033811

[0013] Patent Document 4: Japanese Patent Application Publication No. 2014-189007

[0014] Patent Document 5: International Publication No. 2016 / 133092 Summary of the Invention

[0015] The problem the invention aims to solve

[0016] This invention was made against the backdrop of the aforementioned problems in the prior art. Specifically, it is desirable to provide a release film for manufacturing ceramic green sheets that maintains high smoothness of the release layer surface, has low and uniform peel force, and consequently has low charge on the release film, and can be formed into ultra-thin ceramic green sheets with fewer defects even in sheets with a thickness of less than 1 μm.

[0017] Solution for solving the problem

[0018] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by using a polyester film, and by directly setting a release layer on the surface layer A of the polyester film or by setting a release layer sandwiched with other layers, the release layer is formed by curing a composition containing a specific release agent and a melamine-based compound, thereby providing a release film for manufacturing ceramic green sheets with excellent smoothness and peelability of ceramic green sheets and low charge.

[0019] That is, the present invention comprises the following components.

[0020] 1. A release film for manufacturing ceramic green sheets, wherein when a polyester film is used as a substrate, a layer forming one surface of the substrate is used as surface layer A, and a layer forming the other surface is used as surface layer B, the release layer is directly stacked on the surface layer A or stacked on the surface layer A with other layers sandwiched between them, and the release layer is in contact with the surface layer B. After being kept in an atmosphere of 50°C and a pressure of 10 kPa for 48 hours, the charge of the release layer when it is peeled off from the surface layer B is less than ±5 kV.

[0021] 2. The release film for manufacturing ceramic green sheets according to the first description above, wherein the static friction coefficient μs when the aforementioned release layer overlaps with the aforementioned surface layer B is less than 0.30.

[0022] 3. The release film for manufacturing ceramic green sheets according to the first or second method described above, wherein no antistatic layer is provided on the surface of surface layer A and surface layer B, and surface layer A and surface layer B do not contain an antistatic agent.

[0023] 4. A release film for manufacturing ceramic green sheets according to any one of the above-described 1 to 3, wherein the aforementioned release layer is formed by curing a composition comprising at least a release agent and a melamine-based compound, the aforementioned release layer forming composition does not contain an antistatic agent, the aforementioned melamine-based compound has a weight-average degree of polymerization of 1.7 or less, and the content of the aforementioned melamine-based compound in the aforementioned release layer is 80% by mass or more relative to the solid content of the aforementioned release layer forming composition.

[0024] 5. A release film for manufacturing ceramic green sheets according to any one of the above-mentioned 1 to 4, wherein the release agent contained in the aforementioned release layer forming composition is a polyorganosiloxane containing a carboxyl group.

[0025] 6. The release film for manufacturing ceramic green sheets according to any one of the above-mentioned 1 to 5, wherein the surface layer A substantially does not contain inorganic particles.

[0026] 7. A release film for manufacturing ceramic green sheets according to any one of claims 1 to 6 above, wherein the surface layer B contains particles, at least a portion of which are silica particles and / or calcium carbonate particles, and the total content of the particles is 5,000 to 15,000 ppm relative to the mass of the surface layer B.

[0027] 8. A method for manufacturing a ceramic green sheet, wherein the ceramic green sheet is formed into a ceramic green sheet using a release film for manufacturing a ceramic green sheet as described in any one of the above-described 1 to 7, and the formed ceramic green sheet has a thickness of 0.2 μm to 1.0 μm.

[0028] 9. A method for manufacturing a ceramic capacitor, which employs the method for manufacturing ceramic green sheets described in section 8 above.

[0029] The effects of the invention

[0030] The release film for manufacturing ultrathin ceramic green sheets of the present invention has low charge, smooth surface of release layer, and excellent peelability of ceramic green sheets. Therefore, it can suppress foreign matter from entering the ceramic green sheets and causing defects, and can effectively manufacture ultrathin ceramic green sheets of 0.2 to 1.0 μm. Detailed Implementation

[0031] The present invention will now be described in detail.

[0032] Preferably, the release film for manufacturing ceramic green sheets of the present invention is a release layer directly laminated to surface layer A of a polyester film serving as a substrate, or laminated to surface layer A of a polyester film serving as a substrate with other layers sandwiched between them, and no antistatic layer is provided on surface layer A and surface layer B on the opposite side of surface layer A. Furthermore, it is preferable that the release layer does not contain an antistatic agent and is formed by curing a composition comprising at least a melamine-based compound and a polyorganosiloxane.

[0033] The release film for manufacturing ceramic green sheets of the present invention preferably has a release layer that is not easily charged. Regarding charge, more specifically, the increased charge that sometimes occurs when the film is wound up and stored in rolls after processing the release layer during the release film manufacturing process can be problematic. For example, if the charge on the rolled film is high, minute environmental impurities and film debris generated during cutting can easily adhere to the film during the cutting process and the ceramic green sheet forming process. There is a concern that these impurities adhering to the film may mix into the ceramic green sheets, leading to defects. Therefore, a release film having a release layer that is not easily charged is preferred.

[0034] As an example of evaluating the resistance to charging, the charge on the release layer after contacting it with surface layer B, applying a load, and maintaining it for a constant time is evaluated, thus confirming the resistance. In this evaluation method, the increase in charge over time when the film is stored in a roll can be evaluated using a model. A detailed evaluation method will be described later.

[0035] The charge on the release layer, as measured by the evaluation method described below, is preferably ±5kV or less, for example, ±3.4kV or less, and more preferably ±3kV or less; the smaller the absolute value, the better. By ensuring that the charge on the release layer is ±5kV or less, the increase in charge over time when the film is stored in a roll is minimal, and foreign matter is less likely to adhere to the film, which is therefore preferable. A lower charge on the release layer is more preferable, but it can be 0.1kV or more, or even 0.3kV or more.

[0036] It should be noted that, in this invention, the antistatic agent refers to substances used for imparting conductivity, such as ionicly conductive polymers, π-electron conjugated polymers, conductive fillers, metal layers, and metal oxide layers. Examples of ionicly conductive polymers include ammonium-containing compounds, polyether compounds, sulfonic acid compounds, and betaine compounds. Examples of π-electron conjugated polymers include polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothiaphthene, and polythiophene. Examples of conductive fillers include metals such as gold, silver, copper, aluminum, nickel, titanium, iron, zinc, and tin, their alloys, fibers, metal oxide fillers (excluding silica, titanium dioxide, etc., used specifically for purposes other than conductivity such as sliding properties), metal-coated synthetic fibers, and conductive carbon fibers such as carbon nanotubes. Furthermore, in this invention, the antistatic layer refers to a layer containing the aforementioned antistatic agents to exert an antistatic effect.

[0037] (Polyester film)

[0038] The polyester constituting the polyester film used as the substrate in this invention is not particularly limited. A polyester film obtained by film forming of a polyester commonly used as a substrate for release films can be used. Preferably, it can be a crystalline linear saturated polyester composed of aromatic dicarboxylic acid components and glycol components. For example, polyethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, polyethylene terephthalate, polyethylene terephthalate, propylene terephthalate, or copolymers with components of these resins as the main components are particularly suitable. Polyester films formed from polyethylene terephthalate are especially suitable. For polyethylene terephthalate, the repeating unit of polyethylene terephthalate is preferably 90 mol% or more, more preferably 95 mol% or more. Small amounts of other dicarboxylic acid components and glycol components can be copolymerized. From a cost perspective, a polyester film made solely of terephthalic acid and ethylene glycol is preferred. Furthermore, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizing agents, can be added to the extent that they do not impair the effects of the film of the present invention. For reasons such as the high elastic modulus in both directions, the polyester film is preferably a biaxially oriented polyester film.

[0039] The intrinsic viscosity of the aforementioned polyester film is preferably 0.50 to 0.70 dl / g, more preferably 0.52 to 0.62 dl / g. An intrinsic viscosity of 0.50 dl / g or higher is preferred because it minimizes breakage during the stretching process. Conversely, an intrinsic viscosity of 0.70 dl / g or lower is preferred because it provides good cutability when cut to the specified product width, preventing dimensional defects. Furthermore, the raw material granules are preferably thoroughly vacuum-dried.

[0040] The manufacturing method of the polyester film in this invention is not particularly limited, and conventionally used methods can be employed. For example, it can be obtained as follows: the aforementioned polyester is melted in an extruder, extruded into a film, and cooled on a rotary cooling drum to obtain an unstretched film. This unstretched film is then uniaxially or biaxially stretched to obtain the desired film. The biaxially stretched film can be obtained by: sequentially biaxially stretching a longitudinally or transversely uniaxially stretched film in either the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in both the longitudinal and transverse directions.

[0041] In this invention, the stretching temperature during polyester film stretching is preferably set above the secondary transformation point (Tg) of the polyester. It is preferable to stretch the film by 1 to 8 times, particularly 2 to 6 times, along both the longitudinal and transverse directions.

[0042] The thickness of the aforementioned polyester film is preferably 12–50 μm, more preferably 15–38 μm, and even more preferably 19–33 μm. If the film thickness is 12 μm or more, there is no concern about deformation due to heat during film production, the processing of the release layer, or the molding of ceramic green sheets, which is preferable. On the other hand, if the film thickness is 50 μm or less, the amount of waste film after use will not be excessive, which is preferable in terms of reducing environmental impact.

[0043] The aforementioned polyester film substrate can be a single layer, but is preferably a multilayer consisting of two or more layers. The following explanation describes a scheme where a layer forming one surface of the aforementioned polyester film substrate is designated as surface layer A, a layer forming the other surface is designated as surface layer B, and a release layer is stacked on surface layer A. Surface layer A preferably does not contain inorganic particles. On the other hand, surface layer B preferably contains particles, etc. As a layered configuration of the release film, when the layer on the side coated with the release layer is designated as surface layer A, the layer on the opposite side is designated as surface layer B, and the intermediate layer other than these is designated as layer C, layer configurations in the thickness direction such as release layer / A / B or release layer / A / C / B can be given. Of course, layer C can be composed of multiple layers.

[0044] Surface layer B can be a layer formed together with surface layer A using polyester as the main constituent resin through a so-called co-extrusion process, but it can also be provided as a coating layer on the opposite surface of the polyester film to surface layer A. In the case where surface layer B is the aforementioned coating layer, surface layer B is preferably composed of binder resin and particles, and in this case, surface layer B can also be referred to as an easy-slip coating layer.

[0045] In the polyester film substrate of this invention, the surface layer A of the surface on which the release layer is formed is preferably substantially free of inorganic particles. In this case, the average surface roughness (Sa) of the area of ​​surface layer A is preferably 7 nm or less. If Sa is 7 nm or less, it is preferable that pinholes or the like are less likely to occur during the molding of the stacked ultrathin ceramic green sheet. It can be said that the smaller the average surface roughness (Sa) of the area of ​​surface layer A, the better, but it can also be 0.1 nm or more. Here, when the anchoring coating or the like described later is provided on surface layer A, it is preferable that the coating is substantially free of inorganic particles, and it is preferable that the average surface roughness (Sa) of the area after the coating is stacked falls within the aforementioned range. In this invention, "substantially free of inorganic particles" means a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when the inorganic element is quantitatively analyzed by fluorescent X-rays. This is because even without actively adding inorganic particles to the film, there is a possibility that contaminants from foreign matter, raw material resins, or contaminants adhering to the production line or equipment during the film manufacturing process may detach and mix into the film.

[0046] In the polyester film substrate of the present invention, the surface layer B, which is opposite to the side where the release layer is formed, preferably contains particles from the viewpoint of film slippage and ease of air removal, and particularly preferably uses silica particles and / or calcium carbonate particles. The particle content is preferably 5000 to 15000 ppm in total in the surface layer B. In this case, the regional average surface roughness (Sa) of the film in the surface layer B is preferably in the range of 1 to 40 nm, more preferably in the range of 5 to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5000 ppm or more, and Sa is 1 nm or more, when the film is rolled into a roll, air can be evenly dispersed, resulting in a good rolled appearance and good planarity, thus becoming suitable for manufacturing ultrathin ceramic green sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15000 ppm or less, and Sa is 40 nm or less, lubricant aggregation is less likely to occur, and coarse protrusions are not formed; therefore, the quality is stable and preferred when manufacturing ultrathin ceramic green sheets.

[0047] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used as particles in surface layer B. From the viewpoints of transparency and cost, silica particles and / or calcium carbonate particles are more preferred. Other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Furthermore, heat-resistant organic particles include cross-linked polyacrylic acid particles, cross-linked polystyrene particles, and benzoguanamine-based particles. Moreover, when using silica particles, porous colloidal silica is preferred. When using calcium carbonate particles, from the viewpoint of preventing lubricant detachment, lightweight calcium carbonate with a surface treatment using a polyacrylic acid-based polymer is preferred.

[0048] The average particle size of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, particularly preferably 0.5 μm or more and 1.0 μm or less. An average particle size of 0.1 μm or more is preferred because it results in good sliding properties of the release film. Furthermore, an average particle size of 2.0 μm or less is preferred because it eliminates concerns about pinholes in the ceramic green sheet caused by coarse particles on the surface of the release layer.

[0049] The surface layer B described above may contain two or more types of particles with different raw materials. Alternatively, it may contain the same type of particles but with different average particle sizes.

[0050] When the aforementioned slip-resistant coating layer is provided as surface layer B on the opposite side of surface layer A, it is preferable to use an online coating method during the film-making process of polyester film. When the slip-resistant coating layer is provided, for the same reasons as above, the average surface roughness (Sa) of the area of ​​surface layer B based on the slip-resistant coating layer is preferably in the range of 1 to 40 nm.

[0051] The film thickness of the aforementioned surface layer B based on the slip-resistant coating is preferably 2 μm or less, more preferably 1 μm or less, even more preferably 0.8 μm or less, and particularly preferably 0.5 μm or less. A film thickness of 2 μm or less is preferred as it eliminates concerns about adhesion.

[0052] The binder resin constituting the slip coating layer is not particularly limited. Specific examples of polymers include polyester resins, acrylic resins, urethane resins, polyvinyl alcohol (polyvinyl alcohol, etc.), polyalkylene glycols, polyalkylimides, methylcellulose, hydroxycellulose, starches, etc. Among these, polyester resins, acrylic resins, and urethane resins are preferred from the viewpoint of particle retention and adhesion. Furthermore, acrylic resins are particularly preferred when considering the hardness of the slip coating layer. Other preferred binder resins constituting the slip coating layer on a polyester substrate film include polyester resins and urethane resins. Copolyesters are preferred as polyester resins. It should be noted that polyester resins can be modified with polyurethane. Polycarbonate polyurethane resins are an example of urethane resins. Furthermore, acrylic resins, polyester resins, and polyurethane resins can be used in combination, as well as in combination with the other binder resins mentioned above.

[0053] In this invention, in order to form a cross-linked structure in the slip-resistant coating layer that forms surface layer B, the slip-resistant coating layer may be formed by including a cross-linking agent. By including a cross-linking agent, the hardness of the slip-resistant coating layer can be further improved. Specific cross-linking agents include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based agents. In particular, oxazoline-based and carbodiimide-based cross-linking agents are especially preferred in terms of improving cross-linking density. In addition, catalysts or the like can be used appropriately as needed to promote the cross-linking reaction.

[0054] In order to impart sliding properties to the surface layer B, the slip-resistant coating layer preferably contains lubricant particles. The particles can be inorganic or organic, without particular limitation. Examples include (1) inorganic particles such as silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium dioxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrohalogenite, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, and barium sulfate; and (2) organic particles such as acrylic or methacrylic acid, vinyl chloride, vinyl acetate, nylon, styrene / acrylic acid, styrene / butadiene, polystyrene / acrylic acid, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester. In order to impart appropriate sliding properties to the coating layer, silica is particularly preferred.

[0055] In the layer on the side where the above-mentioned release layer is provided, namely surface layer A, from the viewpoint of reducing pinholes, it is preferable not to use recycled raw materials to prevent the mixing of particles such as lubricant.

[0056] The thickness ratio of the layer on the side where the release layer is provided, i.e., the surface layer A, is preferably 20% or more and 50% or less of the total thickness of the substrate film. If it is 20% or more, the interior of the film is less susceptible to the influence of particles contained in the surface layer B, etc., and the average surface roughness Sa of the region is more likely to meet the above-mentioned range, which is preferable. If it is 50% or less of the total thickness of the substrate film, the proportion of recycled raw materials used in the co-extruded surface layer B and the intermediate layer C can be increased, and the environmental impact is reduced, which is preferable.

[0057] Furthermore, from an economic point of view, layers other than surface layer A (surface layer B or the aforementioned intermediate layer C) can use 50-90% by mass of recycled materials from film scraps or PET bottles. In this case, it is also preferable that the type, amount, particle size, and average surface roughness (Sa) of the lubricant contained in surface layer B meet the above-mentioned ranges.

[0058] In addition, in order to improve the adhesion of subsequent coatings such as release layers, a coating may be applied to the surface of surface layer A and / or surface layer B before stretching or after uniaxial stretching in the film forming process, or corona treatment may be performed.

[0059] However, it is preferable that surface layers A and B do not have an antistatic layer, and it is also preferable that surface layers A and B do not contain an antistatic agent. If an intermediate layer C is present, it is preferable that intermediate layer C also does not contain an antistatic agent. By forming a structure that does not have an antistatic layer or an antistatic agent, a release film with low peel strength can be provided inexpensively.

[0060] (Structure of the release layer)

[0061] The release layer of the present invention preferably does not contain an antistatic agent, and the release layer is formed by curing a composition comprising at least a melamine-based compound and a polyorganosiloxane.

[0062] For the release layer of the present invention, in order to suppress the deformation of the release layer during peeling and to achieve low and uniform peel force, it is preferable to have a high crosslinking density and a high elastic modulus. Here, the elastic modulus of the release layer refers to the elastic modulus in the compression direction. In addition, forming a release layer with a high crosslinking density and a high elastic modulus suppresses the increase in charge over time when the film is stored in a roll, which is therefore preferable. If the elastic modulus of the release layer is increased, the sliding property between the release layer and the contacting surface layer B is improved (it becomes easier to slide) when stored in a roll. If the release layer becomes easier to slide, the pressure applied to the film surface in the vertical direction becomes easier to escape in the horizontal direction. Therefore, the adhesion force with the surface layer B when stored in a roll can be reduced, and charge can be suppressed, which is also preferable.

[0063] It was further found that increasing the crosslinking density of the release layer is important for suppressing charge. Increasing the crosslinking density of the release layer facilitates electron migration between the melamine resins within the release layer, making them less prone to charging, which is therefore preferable. To increase the crosslinking density of the release layer, it is preferable to increase the reactivity of the melamine-based compound. Details regarding highly reactive melamine-based compounds are described later.

[0064] The melamine-based compound used in the release layer of this invention can be any common substance without particular limitation. Preferably, it is obtained by condensing melamine with formaldehyde, and has one or more triazine rings and hydroxymethyl and / or alkoxymethyl groups in one molecule. Specifically, it is preferable to obtain a hydroxymethyl melamine derivative by condensing melamine with formaldehyde, and then etherify the obtained hydroxymethyl melamine derivative by undergoing a dehydration condensation reaction with a lower alcohol such as methanol, ethanol, isopropanol, or butanol. Examples of hydroxymethylated melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. One or more of these compounds can be used.

[0065] To improve the reactivity of melamine-based compounds and increase the elastic modulus of the release layer, hexahydroxymethyl melamine and hexaalkoxymethyl melamine, which have more crosslinking sites per molecule, are preferred, but hexaalkoxymethyl melamine with superior reactivity is more preferred, and hexamethoxymethyl melamine is particularly preferred. Here, hexahydroxymethyl melamine refers to a compound in which X is hydroxymethyl (-CH2-OH) in formula (a) below. Hexaalkoxymethyl melamine refers to a compound obtained by dehydrating a hydroxymethyl melamine derivative with an alcohol, where X is (-CH2-OR, R is an alkyl group having 1 to 4 carbon atoms). Hexamethoxymethyl melamine refers to a compound where X is (-CH2-OMe).

[0066]

[0067] In (a) above, X can be the same or different. Similarly, R can be the same or different. Additionally, X can also be (-H).

[0068] The melamine-based compounds used in this invention are preferably mixtures of multiple compounds rather than single compounds. The structures of the main components of the melamine-based compounds can be broadly classified into three types: all-ether type (X = -CH2-OR, R is an alkyl group with 1 to 4 carbon atoms), hydroxymethyl type (X = -CH2-OH), and imino type (X = -H). From a reactivity point of view, all-ether type and hydroxymethyl type are preferred, more preferably all-ether type. Among all-ether type compounds, hexamethoxymethyl melamine (CAS No. 3089-11-0) with R being methyl is most preferred. The higher the content of hexamethoxymethyl melamine in the melamine-based compound, the more reactive and elastically moduli the release layer can be formed.

[0069] In the melamine-based compound used in the release layer of this invention, the weight-average molecular weight is preferably 250 or more and 1000 or less. More preferably, it is 300 or more and 900 or less, and even more preferably 400 or more and 800 or less. If the weight-average molecular weight is 1000 or less, the crosslinking reaction is easier to carry out, and a film with a higher crosslinking density can be formed, resulting in a release layer with easy peeling and low charge, which is therefore preferred. If the weight-average molecular weight is 250 or more, the crosslinking density will not become too high, and curling will not worsen, which is also preferred. It should be noted that the weight-average molecular weight in this specification is a value converted from standard polystyrene measured by gel permeation chromatography (GPC).

[0070] The weight-average molecular weight of 250-1000 for melamine-based compounds refers to the presence of a large number of mononuclear bodies in the melamine-based compounds used in this invention. Compared to polynuclear bodies formed by the condensation of two or more melamine derivatives, mononuclear bodies have more crosslinking sites and superior reactivity, thus enabling the formation of a release layer with high crosslinking density and excellent peelability. A higher content of mononuclear bodies is preferred, and melamine-based compounds consisting solely of mononuclear bodies are most preferably used.

[0071] Weight-average molecular weight can also be expressed as weight-average degree of polymerization. The weight-average degree of polymerization of the melamine-based compound used is preferably 1.7 or less, more preferably 1.5 or less, and even more preferably 1.3 or less; the lower the value, the more suitable it is for use. If the weight-average degree of polymerization is 1.7 or less, the content of mononuclear bodies in the melamine-based compound increases, resulting in excellent reactivity and peelability, and it can form a release layer that is not easily charged, thus it is preferred. It should be noted that the weight-average degree of polymerization in this specification is a value calculated based on the weight-average molecular weight obtained by gel permeation chromatography and converted from standard polystyrene.

[0072] Melamine compounds sometimes contain imino groups (-NH2-) or polynuclear groups during their synthesis. Even when these melamine derivatives are mixed, as long as the weight-average molecular weight (i.e., weight-average degree of polymerization) of the melamine compounds is within the above-mentioned range, their reactivity is excellent and they can be used separately.

[0073] In the release layer of the present invention, the melamine-based compound preferably comprises 80% by mass or more and 99.9% by mass or less, more preferably 90% by mass or more and 99.9% by mass or less, and even more preferably 95% by mass or more and 99.9% by mass or less, relative to the solid component of the release layer forming composition. By comprising 80% by mass or more of the melamine-based compound, the release layer can obtain a high crosslinking density due to the self-crosslinking of the melamine-based compound, thus becoming a release layer with a high elastic modulus, which is preferred. In this case, a considerable portion of the solvent and acid catalyst in the solid component of the release layer forming composition will evaporate during the drying process; therefore, it can be substantially considered as the total value of the solid component of the melamine-based compound and the release agent.

[0074] To promote the crosslinking reaction of melamine-based compounds, an acid catalyst is preferably added to the release layer of the present invention. More preferably, the acid catalyst is added to the composition for forming the release layer and then coated and cured. A sulfonic acid catalyst is preferably used as the acid catalyst.

[0075] As a sulfonic acid catalyst, p-toluenesulfonic acid, xylenesulfonic acid, isopropylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, trifluoromethanesulfonic acid, etc. can be used. From a reactivity point of view, p-toluenesulfonic acid is particularly suitable.

[0076] The sulfonic acid catalyst used in this invention can also be a commercially available product. Examples of commercially available products include DRYER 900 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd.), NACURE DNNDSA series (dinonylnaphthalene disulfonic acid, manufactured by Kusunoki Chemical Co., Ltd.), DNNSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusunoki Chemical Co., Ltd.), DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusunoki Chemical Co., Ltd.), and p-TSA series (p-toluenesulfonic acid, manufactured by Kusunoki Chemical Co., Ltd.), etc.

[0077] Compared to other acid catalysts such as carboxylic acid catalysts, sulfonic acid catalysts have higher acidity and better reactivity, thus enabling the processing of the release layer at lower temperatures. Therefore, they can suppress the reduction in film planarity and deterioration of the wound appearance caused by heat during processing, making them a preferred choice.

[0078] The amount of acid catalyst added is preferably 0.1 to 10% by mass relative to the melamine-based compound contained in the release layer. More preferably, it is 0.5 to 8% by mass. Even more preferably, it is 0.5 to 5% by mass. If it is 0.1% by mass or more, the curing reaction becomes easier to carry out, which is preferred. On the other hand, if it is 10% by mass or less, there is no concern about the acid catalyst transferring onto the molded ceramic green sheet and no concern about causing adverse effects, which is preferred.

[0079] The release agent (additive for improving the release properties of the release layer) used in the release layer of the present invention is not particularly limited, and general substances can be used. Polyorganosiloxanes having functional groups such as carboxyl, hydroxyl, amino, and thiol groups that can react with melamine-based compounds are preferred. Among these, polyorganosiloxanes having hydroxyl and carboxyl groups are more preferred, and from the viewpoint of peelability and antistatic properties, polyorganosiloxanes containing carboxyl groups are most preferred. Polyorganosiloxane structures having a polydimethylsiloxane structure (abbreviated as PDMS) can be suitable.

[0080] By using a polyorganosiloxane containing carboxyl groups as the release agent, the release agent does not exhibit strong interactions with melamine-based compounds during the drying process, making it easier to orient on the surface of the release layer and resulting in good peelability. Therefore, by using a polyorganosiloxane containing carboxyl groups, it is preferable that even a small amount of release agent can meet the peelability requirements. Furthermore, the ease with which it orients on the surface of the release layer improves the sliding properties of the release layer surface and makes it less prone to charging, which is also preferable.

[0081] The carboxyl group can be introduced into the single end, the two ends, or the side chain of the polyorganosiloxane. Furthermore, it can be introduced into one or more locations.

[0082] For carboxyl-modified polyorganosiloxanes, carboxyl groups can be directly bonded to the silicon atoms of the polyorganosiloxane, or they can be bonded to the polyorganosiloxane using alkyl or aryl groups. However, those formed by bonding carboxyl groups to polyorganosiloxanes using organic groups with repeating structures, such as polyethers, polyesters, and polyurethanes, are not preferred.

[0083] As a functional group introduced into the polyorganosiloxane, which is a mold release agent, a molecule may have other functional groups besides the carboxyl group, but it is preferred to have only the carboxyl group. If functional groups other than the carboxyl group are included, the intermolecular interaction with melamine-based compounds will increase to a greater extent than desired, which may make it difficult to orient on the surface of the mold release layer, so it is not preferred.

[0084] Modified polyorganosiloxanes, such as those containing hydroxyl groups that exhibit strong interactions with melamine-based compounds, react rapidly with these compounds during the drying process. This makes it difficult for them to orient on the surface of the release layer, sometimes resulting in poor release properties. Therefore, to achieve sufficient release properties, the amount added must be increased. However, this reduces the elastic modulus of the release layer, raising concerns about increased peel force. Furthermore, increasing the amount of polyorganosiloxane may worsen the coatability during ceramic green sheet molding, making it less desirable.

[0085] The weight-average molecular weight of the carboxyl-containing polyorganosiloxane used in this invention is preferably 40,000 or less. More preferably, it is 30,000 or less. If the weight-average molecular weight is 40,000 or less, the carboxyl-containing polyorganosiloxane is prone to segregation on the surface of the release layer, which is preferred from the viewpoint of peelability and charge.

[0086] As mentioned above, polyorganosiloxanes containing carboxyl groups are more preferably polydimethylsiloxanes containing carboxyl groups. Examples of polydimethylsiloxanes containing carboxyl groups include X22-3701E (side-chain carboxyl-modified polydimethylsiloxane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), X22-3710 (single-terminal carboxyl-modified polydimethylsiloxane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), X22-162C (two-terminal carboxyl-modified polydimethylsiloxane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), BY16-750 (two-terminal carboxyl-modified polydimethylsiloxane, manufactured by DOW CORNING TORAY Co., Ltd.), BY16-880 (side-chain carboxyl-modified polydimethylsiloxane, manufactured by DOW CORNING TORAY Co., Ltd.), and Magnasoft 800L (two-terminal carboxyl-modified polydimethylsiloxane, manufactured by Momentive Co., Ltd.).

[0087] The carboxyl-containing polydimethylsiloxane used in this invention can be an acrylic resin formed by introducing polydimethylsiloxane as a side chain onto an acrylic backbone containing carboxyl groups. CIMAC (registered trademark) US-350, US-352, and US-380 (the above, manufactured by Toa Synthetic Co., Ltd.) are examples of acrylic resins formed by introducing polydimethylsiloxane as a side chain onto an acrylic backbone containing carboxyl and hydroxyl groups in one molecule. Alternatively, an acrylic resin can also be formed by introducing polydimethylsiloxane as a side chain onto an acrylic backbone containing carboxyl and hydroxyl groups in one molecule. CIMAC (registered trademark) US-450 and US-480 (the above, manufactured by Toa Synthetic Co., Ltd.) are examples of acrylic resins formed by introducing polydimethylsiloxane as a side chain onto an acrylic backbone containing carboxyl and hydroxyl groups in one molecule.

[0088] In the release layer of the present invention, the release agent preferably comprises 0.05% by mass or more and 5% by mass or less relative to the solid content of the release layer forming composition. More preferably, it comprises 0.1% by mass or more and 3% by mass or less, and even more preferably, it comprises 0.1% by mass or more and 1% by mass or less. If it is 0.05% by mass or more, not only is the peelability improved, but the release layer also becomes easier to slide and less prone to charging, which is preferred. On the other hand, if it is 5% by mass or less, the overall elastic modulus of the release layer is not excessively reduced, which is preferred. In addition, if it is 5% by mass or less, it is also preferred from the perspective of not worrying about the deterioration of the coatability during the molding of ceramic green sheets. In this case, for the solid content of the release layer forming composition, a considerable portion of the solvent and acid catalyst will evaporate during the drying process, so it can be substantially regarded as the total value of the solid content of the melamine-based compound and the release agent.

[0089] The release layer of the present invention may contain particles with a particle size of 1 μm or less, but from the viewpoint of generating pinholes, it is preferable not to contain particles or the like that form protrusions.

[0090] In the release layer of the present invention, other additives may be added as long as they do not impair the effects of the present invention, but it is preferable that it does not contain antistatic agents. By forming a release layer that does not contain antistatic agents, the compatibility with release agents and melamine-based compounds is reduced, and there is no concern about the formation of aggregates that would compromise the smoothness of the release layer, which is therefore preferable. In addition, the release layer can be formed more economically, which is also preferable.

[0091] (Other features)

[0092] In this invention, the thickness of the release layer can be set according to its intended use and is not particularly limited. Preferably, the weight of the cured release coating layer can be in the range of 0.01 to 1.0 μm, more preferably 0.05 to 0.8 μm, even more preferably 0.1 to 0.6 μm, and even more preferably 0.1 to 0.4 μm. A release layer thickness of 0.01 μm or more is preferred as it provides better peel performance. Furthermore, a thickness of 1.0 μm or less is preferred as it shortens the curing time, maintains the planarity of the release film, and suppresses uneven thickness of the ceramic green sheet. Additionally, a thinner release layer is less prone to charging, which is also preferred.

[0093] To prevent defects from being generated in the ceramic green sheet coated / formed thereon, the release layer of the release film of the present invention is preferably flat, with a preferred average surface roughness (Sa) of 7 nm or less and a maximum protrusion height (P) of 100 nm or less. More preferably, the average surface roughness of the region is 5 nm or less and the maximum protrusion height is 80 nm or less.

[0094] For example, the maximum protrusion height (P) can be below 45 nm.

[0095] If the surface roughness of the region is below 7 nm and the maximum protrusion height is below 100 nm, then no defects such as pinholes are generated during the formation of ceramic green sheets, resulting in a good yield, which is preferred. It can be said that the smaller the average surface roughness (Sa), the better, but it can be above 0.1 nm or above 0.3 nm. Similarly, it can be said that the smaller the maximum protrusion height (P), the better, but it can be above 1 nm or above 3 nm.

[0096] The release film of the present invention preferably uses a substrate film with a highly planarized surface layer A, and the thickness of the release layer is less than 0.5 μm, and further less than 0.2 μm, which also makes the surface of the release layer smooth. Therefore, even when using a release layer with a highly reactive melamine-based compound, curling can be suppressed. In addition, the amount of solvent and resin used can be reduced, which is environmentally friendly and allows for the inexpensive production of release films for ultra-thin ceramic green sheet molding.

[0097] For the release film of the present invention, the peeling force when peeling off the ceramic green sheet is preferably 0.5 mN / mm or more and 2.0 mN / mm or less. More preferably, it is 0.5 mN / mm or more and 1.5 mN / mm or less. If the peeling force is 0.5 mN / mm or more, there is no concern that the peeling force will be too light and the ceramic green sheet will float during transport, which is preferable. If the peeling force is 2.0 mN / mm or less, there is no concern that the ceramic green sheet will be damaged during peeling, which is preferable. For example, even in the case of an extremely thin product with a required ceramic green sheet thickness of 0.2 to 1.0 μm, the release film of the present invention can peel off the ceramic green sheet well.

[0098] For the release film of the present invention, the static friction coefficient when the release layer overlaps with the surface layer B is preferably less than 0.30, for example, less than 0.25, and more preferably less than 0.25. If the static friction coefficient is less than 0.30, the adhesion between the release layer and the surface layer B is reduced, thus suppressing the charging caused by edge curling, vibration during transportation, etc., when the film is stored in a roll, which is preferable. The smaller the static friction coefficient, the better it suppresses charging, which is preferable, but for the sake of rollability, it is preferably 0.01 or more, and more preferably 0.03 or more.

[0099] For the release film of the present invention, the curling after heating at 80°C for 5 minutes without applying tension is preferably 3 mm or less, more preferably 1 mm or less. Of course, it is also preferable to have no curling at all. By setting it to 3 mm or less, there is less curling when forming it into a ceramic green sheet and printing electrodes, which can improve printing accuracy, and therefore it is preferred.

[0100] In this invention, the method for forming the release layer is not particularly limited, and the following method can be used: A coating solution containing a release resin is spread on one side of a polyester film substrate by coating or the like; the solvent is removed by drying; and then the film is heated and dried, and then heat-cured. The drying temperature for solvent drying and heat curing is preferably 100°C or higher and 180°C or lower, more preferably 100°C or higher and 160°C or lower, and most preferably 100°C or higher and 140°C or lower. The heating time is preferably 30 seconds or lower, more preferably 20 seconds or lower. Temperatures below 180°C maintain the planarity of the film, minimizing concerns about uneven thickness of the ceramic green sheet, and are therefore preferred. Temperatures below 140°C allow for processing without compromising the planarity of the film, further reducing concerns about uneven thickness of the ceramic green sheet, and are therefore particularly preferred. Temperatures below 100°C result in insufficient curing of the melamine, leading to a decrease in the elastic modulus of the release layer, and are therefore not preferred.

[0101] In this invention, there are no particular limitations on the coating liquid used when applying the release coating layer, but it is preferable to add a solvent with a boiling point of 90°C or higher. By adding a solvent with a boiling point of 90°C or higher, sudden boiling during drying can be prevented, the coating film can be leveled, and the smoothness of the dried coating film surface can be improved. As for the amount added, it is preferable to add about 10 to 80% by mass relative to the total coating liquid.

[0102] As for the coating method of the above-mentioned coating liquid, any known coating method can be applied, such as gravure coating, reverse roll coating and other roll coating methods, bar coating such as wire rod coating, mold coating, spray coating, air knife coating and other methods that have been known for a long time.

[0103] (Ceramic green sheets and ceramic capacitors)

[0104] Typically, a multilayer ceramic capacitor has a cuboid ceramic body. Inside the ceramic body, a first internal electrode and a second internal electrode are alternately arranged along the thickness direction. The first internal electrode is exposed at a first end face of the ceramic body. A first external electrode is located at 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 at a second end face of the ceramic body. A second external electrode is located at the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0105] The release film for manufacturing ceramic green sheets of the present invention is used to manufacture such multilayer ceramic capacitors. For example, it can be manufactured as follows: First, using the release film of the present invention as a carrier film, a ceramic slurry for forming the ceramic body is coated and dried. The thickness of the ceramic green sheet is gradually reduced to an extremely thin 0.2–1.0 μm. A conductive layer for forming the first or second internal electrode is printed on the coated and dried ceramic green sheet. The ceramic green sheet, the ceramic green sheet with the conductive layer for forming the first internal electrode, and the ceramic green sheet with the conductive layer for forming the second internal electrode are appropriately stacked and pressed to obtain a master laminate. The master laminate is cut into multiple pieces to produce a green ceramic body. The green ceramic body is fired to obtain a ceramic body. Then, by forming the first and second external electrodes, the multilayer ceramic capacitor can be completed.

[0106] Example

[0107] The present invention will be further described in detail below with reference to examples, but the present invention is not limited to these examples. The characteristic values ​​used in the present invention are evaluated using the methods described below.

[0108] (Surface roughness)

[0109] The values ​​are measured using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. The average surface roughness (Sa) of the area is the average of 5 measurements, and the maximum protrusion height (P) is the maximum value of 5 measurements taken 7 times, after removing the maximum and minimum values.

[0110] (Measurement conditions)

[0111] • Measurement mode: WAVE mode

[0112] • Objective lens: 10x

[0113] ·0.5× lens barrel

[0114] • Measurement area: 936 μm × 702 μm

[0115] (Analysis conditions)

[0116] • Horizontal correction: 4 corrections

[0117] • Interpolation processing: Full interpolation

[0118] (Evaluation of the coatability of ceramic slurry)

[0119] Slurry composition I, containing the following materials, was stirred and mixed for 10 minutes, and then dispersed for 10 minutes using a bead mill with 0.5 mm diameter zirconia beads to obtain a primary dispersion. Then, slurry composition II, containing the following materials, was added to the primary dispersion to achieve a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0. The mixture was then dispersed twice for 10 minutes each time using a bead mill with 0.5 mm diameter zirconia beads to obtain a ceramic slurry.

[0120] (Slurry Composition I)

[0121]

[0122] (Slurry Composition II)

[0123] 39.6 parts by weight of toluene

[0124] 39.6 parts by weight of ethanol

[0125] 3.3 parts by weight of dioctyl phthalate

[0126] Polyvinyl butyral (S-LEC BM-S manufactured by Sekisui Chemicals Co., Ltd.) 16.3 parts by weight

[0127] 0.5 parts by weight of 1-ethyl-3-methylimidazolium ethyl sulfate

[0128] Next, the release surface of the obtained release film sample was coated with the dried slurry to a thickness of 1.0 μm using an applicator. After drying at 60°C for 1 minute, the coatability was evaluated according to the following criteria.

[0129] ○: No dents or depressions and can be coated on the entire surface.

[0130] ×: Visible defects such as dents.

[0131] (Evaluation of pinholes in ceramic raw shards)

[0132] Similar to the evaluation of the coatability of the aforementioned ceramic slurry, a 1 μm thick ceramic green sheet was formed on the release surface of the release film. Next, the release film containing the ceramic green sheet was peeled off to obtain the ceramic green sheet. In the central region of the obtained ceramic green sheet along the width direction, at a depth of 25 cm... 2 Within the specified range, shine light on the opposite side of the ceramic slurry coating surface and observe the appearance of pinholes visible through the light. Make a visual judgment according to the following criteria.

[0133] ○: No pinholes were generated.

[0134] △: Almost no pinholes were produced.

[0135] ×: Produces a large number of pinholes

[0136] (Evaluation of the peelability of ceramic raw shards)

[0137] Slurry composition I, containing the following materials, was stirred and mixed for 10 minutes. Then, using a bead mill, it was dispersed for 10 minutes with zirconia beads of 0.5 mm diameter to obtain a primary dispersion. Next, slurry composition II, containing the following materials, was added to the primary dispersion to achieve a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0. The mixture was then dispersed twice, for 10 minutes each time, using a bead mill with zirconia beads of 0.5 mm diameter to obtain a ceramic slurry.

[0138] (Slurry Composition I)

[0139]

[0140] (Slurry Composition II)

[0141] 39.6 parts by weight of toluene

[0142] 39.6 parts by weight of ethanol

[0143] 3.3 parts by weight of dioctyl phthalate

[0144] Polyvinyl butyral (S-LEC BM-S manufactured by Sekisui Chemicals Co., Ltd.) 16.3 parts by weight

[0145] 0.5 parts by weight of 1-ethyl-3-methylimidazolium ethyl sulfate

[0146] Next, the obtained release film sample was coated with a 1.0 μm thick layer of dried slurry using an applicator on the release surface, and dried at 60°C for 1 minute to form the ceramic green sheet onto the release film. After eliminating static electricity from the obtained release film with the ceramic green sheet using a destatic motor (KEYENCE CORPORATION, SJ-F020), peeling was performed using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3, load sensor 0.1N) at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 10 m / min. As the peeling direction, double-sided adhesive tape (Nitto Denko Co., Ltd., No. 535A) was adhered to the SUS plate attached to the peel tester, and the release film was fixed on it by bonding the ceramic green sheet side to the double-sided tape. Peeling was performed by stretching the release film side. The average peel force of the measured values ​​with peel distances of 20 mm to 70 mm was calculated and taken as the peel force. The peel force was measured a total of 5 times, and the average value was used for evaluation. The peel force value was judged according to the following criteria.

[0147] ◎: Above 0.5mN / mm and below 1.5mN / mm

[0148] ○: Greater than 1.5 mN / mm and less than 2.0 mN / mm

[0149] ×: Below 0.5 mN / mm, above 2.0 mN / mm

[0150] (Evaluation of the curling of the release film)

[0151] Cut the release film sample into 10cm × 10cm pieces and heat-treat it in a hot air oven at 80°C for 5 minutes without applying tension. Afterward, remove it from the oven, allow it to cool to room temperature, and place the sample on a glass plate with the release side facing up. Measure the height of the portion that floats above the four corners of the glass plate. The average of these four corner float measurements is taken as the curling amount. Evaluate the curling performance according to the following criteria.

[0152] ◎: Curl less than 1mm, almost no curl

[0153] ○: Curl greater than 1mm and less than 3mm, slight curling is visible.

[0154] ×: Curl greater than 3mm, curl is visible.

[0155] (Method for determining weight-average degree of polymerization)

[0156] Analysis conditions

[0157] Weigh 16 mg of the sample and dissolve it in 8 ml of chloroform. Filter the solution through a 0.2 μm membrane filter and perform GPC analysis on the resulting sample solution under the following conditions.

[0158] Device: TOSOH HLC-8320GPC

[0159] Column: K-G+K-802 (size exclusion limit molecular weight 5×10⁻⁶) 3 +K-801 (exclusion limit molecular weight 1.5×10) 3 (Shodex)

[0160] Solvent: 100% chloroform

[0161] Flow rate: 1.0 ml / min

[0162] Concentration: 0.2%

[0163] Injection volume: 50μL

[0164] Temperature: 40℃

[0165] Detector: RI

[0166] The weight-average molecular weight was calculated from polystyrene, and the weight-average degree of polymerization was calculated based on this value. PStQuick C(TOSOH) from the PStQuick series was used for the polystyrene. Polystyrene molecules with molecular weights significantly exceeding the exclusion limit of the column (Mw2110000, 427000, 37900) added to PStQuick C(TOSOH) were excluded from the preparation of the standard curve.

[0167] (with battery charge)

[0168] Two 10cm x 10cm evaluation samples were prepared by cutting the release film. The two samples were de-electrolyzed using a de-electrode (KEYENCE CORPORATION, SJ-F020) to confirm a voltage of 0kV. The release layer was then brought into contact with surface layer B with the release layer facing upwards. The two samples were then held in place with a weighing paper, and a load of 10.2 kg (10 kPa pressure) was applied from above, maintaining the temperature at 50°C for 48 hours. After 48 hours, the temperature was allowed to return to room temperature (25°C). The two samples were then peeled off, and the charge on the release layer in contact with surface layer B was measured using a digital electrostatic potential meter (KSD-1000, Kasuga Electric Co., Ltd.). The charge measured at this point was evaluated according to the following criteria.

[0169] ◎: The absolute value of the charge is less than 3kV

[0170] ○: The absolute value of the charge is above 3kV and below 5kV

[0171] ×: The absolute value of the charge exceeds 5kV

[0172] (Coefficient of static friction)

[0173] Cut an 8cm × 5cm area from the release film to make a sample film. Fix it to the bottom of a 6cm × 5cm metal cuboid weighing 4.4kg, so that surface layer B appears on the surface. Then, align the 5cm width of the sample film with the 5cm width of the metal cuboid, bend one side of the sample film along its length, and fix it to the side of the metal cuboid with adhesive tape.

[0174] Next, a 20cm × 10cm sample film was cut from the same release film roll. With the release layer surface visible, the longitudinal end was secured to a flat metal plate with adhesive tape. The plate was then placed on the metal plate so that it contacted the test surface of the metal cuboid to which the sample film was adhered. The test was performed at a tensile speed of 100 mm / min, 23°C, and 65% RH. The test was conducted three times, and the average value was used as the static friction coefficient (μs). It should be noted that the tests were performed using an A&D Company Tensilon RTG-1210 universal testing machine.

[0175] (Preparation of polyethylene terephthalate granules (PET(I)))

[0176] As the esterification reactor, a continuous esterification reactor consisting of a three-stage fully mixed tank with a stirring device, a condenser, a raw material inlet, and a product outlet is used. The slurry is continuously fed into the first esterification reactor of the esterification reactor at a rate of 2 tons / hour of TPA, 2 moles of EG (ethylene glycol) relative to 1 mole of TPA, and 160 ppm of antimony trioxide relative to the amount of Sb atoms in the generated PET. The reaction is carried out at atmospheric pressure, with an average residence time of 4 hours and a temperature of 255°C. Next, the reaction product from the first esterification reactor was continuously removed from the system and fed to the second esterification reactor. EG removed by distillation from the first esterification reactor was supplied to the second esterification reactor at a mass ratio of 8% relative to the generated PET. Then, an EG solution containing 65 ppm of magnesium acetate tetrahydrate relative to the generated PET and an EG solution containing 40 ppm of TMPA (trimethyl phosphate) relative to the generated PET were added. The reaction was carried out at atmospheric pressure, with an average residence time of 1 hour and a temperature of 260°C. Next, the reaction product from the second esterification reactor was continuously removed from the system and fed to the third esterification reactor, where it was dispersed using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) at 39 MPa (400 kg / cm²). 2Under pressure, 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm, which has undergone an average of 5 dispersion treatments, and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm and an ammonium salt of polyacrylic acid attached relative to calcium carbonate, were added to form a 10% EG slurry. The mixture was then reacted at atmospheric pressure with an average residence time of 0.5 hours and a temperature of 260°C. The esterification reaction product generated in the third esterification reactor was continuously fed to a three-stage continuous polycondensation reactor for polycondensation. After filtration using a filter made of sintered stainless steel fibers with a 95% split particle size of 20 μm, the product was ultrafiltered and extruded into water. After cooling, it was cut into small flakes to obtain PET flakes with an intrinsic viscosity of 0.60 dl / g (hereinafter referred to as PET(I)). The lubricant content in the PET flakes was 0.6% by mass.

[0177] (Preparation of polyethylene terephthalate granules (PET(II)))

[0178] On the other hand, in the manufacture of the above-mentioned PET(I) flakes, PET flakes with an intrinsic viscosity of 0.62 dl / g that are completely free of particles such as calcium carbonate and silica are obtained (hereafter referred to as PET(II)).

[0179] (Manufacturing of the laminated thin film X1)

[0180] After drying, these PET flakes were melted at 285°C and then melted again at 290°C using different melt extruders. This resulted in two-stage filtration: filters made from 95% sintered stainless steel fibers with a particle size of 15μm and filters made from 95% sintered stainless steel particles with a particle size of 15μm. The filters were then combined in the feed head and layered so that PET(I) became surface layer B (reverse demolding side layer) and PET(II) became surface layer A (demolding side layer). The layers were extruded (cast) into sheets at a speed of 45 m / min. Electrostatic sealing was then performed on a casting drum at 30°C to achieve electrostatic sealing and cooling, yielding unstretched polyethylene terephthalate sheets with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted to PET(I) / (II) = 60% by mass / 40% by mass, calculated based on the discharge rate of each extruder. Next, the unstretched sheet was heated with an infrared heater and stretched 3.5 times longitudinally by the speed difference between the rollers at a roller temperature of 80°C. Then, it was fed into a tenter frame and stretched 4.2 times transversely at 140°C. Next, it was heat-treated at 210°C in a heat-setting zone. Afterward, it underwent a 2.3% relaxation treatment at 170°C transversely to obtain a biaxially stretched polyethylene terephthalate film X1 with a thickness of 31 μm. The surface layer A of the obtained film X1 has a Sa value of 1 nm, and the surface layer B has a Sa value of 28 nm.

[0181] (Manufacturing of laminated thin film X2)

[0182] As the laminated film X2, E5101 (TOYOBOESTER (registered trademark) film, manufactured by Toyobo Co., Ltd.) with a thickness of 25 μm was used. E5101 has a structure containing particles in surface layer A and surface layer B. The Sa of surface layer A and surface layer B of the laminated film X2 is 24 nm.

[0183] (Manufacturing of laminated thin film X3)

[0184] As a polymer feedstock for films, PET resin granules (PETII) with an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60 / 40) of 0.62 dl / g and substantially free of inorganic particles were dried at 135°C for 6 hours under reduced pressure of 133 Pa. The dried granules were then fed to an extruder and melt-extruded into sheets at approximately 280°C. The sheets were then rapidly cooled and solidified on rotating cooling metal rollers with a surface temperature maintained at 20°C to obtain unstretched PET sheets.

[0185] The unstretched PET sheet was heated to 100°C in a heated roller assembly and an infrared heater, and then stretched into a uniaxial PET film by using a roller assembly with a circumferential speed difference along the length direction by 3.5 times.

[0186] Next, the slip coating solution with the composition shown below was applied to one side of the PET film using a bar coater and dried at 80°C for 15 seconds. It should be noted that the coating thickness was adjusted to 0.1 μm after final stretching and drying. Then, in a tenter frame, the film was stretched 4.0 times its original length in the width direction at 150°C. With the width direction length of the film fixed, it was heated at 230°C for 0.5 seconds, followed by a 3% width direction relaxation treatment at 230°C for 10 seconds, resulting in a laminated film X3 with a thickness of 31 μm. The laminated film X3 has the following structure: surface layer A is substantially free of inorganic particles, and a slip coating layer is present on the surface opposite to surface layer A. The aforementioned slip coating layer is surface layer B. The Sa of surface layer A is 1 nm, and the Sa of surface layer B is 2 nm.

[0187] (Composition of the easy-to-slide coating liquid)

[0188]

[0189] (Made by Nissan Chemical, trade name MP2040, average particle size 200nm, solid content concentration 40% by mass)

[0190] Fluorinated surfactant (solid component concentration 10% by mass) 0.30 parts by mass

[0191] (The manufacture of the aforementioned acrylic polyol resins)

[0192] In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen purge tube, 77 parts by weight of methyl methacrylate (MMA), 100 parts by weight of hydroxyethyl methacrylate (HEMA), 33 parts by weight of methacrylic acid (MAA), and 490 parts by weight of isopropanol (IPA) were added. The mixture was heated to 80°C while stirring. The temperature was maintained at 80°C for 3 hours with stirring. Then, 0.5 parts by weight of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide were added. The mixture was then heated to 120°C while purging with nitrogen, and stirred at 120°C for 2 hours.

[0193] Next, a reduced pressure of 1.5 kPa was applied at 120°C to remove unreacted raw materials and solvents, yielding acrylic polyols. The pressure in the flask was restored to atmospheric pressure, cooled to room temperature, and 840 parts by mass of an IPA aqueous solution (50% by mass) was added and mixed. Then, triethylamine was added using a dropping funnel while stirring to neutralize the acrylic polyols until the pH of the solution reached the range of 5.5–7.5, yielding acrylic polyols with a solid content of 20% by mass.

[0194] (Manufacturing of the above-mentioned oxazoline-based crosslinking agent)

[0195] In a flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer, 460.6 parts of isopropanol were added, and the mixture was heated to 80°C while nitrogen was slowly flowing through it. A pre-prepared monomer mixture containing 126 parts of methyl methacrylate, 210 parts of 2-isopropenyl-2-oxazoline, and 84 parts of methoxy polyethylene glycol acrylate, and an initiator solution containing 21 parts of 2,2'-azobis(2-methylbutyronitrile) (manufactured by Japan Hydrazine Industry Co., Ltd., "ABN-E") and 189 parts of isopropanol as a polymerization initiator were added dropwise over 2 hours, and the reaction was continued for another 5 hours after the addition was completed. Nitrogen gas was continuously circulated throughout the reaction to maintain the temperature inside the flask at 80±1°C. The reaction solution was then cooled to obtain a resin with an oxazoline group and a solid content of 25%. The obtained resin with oxazoline groups had an oxazoline group content of 4.3 mmol / g and a number-average molecular weight of 20,000 as determined by GPC (gel permeation chromatography).

[0196] (Example 1)

[0197] A release layer forming agent with the following composition (described as amounts converted to solid components, the same applies hereinafter) was mixed in a mixed solvent of methyl ethyl ketone, toluene, and isopropanol to prepare a coating solution. This coating solution was applied to the surface layer A of a laminated film X1 using reverse gravure printing, resulting in a dried release layer thickness of 0.5 μm. The film was then dried at 130°C for 15 seconds to obtain a release film for manufacturing ultrathin ceramic green sheets. The obtained release film was evaluated for its charge, slip properties, surface roughness, ceramic sheet peelability, ceramic sheet coating properties, curling, and pinholes; the results were satisfactory.

[0198] 99.7 parts by weight of melamine-based compounds

[0199] (All-ether methylated melamine, manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MW-30M, weight-average degree of polymerization 1.3, main component is hexamethoxymethylmelamine)

[0200] 0.3 parts by weight of release agent

[0201] (Single-terminal carboxyl-modified PDMS, manufactured by Shin-Etsu Chemical Co., Ltd., trade name: X22-3710, alkyl group between dimethylsiloxane and carboxyl group)

[0202] p-Toluenesulfonic acid 2.0 parts by weight

[0203] (Examples 2 and 3)

[0204] The contents of melamine-based compounds and single-terminal carboxyl-modified PDMS were changed to the amounts shown in Table 1, and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0205] (Example 4)

[0206] The release agent was changed to a two-terminal carboxyl-modified PDMS (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name: X22-162C, with alkyl groups between dimethylsiloxane and carboxyl groups), and the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0207] (Example 5)

[0208] The content of melamine-based compounds was changed to 99.9 parts by mass, and the release agent was changed to 0.1 parts by mass of carboxyl-modified PDMS (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name: X22-162C, alkyl group between dimethylsiloxane and carboxyl group). Otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0209] (Example 6)

[0210] By changing the release agent to side-chain carboxyl-modified PDMS (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name: X22-3701E, with alkyl groups between dimethylsiloxane and carboxyl groups), an ultra-thin release film for manufacturing ceramic green sheets was obtained in the same manner as in Example 1.

[0211] (Example 7)

[0212] By changing the release agent to COOH-modified copolymer acrylic silicone (manufactured by Toa Synthetic Co., Ltd., trade name: CIMAC US-352), an ultrathin release film for manufacturing ceramic green sheets was obtained in the same manner as in Example 1.

[0213] (Example 8)

[0214] The melamine-based compound was replaced with a fully etherified methylated melamine (manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MW-30, weight-average degree of polymerization 1.5, main component hexamethoxymethylmelamine), and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0215] (Example 9)

[0216] The melamine-based compound was replaced with a fully etherified methylated melamine (manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MW-390, weight-average degree of polymerization 1.0, main component hexamethoxymethylmelamine), and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0217] (Example 10)

[0218] The melamine compound (MW-30M) in Example 1 was replaced with a fully ether-type methylated melamine (weight-average degree of polymerization 1.1, main component hexamethoxymethylmelamine) obtained by recrystallization in isopropanol. Otherwise, the same as in Example 1 was used to obtain a release film for manufacturing ultrathin ceramic green sheets.

[0219] (Examples 11 and 12)

[0220] The thickness of the release layer was changed to the thickness shown in Table 1, and otherwise the same as in Example 1 was obtained to obtain an ultrathin release film for manufacturing ceramic green sheets.

[0221] (Example 13)

[0222] The ultrathin ceramic green sheet is obtained by coating the surface layer A of the laminated film X2, otherwise the same as in Example 1.

[0223] (Example 14)

[0224] The ultrathin ceramic green sheet is obtained by coating the surface layer A of the laminated film X3, otherwise the same as in Example 1.

[0225] (Example 15)

[0226] The release agent used was PDMS modified with single-terminated hydroxyl groups. Otherwise, under the conditions shown in Table 1B, an ultrathin release film for manufacturing ceramic green sheets was obtained in the same manner as in Example 1. The obtained release film had a charge of 3.5 kV, a static friction coefficient of 0.28, and a floatability of 0.7. Furthermore, it exhibited good ceramic sheet coating properties. Additionally, the obtained release film showed peel strength comparable to that obtained in Example 7, with almost no pinholes.

[0227] (Example 16)

[0228] The release agent used was single-terminated amino-modified PDMS. Otherwise, under the conditions shown in Table 1B, a release film for manufacturing ultrathin ceramic green sheets was obtained in the same manner as in Example 1. The obtained release film had a charge of 3.9 kV, a static friction coefficient of 0.26, and a float of 0.7, exhibiting good ceramic sheet coating properties. Furthermore, the obtained release film showed peel strength comparable to that obtained in Example 7, with almost no pinholes.

[0229] (Comparative Example 1)

[0230] The melamine-based compound was replaced with 99.5 parts by weight of imino-type melamine resin (manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MX-730, weight-average degree of polymerization 2.4), and the release agent was replaced with 0.5 parts by weight of PDMS containing polyether-modified hydroxyl groups (manufactured by BYK Japan Co., Ltd., trade name: BYK-377). The coating was then applied to make the film thickness 1.0 μm. Otherwise, the same as in Example 1, a release film for manufacturing ultrathin ceramic green sheets was obtained.

[0231] (Comparative Example 2)

[0232] The melamine-based compound was replaced with an imino-type melamine resin (manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MX-730, weight-average degree of polymerization 2.4), and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0233] (Comparative Example 3)

[0234] The contents of melamine-based compounds and single-terminal carboxyl-modified PDMS were changed to the amounts shown in Table 1, and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0235] (Comparative Example 4)

[0236] The melamine compound was replaced with a hydroxymethyl melamine resin (manufactured by SANWA CHEMICAL CO.,LTD., trade name: NIKALAC MS-11, weight-average degree of polymerization 1.8), and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0237] (Comparative Example 5)

[0238] The melamine compound was replaced with an imino / hydroxymethyl melamine resin (manufactured by SANWA CHEMICALCO.,LTD., trade name: NIKALAC MS-001, weight-average degree of polymerization 5.7), and otherwise, the same release film for manufacturing ultrathin ceramic green sheets was obtained as in Example 1.

[0239] [Table 1A]

[0240]

[0241] [Table 1B]

[0242]

[0243] [Table 1C]

[0244]

[0245] The charge on the release films obtained in the comparative examples is not within the scope of this invention. Therefore, this demonstrates the tendency for minute environmental foreign matter to adhere to the release film during the process.

[0246] Industrial availability

[0247] According to the present invention, the surface of the release layer is highly smooth, which not only allows for the uniform and low-force peeling of ceramic green sheets, but also makes the release layer less prone to charging. Therefore, foreign matter is less likely to adhere to the film, enabling the manufacture of ultra-thin ceramic green sheets with a thickness of less than 1 μm without the defects caused by foreign matter.

Claims

1. A release film for manufacturing ceramic green sheets, wherein when a polyester film is used as a substrate, a layer forming one surface of the substrate is designated as surface layer A, and a layer forming the other surface is designated as surface layer B, the release layer is directly laminated onto surface layer A or laminated onto surface layer A with other layers sandwiched between them. Furthermore, after the release layer is brought into contact with surface layer B and maintained at 50°C and 10 kPa pressure for 48 hours, the charge on the release layer when it is peeled off from surface layer B is below ±5 kV. The release layer is formed by curing a composition containing at least a release agent and a melamine-based compound. The release layer forming composition does not contain an antistatic agent, the melamine-based compound has a weight-average degree of polymerization of 1.7 or less, and the melamine-based compound in the release layer accounts for 80% by mass or more of the solid content of the release layer forming composition.

2. The release film for manufacturing ceramic green sheets according to claim 1, wherein, The static friction coefficient μs when the release layer overlaps with the surface layer B is less than 0.

30.

3. The release film for manufacturing ceramic green sheets according to claim 1, wherein, The release agent contained in the composition for forming the release layer is a polyorganosiloxane containing a carboxyl group.

4. The release film for manufacturing ceramic green sheets according to claim 1, wherein, Surface layer A does not actually contain inorganic particles.

5. The release film for manufacturing ceramic green sheets according to claim 1, wherein, Surface layer B contains particles, at least a portion of which are silica particles and / or calcium carbonate particles, and the total content of particles is 5000 to 15000 ppm relative to the mass of surface layer B.

6. A method for manufacturing ceramic green sheets, comprising a method for manufacturing ceramic green sheets by forming a release film for manufacturing ceramic green sheets according to any one of claims 1 to 5, wherein the formed ceramic green sheets have a thickness of 0.2 μm to 1.0 μm.

7. A method for manufacturing a ceramic capacitor, comprising the method for manufacturing a ceramic green sheet as described in claim 6.

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