Release film for manufacturing ceramic green sheets

Abstract

To provide a release film for manufacturing an excellent ceramic green sheet, which makes it possible to achieve both prevention of pinholes and partial thickness variations and a reduction in unwinding electrification even if the ceramic green sheet is thinned.SOLUTION: A release film for manufacturing a ceramic green sheet includes a base material that is a polyester film containing substantially no inorganic particle. A release coating layer is disposed on one surface of the base material, and an easy-slip coating layer containing particles is disposed on another surface thereof. The easy-slip coating layer is obtained by curing a composition containing an acrylic resin and a melamine-based crosslinking agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film for manufacturing ceramic green sheets. More specifically, the present invention relates to a release film for manufacturing ceramic green sheets that can prevent pinholes and localized thickness variations, and reduce static electricity during unwinding, even when the ceramic green sheet is made into a thin film. [Background technology]

[0002] Conventionally, a technique has been disclosed to resolve problems such as the front and back sides of a ceramic green sheet manufacturing release film sticking together (blocking) when the film is stored in a rolled-up state, by making the surface roughness of the side opposite to the side of the base film where the release agent layer is provided relatively rough (see, for example, Patent Document 1). However, this conventional technique has the problem of causing pinholes and localized thickness variations due to the large protrusions.

[0003] Therefore, a technique has been disclosed that attempts to prevent the occurrence of pinholes and localized thickness variations in the ceramic green sheet by filling the protrusions on the back surface with a coating layer in order to reduce the height of the protrusions (see, for example, Patent Document 2). However, with this conventional technique, although the height of the protrusions is reduced, the density of the protrusions is low, so the pressure on the protrusions is large, and if the ceramic green sheet is made even thinner, there is a problem in that pinholes occur. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-203822 [Patent Document 2] Japanese Patent Publication No. 2014-144636 [Overview of the project] [Problems that the invention aims to solve]

[0005] This invention was made against the backdrop of the problems of the prior art. Specifically, the object of this invention is to provide an excellent release film for manufacturing ceramic green sheets that can prevent pinholes and localized thickness variations, and reduce static electricity during unwinding, even when the ceramic green sheet is made into a thin film. [Means for solving the problem]

[0006] The inventors diligently studied and conducted research to achieve the above objective, resulting in the completion of the present invention. Specifically, the present invention consists of the following configuration.

[0007] 1. A release film for manufacturing ceramic green sheets, comprising a polyester film substantially free of inorganic particles as a base material, a release coating layer on one surface of the base material, and a smooth coating layer containing particles on the other surface, wherein the smooth coating layer is formed by curing a composition containing acrylic resin and a melamine-based crosslinking agent.

[0008] 2. The release film for manufacturing ceramic green sheets according to the first claim, wherein the glass transition temperature of the acrylic resin is 50°C or higher and 110°C or lower.

[0009] 3. The release film for manufacturing ceramic green sheets according to the first or second above, wherein the hydroxyl value of the acrylic resin is 50 mg KOH / g or more and 450 mg KOH / g or less.

[0010] 4. A release film for manufacturing ceramic green sheets according to any one of the first to third claims above, wherein the average surface roughness (Sa) of the slippery coating layer is 1 nm or more and 25 nm or less, the maximum protrusion height (P) is 60 nm or more and 500 nm or less, and the average length of the roughness curve elements (RSm) is 10 μm or less.

[0011] 5. A release film for manufacturing ceramic green sheets according to any one of the first to fourth claims above, wherein the thickness of the slip-free coating layer is 0.001 μm or more and 2 μm or less.

[0012] 6. A method for manufacturing a ceramic green sheet using a release film for manufacturing ceramic green sheets as described in any of the above 1 to 5.

[0013] 7. The method for manufacturing a ceramic green sheet according to paragraph 6, wherein the thickness of the ceramic green sheet to be manufactured is 0.2 μm or more and 2.0 μm or less.

[0014] 8. A method for manufacturing a ceramic capacitor using the method for manufacturing a ceramic green sheet described in paragraph 6 or 7 above. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an excellent release film for manufacturing ceramic green sheets that can prevent pinholes and localized thickness variations, as well as reduce static electricity during unwinding, even when the ceramic green sheet is made into a thin film. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below.

[0017] The release film for manufacturing ceramic green sheets of the present invention (hereinafter sometimes simply referred to as "release film") is a release film having a release coating layer on one side of a biaxially oriented polyester film which is a base film, and a smooth coating layer containing particles on the other side.

[0018] To increase the density of protrusions on the smooth surface, a release film has been proposed that can accommodate the thinning of green sheets in recent years by keeping the average length (RSm) of the roughness curve elements of the smooth coated surface within a specific range (for example, International Publication No. 2017 / 017354). This technology is preferable because, by increasing the density of protrusions, it is possible to maintain a low protrusion height while providing good winding properties and preventing pinholes and localized thickness variations.

[0019] In the present invention, as the lubricious coating layer, a composition containing an acrylic resin and a melamine-based crosslinking agent is cured, so that the hardness of the lubricious coating layer becomes moderately high, and deformation of the lubricious coating layer when it is wound up after the release coating layer is applied is less likely to occur. Generally, it is known that the greater the contact area between two generally contacting objects, the greater the charge generation during peeling when the two objects are peeled. When the amount of deformation of the lubricious coating layer is small, the contact area between the lubricious coating layer and the release layer becomes small, so it is preferable because it can suppress the charge generation during unwinding when the release film roll is unwound. Less charge generation during unwinding is preferable because it can prevent quality abnormalities of ceramic capacitors due to adhesion of environmental foreign substances to the release surface. In the thinning of ceramic sheets, which is a trend in recent years, even adhesion of minute environmental foreign substances to the release surface, which was not a problem conventionally, becomes a problem. Therefore, the release film having the composition of the lubricious coating layer defined in the present invention is effective, and it is more preferable to keep the average length (RSm) of the roughness curve elements of the lubricious coating layer within a specific range.

[0020] (Base film) In the present invention, the film preferably used as the base material is a film composed of a polyester resin, and mainly, a polyester film containing at least one selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate is preferable. Further, it may be a film made of a polyester in which a third component monomer is copolymerized as a part of the dicarboxylic acid component or the diol component of the polyester as described above. Among these polyester films, a polyethylene terephthalate film is most preferable in view of the balance between physical properties and cost.

[0021] <X Further, the polyester film may be single-layer or multi-layer. Also, within the range in which the desired effects of the present invention are exhibited, various additives can be contained in the polyester resin in these respective layers as necessary. Examples of the additives include antioxidants, light-resistant agents, anti-gelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, and the like.

[0022] (Slip coat layer) The release film of the present invention has a slip coat layer on one surface of the base film made of polyester as described above. It is preferable that at least a binder resin and particles are contained in the slip coat layer.

[0023] (Binder resin in the slip coat layer) As the binder resin constituting the slip coat layer in the present invention, it is preferable to contain an acrylic resin. The acrylic resin is preferably an acrylic resin having a hydroxyl group and a carboxyl group in the molecule. It is more preferable that the constituent unit having a hydroxyl group is contained in an amount of 20 to 90 mol% in 100 mol% of all constituent units. When the constituent unit having a hydroxyl group is 20 mol% or more, it is preferable because the water solubility of the acrylic resin is appropriately maintained and a strong crosslinked structure with a melamine-based crosslinking agent is formed. On the other hand, when it is 90 mol% or less, it is preferable because the hydroxyl group of the acrylic resin does not cause an extreme interaction with the particles contained in the slip coat layer and the particles are uniformly dispersed.

[0024] To introduce a hydroxyl group into the acrylic resin, monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or ring-opening adducts of γ-butyrolactone or ε-caprolactone to 2-hydroxyethyl (meth) acrylate may be used as copolymerization components. Among them, 2-hydroxyethyl (meth) acrylate is preferable in that it does not inhibit water solubility. These may be used in combination of two or more. Needless to say, the acrylic resin referred to in the present invention includes methacrylic resin.

[0025] The hydroxyl value of the acrylic resin is preferably 50 mg KOH / g or more, more preferably 100 mg KOH / g or more, and even more preferably 150 mg KOH / g or more. A hydroxyl value of 50 mg KOH / g or more is preferable because it results in good water solubility of the acrylic resin and the formation of a strong crosslinked structure with the melamine-based crosslinking agent.

[0026] The hydroxyl value of the acrylic resin is preferably 450 mgKOH / g or less, more preferably 400 mgKOH / g or less, and even more preferably 350 mgKOH / g or less. A hydroxyl value of 450 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.

[0027] The acrylic resin used in this invention is preferably a resin having carboxyl groups in addition to hydroxyl groups. The presence of carboxyl groups makes it easy to 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.

[0028] 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 imparting of 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.

[0029] 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.

[0030] 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 facilitates the imparting of water solubility.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (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.

[0035] 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.

[0036] 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.

[0037]

number

[0038] W n : Mass fraction (mass%) of each monomer Tg n :Tg(K) of homopolymers of each monomer 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 hydroxyl groups or carboxyl groups, which are the crosslinking components, and thus does not result in a low crosslinking density. 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 thus does not result in a low crosslinking density.

[0045] (Crosslinking agent) In the present invention, it is preferable that the smooth coating layer contains a melamine-based crosslinking agent in order to form a crosslinked structure within the smooth coating layer. By including a melamine-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 hydroxyl groups and carboxyl groups of the acrylic resin, and as a result, static electricity when the release film roll is unwound can be suppressed. Other crosslinking agents may also be used in combination, and specific crosslinking agents that can be used in combination include urea-based, epoxy-based, oxazoline-based, carbodiimide-based, isocyanate-based, and silanol-based agents. Furthermore, catalysts and the like can be used as appropriate as needed to promote the crosslinking reaction.

[0046] Examples of melamine-based crosslinking agents include melamine, methylolated melamine derivatives obtained by condensing melamine with formaldehyde, compounds partially or completely etherified by reacting methylolated melamine with a lower alcohol, and mixtures thereof. Specifically, compounds having triazine and a methylol group are particularly preferred. In this invention, the melamine-based crosslinking agent refers to the component derived from the melamine-based crosslinking agent when the melamine-based crosslinking agent described below forms a crosslinked structure with the acrylic resin. The melamine-based crosslinking agent may be a monomer, a condensate consisting of two or more polymers, or a mixture thereof. Examples of lower alcohols used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The groups include imino groups, methylol groups, or alkoxymethyl groups such as methoxymethyl groups and butoxymethyl groups, which are present in one molecule. Examples include imino-type methylated melamine resins, methylol-type melamine resins, methylol-type methylated melamine resins, and fully alkyl-type methylated melamine resins. Among these, methylolated melamine resins are the most preferred. Furthermore, to promote the thermosetting of melamine compounds, an acidic catalyst such as p-toluenesulfonic acid may be used.

[0047] Using such a melamine-based crosslinking agent not only suppresses static electricity during unwinding by increasing the hardness of the coating film due to the self-condensation of the melamine-based crosslinking agent, but also allows for the reaction between the hydroxyl groups and carboxyl groups contained in the acrylic resin and the melamine-based crosslinking agent to proceed, resulting in a resin layer with even higher hardness. With a higher hardness coating film, deformation of the easily slippery coating layer during unwinding is reduced, and a film that further suppresses static electricity during unwinding can be obtained.

[0048] 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 hydroxyl groups and carboxyl groups of the acrylic resin to be crosslinked too much, and thus does not reduce the crosslinking density.

[0049] (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. Silica is particularly preferred for providing the coating layer with appropriate lubricity.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 strengthens the interaction between the binder and crosslinking agent components of the slippery coating layer, making it easier to prevent detachment, which is preferable. 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. These organic particles are preferably included as particles with a relatively large average particle size, where detachment from the slippery coating layer is likely to be a problem, for example, particles with an average particle size of 300 to 1000 nm are preferable. More preferably, particles with an average particle size of 350 to 600 nm are included. Of course, it is particularly preferable that the organic particles with the above average particle size are acrylic resin particles and / or methacrylic resin particles.

[0054] 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.

[0055] 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 particle 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] (Additives in the lubrication coating layer) In order 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] (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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] The ceramic green sheet, which is coated and molded onto the release coating layer described later, is wound into a roll together with the release film after coating and molding. At this time, the ceramic green sheet is wound up with the slip-free coating layer of the release film in contact with the surface of the ceramic green sheet. In order to prevent defects from occurring on the surface of the ceramic green sheet, the outer surface of the slip-free coating layer (the surface of the slip-free coating layer of the entire coating film that is not in contact with the polyester film) must be reasonably flat, and it is preferable that the average surface roughness (Sa) of the region is 1 nm or more and 25 nm or less, and the maximum protrusion height (P) is 60 nm or more and 500 nm or less.

[0074] If the average surface roughness (Sa) of the outer surface of the slip-free coating layer is 1 nm or more and the maximum protrusion height (P) is 60 nm or more, it is preferable because the slip-free coating 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 25 nm or less and the maximum protrusion height (P) is 500 nm or less, it is preferable because the slip-free coating surface does not become too rough and defects in the ceramic green sheet do not occur due to protrusions.

[0075] In this invention, in addition to setting the average surface roughness (Sa) and maximum protrusion height (P) within the above ranges, it is preferable that the average length of the roughness curve elements (RSm) is 10 μm or less. Controlling the average length of the roughness curve elements (RSm) to 10 μm or less increases the number of protrusions per unit area. When the number of protrusions increases, the pressure applied to each protrusion is dispersed and reduced, which is preferable as it effectively suppresses the occurrence of pinholes. The average length of the roughness curve elements (RSm) is more preferably 5 μm or less, and even more preferably 3 μm or less. However, if the average length of the roughness curve elements (RSm) is too small, it is related to the fact that the particle content in the smooth coating layer is too high, and is also related to the average surface roughness (Sa) and the maximum protrusion height (P) being large, so it is preferable that it be 0.1 μm or more, and it may also be 0.5 μm or more, or it may also be 1 μm or more.

[0076] In this invention, in order to set the average length (RSm) of the roughness curve elements within a predetermined range, it is preferable that the average particle size of the particles contained in the smooth coating layer be 1000 nm or less. More preferably, it is 800 nm or less, and even more preferably, 600 nm or less. When the particle size is 1000 nm or less, the distance between particles does not become too large, and the RSm is adjusted within the predetermined range, which is preferable. The surface free energy of the slip-free coating layer is 45 mJ / m 2 Preferably, it is 40 mJ / m 2 It is more preferable that the surface free energy of the slip-free coating layer is 45 mJ / m 2The following is preferable, as it makes it less likely for environmental foreign matter to adhere during the process, less likely for foreign matter to adhere to the release surface, and less likely for pinholes caused by environmental foreign matter to occur in the ceramic green sheet.

[0077] (Release coating layer) The resin constituting the release coating 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.

[0078] In the present invention, the release coating 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.

[0079] 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.

[0080] 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.

[0081] 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.).

[0082] 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.

[0083] 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.

[0084] 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.

[0085] When using the above-mentioned resin for the release coating 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.

[0086] 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.

[0087] The release coating layer in the present 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.

[0088] In the present invention, the thickness of the release coating layer can be set according to its intended use and is not particularly limited, but preferably, the thickness of the release coating layer after curing is in the range of 0.005 to 2.0 μm. A thickness of 0.005 μm or more is preferable because it maintains peeling performance. Furthermore, a thickness of 2.0 μm or less 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 is not 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.

[0089] The outer surface of the film on which the release coating layer is formed (the surface of the release coating layer on the entire coated film that is not in contact with the polyester film) is preferably flat in order to prevent defects from occurring in the ceramic green sheet that is coated and molded on it. Preferably, the average surface roughness (Sa) is 5 nm or less and the maximum protrusion height (P) is 30 nm or less. Furthermore, it is more preferable that the average surface roughness is 5 nm or less and the maximum protrusion height is 20 nm or less. If the surface roughness is 5 nm or less and the maximum protrusion height is 30 nm or less, defects such as pinholes will not occur when forming the ceramic green sheet, resulting in a good yield, which is preferable. A smaller average surface roughness (Sa) is preferable, but it may be 0.1 nm or more, or 0.3 nm or more. Similarly, a smaller maximum protrusion height (P) is preferable, but it may be 1 nm or more, or 3 nm or more.

[0090] In the present invention, in order to adjust the surface of the film on which the release coating layer is formed to a predetermined roughness range, it is preferable that the PET film is substantially free of inorganic particles. In this invention, "substantially free of inorganic particles" is defined as a quantitative analysis of elements derived from particles by X-ray fluorescence analysis of both the base film and the release coating layer, where the concentration is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even without actively adding particles to the base film, contamination components originating from foreign substances, or dirt adhering to the raw resin or the lines and equipment in the film manufacturing process, may peel off and become mixed into the film.

[0091] In the present invention, the method for forming the release coating 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 coating is heated, heat-cured, or UV-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 the flatness of the film, and the risk of causing uneven thickness in the ceramic green sheet is further reduced, which is particularly preferable.

[0092] In the present invention, the surface tension of the coating liquid when applying the release coating 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 surface irregularities of the coating film after drying can be reduced.

[0093] In the present invention, the coating liquid used when applying the release coating 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 solvent added is preferably about 10 to 80% by mass of the total coating liquid.

[0094] Any known coating method can be applied to the above coating liquid. For example, conventional 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.

[0095] (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.

[0096] 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]

[0097] 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.

[0098] [NMR measurement] The ratio of copolymer components introduced into the acrylic polyol is determined by nuclear magnetic resonance spectroscopy ( 1 H-NMR, 13The 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.

[0099] [Checking Tg] The Tg of each 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.

[0100] [Suitability for extension] To evaluate the stretchability of the acrylic polyol itself, synthesized acrylic polyols (1) to (13) were placed in a mixed solvent (25°C) of 30% by mass of isopropanol and 70% by mass of water to a solid content concentration of 12% by mass, to prepare a solution of the acrylic polyol alone. The solution was then applied to the surface of a polyester film that had been stretched only longitudinally using a Meyer bar #5. Next, the film sample with the applied layer (thickness 6.5 μm) was left to stand in a hot air circulating oven set at 60°C for 30 seconds, and then the film sample was removed from the oven for pre-drying. Next, the sample was set in a hand-cranked stretching device (manufactured by Toyobo Engineering Co., Ltd.) and placed in a hot air circulating oven at 100°C, where it was slowly stretched. The stretching operation was continued until the length was four times the length before stretching, and then the stretching device was removed from the hot air circulating oven. Subsequently, the stretched coating film was observed under an optical microscope (magnification: 200x), and the presence or absence of cracking due to stretching was determined according to the following criteria. ○: No cracks are visible at all. △: Some cracks are visible (1 to 4). ×: Five or more cracks, or cracks are visible throughout the entire surface.

[0101] (1) Surface properties of the coated 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.

[0102] (Measurement conditions) • Measurement mode: WAVE mode • Objective lens: 50x 0.5x Tube Lens ·Measurement area 187×139μm (Sa,P measurement) • Measurement length (Lr: reference length): 187 μm (RSm measurement) (2) Evaluation of particle dispersibility of the smooth coating layer (narrow field of view, VertScan measurement field of view 187 × 139 μm) The maximum protrusion height (P) measured in (1) above was judged according to the following criteria.

[0103] ○: Maximum projection height (P) is 0.2 μm or less ○△: The maximum projection height (P) is greater than 0.2 μm and less than 0.3 μm.

[0104] △: Maximum projection height (P) is 0.3 μm or greater. (3) Evaluation of particle dispersibility of the smooth coating layer (wide field of view, visual measurement field: 600mm x 420mm) In a darkroom, four A4-sized release films for green sheet manufacturing were observed visually using an LED light (LED LENSER P5R.2, manufactured by LED LENSER). White particle aggregates were marked and judged according to the following criteria.

[0105] ◎: No particulate matter aggregates ○: 1 to 3 particle aggregates.

[0106] △: Four or more particle aggregates.

[0107] (4) Resistance to falling powder 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 smooth coating 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.

[0108] ○: No powder fallout was observed on the black background.

[0109] △: Slight powder fallout can be observed overall on the black background.

[0110] (5) Surface free energy Under conditions of 25°C and 50% RH, droplets of water (1.8 μL), diiodomethane (0.9 μL), and ethylene glycol (0.9 μL) were prepared on the release surface of a release film using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701), and their contact angles were measured. The contact angle was taken 10 seconds after each liquid was dropped onto the release film. The contact angle data for water, diiodomethane, and ethylene glycol obtained by the above method were calculated using the "Kitazaki-Hata" theory to determine the dispersion component γsd, polar component γsp, and hydrogen bonding component γsh of the surface free energy of the release film, and the sum of these components was defined as the surface free energy γs. This calculation was performed using the calculation software within the contact angle meter software (FAMAS).

[0111] (6) Discharge of release film roll The release films for green sheet manufacturing 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 release film rolls. After storing these release film rolls in an environment of 40°C and humidity of 50% or less for 30 days, the amount of charge when rewinding at 200 m / min was measured using a Kasuga Electric Co., Ltd. "KSD-0103" device. The amount of charge was measured at a point 100 mm immediately after unwinding, every 500 m of unwinding length, and the average value was calculated.

[0112] ○: Less than ±3 kV ○△: ±3 kV or more and less than 5 kV △: ±5 kV or more and less than 10 kV ×: ±10 kV or more (7) Evaluation of pinholes and thickness variations in ceramic green sheets A composition composed of the following materials was stirred and mixed, and dispersed for 2 hours using a paint shaker with 2.0 mm glass beads as the dispersion medium to obtain a ceramic slurry.

[0113] Toluene 22.5% by mass Ethanol 22.5% by mass Barium titanate (HPBT-1 manufactured by Fuji Titanium Co., Ltd.) 50% by mass Polyvinyl butyral (ESREC BH-3 manufactured by Sekisui Chemical Co., Ltd.) 5% by mass Next, the slurry after drying was applied to the release surface of the release film sample using an applicator so that the thickness became 0.5 μm, dried at 90°C for 1 minute, then the slurry surface and the smoothed coating layer surface were overlapped, and after applying a load of 1 kg / cm 2 for 10 minutes, the release film was peeled off to obtain a ceramic green sheet.

[0114] In the central region in the film width direction of the obtained ceramic green sheet, light was applied from the opposite side of the coating surface of the ceramic slurry within a range of 25 cm 2 to observe the occurrence of pinholes through which the light was transmitted and visually judged according to the following criteria.

[0115] ◎: No pinholes generated, and thickness variation is particularly good ○: No pinholes generated, and thickness variation is not particularly problematic △: There are very few pinholes generated, and thickness variation is slightly visible.

[0116] ×: There are a few pinholes generated, and thickness variation is slightly noticeable.

[0117] (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.

[0118] (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)).

[0119] (Manufacturing of laminated film Z) 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 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 PET(I) / (II) = 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 Z with a thickness of 31 μm. The Sa of the obtained film Z was 2 nm on the release side layer and 28 nm on the non-release side layer.

[0120] (Manufacturing of Acrylic Polyol A-1) A four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet was charged with 77 parts by mass of methyl methacrylate (MMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 33 parts by mass of methacrylic acid (MAA), and 490 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 840 parts by mass of an IPA aqueous solution (water content 50% by mass) was added and mixed. Then, while stirring, triethylamine 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 (A-1) with a solid content of 20% by mass. The composition ratio, Tg, stretchability, and acid value of acrylic polyol (A-1) as determined by NMR are shown in Table 1.

[0121] (Manufacturing of acrylic polyols (A-2) to (A-13)) As shown in Table 1, acrylic polyols (A-2) to (A-13) with a solid content of 20% by mass were obtained in the same manner as in the production of acrylic polyol 1, except that the amounts of MMA, St, SMA, HEMA, MAA, AA, IPA at the time of charging, the amount of IPA aqueous solution at the time of dilution, and the neutralizing agent were changed. The composition ratio, Tg, stretchability, acid value, and hydroxyl value of acrylic polyols (A-2) to (A-13) as determined by NMR measurement are also shown in Table 1. The composition ratio is expressed as l-1, l-2, and l-3 (units) for MMA, St (styrene), and SMA (stearyl methacrylate), respectively, m (unit) for HEMA, and n (unit) for MAA and AA (acrylic acid).

[0122] [Table 1]

[0123] (Polymerization of polyester resin B0-1) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 185.1 parts by mass of ethylene glycol, 185.1 parts by mass of neopentyl glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (B0-1). The obtained copolymerized polyester resin (B0-1) was pale yellow and transparent. The reduced viscosity of copolymerized polyester resin (B0-1) was measured to be 0.60 dl / g. The glass transition temperature determined by DSC was 65°C.

[0124] (Manufacturing of polyester aqueous dispersion B-1) In a reactor equipped with a stirrer, thermometer, and reflux device, 30 parts by mass of polyester resin (B0-1) and 15 parts by mass of ethylene glycol-n-butyl ether were added and heated at 110°C, stirring to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (B0-1) with a solid content of 30% by mass.

[0125] (Polymerization of polyester resin B0-2) A stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser was charged with 163 parts by mass of dimethyl terephthalate, 163 parts by mass of dimethyl isophthalate, 169 parts by mass of 1,4-butanediol, 324 parts by mass of ethylene glycol, and 0.5 parts by mass of tetra-n-butyl titanate, and the transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours.

[0126] Next, 14 parts by mass of fumaric acid and 203 parts by mass of sebacic acid were added, and the temperature was raised from 200°C to 220°C over 1 hour to carry out the esterification reaction. Then, the temperature was raised to 255°C, the reaction system was gradually reduced in pressure, and the reaction was carried out under reduced pressure of 29 Pa for 1 hour and 30 minutes to obtain a hydrophobic copolymer polyester resin (B0-2). The obtained hydrophobic copolymer polyester resin (B0-2) was pale yellow and transparent.

[0127] (Manufacturing of polyester aqueous dispersion B-2) Next, 60 parts by mass of the copolymerized polyester resin (B0-2), 45 parts by mass of methyl ethyl ketone, and 15 parts by mass of isopropyl alcohol were placed in a reactor equipped with a graft resin production stirrer, thermometer, reflux device, and quantitative dropper, and the mixture was heated and stirred at 65°C to dissolve the resin. After the resin was completely dissolved, 24 parts by mass of maleic anhydride was added to the polyester solution.

[0128] Next, a solution prepared by dissolving 16 parts by mass of styrene and 1.5 parts by mass of azobisdimethylvaleronitrile in 19 parts by mass of methyl ethyl ketone was added dropwise to the polyester solution at a rate of 0.1 ml / min, and stirring was continued for a further 2 hours. After sampling the reaction solution for analysis, 8 parts by mass of methanol was added. Then, 300 parts by mass of water and 24 parts by mass of triethylamine were added to the reaction solution, and the mixture was stirred for 1 hour.

[0129] Subsequently, the internal temperature of the reactor was raised to 100°C, and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were removed by distillation to obtain a pale yellow transparent polyester resin, and a homogeneous water-dispersible polyester graft copolymer dispersion (B-2) with a solid content of 25% by mass was prepared. The glass transition temperature of the obtained polyester graft copolymer was 68°C.

[0130] (Manufacturing of polyurethane aqueous dispersion C-1) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 43.75 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, 153.41 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 450 g of water was added, the temperature was adjusted to 25°C, and the mixture was stirred for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-soluble polyurethane resin solution C-1 with a solid content of 37% by mass was prepared by removing some of the acetone and water. The glass transition temperature of the obtained polyurethane resin was -30°C.

[0131] (Melamine-based crosslinking agent D-1) Methylated melamine (manufactured by Sanwa Chemical, product name Nikalac MX-035, solid content concentration 70% by mass) (Melamine-based crosslinking agent D-2) Methyl / n-butylated melamine (manufactured by Sanwa Chemical, product name Nikalac MX-45, solid content concentration 100% by mass) (Silica particles E-1) Colloidal silica (manufactured by Nissan Chemical Corporation, product name MP2040, average particle size 200 nm, solid content concentration 40% by mass) (Silica particles E-2) Colloidal silica (manufactured by Nissan Chemical Corporation, product name Snowtex XL, average particle size 40 nm, solid content concentration 40% by mass) (Silica particles E-3) Colloidal silica (manufactured by Nissan Chemical Corporation, product name Snowtex ZL, average particle size 100 nm, solid content concentration 40% by mass) (Silica particles E-4) Colloidal silica (manufactured by Nissan Chemical Corporation, product name MP4540M, average particle size 450nm, solid content concentration 40% by mass) (Acrylic particles E-5) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX100W, average particle size 150 nm, solid content concentration 10% by mass) (Acrylic particles E-6) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX200W, average particle size 350 nm, solid content concentration 10% by mass) (Acrylic particles E-7) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX300W, average particle size 450 nm, solid content concentration 10% by mass) (Release agent solution X-1) A release agent solution with a solid content of 2% by mass was prepared by diluting 100 parts by mass of thermosetting amino alkyd resin (Tesfine 314, manufactured by Hitachi Chemical Co., Ltd., 60% by mass of solids) and 1.2 parts by mass of p-toluenesulfonic acid (Dryer 900, manufactured by Hitachi Chemical Co., Ltd., 50% by mass of solids) as a curing catalyst with a toluene / methyl ethyl ketone / heptane (=3:5:2) solution.

[0132] (Release agent solution X-2) A mold release agent solution with a solid content of 2% by mass was prepared by diluting 100 parts by mass of UV-curable silicone resin (Momentive UV9300, solid content concentration 100% by mass) and 1 part by mass of curing catalyst bis(alkylphenyl)iodonium hexafluoroantimonate with a toluene / methyl ethyl ketone / heptane (=3:5:2) solution.

[0133] (Example 1) (Preparation of lubrication coating solution 1) A lubrication solution 1 with the following composition was prepared.

[0134] (Smooth coating liquid 1) Water 45.51 parts by mass Isopropyl alcohol 35.00 parts by mass Acrylic polyol resin A-1 (solid content concentration 20% by mass) 16.57 parts by mass Melamine-based crosslinking agent D-1 (solid content concentration 70% by mass) 2.03 parts by mass Silica particles E-1: 0.59 parts by mass (Average particle size 200nm, solids concentration 40% by mass) Surfactant F-1 (silicone-based, solid content concentration 10% by mass) 0.30 parts by mass (Manufacturing of polyester film) 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.

[0135] 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.

[0136] Next, the above-mentioned lubrication 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 an in-line coated polyester film with a thickness of 31 μm.

[0137] (Formation of release coating layer) The release agent solution X-1 was applied to the inline coated polyester film obtained above, on the surface opposite to the laminated surface of the slip-free coating layer, using a reverse gravure coater to a thickness of 0.1 μm after drying. Then, a release coating layer was formed by drying with hot air at 130°C for 30 seconds, yielding a release film for the manufacture of ultrathin ceramic green sheets. Winding performance, process passability, and handling performance were excellent with no particular problems. After winding as a roll, the electrostatic charge when unwinding again for ceramic sheet coating was low, suppressing the adhesion of environmental foreign matter, and enabling the production of high-quality ceramic capacitors without reducing the yield of ceramic capacitors.

[0138] (Example 2) A release film for manufacturing an ultrathin ceramic green sheet was obtained in the same manner as in Example 1, except that a release film for manufacturing an ultrathin ceramic green sheet was used the release film for manufacturing an ultrathin ceramic green sheet was used in the release film for manufacturing an ultrathin ceramic green sheet was used in the same manner as in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in the release film for manufacturing an ultrathin ceramic green sheet was used in the same manner as in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the release film for manufacturing an ultrathin ceramic green sheet was used in Example 1, except that the

[0139] (Examples 3-19, 21-24) A polyester film was obtained in the same manner as in Example 1, except that the lubrication coating liquid 1 was changed as shown in Table 2.

[0140] (Example 20) A release film for manufacturing an ultrathin ceramic green sheet was obtained in the same manner as in Example 1, except that the release coating layer was formed as described below.

[0141] (Formation of release coating layer) The obtained inline coated polyester film was coated with release agent solution X-2 using a reverse gravure coater to a thickness of 0.1 μm after drying. Then, it was dried with hot air at 90°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 and obtain a release film for manufacturing ultrathin ceramic green sheets.

[0142] (Comparative Examples 1-4) A polyester film was obtained in the same manner as in Example 1, except that the lubrication coating liquid 1 was changed as shown in Table 2.

[0143] (Comparative Example 5) A release film for manufacturing ceramic green sheets was obtained in the same manner as in Example 1, except that E5000-25μm (manufactured by Toyobo) was used as the film for forming the release coating layer, instead of the inline coating film with an easy-slip coating layer on one surface prepared in Example 1. E5000 contained particles inside the film, and the Sa on both surfaces was 0.031μm.

[0144] (Comparative Example 6) A release film for manufacturing ceramic green sheets was obtained in the same manner as in Example 1, except that the inline coating film prepared in Example 1, which had a smooth coating layer on one surface, was replaced with a laminated film Z as the film for forming the release coating layer. The release coating layer was applied to the side of the laminated film Z from which the PET(II) pellets were ejected (the layer that does not contain particles).

[0145] Table 2 shows the evaluation results for each example and comparative example.

[0146] [Table 2]

[0147] In Table 2 above, the composition of the resin, crosslinking agent, particles, and surfactant in the lubrication solution is listed as parts by mass of solids. The sum of the parts by mass of solids of the resin, crosslinking agent, particles, and surfactant present in the lubrication solution equals the total parts by mass of solids in the lubrication layer. By dividing the parts by mass of solids of each component by the total parts by mass of solids in the lubrication layer, the mass percentage of the resin, crosslinking agent, particles, and surfactant in the lubrication layer can be determined.

[0148] In Examples 1 to 24, the discharge charge was low when the roll was unwound again after the release process, and environmental foreign matter was less likely to adhere. As a result, high-quality ceramic capacitors could be produced without reducing the yield of ceramic capacitors. The release film used as a base material was a polyester film that substantially does not contain inorganic particles. The base material had a release coating layer on one surface and a slip-free coating layer containing particles on the other surface. The slip-free coating layer was formed by curing a composition containing acrylic resin and a melamine-based crosslinking agent. This resulted in a high crosslinking density in the slip-free coating layer and a small amount of deformation of the slip-free coating layer. It is believed that the amount of charge generated was suppressed because the contact area between the release layer and the slip-free layer was reduced when the release-processed film roll was unwound.

[0149] On the other hand, in Comparative Examples 1 to 4, since the easy-slip coating layer is not formed by curing a composition containing the acrylic resin and melamine-based crosslinking agent specified in the present invention, the crosslinking density of the easy-slip coating layer is low, and the amount of deformation of the easy-slip coating layer is large. It is thought that the discharge charge increased because the contact area was large when the release layer and the easy-slip layer were separated when the release-processed film roll was unwound. In addition, although the discharge charge was low in Comparative Examples 5 and 6, they did not have the easy-slip coating layer specified in the present invention, and the surface roughness of the easy-slip surface was large, resulting in the occurrence of pinholes in the ceramic sheet. [Industrial applicability]

[0150] According to the present invention, it is possible to provide a release film for manufacturing ceramic green sheets that can simultaneously prevent pinholes and localized thickness variations, as well as prevent the adhesion of environmental foreign matter due to static electricity, even when the ceramic green sheet is made into a thin film. Furthermore, by using the release film for manufacturing ceramic green sheets of the present invention, an ultrathin ceramic green sheet can be obtained, and tiny ceramic capacitors can be manufactured efficiently.

Claims

1. Using polyester film as the base material, The substrate has a release coating layer on one surface and a smooth coating layer containing particles on the other surface. When elements originating from inorganic particles were quantitatively analyzed by X-ray fluorescence analysis of both the base film and the release coating layer, the concentration was 50 ppm or less. The aforementioned smooth coating layer is formed by curing a composition containing an acrylic resin, a crosslinking agent, and a surfactant. The aforementioned crosslinking agent is a melamine-based crosslinking agent. The hydroxyl value of the acrylic resin is 50 mg KOH / g or more and 450 mg KOH / g or less. Release film for manufacturing ceramic green sheets.

2. The release film for manufacturing ceramic green sheets according to claim 1, wherein the glass transition temperature of the acrylic resin is 50°C or more and 110°C or less.

3. The release film for manufacturing ceramic green sheets according to claim 1, wherein the average surface roughness (Sa) of the slippery coating layer is 1 nm or more and 25 nm or less, the maximum protrusion height (P) is 60 nm or more and 500 nm or less, and the average length (RSm) of the roughness curve elements is 10 μm or less.

4. The release film for manufacturing ceramic green sheets according to claim 1, wherein the thickness of the slip-free coating layer is 0.001 μm or more and 2 μm or less.

5. A polyester film that substantially does not contain inorganic particles is used as the base material. The substrate has a release coating layer on one surface and a smooth coating layer containing particles on the other surface. The aforementioned smooth coating layer is formed by curing a composition containing an acrylic resin, a crosslinking agent, and a surfactant. The aforementioned crosslinking agent is a melamine-based crosslinking agent. The hydroxyl value of the acrylic resin is 50 mg KOH / g or more and 450 mg KOH / g or less. Release film for manufacturing ceramic green sheets.

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