CN112672866B

CN112672866B - Release film for producing ceramic green sheet

Info

Publication number: CN112672866B
Application number: CN201980057455.8A
Authority: CN
Inventors: 中谷充晴; 柴田悠介; 应矢量之
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2018-09-03
Filing date: 2019-08-26
Publication date: 2022-03-15
Anticipated expiration: 2039-08-26
Also published as: JP2021079699A; JP6813124B2; CN113246263B; KR102342605B1; SG11202101981QA; JPWO2020050081A1; JP2021091223A; CN113246263A; MY194550A; KR102335931B1; PH12021550425A1; KR20210036404A; WO2020050081A1; CN112672866A; KR20210038720A; JP7092221B2; JP6841375B1; KR102342605B9; SG10202103428TA; MY195706A

Abstract

A release film for producing a ceramic green sheet, which has high smoothness by suppressing deterioration of surface roughness due to aggregation during drying of the release layer and which has excellent releasability by adjusting the amount of a silicone component on the surface of the release layer. A release film for producing a ceramic green sheet, comprising a polyester film as a base material, wherein at least one surface of the base material has a surface layer A substantially free of particles, a release layer is directly laminated on the surface of the surface layer A of the at least one surface or laminated with another layer interposed therebetween, the release layer is obtained by curing a composition containing a binder component and a silicone-based release agent, the Si element ratio on the surface of the release layer is 2.0 at% or more and 10.0 at% or less, the maximum protrusion height (P) on the surface of the release layer is 50nm or less, and the area average roughness (Sa) is 1.5nm or less.

Description

Release film for producing ceramic green sheet

Technical Field

The present invention relates to a release film for manufacturing a ceramic green sheet, and more particularly, to a release film for manufacturing an ultrathin layer, which can manufacture an ultrathin layer ceramic green sheet while suppressing occurrence of process defects due to pinholes and thickness unevenness.

Background

In recent years, with the miniaturization and increase in capacity of multilayer ceramic capacitors (MLCCs), there has been a demand for thinner ceramic green sheets. The multilayer laminated ceramic capacitor can be manufactured by the following method: the ceramic green sheet is produced by applying a slurry containing a ceramic component such as barium titanate and a binder resin to a release film and drying the slurry to mold the ceramic green sheet, printing an electrode on the obtained ceramic green sheet, peeling the ceramic green sheet from the release film, laminating the ceramic green sheets, pressing, degreasing, sintering the laminate, and applying an external electrode.

In order to make the MLCC compact and have a large capacity, it is necessary to make the ceramic green sheet thin, and the thickness thereof is 1.0 μm or less, and further thin. However, when the ceramic green sheet is made thin, there are the following problems: the release film is likely to have defects such as pinholes and cracks due to minute projections and force when peeled from the release film.

In order to solve these problems, as a release film used for molding a ceramic green sheet, a film in which a release layer is provided on a polyester film and the surface of the release layer is highly smoothed has been proposed. Patent document 1 discloses: a surface of a polyester film is provided with a smoothing layer, and then a mold-releasing layer is provided on the smoothing layer. Further, patent document 2 discloses: a release layer containing a (meth) acrylate and a silicone component is formed in a film thickness of 0.3 μm or more. Patent documents 1 and 2 disclose that the arithmetic average roughness Ra of the surface of the release layer can be set to 8nm or less and the maximum protrusion height Rp can be set to 50nm or less.

However, the techniques described in patent documents 1 and 2 have a problem that curing takes time because the resin layers (release layer and smoothing layer) laminated on the polyester film are thick, and the amount of the organic solvent used is also increased, which causes a large environmental load. Further, since the release layer has a large thickness, curling and the like of the obtained release film also become a problem. In the techniques described in these documents, the release layer contains a large amount of silicone-based components, and the elastic modulus of the release layer surface may be low, resulting in unstable peeling.

Further, as a release layer of a release film for molding a ceramic green sheet, the following proposals have been made. Patent document 3 proposes a non-silicone release layer containing no silicone. Patent document 4 proposes a film in which a silicone resin is formed into a release layer. However, there is a problem that the peeling force when peeling the non-silicone release layer and the ceramic green sheet as in the technique described in patent document 3 becomes large, and the ceramic green sheet formed into a thin film is damaged. In addition, in the release layer of the silicone resin as described in patent document 4, the peeling force when peeling the ceramic green sheet is small, but generally, the glass transition temperature of the silicone resin is room temperature or lower, and therefore, the elastic modulus is lowered, and the release layer is deformed at the time of peeling, and there is a problem that the peeling force becomes unstable.

Patent document 5 proposes a release layer containing an alkyd resin, an amino resin, and a modified silicone resin. Further, patent document 6 proposes a release layer containing a melamine resin and a polyorganosiloxane. It has been proposed that a binder for a release layer mainly contains a crosslinked material such as a melamine resin, and a silicone resin is added as a release component to improve the elastic modulus of the release layer and to achieve both deformability and releasability.

However, as described in patent documents 5 and 6, in the case of a release layer containing a binder resin and a silicone resin, since the solubility of the binder resin and the silicone resin in an organic solvent and the surface tension of a solution are greatly different from each other, there is a problem that the compatibility is deteriorated during drying, and the respective resins are aggregated and become protrusions, which deteriorates the surface roughness of the release layer surface. When ceramic green sheets having a thickness of 1.0 μm or less, and further 0.6 μm or less are molded, pinholes and the like are generated even if the surface roughness is slightly deteriorated, and the fraction defective of the multilayer ceramic capacitor obtained is deteriorated, and therefore further smoothness is required.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-177093

Patent document 2: international publication No. 2013/145864

Patent document 3: japanese laid-open patent application No. 2010-144046

Patent document 4: japanese patent laid-open publication No. 2012-207126

Patent document 5: japanese laid-open patent publication No. 9-239913

Patent document 6: japanese patent laid-open publication No. 2017-7226

Disclosure of Invention

Problems to be solved by the invention

In view of the above circumstances, the present invention provides a release film for ceramic green sheet production, which has high smoothness by suppressing deterioration of surface roughness due to aggregation of a binder component and a silicone-based release agent at the time of drying, and which has excellent releasability by adjusting the amount of the silicone-based component on the surface of the release layer, even when the release layer is formed by curing a composition containing the binder component and the silicone-based release agent.

Means for solving the problems

That is, the present invention is configured as follows.

1. A release film for producing a ceramic green sheet, comprising a polyester film as a base material, wherein at least one surface of the base material has a surface layer A substantially free of particles, a release layer is directly laminated or laminated with another layer interposed therebetween on the surface of the surface layer A of at least one surface, the release layer is obtained by curing a composition containing a binder component and a silicone-based release agent, the Si element ratio on the surface of the release layer is 2.0 at% or more and 10.0 at% or less, the maximum protrusion height (P) on the surface of the release layer is 50nm or less, and the area average roughness (Sa) is 1.5nm or less.

2. The release film for producing a ceramic green sheet according to the above 1, wherein the silicone-based release agent is a silicone-based resin having a polyether moiety or a carboxyl group.

3. The release film for producing a ceramic green sheet according to the above 1 or 2, wherein the release layer contains 1 to 15mg/m²Derived from a silicone-based release agent.

4. The release film for manufacturing a ceramic green sheet according to any one of the above 1 to 3, wherein the binder component contains a resin having a long chain alkyl group and/or a silicone skeleton.

5. A method for producing a ceramic green sheet, which comprises molding a ceramic green sheet using the release film for producing a ceramic green sheet according to any one of the above items 1 to 4, wherein the molded ceramic green sheet has a thickness of 0.2 to 1.0 μm.

6. A method for producing a ceramic capacitor, which comprises using the method for producing a ceramic green sheet described in the above 5.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a release film for producing a ceramic green sheet, which has excellent releasability and few defects such as pinholes, even in the production of an ultrathin ceramic green sheet having a film thickness of 0.2 to 1.0 μm, which has excellent releasability, by controlling the amount of a silicone-based component on the surface of a release layer, and which can suppress deterioration in surface roughness due to aggregation of the above components during drying to provide high smoothness, even if the release layer contains at least a binder component and a silicone-based release agent.

Detailed Description

In order to solve the above problems, the present inventors have intensively studied and optimized the drying conditions after coating the release layer and the content of the silicone compound in the release layer, and found that when a ceramic green sheet having a very thin film thickness of 0.2 to 1.0 μm is formed from a release film for producing a ceramic green sheet, the release film is excellent in releasability and less in defects such as pinholes, the release film for producing a ceramic green sheet is obtained by directly laminating a release layer or laminating a release layer with another layer interposed therebetween on at least one surface layer A of a polyester film having at least one surface layer A substantially free of particles, wherein the release layer is obtained by curing a composition containing a binder component and a silicone-based release agent, the maximum protrusion height (P) of the surface of the release layer is 50nm or less and the area average roughness (Sa) is 1.5nm or less, and the Si element ratio of the outermost surface of the mold release layer is 2.0 at% or more and 10.0 at% or less. The present invention will be described in detail below.

(polyester film)

In the present invention, the polyester constituting the polyester film used as the substrate is not particularly limited, and those generally used as a substrate for a release film can be used by film-molding, and crystalline linear saturated polyesters composed of an aromatic dibasic acid component and a diol component are preferable, and for example, polyethylene terephthalate, poly (ethylene 2, 6-naphthalate), polybutylene terephthalate, polytrimethylene terephthalate, or copolymers mainly composed of these resins are more preferable, and a polyester film composed of polyethylene terephthalate is particularly preferable. The polyethylene terephthalate has a repeating unit of preferably 90 mol% or more, more preferably 95 mol% or more, and other dicarboxylic acid component and diol component may be copolymerized in a small amount, but from the viewpoint of cost, it is preferably produced from only terephthalic acid and ethylene glycol. In addition, known additives such as an antioxidant, a light stabilizer, an ultraviolet absorber, a crystallizing agent, and the like may be added within a range in which the effect of the film of the present invention is not inhibited. The polyester film is preferably a biaxially oriented polyester film for the reason of high elastic modulus in both directions.

The intrinsic viscosity of the polyethylene terephthalate film is preferably 0.50 to 0.70dl/g, and more preferably 0.52 to 0.62 dl/g. When the intrinsic viscosity is 0.50dl/g or more, breakage is not likely to occur in the drawing step, and therefore, it is preferable. On the other hand, a value of 0.70dl/g or less is preferred because it is excellent in cuttability and does not cause dimensional defects when cut to a predetermined product width. Further, the raw material pellets are preferably sufficiently vacuum-dried.

The method for producing the polyester film in the present invention is not particularly limited, and conventionally used methods can be used. For example, the polyester can be obtained by melting the polyester with an extruder, extruding the melt into a film, cooling the film with a rotating cooling drum to obtain an unstretched film, and biaxially stretching the unstretched film. The biaxially stretched film can be obtained by a method of subjecting a uniaxially stretched film in the longitudinal direction or transverse direction to successive biaxial stretching in the transverse direction or longitudinal direction, or a method of subjecting an unstretched film to simultaneous biaxial stretching in the longitudinal direction and transverse direction.

In the present invention, the stretching temperature at the time of stretching the polyester film is preferably set to be not less than the secondary transition point (Tg) of the polyester. Preferably, the stretching is performed 1 to 8 times, particularly 2 to 6 times, in each of the longitudinal and transverse directions.

The thickness of the polyester film is preferably 12 to 50 μm, more preferably 15 to 38 μm, and still more preferably 19 to 33 μm. When the thickness of the film is 12 μm or more, there is no possibility of deformation due to heat in the step of processing a release layer or molding a ceramic green sheet during film production, and therefore, it is preferable. On the other hand, a film thickness of 50 μm or less is preferable because the amount of the film to be discarded after use is not excessive and the environmental load can be reduced.

The biaxially oriented polyester film substrate may have a single layer or a plurality of layers of 2 or more, and preferably has a surface layer a substantially free of particles on at least one surface. In the case of a laminated polyester film comprising 2 or more layers, it is preferable to have a surface layer B which may contain particles or the like on the opposite side of the surface layer A which does not substantially contain particles. When the layer on the side to which the release layer is applied is the surface layer a, the layer on the opposite side thereof is the surface layer B, and the core layer other than these is the layer C, the layer structure in the thickness direction may be a laminate structure such as release layer/a/B or release layer/a/C/B. Of course, the layer C may be a plurality of layers. In addition, the surface layer B may contain no particles. In this case, in order to impart slidability for winding the film into a roll shape, it is preferable to provide a coating layer containing particles and a binder on the surface layer B.

In the polyester film substrate of the present invention, the surface layer a on the side on which the coating release layer is formed preferably contains substantially no particles. At this time, the regional surface average roughness (Sa) of the surface layer a is preferably 7nm or less. When the Sa is 7nm or less, generation of pinholes and the like is less likely to occur at the time of molding of the stacked ultrathin ceramic green sheet, and therefore, it is preferable. The smaller the area surface average roughness (Sa) of the surface layer a is, the more preferable it is, but it may be 0.1nm or more. Here, when an anchor coat layer or the like described later is provided on the surface layer a, the coat layer preferably contains substantially no particles, and the region surface average roughness (Sa) after the coating layers are laminated preferably satisfies the above range. In the present invention, "substantially no particles" means, for example, in the case of inorganic particles, a content of 50ppm or less, preferably 10ppm or less, and most preferably detection limit or less when an inorganic element is quantified by fluorescent X-ray analysis. This is because, even if the particles are not positively added to the film, contamination components derived from foreign substances and contaminants adhering to lines and devices in the production process of the raw material resin or the film may be peeled off and mixed into the film.

In the polyester film substrate of the present invention, the surface layer B on the side opposite to the side on which the release layer is formed preferably contains particles, and particularly, silica particles and/or calcium carbonate particles are preferably used, from the viewpoint of slidability of the film and easiness of air discharge. The content of the particles contained is preferably 5000 to 15000ppm in terms of the total amount of the particles in the surface layer B. In this case, the regional surface average roughness (Sa) of the thin film of the surface layer B is preferably in the range of 1 to 40 nm. More preferably 5 to 35 nm. When the total of the silica particles and/or calcium carbonate particles is 5000ppm or more and the Sa is 1nm or more, air can be uniformly released when the film is wound in a roll form, and the roll form is good and the flatness is good, and thus the method is suitable for producing an ultrathin ceramic green sheet. Further, when the total of the silica particles and/or calcium carbonate particles is 15000ppm or less and the Sa is 40nm or less, aggregation of the lubricant does not easily occur and coarse protrusions are not generated, and therefore, the quality is stable in the production of an ultrathin ceramic green sheet, which is preferable.

As the particles contained in the surface layer B, inactive inorganic particles and/or heat-resistant organic particles, etc. may be used in addition to silica and/or calcium carbonate. From the viewpoint of transparency and cost, silica particles and/or calcium carbonate particles are more preferably used, and examples of other inorganic particles that can be used include alumina-silica composite oxide particles, hydroxyapatite particles, and the like. Examples of the heat-resistant organic particles include crosslinked polyacrylic acid-based particles, crosslinked polystyrene particles, and benzoguanamine-based particles. In the case of using silica particles, porous colloidal silica is preferable, and in the case of using calcium carbonate particles, light calcium carbonate surface-treated with a polyacrylic acid-based polymer compound is preferable from the viewpoint of preventing the lubricant from falling off.

The average particle diameter of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. When the average particle diameter of the particles is 0.1 μm or more, the slip of the release film is good, and therefore, it is preferable. In addition, an average particle size of 2.0 μm or less is preferable because it is not necessary to cause generation of pinholes in the ceramic green sheet due to coarse particles on the surface of the release layer.

The surface layer B may contain particles of 2 or more different raw materials. Further, the particles may contain the same kind and different average particle diameters.

When the surface layer B does not contain particles, it is preferable to make the surface layer B slippery with a coating layer containing particles. The present coating layer is not particularly limited, and is preferably provided by so-called Inline coating (Inline coat) in which coating is performed in the film formation of a polyester film. When the surface layer B does not contain particles and the surface layer B has a coating layer containing particles thereon, the regional surface average roughness (Sa) of the surface of the coating layer is preferably in the range of 1 to 40nm for the same reason as the above-described regional surface average roughness (Sa) of the surface layer B. More preferably 5 to 35 nm.

In the surface layer a as a layer on the side where the release layer is provided, it is preferable not to use a recycled material or the like in order to prevent the mixing of particles such as a lubricant or the like from the viewpoint of reducing pinholes.

The thickness ratio of the surface layer a as a layer on the side where the release layer is provided is preferably 20% to 50% of the total layer thickness of the base film. When the content is 20% or more, the inside of the film is less likely to be affected by particles contained in the surface layer B and the like, and the regional surface average roughness Sa easily satisfies the above range, which is preferable. When the thickness of the base film is 50% or less of the total thickness of the base film, the use ratio of the recycled material in the surface layer B can be increased, and the environmental load is reduced, which is preferable.

In addition, from the viewpoint of economy, 50 to 90 mass% of film scrap or recycled material of plastic bottles can be used for the layers other than the surface layer a (the surface layer B or the intermediate layer C). In this case, the type, amount, particle diameter, and regional surface average roughness (Sa) of the lubricant contained in the surface layer B are preferable since they easily satisfy the above ranges.

In addition, in order to improve the adhesion of a release layer or the like to be applied later and prevent static electricity, etc., a coating layer may 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 step, or corona treatment or the like may be performed. In the case where a coating layer is provided on the surface layer a, the coating layer preferably contains substantially no particles.

(Release layer)

The release layer of the present invention is preferably obtained by curing a composition containing at least a binder component and a silicone-based release agent. Other components may be added in addition to the above-mentioned resin and compound within the range not to inhibit the effect of the present invention.

(Binder component)

The binder component contained in the composition for forming a release layer of the present invention is not particularly limited, and is preferably a crosslinkable component in order to increase the crosslinking density of the release layer and improve the durability, solvent resistance and the like of the release layer. Therefore, the binder component is preferably obtained by reacting a resin having a reactive functional group with a crosslinking agent. Further, it is also preferable that either the reactive functional group or the crosslinking agent is independently self-crosslinked. However, the binder component of the present invention does not exclude a form formed only of a resin having a reactive functional group or formed only of a crosslinking agent.

The resin having a reactive functional group is not particularly limited, and a polyester resin, a poly (meth) acrylic resin, a polyurethane resin, a polyolefin resin, or the like can be suitably used. In these resins, it is preferable that the reactive functional group has at least 1 or more selected from a carboxyl group, a hydroxyl group, an epoxy group, an amino group, and the like.

The resin having a reactive functional group preferably has a long-chain alkyl group and/or a silicone skeleton in a part of the resin skeleton. By having a site with low surface free energy such as a long-chain alkyl group and/or a silicone skeleton in a part of the resin skeleton, compatibility between the silicone-based release agent described later and the binder component becomes high, aggregation at drying becomes difficult, and smoothness is improved, which is preferable.

Specific examples of the reactive functional group-containing resin having a long chain alkyl group in the resin skeleton include alkyd resins having a long chain alkyl group in a side chain, and (meth) acrylic resins. The long-chain alkyl group used is preferably a straight-chain alkyl group having 6 to 20 carbon atoms. Having the above carbon number is preferable because the surface free energy of the obtained resin can be reduced and the compatibility with the silicone-based release agent can be improved.

In the case of an alkyd resin having a long-chain alkyl group in the side chain, the alkyd resin can be obtained by mixing the above-mentioned acid having a long-chain alkyl group (e.g., octanoic acid, stearic acid, etc.) with a polybasic acid such as phthalic acid, further mixing with a polyhydric alcohol component (e.g., pentaerythritol, diethylene glycol, etc.), and subjecting the mixture to a dehydration condensation reaction.

The (meth) acrylic resin having a long-chain alkyl group in a side chain is preferably obtained by copolymerizing 2 or more (meth) acrylic monomers. The comonomer preferably contains a monomer having a long-chain alkyl group (for example, lauryl (meth) acrylate, stearyl (meth) acrylate, isodecyl (meth) acrylate, etc.), and the reactive functional group site preferably contains a monomer having a hydroxyl group (for example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc.). In addition, other known monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexanediol dimethacrylate, and butanediol dimethacrylate may be included in order to impart Tg adjustment, crosslinking property, reactivity, and the like to the obtained polymer.

The content of the monomer having a long-chain alkyl group constituting the obtained acrylic resin is preferably 1 mol% or more and 50 mol% or less with respect to the total monomers constituting the acrylic resin. At least 1 mol% is preferable because it has an effect of reducing the surface free energy. When the amount is 50 mol% or less, the monomer having a reactive functional group is relatively high, and therefore the crosslinking density of the resin is preferably high.

Specific examples of the reactive functional group-containing resin having a silicone skeleton in the resin skeleton include alkyd resins or acrylic resins having a polydimethylsiloxane skeleton in the side chain. Specific examples of commercially available products include SYMAC (registered trademark) US350, US352 (reactive functional group: carboxyl group, manufactured by Toyo chemical Co., Ltd.), SYMAC (registered trademark) US270 (reactive functional group: hydroxyl group, manufactured by Toyo chemical Co., Ltd.), and the like.

(crosslinking agent)

The binder component preferably further contains a crosslinking agent. The crosslinking agent is not particularly limited, and a melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, or epoxy-based crosslinking agent may be used, and one kind may be used or two or more kinds may be used in combination. Particularly preferred is a crosslinking agent capable of reacting with the reactive functional group introduced into the binder component.

The crosslinking agent used in the present invention is preferably a melamine compound from the viewpoint of reactivity. By using the melamine compound, the coating amount after curing of the release layer was 0.2g/m²The following film is preferable because it can be cured quickly and the crosslinking density is high.

The melamine compound used in the present invention may be any of those generally used, but is not particularly limited, and is preferably obtained by condensing melamine with formaldehyde, and preferably has 1 or more triazine rings and hydroxymethyl groups and/or alkoxymethyl groups in each molecule. Specifically, preferred are compounds obtained by subjecting a methylolmelamine derivative obtained by condensing melamine with formaldehyde and a lower alcohol such as methanol, ethanol, isopropanol, or butanol to a dehydration condensation reaction and etherification, and the like. Examples of the methylolated melamine derivative include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylmelamine, and hexamethylolmelamine. One kind or two or more kinds may be used.

As the melamine-based compound, hexamethylol melamine, hexamethoxy methylolmelamine, or the like having a plurality of crosslinking points in 1 molecule is preferably used because the crosslinking density of the binder component can be increased. When an ether compound obtained by subjecting a methylolmelamine derivative to dehydration condensation reaction with an alcohol is used, hexamethoxymethylhydroxymethyl melamine obtained by dehydration condensation with methanol is particularly preferable from the viewpoint of reactivity.

The amount of the crosslinking agent contained in the binder component in the present invention is preferably 15% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass, relative to the resin having a reactive functional group. When the crosslinking agent is self-condensed to form a resin film, the binder component may be constituted by only the crosslinking agent. The inclusion of 15 mass% or more of a crosslinking agent is preferable because the crosslinking density of the release layer can be increased and the solvent resistance and the elastic modulus can be improved.

(catalyst)

The composition for forming a release layer of the present invention may contain a catalyst for curing the crosslinking agent. When a melamine compound is used, an acid catalyst is preferably used, and is not particularly limited, and a carboxylic acid-based, metal salt-based, phosphate-based, or sulfonic acid-based acid catalyst can be suitably used. In addition, a blocked catalyst in which an acid site is blocked may be used. In particular, p-toluenesulfonic acid can be suitably used from the viewpoint of reactivity. When the isocyanate-based compound is used, those which are generally used can be used, and organic tin, amine compound, trialkyl phosphine compound and the like can be suitably used.

The content of the catalyst is preferably 0.1 to 40% by mass based on the crosslinking agent contained in the composition for forming a release layer. More preferably 0.5 to 30 mass%. More preferably 0.5 to 20 mass%. When the content is 0.1% by mass or more, the curing reaction is easy to proceed, and therefore, it is preferable. On the other hand, when the content is 40% by mass or less, there is no fear that the acid catalyst is transferred to the formed ceramic green sheet, and it is preferable from the viewpoint of not causing adverse effects.

(Silicone mold release agent)

The silicone-based release agent used as the release layer of the present invention is a compound having an organosilicon structure in the molecule, and is not particularly limited as long as the effects of the present invention are obtained, and a polyorganosiloxane or the like can be suitably used. Among the polyorganosiloxanes, polydimethylsiloxane (abbreviated as PDMS) can be suitably used, and one having a functional group in a part of the polydimethylsiloxane is preferable. Having a functional group is preferable because intermolecular interaction between the binder resin and hydrogen bonds and the like is easily expressed and transfer to the ceramic green sheet is difficult.

The functional group to be introduced into polydimethylsiloxane is not particularly limited, and a reactive functional group or a non-reactive functional group is optional. The functional group may be introduced at one end of the polydimethylsiloxane, at both ends, or in a side chain. The number of introduction positions may be 1 or more.

Examples of the reactive functional group introduced into polydimethylsiloxane include an amino group, an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group, a methacrylic group, an acrylic group, and the like. As the non-reactive functional group, a polyether group, an aralkyl group, a fluoroalkyl group, a long chain alkyl group, an ester group, an amide group, a phenyl group, or the like can be used. Without being bound by theory, those having epoxy, carboxyl, polyether, methacrylic, acrylic, ester groups among the above are preferred.

The functional group introduced into the polydimethylsiloxane is more preferably not reactive with the binder component. For example, polydimethylsiloxane modified with a hydroxyl group or the like that reacts with a melamine resin reacts with melamine in the drying step, and therefore, orientation is not easily caused on the surface of the release layer, the Si element ratio on the surface of the release layer is reduced, and releasability is not easily exhibited in some cases. Therefore, in order to provide sufficient releasability, the amount of addition needs to be increased, and in this case, the elastic modulus of the release layer decreases, and the release layer may be easily deformed.

From the above-described reasons, the functional group introduced into polydimethylsiloxane is particularly preferably a polyether group or an ester group, and particularly preferably a polyether group, as a functional group which does not react with the binder resin, is easily oriented on the surface of the release layer, and has little transferability to the ceramic green sheet. The functional group having a high Si element ratio on the surface of the release layer even when reacted with the binder resin includes a carboxyl group.

The molecular weight of the silicone-based release agent used in the present invention is preferably 40000 or less. More preferably 30000 or less. When the molecular weight is 40000 or less, the silicone-based release agent is preferably because it is likely to segregate on the surface of the release layer and has good releasability.

The content of the component derived from the silicone-based release agent contained in the release layer after curing in the present invention is preferably 1mg/m²Above and 15mg/m²The following. More preferably 1mg/m²Above and 10mg/m²The following. Is 1mg/m²In the above case, the silicone component is preferably precipitated sufficiently on the outermost layer of the release layer, and the releasability of the ceramic green sheet is stable. Is 15mg/m²In the following case, the silicone component having a low elastic modulus in the release layer is small, and therefore the elastic modulus of the release layer does not become too low, and the releasability of the ceramic sheet is stable, which is preferable. Here, if the chemical structure of the silicone release agent does not change in the cured release layer and exists as an original structure, the chemical structure may change due to a chemical reaction with a binder component or the like. Here, the mass of a substance existing per unit area of the release layer after curing, which is derived from the silicone-based release agent in the composition before curing, is referred to as the content of the component derived from the silicone-based release agent. The content of the component derived from the silicone release agent may be determined by the presence ratio (mass%) of the silicone release agent in the solid content of the coating liquid containing the composition and the coating amount (g/m) of the solid content of the release layer after curing²) And (4) calculating and solving.

The release layer of the present invention may contain particles having a particle diameter of 1 μm or less, but from the viewpoint of pin hole suppression of the ceramic green sheet, a material which forms projections without particles or the like is more preferable.

In the release layer of the present invention, additives such as adhesion improving agents and antistatic agents may be added as long as the effects of the present invention are not impaired. In order to improve the adhesion to the substrate, the surface of the polyester film is preferably subjected to pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment before the release coating layer is provided.

The amount of the release layer after curing of the present invention is not particularly limited, but is preferably 1.0g/m²The following. More preferably 0.01 to 0.5g/m²More preferably 0.02 to 0.20g/m²If it is 0.02 to 0.09g/m²It is more preferable. The coating amount of the release layer was 0.01g/m²The above is preferable because the peeling property can be easily obtained. Is 0.2g/m²In the following case, since the curing time of the release layer can be shortened, the planarity of the release film is protected, and the thickness unevenness of the ceramic green sheet can be suppressed, which is preferable. Further 0.2g/m²In the following case, the obtained film is preferably improved in molding accuracy at the time of molding the ceramic green sheet because the curl is also reduced.

The surface free energy of the surface of the release layer of the release film of the present invention is preferably 18mJ/m²Above and 35mJ/m²The following. More preferably 20mJ/m²Above and 30mJ/m²Hereinafter, more preferably 21mJ/m²Above and 28mJ/m²The following. Is 18mJ/m²The above is preferable because the ceramic slurry is less likely to shrink when applied and can be applied uniformly. Further, it was 35mJ/m²Hereinafter, the ceramic green sheet is preferable because the releasability thereof may not be lowered. By setting the above range, a release film having no shrinkage at the time of coating and excellent releasability can be provided.

In the release film of the present invention, the peeling force at the time of peeling the ceramic green sheet is preferably 0.5mN/mm²Above and 3mN/mm²The following. More preferably 0.8mN/mm²2.5mN/mm or more²The following. More preferably 1.0mN/mm²Above and 1.8mN/mm²The following. The peel force was 0.5mN/mm²The above is preferable because the peeling force is not too low and the ceramic green sheet does not float during transportation. The peel force was 3mN/mm²In the following case, the ceramic green sheet is preferably peeled off without being damaged.

The release film of the present invention preferably has less curling. Specifically, the curl after heating at 100 ℃ for 15 minutes is preferably 2mm or less, more preferably 1mm or less, without applying tension to the film. Of course, it is also preferred that no curl is present at all. When the thickness is 2mm or less, the ceramic green sheet is preferably formed and the electrode is printed, since the curl is small and the printing accuracy can be improved.

On the surface of the release layer of the release film of the present invention, it is preferable that the component derived from the silicone-based release agent contained in the release layer is sufficiently precipitated. As an index indicating the amount of deposition of a component derived from the silicone-based release agent, the ratio of Si element on the surface of the release layer can be used. The Si element ratio on the surface of the release layer can be evaluated by ESCA capable of measuring only the surface of the release layer. The Si element ratio in the present invention is represented by the following formula, and is the ratio (at%) of Si in 5 elements of C, S, Si, O, and N.

Si element ratio (at%) { Si/(C + O + N + S + Si) } × 100 … formula

The release film of the present invention preferably has a Si element ratio of 2.0 at% or more on the outermost surface of the release layer. More preferably 2.5 at% or more, and even more preferably 3.0 at% or more, and still more preferably 3.5 at% or more. When the content is 2.0 at% or more, the silicone-based release agent can sufficiently cover the surface of the release layer, and the peeling force is stable when the ceramic green sheet of the film is peeled. The upper limit of the Si element ratio is preferably 10 at% or less, more preferably 9 at% or less, and still more preferably 8 at% or less. When the content is 10 at% or less, the elastic modulus of the surface of the release layer is not lowered, and the peeling is stable, so that the composition is preferable.

In order to achieve the Si element ratio on the outermost surface of the release layer of the release film of the present invention, it is preferable to optimize the content of the component derived from the silicone-based release agent contained in the release layer after the curing and the passage time of the initial drying step after the application of the release layer described later.

The surface of the release layer of the release film of the present invention is desirably flat so as not to cause defects in the ceramic green sheet applied and formed thereon, and the average surface roughness (Sa) of the area is preferably 1.5nm or less, more preferably 1.2nm or less, and still more preferably 1.0nm or less. The maximum protrusion height (P) of the surface of the release layer is preferably 50nm or less, more preferably 40nm or less, and still more preferably 30nm or less. When the area surface average roughness (Sa) is 1.5nm or less and the maximum protrusion height (P) is 50nm or less, defects such as pinholes are not generated at the time of forming the ceramic green sheet, and productivity is good, so that it is preferable. The smaller the area surface average roughness (Sa), the more preferable, but it may be 0.1nm or more, or 0.3nm or more. The smaller the maximum protrusion height (P) is, the more preferable, but the maximum protrusion height may be 1nm or more, or 3nm or more.

In the release film of the present invention, in order to use a highly planarized base film, the amount of the release layer applied is preferably 0.2g/m²The ratio is set to 0.09g/m²Since the surface of the release layer can be made thin and smooth, the amount of solvent and resin used can be reduced, and the release film for molding an ultrathin ceramic green sheet can be produced at low cost.

In order to set the maximum protrusion height (P) of the surface of the release layer of the release film of the present invention to 50nm or less and the region average roughness (Sa) to 1.5nm or less, it is preferable to suppress aggregation of the silicone release agent and the binder component until the coating liquid of the release layer is applied and dried. Therefore, as described in the production method described later, the time from the application to the drying is performed under certain conditions, whereby a target ultra-high smooth surface of the release layer can be obtained.

(method for producing Release film)

The method for producing the release film of the present invention is not particularly limited, and a method of laminating release layers through the following steps is preferably used: a coating step of coating at least one surface of the polyester film of the substrate with a coating solution in which at least a binder component and a silicone-based release agent are dissolved or dispersed in a solvent by coating or the like to laminate the polyester film; an initial drying step of mainly removing the solvent and the like after coating; and a heat curing step of mainly curing the binder resin and the like. The surface of the polyester film on the release layer side is preferably a surface layer a substantially free of particles, and another coating layer may be present between the surface layer a and the release layer.

(coating Process)

The solvent for dissolving or dispersing the binder resin and the silicone-based release agent is not particularly limited, and an organic solvent is preferably used. The use of an organic solvent is preferable because the surface tension of the coating liquid can be reduced, shrinkage and the like hardly occur after coating, and the surface smoothness of the release layer can be kept high.

The organic solvent used in the method for producing a release film of the present invention is not particularly limited, and known ones can be used. Examples of the solvent generally include aromatic hydrocarbons such as benzene, toluene, and xylene; fatty acid hydrocarbons such as cyclohexane, n-hexane, and n-heptane; halogenated hydrocarbons such as perchloroethylene; ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and the like. In view of coatability when coating on the surface of the base film, a mixed solvent of toluene and methyl ethyl ketone is practically preferable, though not limited thereto.

In the present invention, the coating liquid used for coating for forming the release layer is not particularly limited, and preferably contains 2 or more organic solvents having different boiling points. Preferably, at least 1 of the organic solvents has a boiling point of 100 ℃ or higher. By adding a solvent having a boiling point of 100 ℃ or higher, bumping during drying can be prevented, the coating film can be leveled, and the smoothness of the surface of the coating film after drying can be improved. The amount of the additive is preferably about 10 to 50% by mass based on the whole coating liquid. Examples of the solvent having a boiling point of 100 ℃ or higher include toluene, xylene, octane, cyclohexanone, methyl isobutyl ketone, n-propyl acetate, and the like.

In the present invention, the surface tension (20 ℃) of the coating liquid when the coating liquid for forming the release layer is applied is not particularly limited, and is preferably 30mN/m or less. By setting the surface tension as described above, the coatability after coating is improved, and unevenness on the surface of the coating film after drying can be reduced. In order to reduce the surface tension of the coating liquid, it is preferable to use an organic solvent having a low surface tension. The surface tension (20 ℃) of at least 1 organic solvent is preferably 26mN/m or less, and more preferably 23mN/m or less. The inclusion of an organic solvent having a surface tension (20 ℃) of 26mN/m or less is preferable because it can reduce appearance defects such as shrinkage at the time of coating. The amount of addition is preferably 20% by mass or more based on the entire coating liquid.

The solid content concentration of the release agent contained in the coating liquid is preferably 0.1 mass% or more and 10 mass% or less, and more preferably 0.2 mass% or more and 8 mass% or less. When the solid content concentration is 0.1 mass% or more, the drying after coating is fast, and therefore aggregation of the components in the release agent is not likely to occur, and is preferable. On the other hand, when the solid content concentration is 10% by mass or less, the coating liquid is preferably low in viscosity and good in leveling property, so that the flatness after coating can be improved. The viscosity of the coating liquid is preferably 1 to 100mPa · s, more preferably 2 to 10mPa · s, in view of the coating appearance. The solid content concentration, the organic solvent, and the like are preferably adjusted so as to fall within this range.

In the present invention, the coating liquid for forming the release layer is preferably filtered before coating. The filtration method is not particularly limited, and a known method can be used, and a surface type, depth type, or adsorption type filtration cartridge is preferably used. The use of a cylindrical filter is preferable because it can be used when the coating liquid is continuously fed from the tank to the coating section, and therefore, filtration can be performed efficiently with high productivity. The filter is preferably a filter that removes 99% or more of substances having a size of 1 μm, and more preferably a filter that can filter 99% or more of substances having a size of 0.5 μm. By using the filter having the above filtration accuracy, foreign matters mixed in the release agent can be removed, and foreign matters adhering to the release layer of the release film for molding a ceramic green sheet of the present invention can be greatly reduced. Therefore, the ceramic green sheet molded using the release film of the present invention can be reduced in defects and the ceramic capacitor can be reduced in defect rate.

As the coating method of the coating liquid, any known coating method can be used, and conventionally known methods such as a roll coating method such as a gravure coating method and a reverse coating method, a bar coating method such as a wire bar, a die coating method, a spray coating method, and an air knife coating method can be used.

Coating liquid film in coatingThe thickness (amount of Wet) is preferably 1g/m²Above and 10g/m²The following. Is 1g/m²The above is preferable because the coating is stable and defects such as shrinkage and streaks are not easily generated. In addition, if it is 10g/m²Hereinafter, the drying is fast and the components contained in the release layer are less likely to aggregate, so that it is preferable.

(drying Process)

As a method for applying the coating liquid on the base film and drying it, known hot air drying, heating drying by an infrared heater or the like can be mentioned, and hot air drying at a high drying rate is preferable. The drying furnace may be divided into a constant rate drying step (hereinafter referred to as an initial drying step) for the initial drying and a step (hereinafter referred to as a heat curing step) for the rate-reducing drying and curing of the resin. The initial drying step and the heat curing step may be continuous or discontinuous, and are preferable because continuous productivity is good. Each step is preferably divided into areas of the drying furnace. The number of regions in each step may be 1 or more.

In the method for producing a release film of the present invention, the release film is preferably placed in a drying oven within 1.5 seconds after coating, more preferably within 1.0 second, and still more preferably within 0.8 second. It is preferable to put the sheet into a drying oven within 1.5 seconds after the coating to start drying, because the components contained in the release layer can be dried before aggregation occurs, and thus the surface smoothness of the release layer can be prevented from being deteriorated due to aggregation. The time from the application to the drying in the oven is preferably short, and the lower limit is not particularly limited, and may be 0.05 seconds or more, or may be 0.1 seconds or more.

The initial drying step is not particularly limited, and a known drying furnace may be used. The drying furnace system is preferably a roller support system or a floating system because the range of the adjustable air volume during drying is wide in the roller support system, and the air volume can be adjusted according to the type of the release layer.

The temperature in the initial drying step is preferably 60 ℃ to 140 ℃, more preferably 70 ℃ to 130 ℃, and still more preferably 80 ℃ to 120 ℃. By setting the temperature to 60 ℃ or higher and 140 ℃ or lower, the organic solvent amount contained in the release layer after coating can be efficiently dried without causing poor planarity due to heat, which is preferable.

The time for passing through the initial drying step is preferably 1.0 second to 3.0 seconds, more preferably 1.0 second to 2.5 seconds, and still more preferably 1.2 seconds to 2.5 seconds. When the amount is 1.0 second or more, the organic solvent contained in the release layer after coating can be sufficiently dried, and therefore, it is preferable. Further, it is preferable to set the time to 1.0 second or more because the component derived from the silicone-based release agent contained in the release layer can be efficiently precipitated on the surface of the release layer. When the amount is 3.0 seconds or less, aggregation of components in the release layer is less likely to occur, and therefore, is preferable. By adjusting the solid content concentration, the type of organic solvent, and the like of the coating liquid so as to be able to dry within the above time, even if a coating liquid which is likely to aggregate is used, deterioration of smoothness due to aggregation can be suppressed.

The amount of the organic solvent contained in the release layer after the initial drying step is preferably 5% by mass or less, and more preferably 2% by mass or less. By setting the amount of the organic solvent to 5% by mass or less, deterioration in appearance due to bumping or the like can be prevented even when heated in the heating step, and therefore, this is preferable. The amount of the organic solvent in the release layer may be measured by gas chromatography, thermogravimetric analysis, or the like after the initial drying step by sampling the thin film, or may be estimated by simulation (simulation) using drying. The method based on the simulation is preferable because the measurement can be performed without stopping the process. The simulation is not particularly limited, and known simulation software can be used.

(Heat curing step)

The release film of the present invention is preferably subjected to a heat curing step after the initial drying step. The heat curing step is not particularly limited, and a known drying furnace may be used. Regarding the manner of the drying furnace, a roller support manner or a floating manner is optional. The heat curing step is optionally a continuous step or a discontinuous step with the initial drying step, and a continuous step is preferred from the viewpoint of productivity.

The temperature in the heat curing step is preferably 80 ℃ to 180 ℃, more preferably 90 ℃ to 160 ℃, and still more preferably 90 ℃ to 140 ℃. When the temperature is 180 ℃ or lower, the flatness of the film is protected, and the thickness unevenness of the ceramic green sheet is less likely to occur, so that it is preferable. The temperature of 140 ℃ or lower is particularly preferable because the film can be processed without impairing the flatness of the film, and the possibility of causing thickness unevenness of the ceramic green sheet is further reduced. When the temperature is 80 ℃ or higher, curing is sufficiently performed in the case of a thermosetting resin, and therefore, it is preferable.

The time for passing through the heat curing step is preferably 2 seconds to 30 seconds, and more preferably 2 seconds to 20 seconds. When the passage time is 2 seconds or more, the curing of the thermosetting resin proceeds, and therefore, it is preferable. When the amount is 30 seconds or less, the flatness of the film due to heat is not reduced, and therefore, it is preferable.

At the end of the heat curing step, the hot air temperature is preferably equal to or lower than the glass transition temperature of the base film, and the actual temperature of the base film is preferably equal to or lower than the glass transition temperature in a flat state. When the base film is taken out of the drying furnace as it is at a temperature not lower than the glass transition temperature, the sliding is poor when the base film comes into contact with the surface of the roll, and not only scratches but also curling may occur.

The release film of the present invention is preferably wound into a roll after passing through the heat curing step. After the heat curing step, the time taken to wind up the sheet into a roll is preferably 2 seconds or longer, and more preferably 3 seconds or longer. When the amount is 2 seconds or more, the release film whose temperature has risen in the heat curing step is cooled and taken up by a roll, and therefore flatness is not impaired, and this is preferable.

In the release film and the method for producing the same of the present invention, various treatments may be performed before winding the film into a roll after the heat curing step, and the curing treatment, the static charge removing treatment, the corona treatment, the plasma treatment, the ultraviolet irradiation treatment, the electron beam irradiation treatment, and the like may be performed.

(ceramic Green sheet and ceramic capacitor)

Generally, a laminated ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, the 1 st internal electrode and the 2 nd internal electrode are alternately arranged in the thickness direction. The 1 st internal electrode is exposed at the 1 st end surface of the ceramic body. A1 st external electrode is provided on the 1 st end face. The 1 st internal electrode is electrically connected to the 1 st external electrode at the 1 st end face. The 2 nd internal electrode is exposed at the 2 nd end surface of the ceramic body. A2 nd external electrode is provided on the 2 nd end face. The 2 nd internal electrode is electrically connected to the 2 nd external electrode at the 2 nd end face.

The release film for producing a ceramic green sheet of the present invention can be used for producing such a multilayer ceramic capacitor. For example, it can be manufactured in the following manner. First, a ceramic slurry for forming a ceramic body is applied to a release film of the present invention as a carrier film and dried. On the ceramic green sheet subjected to coating and drying, a conductive layer for constituting the 1 st or 2 nd internal electrode was printed. The ceramic green sheets, the ceramic green sheets on which the conductive layers for constituting the 1 st internal electrodes were printed, and the ceramic green sheets on which the conductive layers for constituting the 2 nd internal electrodes were printed were appropriately stacked and pressed, thereby obtaining a mother laminate. The mother laminate is divided into a plurality of pieces to produce a green ceramic body. The ceramic body is obtained by firing a green ceramic body. After that, the 1 st and 2 nd external electrodes are formed to complete the multilayer ceramic capacitor.

Examples

The present invention will be described in further detail with reference to examples below, but the present invention is not limited to these examples. The characteristic values used in the present invention were evaluated by the following methods.

(region surface average roughness (Sa), maximum protrusion height (P))

The measured values were measured under the following conditions using a non-contact surface shape measuring system (manufactured by Ryoka Systems Inc., VertScan R550H-M100). The area surface average roughness (Sa) was measured by taking the average of 5 measurements, the maximum protrusion height (P) was measured 7 times, the maximum value and the minimum value were removed, and the maximum value of 5 times was used.

(measurement conditions)

Measurement mode: WAVE mode

Objective lens: 10 times of

0.5 × Tube objective lens

Measurement area 936. mu. m.times.702. mu.m

(analysis conditions)

Surface correction: 4 times correction

Interpolation processing: full interpolation

Filter processing: gauss cut-off value of 50 μm

(amount of coating of Release layer)

The coating amount of the release layer after curing of the release film of the present invention was measured by a gravimetric method. The release film was sampled to a size of 15cm × 15cm, and after static electricity was removed by using a static electricity remover, the weight was measured by using a precision balance (AUW 120D manufactured by shimadzu corporation). The release layer of the release film to be measured was wiped with methyl ethyl ketone, dried at 80 ℃ for 1 minute with a hot air dryer, and then the mass was measured again with a precision balance. The difference between the weight of the film before wiping the release layer and the weight of the film after wiping was divided by the area of the film (15 cm. times.15 cm), and the amount of the release layer applied (g/m) was calculated²). The average value of 3 times was used by removing the maximum value and the minimum value by performing 5 measurements using films sampled from different positions.

(Si element ratio of the outermost surface of the mold releasing layer)

The Si element ratio of the outermost surface of the release layer of the release film of the present invention was measured by ESCA. The device uses K-Alpha⁺(manufactured by Thermo Fisher Scientific Co., Ltd.). The details of the measurement conditions are shown below. Using this apparatus, the Si element ratio (at%) was calculated by the following equation by performing narrow scanning of 5 elements of C, O, N, S, Si on the surface of the release layer. (in the present invention, the Si element ratio is C, O, N, S, Si5 element Si (at%))

Si element ratio (at%) { Si/(C + O + N + S + Si) } × 100 … formula

In the analysis, the background was removed by the shirley method. The surface Si element ratio is an average of the measurement results of 3 or more.

Measurement conditions

Exciting X-ray, monochromatized Al Ka line

The X-ray power is 12kV and 6mA

Photoelectron escape angle of 90 °

Spot size 400mm f (left and right)

Path energy 50eV

Step size of 0.1eV

(surface free energy)

A droplet of water (droplet amount: 1.8. mu.L), diiodomethane (droplet amount: 0.9. mu.L) and ethylene glycol (droplet amount: 0.9. mu.L) was formed on the release surface of the release film by means of a contact angle meter (manufactured by Kyowa interface science Co., Ltd.: full-automatic contact angle meter, DM-701) under conditions of 25 ℃ and 50% RH, and the contact angle thereof was measured. The contact angle was measured after 10 seconds after each droplet was applied to the release film. The contact angle data of water, diiodomethane and ethylene glycol obtained by the above method was calculated by the theory of "hokkaki-zuku" to obtain the dispersion component γ sd, the polar component γ sp and the hydrogen bond component γ sh of the surface free energy of the release film, and the total value of the components was defined as the surface free energy γ s. This calculation is performed using calculation software in the contact angle measuring software (FAMAS).

(surface tension of coating liquid)

The surface tension of the coating liquid was measured by the Wilhelmy method using a platinum plate at 20 ℃ using a surface tensiometer (manufactured by Kyowa interface science Co., Ltd.: high-performance surface tensiometer DY-500). The average of 3 measurements was used.

(viscosity of coating liquid)

The viscosity of the coating liquid was measured at 20 ℃ using a rotary viscometer (TVB-15M, manufactured by Toyobo industries Co., Ltd.). When a low-viscosity liquid of 10 mPas or less is measured, the measurement is carried out by using an additional low-viscosity adapter. The average value of 3 measurements was used.

(evaluation of coatability of ceramic slurry)

A composition comprising the following materials was stirred and mixed, and dispersed for 60 minutes using a bead mill using zirconia beads having a diameter of 0.5mm to obtain a ceramic slurry.

Then, the release surface of the obtained release film sample was coated with a coater so that the dried slurry became 1 μm, and after drying at 90 ℃ for 1 minute, the coating property was evaluated in accordance with the following criteria.

O: the entire surface can be coated without shrinkage or the like.

And (delta): the coated end is slightly constricted but substantially the entire surface can be coated.

X: the shrinkage was large and the coating was not performed.

(pinhole evaluation of ceramic Green sheet)

In the same manner as in the evaluation of the coatability of the ceramic slurry, a ceramic green sheet having a thickness of 1 μm was molded on the release surface of the release film.

Then, the release surface of the obtained release film sample was coated with a paste having a thickness of 1 μm after drying using an applicator, and after drying at 90 ℃ for 1 minute, the release film was peeled off to obtain a ceramic green sheet.

In the central region of the obtained ceramic green sheet in the film width direction of 25cm²In a state where light is irradiated from the side opposite to the applied side of the ceramic slurry, and visible pinholes are generated by observing light transmission, the evaluation was made by visual observation according to the following criteria.

O: no generation of pin holes

And (delta): substantially free from generation of pinholes

X: the generation of pinholes is large

(evaluation of releasability of ceramic Green sheet)

Then, the release surface of the obtained release film sample was coated with a dried slurry using an applicator so as to have a thickness of 10 μm, and dried at 90 ℃ for 1 minute to mold a ceramic green sheet on the release film. The obtained release film with ceramic green sheet was subjected to static elimination using a static elimination machine (SJ-F020, manufactured by Keyence corporation), and then peeled at a peeling angle of 90 degrees and a peeling speed of 10 m/min with a width of 30 mm. The stress required for peeling was measured and used as the peeling force.

(evaluation of peeling stability of ceramic Green sheet)

The peeling property was evaluated 10 times in the same manner as in the above-described evaluation of the peeling property of the ceramic green sheet. The deviation of the peeling force was evaluated 10 times according to the following criteria, and the evaluation was made as the evaluation of the peeling stability.

O: the difference between the maximum value and the minimum value in 10 measurements is less than 0.5mN/mm²。

And (delta): the difference between the maximum value and the minimum value in 10 measurements was 0.5mN/mm²Above and less than 1.0N/mm²。

X: the difference between the maximum value and the minimum value in 10 measurements was 1.0mN/mm²The above.

(evaluation of curl of Release film)

The sample of the release film was cut into a size of 10cm × 10cm, and heat-treated with a hot air oven at 100 ℃ for 15 minutes in such a manner that no tension was applied to the release film. After that, the sheet was taken out of the oven and cooled to room temperature, and then a release film sample was placed on the glass plate with the release surface facing upward, and the height of the portion floating from the glass plate was measured. The height of the maximum floating portion on the glass plate at this time was defined as a measured value. The curling properties were evaluated according to the following criteria.

O: the curl was 1mm or less, and almost no curl was observed.

And (delta): the curl was larger than 1mm and 2mm or less, and a small amount of curl was observed.

X: the curl was greater than 2mm and the curl occurred.

(preparation of polyethylene terephthalate Pellets (PET) (I))

As the esterification reaction apparatus, a continuous esterification reaction apparatus comprising a 3-stage complete mixing tank having a stirring apparatus, a partial condenser, a raw material inlet and a product outlet was used. TPA (terephthalic acid) was 2 tons/hr, EG (ethylene glycol) was 2 moles per 1 moles of TPA, and antimony trioxide was 160ppm in terms of atoms of PET and Sb produced, and these slurries were continuously supplied to the 1 st esterification reaction tank of the esterification reaction apparatus, and reacted at 255 ℃ with an average residence time of 4 hours under normal pressure. Then, the reaction product in the 1 st esterification reaction tank was continuously taken out of the system and supplied to the 2 nd esterification reaction tank, 8 mass% of EG distilled off from the 1 st esterification reaction tank was supplied to the 2 nd esterification reaction tank with respect to the produced PET, and an EG solution containing magnesium acetate tetrahydrate salt in an amount of 65ppm with respect to the produced PET and Mg atom and an EG solution containing TMPA (trimethyl phosphate) in an amount of 40ppm with respect to the produced PET and P atom were added thereto, and the reaction was carried out at 260 ℃ for 1 hour at an average residence time under normal pressure. Next, the reaction product in the 2 nd esterification reaction tank was continuously taken out of the system and supplied to the 3 rd esterification reaction tank, and the reaction product was dispersed by a high pressure disperser (manufactured by Nippon Seiko Co., Ltd.) at 39MPa (400 kg/cm)²) 0.2 mass% of porous colloidal silica having an average particle size of 0.9 μm obtained by dispersion treatment with an average treatment frequency of 5 times (pass) and 0.4 mass% of synthetic calcium carbonate having an average particle size of 0.6 μm and having 1 mass% of an ammonium salt of polyacrylic acid attached to the calcium carbonate unit were added as 10% EG slurry, and the reaction was carried out at 260 ℃ for an average retention time of 0.5 hour under normal pressure. Continuously feeding the esterification reaction product generated in the 3 rd esterification reaction tank to a 3-stage continuous polycondensation reaction device, performing polycondensation, filtering with a filter sintered with 95% stainless steel fiber with diameter of 20 μm, performing ultrafiltration, extruding in water, cooling, and cutting into small pieces (chips) to obtain the final productTo PET chips having an intrinsic viscosity of 0.60dl/g (hereinafter, abbreviated as PET (I)). The content of the lubricant in the PET chips was 0.6 mass%.

(preparation of polyethylene terephthalate Pellets (PET) (II))

On the other hand, in the production of the above PET chips, PET chips having an intrinsic viscosity of 0.62dl/g (hereinafter referred to as PET (II)) completely free of particles such as calcium carbonate and silica are obtained.

(production of polyethylene terephthalate Pellets (PET) (III))

The types and contents of the PET (I) particles are changed as follows: PET flakes (hereinafter referred to as PET (III)) were obtained in the same manner as PET (I) except that 0.75 mass% of synthetic calcium carbonate having an average particle diameter of 0.9 μm, to which 1 mass% of ammonium salt of polyacrylic acid per unit of calcium carbonate was attached, was used. The content of the lubricant in the PET chips was 0.75 mass%.

(production of laminated film X1)

These PET chips were dried, melted at 285 ℃, melted at 290 ℃ by a separate melt extrusion extruder, subjected to 2-stage filtration using a filter sintered with 95% of stainless steel fibers having a cut diameter of 15 μm and a filter sintered with 95% of stainless steel particles having a cut diameter of 15 μm, merged in a feed block (feed block) so that PET (i) became a surface layer B (reverse release surface side layer) and PET (ii) became a surface layer a (release surface side layer), extruded (cast) at a rate of 45 m/min into a sheet form, and subjected to electrostatic adhesion and cooling on a casting drum at 30 ℃ by an electrostatic adhesion method to obtain an unstretched polyethylene terephthalate sheet having an intrinsic viscosity of 0.59 dl/g. The layer ratio was adjusted so that pet (i)/(II) — 60%/40% was calculated according to the discharge amount of each extruder. Subsequently, the unstretched sheet was heated by an infrared heater and then stretched 3.5 times in the machine direction at a roll temperature of 80 ℃ by the speed difference between rolls. Thereafter, the resultant was introduced into a tenter and stretched 4.2 times in the transverse direction at 140 ℃. Subsequently, heat treatment was performed at 210 ℃ in the heat-set region. Thereafter, a 2.3% relaxation treatment was carried out at 170 ℃ in the transverse direction to obtain a biaxially stretched polyethylene terephthalate film X1 having a thickness of 31 μm. The Sa of the surface layer A and the Sa of the surface layer B of the obtained film X1 were 2nm and 28nm, respectively.

(production of laminated film X2)

A biaxially stretched polyethylene terephthalate film X2 having a thickness of 25 μm was obtained by adjusting the thickness of the film at a casting speed without changing the stretching conditions and with the same layer composition as that of the laminated film X1. The Sa of the surface layer A and that of the surface layer B of the obtained film X2 were 3nm and 29nm, respectively.

(laminated film X3)

A4100(COSMOSHINE (registered trademark), Toyo Kabushiki Co., Ltd.) having a thickness of 25 μm was used as the laminated film X3. A4100 is substantially free of particles in the thin film, and is configured such that a coating layer containing particles is provided on the surface layer B side by in-line coating (Inline coat). The Sa of the surface layer A and the Sa of the surface layer B of the laminated film X3 were 1nm and 2nm, respectively.

(laminated film X4)

As the laminated film X4, E5101(Toyobo ester (registered trademark) film, Toyo Kabushiki Co., Ltd.) having a thickness of 25 μm was used. E5101 has a structure in which particles are contained in the surface layers a and B of the film. The Sa of the surface layer A of the laminated film X4 was 24nm, and the Sa of the surface layer B was 24 nm.

(production of laminated film X5)

A biaxially stretched polyethylene terephthalate film X5 having a thickness of 31 μm was obtained in the same manner as in the laminated film X1, except that pet (iii) was laminated to form a surface layer B (release surface side layer) and pet (II) was laminated to form a surface layer a (release surface side layer), and the layer ratio was such that pet (iii)/(II): 80%/20% in terms of the discharge amount of each extruder. The Sa of the surface layer A and that of the surface layer B of the obtained film X5 were 2nm and 30nm, respectively.

(resin solution A) acrylic polyol ester having a Long-chain alkyl group

The resulting mixture was diluted with toluene so that the solid content concentration became 40% by mass, and 0.5% by mol of azobisisobutyronitrile was added under a nitrogen stream to copolymerize the mixture, thereby obtaining a resin solution a. The weight average molecular weight of the polymer obtained at this time was 30000.

(example 1)

Coating solution 1 having the following composition was passed through a filter capable of removing 99% or more and 0.5 μm or more of foreign matter, and then reverse gravure was used so that the coating film thickness (wet amount) became 5g/m²Was coated on the surface layer a of the laminate film X1, and was adjusted so as to enter the initial drying oven in 0.5 second. After drying at 100 ℃ for 2 seconds in an initial drying oven, the mixture was continuously subjected to a heat curing process and heated at 130 ℃ for 7 seconds. After the heat curing step, the film was wound into a roll shape after 8 seconds to obtain a release film for producing an ultrathin ceramic green sheet. The results of measuring the film thickness, surface roughness, surface free energy, curl, and the like of the obtained release film are shown in table 1. The obtained release film was coated with ceramic slurry and evaluated for coatability, releasability, and pinhole, and good evaluation results were obtained.

(coating solution 1) solid content 1.0 mass%, surface tension: 27mN/m, viscosity 5 mPas

(examples 2 to 4, comparative examples 1 and 7)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the composition of coating liquid 1 was changed to the ratio shown in table 1. The results of evaluation of the obtained release film were as follows: the examples containing the silicone release agent also showed good results in terms of peel strength; however, in comparative example 1 which did not contain a silicone release agent, the result was that the peeling force was high, and defects such as pinholes were likely to occur when the ceramic green sheet was peeled from the release film. Further, comparative example 7, which contained a small amount of silicone-based mold release agent and had a low Si element ratio on the surface of the mold release layer, exhibited poor in-plane peeling uniformity.

(examples 5 to 7, comparative example 2)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the resin ratio of coating liquid 1 was changed to table 2 for the solid content and the amount of the release layer applied (solid content) was changed.

The results of evaluation of the obtained release film were as follows: the amount of the release layer applied was 0.2g/m²The following examples, good results with no curl; however, the amount of the release layer applied was 0.75g/m²Comparative example 2 (a) shows a deterioration result with a large curl. In comparative example 2, it was found that the content of the silicone-based release agent contained in the release layer was large, the Si element ratio at the outermost surface of the release layer was high, and the release stability tended to deteriorate.

(example 8)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating solution 1 was changed to the coating solution 8.

(coating liquid 8)

(example 9)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating solution 1 was changed to the coating solution 9.

(coating liquid 9)

(example 10)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating solution 1 was changed to the coating solution 10.

(coating liquid 10)

(example 11)

A release film for producing AN ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the resin solution a of the coating solution 1 was changed to 6AN-5000 (acrylic resin containing no long-chain alkyl group) to obtain a coating solution 11.

(coating liquid 11)

(example 12)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating solution 1 was changed to the coating solution 12.

(coating liquid 12)

As in examples 8 to 12, good results were obtained even when the binder component was changed. In the examples in which the binder component contains a resin having a long-chain alkyl group or a silicone skeleton, even when processed under the same conditions, the surface protrusions tend to be less changed.

(example 13)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating liquid 1 was changed to the coating liquid 13.

(coating liquid 13)

(example 14)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating solution 1 was changed to the coating solution 14.

(coating liquid 14)

(example 15)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the coating liquid 1 was changed to the coating liquid 15.

(coating liquid 15)

Although examples 13 to 15 in which the types of silicone release agents were changed gave good evaluation results, examples containing no hydroxyl group that reacted with the crosslinking agent (melamine in this example) tended to have a high Si element ratio at the outermost surface of the release layer and improved peelability under the same conditions.

(examples 16 to 18, comparative example 3)

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1, except that the base film of example 1 was changed to the base film described in table 1.

As a result of evaluation of the obtained release film, examples 1 to 15 and 16 to 18 using X1, X2, X3 and X5 containing no particles in the surface layer A of the base film had low Sa and P on the surface of the release layer and had good pinhole evaluation; on the other hand, in comparative example 3 in which the surface layer a of the base film contained X4 of particles and the release layer was thin with a small coating amount, both Sa and P on the surface of the release layer were high, and the pinhole evaluation was poor.

(examples 19 to 22, comparative examples 4 and 5)

With respect to the production conditions of example 1, a release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 1 except that the time from coating to placing in the initial drying furnace, or the temperature and passage time of the initial drying furnace were changed to the conditions shown in table 2.

Comparative example 6

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in example 11, except that the production conditions of example 11 were changed to the conditions shown in table 1.

Comparative example 8

A release film for producing an ultrathin ceramic green sheet was produced in the same manner as in comparative example 4, except that the content of the silicone-based release agent was changed to the content shown in table 1.

As a result of evaluation of the obtained film, in the examples in which the time from the coating to the initial drying furnace was set to 1.5 seconds or less and the passage time of the initial drying furnace was set to 1.0 seconds or more and 3.0 seconds or less, the surface roughness Sa of the surface of the release layer, the maximum protrusion height P, and the pinhole evaluation were good; on the other hand, in the comparative examples except the above conditions, it was found that the aggregation of the release layer, the surface roughness Sa of the release layer, and the maximum protrusion height P were increased. In comparative examples 4 and 8 in which the passage time in the initial drying step was short, it was found that the deposition of the silicone-based release agent on the surface of the release layer was small and the Si element ratio at the outermost surface of the release layer tended to be low. In particular, in comparative example 8, the Si element ratio at the outermost surface of the release layer was decreased, and the release stability was poor.

[ Table 1]

PDMS: PDMS polydimethylsiloxane

[ Table 2]

[ Table 3]

Industrial applicability

According to the present invention, a release film having high smoothness and excellent releasability can be provided by curing a composition containing at least a binder component and a silicone-based release agent as a release layer of a release film for producing a ceramic green sheet, while suppressing deterioration of surface roughness due to aggregation of the components during drying. The present invention provides a ceramic green sheet having a film thickness of 0.2 to 1.0 μm, which is excellent in releasability and can reduce defects such as pinholes in the ceramic green sheet.

Claims

1. A release film for producing a ceramic green sheet, comprising a polyester film as a base material, at least one surface of which has a surface layer A substantially free of particles, a release layer being directly laminated on the surface of the surface layer A of the at least one surface or laminated with another layer interposed therebetween,

the releasing layer is formed by curing a composition containing a binder component and a silicone-based releasing agent,

the silicone release agent comprises a silicone resin having a polyether moiety, a carboxyl group or a non-reactive ester group,

the Si element ratio on the surface of the release layer is 2.0 at% to 10.0 at%, the maximum protrusion height (P) on the surface of the release layer is 50nm or less, and the region average roughness (Sa) is 1.5nm or less.

2. The release film for producing a ceramic green sheet according to claim 1, wherein the silicone-based release agent is a silicone-based resin having a polyether moiety or a carboxyl group.

3. The release film for producing a ceramic green sheet according to claim 1, wherein the release layer contains 1 to 15mg/m²Derived from a silicone-based release agent.

4. The release film for manufacturing a ceramic green sheet according to claim 1, wherein the binder component contains a resin having a long chain alkyl group and/or a silicone skeleton.

5. A method for producing a ceramic green sheet, which comprises molding a ceramic green sheet using the release film for producing a ceramic green sheet according to any one of claims 1 to 4, wherein the molded ceramic green sheet has a thickness of 0.2 to 1.0 μm.

6. A method for producing a ceramic capacitor, which comprises using the method for producing a ceramic green sheet according to claim 5.