Release film with antistatic layer

Abstract

This invention provides a release film that can prevent pinholes and localized thickness variations, and maintain antistatic properties, even when ceramic green sheets are made into thin films. [Solution] A release film having a base material, an antistatic layer, and a release layer in that order, wherein the composition forming the antistatic layer comprises an antistatic agent, a melamine compound, a silane coupling agent, and an acid catalyst, the antistatic agent comprises an alkoxysilane hydrolyzed polycondensate and a polystyrene sulfonic acid compound, the alkoxysilane hydrolyzed polycondensate is obtained by hydrolyzing and polycondensing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, having a siloxane bond as its backbone, the melamine compound content being 2.0% by mass or more and 20% by mass or less, and the surface resistivity (logΩ / □) of the antistatic layer and the release layer being 5 or more and 12 or less.

Description

Technical Field

[0001] The present invention relates to a release film for manufacturing a ceramic green sheet. More specifically, it relates to a release film with an antistatic layer that can provide good releasability and suppression of charging even when a resin sheet such as a ceramic green sheet is made thinner.

Background Art

[0002] Generally, in the manufacturing process of multilayer ceramic capacitors, it is common to mold a ceramic slurry or the like on a release film, once make it into a roll state, and then proceed to the next process. In recent years, as the thinning of ceramic green sheets has progressed, not only the smoothness of the surface of the release layer but also the smoothness of the back surface of the release film (the side opposite to the release layer is called the back surface of the release film) that comes into contact with the ceramic green sheet in the roll state has been attracting attention. On the other hand, a release film with high surface smoothness is likely to cause problems such as blocking when wound into a roll and charging when the roll is unwound. When such charging occurs, there is a possibility that the ceramic green sheet may break during the peeling process of the ceramic green sheet. In order to prevent such problems, it is known to impart an antistatic function by incorporating an antistatic agent or the like into the release film.

[0003] For example, Patent Documents 1 and 2 disclose techniques for providing an antistatic layer on the release layer side to impart an antistatic function. Furthermore, Patent Document 3 discloses a technique for imparting an antistatic function to the back surface of the film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] In the antistatic release film shown in Patent Document 1, the components contained in the antistatic layer may aggregate, potentially leading to the antistatic layer detaching during release layer processing, deterioration of the smoothness of the release layer surface, and inhibition of curing due to the influence of the antistatic layer, which could result in a deterioration of release performance. Similarly, in the antistatic film shown in Patent Document 2, an antistatic agent is added to the release layer, which may lead to a deterioration in release performance. In the antistatic release film described in Patent Document 3, an antistatic layer has been formed by applying an alkylammonium salt or the like to the base material of the release film by in-line coating during the base material manufacturing process in order to impart antistatic properties to the release film. By providing an antistatic layer on the back surface, adverse effects on the surface of the release layer are eliminated, but because the surface of the antistatic layer is not slippery, the antistatic layer is prone to falling off due to contact with guide rolls, etc., during ceramic green sheet molding, and this may lead to the generation of foreign matter. Furthermore, in recent years, demand for release films used in the manufacture of multilayer ceramic capacitors has been increasing worldwide, which could lead to longer product transport times. Long-term storage in roll form can cause stress on the film, potentially leading to the detachment of the antistatic layer and deterioration of its antistatic properties and slipperiness.

[0006] This invention was made against the backdrop of the problems of the prior art. Specifically, the object of this invention is to provide a release film that has good adhesion of the antistatic layer, good release properties of the release layer, high smoothness, and antistatic properties. [Means for solving the problem]

[0007] The present invention can be shown in the following embodiments. [1] A release film having a polyester substrate, an antistatic layer on one surface of the substrate, and a release layer in that order, The antistatic layer is formed by curing an antistatic layer forming composition. The antistatic layer forming composition comprises an antistatic agent (A), a melamine compound (B), a silane coupling agent (C), and an acid catalyst (D). The antistatic agent (A) comprises an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2). The aforementioned alkoxysilane hydrolysis polycondensate (A-1) is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, and then by a polycondensation reaction, and has a siloxane bond (Si-O-Si) as its backbone. The content of the melamine compound (B) in the total solid content of the antistatic layer forming composition is 2.0% by mass or more and 20% by mass or less. The surface resistivity (logΩ / □) of the antistatic layer is 5 or more and 12 or less. A release film wherein the surface resistivity (logΩ / □) on the side of the release layer opposite to the antistatic layer is 5 or more and 12 or less. [2] In the antistatic layer, the average surface roughness (Sa) of the region on the side opposite to the substrate is 0.1 nm or more and 5 nm or less, and the maximum protrusion height (P) is 1 nm or more and 100 nm or less. In the aforementioned release layer, the average surface roughness (Sa) of the region on the side opposite to the antistatic layer is 0.1 nm or more and 5 nm or less, and the maximum protrusion height (P) is 1 nm or more and 100 nm or less. The release film described in item 1 above. [3] The release film according to any one of [1] to [2] above, wherein the content of the antistatic agent (A) is 60% by mass or more and 99% by mass or less of the total solid content of the antistatic layer forming composition. [4] The release film according to any one of [1] to [3] above, wherein the content of the silane coupling agent (C) is 2.5% by mass or more and 30% by mass or less in 100% by mass of the total solid content of the antistatic layer forming composition. [5] The release film according to any one of [1] to [4] above, wherein the surface layer on which the antistatic layer of the polyester substrate is laminated is a surface layer that substantially does not contain particles. [Effects of the Invention]

[0008] According to the present invention, a release film with an antistatic layer is provided that is suitable for manufacturing resin sheets, such as ceramic green sheets, and provides good adhesion of the antistatic layer, good release properties, and suppression of static charge, whether the ceramic green sheet is made into a thin film or a resin sheet such as a ceramic green sheet is made into a thin film. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. The release film with an antistatic layer of the present invention (sometimes simply referred to as a release film) has the following features. A release film having a polyester substrate, an antistatic layer on one surface of the substrate, and a release layer in that order, The antistatic layer is formed by curing an antistatic layer forming composition. The antistatic layer forming composition comprises an antistatic agent (A), a melamine compound (B), a silane coupling agent (C), and an acid catalyst (D). The antistatic agent (A) comprises an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2). The aforementioned alkoxysilane hydrolysis polycondensate (A-1) is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, and then by a polycondensation reaction, and has a siloxane bond (Si-O-Si) as its backbone. In 100% by mass of the total solid content of the antistatic layer-forming composition, the content of the melamine compound (B) is 2.0% by mass or more and 20% by mass or less, the surface resistivity (logΩ / sq) of the antistatic layer is 5 or more and 12 or less, A release film in which the surface resistivity (logΩ / sq) on the surface of the release layer opposite to the antistatic layer is 5 or more and 12 or less. In one aspect, the release film with an antistatic layer of the present invention is a release film with an antistatic layer for manufacturing a ceramic green sheet.

[0010] For the release film with an antistatic layer of the present invention, it is possible to suppress the deterioration of the smoothness of the surface of the release layer and also suppress the inhibition of the curing of the release layer due to the influence of the antistatic layer. Therefore, the present invention can exhibit excellent release performance while having antistatic properties. In addition, since the present invention does not contain an antistatic agent in the release layer, the release layer can exhibit high smoothness and releasability without degrading the release performance. Furthermore, since the present invention laminates a polyester base material, an antistatic layer, and a release layer in this order, it is possible to suppress the peeling off of the antistatic layer that may occur due to contact with a guide roll or the like during the molding of the ceramic green sheet. Therefore, the generation of foreign matter during the molding of the ceramic green sheet can also be suppressed. In addition, the present invention is suitable for long-term storage and transportation in a roll state, for example, when transporting the release film from Japan to overseas. For example, it is possible to suppress the peeling off of the antistatic layer from the film during transportation.

[0011] (Base material) In the present invention, the film preferably used as a base material is a film made of polyester resin, and is preferably a polyester film mainly containing at least one selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Alternatively, it may be a film made of polyester in which a third component monomer is copolymerized as part of the dicarboxylic acid component or diol component of the polyester as described above. Among these polyester films, polyethylene terephthalate film is the most preferred in terms of the balance between physical properties and cost.

[0012] Furthermore, the polyester film may be single-layered or multi-layered. In addition, within the range that the desired effects of the present invention are achieved, various additives may be included in the polyester resin of each of these layers as needed. Examples of additives include antioxidants, lightfastness agents, gelation inhibitors, organic wetting agents, antistatic agents, and ultraviolet absorbers. The polyethylene terephthalate film used as the base material in this invention substantially contains no particles with a particle size of 1.0 μm or larger. When the base material has a multilayer structure, the layer forming the surface in contact with the release layer substantially contains no particles with a particle size of 1.0 μm or larger. Hereinafter, whether the base material has a single-layer or multilayer structure, the layer forming the surface in contact with the release layer preferably exhibits the following characteristics. Furthermore, the substrate may contain particles with a particle size of less than 1.0 μm but larger than 1 nm. By substantially free of particles with a particle size of 1.0 μm or larger, such as inorganic particles, the release layer can exhibit high smoothness and release properties, and the transfer of particle shapes from the substrate to resin sheets such as green sheets can be reduced, thereby reducing defects.

[0013] In one embodiment, by not including particles with a particle size of less than 1.0 μm in the substrate, it is possible to more effectively suppress defects caused by the transfer of the particle shape in the substrate to the resin sheet.

[0014] In one embodiment, the substrate of the present invention, for example, a polyethylene terephthalate film, is preferably a film that is substantially free of inorganic particles. This makes it possible to more effectively suppress defects caused by the transfer of the particle shape in the substrate to the resin sheet.

[0015] For example, a substrate that substantially does not contain particles with a particle size of less than 1.0 μm is preferably one that also substantially does not contain particles with a particle size of 1.0 μm or larger.

[0016] In this invention, "substantially free of particles" means, for example, in the case of inorganic particles smaller than 1.0 μm, that the content of inorganic elements is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit, when quantified by fluorescence X-ray analysis. This is because even without actively adding particles to the film, contaminants originating from foreign substances, or dirt adhering to the raw material resin or the lines and equipment in the film manufacturing process, may peel off and become mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or larger" means that the film does not actively contain particles with a particle size of 1.0 μm or larger.

[0017] Preferably, the surface layer on which the antistatic layer of the polyester substrate is laminated is a surface layer that is substantially free of particles. In another embodiment, the polyester substrate may have a surface layer and an intermediate layer, the surface layer being a surface layer that is substantially free of particles, or a surface layer that is substantially free of particles with a particle size of less than 1.0 μm, and the intermediate layer may contain recycled resin.

[0018] (Antistatic layer) The release film with an antistatic layer of the present invention has an antistatic layer laminated on one surface of a polyester substrate. By laminating the antistatic layer, the adhesion of foreign matter can be suppressed, and peeling defects due to electrostatic force can be further suppressed. As described later, by providing the antistatic layer, the adhesion between the antistatic layer and the substrate can be improved, and the detachment of the antistatic layer can be suppressed.

[0019] The antistatic layer is formed by curing an antistatic layer-forming composition, which comprises an antistatic agent (A), a melamine compound (B), a silane coupling agent (C), and an acid catalyst (D). The antistatic agent (A) comprises an alkoxysilane hydrolyzed polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2). Alkoxysilane hydrolysis polycondensate (A-1) is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, followed by a polycondensation reaction, and has a siloxane bond (Si-O-Si) as its backbone. The antistatic layer-forming composition contains 2.0% to 20% by mass of melamine compound (B) in 100% by mass of total solids.

[0020] The means for laminating the antistatic layer are not particularly limited, and known methods such as coating, vacuum deposition, and bonding can be used. For example, applying a coating solution containing an antistatic agent by coating is preferable from the viewpoint of shortening the manufacturing process and ensuring stable film formation.

[0021] (Antistatic agent (A)) The antistatic agent (A) contains an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2). In the present invention, the alkoxysilane hydrolysis polycondensate (A-1) is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, and then by a polycondensation reaction, and has a siloxane bond represented by formula 1 as its backbone. (Si-O-Si) (Equation 1) When phenylalkoxysilane and / or its oligomer are mixed with tetraalkoxysilane and / or its oligomer, the compatibility and adhesion of the alkoxysilane hydrolysate polycondensate (A-1) with polystyrene sulfonic acid compound (A-2) is improved. For this reason, it is preferable to use phenylalkoxysilane and / or its oligomer. Furthermore, the antistatic performance can be improved by adding a polystyrene sulfonic acid compound. For example, by including an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2) in the antistatic agent (A), the aggregation of components in the antistatic layer can be suppressed, and the detachment of the antistatic layer during release layer processing can be avoided. In addition, the smoothness of the antistatic layer can be maintained. Therefore, deterioration of the smoothness of the release layer surface can be suppressed, and inhibition of the release layer hardening caused by the antistatic layer can also be suppressed. Furthermore, since the antistatic agent (A) contains an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2), it is anticipated that the film will be subjected to stress when the product is stored in a roll for a long period of time, especially during product transport. The present invention can suppress the detachment of the antistatic layer caused by stress that may occur not only during roll winding and unwinding, but also during long-term storage in a roll. Furthermore, different antistatic agents can be used in combination, as long as they do not impair the effects of the antistatic agent according to the present invention. The antistatic agent may also be a polymer utilizing ion conduction, such as a cationic compound, or a π-electron conjugated conductive polymer, in addition to the antistatic agent of the present invention. Surfactants, silicon dioxide compounds, conductive metal compounds, etc., can also be used.

[0022] The tetraalkoxysilanes and their oligomers used in the present invention can be represented by the following formulas: Si(OR1)4 and SinOn-1(OR1)2n+2, respectively. In these formulas, each R1 may be the same or different, and independently of each other, represents an alkyl group having 1 to 6 carbon atoms. For the oligomers, low condensation groups with n=2 to 10 are used. Specific examples of tetraalkoxysilanes and their oligomers used in the present invention include, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, with tetramethoxysilane and tetraethoxysilane being particularly preferred. Such silanes having a methoxy group or an ethoxy group can be obtained inexpensively, and can also smoothly carry out (co)hydrolysis reactions even in the presence of phenylalkoxysilane.

[0023] Tetraalkoxysilane oligomers can be obtained by hydrolysis and condensation reactions of these alkoxysilane monomers, and as described above, 2 to 10-mer oligomers are preferably used. Commercially available products include methyl silicate 51, an average tetramer oligomer of tetramethoxysilane, and ethyl silicate 40, an average pentamer oligomer of tetraethoxysilane, and these are preferably used. In the present invention, alkoxysilane and its oligomer may be used individually or as a mixture.

[0024] The phenylalkoxysilane used in combination with tetraalkoxysilane and / or its oligomer in the implementation of the present invention is given by the following formula 2: PhnSi(OR2) 4-n (Formula 2) (In formula 2, Ph represents a phenyl group, R2 may be the same or different, and each independently represents an alkyl group having 1 to 6 carbon atoms, and n is an integer between 1 and 2.) This is expressed as follows. Furthermore, 2 to 10-mers can be used as oligomers of phenylalkoxysilane.

[0025] Specific examples of phenylalkoxysilanes include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, and phenyltri-n-butoxysilane, but phenyltrimethoxysilane and phenyltriethoxysilane are preferred. These methoxysilanes and ethoxysilanes have the advantage of proceeding smoothly because their reaction rates are similar in the co-hydrolysis reaction with the tetraalkoxysilanes mentioned above. Diphenyldialkoxysilanes, in which two phenyl groups are bonded to silicon (Si), can also be used, but in this case as well, methyl or ethoxy groups are preferred for the alkoxy groups. For oligomers, dimers or trimers of the above-mentioned phenylalkoxysilanes are desirable. In the case of phenylalkoxysilanes, phenylalkoxysilanes and their oligomers may be used individually or as a mixture.

[0026] When preparing hydrolyzed polycondensates, the ratio of tetraalkoxysilane and / or oligomer to phenylalkoxysilane and / or its oligomer is usually preferably in the range of approximately 1:0.1 to 1 by weight. Using more phenylalkoxysilane than tetraalkoxysilane reduces adhesion to the substrate. Conversely, lowering the ratio below this range is undesirable because, although there are no problems in terms of adhesion, it results in reduced water resistance. In the present invention, the alkoxysilane hydrolysis polycondensate (A-1) formed by polycondensation reaction has a siloxane bond (Si-O-Si) as its backbone.

[0027] Polystyrene sulfonic acid compounds (hereinafter also abbreviated as "PSS") refer to polymers obtained by sulfonating polystyrene compounds.

[0028] The sulfonic acid groups of polystyrene sulfonic acid compounds form ion pairs with hydrogen or monovalent alkali metals, and the weight-average molecular weight (Mw) of the polystyrene sulfonic acid compounds is in the range of approximately 10,000 to 100,000. A preferred molecular weight range is approximately 60,000 to 80,000.

[0029] Polystyrene sulfonic acid is soluble in water, alcohols, ketones, esters, etc., and is usually commercially available as a solution or dispersion containing approximately 10-30% by weight of polystyrene sulfonic acid in these solvents. The properties of such liquids are a pH of 9.0 or less, and a viscosity of approximately 150 mPa·s or less, which varies depending on the concentration of PSS and the type of solvent. The amount of PSS used is preferably about 0.5-30.0% by weight, particularly 3.0-20.0% by weight, relative to the weight of the polycondensate of tetraalkoxysilane and / or oligomer and phenylalkoxysilane and / or its oligomer. If the amount of PSS added is increased beyond the above range, the antistatic effect will not improve, the water resistance will decrease significantly, and the adhesion to the substrate will decrease. Conversely, if the amount added is reduced below the above range, the required antistatic effect will not be achieved, which is undesirable.

[0030] As a coating solution containing the aforementioned components, commercially available products such as Colcoat PS-169 (manufactured by Colcoat Co., Ltd.), Colcoat PS-903 (manufactured by Colcoat Co., Ltd.), and Colcoat PC-301 may be used.

[0031] The antistatic agent (A), which is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, and then undergoing a polycondensation reaction, and which contains an alkoxysilane hydrolysis polycondensate (A-1) having a siloxane bond (Si-O-Si) as its backbone, and a polystyrene sulfonic acid compound (A-2), is preferably present in an amount of 60% by mass or more, more preferably 68% by mass or more, when the total solid content in the antistatic layer, i.e., the sum of the solid content of the antistatic agent (A), melamine compound (B), silane coupling agent (C), and acid catalyst (D), is taken as 100% by mass. Even more preferably, it is present in an amount of 70% by mass or more. By including an antistatic agent in this amount, good antistatic properties can be imparted. Furthermore, adding this amount reduces minute irregularities originating from the antistatic layer, allowing for the formation of a highly smooth antistatic layer, which is preferable.

[0032] In the present invention, the amount of antistatic agent (A) contained in the antistatic layer is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on 100% by mass of the total solid content in the antistatic layer. Including an antistatic agent in this amount is preferable because it suppresses the curing inhibition of the acid catalyst (D), which will be described later, and the antistatic coating becomes harder, resulting in good powder-shedding properties. Although the effect of the acid catalyst on curing is not clear, we believe that cation exchange occurs between the polystyrene sulfonate and the acid catalyst, thereby inhibiting its effectiveness as an acid catalyst. In one embodiment, the antistatic agent (A) may be 85% by mass or less relative to 100% by mass of the total solids content in the antistatic layer. This setting of antistatic agent content allows for better solvent resistance and abrasion resistance of the antistatic layer. Good solvent resistance and abrasion resistance allow for smaller average surface roughness (Sa) and maximum protrusion height (P) in the release layer, resulting in a highly smooth release film.

[0033] (Melamine compound) This invention involves laminating an antistatic layer and a release layer in that order on one surface of a substrate. By improving the adhesion between the substrate and the antistatic layer, the detachment of the antistatic layer during release processing can be suppressed. For example, by improving the adhesion between the substrate and the antistatic layer, detachment of the antistatic layer that may occur due to contact with guide rolls or coated areas during release layer formation can also be suppressed. By preventing detachment during release processing in this way, the generation of foreign matter during the ceramic green sheet molding process, which is a customer process, can also be suppressed. In addition, it is suitable for long-term storage in a rolled state, for example, and can prevent the antistatic layer from peeling off the film. Thus, the present invention can provide a release film equipped with an antistatic layer that is less likely to peel off even when subjected to external factors such as friction. In the present invention, in order to adhere the antistatic layer to the substrate, it is preferable that the antistatic layer be formed from a composition containing a melamine compound. Including a melamine compound is preferable because it improves durability and suppresses the deterioration of antistatic performance even when processed under high temperature and high humidity conditions. The melamine compound used in the antistatic layer in the present invention can be any common compound and is not particularly limited, but it is preferable that it is obtained by condensing melamine and formaldehyde and has one or more triazine rings and one or more methylol groups and / or alkoxymethyl groups in one molecule. Specifically, it is preferable to use a compound obtained by dehydrating and condensing a methylolmelamine derivative obtained by condensing melamine and formaldehyde with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol to obtain an ether. Examples of methylolated melamine derivatives include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, and hexamethylolmelamine. You may use one type or two or more types. In one embodiment, a thermosetting resin selected from compounds other than melamine compounds may be used in combination. Examples of thermosetting resins include acrylamide resins, polycarbodiimide resins and oxazoline resins, urea-based, epoxy-based, isocyanate-based, polycarbodiimide-based, and aziridine-based resins. Furthermore, catalysts and the like may be used as needed to promote the crosslinking reaction.

[0034] The melamine used in this invention can also be commercially available. For example, Cymel 300, Cymel 301, Cymel 303LF, Cymel 350, Cymel 370N, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 701, Cymel 266, Cymel 267, Cymel 285, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 272, Cymel 212, Cymel 253, Cymel 254, Cymel 202, Cymel 207 (manufactured by Ornex Japan Co., Ltd.), Nikarac MW-30M, Nikarac MW-30, Nikarac MW-30HM, Nikarac MW-390, Examples include Nikarac MW-100LM, Nikarac MA-1-750LM, Nikarac MW-22, Nikarac MS-21, Nikarac MS-11, Nikarac MW-24A-1, Nikarac MS-001, Nikarac MA-1-002, Nikarac MA-1-730, Nikarac MA-1-750, Nikarac MA-1-708, Nikarac MA-1-706, Nikarac MA-1-042, Nikarac MA-1-035, Nikarac MA-1-45, Nikarac MA-1-43, Nikarac MA-1-417, and Nikarac MA-1-410 (manufactured by Nippon Carbide Co., Ltd.). Among these, full-ether type methylated melamine resins are preferred in terms of reactivity and adhesion with the substrate, antistatic agent, and silane coupling agent. Examples of commercially available products include the Cymel 303LF and the Nikalac MW-30.

[0035] The melamine compound contained in the antistatic layer of the present invention has a content of 2.0% to 20% by mass when the total solid content of the antistatic agent (A), melamine compound (B), silane coupling agent (C), and acid catalyst (D) is taken as 100% by mass. The melamine compound is more preferably present in an amount of 5.0% by mass or more relative to 100% by mass of the total solids content in the antistatic layer. An amount of 2.0% by mass or more is preferable as it provides a stronger coating film with a higher crosslinking density as an antistatic layer, resulting in good adhesion to the substrate and good solvent resistance. It is also preferable because it improves adhesion to the release layer laminated on the antistatic layer. Furthermore, an amount of 5.0% by mass or more is preferable because it results in an even stronger coating film, thus improving antistatic performance and resistance to shedding over time.

[0036] The melamine compound is preferably present in the antistatic layer at an amount of 20% by mass or less, and may be 15% by mass or less, based on 100% by mass of the total solids content. An amount of 20% by mass or less is preferable because it does not affect the antistatic performance. If the amount exceeds 20% by mass, a reaction with the hydroxyl groups of polysiloxane may proceed, potentially impairing the antistatic performance.

[0037] (Silane coupling agent) This invention involves laminating an antistatic layer and a release layer in that order on one surface of a substrate. By improving the adhesion between the substrate and the antistatic layer, the detachment of the antistatic layer during release processing can be suppressed. For example, by improving the adhesion between the substrate and the antistatic layer, detachment of the antistatic layer that may occur due to contact with guide rolls or coated areas during release layer formation can also be suppressed. By preventing detachment during release processing in this way, the generation of foreign matter during the ceramic green sheet molding process, which is a customer process, can also be suppressed. In addition, it is suitable for long-term storage in a rolled state, for example, and can prevent the antistatic layer from peeling off the film. Thus, the present invention can provide a release film equipped with an antistatic layer that is less likely to peel off even when subjected to external factors such as friction. In the present invention, in order to adhere the antistatic layer to the substrate, it is preferable that the antistatic layer be formed from a composition containing a melamine compound in addition to a silane coupling agent. Inclusion of a silane coupling agent is preferable because it allows for the formation of a strong coating film without degrading the antistatic performance. A silane coupling agent represented by formula (3) is preferably used.

[0038] [ka] (Formula 3)

[0039] In formula (3), R3 is a C1-C3 alkyl group (C1-C3 alkyl group) or acyloxy group which may be substituted with an alkoxy group (preferably a C1-C3 alkoxy group), Y is a glycidyloxy group, epoxy group, amino group, vinyl group, allyl group, (meta)acryloyloxy group, mercapto group, isocyanate group or ureido group, or C1-C3 alkylthio group, p is an integer from 0 to 2, and q is an integer from 0 to 3.

[0040] A particularly preferred example of the silane coupling agent of formula (3) is a silane coupling agent in which R3 is a methyl group, Y is a glycidyloxy group, p is 0, and q is 3. This structure is preferable because it not only improves adhesion to the polyester substrate but also allows for the formation of a strong coating film by reacting with the antistatic agent and melamine compound in the antistatic layer.

[0041] In one embodiment, a silane coupling agent selected from those other than the above-mentioned silane coupling agent may be used in combination. For example, a silane coupling agent in formula (3) in which R3 is an acetoxy group, Y is a vinyl group, p is 0, and q is 0 can be cited. This structure is preferable because it reacts with the antistatic agent and melamine in the antistatic layer to form a strong coating film, and also reacts with the release layer laminated in a subsequent process to improve adhesion.

[0042] The silane coupling agent contained in the antistatic layer of the present invention has a content of 2.5% by mass or more and 30% by mass or less when the total solid content of the antistatic agent (A), melamine compound (B), silane coupling agent (C), and acid catalyst (D) is taken as 100% by mass. The silane coupling agent is more preferably 5.0% by mass or more relative to 100% by mass of the total solid content in the antistatic layer. When a silane coupling agent is used in combination, the silane coupling agent content specified in this application refers to the total amount of silane coupling agents used in combination. A crosslinking density of 2.5% by mass or more is preferable because it results in a stronger coating film with higher crosslinking density, better adhesion to the substrate, and better solvent resistance. Furthermore, a crosslinking density of 5.0% by mass or more is preferable because it results in an even stronger coating film, which also improves antistatic performance and resistance to shedding over time.

[0043] The silane coupling agent is preferably included in the antistatic layer at an amount of 30% by mass or less, and more preferably 25% by mass or less, relative to 100% by mass of the total solid content. When the amount is 30% by mass or less, the generation of aggregates derived from the silane coupling agent is suppressed, and a highly smooth antistatic layer can be formed.

[0044] (Acid catalyst) In the present invention, it is preferable to add an acid catalyst to the antistatic layer to promote the crosslinking reaction of the melamine compound and the hydrolysis of the antistatic agent and silane coupling agent. It is preferable to add the acid catalyst to the antistatic layer forming composition, apply it, and cure it. The acid catalyst used is not particularly limited, and existing acid catalysts can be used, but it is preferable to use a sulfonic acid-based catalyst.

[0045] As sulfonic acid catalysts, for example, p-toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and trifluoromethanesulfonic acid can be suitably used, but from the viewpoint of reactivity, p-toluenesulfonic acid can be particularly suitably used.

[0046] Sulfonic acid-based catalysts have higher acidity and superior reactivity compared to other acid catalysts such as carboxylic acid-based catalysts, allowing for the processing of antistatic layers at lower temperatures. This is preferable because it suppresses the deterioration of film flatness and winding appearance caused by heat during processing.

[0047] The sulfonic acid catalyst used in this invention can also be a commercially available one. Examples of commercially available products include Dryer® 900 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd.), NACURE® DNNDSA series (dinonylnaphthalenedisulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), NACURE® DNNSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), NACURE® DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), and NACURE® p-TSA series (p-toluenesulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.).

[0048] In addition to the above, the antistatic layer may contain, as necessary, lubricants, dyes, ultraviolet absorbers, etc., to the extent that it does not hinder the objectives of the present invention.

[0049] The thickness of the antistatic layer of the present invention is preferably 40 nm to 150 nm. More preferably, it is 50 nm to 100 nm. A thickness of 40 nm or more is preferable because it provides an antistatic effect. On the other hand, a thickness of 150 μm or less is preferable because it suppresses the generation of aggregates originating from the antistatic layer.

[0050] The surface resistivity of the antistatic layer of the present invention is 12 [logΩ / □] or less. More preferably, it is 11 [logΩ / □] or less, and even more preferably, 10 [logΩ / □] or less. By making the surface resistivity 12 [logΩ / □] or less, static charge on the film can be suppressed, and foreign matter adhesion during the process can be prevented. Furthermore, by making it even smaller, such as 11 [logΩ / □] or less, or 10 [logΩ / □] or less, product defects due to static charge during the manufacturing of ceramic green sheets can be reduced, which is preferable.

[0051] Furthermore, while there is no specific lower limit for the surface resistivity of the antistatic film, it is preferable that it be 5.0 [logΩ / □] or higher. A surface resistivity of 5.0 [logΩ / □] or higher is preferable because it may prevent short circuits in the ceramic green sheet when the antistatic agent is transferred to the ceramic green sheet. In one embodiment, the surface resistivity of the antistatic film is 5.2 [logΩ / □] or higher, and may be, for example, 5.5 [logΩ / □] or higher.

[0052] In one embodiment, it is preferable that the surface resistivity (logΩ / □) of the antistatic layer is smaller than the surface resistivity (logΩ / □) of the release layer on the side opposite to the antistatic layer.

[0053] In the antistatic layer, the average surface roughness (Sa) of the surface opposite to the substrate is preferably 0.1 nm to 5 nm, for example, 0.2 nm to 4.5 nm. The maximum protrusion height (P) is preferably 1 nm to 100 nm, for example, 1 nm to 50 nm. A surface roughness of 5 nm or less, or a maximum protrusion height of 100 nm or less, is preferable because it can suppress deterioration of the smoothness of the release layer during release layer lamination.

[0054] In the present invention, the method for forming the antistatic layer is not particularly limited. A coating solution obtained by dissolving or dispersing the above-mentioned antistatic agent (A), melamine compound (B), silane coupling agent (C), and acid catalyst (D) is applied to one side of a polyester film substrate by coating or the like. After removing the solvent by drying, the coating is heated and dried, and then heat-cured. In this case, the drying temperature during solvent drying and heat curing is preferably 180°C or lower, and more preferably 150°C or lower. The heating time is preferably 30 seconds or less, and more preferably 20 seconds or less. When the temperature is 180°C or lower, the flatness of the film is maintained, and there is little risk of causing uneven thickness in the ceramic green sheet, which is preferable. When the temperature is 150°C or lower, the film can be processed without impairing the flatness of the film, and the risk of causing uneven thickness in the ceramic green sheet is further reduced, which is particularly preferable.

[0055] (Smooth coating layer) The antistatic release film of the present invention may also have a smooth coating layer provided on the surface of the polyester base film described above that is opposite to the surface on which the antistatic layer and the release layer are laminated. By providing a slip-free coating layer as described later, it is possible to reduce the transportability of the film and the load on the ceramic green sheet.

[0056] The smooth coating layer preferably contains at least a binder resin and particles.

[0057] (Binder resin in the lubrication coating layer) In the present invention, the binder resin constituting the smooth coating layer preferably contains an acrylic resin. The acrylic resin is preferably an acrylic resin having hydroxyl groups and carboxyl groups in its molecule. It is even more preferable that the constituent units having hydroxyl groups constitute 20 to 90 mol% of the total constituent units out of 100 mol%. When the constituent units having hydroxyl groups are 20 mol% or more, it is preferable that the water solubility of the acrylic resin can be appropriately maintained. On the other hand, when it is 90 mol% or less, it is preferable that the hydroxyl groups of the acrylic resin and the particles contained in the smooth coating layer do not cause extreme interaction and the particles are uniformly dispersed.

[0058] To introduce hydroxyl groups into acrylic resin, monomers having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, or ring-opening adducts of γ-butyrolactone or ε-caprolactone to 2-hydroxyethyl (meth)acrylate, can be used as copolymerization components. Among these, 2-hydroxyethyl (meth)acrylate is preferred because it does not inhibit water solubility. Two or more of these may be used in combination. Needless to say, the acrylic resin referred to in this invention includes methacrylic resin.

[0059] The hydroxyl value of the acrylic resin is preferably 10 mg KOH / g or more, more preferably 20 mg KOH / g or more, and even more preferably 30 mg KOH / g or more. A hydroxyl value of 10 mg KOH / g or more is preferable because it results in good water solubility of the acrylic resin.

[0060] The hydroxyl value of the acrylic resin is preferably 250 mgKOH / g or less, more preferably 230 mgKOH / g or less, and even more preferably 200 mgKOH / g or less. A hydroxyl value of 250 mgKOH / g or less is preferable because it prevents extreme interaction between the hydroxyl groups of the acrylic resin and the particles contained in the smooth coating layer, resulting in uniform particle dispersion.

[0061] The acrylic resin used in this invention is preferably a resin having carboxyl groups in addition to hydroxyl groups. Having carboxyl groups makes it possible to form a crosslinked structure with a crosslinking agent and to easily impart water solubility. Examples include monomers containing carboxyl groups such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid, and monomers containing acid anhydride groups such as maleic anhydride and itaconic anhydride.

[0062] The monomer having a carboxyl group is preferably present in an amount of 4 mol% or more, and more preferably 10 mol% or more, of 100 mol% of the total constituent units of the acrylic resin. An amount of 4 mol% or more is preferable because it facilitates the formation of a crosslinked structure in the smooth coating layer and imparts water solubility. The monomer having a carboxyl group is preferably present in an amount of 65 mol% or less, and more preferably 50 mol% or less. An amount of 65 mol% or less is preferable because the Tg of the resulting coating film does not become too high compared to the preferred range described later, resulting in good film-forming properties and stretchability in in-line coating.

[0063] To achieve good water solubility, it is preferable to neutralize the carboxyl groups introduced into the acrylic resin by copolymerization of acrylic acid or methacrylic acid. Suitable basic neutralizing agents include amine compounds such as ammonia, trimethylamine, triethylamine, and dimethylaminoethanol, as well as inorganic basic substances such as potassium hydroxide and sodium hydroxide. Of these, amine compounds are preferred as neutralizing agents due to their volatility and ease of cross-linking. Ammonia is the most preferred because it does not cause particle aggregation. The neutralization rate is preferably 30 mol% to 95 mol%, and more preferably 40 mol% to 90 mol%. A neutralization rate of 30 mol% or higher is preferable because it ensures sufficient water solubility of the acrylic resin, facilitates dissolution of the acrylic resin during coating solution preparation, and prevents whitening of the coating surface after drying. On the other hand, a neutralization rate of 95 mol% or lower is preferable because it ensures moderate water solubility, facilitates mixing of alcohols and other substances during coating solution preparation.

[0064] The acid value of the acrylic resin is preferably 40 mg KOH / g or higher, more preferably 50 mg KOH / g or higher, and even more preferably 60 mg KOH / g or higher. An acid value of 40 mg KOH / g or higher is preferable because it increases the number of crosslinking sites with the oxazoline crosslinking agent or carbodiimide crosslinking agent, resulting in a stronger coating film with a higher crosslinking density.

[0065] The acid value of the acrylic resin is preferably 400 mg KOH / g or less, more preferably 350 mg KOH / g or less, and even more preferably 300 mg KOH / g or less. A 400 mg KOH / g or less acid value is preferable because it prevents excessive interaction between the carboxyl groups of the acrylic resin and the particles contained in the smooth coating layer, resulting in uniform particle dispersion. Good particle dispersibility is preferable because it prevents the formation of large protrusions on the smooth coating surface and prevents the formation of pinholes in the ceramic sheet.

[0066] The glass transition temperature (Tg) of the acrylic resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. A glass transition temperature of 50°C or higher is preferable because it results in a moderately high hardness of the smooth coating layer.

[0067] The glass transition temperature (Tg) of the acrylic resin is preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 100°C or lower. A glass transition temperature of 110°C or lower is preferable because it prevents cracks from forming in the coating film during the stretching process after applying the smooth coating layer, resulting in uniform stretching.

[0068] (Meth)acrylic monomers and non-acrylic vinyl monomers can be used as Tg-adjusting monomers copolymerized to bring the Tg within the above range. Specific examples of (meth)acrylic monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and stearyl (meth)acrylate; nitrogen-containing acrylic monomers such as (meth)acrylamide, diacetone acrylamide, n-methylolacrylamide, and (meth)acrylonitrile; and vinyl methacrylate. One or more of these can be used.

[0069] Furthermore, examples of non-acrylic vinyl monomers include styrene monomers such as styrene, α-methylstyrene, vinyltoluene (a mixture of m-methylstyrene and p-methylstyrene), and chlorostyrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl pivalate, vinyl octoate, vinyl monochloroacetate, divinyl adipate, vinyl crotate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate; and halogenated vinyl monomers such as vinyl chloride and vinylidene chloride; one or more of these can be used.

[0070] For adjusting the Tg, it is preferable to determine the appropriate amounts of hydroxyl group-containing monomers and carboxyl group-containing monomers, and then use the remainder. The Tg of the copolymer can be determined using the following Fox formula.

[0071]

number

[0072] For Tg adjustment, it is preferable to introduce components that lower the surface free energy, such as long-chain alkyl groups, as monomers copolymerized. As for acrylic resins with introduced long-chain alkyl groups, those having alkyl groups with approximately 8 to 20 carbon atoms in the side chains of the acrylic resin are preferred. Furthermore, copolymers in which (meth)acrylic acid esters are the main repeating units and which contain long-chain alkyl groups with 8 to 20 carbon atoms in the transesterified portion can also be suitably used.

[0073] For Tg adjustment, the monomer having a long-chain alkyl group in the copolymerized monomer is preferably 50 mol% or less, and more preferably 40 mol% or less, of 100 mol% of the total constituent units of the acrylic resin. A concentration of 50 mol% or less is preferable because it prevents the Tg of the resulting coating film from becoming too low relative to the preferred range, thus maintaining a high level of coating film hardness. In this invention, the monomer having a long-chain alkyl group may be 0 mol% as long as the Tg can be maintained within the preferred range; however, a concentration of 5 mol% or more is preferable because it clearly demonstrates the effect of adjusting the Tg of the acrylic resin.

[0074] The acrylic resin used in this invention can be obtained by known radical polymerization. Emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, etc., can all be used. Solution polymerization is preferred from the viewpoint of ease of handling. Examples of water-soluble organic solvents that can be used for solution polymerization include ethylene glycol n-butyl ether, isopropanol, ethanol, n-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane, 1,3-oxolane, methyl solosolve, ethyl solosolve, ethyl carbitol, butyl carbitol, propylene glycol monopropyl ether, and propylene glycol monobutyl ether. These may also be used mixed with water.

[0075] Any known compound that generates radicals can be used as a polymerization initiator, but water-soluble azo polymerization initiators such as 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide are preferred. The polymerization temperature and time can be selected as appropriate.

[0076] The mass-average molecular weight (Mw) of the acrylic resin is preferably around 10,000 to 200,000. A more preferable range is 20,000 to 150,000. When Mw is 10,000 or higher, there is no risk of thermal decomposition in the tenter, which is preferable. When Mw is 200,000 or lower, there is no significant increase in the viscosity of the coating solution, and the coating properties are good, which is also preferable.

[0077] In the present invention, other binder resins may be used in combination with acrylic resin as the binder for the smooth coating layer. Examples of other binder resins include polyester resin, urethane resin, polyvinyl resin (such as polyvinyl alcohol), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, and starches.

[0078] The content of the acrylic resin in the smooth coating layer is preferably 20% by mass or more and 95% by mass or less of the total solids. More preferably 30% by mass or more and 90% by mass or less. A content of 20% by mass or more is preferable because it does not result in too few carboxyl groups, which are the crosslinking components, and the crosslinking density does not decrease. A content of 95% by mass or less is preferable because it does not result in too few crosslinking agents, which are the targets of crosslinking, and the crosslinking density does not decrease.

[0079] (Crosslinking agent) In the present invention, it is preferable that the smooth coating layer contains at least one crosslinking agent selected from oxazoline-based crosslinking agents or carbodiimide-based crosslinking agents in order to form a crosslinked structure in the smooth coating layer. By including an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent, adhesion to the PET substrate can be improved, and the strength of the coating film of the smooth layer can be improved by promoting crosslinking with the carboxyl groups of the acrylic resin. Other crosslinking agents may also be used in combination, and specific crosslinking agents that can be used in combination include urea-based, epoxy-based, melamine-based, isocyanate-based, and silanol-based agents. Furthermore, catalysts and the like can be used as appropriate as needed to promote the crosslinking reaction.

[0080] Examples of crosslinking agents having oxazoline groups include polymers having oxazoline groups obtained by copolymerizing a polymerizable unsaturated monomer having oxazoline groups with other polymerizable unsaturated monomers as needed using conventionally known methods (e.g., solution polymerization, emulsion polymerization, etc.).

[0081] Examples of polymerizable unsaturated monomers having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These may be used individually or in combination of two or more.

[0082] Other polymerizable unsaturated monomers include, for example, alkyl or cycloalkyl esters of (meth)acrylic acid with 1 to 24 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, and isobornyl (meth)acrylate; hydroxyalkyl esters of (meth)acrylic acid with 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; vinyl aromatic compounds such as styrene and vinyltoluene; adducts of (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate with amines; polyethylene glycol (meth)acrylate; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, and (meth)acrylonitrile. These can be used individually or in combination of two or more types.

[0083] Other polymerizable unsaturated monomers are preferably hydrophilic monomers, from the viewpoint of improving compatibility with other resins, wettability, and crosslinking reaction efficiency when using the resulting oxazoline group-containing crosslinking agent as a water-soluble crosslinking agent. Examples of hydrophilic monomers include monomers having polyethylene glycol chains such as 2-hydroxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, monoester compounds of (meth)acrylic acid and polyethylene glycol, 2-aminoethyl (meth)acrylate and its salts, (meth)acrylamide, N-methylol (meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, (meth)acrylonitrile, and sodium styrene sulfonate. Among these, monomers having polyethylene glycol chains such as methoxypolyethylene glycol (meth)acrylate and monoester compounds of (meth)acrylic acid and polyethylene glycol, which have high solubility in water, are preferred.

[0084] The crosslinking agent having an oxazoline group preferably has an oxazoline group content of 3.0 to 9.0 mmol / g. More preferably, it is in the range of 4.0 to 8.0 mmol / g. A content within the range of 4.0 to 8.0 mmol / g is preferable because it allows for the formation of an appropriate crosslinked structure.

[0085] Examples of carbodiimide-based crosslinking agents include monocarbodiimide compounds and polycarbodiimide compounds. Examples of monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di-β-naphthylcarbodiimide. As for polycarbodiimide compounds, those produced by conventionally known methods can be used. For example, they can be produced by synthesizing isocyanate-terminated polycarbodiimides through a condensation reaction involving the decarbonization of diisocyanates.

[0086] Examples of diisocyanates used as raw materials for the synthesis of polycarbodiimide compounds include isomers of toluene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanate-methyl)cyclohexane, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. Due to the problem of yellowing, aromatic aliphatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates are preferred.

[0087] Furthermore, the above-mentioned diisocyanate may be used after controlling the degree of polymerization of the molecule using a compound that reacts with a terminal isocyanate such as a monoisocyanate. Examples of monoisocyanates used to encapsulate the ends of polycarbodiimide and control its degree of polymerization include phenyl isocyanate, toluene isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate. In addition, compounds having OH groups, -NH2 groups, COOH groups, and SO3H groups can also be used as end-encapsulating agents.

[0088] The condensation reaction of diisocyanates, accompanied by decarbonation, proceeds in the presence of a carbodiimide catalyst. Examples of catalysts include 1-phenyl-2-phosphorene-1-oxide, 3-methyl-2-phosphorene-1-oxide, 1-ethyl-2-phosphorene-1-oxide, 3-methyl-1-phenyl-2-phosphorene-1-oxide, and phosphorene oxides such as their 3-phosphorene isomers. 3-methyl-1-phenyl-2-phosphorene-1-oxide is preferred due to its reactivity. The amount of catalyst used can be catalytic.

[0089] It is desirable that the above-mentioned mono or polycarbodiimide compounds be kept in a uniformly dispersed state when blended into water-based paints. For this purpose, it is preferable to emulsify them using an appropriate emulsifier and use them as an emulsion, or to add hydrophilic segments to the molecular structure of the polycarbodiimide compound and blend it into the paint in the form of a self-emulsifying or self-dissolving product.

[0090] The carbodiimide-based crosslinking agent used in the present invention is characterized by its water dispersibility and water solubility. Water solubility is preferred because it has good compatibility with other water-soluble resins and improves the crosslinking reaction efficiency of the smooth coating layer. To make the carbodiimide compound water-soluble, it can be produced by synthesizing an isocyanate-terminated polycarbodiimide through a condensation reaction involving the decarbonization of isocyanates, and then adding a hydrophilic moiety having a functional group that reacts with isocyanate groups.

[0091] Examples of hydrophilic moieties include (1) quaternary ammonium salts of dialkylamino alcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) alkyl sulfonates having at least one reactive hydroxyl group, and (3) poly(ethylene oxide) with alkoxy groups at the end, and mixtures of poly(ethylene oxide) and poly(propylene oxide). When the above hydrophilic moieties are introduced into a carbodiimide compound, it can be (1) cationic, (2) anionic, or (3) nonionic. Among these, nonionic properties, which allow compatibility regardless of the ionic properties of other water-soluble resins, are preferred.

[0092] The preferred content of the crosslinking agent in the smooth coating layer is 5% by mass or more and 80% by mass or less of the total solid content. More preferably, it is 10% by mass or more and 70% by mass or less. A content of 5% by mass or more is preferable because it does not reduce the crosslinking density of the resin in the coating layer. A content of 80% by mass or less is preferable because it does not reduce the amount of carboxyl groups in the acrylic resin to be crosslinked too much, and thus does not lower the crosslinking density.

[0093] (Particles in the smooth coating layer) The slip-free coating layer preferably contains lubricant particles to impart slipperiness to the surface. The particles may be inorganic or organic, and are not particularly limited, but 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, hydrated halloysite, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, and barium sulfate; and (2) organic particles such as acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester. In terms of preventing particles from detaching from the slippery coating layer, the use of organic particles is particularly preferable. The use of organic particles is preferable because it strengthens the interaction between the binder and crosslinking agent components of the slippery coating layer, making it easier to prevent detachment. Among organic particles, acrylic resin particles and / or methacrylic resin particles, which have a chemical structure similar to the acrylic resin present in the slippery coating layer, are particularly preferable in terms of preventing particles from detaching from the slippery coating layer.

[0094] The average particle size is preferably 10 nm or larger, more preferably 20 nm or larger, and even more preferably 30 nm or larger. An average particle size of 10 nm or larger is preferable because it makes the particles less prone to aggregation and ensures good lubricity.

[0095] The average particle size is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 600 nm or less. An average particle size of 1000 nm or less is preferable because it maintains transparency and prevents particle detachment.

[0096] Furthermore, for example, mixing small particles with an average particle size of about 10 to 270 nm and large particles with an average particle size of about 300 to 1000 nm is preferable in order to achieve both slipperiness and smoothness by reducing the average length of the roughness curve elements (RSm) while keeping the average surface roughness (Sa) and maximum protrusion height (P) of the region low, as described later. Particularly preferable is the combination of small particles with an average particle size of 30 nm to 250 nm and large particles with an average particle size of 350 to 600 nm. When mixing small and large particles, it is preferable to keep the mass content of the small particles greater than the mass content of the large particles relative to the total solid content of the coated layer.

[0097] The average particle size was measured by observing the particles in the cross-section of the processed film using a transmission electron microscope or scanning electron microscope. 100 non-aggregated particles were observed, and the average value of these 100 particles was used as the average particle size.

[0098] The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles or irregularly shaped non-spherical particles can be used. The diameter of irregularly shaped particles can be calculated as the equivalent diameter of a circle. The equivalent diameter of a circle is obtained by dividing the area of ​​the observed particle by π, calculating the square root, and multiplying by 2.

[0099] The ratio of particles to the total solid content of the slip-free coating layer is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. A ratio of particles to the total solid content of the slip-free coating layer of 50% by mass or less is preferable because transparency is maintained and particle shedding from the slip-free coating layer does not occur significantly.

[0100] The ratio of particles to the total solid content of the slippery coating layer is preferably 1% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2% by mass or more. A ratio of particles to the total solid content of the slippery coating layer of 1% by mass or more is preferable as it ensures slipperiness.

[0101] As a method for measuring the particle content in a slip-free coating layer, for example, if the slip-free coating layer contains organic resin components and inorganic particles, the following method can be used. First, the slip-free coating layer applied to the processed film is extracted from the processed film using a solvent and allowed to dry to remove it. Next, heat is applied to the obtained slip-free coating layer, and the organic components contained in the slip-free coating layer are burned off by heat, thereby obtaining only the inorganic components. By measuring the weight of the obtained inorganic components and the slip-free coating layer before burning and distillation, the mass % of particles contained in the slip-free coating layer can be determined. At this time, accurate measurement can be achieved by using a commercially available differential thermal and thermogravimetric simultaneous measurement device. Note that the ratio of the above particles to the total solid content of the slip-free coating layer refers to the ratio of the total amount of multiple types of particles if multiple types of particles are present.

[0102] (Additives in the lubrication coating layer) To impart other functionalities to the smooth coating layer, various additives may be included, to the extent that they do not impair the appearance of the coating. Examples of such additives include fluorescent dyes, fluorescent whitening agents, plasticizers, ultraviolet absorbers, pigment dispersants, antifoaming agents, defoaming agents, and preservatives.

[0103] The smooth coating layer may also contain surfactants to improve leveling during application and to defoam the coating solution. The surfactant can be cationic, anionic, or nonionic, but silicone-based, acetylene glycol-based, or fluorine-based surfactants are preferred. These surfactants should be included in the coating layer in an amount that does not cause abnormalities in the coating appearance due to excessive addition.

[0104] As for the coating method, both the so-called in-line coating method, in which the coating is applied simultaneously with the formation of the polyester substrate film, and the so-called off-line coating method, in which the coating is applied separately with a coater after the polyester substrate film has been formed, can be applied. However, the in-line coating method is more efficient and therefore preferable.

[0105] As a coating method, any known method can be used to apply the coating solution to the polyethylene terephthalate (PET) film. Examples include the reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, and curtain coating method. These methods can be used individually or in combination.

[0106] In the present invention, a method for providing a smooth coating layer on a polyester film is to apply a coating solution containing a solvent, particles, and resin to the polyester film and then dry it. As the solvent, examples include organic solvents such as toluene, water, or a mixture of water and a water-soluble organic solvent. Preferably, from the standpoint of environmental concerns, a so-called aqueous solvent, such as water alone or a mixture of water and a water-soluble organic solvent, is preferred.

[0107] The solid content concentration of the lubrication coating solution depends on the type of binder resin and solvent, but is preferably 0.5% by mass or more, and more preferably 1% by mass or more. The solid content concentration of the coating solution is preferably 35% by mass or less, and more preferably 20% by mass or less.

[0108] The drying temperature after coating also depends on the type of binder resin, the type of solvent, the presence or absence of a crosslinking agent, the solid content concentration, etc., but it is preferably 70°C or higher and preferably 250°C or lower.

[0109] (Manufacturing of polyester film) In the present invention, the polyester film that serves as the base film can be manufactured according to a general method for manufacturing polyester films. For example, one method involves melting polyester resin, extruding it into a sheet, stretching the unoriented polyester longitudinally using the speed difference of the rolls at a temperature above the glass transition temperature, then stretching it transversely using a tenter, and finally heat-treating it. Another method involves biaxial stretching simultaneously in both longitudinal and transverse directions within a tenter.

[0110] In the present invention, the polyester film used as the base film may be either a uniaxially oriented film or a biaxially oriented film, but a biaxially oriented film is preferred.

[0111] The polyester film substrate is preferably 5 μm or thicker, more preferably 10 μm or thicker, and even more preferably 15 μm or thicker. A thickness of 5 μm or thicker is preferable because it reduces the likelihood of wrinkles forming during film transport.

[0112] The thickness of the polyester film substrate is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less. A thickness of 40 μm or less is preferable because it reduces the cost per unit area.

[0113] In the case of inline coating, the coating may be applied to the unstretched film before longitudinal stretching, or to the uniaxially oriented film after longitudinal stretching but before transverse stretching. When coating before longitudinal stretching, it is preferable to provide a drying step before roll stretching. When coating to the uniaxially oriented film before transverse stretching, the drying step can be combined with the film heating step in the tenter, so it is not always necessary to provide a separate drying step. The same applies to simultaneous biaxial stretching.

[0114] The thickness of the smooth coating layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, even more preferably 0.02 μm or more, and particularly preferably 0.03 μm or more. A thickness of 0.001 μm or more of the coating layer is preferable because it maintains the film-forming properties of the coating film and allows for the acquisition of a uniform coating film.

[0115] The thickness of the smooth coating layer 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 coating layer thickness of 2 μm or less is preferable because it eliminates the risk of blocking.

[0116] (Release layer) The release layer is laminated on top of the antistatic layer, which is applied to one side of the substrate. The resin constituting the release layer in the present invention is not particularly limited, and silicone resins, fluororesins, alkyd resins, various waxes, aliphatic olefins, etc., can be used, and each resin can be used alone or in combination of two or more types.

[0117] In the present invention, the release layer can be, for example, a silicone resin, which is a resin having a silicone structure in its molecule. Examples include curable silicone, silicone graft resin, and modified silicone resin such as alkyl-modified silicone resin. However, from the viewpoint of migration properties, it is preferable to use a reactive curable silicone resin. Reactive curable silicone resins can include those that are addition reaction type, condensation reaction type, or ultraviolet or electron beam curable type. More preferably, low-temperature curable addition reaction type resins that can be processed at low temperatures, and ultraviolet or electron beam curable type resins are preferred. By using these, the polyester film can be coated at low temperatures. Therefore, there is less thermal damage to the polyester film during processing, a polyester film with high flatness can be obtained, and defects such as pinholes can be reduced even when manufacturing ultrathin ceramic green sheets with a thickness of 0.2 to 2.0 μm.

[0118] Examples of silicone resins used in addition reactions include those obtained by reacting polydimethylsiloxane, which has vinyl groups introduced to its terminals or side chains, with hydrodienesiloxane using a platinum catalyst and curing the reaction. In this case, it is preferable to use a resin that can be cured at 120°C in 30 seconds or less, as this allows for processing at lower temperatures. Examples include low-temperature addition-curing types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV-curing types (LTC851, BY24-510, BY24-561, BY24-562, etc.) from Toray Dow Corning, as well as solvent addition + UV-curing types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual-cure curing types (X62-2835, X62-2834, X62-1980, etc.) from Shin-Etsu Chemical Co., Ltd.

[0119] Examples of silicone resins used in condensation reactions include those in which polydimethylsiloxane with OH groups at the ends and polydimethylsiloxane with H groups at the ends are condensed using an organotin catalyst to create a three-dimensional crosslinked structure.

[0120] Examples of UV-curable silicone resins include, as the most basic type, those that utilize the same radical reaction as conventional silicone rubber crosslinking, those that introduce unsaturated groups for photocuring, those that decompose onium salts with UV light to generate strong acids which then cleave epoxy groups and cause crosslinking, and those that crosslink through the addition reaction of thiols to vinylsiloxane. In addition, electron beams can be used instead of UV light. Electron beams have more energy than UV light, and it is possible to carry out a radical crosslinking reaction without using an initiator as in the case of UV curing. Examples of resins used include UV-curing silicones from Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, ​​X62-7629, X62-7660, etc.), UV-curing silicones from Momentive Performance Materials Inc. (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curing silicones from Arakawa Chemical Corporation (Silicolise UV POLY200, POLY215, POLY201, KF-UV265AM, etc.).

[0121] As the UV-curing silicone resins mentioned above, acrylate-modified or glycidoxy-modified polydimethylsiloxanes can also be used. Good mold release properties can also be obtained by mixing these modified polydimethylsiloxanes with polyfunctional acrylate resins or epoxy resins and using them in the presence of an initiator.

[0122] Other suitable resins include alkyd resins and acrylic resins that have been modified by stearyl or lauryl, or alkyd resins and acrylic resins obtained by the reaction of methylated melamine.

[0123] Examples of aminoalkyd resins obtained by the above-mentioned reaction of methylated melamine include Tesfine 303, Tesfine 305, and Tesfine 314, manufactured by Hitachi Chemical Co., Ltd. Examples of aminoacrylic resins obtained by the above-mentioned reaction of methylated melamine include Tesfine 322, manufactured by Hitachi Chemical Co., Ltd.

[0124] When using the above-mentioned resin for the release layer in the present invention, one type may be used, or two or more types may be mixed and used. In addition, it is possible to mix in additives such as light release additives and heavy release additives to adjust the release force.

[0125] The release coating layer in the present invention may contain particles with a particle size of 1 μm or less, but from the viewpoint of pinhole generation, it is preferable to substantially omit any particles or other materials that form protrusions.

[0126] The release layer in this invention may contain additives such as adhesion enhancers and antistatic agents. Furthermore, to improve adhesion to the substrate, it is preferable to pre-treat the polyester film surface with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0127] In the present invention, the thickness of the release layer can be set according to its intended use and is not particularly limited, but preferably, the thickness of the cured release coating layer is in the range of 0.005 to 2.0 μm. A thickness of 0.005 μm or more of the release coating layer is preferable because it maintains release performance. Furthermore, a thickness of 2.0 μm or less of the release coating layer is preferable because the curing time does not become too long, and there is no risk of uneven thickness in the ceramic green sheet due to a decrease in the flatness of the release film. In addition, because the curing time does not become too long, there is no risk of the resin constituting the release coating layer agglomerating and forming protrusions, so it is preferable that pinhole defects in the ceramic green sheet do not occur easily.

[0128] When a release layer is laminated on the antistatic layer of the present invention, the surface resistivity of the release layer surface is 12 [logΩ / □] or less. More preferably, it is 11 [logΩ / □] or less, and even more preferably, 10 [logΩ / □] or less. By making the surface resistivity 12 [logΩ / □] or less, static charge on the film can be suppressed, and foreign matter adhesion during the process can be prevented. Furthermore, by making it even smaller, such as 11 [logΩ / □] or less, or 10 [logΩ / □] or less, product defects due to static charge during the manufacturing of ceramic green sheets can be reduced, which is preferable.

[0129] Furthermore, while there is no specific lower limit for the surface resistivity of the antistatic film, it is preferable that it be 5.0 [logΩ / □] or higher. A surface resistivity of 5.0 [logΩ / □] or higher is preferable because it may prevent short circuits in the ceramic green sheet when the antistatic agent is transferred to the ceramic green sheet. In one embodiment, the surface resistivity of the antistatic film is 5.2 [logΩ / □] or higher, and may be, for example, 5.5 [logΩ / □] or higher.

[0130] The outer surface of the film on which the release layer is formed (the surface of the release coating on the entire coated film that is not in contact with the polyester film) needs to be reasonably flat in order to prevent defects from occurring in the ceramic green sheet that is coated and molded on it. The average surface roughness (Sa) of the region of the release layer on the side opposite to the substrate is 0.1 nm to 5 nm, for example, 0.2 nm to 4.5 nm. The maximum protrusion height (P) is preferably 1 nm to 100 nm, for example, 1 nm to 50 nm. If the surface roughness of the region is 5 nm or less, or the maximum protrusion height is 100 nm or less, then during sheet formation, defects such as pinholes do not occur, resulting in a good yield, which is preferable.

[0131] The ceramic green sheet, which is coated and molded onto the release layer, is wound into a roll together with the release film after coating and molding. At this time, the smooth surface of the release film, which is located on the opposite side of the release layer, is in contact with the surface of the ceramic green sheet during winding. In order to prevent defects from occurring on the surface of the ceramic green sheet, the outer surface of the smooth surface located on the opposite side of the release layer of the release film must be reasonably flat, and the average surface roughness (Sa) of the region should be between 1 nm and 30 nm, for example, between 2 nm and 25 nm. It is preferable that the maximum protrusion height (P) is between 60 nm and 500 nm.

[0132] If the average surface roughness (Sa) of the outer surface of the smooth surface is 1 nm or more and the maximum protrusion height (P) is 60 nm or more, it is preferable because the smooth surface does not become too smooth and an appropriate level of slipperiness is maintained. If the average surface roughness (Sa) of the outer surface is 30 nm or less and the maximum protrusion height (P) is 500 nm or less, it is preferable because the smooth surface does not become too rough and defects in the ceramic green sheet do not occur due to protrusions.

[0133] In the present invention, the method for forming the release layer is not particularly limited. A coating solution containing a dissolved or dispersed release resin is applied to one side of a polyester film substrate, and after removing the solvent by drying, the material is heated, heat-cured, or ultraviolet-cured. In this case, the drying temperature during solvent drying or heat curing is preferably 180°C or lower, more preferably 150°C or lower, and most preferably 120°C or lower. The heating time is preferably 30 seconds or less, and more preferably 20 seconds or less. When the temperature is 180°C or lower, the flatness of the film is maintained, and there is little risk of causing uneven thickness in the ceramic green sheet, which is preferable. When the temperature is 120°C or lower, the film can be processed without impairing its flatness, and the risk of causing uneven thickness in the ceramic green sheet is further reduced, which is particularly preferable.

[0134] In the present invention, the surface tension of the coating liquid when applying the composition that forms the release layer is not particularly limited, but is preferably 30 mN / m or less. By setting the surface tension as described above, the wettability after coating is improved, and the unevenness of the coating film surface after drying can be reduced.

[0135] In the present invention, the coating liquid used when applying the composition that forms the release layer is not particularly limited, but it is preferable to add a solvent with a boiling point of 90°C or higher. Adding a solvent with a boiling point of 90°C or higher prevents bumping during drying, levels the coating film, and improves the smoothness of the coating film surface after drying. The amount of the solvent added is preferably about 10 to 80% by mass of the total coating liquid.

[0136] Any known coating method can be applied to the composition that forms the above-mentioned release layer. For example, conventionally known methods such as roll coating methods including gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0137] (Ceramic green sheet and ceramic capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, first internal electrodes and second internal electrodes are alternately arranged along the thickness direction. The first internal electrodes are exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrodes are electrically connected to the first external electrode at the first end face. The second internal electrodes are exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrodes are electrically connected to the second external electrode at the second end face.

[0138] The release film for manufacturing ceramic green sheets of the present invention is used to manufacture such multilayer ceramic capacitors. For example, it is manufactured as follows: First, the release film of the present invention is used as a carrier film, and a ceramic slurry for forming a ceramic body is applied and dried. A conductive layer for forming a first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately laminating the ceramic green sheet, the ceramic green sheet with the conductive layer for forming the first internal electrode printed on it, and the ceramic green sheet with the conductive layer for forming the second internal electrode printed on it, and pressing them. The mother laminate is divided into multiple parts to produce raw ceramic bodies. Ceramic bodies are obtained by firing the raw ceramic bodies. After that, a multilayer ceramic capacitor can be completed by forming the first and second external electrodes. [Examples]

[0139] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. Furthermore, the evaluation methods used in the present invention are as follows.

[0140] [NMR measurement] The ratio of copolymer components introduced into the acrylic polyol is determined by nuclear magnetic resonance spectroscopy ( 1 HN MR, 13 The NMR spectrum was confirmed using a Varian Unity 400 (Agilent). The measurement was performed by removing the solvent from the synthesized acrylic polyol using a vacuum dryer, and then dissolving the dry material in deuterated chloroform. From the obtained NMR spectrum, the chemical shift δ (ppm) peaks assigned to each group were identified. The integrated intensity of each obtained peak was determined, and the composition ratio (mol%) of the copolymer components introduced into the acrylic polyol was confirmed from the number of hydrogen atoms at each group and the integrated intensity.

[0141] [Checking Tg] The Tg of the acrylic polyol was determined from the composition ratio of the copolymer components obtained by the above NMR measurement and from the Fox formula described above.

[0142] (1) Surface properties of the film The values ​​were measured using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. The average surface roughness (Sa) and average length of roughness curve elements (RSm) were taken as the average of 5 measurements, and the maximum protrusion height (P) was taken as the maximum value of 5 measurements. (Measurement conditions) • Measurement mode: WAVE mode • Objective lens: 50x 0.5x Tube Lens ·Measurement area 187×139μm (Sa,P measurement)

[0143] (4) Evaluation of the abrasion resistance of the antistatic layer A release film for green sheet manufacturing (3cm (film width direction) x 20cm (film length direction)) was mounted on a friction fastness tester (Daiei Kagaku Seiki Seisakusho, RT-200) with the antistatic layer facing upwards. An aluminum foil (thickness 80μm, arithmetic mean surface roughness 0.03μm) was used at the contact point between the load head (2cm x 2cm, 200g) and the sample film, and the test was performed 10 times back and forth over a distance of 10cm at a speed of 2 seconds per back and forth. The resulting film was placed on a black cardboard base and visually checked for powder falloff. ◎ and ○ were judged to be passable. ◎: No wear particles from the antistatic layer can be observed on the black background. ○: A small amount of wear dust from the antistatic layer can be seen on a portion of the black cardboard background. ×: Wear particles from the antistatic layer can be seen throughout the black background.

[0144] (5) Measurement of surface resistivity of the antistatic layer surface The surface resistivity of the antistatic layer surface in the antistatic film of the present invention was measured using a surface resistance meter (SIMCO Japan Co., Ltd., Work Surface Tester ST-3) after 24 hours of humidity control under conditions of 23°C and 55% humidity, and evaluated according to the following criteria. ◎ and ○ were judged to be acceptable. Furthermore, the surface resistivity of the antistatic layer surface of the present invention was measured with the antistatic layer formed on the substrate. ◎: Surface resistivity between 5 and 10 [logΩ / □] ○: Surface resistivity greater than 10 and less than or equal to 11 [logΩ / □] ×: Surface resistivity greater than 11 [logΩ / □] or greater

[0145] (5) Measurement of surface resistivity of the release layer surface The surface resistivity of the release layer surface in the antistatic film of the present invention was measured using a surface resistance meter (Simco Japan Co., Ltd., Work Surface Tester ST-3) after 24 hours of humidity control under conditions of 23°C and 55%, and evaluated according to the following criteria. ◎ and ○ were judged to be acceptable. Furthermore, the surface resistivity of the release layer surface of the present invention was measured after forming an antistatic layer on the substrate and then forming the release layer. ◎: Surface resistivity is between 5 and 11 [logΩ / □] ○: Surface resistivity greater than 11 and less than or equal to 12 [logΩ / □] ×: Surface resistivity greater than 12 [logΩ / □] or greater

[0146] (5) Solvent resistance evaluation The surface of the antistatic layer was wiped 10 times back and forth using a Kimwipe impregnated with a solvent (methyl ethyl ketone). The change in appearance after the above treatment was evaluated according to the following criteria. ◎ and ○ were judged to be acceptable. ◎: No whitening ○: Slight whitening present on the wiping surface. ×: Whitening present across the entire surface to be wiped.

[0147] (7) Measurement of peeling force of ceramic green sheet Next, the release surface of the obtained release film sample was coated with a slurry using an applicator so that the dried slurry had a thickness of 2.0 μm, and dried at 60°C for 1 minute to form a ceramic green sheet on the release film. The obtained release film with the ceramic green sheet attached was destaticized using a static eliminator (Keyence Corporation, SJ-F020), and then peeled using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3, load cell load 0.1N) at a peel angle of 90 degrees, peel temperature of 25°C, and peel speed of 10 m / min. For peeling, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to a SUS plate attached to the peel tester, and the release film was fixed on top of it with the release film side adhering to the double-sided tape, and the ceramic green sheet side was peeled off by pulling. From the obtained measured values, the average value of the peel force for peel distances of 20 mm to 70 mm was calculated, and this value was defined as the peel force. Measurements were taken a total of five times, and the average value of the peeling force was used for evaluation. The peeling force values ​​obtained were judged according to the following criteria. ◎, ○, and △ were judged as passing. ◎: 0.4mN / mm or more, 0.6mN / mm or less ○: Greater than 0.6 mN / mm and 0.8 mN / mm or less △: Greater than 0.8 mN / mm and less than or equal to 1.0 mN / mm ×: Less than 0.4 mN / mm or greater than 1.0 mN / mm, or the ceramic green sheet ruptured during measurement.

[0148] (8) Evaluation of pinholes and thickness variations in ceramic green sheets The antistatic release films obtained in each example and comparative example were wound into rolls with a width of 400 mm and a length of 5000 m to obtain antistatic release films. These antistatic release film rolls were stored for 30 days in an environment of 40°C and humidity of 50% or less, and the antistatic films were then used for evaluation. Slurry composition I, consisting of the materials listed below, was stirred and mixed for 10 minutes, and then dispersed using a bead mill with 0.5 mm diameter zirconia beads for 10 minutes to obtain a primary dispersion. Subsequently, slurry composition II, consisting of the materials listed below, was added to the primary dispersion in a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0, and secondary dispersion was performed using a bead mill with 0.5 mm diameter zirconia beads for 10 minutes to obtain a ceramic slurry. (Slurry composition I) Toluene 22.3 parts by mass Ethanol 18.3 parts by mass Barium titanate (average particle size 100 nm) 57.5 parts by mass Homogenol L-18 (manufactured by Kao Corporation) 1.9 parts by mass (Slurry Composition II) Toluene 39.6 parts by mass Ethanol 39.6 parts by mass Dioctyl phthalate 3.3 parts by mass Polyvinyl butyral (Sekisui Chemical Co., Ltd., Esrec BM-S) 16.3 parts by mass 1-Ethyl-3-methylimidazolium ethyl sulfate 0.5 parts by mass Apply the slurry to the release surface of the antistatic release film sample using an applicator so that the dried slurry is 0.5 μm thick. Dry at 90°C for 1 minute, then overlap the slurry surface and the smoothed coating surface and apply at 1 kg / cm² for 10 minutes. 2 After applying the load, 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, 25 cm 2 Within the specified range, light was shone from the opposite side of the coated surface of the ceramic slurry, and the occurrence of pinholes visible through the transmitted light was observed and visually judged according to the following criteria. ◎, ○, and △ were judged to be acceptable. ◎: No pinholes, and the thickness variation is particularly good. ○: No pinholes, no particular issues with thickness variation. △: There are a very small number of pinholes and some variation in thickness is visible. ×: There are some pinholes, and the thickness variation is somewhat noticeable.

[0149] (Preparation of polyethylene terephthalate pellets (PET(I))) A continuous esterification reactor consisting of a three-stage complete mixing tank equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet was used as the esterification reactor. Terephthalic acid (TPA) was supplied at a rate of 2 tons / hour, ethylene glycol (EG) at a ratio of 2 moles per mole of TPA, and antimony trioxide was added in an amount that resulted in 160 ppm of Sb atoms relative to the produced PET. This slurry was continuously supplied to the first esterification reactor of the esterification reactor and reacted at atmospheric pressure at 255°C for an average residence time of 4 hours. Next, the reaction products from the first esterification reactor were continuously removed from the system and supplied to the second esterification reactor. EG distilled off from the first esterification reactor was supplied to the second esterification reactor at 8% by mass relative to the generated PET. Furthermore, an EG solution containing magnesium acetate tetrahydrate in an amount that resulted in 65 ppm of Mg atoms relative to the generated PET, and an EG solution containing TMPA (trimethyl phosphate) in an amount that resulted in 40 ppm of P atoms relative to the generated PET were added, and the reaction was carried out at atmospheric pressure at 260°C for an average residence time of 1 hour. Next, the reaction products from the second esterification reactor were continuously removed from the system and supplied to the third esterification reactor, and the mixture was dispersed at 39 MPa (400 kg / cm²) using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.). 2 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm, which was dispersed by a dispersion treatment with an average of 5 passes at a pressure of ) and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm, which had 1% by mass of polyacrylic acid ammonium salt attached to calcium carbonate, were added as 10% EG slurry each and reacted at atmospheric pressure at 260°C with an average residence time of 0.5 hours. The esterification reaction product generated in the third esterification reaction vessel was continuously supplied to a three-stage continuous polycondensation reaction apparatus to perform polycondensation, and after filtration with a filter made of sintered stainless steel fibers with a 95% cut diameter of 20 μm, it was extruded into water by ultrafiltration, cooled and cut into chips to obtain PET chips with an intrinsic viscosity of 0.60 dl / g (hereinafter abbreviated as PET(I)). The lubricant content in the PET chips was 0.6% by mass.

[0150] (Preparation of polyethylene terephthalate pellets (PET(II))) On the other hand, in the production of the above-mentioned PET chip, a PET chip with an intrinsic viscosity of 0.62 dl / g that does not contain any particles such as calcium carbonate or silica was obtained (hereinafter abbreviated as PET(II)).

[0151] (Manufacturing of laminated film Y) After drying these PET chips, they were melted at 285°C and then melted again at 290°C in a separate extruder. A two-stage filtration process was performed using a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. The mixture was then combined in a feed block, and PET(I) was laminated as the anti-release side layer and PET(II) as the release side layer. The resulting sheet was extruded (casted) at a speed of 45 m / min and electrostatically adhered and cooled on a casting drum at 30°C using the electrostatic adhesion method to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted so that anti-release side layer / release side layer = 60% / 40% based on the discharge rate calculations of each extruder. Next, this unstretched sheet was heated with an infrared heater and then stretched 3.5 times in the longitudinal direction by the speed difference between the rolls at a roll temperature of 80°C. Subsequently, the material was guided into a tenter and stretched 4.2 times laterally at 140°C. Next, it was heat-treated at 210°C in a heat-fixing zone. After that, a 2.3% relaxation treatment was performed laterally at 170°C to obtain a biaxially oriented polyethylene terephthalate film Y with a thickness of 31 μm. The Sa of the obtained film Y was 2 nm on the release side layer and 26 nm on the non-release side layer.

[0152] (Antistatic agent A) A mixture of alkoxysilane hydrolyzed polycondensate and polystyrene sulfonic acid (manufactured by Colcoat, trade name Colcoat PS-169, solid content concentration 3.50%).

[0153] (Melamine compound B-1) Melamine compound (manufactured by Nippon Carbide Co., Ltd., MW-30M, melamine resin, full ether type, solid content concentration 100% by mass) (Melamine compound B-2) Melamine compound (manufactured by Nippon Carbide Co., Ltd., MW-22, melamine resin, full ether type, solids content 70% by mass) (Melamine compound B-3) Melamine compound (manufactured by Nippon Carbide Co., Ltd., MX-730, melamine resin, iminotype, solid content concentration 80% by mass) (Melamine compound B-4) Melamine compound (manufactured by Nippon Carbide Co., Ltd., MX-042, melamine resin, iminomethylol type, solid content concentration 70% by mass)

[0154] (Silane coupling agent C-1) 3-Glycidoxypropyltrimethoxysilane, solid content concentration 100% by mass (Silane coupling agent C-2) Vinyltriacetoxysilane, solid content concentration 100% by mass

[0155] (Acid catalyst D-1) Paratoluenesulfonic acid, manufactured by Hitachi Chemical Polymer Co., Ltd., Dryer #900

[0156] (Manufacturing of Acrylic Polyol E) A four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet was charged with 231 parts by mass of methyl methacrylate (MMA), 130 parts by mass of stearyl methacrylate (SMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 33 parts by mass of methacrylic acid (MAA), and 1153 parts by mass of isopropyl alcohol (IPA). The flask was heated to 80°C while stirring. The flask was stirred for 3 hours while maintaining the temperature at 80°C, after which 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. The flask was then heated to 120°C while purging with nitrogen, and the mixture was stirred at 120°C for 2 hours. Next, the mixture was subjected to a reduced pressure of 1.5 kPa at 120°C to remove unreacted raw materials and solvent, yielding an acrylic polyol. The flask was returned to atmospheric pressure and cooled to room temperature, and 1976 parts by mass of an IPA aqueous solution (water content 50% by mass) was added and mixed. Then, while stirring, ammonia was added using a dropping funnel, and the acrylic polyol was neutralized until the pH of the solution was in the range of 5.5 to 7.5, yielding acrylic polyol E with a solid content of 20% by mass. The Tg of acrylic polyol E was 88°C, the acid value was 87 mg KOH / g, and the hydroxyl value was 100 mg KOH / g.

[0157] (Manufacturing of oxazoline-based crosslinking agent F) In a flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer, 460.6 parts of isopropyl alcohol were charged and heated to 80°C while slowly flowing nitrogen gas. A pre-prepared monomer mixture consisting of 126 parts methyl methacrylate, 210 parts 2-isopropenyl-2-oxazoline, and 84 parts methoxypolyethylene glycol acrylate, and an initiator solution consisting of 21 parts 2,2'-azobis(2-methylbutyronitrile) (manufactured by Nippon Hydrazine Industries Co., Ltd., "ABN-E") and 189 parts isopropyl alcohol were added dropwise from a dropping funnel over 2 hours to allow the reactions to occur, and the reaction was continued for 5 hours after the dropwise addition was complete. Nitrogen gas was continuously flowed during the reaction to maintain the temperature inside the flask at 80±1°C. After that, the reaction solution was cooled to obtain a resin (F) having oxazoline groups with a solid content of 25%. The amount of oxazoline groups in the obtained resin (F) containing oxazoline groups was 4.3 mmol / g, and the number-average molecular weight measured by GPC (gel permeation chromatography) was 20,000.

[0158] (Acrylic Particles G-1) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX100W, average particle size 150 nm, solid content concentration 10% by mass) (Acrylic Particles G-2) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX300W, average particle size 450 nm, solid content concentration 10% by mass)

[0159] (Preparation of lubrication coating solution) A lubricating coating solution with the following composition was prepared. (Smooth coating liquid) Water 39.62 parts by mass Isopropyl alcohol 35.00 parts by mass Acrylic polyol resin E (solid content concentration 20% by mass) 16.57 parts by mass Oxazoline-based crosslinking agent F (solid content concentration 25% by mass) 5.68 parts by mass Acrylic particles G-1: 2.37 parts by mass (Average particle size 150nm, solid content concentration 10% by mass) Acrylic particles G-2: 0.47 parts by mass (Average particle size 450nm, solid content concentration 10% by mass) Surfactant H (silicone-based, solid content concentration 10% by mass) 0.30 parts by mass

[0160] (Release agent solution) A mold release agent solution with a solid content of 2% by mass was prepared by diluting 100 parts by mass of heat- and UV-curing silicone resin (LTC851, manufactured by Toray Dow Corning) and 2 parts by mass of platinum catalyst (SRX212, manufactured by Toray Dow Corning) as a curing catalyst with a toluene / methyl ethyl ketone / heptane (=7:7:6) solution.

[0161] (Example 1)

[0162] (Manufacturing of laminated film Z) As a film raw material polymer, PET resin pellets (PET(II)) with an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60 / 40) of 0.62 dl / g and substantially free of particles were dried at 135°C for 6 hours under reduced pressure of 133 Pa. The pellets were then fed into an extruder and melt-extruded into a sheet at approximately 280°C. The sheet was then rapidly cooled and solidified on a rotating, cooled metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

[0163] This unstretched PET sheet was heated to 100°C using a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a roll group with different peripheral speeds to obtain a uniaxially oriented PET film.

[0164] Next, the slip-free coating solution was applied to one side of the PET film using a bar coater and dried at 80°C for 15 seconds. The coating amount after final stretching and drying was adjusted to 0.1 μm. Subsequently, the film was stretched 4.0 times in the width direction at 150°C using a tenter, and with the length in the width direction of the film fixed, it was heated at 230°C for 0.5 seconds, and then subjected to a 3% widthwise relaxation treatment at 230°C for 10 seconds to obtain a polyester film Z with a slip-free coating layer and a thickness of 31 μm. The Sa of the release side layer of the obtained film Z was 0.3 nm, and the Sa of the non-release side layer was 6 nm.

[0165] (Formation of an antistatic layer) The following antistatic layer-forming composition 1 was applied to the side of the release film opposite to the side where the slip-free coating layer was formed, using a reverse gravure coater, to a dry thickness of 0.065 μm. Then, it was dried and cured with hot air at 140°C for 30 seconds to obtain a polyester film with an antistatic layer. (Composition for forming an antistatic layer 1) Isopropyl alcohol 74.062 parts by mass Antistatic agent A-1 (manufactured by Colcoat Co., Ltd., Colcoat PS-169, solid content concentration 3.50%) 25.714 parts by mass Melamine compound B-1 (manufactured by Nippon Carbide Co., Ltd., MW-30M, melamine resin, full ether type, solid content concentration 100% by mass) 0.100 parts by mass Silane coupling agent C-1 (3-glycidoxypropyltrimethoxysilane, solid content concentration 100% by mass) 0.060 parts by mass Silane coupling agent C-2 (vinyltriacetoxysilane, solid content concentration 100% by mass) 0.060 parts by mass Acid catalyst D-1 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Polymer Co., Ltd., dryer #900) 0.004 parts by mass

[0166] (Formation of release coating layer) A release agent solution was applied to the surface of a polyester film with an antistatic layer using a reverse gravure coater to a thickness of 0.01 μm after drying. Then, it was dried with hot air at 120°C for 30 seconds, and immediately afterward, ultraviolet irradiation (300 mJ / cm2) was performed using an electrodeless lamp (H-bulb manufactured by Heraeus Corporation) to form a release coating layer, thereby obtaining a release film with an antistatic layer.

[0167] (Examples 2-20, Comparative Examples 1-3) A release film with an antistatic layer was obtained using the same procedure as in Example 1, except that the base material, composition number, solid content ratio of each component, and coating thickness were changed to those shown in Table 1.

[0168] Tables 1 and 2 show the composition and evaluation results for each example and comparative example.

[0169] [Table 1]

[0170] [Table 2]

[0171] Table 1 above shows the solid content ratios of the antistatic agent, melamine compound, silane coupling agent, and acid catalyst in the antistatic layer forming composition. These ratios represent the mass ratio of each solid content when the total solid content of the antistatic agent, melamine compound, silane coupling agent, and acid catalyst is set to 100% by mass.

[0172] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0173] The objective of the present invention is to provide a release film that has good peelability, high smoothness, and antistatic properties. In Examples 1 to 20, an antistatic layer that suppresses detachment during the processing step is applied, making it possible to produce high-quality ceramic capacitors without reducing the yield of ceramic capacitors. Thus, the release film of the present invention can suppress the aggregation of components contained in the antistatic layer, thereby preventing the antistatic layer from falling off during release layer processing. Furthermore, it can maintain the smoothness of the antistatic layer. Therefore, deterioration of the smoothness of the release layer surface can be suppressed, and inhibition of the release layer's hardening caused by the antistatic layer can also be suppressed. In addition, since the release film of the present invention can suppress the detachment of the antistatic layer that occurs during ceramic green sheet molding, the generation of foreign matter caused by the components of the release film can be suppressed. Furthermore, when product transport time is long, the film is often stored in a rolled state for extended periods, and stress is expected to be applied to the film. The present invention can suppress the detachment of the antistatic layer caused by stress that may occur not only during roll winding and unwinding, but also during long-term storage in a rolled state. On the other hand, in Comparative Examples 1 and 2, the melamine compound and silane coupling agent fall below the scope of the present invention, resulting in poor adhesion to the substrate, poor powder shedding, and poor solvent resistance. Therefore, there are concerns about reduced yield due to the adhesion of foreign matter originating from the antistatic layer. Due to the poor powder shedding and solvent resistance, it is thought that this affects the release layer during processing, leading to deterioration of surface roughness and poor evaluation of ceramic peeling. Furthermore, in Comparative Example 3, the ratio of the melamine compound exceeded the range of the present invention, which is thought to have reduced the antistatic performance, making it easier for environmental foreign matter to adhere during the manufacturing process of the ceramic capacitor, and resulting in the occurrence of pinholes. [Industrial applicability]

[0174] According to the present invention, it is possible to provide a release film with good peelability, high smoothness, and antistatic properties. Furthermore, by using the release film for manufacturing ceramic green sheets of the present invention, an ultrathin ceramic green sheet can be obtained, and minute ceramic capacitors can be manufactured efficiently.

Claims

1. A release film having a polyester substrate, an antistatic layer on one surface of the substrate, and a release layer in that order, The antistatic layer is formed by curing an antistatic layer forming composition. The antistatic layer forming composition comprises an antistatic agent (A), a melamine compound (B), a silane coupling agent (C), and an acid catalyst (D). The antistatic agent (A) comprises an alkoxysilane hydrolysis polycondensate (A-1) and a polystyrene sulfonic acid compound (A-2). The aforementioned alkoxysilane hydrolysis polycondensate (A-1) is obtained by hydrolyzing a mixture of tetraalkoxysilane and / or its oligomer and phenylalkoxysilane and / or its oligomer, and then by a polycondensation reaction, and has a siloxane bond (Si-O-Si) as its backbone. The content of the melamine compound (B) in the total solid content of the antistatic layer forming composition is 2.0% by mass or more and 20% by mass or less. The surface resistivity (logΩ / □) of the antistatic layer is 5 or more and 12 or less. A release film wherein the surface resistivity (logΩ / □) of the release layer on the side opposite to the antistatic layer is 5 or more and 12 or less.

2. In the antistatic layer, the average surface roughness (Sa) of the region on the side opposite to the substrate is 0.1 nm or more and 5 nm or less, and the maximum protrusion height (P) is 1 nm or more and 100 nm or less. In the aforementioned release layer, the average surface roughness (Sa) of the region on the side opposite to the antistatic layer is 0.1 nm or more and 5 nm or less, and the maximum protrusion height (P) is 1 nm or more and 100 nm or less. The release film according to claim 1.

3. The release film according to claim 1, wherein the content of the antistatic agent (A) is 60% by mass or more and 99% by mass or less of the total solid content of the antistatic layer forming composition.

4. The release film according to claim 1, wherein the content of the silane coupling agent (C) is 2.5% by mass or more and 30% by mass or less of the total solid content of the antistatic layer forming composition.

5. The release film according to claim 1, wherein the surface layer on which the antistatic layer of the polyester substrate is laminated is a surface layer that substantially does not contain particles.

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