Silicone release polyester film and its manufacturing method

Abstract

The present invention provides: a silicone release polyester film which is suitable for use as a carrier film during the production of a multilayer ceramic capacitor and the like, and which exhibits excellent adhesion and excellent releasability suitable for sheet molding ranging from easy separation to uneasy separation; and a method for producing this silicone release polyester film.　The present invention provides a silicone release polyester film which has, on at least one surface of a polyester film, a coating layer that is formed using a coating composition for mold release, the coating composition containing an aqueous dispersion (1) of one or more silicones (A) that each contain an alkenyl group and / or a Q unit represented by SiO4 / 2, an aqueous dispersion (2) of a silicone (B) that has a hydrogen atom directly bonded to an Si atom as represented by an Si-H group, a crosslinking reaction inhibitor, a platinum-based catalyst and a nonionic emulsifying agent. With respect to this silicone release polyester film, the number average molecular weight of the silicones A is 150,000 or more; and the content of Si atoms in the Q unit is 0.05% by mole to 60% by mole.

Description

[Technical Field]

[0001] The present invention relates to a silicone release polyester film, and more specifically to a silicone release polyester film that has releasability and adhesion suitable for molding, ranging from light to heavy release, into ceramic green sheets used in the production of multilayer ceramic capacitors, and that can prevent tearing or deformation of the sheets, as well as a method for producing the same. [Background technology]

[0002] Release films are used as carrier films for molding resin and ceramic sheets. Polyester film is often used as the base material for release films, particularly for its dimensional stability and heat resistance. In recent years, ceramic green sheets have been manufactured in a wide variety of thicknesses, particularly with the trend toward miniaturization and high reliability of multilayer ceramic capacitors. Therefore, carrier films are required to have various properties suited to the thickness of the slurry. In the production of multilayer ceramic capacitors, thinning ceramic green sheets reduces their rigidity, leading to tearing during peeling, so easy peeling is required. Furthermore, relatively thick green sheets have high rigidity, which can cause lifting between the sheet and the release film during processing, resulting in sheet deformation. Thus, ceramic sheet peeling requires a variety of peel strengths, ranging from light to heavy. Furthermore, regardless of the thickness of the green sheet, even slight defects in the ceramic slurry coating can penetrate the sheet, resulting in pinholes and thickness variations, significantly reducing the yield of multilayer ceramic capacitors. Therefore, uniformity of the release layer coating on the release film is essential.

[0003] In response to these problems, it has been proposed to add a component made of a silicone resin having a trifunctional unit siloxane or tetrafunctional unit siloxane structure (see, for example, Patent Document 1), but the specific content of the silicone resin is not disclosed, and there is no mention of emulsion-type release agents.

[0004] Furthermore, an aqueous coating composition containing a silicone containing Q units in a specified range of mole percent and a silicone having Si-H groups has been described (see, for example, Patent Document 2), but the optimum molecular weight range of the silicone containing Q units is not particularly described. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-1527 [Patent Document 2] Patent Publication No. 2021-11081 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, the present invention aims to provide a silicone release polyester film that has excellent release and adhesion properties suitable for sheet molding with light to heavy release properties, and that can be suitably used, for example, as a carrier film in the production of multilayer ceramic capacitors, and a method for producing the same. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have discovered that, under certain specific conditions, even when emulsion-type silicone is used, it is possible to provide a release film or the like that has an appropriate release force, ranging from light to heavy release, and have thereby completed the present invention.

[0008] That is, the present invention provides the following silicone release polyester film (silicone releaseable polyester film).

[0009] [1] At least one surface of the polyester film is provided with an alkenyl group and / or SiO 4 / 2a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: (A) a water dispersion (2) of a silicone (B) having a hydrogen atom directly bonded to a Si atom represented by a Si-H group; a crosslinking reaction inhibitor; a platinum-based catalyst; and a nonionic emulsifier; The number average molecular weight of the silicone A is 150,000 or more, The content of Si atoms contained in the Q units is 0.05 mol % or more and 60 mol % or less. Silicone release polyester film.

[0010] [2] The silicone release polyester film according to [1], wherein the content of the silicone (B) is 3 parts by mass or more and 45 parts by mass or less, when the total content of the silicone (A) and the silicone (B) is 100 parts by mass.

[0011] [3] The silicone release polyester film according to [1] or [2], wherein the alkenyl group of the silicone (A) is a vinyl group.

[0012] [4] The silicone release polyester film according to any one of [1] to [3], which has a peel strength after being attached to a polyester adhesive tape of 20 g / 25 mm width or more and 400 g / 25 mm width or less.

[0013] [5] The silicone release polyester film according to any one of [1] to [4], which is used for forming ceramic green sheets in the production of multilayer ceramic capacitors.

[0014] The present invention also provides the following method for producing a silicone release polyester film.

[0015] [6] At least one surface of the polyester film is provided with an alkenyl group and / or SiO 4 / 2a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: (A) (B) (C) (D) (E) (F) (H ... (F)) (F)) (F)) (F)) (F)) (F)) (F)) The number average molecular weight of the silicone A is 150,000 or more, The content of Si atoms contained in the Q units is in the range of 0.05 mol % or more and 60 mol % or less. Method for producing silicone release polyester film.

[0016] [7] The manufacturing method according to [6], wherein the content of the silicone (B) is 3 parts by mass or more and 45 parts by mass or less, when the total content of the silicone (A) and the silicone (B) is 100 parts by mass.

[0017] [8] The method according to [6] or [7], wherein the alkenyl group of the silicone (A) is a vinyl group. [Effects of the Invention]

[0018] By having the above-described configuration, the silicone release polyester film of the present invention can be used as a release film for sheet molding, having a peel strength suitable for sheet molding of the thickness of ceramic green sheets, etc., and moderate releasability with little sheet deformation, thereby enabling the production of sheets with reduced defect rates and high reliability.

[0019] Furthermore, the method for producing a silicone release polyester film of the present invention makes it possible to efficiently and easily obtain a silicone release polyester film having the above-mentioned properties. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0021] <Silicone release polyester film> The silicone release polyester film of the present invention is At least one surface of the polyester film is provided with an alkenyl group and / or SiO 4 / 2 a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: (A) a water dispersion (2) of a silicone (B) having a hydrogen atom directly bonded to a Si atom represented by a Si-H group; a crosslinking reaction inhibitor; a platinum-based catalyst; and a nonionic emulsifier; The number average molecular weight of the silicone A is 150,000 or more, The content of Si atoms contained in the Q units is 0.05 mol % or more and 60 mol % or less.

[0022] [Polyester film] For the polyester film of the present invention, any known polyester can be used as appropriate, and for example, the following polyesters can be suitably used.

[0023] (polyester) The polyester constituting the polyester film used as the base film (hereinafter sometimes referred to as "base material") in the present invention is not particularly limited, and a film of a polyester commonly used as a base material for release films can be used. Preferred are crystalline linear saturated polyesters composed of an aromatic dibasic acid component and a diol component. For example, polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate), polytrimethylene terephthalate, or copolymers primarily composed of these resin components are more preferred. Of these, polyester films formed from polyethylene terephthalate are particularly preferred. The polyethylene terephthalate preferably contains 90 mol % or more, more preferably 95 mol % or more, of ethylene terephthalate repeating units, and may contain small amounts of other dicarboxylic acid components or diol components copolymerized therein. For example, from the standpoint of cost, those produced solely from terephthalic acid and ethylene glycol are preferred.

[0024] Furthermore, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, crystallizing agents, etc. may be added within a range that does not impair the effects of the release film of the present invention. The polyester film is preferably a biaxially oriented polyester film because of its high bidirectional elastic modulus.

[0025] The intrinsic viscosity of the polyester film is preferably 0.50 dL / g or more and 0.70 dL / g or less, more preferably 0.52 dL / g or more and 0.65 dL / g or less. An intrinsic viscosity of 0.50 dL / g or more is preferred because breakage does not occur frequently during the stretching process. Conversely, an intrinsic viscosity of 0.70 dL / g or less is preferred because cuttability when cutting to a predetermined product width is good and dimensional defects do not occur. It is also preferred that the raw material pellets are thoroughly vacuum dried.

[0026] In this specification, when simply referring to a "polyester film", it means a polyester film having (laminated with) a surface layer A and a surface layer B.

[0027] The method for producing the polyester film of the present invention is not particularly limited, and any conventionally commonly used method can be used. For example, the polyester can be melted in an extruder, extruded into a film, and cooled on a rotating cooling drum to obtain an unstretched film, which can then be biaxially stretched. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0028] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition point (Tg) of the polyester, and the stretching is preferably 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0029] The polyester film preferably has a thickness of 12 μm or more and 100 μm or less, more preferably 16 μm or more and 50 μm or less, and even more preferably 19 μm or more and 33 μm or less. A film thickness of 12 μm or more is preferable because there is no risk of deformation due to heat during film production, processing, or molding. On the other hand, a film thickness of 100 μm or less is preferable in terms of reducing the amount of film discarded after use and reducing the environmental impact.

[0030] The polyester film substrate may be a single layer or a multilayer structure of two or more layers. For example, the substrate film may be a polyester film having a surface layer A that is substantially free of particles having a particle size of 1.0 μm or more and a surface layer B that contains particles. Preferably, the surface layer A is substantially free of inorganic particles having a particle size of 1.0 μm or more.

[0031] In this embodiment, particles having a particle size of less than 1.0 μm and 1 nm or more may be present in the surface layer A. By making the surface layer A substantially free of particles having a particle size of 1.0 μm or more, such as inorganic particles, it is possible to reduce defects caused by the shape of particles in the substrate being transferred to the resin sheet.

[0032] In one embodiment, the surface layer A does not contain particles with a particle size of less than 1.0 μm, so that problems caused by the shape of particles in the substrate being transferred to the resin sheet can be more effectively prevented.

[0033] In one embodiment, the polyester film substrate is preferably a laminate film having a surface layer A substantially free of inorganic particles on at least one side, which more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet.

[0034] For example, a preferred embodiment is that the surface layer A that does not substantially contain particles with a particle size of less than 1.0 μm also does not substantially contain particles with a particle size of 1.0 μm or more.

[0035] In the present invention, "substantially free of particles" means, for example, in the case of inorganic particles less than 1.0 μm in size, that the content of inorganic elements quantified by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if particles are not actively added to the film, contaminants from foreign substances or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may peel off and be mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or more" means that particles with a particle size of 1.0 μm or more are not actively included.

[0036] In the case of a laminated polyester film having a multi-layer structure of two or more layers, it is preferable that a surface layer B that can contain inorganic particles or the like is provided on the surface opposite to a surface layer A that does not substantially contain inorganic particles.

[0037] In terms of the laminate structure, if the layer on the side to which the release layer is applied is Layer A, the layer on the opposite side is Layer B, and the other core layer is Layer C, the layer structure in the thickness direction can be a laminate structure such as release layer / A / B or release layer / A / C / B. Naturally, Layer C may be a multi-layer structure. Furthermore, surface layer B may not contain inorganic particles. In that case, it is preferable to provide a coating layer containing at least inorganic particles and a binder on surface layer B to impart slip properties for winding the film into a roll.

[0038] In the polyester film substrate of the present invention, the surface layer B, which forms the surface opposite to the surface to which the release layer is applied, preferably contains inorganic particles, particularly silica particles and / or calcium carbonate particles, from the viewpoint of the slipperiness of the film and ease of air escape. The content of the inorganic particles contained in the surface layer B is preferably 5,000 ppm or more and 15,000 ppm or less in total.

[0039] In this case, the area surface average roughness (Sa) of the film of surface layer B is preferably in the range of 1 nm to 40 nm, more preferably in the range of 5 nm to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5,000 ppm or more and Sa is 1 nm or more, air can be uniformly released when the film is wound into a roll, resulting in a good wound shape and good flatness, making it suitable for producing ultrathin ceramic green sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15,000 ppm or less and Sa is 40 nm or less, the lubricant is less likely to aggregate and large protrusions are not formed, which is preferable because it ensures stable quality when producing ultrathin ceramic green sheets.

[0040] The particles contained in Layer B may be inert inorganic particles and / or heat-resistant organic particles other than silica and / or calcium carbonate. However, from the viewpoints of transparency and cost, it is more preferable to use silica particles and / or calcium carbonate particles. Other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferred. When calcium carbonate particles are used, light calcium carbonate that has been surface-treated with a polyacrylic acid-based polymer compound is preferred from the viewpoint of preventing the lubricant from falling off.

[0041] The average particle size of the inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.3 μm or more and 1.0 μm or less. If the average particle size of the inorganic particles is 0.1 μm or more, the slipperiness of the release film is good, which is preferable. Furthermore, if the average particle size is 2.0 μm or less, there is no risk of adversely affecting the smoothness of the release layer surface, and there is no risk of pinholes occurring in the ceramic green sheet, which is preferable.

[0042] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, or to prevent static electricity, a coating layer may be provided on the surface of the surface layer A and / or the surface layer B before stretching or after uniaxial stretching in the film-forming process, and corona treatment or the like may also be performed.

[0043] Furthermore, the silicone release polyester film of the present invention can have a peel strength of 20 g / 25 mm width or more and 400 g / 25 mm width or less after being attached to a polyester adhesive tape. The lower limit of the peel strength can be, for example, 30 g / 25 mm width or more, 40 g / 25 mm width or more, 50 g / 25 mm width or more, 70 g / 25 mm width or more, 100 g / 25 mm width or more, 120 g / 25 mm width or more, 150 g / 25 mm width or more, 180 g / 25 mm width or more, etc. The upper limit of the peel strength can be, for example, 380 g / 25 mm width or less, 350 g / 25 mm width or less, 330 g / 25 mm width or less, 300 g / 25 mm width or less, 280 g / 25 mm width or less, 250 g / 25 mm width or less, 230 g / 25 mm width or less, 200 g / 25 mm width or less, etc. The above peel strength is preferably 20 g / 25 mm or more and 400 g / 25 mm or less. Because the silicone release polyester film of the present invention has the above configuration, for example, by introducing a silicone resin (Q unit resin) into the silicone main component (silicone A), it is possible to provide a release film with appropriate hardness for use in sheet formation even when a small amount of crosslinking agent is used, and in addition, the release force can be controlled from light to heavy by adjusting the amount of crosslinking agent added, making it of extremely high industrial value.

[0044] In the present invention, the adhesive tape peel strength refers to the strength obtained by laminating a polyester adhesive tape (Nitto Denko Corporation, No. 31B) to the surface of the coating layer (release layer) of a release film, pressing it with a 5 kg pressure roller, leaving it for 30 minutes or more, and then measuring the peel strength between the release layer and the adhesive tape (peel angle 180 degrees, peel speed 300 mm / min, unit: g / 25 mm width) with a peel strength tester.

[0045] [Release Coating Composition] The release coating composition of the present invention contains an alkenyl group and / or SiO 4 / 2 The composition comprises an aqueous dispersion (1) of one or more silicones (A) containing Q units represented by the following formula: an aqueous dispersion (2) of a silicone (B) having a hydrogen atom directly bonded to a Si atom represented by a Si-H group; a crosslinking reaction inhibitor; a platinum-based catalyst; and a nonionic emulsifier.

[0046] (Alkenyl group and / or SiO 4 / 2 (A) one or more silicones containing Q units represented by The alkenyl group and / or SiO 4 / 2 An example of the silicone (A) containing Q units represented by the formula (hereinafter may be simply referred to as "Q units") is organopolysiloxane (hereinafter may be referred to as "silicone (A)") having the following general formula (I): R 1 a R 2 b SiO (4-a-b) / 2 (I) (In formula (I), R 1 is an alkenyl group having 2 to 8 carbon atoms, R 2 represents a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from alkyl groups or aryl groups, a represents an integer of 0 to 3, and b represents an integer of 0 to 3, and a+b≦3.

[0047] R 1 Examples of the alkenyl group having 2 to 8 carbon atoms represented by the formula (I) include a vinyl group, an allyl group, a butenyl group, a pentenyl group, and a hexenyl group, and among these, a vinyl group is particularly preferred. 2 Examples of the alkyl group represented by the formula (I) include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group represented by the formula (I) include a phenyl group and a tolyl group. 2 It is preferable that 50 mol % or more of the substituents are methyl groups in terms of easy peeling properties.

[0048] The silicone (A) containing alkenyl groups and / or Q units must contain Q units. However, when multiple types of silicone (A) containing alkenyl groups and / or Q units are contained, it is sufficient that any one of them contains Q units. The inclusion of Q units in the silicone-based release layer increases the coating hardness of the silicone-based release layer, reducing viscosity loss during sheet peeling, leading to easier peeling. Furthermore, the inclusion of a silicone containing Q units in the alkenyl group-containing silicone improves wettability, thereby reducing pinhole defects during sheet coating. The content of Si atoms contained in Q units is 0.05 mol% to 60 mol%, preferably 0.1 mol% to 55 mol%, and more preferably 1.0 mol% to 50 mol%, based on the total Si atoms in the silicone (A) containing alkenyl groups and / or Q units. If the content of Si atoms in the Q units is less than 0.05 mol%, sufficient coating hardness cannot be achieved, which does not lead to light peeling. If it exceeds 60 mol%, excessive wettability is imparted, resulting in strong adhesion to the sheet, which ultimately causes cohesive failure of the sheet surface (excessively heavy peeling).

[0049] The number average molecular weight of the silicone (A) containing alkenyl groups and / or Q units is preferably 150,000 or more, for example, 180,000 or more, 200,000 or more, or 220,000 or more. The number average molecular weight of the silicone (A) containing alkenyl groups and / or Q units can be, for example, 1,000,000 or less, and can be 900,000 or less, 800,000 or less, 700,000 or less, 600,000 or less, 500,000 or less, or 400,000 or less. If the number average molecular weight is less than 150,000, the amount of crosslinking agent will be insufficient to form crosslinks in the release coating film, and viscosity loss during sheet peeling cannot be suppressed, resulting in excessively heavy peeling and an increased amount of silicone transferred to the adherend.

[0050] The silicone (A) containing alkenyl groups and / or Q units of the present invention can be produced by known methods. The silicone (A) containing alkenyl groups and / or Q units of the present invention is preferably contained in the composition in the form of an aqueous dispersion (aqueous dispersion (1)).

[0051] When the silicone (A) containing alkenyl groups and / or Q units is prepared into an aqueous dispersion (aqueous dispersion (1)), the mass % of the silicone (A) containing alkenyl groups and / or Q units in the aqueous dispersion (1) can be, for example, 1 mass % or more and 50 mass % or less, such as 3 mass % or more and 40 mass % or less, 5 mass % or more and 30 mass % or less, or 10 mass % or more and 20 mass % or less.

[0052] (Silicone (B) having a hydrogen atom directly bonded to a Si atom represented by an Si-H group) In the present invention, the silicone (B) having a hydrogen atom directly bonded to a Si atom represented by a Si-H group (hereinafter, sometimes referred to as "silicone (B)" or "Si-H group-containing silicone (B)") is exemplified by organohydrogenpolysiloxanes having a structure represented by the following general formula (II): R 3 c H d SiO (4-c-d) / 2 (II) (In formula (II), R 3 represents a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, c represents an integer of 0 to 2, and d represents an integer of 1 to 3, and c+d≦3.

[0053] R 3 Examples of the alkyl group represented by the formula (I) include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group represented by the formula (I) include a phenyl group and a tolyl group. 3 It is preferable that 50 mol % or more of the substituents are methyl groups in terms of easy peeling properties.

[0054] From the viewpoint of curing properties, the Si—H group-containing silicone (B) preferably has at least three, and more preferably five or more, hydrogen atoms bonded to Si atoms in one molecule of the silicone.

[0055] The Si-H group-containing silicone (B) can be produced by known methods. The Si-H group-containing silicone (B) of the present invention is preferably contained in the composition in the form of an aqueous dispersion (aqueous dispersion (2)).

[0056] When the Si—H group-containing silicone (B) is prepared into an aqueous dispersion (aqueous dispersion (2)), the mass % of the Si—H group-containing silicone (B) in the aqueous dispersion (2) can be, for example, from 1 to 50 mass %, or may be from 3 to 40 mass %, from 5 to 30 mass %, or from 10 to 20 mass %, etc.

[0057] The content of the Si-H group-containing silicone (B) is determined by the amount of alkenyl groups and / or SiO 4 / 2 When the total content of the silicone (A) containing Q units represented by the formula (I) and the Si-H group-containing silicone (B) is taken as 100 parts by mass, the content is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, and even more preferably 3 parts by mass or more and 45 parts by mass or less. If the content is less than 1 part by mass, the curing reaction does not proceed easily, and sufficient coating hardness may not be obtained. If the content exceeds 60 parts by mass, Si-H may precipitate excessively on the surface, resulting in strong adhesion to the green sheet, which may result in severe peeling.

[0058] (Silicone content) In the release coating composition of the present invention, the amount of alkenyl groups and / or SiO 2 is determined based on the solid content mass of the composition. 4 / 2The total solid content of the silicone (A) containing Q units represented by the formula (I) and the Si-H group-containing silicone (B) is preferably 70% by mass or more. The content of each silicone solid content is more preferably 80% by mass or more and 97% by mass or less. Here, the silicone solid content refers to the amount excluding the aqueous solvent, and the solid content mass of the composition refers to the total amount of the solid content of each additive. If the total silicone solid content is less than the lower limit, the area covered by the silicone on the film surface on which the coating is formed will be smaller, resulting in a heavier release force and possibly uneven release force.

[0059] (aqueous solvent) Water is preferably used as the aqueous solvent for forming each of the silicone aqueous dispersions of the present invention. By using an aqueous solvent, it is possible to form a silicone release layer without using explosion-proof equipment and organic solvent recovery equipment, which are required for organic solvents during the process of producing a release film.

[0060] (nonionic emulsifier) Each aqueous dispersion is prepared using a nonionic emulsifier to increase the stability and shear resistance of the aqueous dispersion. After extensive research, the inventors discovered that a nonionic emulsifier is necessary to prevent aggregation of each aqueous dispersion and to avoid affecting the silicone curing reaction. Cationic emulsifiers affect the silicone curing reaction and can become localized in the coating film, for example, by bleeding out to the surface, affecting release properties and resulting in heavy peeling. Furthermore, although the details are unclear, the use of cationic emulsifiers makes it easier for silicone-based aqueous dispersions to aggregate.

[0061] The nonionic emulsifier preferably has an HLB value in the range of 6 to 18, and examples thereof include at least one selected from alkylene oxide adducts such as alkylene oxide adducts of higher alcohols or higher fatty acids, esters of alkylene oxide adducts of higher fatty acids and alcohols, alkylene oxide adducts of alkanolamides, alkylene oxide adducts of sorbitan esters, and alkylene oxide adducts of higher fatty acid glycerides. These may be used alone or in combination of two or more. The HLB value is a value calculated by Griffin's formula.

[0062] Examples of alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide. These may be used alone or in combination. When using multiple alkylene oxides, whether block or random addition is preferred, the HLB value is preferably in the range of 6 to 18, and more preferably 10 to 15. Among these nonionic emulsifiers, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, and the like are preferred. If a nonionic emulsifier with an HLB value outside the above range is used as an emulsifier for a silicone aqueous dispersion, the emulsifying and dispersing power and stability of the aqueous dispersion may decrease. The nonionic emulsifier is preferably used in a range of 0.1 to 20% by mass, more preferably 0.2 to 15% by mass, and even more preferably 0.5 to 10% by mass, based on the total solids content. If the amount is less than this range, emulsification tends to be poor, while if it is greater, severe peeling may occur.

[0063] (Platinum catalyst) The release coating composition constituting the coating layer of the present invention requires the use of a platinum-based catalyst to cause an addition reaction between one or more types of silicone (A) containing alkenyl groups and / or Q units and the Si-H group-containing silicone (B).

[0064] Known platinum catalysts can be used, such as platinum chloride and chloroplatinic acid. Taking into consideration dispersibility in silicone, the platinum catalyst may be a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex (Karstedt catalyst), which can be dispersed simultaneously with the silicone emulsification to ensure uniform dispersion. These catalysts may be used alone or in combination of two or more.

[0065] The amount of platinum catalyst is preferably in the range of 10 ppm to 800 ppm by mass of elemental platinum relative to 100 parts by mass of the combined total of the aqueous dispersion (1) of one or more silicones (A) containing alkenyl groups and / or Q units, and the aqueous dispersion (2) of the Si-H group-containing silicone (B). By adjusting the amount within this range, sufficient curing of the silicone can be achieved. Furthermore, the generation of silicone aggregates can be suppressed, resulting in a release polyester film with excellent surface properties. If the mass ratio of the platinum element exceeds the upper limit, the addition reaction between the alkenyl groups and the Si-H groups is accelerated, tending to generate silicone aggregates. From the above perspectives, the amount of platinum catalyst is more preferably 600 ppm or less, even more preferably 500 ppm or less, particularly preferably 200 ppm or less, and extremely preferably 150 ppm or less. Furthermore, if the mass ratio of the platinum element is below the lower limit, the addition reaction does not proceed, tending to result in poor curing of the silicone. From the above viewpoint, the amount of platinum catalyst is more preferably 15 ppm or more, further preferably 20 ppm or more, particularly preferably 25 ppm or more, and most preferably 40 ppm or more.

[0066] (Crosslinking reaction inhibitor) In order to suppress the activity of the platinum-based catalyst at room temperature, it is preferable that the aqueous coating composition contains a crosslinking reaction inhibitor. The crosslinking reaction inhibitor is preferably a crosslinking reaction inhibitor having an alkynyl group. The crosslinking reaction inhibitor having an alkynyl group is not particularly limited as long as it has an alkynyl group, but specific examples include 1-ethynyl-1-cyclohexanol, 4-ethyl-1-octyn-3-ol, 3-methyl-1-dodecyn-3-ol, 3,7,11-trimethyl-1-dodecyn-3-ol, 1,1-diphenyl-2-propyn-3-ol, 3-ethyl-6-ethyl-1-nonyn-3-ol, 3-methyl-1-pentadecyn-3-ol, 2,5-dimethyl-3-hexyne-2,5-diol, and 3-phenyl-1-butyn-3-ol. These may be used alone or in combination of two or more. Since the present invention employs an aqueous emulsion coating composition, it is preferable to use a crosslinking reaction inhibitor having an alkynyl group and a hydroxyl group, as exemplified above, in view of the balance of affinity and solubility in water, coordination ability to platinum, and boiling point.

[0067] The content of the crosslinking reaction inhibitor is preferably 5 ppm or more and 1000 ppm or less, more preferably 10 ppm or more and 700 ppm or less, and even more preferably 20 ppm or more and 500 ppm or less, based on the mass of the aqueous coating composition used to form the release layer. If the content of the crosslinking reaction inhibitor is above the lower limit, the pot life is extended, the addition curing reaction of silicone is less likely to proceed at room temperature, and silicone aggregates are less likely to occur. If the content of the crosslinking reaction inhibitor is below the upper limit, the silicone is less likely to migrate to the counter material after peeling it off, and the amount of reaction inhibitor volatilized during heat treatment is reduced, making it less likely that the inside of the oven will be contaminated.

[0068] (Other ingredients) To the release coating composition of the present invention, for example, an agent for imparting adhesion to the substrate, a colorant, an ultraviolet absorber, particles, an antistatic agent, etc. may be further added within a range that does not impair the object of the present invention.

[0069] (Preparation of silicone water dispersion) In preparing each of the silicone water dispersions of the present invention, there can be mentioned a method of emulsifying the silicone component, aqueous solvent, and emulsifier described above.These components can be emulsified by a known method, for example, by mechanically emulsifying a pre-prepared silicone, an emulsifier, and, if necessary, other components, in an aqueous medium using a stirring device such as a homogenizer, an azihomobiotic mixer, or an ultra-planetary mixer.

[0070] The particle size of the aqueous dispersion can be adjusted by adjusting the size of the stirring blades, the stirring speed, and the stirring time. The average particle size of each silicone aqueous dispersion of the present invention is preferably 200 nm or less, and more preferably 100 nm or more and 200 nm or less.

[0071] [Coating layer] In the present invention, a coating layer (release layer) is formed on at least one surface of a polyester film using the release coating composition of the present invention. The coating layer (release layer) of the present invention is formed by applying the release coating composition to the polyester film and then drying the coating composition.

[0072] In the present invention, the thickness of the coating layer after drying is preferably 5 nm to 70 nm. If the thickness of the coating layer is less than the lower limit, the release properties may be insufficient, while if the thickness exceeds the upper limit, the peel strength increases and the coating liquid needs to be concentrated or the coating amount needs to be increased, which tends to make coating more difficult.

[0073] When applying the release coating composition of the present invention to a polyester film, an aqueous coating liquid containing the composition is prepared, and the solids concentration of the aqueous coating liquid is preferably 20% by mass or less, more preferably 1% by mass or more and 10% by mass or less, based on the mass of the coating liquid. If the solids concentration in the aqueous coating liquid is less than the lower limit, the coating ability to the polyester film may be insufficient. On the other hand, if the solids concentration exceeds the upper limit, the stability of the coating liquid and the appearance of the coating layer may be deteriorated. Water is preferably used as the aqueous solvent for adjusting the solids concentration.

[0074] The aqueous coating solution can be applied to the polyester film at any stage, but is preferably applied during the polyester film production process, and more preferably to the polyester film before the orientation crystallization is completed.

[0075] Here, polyester films before completion of crystal orientation include unstretched films, uniaxially oriented films obtained by aligning unstretched films in either the machine direction (hereinafter referred to as the direction of continuous film production, longitudinal direction, or MD) or the transverse direction (hereinafter referred to as the direction perpendicular to the machine direction, width direction, or TD), and films oriented by low-magnification stretching in both the machine direction and the transverse direction (biaxially oriented films before final re-stretching in the machine direction or the transverse direction to complete orientation crystallization). Among these, so-called in-line coating is preferred, in which an aqueous coating solution of the composition is applied to an unstretched film or a uniaxially oriented film, followed by machine stretching and / or transverse stretching and heat setting. The coating layer may be dried by a stretching step or heat setting treatment after coating, or a drying step may be added as needed. Furthermore, when the composition is cured using a catalyst to obtain a cured coating, the curing can be achieved by a stretching step or heat setting treatment, but a curing step may also be added as needed.

[0076] When applying the aqueous coating liquid to a polyester film, it is preferable to subject the film surface to a physical treatment such as corona surface treatment, flame treatment, or plasma treatment as a preliminary treatment to improve coatability, or to use the above-mentioned emulsifier together with the composition as a wetting agent.

[0077] Any known coating method can be used as the coating method, for example, roll coating, gravure coating, roll brushing, spray coating, air knife coating, impregnation, curtain coating, etc., which can be used alone or in combination.

[0078] <Method of manufacturing silicone release polyester film> The method for producing a silicone release polyester film of the present invention comprises the steps of: At least one surface of the polyester film is provided with an alkenyl group and / or SiO 4 / 2 a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: (A) (B) (C) (D) (E) (F) (H ... (F)) (F)) (F)) (F)) (F)) (F)) (F)) The number average molecular weight of the silicone A is 150,000 or more, The content of Si atoms contained in the Q units is in the range of 0.05 mol % to 60 mol %.

[0079] The method for producing a silicone release polyester film of the present invention makes it possible to efficiently and easily obtain a silicone release polyester film having the above-mentioned properties. Note that the production method shown here is only an example, and the present invention is not limited to this.

[0080] In the above-mentioned manufacturing method, the descriptions regarding the silicone release polyester film and the like in this specification can be applied mutatis mutandis to the respective components as appropriate.

[0081] In the above-described production method, as the step of forming a coating layer using a water-dispersed release coating composition, any known method can be used as appropriate as long as it is a method of forming a coating layer on a film using a water-dispersed release coating composition. [Example]

[0082] The present invention will be specifically described using examples, but the present invention is not limited to the following examples. The physical properties and characteristics in the examples were measured or evaluated by the following methods. Furthermore, the term "parts" means "parts by mass."

[0083] Measurements and evaluations in the examples were carried out as follows.

[0084] (1) Adhesive tape releasability The adhesive tape peel strength is the strength obtained by laminating a polyester adhesive tape (Nitto Denko Corporation, No. 31B) to the surface of the coating layer (release layer) of a release film, pressing it with a 5 kg pressure roller, leaving it for 30 minutes or more, and then measuring the peel strength between the release layer and the adhesive tape (peel angle 180 degrees, peel speed 300 mm / min, unit: g / 25 mm width) with a peel strength tester. The silicone release polyester film of the present invention preferably has a peel strength of 20 g / 25 mm or more and 400 g / 25 mm or less.

[0085] (2)Residual adhesion rate The peel strength of a polyester adhesive tape (Nitto Denko, No. 31B) applied to a cold-rolled stainless steel plate (SUS304) specified in JIS G4305 was measured and recorded as the base adhesive strength (f0). The polyester adhesive tape was also pressed onto the release layer surface of a release polyester film using a 5 kg pressure roller, maintained for 30 seconds, and then peeled off. The peeled adhesive tape was then applied to the stainless steel plate and the peel strength was measured and recorded as the residual adhesive strength (f). The residual adhesion rate was calculated from the obtained base adhesive strength (f0) and residual adhesive strength (f) using the following formula. The peel angle was 180 degrees and the peel speed was 300 mm / min. Residual adhesion rate (%)=(f) / (f0)×100 A residual adhesion rate of 90% or more is preferable, indicating a high silicone crosslink density, and a rate of less than 90% indicates insufficient crosslinking.

[0086] [Examples 1 to 3, Comparative Examples 1 to 4] Molten polyethylene terephthalate ([η]=0.64 dl / g, Tg=78°C) containing 0.1 mass% of calcium carbonate particles with an average particle size of 0.7 μm was extruded through a die and cooled on a cooling drum in a conventional manner to form an unstretched film. The film was then stretched 3.6 times in the machine direction, and an aqueous coating liquid (aqueous dispersion with a solid content of 3 mass%) prepared by mixing the components to obtain the solid content ratio shown in Table 1 was uniformly applied to the surface of the film using a roll coater.

[0087] The coated film was then dried at 115°C for about 5 seconds, stretched 4.5 times in the transverse direction at 145°C, and further heat-set at 230°C for about 5 seconds to obtain a 25 μm biaxially stretched polyester film having the coating layer shown in Table 1.

[0088] (Water dispersion of silicone (1-a) containing alkenyl groups and Q units) Using an emulsifier capable of stirring the entire container (NP Labs, device name "Ultra Planetary Mixer"), raw materials consisting of 95% by mass of silicone (1) and 5% by mass of polyoxyethylene tridecyl ether (Takemoto Yushi Co., Ltd., trade name "New Calgen D-1208") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous dispersion of silicone (1-a) with a solids content of 20% by mass. The emulsion particle size was adjusted to an average particle size of 200 nm by adjusting the stirring speed and stirring time during emulsification.

[0089] The composition of silicone (1-a) is as follows: 1 is a vinyl group, R 2 is a methyl group, and the silicon to which the vinyl group is directly bonded contains 6.00 mol% of structural units to which only one vinyl group is bonded, 60.00 mol% of structural units composed of Q units where a=b=0 in formula (I), and R2 is a methyl group, and is composed of 34.00 mol% of structural units where a=0 and b=2 (both terminals have a=0 and b=3), and was adjusted so that the number average molecular weight was 240,000 (1-a). R 1 a R 2 b SiO (4-a-b) / 2 (I) (In formula (I), R 1 is an alkenyl group having 2 to 8 carbon atoms, R 2 represents a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from alkyl groups or aryl groups, a represents an integer of 0 to 3, and b represents an integer of 0 to 3, and a+b≦3.

[0090] (Water dispersion of silicone (1-b) containing an alkenyl group and not containing a Q unit) Using an emulsifier capable of stirring the entire container (NP Labs, device name "Ultra Planetary Mixer"), raw materials consisting of 95% by mass of silicone (1-b) and 5% by mass of polyoxyethylene tridecyl ether (Takemoto Yushi Co., Ltd., trade name "New Calgen D-1208") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous dispersion of silicone (1-b) with a solids content of 20% by mass. The emulsion particle size was adjusted to an average particle size of 200 nm by adjusting the stirring speed and stirring time during emulsification.

[0091] The composition of silicone (1-b) is as follows: 1 is a vinyl group, R 2 is a methyl group, and only one vinyl group is bonded to the silicon atom directly bonded to the vinyl group, and the vinyl group is bonded to a terminal silicon atom. The repeating number of the silicon atom bonded to the vinyl group is 3, and the structural unit of dimethylsiloxane (both terminals are vinyl groups) is composed, and the number average molecular weight was adjusted to 40,000 by the repeating number of the latter structural unit.

[0092] (Water dispersion of silicone (2) having Si-H groups) Using an emulsifier capable of stirring the entire container (NP Labs, equipment name "Ultra Planetary Mixer"), raw materials consisting of 97% by mass of Si-H group-containing silicone (2) and 3% by mass of polyoxyethylene tridecyl ether (Takemoto Yushi Co., Ltd., trade name "New Calgen D-1208") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous dispersion (2) of Si-H group-containing silicone (2) with a solids content of 10% by mass. The emulsion particle size was adjusted to an average particle size of 160 nm by adjusting the stirring speed and stirring time during emulsification. R 3 c H d SiO (4-c-d) / 2 (II) (In formula (II), R 3 represents a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, c represents an integer of 0 to 2, and d represents an integer of 1 to 3, and c+d≦3.

[0093] The Si-H group-containing silicone composition is a compound represented by the formula (II), 3 is a methyl group, and c=d=1, meaning that only one hydrogen group is bonded to the silicon atom to which a hydrogen group is directly bonded, and no hydrogen atoms are bonded to the terminal silicon atoms. The repeating number of structural units having silicon atoms to which hydrogen groups are directly bonded is 30, and the structural unit of dimethylsiloxane (both terminals are methyl groups), and the number average molecular weight was adjusted to 5,000 depending on the repeating number of the latter structural unit.

[0094] (Silicone coating solution adjustment) As an aqueous coating composition (release coating composition), an aqueous silicone dispersion was prepared by mixing an aqueous dispersion of silicone (1-a) or an aqueous dispersion of silicone (1-b), and a silicone (2) having a Si-H group in the solid content blending ratio shown in Table 1, and 40 ppm of the following platinum-based catalyst relative to the total coating liquid mass of silicone (1-a) and silicone (2), and 200 ppm of the following crosslinking reaction inhibitor relative to the coating mass, and the solid content concentration of the coating liquid was diluted with water to prepare a coating liquid having a dry coating thickness of 40 nm. Platinum catalyst: Platinum catalyst emulsion (manufactured by Shin-Etsu Chemical Co., Ltd., product name "CAT-PM-10A") Crosslinking reaction inhibitor: 1-ethynylcyclohexanol (Alfa Lancaster)

[0095] The formulation and results are shown in Table 1. The numerical values ​​for each silicone represent parts by mass of solid content.

[0096] [Table 1]

[0097] As can be seen from Table 1, the films of the examples of the present invention were excellent in releasability and residual adhesion. This was because the use of a specific composition containing a very high molecular weight silicone resulted in a film with various releasability and excellent residual adhesion. On the other hand, in Comparative Example 1, crosslinking was insufficient, resulting in heavy peeling. In Comparative Example 2, the amount of SiH residues in the silicone (2) increased, which increased transfer, resulting in a decrease in the residual adhesion. In Comparative Example 3, crosslinking was insufficient, resulting in an increase in transfer of the base compound, resulting in a decrease in the residual adhesion. In Comparative Example 4, the amount of SiH residues in the silicone (2) increased, which increased transfer, resulting in a decrease in the residual adhesion.

Claims

1. At least one surface of the polyester film is provided with an alkenyl group and SiO ４／２ a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: (A) (B) (C) (D) (E) (F) (H ... (F)) (F)) (F)) (F)) (F)) (F)) (F)) (F)) (F)) (F)) The number average molecular weight of the silicone (A) is 150,000 or more, the content of Si atoms contained in the Q units is 0.05 mol % or more and 60 mol % or less; Silicone release polyester film.

2. 2. The silicone release polyester film according to claim 1, wherein the content of the silicone (B) is 3 parts by mass or more and 45 parts by mass or less, when the total content of the silicone (A) and the silicone (B) is 100 parts by mass.

3. 2. The silicone release polyester film according to claim 1, wherein the alkenyl group of the silicone (A) is a vinyl group.

4. 2. The silicone release polyester film according to claim 1, wherein the peel strength after application to a polyester adhesive tape is 20 g / 25 mm width or more and 400 g / 25 mm width or less.

5. A silicone release polyester film as described in claim 1, wherein the number average molecular weight of the silicone (A) is 150,000 or more and 1,000,000 or less.

6. A silicone release polyester film as described in claim 1, having a residual adhesion rate of 90% or more after being attached to and peeled off from a polyester adhesive tape.

7. A silicone release polyester film as described in claim 1, wherein the thickness of the coating layer is 5 nm or more and 70 nm or less.

8. The silicone release polyester film according to any one of claims 1 to 7, which is used in forming ceramic green sheets in the production of multilayer ceramic capacitors.

9. At least one surface of the polyester film is provided with an alkenyl group and SiO ４／２ a water dispersion (1) of one or more silicones (A) containing Q units represented by the formula: The number average molecular weight of the silicone A is 150,000 or more, The content of Si atoms contained in the Q units is in the range of 0.05 mol % or more and 60 mol % or less. Method for producing silicone release polyester film.

10. The production method according to claim 9, wherein the content of the silicone (B) is 3 parts by mass or more and 45 parts by mass or less, relative to 100 parts by mass of the total content of the silicone (A) and the silicone (B).

11. The method according to claim 9 or 10, wherein the alkenyl group of the silicone (A) is a vinyl group.

12. A manufacturing method as described in claim 9 or 10, comprising a step of drying the coating layer at a temperature of 115°C or higher and 230°C or lower after coating the coating layer.

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