Release film

Abstract

Provided is a release film that has suitable release properties even when a resin sheet such as a ceramic green sheet is thinned, and thus suppresses the transfer of ceramic green sheets.　The present invention has a polyester film base material, a release layer on one surface of the base material, and a slippery layer containing particles on the surface of the base material opposite from the surface on which the release layer is provided. The surface free energy γsa (mJ / m2) of the release layer and the surface free energy γsb (mJ / m2) of the slippery layer satisfy formulas 1, 2, and 3. Formula (1): 15 ≤ γsa ≤ 40. Formula (2): 25 ≤ γsb ≤ 45. Formula (3): -20 ≤ γsa-γsb ≤ 20.

Description

Release film

[0001] This invention relates to a release film for manufacturing ceramic green sheets. More specifically, it relates to a release film that has good release properties and suppresses transfer of ceramic green sheets, even when resin sheets such as ceramic green sheets are thinned.

[0002] Typically, in the manufacturing process of multilayer ceramic capacitors, ceramic slurry is molded onto a release film, rolled into a roll, and then proceeded to the next process. In recent years, with the increasing thinning of ceramic green sheets, attention has been paid not only to the smoothness of the surface of the release layer, but also to the smoothness of the back surface of the release film (the side opposite the release layer) because it comes into contact with the ceramic green sheet in a rolled state. To address this, techniques have been developed to reduce the height of protrusions by filling the protrusions on the back surface with a coating layer, or by providing a smooth layer with reduced protrusion height.

[0003] For example, Patent Document 1 discloses a technique to prevent pinholes and localized thickness variations in a ceramic green sheet by filling the protrusions on the back surface with a coating layer in order to reduce the height of the protrusions. Furthermore, Patent Document 2 discloses a technique for applying a smoothing layer to the back surface of a film.

[0004] Japanese Patent Publication No. 2014-144636 Japanese Patent Publication No. 2024-119013

[0005] As shown in Patent Document 1, if the protrusions on the back surface are filled with a coating layer to reduce the height of the protrusions and prevent pinholes and localized thickness variations in the ceramic green sheet, although the protrusion height is reduced, the protrusion density is low, resulting in high pressure on the protrusions. When the ceramic green sheet is further thinned, there is a problem in that pinholes occur. As shown in Patent Document 2, when urethane or polyester is used to provide a smooth layer on the back surface of the film, adhesion is established with the resin used in the ceramic green sheet, and there is a risk that the ceramic green sheet will transfer to the smooth layer side. As the thinning of ceramic green sheets progresses further in the future, it is expected that the tension during the ceramic green sheet coating process will be increased in order to control the uniform coating thickness of the ceramic green sheet. If a release film with a high surface smoothness is used, the ceramic green sheet is coated under high tension, and then wound into a roll, there is a risk of further blocking occurring, and it is possible that the ceramic green sheet will transfer to the smooth layer side when the roll is unwound.

[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 release properties and suppresses transfer of ceramic green sheets, even when resin sheets such as ceramic green sheets are made into thin films.

[0007] The present invention can be shown in the following embodiments: [1] A smooth layer containing particles, a polyester film substrate, and a release layer in this order, wherein the surface free energy of the release layer is γs a(mJ / m 2 ) and the surface free energy γs b(mJ / m) of the slippery layer 2A release film in which the following formulas 1, 2, and 3 are satisfied: 15 ≤ γs a ≤ 40 (Formula 1) 25 ≤ γs b ≤ 45 (Formula 2) - 20 ≤ γs a - γs b ≤ 20 (Formula 3) [2] The release film according to [1], wherein the substrate is a polyester film substrate that substantially does not contain inorganic particles. [3] The release film according to [1] or [2], wherein the average surface roughness (Sa) of the release layer region is 0.1 nm or more and 30 nm or less, and the maximum protrusion height (P) is 0.1 nm or more and 500 nm or less. [4] The release film according to any one of [1] to [3], wherein the average surface roughness (Sa) of the smooth layer 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. [5] A release film according to any one of [1] to [4], wherein the smooth layer is formed by curing a composition containing an acrylic resin containing a long-chain alkyl group and at least one crosslinking agent selected from oxazoline-based crosslinking agents or carbodiimide-based crosslinking agents. [6] A release film according to any one of [1] to [5], wherein the release layer is formed by curing a composition containing an acrylic resin containing a long-chain alkyl group and a melamine-based compound. [7] A release film according to any one of [1] to [6], wherein the resin containing the long-chain alkyl group is an acrylic resin, and the acrylic resin contains at least component A-1 represented by the following chemical formula (Chemical Formula 1).

[0008] In formula (1), R １ is (CnH2n+1) (n = an integer between 8 and 20), R ４ is H or CH ３ [8] A release film according to any one of [1] to [7], wherein the thickness of the release layer is 0.001 μm or more and 2 μm or less. [9] A release film according to any one of [1] to [8], wherein the release film is a release film for manufacturing ceramic green sheets.

[10] A method for manufacturing a release film according to any one of [1] to [9], comprising coating an easy-slip layer forming composition onto an unstretched film or a uniaxially oriented film, and after coating the easy-slip layer forming composition, heat-setting the film at 80°C to 270°C in an unstretched state or after stretching at least uniaxially.

[0009] According to the present invention, a release film is provided that has good release properties and suppresses transfer of the ceramic green sheet, even when a resin sheet such as a ceramic green sheet is made into a thin film.

[0010] The present invention will be described in detail below. The release film of the present invention has the following characteristics: It comprises, in this order, a smooth layer containing particles, a polyester film substrate, and a release layer, and the surface free energy of the release layer is γs a(mJ / m 2 ) and the surface free energy γs b(mJ / m) of the slippery layer 2 A release film in which the following equations 1, 2, and 3 are satisfied: 15 ≤ γs a ≤ 40 (Equation 1) 25 ≤ γs b ≤ 45 (Equation 2) - 20 ≤ γs a - γs b ≤ 20 (Equation 3) In one embodiment, the release film of the present invention is a release film for manufacturing ceramic green sheets.

[0011] The release film of the present invention has a highly smooth, slippery layer, which suppresses pinholes even when a resin sheet such as a ceramic green sheet is made into a thin film. Furthermore, because the surface free energy is within a desired range, the transfer of the ceramic green sheet to the slippery layer can be suppressed even under high load conditions.

[0012] (Base material) The film preferably used as a base material in the present invention 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.

[0013] Furthermore, the polyester film may be single-layered or multi-layered. Within the range that achieves the desired effects in the present invention, various additives may be incorporated into the polyester resin in 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, which is the base material in the present invention, substantially does not contain particles with a particle size of 1.0 μm or larger. If the base material has a multilayer structure, the layer forming the surface in contact with the release layer substantially does not contain particles with a particle size of 1.0 μm or larger. Hereinafter, whether the base material has a single-layered or multilayer structure, it is desirable that the layer forming the surface in contact with the release layer exhibits the following characteristics. Furthermore, the base material may contain particles with a particle size of less than 1.0 μm and greater than or equal to 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, reducing the likelihood of defects occurring due to the transfer of particle shapes from the base material to resin sheets such as green sheets.

[0014] In one embodiment, by not including any 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.

[0015] 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.

[0016] 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.

[0017] 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 when quantified by fluorescence X-ray analysis 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 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.

[0018] 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.

[0019] (Slippery layer) The release film of the present invention has a slippery layer on one surface of a polyester base film as described above. Preferably, the slippery layer contains at least a binder resin and particles.

[0020] (Binder resin in the smooth layer) The binder resin constituting the smooth layer in the present invention 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%. It is preferable that the constituent units having hydroxyl groups constitute 20 mol% or more, as this can appropriately maintain the water solubility of the acrylic resin. On the other hand, it is preferable that the constituent units having hydroxyl groups constitute 90 mol% or less, as this prevents extreme interaction between the hydroxyl groups of the acrylic resin and the particles contained in the smooth layer, resulting in uniform dispersion of the particles.

[0021] 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 copolymer 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.

[0022] 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.

[0023] The hydroxyl value of the acrylic resin is preferably 250 mg KOH / g or less, more preferably 230 mg KOH / g or less, and even more preferably 200 mg KOH / g or less. A hydroxyl value of 250 mg KOH / 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 layer, resulting in uniform particle dispersion.

[0024] 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 the 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.

[0025] 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 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.

[0026] 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 sufficient water solubility, facilitates mixing of alcohols and other substances during coating solution preparation.

[0027] 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. A 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.

[0028] 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 layer, resulting in uniform particle dispersion. Good particle dispersibility is preferable because it prevents the formation of large protrusions on the smooth coated surface and prevents the formation of pinholes in the ceramic sheet.

[0029] 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 layer.

[0030] 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 the application of the smooth layer, resulting in uniform stretching.

[0031] (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)acrylate esters 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.

[0032] Further, examples of the non-acrylic vinyl monomers include: styrene-based 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 octylate, vinyl monochloroacetate, divinyl adipate, vinyl crotonate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate; and halogenated vinyl monomers such as vinyl chloride and vinylidene chloride. One or two or more of these may be used.

[0033] The Tg adjusting monomer is preferably the remaining portion after determining appropriate amounts of the hydroxyl group-containing monomer and the carboxyl group-containing monomer. The Tg of the copolymer is determined by the following Fox equation.

[0034] W n : mass fraction (mass%) of each monomer; Tg n : Tg (K) of the homopolymer of each monomer

[0035] As a monomer to be copolymerized for Tg adjustment, a component that reduces surface free energy, such as a long-chain alkyl group, is preferably introduced. As the acrylic resin having a long-chain alkyl group introduced therein, those having an alkyl group with about 8 to 20 carbon atoms in a side chain of the acrylic resin are preferable. Further, copolymers which are polymers having (meth)acrylic acid esters as main repeating units and contain a long-chain alkyl group with 8 to 20 carbon atoms in a transesterified moiety can also be suitably used.

[0036] 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.

[0037] 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 in 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.

[0038] 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.

[0039] 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.

[0040] In the present invention, other binder resins may be used in combination with acrylic resin as the binder for the smooth-slip layer. Examples of other binder resins include polyester resin, urethane resin, polyvinyl resin (such as polyvinyl alcohol), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, and starches.

[0041] The content of the active ingredient in the smooth layer of the acrylic resin is preferably 20% by mass or more and 95% by mass or less of the total active ingredient. More preferably, it is 30% by mass or more and 90% by mass or less. If it is 20% by mass or more, it is preferable because the amount of carboxyl groups, which are the crosslinking components, does not become too small and the crosslinking density does not become low. If it is 95% by mass or less, it is preferable because the amount of the crosslinking agent, which is the target of crosslinking, does not become too small and the crosslinking density does not become low.

[0042] (Crosslinking agent) In the present invention, it is preferable that the smooth 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 layer. By including an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent, the adhesion to the PET substrate can be improved, and the coating strength 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.

[0043] Examples of crosslinking agents having an oxazoline group include polymers having an oxazoline group obtained by copolymerizing a polymerizable unsaturated monomer having an oxazoline group with other polymerizable unsaturated monomers as needed using conventionally known methods (e.g., solution polymerization, emulsion polymerization, etc.).

[0044] 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.

[0045] Other polymerizable unsaturated monomers include, for example, alkyl or cycloalkyl esters of (meth)acrylic acid having 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 having 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.

[0046] 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 2-hydroxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, monomers having polyethylene glycol chains such as 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, sodium styrene sulfonate, etc. 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 an OH group, -NH2 group, COOH group, or SO3H group can also be used as end-encapsulating agents.

[0051] 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.

[0052] 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.

[0053] The carbodiimide 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 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.

[0054] 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.

[0055] The preferred content of the crosslinking agent in the smooth layer is 5% by mass or more and 80% by mass or less of the total active ingredients. 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 coated 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 reduce the crosslinking density.

[0056] (Particles in the lubricating layer) The lubricating layer preferably contains lubricant particles in order 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. The use of organic particles is particularly preferable in that it prevents the particles from falling off the slippery layer. Using organic particles is preferable because it strengthens the interaction between the binder and crosslinking agent components of the smooth 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 smooth layer, are particularly preferred in terms of preventing the particles from detaching from the smooth layer.

[0057] 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.

[0058] 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.

[0059] 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 (RSm) of the roughness curve elements while keeping the average surface roughness (Sa) and maximum protrusion height (P) of the region small, 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 active ingredients of the coating layer.

[0060] 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.

[0061] 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.

[0062] The ratio of particles to the total active ingredients in the smooth 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 active ingredients in the smooth layer of 50% by mass or less is preferable because it maintains transparency and prevents significant particle shedding from the smooth layer.

[0063] The ratio of particles to the total active ingredients of the lubricating 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 active ingredients of the lubricating layer of 1% by mass or more is preferable as it ensures lubricity.

[0064] As a method for measuring the particle content in the smooth layer, for example, if the smooth layer contains organic resin components and inorganic particles, the following method can be used. First, the smooth layer provided on 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 smooth layer, and the organic components contained in the smooth layer are burned off by heat, thereby obtaining only the inorganic components. By measuring the weight of the obtained inorganic components and the smooth layer before burning and distillation, the mass percentage of particles contained in the smooth 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 effective components of the smooth layer refers to the ratio of the total amount of multiple types of particles if multiple types of particles are present.

[0065] (Additives in the smooth layer) Various additives may be included in the smooth layer to impart other functionalities, as long as 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.

[0066] The smoothing layer may contain surfactants to improve leveling properties 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 appearance of the coating due to excessive addition.

[0067] 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.

[0068] 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.

[0069] In the present invention, a method for providing a smooth 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.

[0070] The concentration of the active ingredient in 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 concentration of the active ingredient in the coating solution is preferably 35% by mass or less, and more preferably 20% by mass or less.

[0071] The drying temperature after application also depends on the type of binder resin, the type of solvent, the presence or absence of a crosslinking agent, and the concentration of the active ingredient, but it is preferably 70°C or higher and preferably 250°C or lower.

[0072] (Manufacturing of Polyester Film) In the present invention, the polyester film that will serve as the base film can be manufactured according to a general method for manufacturing polyester film. For example, one method involves melting polyester resin, extruding it into a sheet, stretching the unoriented polyester in the longitudinal direction 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 the longitudinal and transverse directions within a tenter.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The thickness of the smooth 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.

[0078] The thickness of the smooth 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 thickness of 2 μm or less for the coated layer is preferable because it eliminates the risk of blocking.

[0079] The ceramic green sheet, which is coated and molded onto the release layer described later, is wound into a roll together with the release film after coating and molding. At this time, the slip-free layer of the release film 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 slip-free layer (the surface of the slip-free layer of the entire coated 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.

[0080] If the average surface roughness (Sa) of the outer surface of the slippery layer is 1 nm or more and the maximum protrusion height (P) is 60 nm or more, it is preferable because the slippery coated 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 slippery coated surface does not become too rough and defects in the ceramic green sheet do not occur due to protrusions.

[0081] In the present 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 slippery 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.

[0082] 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 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 RSm is adjusted within the predetermined range, which is preferable.

[0083] The surface free energy γsb of the slippery layer is 45 mJ / m ２ Preferably, it is 41 mJ / m ２ It is more preferable that the following conditions apply: 40.5 mJ / m ２ It is more preferable that the surface free energy of the slippery layer is 45 mJ / m ２ The following is preferable, as it makes it less likely for the ceramic green sheet to transfer to the smooth layer when the ceramic green sheet is applied, wound, and then unwound. Furthermore, it is preferable that environmental foreign matter does not adhere to the material during the process, foreign matter does not adhere to the release surface, and pinholes caused by environmental foreign matter do not occur in the ceramic green sheet.

[0084] The surface free energy γsb of the slippery layer is 25 mJ / m ２ Preferably, it is 30 mJ / m ２ It is more preferable that the surface free energy of the slippery layer is 25 mJ / m ２ This is preferable because it suppresses the shedding of particles in the smooth layer. This numerical range can be expressed as 25 ≤ γs b ≤ 45 (Equation 2).

[0085] (Release Layer) The release layer in the present invention comprises a long-chain alkyl group-containing acrylic resin, a melamine compound, and a low-molecular-weight polyol. For example, a release layer can be formed by curing a release layer-forming composition comprising a long-chain alkyl group-containing acrylic resin, a melamine compound, and a low-molecular-weight polyol. In one embodiment, the release layer of the present invention comprises a release additive.

[0086] (Long-chain alkyl group-containing acrylic resin) The long-chain alkyl group-containing acrylic resin may be, for example, an acrylic polymer copolymerized with long-chain alkyl acrylates, a graft polymer with long-chain alkyl grafts, or a block polymer with long-chain alkyl groups attached to its ends. Similar embodiments can be adopted for polyester resins and the like that may be included in the matrix. The details of the long-chain alkyl group-containing acrylic resin will be described below as an example, but the same applies to polyester resins and the like that may be included in the matrix. For example, the long-chain alkyl group-containing acrylic resin includes an acrylic resin in which the long-chain alkyl group has 8 or more carbon atoms and 20 or less carbon atoms.

[0087] The long-chain alkyl group-containing acrylic resin preferably contains at least component A-1 represented by the following chemical formula (1).

[0088]

[0089] In formula (1), R １ is (CnH2n+1) (n = an integer between 8 and 20), R ４ is H or CH ３ This indicates.

[0090] The long-chain alkyl group-containing acrylic resin may also contain component A-2, represented by the following chemical formula (2).

[0091]

[0092] In formula (2), R ２ (CmH2mOH) (m = an integer between 1 and 10) or H, R ４ is H or CH ３ This indicates.

[0093] As a long-chain alkyl group-containing acrylic resin, the constituent units of component A-1 and component A-2 are preferably in the range of A-1: ​​20 to 100% by weight and A-2: 0 to 80% by weight, respectively, relative to the weight of the acrylic resin, and more preferably in the range of A-1: ​​30 to 100% by weight and A-2: 0 to 70% by weight. If component A-1 is 20% or more, sufficient peelability can be obtained from thin-film ceramic sheets.

[0094] In formula (1) showing component A-1, R １ The C1 is an alkyl group with 8 to 20 carbon atoms. When the C1 is 8 or more, component A-1 exhibits good release properties. On the other hand, when the C1 is 20 or less, the flexibility of component A-1 can be maintained, and sufficient wettability of the release layer film surface can be ensured. Furthermore, the cohesive force of the acrylic resin can be suppressed, resulting in no protrusions derived from aggregates and ensuring sufficient smoothness. The C1 is preferably 8 to 18, and more preferably 8 to 16. Also, R １ The chain may be linear or branched.

[0095] In formula (1) showing component A-1, R ４ is H or CH ３ All of these are suitable. As the raw material for component A-1, the monomer shown in the following chemical formula (3) can be used.

[0096]

[0097] In formula (3), R １ is (CnH2n+1) (n = an integer between 8 and 20), R ４ is H or CH ３ This indicates.

[0098] Specifically, lauryl (meth)acrylate, stearyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, etc. can be used as raw materials for component A-1.

[0099] R in equation (2) that represents the A-2 component ２ In particular, the number of carbon atoms m is 1 or more and 10 or less. When the number of carbon atoms m is 10 or less, it is possible to avoid the crosslinking density of the release layer of the present invention becoming sparse, to suppress the weakening of the cohesive force of the release layer itself, and further, to suppress the increase in peeling force. The number of carbon atoms m is preferably 2 or more and 8 or less, and more preferably 2 or more and 4 or less.

[0100] In formula (2) showing component A-2, R ４ is H or CH ３ All of these are suitable. As the raw material for component a-2, the monomer shown in the following chemical formula (4) can be used.

[0101]

[0102] In formula (4), R ２ is (CmH ２ mOH) (m = an integer between 1 and 10) or H, R ４ is H or CH ３ This indicates.

[0103] Specifically, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc., can be used as raw materials for component A-2.

[0104] In addition to components A-1 and A-2, other materials such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate may also be used as raw materials for the third component.

[0105] In the present invention, the content of the long-chain alkyl group-containing acrylic resin in the release layer is preferably 0.1% by mass or more, and more preferably 1% by mass or more, based on 100% by mass of the total amount of active ingredients in the release layer. In one embodiment, the content of the long-chain alkyl group-containing acrylic resin is 35% by mass or less, for example, 20% by mass or less, based on 100% by mass of the total amount of active ingredients in the release layer. If the content is 0.1% by mass or more, good peeling from the ceramic green sheet is possible. If the content is 35% by mass or less, the surface free energy does not become too low, and the transfer of the ceramic green sheet to the slippery layer can be suppressed.

[0106] (Melamine-based compound) The melamine-based compound (b) used in the release layer in the present invention can be any general 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, 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 formaldehyde is preferred. Examples of methylolated melamine derivatives include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, and hexamethylolmelamine. One type or two or more types may be used.

[0107] 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 Examples include Nikarac MW-390, Nikarac MW-100LM, Nikarac MX-750LM, Nikarac MW-22, Nikarac MS-21, Nikarac MS-11, Nikarac MW-24X, Nikarac MS-001, Nikarac MX-002, Nikarac MX-730, Nikarac MX-750, Nikarac MX-708, Nikarac MX-706, Nikarac MX-042, Nikarac MX-035, Nikarac, MX-45, Nikarac MX-43, Nikarac MX-417, and Nikarac MX-410 (manufactured by Nippon Carbide Co., Ltd.). Among these, full-ether type methylated melamine resin is preferred in terms of curability at low temperatures and in a short time, and adhesion to polyester film. Examples of commercially available products include the Cymel 303LF and the Nikarac MW-30.

[0108] In the present invention, it is preferable to add an acid catalyst to the release layer to promote the crosslinking reaction of the melamine-based compound, and it is preferable to add the acid catalyst to the release 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.

[0109] 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.

[0110] 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 the release layer at lower temperatures. This is preferable because it suppresses the decrease in film flatness and deterioration of the winding appearance caused by heat during processing.

[0111] The sulfonic acid catalyst used in the present 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.).

[0112] The low molecular weight polyol (c) contained in the release layer in the present invention can be any common polyol and is not particularly limited, but examples include aliphatic diols such as 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, butylethylpropanediol, and butylethylpentanediol; aliphatic and aromatic cyclic diols such as 1,4-cyclohexanedimethanol and 1,4-benzenedimethanol; trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, dimer diol, hydrogenated dimer diol, trimertriol, hydrogenated trimertriol, castor oil, castor oil-based modified polyols, alkylene oxide adducts of bisphenol compounds or their derivatives, and one or more of these can be used. By adding these polyols, the crosslinking density of the release layer is increased, resulting in improved solvent resistance and elastic modulus, making it easier to peel off the ceramic green sheet.

[0113] In the present invention, the total content of melamine compounds and low molecular weight polyols in the release layer is preferably 60% by mass or more, and more preferably 80% by mass or more, based on 100% by mass of the total amount of active ingredients in the release layer. In one embodiment, the total content of melamine compounds and low molecular weight polyols is 99.9% by mass or less, for example, 98% by mass or less, based on 100% by mass of the total amount of active ingredients in the release layer. If the total content is 60% by mass or more, sufficient solvent resistance can be obtained and good peeling from the ceramic green sheet can be achieved. Furthermore, by increasing the content of low molecular weight raw materials, the viscosity of the coating liquid can be suppressed, preventing groove-like streaks caused by coating from leveling and remaining on the coating surface, thus preventing a decrease in the smoothness of the release layer.

[0114] In the present invention, release agents such as silicone, wax, or long-chain alkyl pendant polymers without reactive groups may be added to the release layer to adjust the release force, provided that they do not hinder the effects of the present invention.

[0115] In the present invention, additives such as adhesion enhancers and antistatic agents may be added to the release layer, provided that they do not hinder the effects of the present invention, but it is preferable that the release layer does not contain particles. By not containing particles in the release layer, deterioration of the smoothness of the release layer surface and the mixing of particles into the resin sheet due to particle detachment can be suppressed. In order to improve adhesion to the substrate, pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment can be performed on the surface of the polyester film before applying the release layer.

[0116] 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 160°C or lower, and most preferably 140°C or lower. The heating time is preferably 30 seconds or less, more preferably 20 seconds or less, and even more preferably 10 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 unevenness in the thickness of the release layer, which is preferable. When the temperature is 140°C or lower, the film can be processed without impairing its flatness, and the risk of causing unevenness in the thickness of the release layer is further reduced, which is particularly preferable.

[0117] In the present invention, the coating liquid used when applying the release layer is not particularly limited, but it is preferable to add a solvent with a boiling point of 70°C or higher. Adding a solvent with a boiling point of 70°C or higher prevents bumping during drying, levels the coating film, and improves the flatness of the coating film surface after drying. The amount of the solvent added is preferably about 50 to 99% by mass of the total coating liquid.

[0118] 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.

[0119] The release 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 not to substantially contain any particles or other materials that form protrusions.

[0120] 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 before applying the release layer, such as by applying an anchor coat, corona treatment, plasma treatment, or atmospheric pressure plasma treatment.

[0121] 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 release layer after curing is in the range of 0.005 to 2.0 μm. A release layer thickness of 0.005 μm or more is preferable because it maintains peeling performance. Furthermore, a release layer 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. Also, because the curing time does not become too long, there is no risk of the resin constituting the release layer agglomerating and forming protrusions, so it is preferable that pinhole defects in the ceramic green sheet do not occur easily.

[0122] The outer surface of the film on which the release layer is formed (the release layer surface of 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 surface of the release layer on the side opposite to the substrate is preferably 0.1 nm or more and 5 nm or less, for example, 0.2 nm or more and 4.5 nm or less. The maximum protrusion height (P) is preferably 1 nm or more and 100 nm or less, for example, 1 nm or more and 50 nm or less. If the surface roughness of the region is 5 nm or less, or the maximum protrusion height is 100 nm or less, defects such as pinholes will not occur during sheet formation, and the yield will be good, which is preferable.

[0123] The release film of the present invention has a surface free energy γs a(mJ / m) of the release layer. 2 ) and the surface free energy γs b(mJ / m) of the slippery layer 2 The following equations 1, 2, and 3 are satisfied: 15 ≤ γs a ≤ 40 (Equation 1) 25 ≤ γs b ≤ 45 (Equation 2) - 20 ≤ γs a - γs b ≤ 20 (Equation 3)

[0124] By satisfying the above (Equation 1), (Equation 2), and (Equation 3), the thinned ceramic green sheet can be peeled off without defects, and the ceramic green sheet on the release layer can be held appropriately, suppressing the transfer of the ceramic green sheet to the slippery layer when the ceramic green sheet is wound after coating and then unwound. Furthermore, the present invention can suppress the phenomenon in which the green sheet is temporarily transferred to the slippery layer during winding and returns to the release layer when unwound, thereby suppressing the occurrence of defects in the green sheet caused by transfer to the slippery layer. Since such temporary transfer during winding can be suppressed, it is thought that the occurrence of pinholes in the green sheet can be suppressed, and furthermore, thickness variations can also be suppressed.Therefore, it is thought that the release film of the present invention can maintain a state in which the green sheet and the release layer are in close contact even during winding.

[0125] The surface free energy γs a of the release layer is 40 mJ / m ２ The following is true: 35 mJ / m ２ It is more preferable that the surface free energy of the release layer is 40 mJ / m ２ The following conditions ensure sufficient peelability, allowing the ceramic green sheet to be peeled off without defects.

[0126] The surface free energy γs a of the release layer is 15 mJ / m ２ That is all. 20 mJ / m ２ Preferably, it is 25 mJ / m ２ It is more preferable that the surface free energy of the release layer is 20 mJ / m ２ As a result, the ceramic green sheet on the release layer is more easily held in place, and when the ceramic green sheet is applied, wound, and then unwound, the transfer of the ceramic green sheet to the slippery layer is less likely to occur, which is preferable. The definition of such a numerical range can be expressed as 15 ≤ γs a ≤ 40 (Equation 1).

[0127] 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 surface irregularities of the coating film after drying can be reduced.

[0128] The difference in surface free energy between the release layer and the slippery layer (γs a - γs b) is -20 mJ / m ２ It is preferable that it is greater than or equal to 15 mJ / m ２ It is even more preferable that the value be greater than or equal to -20 mJ / m ２ As a result, the force with which the smooth layer attracts the ceramic green sheet does not become excessively large compared to the force with which the release layer holds the ceramic green sheet. Therefore, when the ceramic green sheet is applied, wound, and then unwound, transfer of the ceramic green sheet to the smooth layer is less likely to occur, which is preferable. Furthermore, the difference in surface free energy between the release layer and the smooth layer (γs a - γs b) is 20 mJ / m ２ Preferably, the following: More preferably, 15 mJ / m ２ For example, 10 mJ / m ２ The following applies: 5 mJ / m ２ The following is even more preferable: 20 mJ / m ２ The following conditions prevent the surface free energy of the release layer from becoming too high relative to the slippery layer, ensuring sufficient release properties of the release layer and allowing the ceramic green sheet to be removed without defects. This range of values ​​can be expressed as -20 ≤ γs a - γs b ≤ 20 (Equation 3).

[0129] Preferably, the surface free energy γs b(mJ / m) of the smooth layer is 2 ) is the surface free energy γs a(mJ / m) of the release layer. 2 It is larger than ). This relationship makes it possible to suppress the transfer of the ceramic green sheet to the smooth layer when the ceramic green sheet is applied, wound, and then unwound.

[0130] (Ceramic Green Sheet and Ceramic Capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, a first internal electrode and a second internal electrode are alternately arranged along the thickness direction. The first internal electrode is exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0131] 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.

[0132] In another embodiment, the present invention provides a method for manufacturing a release film as described herein, comprising coating an unstretched or uniaxially oriented film with a slip-free layer-forming composition, and, after coating with the slip-free layer-forming composition, heat-setting the film at 80°C to 270°C in an unstretched state or after stretching at least uniaxially. For example, the release film of the present invention can be manufactured using this manufacturing method.

[0133] 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.

[0134] [NMR Measurement] The ratio of copolymer components introduced into the acrylic polyol is determined by nuclear magnetic resonance spectroscopy ( 1 H-N MR, 13 The compound was confirmed using 1C-NMR (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.

[0135] [Confirmation of Tg] The Tg of the acrylic polyol was determined from the composition ratio of the copolymer components obtained by the NMR measurement described above and from the Fox formula described above.

[0136] (1) Surface Characteristics of 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 five measurements, and the maximum protrusion height (P) was taken as the maximum value of five measurements. (Measurement conditions) ・Measurement mode: WAVE mode ・Objective lens: 50x ・0.5×Tube lens ・Measurement area: 187 × 139 μm (Sa, P measurement)

[0137] (2) Surface Free Energy Under conditions of 25°C and 50% RH, droplets of water (droplet volume 1.8 μL), diiodomethane (appropriate liquid volume 0.9 μL), and ethylene glycol (appropriate liquid volume 0.9 μL) were prepared on the release surface of the release film using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701), and the contact angles were measured. The contact angles were 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 taken as the surface free energy γs. This calculation was performed using the calculation software within the contact angle meter software (FAMAS).

[0138] (3) Measurement of peeling force of ceramic green sheet Slurry composition I, consisting of the following materials, was stirred and mixed for 10 minutes, and dispersed with zirconia beads with a diameter of 0.5 mm using a bead mill for 10 minutes to obtain a primary dispersion. Then, slurry composition II, consisting of the following materials, 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 with zirconia beads with a diameter of 0.5 mm using a bead mill 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 (Seslec BM-S, manufactured by Sekisui Chemical Co., Ltd.) 16.3 parts by mass 1-Ethyl-3-methylimidazolium ethyl sulfate 0.5 parts by mass Next, the release surface of the obtained release film sample was coated with 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 resulting ceramic green sheet-attached release film was static-eliminated 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, a peel temperature of 25°C, and a 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 the tape with the release film side adhering to the double-sided tape, and then peeled by pulling the ceramic green sheet side. From the obtained measured values, the average value of the peel force for peel distances of 20 mm to 70 mm was calculated and defined as the peel force. A total of five measurements were taken, and the average value of the peel force was adopted for evaluation. The obtained peel force values ​​were judged according to the following criteria. ◎, ○, and △ were judged to be acceptable.◎: 0.4 mN / mm or more, 0.8 mN / mm or less ○: Greater than 0.8 mN / mm, 1.2 mN / mm or less △: Greater than 1.2 mN / mm, 1.5 mN / mm or less ×: Less than 0.4 mN / mm or greater than 1.5 mN / mm, or the ceramic green sheet broke during measurement.

[0139] (4) Evaluation of pinholes and thickness variation in ceramic green sheets Slurry composition I, consisting of the following materials, was stirred and mixed for 10 minutes, and dispersed for 10 minutes using a bead mill with zirconia beads with a diameter of 0.5 mm to obtain a primary dispersion. Then, slurry composition II, consisting of the following materials, 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 for 10 minutes using a bead mill with zirconia beads with a diameter of 0.5 mm 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 (Seslec BM-S, manufactured by Sekisui Chemical Co., Ltd.) 16.3 parts by mass 1-Ethyl-3-methylimidazolium ethyl sulfate 0.5 parts by mass The slurry was applied to the release surface of the release film sample using an applicator so that the dried slurry had a thickness of 1.0 μm, dried at 60°C for 1 minute, and then the release film was peeled off to obtain a ceramic green sheet. In the central region of the film width direction of the obtained ceramic green sheet, 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 as passing. ◎: No pinholes, thickness variation is particularly good ○: No pinholes, thickness variation is not particularly problematic △: A very small number of pinholes are present, and some thickness variation is visible. ×: A few pinholes are present, and thickness variation is somewhat noticeable.

[0140] (5) Evaluation of the transferability of the ceramic green sheet Slurry composition I, consisting of the following materials, was stirred and mixed for 10 minutes, and dispersed for 10 minutes using a bead mill with zirconia beads with a diameter of 0.5 mm to obtain a primary dispersion. Then, slurry composition II, consisting of the following materials, 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 for 10 minutes using a bead mill with zirconia beads with a diameter of 0.5 mm 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 (Seslec BM-S, manufactured by Sekisui Chemical Co., Ltd.) 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 release film sample using an applicator so that the dried slurry is 1.0 μm thick, dry at 60°C for 1 minute, then place the coated slurry surface on top of the slippery layer surface of another release film and leave for 24 hours at 1 kg / cm ２ After applying the load, the film on the side with the slippery layer was slowly peeled off to check whether the slurry was transferred to the slippery layer. For release films that did not transfer under the above overlapping conditions, an additional 24 hours of 5 kg / cm² of material was applied. ２ After applying the load, the film on the side with the slippery layer was slowly peeled off, and it was checked whether the slurry was transferred to the slippery layer. Each level was evaluated three times, and if the slurry transfer was visually confirmed even once, it was judged as having been transferred. ◎ and ○ were judged as passing. ◎: 24 hours, 1 kg / cm ２ The load conditions were 24 hours, 5 kg / cm². ２ Under either of the loading conditions, the slurry did not transfer to the easily slippery surface. ○: 24 hours, 1 kg / cm ２ Under these loading conditions, the slurry did not transfer to the easily slippery surface, but at 5 kg / cm³ for 24 hours, ２ Under these loading conditions, the slurry was transferred to the easily slippery surface. ×: 24 hours, 1 kg / cm³ ２ Under these weighting conditions, the slurry was transferred to the easily slippery surface.

[0141] (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. Two tons of TPA (terephthalic acid) were used per hour, 2 moles of EG (ethylene glycol) were used per mole of TPA, and antimony trioxide was added in an amount such that the Sb atoms in the generated PET amounted to 160 ppm. These slurries were continuously supplied to the first esterification reactor of the esterification reactor and reacted at atmospheric pressure for an average residence time of 4 hours at 255°C. 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 for an average residence time of 1 hour at 260°C. Next, the reaction products from the second esterification reactor were continuously removed from the system and supplied to the third esterification reactor, and the reaction was carried out using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) at 39 MPa (400 kg / cm²). 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 0.2% by mass, 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 per calcium carbonate, were added as 10% EG slurry each and reacted at atmospheric pressure with an average residence time of 0.5 hours at 260°C. 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.

[0142] (Composition for forming a smooth layer) (Acrylic polyol resin A-1) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube, 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) were charged, and the contents of the flask were heated to 80°C while stirring. The contents of the flask were stirred for 3 hours while maintaining the temperature at 80°C, and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After purging the contents of the flask with nitrogen while raising the temperature to 120°C, the mixture was stirred at 120°C for 2 hours. Next, the pressure was reduced to 1.5 kPa at 120°C to remove unreacted raw materials and solvent, and an acrylic polyol was obtained. The flask was returned to atmospheric pressure and cooled to room temperature. 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 (A-1) with an active ingredient concentration of 20% by mass. The Tg of acrylic polyol (A-1) was 88°C, the acid value was 87 mg KOH / g, and the hydroxyl value was 87 mg KOH / g.

[0143] (Acrylic Polyol Resin A-2) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube, 103 parts by mass of methyl methacrylate (MMA), 173 parts by mass of stearyl methacrylate (SMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 22 parts by mass of methacrylic acid (MAA), and 929 parts by mass of isopropyl alcohol (IPA) were charged, and the contents of the flask were heated to 80°C while stirring. The contents of the flask were stirred for 3 hours while maintaining the temperature at 80°C, and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After purging the flask with nitrogen while raising the temperature to 120°C, the mixture was stirred at 120°C for 2 hours. Next, the pressure was reduced to 1.5 kPa at 120°C to remove unreacted raw materials and solvent, and an acrylic polyol was obtained. The flask was returned to atmospheric pressure and cooled to room temperature. 1592 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 (A-2) with an active ingredient concentration of 20% by mass. The Tg of acrylic polyol (A-2) was 73°C, the acid value was 72 mg KOH / g, and the hydroxyl value was 108 mg KOH / g.

[0144] (Acrylic Polyol Resin A-3) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, 46 parts by mass of methyl methacrylate (MMA), 52 parts by mass of stearyl methacrylate (SMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 13 parts by mass of methacrylic acid (MAA), and 493 parts by mass of isopropyl alcohol (IPA) were charged, and the contents of the flask were heated to 80°C while stirring. The contents of the flask were stirred for 3 hours while maintaining the temperature at 80°C, and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After purging the flask with nitrogen while raising the temperature to 120°C, the mixture was stirred at 120°C for 2 hours. Next, the pressure was reduced to 1.5 kPa at 120°C to remove unreacted raw materials and solvent, and an acrylic polyol was obtained. The flask was returned to atmospheric pressure and cooled to room temperature. 846 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 (A-3) with an active ingredient concentration of 20% by mass. The Tg of acrylic polyol (A-3) was 66°C, the acid value was 82 mg KOH / g, and the hydroxyl value was 204 mg KOH / g.

[0145] (Acrylic polyol resin A-4) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube, 277 parts by mass of methyl methacrylate (MMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 26 parts by mass of methacrylic acid (MAA), and 941 parts by mass of isopropyl alcohol (IPA) were charged, and the contents of the flask were heated to 80°C while stirring. The contents of the flask were stirred for 3 hours while maintaining the temperature at 80°C, and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. The contents of the flask were purged with nitrogen while the temperature of the flask was raised to 120°C, and the mixture was stirred at 120°C for 2 hours. Next, the pressure was reduced to 1.5 kPa at 120°C to remove unreacted raw materials and solvent, and an acrylic polyol was obtained. The flask was returned to atmospheric pressure and cooled to room temperature. 1614 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 (A-4) with an active ingredient concentration of 20% by mass. The Tg of acrylic polyol (A-4) was 94°C, the acid value was 86 mg KOH / g, and the hydroxyl value was 107 mg KOH / g.

[0146] (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.

[0147] (Preparation 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 placed and heated at 110°C, and the resin was dissolved by stirring. 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 produce a milky white polyester aqueous dispersion (B-1) with an active ingredient content of 30% by mass.

[0148] (Polymerization of polyester resin B0-2) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 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 were charged, and a transesterification reaction was carried out from 160°C to 220°C over 4 hours. 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 an esterification reaction. Next, the temperature was raised to 255°C, the reaction system was gradually reduced in pressure, and the reaction was carried out under a 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.

[0149] (Production 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. Next, a solution of 16 parts by mass of styrene and 1.5 parts by mass of azobisdimethylvaleronitrile dissolved 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 for analysis from the reaction solution, 8 parts by mass of methanol was added. Next, 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. 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. A homogeneous, water-dispersible polyester graft copolymer dispersion (B-2) with an active ingredient concentration of 25% by mass was then prepared. The glass transition temperature of the obtained polyester graft copolymer was 68°C.

[0150] (Preparation of Oxazoline Crosslinking Agent C-1) 460.6 parts of isopropyl alcohol were charged into a flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer, and heated to 80°C while slowly flowing nitrogen gas. A monomer mixture consisting of 126 parts methyl methacrylate, 210 parts 2-isopropenyl-2-oxazoline, and 84 parts methoxypolyethylene glycol acrylate, which had been prepared in advance, 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 reaction to proceed, and the reaction was continued for 5 hours after the dropwise addition was completed. 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 (C-1) having oxazoline groups with an active ingredient concentration of 25%. The amount of oxazoline groups in the obtained resin (C-1) containing oxazoline groups was 4.3 mmol / g, and the number-average molecular weight measured by GPC (gel permeation chromatography) was 20,000.

[0151] (Preparation of Oxazoline Crosslinking Agent C-2) Using the same method as in the synthesis of the oxazoline group-containing resin (C-1) described above, an oxazoline group-containing resin (C-2) with a different composition (oxazoline group amount and molecular weight) and an active ingredient concentration of 10% was obtained. The amount of oxazoline groups in the obtained oxazoline group-containing resin (C-2) was 7.7 mmol / g, and the number average molecular weight measured by GPC was 40,000.

[0152] (Preparation of Carbodiimide Crosslinking Agent D-1) 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were charged into a flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was stirred at 120°C for 1 hour. Then, 26 parts by mass of 4,4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphoren-1-oxide (2% by mass relative to the total isocyanate) were added as a carbodiimide catalyst, and the mixture was stirred at 185°C under a nitrogen stream for a further 5 hours. The infrared spectrum of the reaction solution was measured, with wavelengths of 2200-2300 cm. －１It was confirmed that the absorption had disappeared. The mixture was allowed to cool to 60°C, and 567 parts by mass of deionized water was added to obtain a carbodiimide water-soluble resin (D-1) with an active ingredient content of 40% by mass.

[0153] (Acrylic Particles E-1) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX100W, average particle size 150 nm, active ingredient concentration 10% by mass) (Acrylic Particles E-2) Acrylic particle aqueous dispersion (manufactured by Nippon Shokubai, product name MX300W, average particle size 450 nm, active ingredient concentration 10% by mass)

[0154] (Composition for forming a release layer) (Long-chain alkyl group-containing acrylic resin G-1) Lauryl methacrylate (CH ２ = C(CH ３ ) COOC １２ H ２５ ), hydroxyethyl methacrylate (CH ２ = C(CH ３ ) COOC ２ H ４ Mixing OH) in a ratio of 77:23, adding toluene to achieve an active ingredient concentration of 25% by weight, and copolymerizing under a nitrogen atmosphere by adding 0.5 mol% azobisisobutyronitrile (AIBN) to obtain a long-chain alkyl group-containing acrylic resin (G-1).

[0155] (Long-chain alkyl group-containing acrylic resin G-2) Lauryl methacrylate (CH ２ = C(CH ３ ) COOC １２ H ２５ ), hydroxyethyl methacrylate (CH ２ = C(CH ３ ) COOC ２ H ４ Mixing OH) in a ratio of 88:12, adding toluene to achieve an active ingredient concentration of 25% by weight, and copolymerizing under a nitrogen atmosphere by adding 0.5 mol% azobisisobutyronitrile (AIBN) to obtain a long-chain alkyl group-containing acrylic resin (G-2).

[0156] (Long-chain alkyl group-containing acrylic resin G-3) Lauryl methacrylate (CH ２ = C(CH ３ ) COOC １２ H ２５) were mixed in a ratio of 100, toluene was added so that the active ingredient concentration became 25% by weight, 0.5 mol% of azobisisobutyronitrile (AIBN) was added under a nitrogen stream, and copolymerization was carried out to obtain a long-chain alkyl group-containing acrylic resin (G-3).

[0157] (Long-chain alkyl group-containing acrylic resin G-4) Hydroxyethyl methacrylate (CH ２ =C(CH ３ )COOC ２ OH), methyl methacrylate (CH ４ =C(CH ２ )COOC ３ )COOC ３ H ３ ), butyl methacrylate (CH ２ =C(CH ３ )COOC ４ H ９ ) were mixed in a ratio of 23:24:53, toluene was added so that the active ingredient concentration became 25% by weight, 0.5 mol% of azobisisobutyronitrile (AIBN) was added under a nitrogen stream, and copolymerization was carried out to obtain a long-chain alkyl group-containing acrylic resin (G-4).

[0158] (Resin H-1) Heat / UV curable silicone resin (LTC856, manufactured by Dow Corning Toray Co., Ltd.)

[0159] (Melamine Compound I-1) Melamine compound (manufactured by Nippon Carbide Industries Co., Inc., MW-30M, melamine resin, full ether type, active ingredient concentration: 100% by mass) (Melamine Compound I-2) Melamine compound (manufactured by Nippon Carbide Industries Co., Inc., MS-11, melamine resin, methylol type, active ingredient concentration: 60% by mass)

[0160] (Polyol J-1) Hydrogenated dimer diol: product name "Pripol 2033", manufactured by Croda Japan Co., Ltd., number average molecular weight: 540, active ingredient: 100% (Polyol J-2) Cyclohexanedimethanol (manufactured by Tokyo Chemical Industry Co., Ltd., cyclohexanedimethanol, CHDM), active ingredient: 100%

[0161] (Catalyst K-1) Paratoluenesulfonic acid, manufactured by Hitachi Chemical Polymer Co., Ltd., Dryer #900, active ingredient concentration 50% by mass (Catalyst K-2) Platinum catalyst (manufactured by Toray Dow Corning, Inc., SRX212), active ingredient concentration 50% by mass

[0162] (Additive L-1) Terminally carboxyl-modified polydimethylsiloxane, X22-3710, active ingredient concentration 100%, manufactured by Shin-Etsu Chemical Co., Ltd.

[0163] (Example 1) (Production of Laminated Film) As the 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 a reduced pressure of 133 Pa. Thereafter, the pellets were fed into an extruder and melt-extruded into a sheet at approximately 280°C, and rapidly cooled and solidified on a rotating cooling metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

[0164] 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.

[0165] Next, the following slip-free layer-forming composition 1 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 with a slip-free layer with a thickness of 31 μm. (Composition 1 for forming a smooth surface) Water 39.62 parts by mass Isopropyl alcohol 35.00 parts by mass Acrylic polyol resin A-1 (active ingredient concentration 20% by mass) 16.57 parts by mass Oxazoline crosslinking agent C-1 (active ingredient concentration 25% by mass) 5.68 parts by mass Acrylic particles E-1 2.37 parts by mass (average particle size 150 nm, active ingredient concentration 10% by mass) Acrylic particles E-2 0.47 parts by mass (average particle size 450 nm, active ingredient concentration 10% by mass) Surfactant F-1 (silicone-based, active ingredient concentration 10% by mass) 0.30 parts by mass

[0166] (Formation of release layer) The release layer forming composition 1 described below was applied to the side of the polyester film with a smooth-slip layer opposite to the side where the smooth-slip layer was formed, using a reverse gravure coater, so that the thickness after drying was 0.150 μm. Then, it was dried and cured with hot air at 140°C for 30 seconds to obtain a release film with a laminated smooth-slip layer. (Release layer forming composition 1, MEK / toluene = 50 / 50, active ingredient concentration 4.62%) MEK 46.932 parts by mass Toluene 46.932 parts by mass Long-chain alkyl group-containing acrylic resin G-1 (active ingredient concentration 100% by mass) 1.774 parts by mass Melamine compound I-1 (active ingredient concentration 100% by mass) 1.774 parts by mass Polyol J-1 (active ingredient concentration 100% by mass) 2.218 parts by mass Acid catalyst K-1 (Dryer #900, active ingredient concentration 50% by mass) 0.370 parts by mass

[0167] (Examples 2-21, Comparative Examples 1-7) Release films were obtained using the same procedure as in Example 1, except that the composition numbers of the smooth-slip layer, the composition numbers of the release layer, and the ratio of active ingredients of each component were changed to the conditions in Tables 1 and 2.

[0168] Tables 1, 2, and 3 show the composition details and evaluation results for each example and comparative example.

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175] In the tables and text, "active ingredient" refers to the main component of each material, and "active ingredient concentration" refers to the concentration of the main component of each material. In the case of compositions for forming a smooth layer or a release layer, "active ingredient" refers to the main component of the entire material, and "active ingredient concentration" refers to the concentration of the main component of the entire material. The main component may be solid or liquid.

[0176] Table 1 above shows the ratio of active ingredients of resin, crosslinking agent, particles, and surfactant in the composition for forming a smooth layer. These ratios represent the mass ratio of each active ingredient when the total active ingredients of the resin and crosslinking agent are set to 100% by mass.

[0177] Table 1 above shows the ratio of active ingredients of resin, crosslinking agent, polyol, catalyst, and silicone additive in the release layer forming composition. These ratios represent the mass ratio of each active ingredient when the total amount of active ingredients of the resin, crosslinking agent, polyol, catalyst, and silicone additive is set to 100% by mass.

[0178] 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.

[0179] The object of the present invention is to provide a release film that has good release properties and suppresses the transfer of ceramic green sheets, even when resin sheets such as ceramic green sheets are made into thin films. In Examples 1 to 21, by adjusting the surface free energy of the smooth layer, the surface free energy of the release layer, and the difference between the two to a desired range, it was possible to suppress the transfer of ceramic green sheets to the smooth surface, making it possible to produce high-quality ceramic capacitors without reducing the yield of ceramic capacitors. On the other hand, in Comparative Examples 1, 2, 3, and 4, since a material with high surface free energy was used for the smooth layer, it is thought that the smooth layer and the ceramic green sheet blocked each other, resulting in the transfer of ceramic green sheets to the smooth layer. In Comparative Examples 5 and 6, the surface free energy on the release layer side was high, and the peeling force of the ceramic green sheet increased, so it is thought that the sheet was more likely to be damaged during peeling. In Comparative Example 7, by providing a release layer with low surface free energy, (γS a - γS b) fell below the desired range, so it is thought that the force with which the release layer holds the ceramic green sheet weakened, resulting in the transfer of ceramic green sheets to the smooth layer.

[0180] According to the present invention, it is possible to provide a release film that has good release properties and suppresses transfer of ceramic green sheets, even when resin sheets such as ceramic green sheets are made into thin films. Furthermore, by using the release film for manufacturing ceramic green sheets of the present invention, ultra-thin ceramic green sheets can be obtained, and minute ceramic capacitors can be manufactured efficiently.

Claims

1. The material comprises a smooth-slip layer containing particles, a polyester film substrate, and a release layer in this order, wherein the surface free energy of the release layer is γs a(mJ / m 2 ) and the surface free energy γs b(mJ / m) of the slippery layer 2 A release film that satisfies the following equations 1, 2, and 3: (Equation 1) 15 ≤ γs a ≤ 40 (Equation 2) 25 ≤ γs b ≤ 45 (Equation 3) - 20 ≤ γs a - γs b ≤ 20 2. The release film according to claim 1, wherein the polyester film substrate is a polyester film substrate that substantially does not contain inorganic particles.

3. The release film according to claim 1, wherein the average surface roughness (Sa) of the release layer region is 0.1 nm or more and 30 nm or less, and the maximum protrusion height (P) is 0.1 nm or more and 500 nm or less.

4. The release film according to claim 1, wherein the average surface roughness (Sa) of the smooth-slip layer 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.

5. The release film according to claim 1, wherein the smooth layer is formed by curing a composition containing an acrylic resin containing a long-chain alkyl group and at least one crosslinking agent selected from oxazoline-based crosslinking agents or carbodiimide-based crosslinking agents.

6. The release film according to claim 1, wherein the release layer is formed by curing a composition containing an acrylic resin containing a long-chain alkyl group and a melamine compound.

7. The release film according to claim 5, wherein the resin containing the long-chain alkyl group is an acrylic resin, and the acrylic resin contains at least component A-1 represented by the following chemical formula (Chemical Formula 1). In formula (1), R １ is (CnH2n+1) (n = an integer between 8 and 20), R ４ is H or CH ３ This indicates.

8. The release film according to claim 1, wherein the release film is a release film for manufacturing ceramic green sheets.

9. A method for manufacturing a release film according to claim 1, comprising: coating an unstretched film or a uniaxially oriented film with a slip-free layer forming composition; and, after coating the film with the slip-free layer forming composition, heat-setting the film at 80°C to 270°C in an unstretched state or after stretching it at least uniaxially.

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