Release film

Abstract

The present invention provides a release film that readily achieves both releasability and wettability of a release layer, and has high coating uniformity of the release layer. In addition, provided is a release film having excellent recyclability and excellent adhesion between a release layer and a substrate.　The present invention is a release film having: a substrate film; and a release layer obtained by reacting and solidifying an aqueous coating composition, wherein the aqueous coating composition contains an alkenyl group-containing silicone (A) having a number average molecular weight of 1,000 to 14,000, and a Si-H group-containing silicone (B) having a phenyl group.

Description

Release film

[0001] The present invention relates to a release film having a base film and a release layer, and relates to a release film that is useful as a film for various processes.

[0002] Conventionally, release films using a polyester film or the like as a substrate have high heat resistance and mechanical properties, and are used as process films for producing adhesive sheets, cover films, ceramic slurries, polymer electrolyte membranes, and other resin sheets. Furthermore, as the release layer of a release film, many release layers formed from coating compositions containing silicone have been proposed because of their good heat resistance and releasability (Patent Documents 1 to 5).

[0003] The release film is also used as a process film for molding ceramic green sheets, which require high smoothness for ceramic capacitors, ceramic substrates, etc. In recent years, as multilayer ceramic capacitors have become smaller and have increased capacity, the thickness of ceramic green sheets has also tended to decrease. Ceramic green sheets are molded by coating a slurry containing ceramic components such as barium titanate and a binder resin onto the release layer of a release film and drying the slurry. Electrodes are printed on the molded ceramic green sheets, which are then peeled off from the release film to obtain ceramic green sheets with electrodes. Multilayer ceramic capacitors are then manufactured by laminating, pressing, firing, and applying external electrodes to the resulting ceramic green sheets.

[0004] Patent Documents 1 and 2 propose release films in which a release layer is formed from a coating composition containing a polysiloxane having an unsaturated group, a polysiloxane having a phenyl group and an Si—H group, and a platinum group metal catalyst. The solvent-free silicone used is described as having the effect of exhibiting excellent adhesion, particularly to plastic film substrates.

[0005] Patent Document 3 also proposes a release film having a release layer formed from a coating composition containing a polysiloxane having an unsaturated group, a polysiloxane having a phenyl group and an Si—H group, and a platinum group metal catalyst. These films are generally produced by in-line coating, a process in which an amorphous polymer melt is extruded and solidified into a sheet, a release coating layer is applied to the sheet, and the resulting film is then subjected to processes such as preheating, stretching, heat setting, and cooling, resulting in improved adhesion to polyester films.

[0006] Patent Document 4 proposes a release film in which a release layer is formed from a coating composition containing a polysiloxane having an unsaturated group with a weight average molecular weight of 500 or more and 30,000 or less, a polysiloxane having an Si—H group with a weight average molecular weight of 150 or more and 10,000 or less, and a platinum group metal catalyst. It is described as having good releasability from the adhesive, little migration of the adhesive to the member, and good antistatic properties.

[0007] Patent Document 5 proposes a release film having a release layer formed thereon, the release layer being a coating composition containing a polysiloxane having an unsaturated group, a polysiloxane having an Si—H group, and a platinum group metal catalyst, the ratio of the unsaturated group to the Si—H group being specified. It states that even when the release agent layer of the release sheet is exposed to the atmosphere for a long period of time, an increase in the peel strength between the release agent and the pressure-sensitive adhesive can be suppressed.

[0008] Japanese Patent Application Laid-Open No. 2018-012827 Japanese Patent Application Laid-Open No. 2018-119056 Japanese Patent Application Laid-Open No. 2011-509323 International Publication No. 2017 / 200056 Japanese Patent Application Laid-Open No. 2013-202831

[0009] However, in recent years, there has been a trend toward thinner ceramic green sheets and other components formed on the release layer of a release film. This means that the surface of the release layer may require both releasability and wettability to ceramic slurries, making it difficult to achieve both. In other words, changing the chemical composition of the release layer to enhance wettability reduces releasability. Furthermore, there has been a problem in that no release film has been developed that combines recyclability and substrate adhesion. For example, with regard to recyclability, when recycled resins made from release films are used in new release films, foreign matter originating from the recycled resin can be generated, appearing as protrusions on the surface and deteriorating surface smoothness. With regard to adhesion between the substrate and the release layer, there has been a problem in that ceramic slurries are transferred to the rolls that come into contact with the release film when they are applied, resulting in changes in releasability.

[0010] Patent Documents 1 to 3 do not anticipate applications for molding ceramic green sheets, and evaluate the releasability of adhesive tape. However, they do not suggest the releasability of thin ceramic green sheets. Furthermore, a crosslinking agent having a phenyl group is used to improve the adhesion between the substrate and the release layer, but the effect of the phenyl group on the release force is not recognized, and the film is not suitable as a release film with easy releasability applicable to thin ceramic green sheets, etc.

[0011] Patent Document 4 proposes a release film having a release layer made of a coating composition including a polysiloxane having an unsaturated group and a weight average molecular weight of 500 or more and 30,000 or less, and a polysiloxane having an Si—H group and a weight average molecular weight of 150 or more and 10,000 or less, but does not suggest achieving both releasability and wettability.

[0012] In Patent Document 5, polysiloxane having an unsaturated group and a weight average molecular weight of 1,100,000 is used, which has poor wettability and causes problems such as poor coating uniformity of the release layer.

[0013] An object of the present invention is to provide a release film in which the release layer can be easily made to have both good releasability and wettability, and the release layer can be applied with high uniformity.Furthermore, an object of the present invention is to provide a release film which has the advantages of good recyclability and excellent adhesion between the substrate and the release layer.

[0014] As a result of extensive research into solving these problems, the present inventors discovered that the above problems could be solved by a release layer formed by reacting and solidifying an aqueous coating composition containing an alkenyl group-containing silicone (A) having a predetermined molecular weight and the Si—H group-containing silicone (B) having a phenyl group according to the present invention, and thus completed the present invention.

[0015] [1] A release film having a substrate film and a release layer formed by reacting and solidifying an aqueous coating composition, wherein the aqueous coating composition contains an alkenyl group-containing silicone (A) having a number average molecular weight of 1,000 or more and 14,000 or less, and a Si—H group-containing silicone (B) having a phenyl group, and the Si—H group-containing silicone (B) is represented by general formula (I).

[0016]

[0017] (In formula (I), a1 is a natural number selected from 1 to 50, b1 is a natural number selected from 1 to 50, and c1 is a natural number selected from 0 to 50.) [2] The release film according to [1], wherein the Si—H group-containing silicone (B) includes one having a number average molecular weight of 1,000 or more and 5,000 or less. [3] The release film according to [1] or [2], wherein the alkenyl group-containing silicone (A) is represented by the following general formula (II):

[0018]

[0019] (In general formula (II), R1 may be the same or different and is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon group having 1 to 16 carbon atoms, including an alkyl group or a phenyl group, provided that [SiO] ａ２ R1 bonded to the silicon atom shown in is not an alkenyl group but [SiO] ｃ２At least one of R1 bonded to the silicon atom represented by [SiO] is the alkenyl group. ｂ２ Y1s bonded to silicon atoms represented by the formula (III) may be the same or different and are selected from the group consisting of an alkenyl group having from 2 to 8 carbon atoms, a monovalent hydrocarbon group having from 1 to 16 carbon atoms including an alkyl group or a phenyl group, and a group represented by the following general formula (III): In general formula (III), R1 may be the same group as at least one R1 in general formula (II), and in general formula (III), R1s may be the same or different. When the total of a2, b2, c2, and all of d2 is 100 mol%, a2 is 1 mol% or more, b2 is 0 mol% or more, c2 is 0 mol% or more, and d2 is 0 mol% or more.

[0020]

[0021] [4] The release film according to any one of [1] to [3], wherein the content of the Si—H group-containing silicone (B) is 3 to 30 parts by mass when the total of the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B) is 100 parts by mass.

[0022] [5] The release layer is formed by applying the aqueous coating composition to a substrate film before the crystal orientation is completed, stretching the substrate film in at least one direction, and then heat-treating the substrate film to complete the crystal orientation. [6] The release film according to any one of [1] to [4].

[0023] [6] The release film according to any one of [1] to [5], wherein the base film is a polyester film.

[0024] [7] The release film according to any one of [1] to [6], wherein the release film is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.

[0025] According to the present invention, it is possible to provide a release film that has the advantages of easily achieving both releasability and wettability of the release layer, high coating uniformity of the release layer, good recyclability, and excellent adhesion.

[0026] Although the details of why such an effect is obtained are not clear, a silicone crosslinked body formed by the reaction of relatively low molecular weight silicones easily forms a dense three-dimensional structure, and therefore is likely to maintain its hardness even when in contact with an organic solvent, thereby reducing the adhesion force when peeling off a laminate that has been coated and cast onto the surface of a release layer. Furthermore, a silicone crosslinked body with a dense three-dimensional structure is less likely to form a helical structure such as polydimethylsiloxane, which also affects the surface free energy of the release layer surface, and is therefore likely to exhibit appropriate wettability to the laminate.

[0027] Furthermore, by lowering the molecular weight of the silicone contained in the aqueous coating composition, the stability and uniformity of the coating film are increased, and it is thought that aggregates are less likely to occur in the release layer, thereby improving coating uniformity.In addition, when remelted during recycling, since the coating film has a high uniformity, it is easy for the coating films to disperse within the remelted base film resin, and it is thought that foreign matter is less likely to occur.

[0028] Furthermore, by using a release layer containing a cured product of silicone that further contains a siloxane structure having a phenyl group, the phenyl groups are more likely to be arranged on the substrate side and the methyl groups are more likely to be arranged on the surface of the release layer, improving the ease of releasability and resulting in a release film with excellent adhesion to the substrate.

[0029] The present invention will be described in detail below.

[0030] <Polyester Film> The polyester constituting the polyester film used as the base film is not particularly limited, and a film formed from 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-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or copolymers primarily composed of these resin components are even more preferred. 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 be copolymerized with small amounts of other dicarboxylic acid components or diol components. For example, from the standpoint of cost, polyethylene terephthalate produced solely from terephthalic acid and ethylene glycol is preferred. Furthermore, known additives, such as antioxidants, light stabilizers, UV absorbers, and crystallization agents, may be added within limits that do not impair the effects of the release film of the present invention. The polyester film is preferably a biaxially oriented polyester film due to its high bidirectional elastic modulus.

[0031] 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 0.62 dl / g or less. When the intrinsic viscosity is 0.50 dl / g or more, breakage does not occur frequently during the stretching process, which is preferable. Conversely, when the intrinsic viscosity is 0.70 dl / g or less, cuttability is good when cutting to a predetermined product width, and dimensional defects do not occur, which is preferable. It is also preferable to thoroughly vacuum dry the raw material pellets.

[0032] In this specification, when simply referring to a "polyester film," it may refer to a polyester film having (laminated with) a surface layer A and a surface layer B.

[0033] The method for producing the polyester film of the present invention is not particularly limited, and any conventionally 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.

[0034] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition temperature (Tg) of the polyester. Stretching is preferably performed at a magnification of 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0035] The polyester film preferably has a thickness of 12 μm or more and 50 μm or less, more preferably 15 μm or more and 38 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 50 μm or less is preferable because the amount of film discarded after use is not excessively large, thereby reducing the environmental load.

[0036] 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.

[0037] 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. When the surface layer A is 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.

[0038] In one embodiment, the surface layer A does not contain particles having a particle size of less than 1.0 μm, so that defects caused by the transfer of particle shapes in the substrate to the resin sheet can be more effectively prevented.

[0039] 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 thereof, which more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet.

[0040] For example, it is preferable that the surface layer A substantially does not contain particles having a particle size of less than 1.0 μm, and also substantially does not contain particles having a particle size of 1.0 μm or more.

[0041] 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.

[0042] 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.

[0043] As for 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 have 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 inorganic particles and a binder on surface layer B to impart slip properties for winding the film into a roll.

[0044] 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, and in particular, 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.

[0045] In this case, the area surface average roughness (Sa) of the film of the surface layer B is preferably in the range of 1 nm to 40 nm. More preferably, it is in the range of 5 nm to 35 nm. When the total content 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 content 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.

[0046] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used as particles contained in Layer B. 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, and 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.

[0047] 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, particularly preferably 0.5 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.

[0048] From the viewpoint of reducing pinholes, it is preferable that recycled raw materials or the like are not used for the surface layer A, which is the layer on which the release layer is to be formed, in order to prevent the inclusion of inorganic particles such as lubricants.

[0049] The thickness ratio of the surface layer A, which is the layer on which the release layer is provided, is preferably 20% to 50% of the total layer thickness of the base film. If it is 20% or more, the film is less likely to be affected from the inside by particles contained in the surface layer B, etc., and it is easy for the regional surface average roughness Sa to satisfy the above range, which is preferable. If it is 50% or less of the total layer thickness of the base film, the proportion of recycled raw materials used in the surface layer B can be increased, which is preferable as it reduces the environmental load.

[0050] From the viewpoint of economic efficiency, recycled raw materials such as film scraps and PET bottles may be used in an amount of 50% by mass to 90% by mass for the layers (surface layer B or the aforementioned intermediate layer C) other than the surface layer A. Even in this case, it is preferable that the type and amount of the lubricant contained in layer B, its particle size, and the area surface average roughness (Sa) satisfy the above-mentioned ranges.

[0051] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, or to prevent static charging, 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, or a surface treatment may be applied.

[0052] In one embodiment, the release layer-forming surface to which the aqueous coating composition is applied can be subjected to a surface treatment or provided with an easy-adhesion layer in order to enhance adhesion to the release layer. Examples of surface treatments include plasma treatment, corona discharge treatment, ultraviolet treatment, flame treatment, and electron beam / radiation treatment. Examples of the easy-adhesion layer include a layer containing the same resin as the substrate film and further containing an antistatic agent, a pigment, a surfactant, a lubricant, an antiblocking agent, etc. When an adhesion improver such as a coupling agent is added to the aqueous coating composition, the release layer can have sufficient adhesion to the substrate film even without providing an easy-adhesion layer, etc.

[0053] <Release Layer> In the present invention, the release layer is laminated on the substrate film, for example, the release layer is laminated on the surface layer A of the substrate. The release layer of the present invention is a layer formed by reacting and solidifying an aqueous coating composition.

[0054] The aqueous coating composition comprises an alkenyl group-containing silicone (A) having a number average molecular weight of 1,000 or more and 14,000 or less, and an Si—H group-containing silicone (B) having a phenyl group, wherein the Si—H group-containing silicone (B) is represented by the following general formula (I):

[0055]

[0056] (In formula (I), a1 is a natural number selected from 1 to 50, b1 is a natural number selected from 1 to 50, and c1 is a natural number selected from 0 to 50.)

[0057] The release layer may contain a Si—H group-containing silicone (C) that does not contain a phenyl group (for example, this may be referred to as a phenyl group-free Si—H group-containing silicone (C)).

[0058] The combined use of the Si-H group-containing silicone (C) having no phenyl groups and the Si-H group-containing silicone (B) having a phenyl group is preferable because it is possible to control the methyl groups arranged on the release layer surface and to control the wettability and releasability of the ceramic slurry compared to using only the Si-H group-containing silicone (B) having a phenyl group. In addition, it is possible to increase the number of crosslinking reaction points, which increases the cohesive force of the release layer and improves the abrasion resistance and solvent resistance of the release layer, which is also preferable.

[0059] (Alkenyl Group-Containing Silicone (A)) The alkenyl group-containing silicone (A) is an organopolysiloxane represented by the following general formula (II).

[0060]

[0061] (In general formula (II), R1 may be the same or different and is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon group having 1 to 16 carbon atoms, including an alkyl group or a phenyl group, provided that [SiO] ａ２ R1 bonded to the silicon atom shown in is not an alkenyl group but [SiO] ｃ２ At least one of R1 bonded to the silicon atom represented by [SiO] is the alkenyl group. ｂ２ Y1s bonded to silicon atoms represented by the formula (III) may be the same or different and are selected from the group consisting of an alkenyl group having from 2 to 8 carbon atoms, a monovalent hydrocarbon group having from 1 to 16 carbon atoms including an alkyl group or a phenyl group, and a group represented by the following general formula (III): In general formula (III), R1 may be the same group as at least one R1 in general formula (II), and in general formula (III), R1s may be the same or different. When the total of a2, b2, c2, and all of d2 is 100 mol%, a2 is 1 mol% or more, b2 is 0 mol% or more, c2 is 0 mol% or more, and d2 is 0 mol% or more.

[0062]

[0063] [SiO] of general formula (II) ａ２ [SiO] ｃ２ , [SiO] of general formula (III) ｄ１R1 bonded to the silicon atom represented by the formula (I) is preferably an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon group containing an alkyl group or a phenyl group. For example, [SiO] ａ２ [SiO] ｃ２ [SiO] ｄ１ At least one of R1's bonded to the silicon atom represented by the formula (I) is an alkenyl group having 2 to 8 carbon atoms.

[0064] When one or more of the R1 is an alkenyl group having 2 to 8 carbon atoms, [SiO] ａ１ This can produce the effect of reacting with the hydrogen groups bonded to the silicon atoms shown by the formula (I) to form a crosslinked structure.

[0065] In one embodiment, the terminal R1 can also be an alkenyl group having from 2 to 8 carbon atoms, or a monovalent hydrocarbon group containing an alkyl group or a phenyl group. For example, the terminal R1 is preferably an alkenyl group having from 2 to 8 carbon atoms or a methyl group. A terminal alkenyl group is particularly preferred because it causes relatively little steric structural hindrance when reacted with a Si—H group, making it easy to improve releasability.

[0066] Examples of the alkenyl group having 2 to 8 carbon atoms represented by R1 include a vinyl group, a phenyl group, a butenyl group, a pentenyl group, and a hexenyl group, and among these, a vinyl group is particularly preferred.

[0067] [SiO] in general formula (II) and general formula (III) ａ２ [SiO] ｂ２、 [SiO] ｃ２、 [SiO] ｄ１ When the total of the structural units is 100 mol%, [SiO] ｂ２ The range of the structural unit may be 0 mol%, but is preferably 1 mol% or more and 99 mol% or less, and more preferably 2 mol% or more and 80 mol% or less. For example, [SiO] ｂ２ The range of the structural unit may be 2 mol % or more and 50 mol % or less, or may be 2 mol % or more and 40 mol % or less.

[0068] Also, [SiO] ｂ２It is desirable that the structural unit of is within the above range, and that the number average molecular weight of the alkenyl group-containing silicone (A) is within the range described in this specification. Within the above range, the proportion of branched structures is just right, the hydrocarbon groups are localized on the coating film surface, and a dense film is formed, with good releasability and wettability.

[0069] When the sum of a2, b2, c2 and all d2 in general formula (II) and general formula (III) is 100 mol%, a2 is preferably 1 mol% or more, c2 is 0 mol% or more, and d2 is preferably 0 mol% or more. In particular, from the viewpoint of balancing the crosslink density and surface free energy of the release layer, a2 is more preferably 2 mol% or more and 90 mol% or less, c2 is 5 mol% or more and 90 mol% or less, and d2 is more preferably 10 mol% or more and 90 mol% or less, and a2 is even more preferably 5 mol% or more and 50 mol% or less, c2 is 10 mol% or more and 50 mol% or less, and d2 is even more preferably 30 mol% or more and 50 mol% or less.

[0070] The number average molecular weight of the alkenyl group-containing silicone (A) is 1,000 or more and 14,000 or less, for example, 1,000 or more and 12,000 or less, or may be 1,000 or more and 11,000 or less, or 1,000 or more and 10,000 or less, for example, 1,000 or more and less than 10,000.

[0071] In another embodiment, the number average molecular weight of the alkenyl group-containing silicone (A) may be 2000 or more and 12,000 or less, or 2500 or more and 12,000 or less.

[0072] When the number-average molecular weight is 1,000 or more, the hydrocarbon group is localized on the coating surface, making it easier to obtain sufficient releasability, while when the number-average molecular weight is 14,000 or less, the emulsification properties into aqueous coating compositions tend to be good, and wettability and uniform coating properties also tend to be good.

[0073] In the alkenyl group-containing silicone (A), the alkenyl group may be introduced at one end, both ends, or a side chain. The number of alkenyl groups in a molecule is two or more, preferably 2 to 20, more preferably 2 to 10. If there are two or more alkenyl groups, a crosslinked structure can be formed, and a sufficient number of crosslinking reaction points can be obtained. If there are 20 or less, the variation in the crosslinked structure can be reduced, and uniform releasability can be achieved. For example, the alkenyl group is introduced at one end or both ends. Furthermore, since the number of crosslinking reaction points is adequate, the size of foreign matter consisting of unmelted release layer contained in recycled resin produced from the release film can be reduced, which tends to improve recyclability.

[0074] In the aqueous coating composition, the Si—H group-containing silicone (B) having a phenyl group is preferably contained in an amount of 3 to 30 parts by mass, more preferably 4 to 20 parts by mass, and even more preferably 4.5 to 15 parts by mass, per 100 parts by mass of the total of the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B) having a phenyl group. A content of the Si—H group-containing silicone (B) of 3 parts by mass or more is preferred because it provides a sufficient number of crosslinking reaction sites, making it easier to form a dense crosslinked structure and improving releasability. A content of the Si—H group-containing silicone (B) of 30 parts by mass or less is preferred because it makes it difficult for Si—H groups to remain in the release layer, making it less likely for the activity of the release layer surface to increase and maintaining good releasability.

[0075] For example, the release layer may contain a plurality of alkenyl group-containing silicones (A) having molecular weights according to the present invention.

[0076] In another embodiment, the aqueous coating composition of the present invention may contain a phenyl-free Si—H group-containing silicone (C). In this embodiment, the amount of alkenyl group-containing silicone (A) contained in the aqueous coating composition is preferably 70 parts by mass or more and 95 parts by mass or less, or may be 75 parts by mass or more and 93 parts by mass or less, and more preferably 75 parts by mass or more and 88 parts by mass or less, per 100 parts by mass of the total of the alkenyl group-containing silicone (A), the Si—H group-containing silicone (B), and the phenyl group-free Si—H group-containing silicone (C). By incorporating such an amount, a sufficient number of crosslinking reaction sites are obtained, the cohesive strength of the release layer is increased, and the abrasion resistance and solvent resistance of the release layer are also improved, which is preferable.

[0077] The alkenyl group-containing silicone (A) preferably has a branched structure, because the presence of a branched structure gives the release layer a dense structure and improves releasability.

[0078] (Si—H Group-Containing Silicone Having Phenyl Groups (B)) The Si—H group-containing silicone having phenyl groups (B) is an organohydrogenpolysiloxane represented by the following general formula (I).

[0079]

[0080] (In formula (I), a1 is a natural number selected from 1 to 50, b1 is a natural number selected from 1 to 50, and c1 is a natural number selected from 0 to 50.) The Si—H group-containing silicone (B) having a phenyl group is preferably one having two or more Si—H groups (i.e., two or more hydrogen atoms directly bonded to Si atoms) in the molecule. In addition, the terminal silicon atom preferably has a trialkylsilane structure such as trimethylsilane.

[0081] In the Si—H group-containing silicone (B) represented by general formula (I), [SiO] ａ１ and [SiO] ｂ１ and [SiO] ｃ１ When the total of the structural units is 100 mol%, [SiO] ａ１The range of the structural unit [SiO] is preferably 40 mol % or more and 80 mol % or less, and more preferably 50 mol % or more and 70 mol % or less. ａ１ When the content of the constituent units is 40 mol % or more, the number of crosslinking reaction points becomes sufficient, the cohesive force of the release layer increases, and the abrasion resistance and solvent resistance of the release layer also become favorable, which is preferable.

[0082] In the Si—H group-containing silicone (B) represented by the general formula (I), [SiO] having a phenyl group ｂ１ The range of the structural unit having a phenyl group is preferably from 10 mol % to 40 mol %, and more preferably from 15 mol % to 35 mol %. ｂ１ When the structural unit (B) is 10 mol % or more, the bulkiness of the phenyl groups can prevent the curing reaction from proceeding too rapidly. For example, rapid curing of the release layer can be prevented before the substrate film is stretched. As a result, the stretchability of the coating composition is maintained, and a decrease in the adhesion between the release layer and the substrate due to the stress difference between the substrate film and the release layer does not occur, which is preferable. Furthermore, the π electrons of the phenyl groups in the Si—H group-containing silicone (B) and the aromatic rings in the substrate interact with each other, resulting in a stacking effect, which improves the adhesion between the substrate and the release layer. Furthermore, the arrangement of the phenyl groups on the substrate side facilitates the arrangement of methyl groups on the surface of the release layer, improving releasability.

[0083] In the Si—H group-containing silicone (B) represented by general formula (I), [SiO] ｃ１ The range of the structural unit is preferably 3 mol % or more and 30 mol % or less, and more preferably 5 mol % or more and 20 mol % or less. When the structural unit is 3 mol % or more, the amount of methyl groups localized on the surface of the release layer in the release layer increases, which is preferable because the release layer has good releasability.

[0084] The number average molecular weight of the Si—H group-containing silicone (B) according to the present invention is preferably 1,000 or more and 5,000 or less, and is preferably 1,000 or more and less than 5,000, for example, 1,500 or more and 4,000 or less, or may be 2,000 or more and 4,000 or less.

[0085] A number-average molecular weight of 1,000 or more makes it easier to obtain sufficient releasability. On the other hand, a number-average molecular weight of 5,000 or less improves the emulsification characteristics of the aqueous coating composition and tends to improve coating uniformity. In addition, the crosslinking reaction proceeds smoothly, and since the reaction does not occur during stretching but occurs efficiently after stretching, the number of residual Si-H groups in the release layer decreases, resulting in good releasability.

[0086] In the aqueous coating composition, the Si—H group-containing silicone (B) is preferably contained in an amount of 3 to 30 parts by mass, more preferably 4 to 20 parts by mass, and even more preferably 4.5 to 15 parts by mass, per 100 parts by mass of the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B). A content of 3 parts by mass or more of the Si—H group-containing silicone (B) is preferred because it provides a sufficient number of crosslinking reaction sites, making it easier to form a dense crosslinked structure and improving releasability. A content of 30 parts by mass or less of the Si—H group-containing silicone (B) is preferred because it makes it difficult for Si—H groups to remain in the release layer, making it less likely for the activity of the release layer surface to increase and maintaining good releasability.

[0087] By including the Si-H group-containing silicone (B) with a phenyl group, the adhesion of the release layer is improved compared to when only the Si-H group-containing silicone (C) without a phenyl group is used. The reason for this is unclear, but it is thought that the phenyl group segregates toward the substrate, which has a similar structure, and intermolecular forces act to make it easier to fix. At the same time, the methyl group segregates toward the surface, improving releasability.

[0088] (Phenyl Group-Free Si—H Group-Containing Silicone (C)) The release layer may contain a phenyl group-free Si—H group-containing silicone (C) (for example, this may be referred to as a phenyl group-free Si—H group-containing silicone (C)).

[0089] Examples of the phenyl-free Si—H group-containing silicone (C) include organohydrogenpolysiloxanes represented by the following general formula (IV):

[0090]

[0091] (In formula (IV), a3 is a natural number selected from 1 to 50, and b3 is a natural number selected from 10 to 80.)

[0092] In the phenyl-free Si—H group-containing silicone (C) represented by general formula (IV), [SiO] ａ３ and [SiO] ｂ３ When the total of the structural units is 100 mol%, [SiO] ａ３ The range of the structural unit is preferably 40 mol % or more and 80 mol % or less, and more preferably 45 mol % or more and 70 mol % or less. [SiO] ａ３ When the content of the structural unit [SiO] is 40 mol % or more, the number of crosslinking reaction sites becomes sufficient, the cohesive force of the release layer increases, and the abrasion resistance and solvent resistance of the release layer also become good, which is preferable. ｂ３ The range of the structural unit is preferably 20 mol % or more and 60 mol % or less, and more preferably 30 mol % or more and 55 mol % or less. [SiO] ｂ３ When the content of the structural unit of is 20 mol % or more, the amount of methyl groups localized on the surface of the release layer increases, which is preferable because the release layer has good releasability.

[0093] The number average molecular weight of the phenyl-free Si—H group-containing silicone (C) of the present invention is preferably 1,000 to 10,000, more preferably 2,000 to 8,000. When the number average molecular weight is 1,000 or more, sufficient releasability is easily obtained. On the other hand, when the number average molecular weight is 10,000 or less, the emulsification properties into an aqueous coating composition are improved, and coating uniformity also tends to be improved.

[0094] In the aqueous coating composition, the non-phenyl group-containing Si—H group-containing silicone (C) is preferably contained in an amount of 1 part by mass or more to 30 parts by mass or less, more preferably 3 parts by mass or more to 20 parts by mass or less, and even more preferably 5 parts by mass or more to 15 parts by mass or less, relative to a total of 100 parts by mass of the alkenyl group-containing silicone (A) and the non-phenyl group-containing Si—H group-containing silicone (C). When the content of the non-phenyl group-containing Si—H group-containing silicone (C) is 1 part by mass or more, a sufficient number of crosslinking reaction sites are obtained, which facilitates the formation of a dense crosslinked structure and improves releasability, which is preferable. When the content of the non-phenyl group-containing Si—H group-containing silicone (C) is 30 parts by mass or less, Si—H groups are less likely to remain in the release layer, which reduces uncrosslinked material, which is preferable because good releasability is maintained.

[0095] In one embodiment, the aqueous coating composition preferably contains 30 to 80 parts by mass of component (B), more preferably 32 to 75 parts by mass, and even more preferably 34 to 70 parts by mass, based on 100 parts by mass of the Si—H group-containing silicone (B) and the Si—H group-containing silicone (C) that does not contain a phenyl group. When component (B) is present in an amount of 30 parts by mass or more, the reaction can be controlled by the hardness of the phenyl group, and the number of crosslinking reaction sites can be reduced, thereby reducing the amount of recycled resin-derived foreign matter produced from the release film and improving recyclability. When component (B) is present in an amount of 80 parts by mass or less, the crosslinking reaction sites are sufficient, increasing the cohesive strength of the release layer and improving the abrasion resistance and solvent resistance of the release layer, which is preferable.

[0096] (Platinum-Based Catalyst) The crosslinking reaction between the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B) is an addition reaction, and in one embodiment, it is preferable to use a platinum-based catalyst to accelerate the reaction.

[0097] 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(0) complex (Karstedt's catalyst), which can be dispersed simultaneously with the silicone emulsification to ensure uniform dispersion.

[0098] The content of the platinum catalyst is preferably in the range of 10 ppm to 400 ppm by mass of platinum element relative to the combined mass of the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B). By setting the content in this range, the silicone can be sufficiently cured and the generation of silicone aggregates can be suppressed, resulting in a release film with excellent surface properties. When the mass ratio of platinum element is equal to or less than the upper limit, the addition reaction between the alkenyl group and the Si—H group becomes moderate, tending to suppress the generation of silicone aggregates. From this perspective, the content of the platinum catalyst is more preferably 300 ppm or less, and even more preferably 200 ppm or less. Furthermore, when the mass ratio of platinum element is equal to or greater than the lower limit, the addition reaction proceeds sufficiently, making it less likely that poor curing of the silicone will occur. From this perspective, the content of the platinum catalyst is more preferably 15 ppm or more, and even more preferably 20 ppm or more.

[0099] (Aqueous Solvent) In addition to the alkenyl group-containing silicone (A) and the Si—H group-containing silicone (B), the aqueous coating composition typically contains an aqueous solvent, with water being the preferred aqueous solvent. In one embodiment, an aqueous dispersion of the alkenyl group-containing silicone (A) and an aqueous dispersion of the Si—H group-containing silicone (B) are used to prepare the aqueous coating composition. As the aqueous dispersion of each silicone, an aqueous emulsion is preferably used.

[0100] The aqueous coating composition preferably contains substantially no organic solvent and uses water as a dispersion medium. The absence of organic solvent improves the stability of the silicone emulsion, preventing changes in the composition of the aqueous coating composition due to emulsion breakdown, and preventing aggregation and gelation of the resin in the silicone emulsion.

[0101] "Substantially free of organic solvents" means, for example, a content of 10,000 ppm or less, preferably 5,000 ppm or less, more preferably 3,000 ppm or less, and most preferably below the detection limit, based on the total weight of the aqueous coating composition. This is because, even if no organic solvent is intentionally used, small amounts of organic solvents used in the polymerization process of the resin contained in the silicone emulsion or the emulsification process of the emulsion may remain.

[0102] By using an emulsion type that contains a water-based solvent, i.e., silicone resin dispersed in water, it can be applied without causing any adverse effects on the human body or the environment.

[0103] (Other Components) In one embodiment, other additives such as surfactants, coupling agents, crosslinking reaction inhibitors, antistatic agents, ultraviolet absorbers, pigments, colorants, organic or inorganic particles, lubricants, and antiblocking agents may be mixed into the aqueous coating composition within a range that does not impair the effects of the invention.

[0104] (Surfactant) In one embodiment, in order to promote wetting of the substrate film when providing a release layer, it is preferable to add a surfactant to the aqueous coating composition. Such surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, etc., and it is also possible to use one or more of these. In order to prevent the aggregation of the respective aqueous silicone emulsions and not affect the curing reaction of the silicone, it is preferable to use a nonionic surfactant as an emulsifier.

[0105] The nonionic surfactant 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. The HLB value is calculated by Griffin's formula.

[0106] Examples of alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide, and one or more of these may be used. When more than one is used, the addition may be in block or random form, but the HLB value is preferably in the range of 8 to 18, and more preferably in the range of 10 to 15. Among these nonionic surfactants, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, etc. are preferred. If necessary, two or more types of nonionic surfactants may be mixed. If a nonionic surfactant with an HLB value outside this range is used as an emulsifier for a silicone aqueous dispersion, the emulsifying and dispersing power and the stability of the aqueous dispersion may be reduced.

[0107] The surfactant is preferably used in an amount of 0.1% by mass to 20% by mass, more preferably 0.2% by mass to 15% by mass, and even more preferably 0.5% by mass to 10% by mass, based on the total solid content. If the amount is above the lower limit of this range, the emulsification state becomes good, and if it is below the upper limit of this range, heavy peeling is less likely to occur.

[0108] (Crosslinking Reaction Inhibitor) In one embodiment, a reaction inhibitor is preferably contained in the aqueous coating liquid to suppress the activity of the platinum-based catalyst at room temperature. Such a reaction inhibitor is preferably a reaction inhibitor having an alkynyl group. The 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. Since the present invention is an aqueous coating liquid, it is preferable to use the reaction inhibitors exemplified above that have an alkynyl group and a hydroxyl group, in view of the balance between affinity and solubility in water and coordination ability to platinum, as well as the boiling point. Alternatively, the platinum catalyst may be mixed with a general organopolysiloxane and used as an aqueous emulsion in order to be added to the aqueous coating liquid.

[0109] 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. When the content of the crosslinking reaction inhibitor is equal to or greater than 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 tend to be less likely to occur. When the content of the crosslinking reaction inhibitor is equal to or less than the upper limit, the silicone is less likely to migrate to the counterpart material after peeling it off, and the amount of reaction inhibitor volatilized during heat treatment is reduced, so contamination inside the oven is less likely to occur.

[0110] (Coupling Agent) In one embodiment, a coupling agent can be added to the aqueous coating composition to improve adhesion between the silicone component and the substrate film. Examples of the coupling agent include those represented by the general formula YRSiX ３Examples of the compounds include silane coupling agents, where Y is an organic functional group such as a vinyl group, an epoxy group, an amino group, or a mercapto group, and it is particularly preferred that Y is an epoxy group or a vinyl group.

[0111] R is an alkylene group such as methylene, ethylene, or propylene, or a single bond. X is a hydrolyzable group such as a methoxy group, ethoxy group, or acetoxy group, or an alkyl group, and at least one of the three Xs is a hydrolyzable group, preferably all three Xs are hydrolyzable groups. The hydrolyzable group is preferably a methoxy group.

[0112] Preferred silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, and vinylmethyldimethoxysilane.

[0113] Other examples of coupling agents include organometallic compounds containing metals such as zirconium, titanium, and aluminum, and the organometallic compounds are preferably those classified as alkoxides, chelates, and acylates. Specific examples include, but are not limited to, zirconium tetraacetylacetonate, zirconium acetate, titanium acetylacetonate, triethanolamine titanate, and titanium lactate.

[0114] As the coupling agent, it is also possible to use two or more types of coupling agents, for example, a silane coupling agent in which Y is an epoxy group and a silane coupling agent in which Y is a vinyl group are used in combination.

[0115] In one embodiment, the addition of a coupling agent improves the durable adhesion between silicone, which is the main component of the release layer, and a polyester film or the like. For example, when a resin sheet is cast using a solution casting method that uses an organic solvent, the organic solvent component may penetrate into the release layer, potentially eroding the release layer, but the addition of a coupling agent can suppress this erosion. When a resin sheet is cast using a melt casting method at high temperatures, the release layer is exposed to high temperatures and may be thermally deteriorated, but the addition of a coupling agent suppresses this thermal deterioration and allows the release layer to be maintained.

[0116] From the above viewpoints, the content of the coupling agent is preferably 0.1 parts by mass or more and 20 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total of the alkenyl group-containing silicone and the Si—H group-containing silicone contained in the release layer.

[0117] (Preparation of Silicone Water Dispersion) In one embodiment, the aqueous emulsion is prepared by emulsifying a predetermined alkenyl group-containing silicone or Si—H group-containing silicone, an aqueous solvent, and a surfactant. These components can be emulsified by a known method, and examples include a method in which a predetermined silicone and surfactant, and, if necessary, other components, which have been prepared in advance, are mechanically emulsified in an aqueous medium using a stirring device such as a homogenizer, an azihomobiotic mixer, or an ultraplanetary mixer.

[0118] The particle size of the aqueous dispersion can be adjusted by adjusting the size of the stirring blade, the stirring speed, and the stirring time. The average particle size of the dispersed particles in each silicone aqueous dispersion is preferably 900 nm or less, and more preferably 100 nm or more and 800 nm or less.

[0119] <Formation of Release Layer> In one embodiment, the release layer is formed by applying an aqueous coating composition containing an aqueous emulsion of an alkenyl group-containing silicone and an aqueous emulsion of an Si—H group-containing silicone. In this case, the release layer is formed on at least one surface of the substrate film. The release layer is formed by applying the aqueous coating liquid to the substrate film, followed by heating and drying, whereby the components of the aqueous coating liquid react and solidify to form the release layer. The release layer is preferably formed during the film production process.

[0120] The thickness of the release layer is preferably 5 nm or more and 100 nm or less as the thickness after drying. If the thickness of the release layer is above the lower limit, sufficient releasability is easily obtained, and if it is below the upper limit, the peel strength tends not to increase, and there is no need to increase the concentration of the release layer component in the aqueous coating liquid or increase the coating amount, which tends to make coating easier. Therefore, the thickness of the release layer is more preferably 5 nm or more and 70 nm or less, and even more preferably 5 nm or more and 50 nm or less.

[0121] When the aqueous coating liquid is applied to a substrate film, the solid content is preferably 20% by mass or less, more preferably 1% by mass or more and 10% by mass or less, based on the release layer components in the aqueous coating liquid. When the solid content of the release layer components in the aqueous coating liquid is above the lower limit, the film-forming properties tend to be good. When the solid content is below the upper limit, the stability of the aqueous coating liquid and the appearance of the release layer tend to be good. Water is preferably used as the aqueous solvent for adjusting the solid content.

[0122] The aqueous coating solution to be applied to the base film to form the release layer can be applied at any stage, but is preferably applied during the polyester film production process, and more preferably to the polyester film before the completion of orientation crystallization. Thereafter, the polyester film is stretched in at least one direction and then heat-treated to complete the crystal orientation.

[0123] Here, polyester films before the completion of crystal orientation include unstretched films, uniaxially oriented films obtained by orienting unstretched films in either the longitudinal direction (hereinafter sometimes referred to as the direction of continuous film production, longitudinal direction, or MD direction) or the transverse direction (hereinafter sometimes referred to as the direction perpendicular to the longitudinal direction, width direction, or TD direction), and films that have been stretched and oriented at a low ratio in both the longitudinal and transverse directions (biaxially stretched films before they are finally re-stretched in the longitudinal or transverse direction to complete the orientation crystallization).

[0124] Among these, so-called in-line coating is preferred, in which an aqueous coating liquid is applied to an unstretched film or a uniaxially stretched film oriented in one direction, followed by longitudinal stretching and / or transverse stretching and heat setting. The release layer may be dried by a stretching step or heat setting treatment after coating, and a drying step may be added as needed. In addition, when the composition is cured using a catalyst to obtain a cured coating, the composition can be cured by a stretching step or heat setting treatment, but a curing step may be added as needed.

[0125] When applying an 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, or to add a surfactant as a wetting agent.

[0126] Any known coating method can be used as the coating method, such as roll coating, gravure coating, roll brushing, spray coating, air knife coating, impregnation, curtain coating, etc., which can be used alone or in combination.

[0127] <Characteristics of Release Film> In the present invention, the surface free energy of the release layer is 10 mJ / m ２ 40mJ / m or more ２ The following range is preferred, and 12 mJ / m is more preferred. ２ 38mJ / m or more ２ More preferably, 14 mJ / m or less ２ 36mJ / m or more２ Below 15 mJ / m, particularly preferably ２ 35mJ / m or more ２ The surface free energy of the release layer is within the following range. If the surface free energy is below the upper limit, the adhesive force is reduced and heavy release is difficult to occur. On the other hand, if the surface free energy is above the lower limit, defects due to repelling of a processed layer such as a ceramic sheet or a resin sheet coated on the surface of the release layer are difficult to occur, and pinhole defects are also difficult to occur.

[0128] <Uses> The release film of the present invention can be used as a process film used during the production of multilayer ceramic capacitors, during resin sheet casting, etc. For example, it can also be called a release film for multilayer ceramic capacitors or a release film for resin sheets.

[0129] In particular, even when a thin film resin sheet having a thickness of 1 μm or less after drying is produced, the wettability is good, so pinholes in the processing layer are reduced, and when used as a release film for producing green sheets, for example, the defective rate of thin multilayer ceramic capacitors can be reduced.

[0130] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The physical properties and other properties in the following examples were evaluated using the following methods.

[0131] (1) Surface Free Energy of Release Layer For a sample that had been conditioned for 24 hours under conditions of 23 ° C. and 50% RH, a contact angle meter (DMo-501 manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the static contact angle when water was dropped and allowed to stand for 30 seconds. Similarly, the static contact angles of ethylene glycol and methylene iodide were measured, and the following simultaneous equations relating to the surface tension components of the release layer were established using the surface tension components of each liquid below (the measured liquids of water, ethylene glycol, and methylene iodide are designated 1, 2, and 3, respectively, γLD is the dispersion force component of the liquid, γLP is the polar force component of the liquid, γLH is the hydrogen bond component of the liquid, γL is the total value of each surface tension component in the liquid, γSD is the dispersion force component of the release layer, γSP is the polar force component of the release layer, and γSH is the hydrogen bond component of the release layer. θ represents the contact angle).

[0132] (γSD / γLD1) １／２ +(γSP・γLP1) １／２ +(γSH・γLH1) １／２ =γL1(1+cosθ1) / 2 (γSD・γLD2) １／２ +(γSP・γLP2) １／２ +(γSH・γLH2) １／２ =γL2(1+cosθ2) / 2 (γSD・γLD3) １／２ +(γSP・γLP3) １／２ +(γSH・γLH3) １／２ = γL3(1 + cos θ3) / 2 Note that γLD, γLP, γLH, and γL for water, ethylene glycol, and methylene iodide are as shown in Table 1.

[0133]

[0134] Next, the surface free energy γS of the release layer surface was calculated from the values ​​of γSD, γSP, and γSH obtained above using the following formula: γS=γSD+γSP+γSH

[0135] (2) Coating uniformity of release layer The release film was cut into an A4 size, and the release layer surface was visually observed using a fluorescent lamp and a halogen light. The number of aggregated coating defects (number per A4 size) was compared and evaluated according to the following criteria: ○: 3 or less coating defects △: 3 to 5 coating defects ×: 6 or more coating defects

[0136] (3) Ceramic sheet peelability Barium titanate (BaTiO ３100 parts by weight of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.), 7 parts by weight of dioctyl phthalate, and 3 parts by weight of dispersant (DISPERBYK-103, manufactured by BYK-Chemie Co., Ltd.) were added to a mixed solvent of toluene:ethanol = 1:1 (volume ratio) and dispersed using a ball mill to prepare a slurry. This slurry was uniformly coated on the release layer of a release film so that the thickness after drying would be 2 μm, and then dried to form a ceramic sheet. The release film on which the ceramic sheet was formed was cut into 30 mm x 80 mm to prepare a test piece. Next, the ceramic sheet was peeled using a tensile tester at a peel angle of 180° and a peel speed of 10 m / min, and the peel strength was measured. The peel strength of the ceramic sheet was judged based on the following indicators. ◎: Peel strength is less than 1 mN / mm ○: Peel strength is 1 mN / mm or more and less than 1.5 mN / mm △: Peel strength is 1.5 mN / mm or more and less than 2.0 mN / mm ×: Peel strength is 2.0 mN / mm or more

[0137] (4) Rub-off test (adhesion) of release layer The release surface of the release film was rubbed with a thumb at a load of about 500 gf 10 times, and an adhesive tape (manufactured by Nitto Denko Corporation, product name "31B tape") was stuck to the rubbed surface to check for silicone detachment at that point. The peeling state of the adhesive tape was checked and evaluated according to the following criteria: ○: When the adhesive tape was peeled off, the peeling change was less than 1.5 times; △: When the adhesive tape was peeled off, the peeling change was 1.5 times or more but less than 2 times; ×: When the adhesive tape was peeled off, the peeling change was 2 times or more.

[0138] (5) Recyclability Evaluation Recyclability was evaluated by counting the number of particles with a maximum diameter of 50 μm or more, magnifying the size and number of particles contained in the film by 20 times using a universal projector. The measurement area was 0.05 m. ２ It was decided.

[0139] Good: 5 foreign objects / 0.05m ２ Less than 5-10 foreign objects / 0.05m, no problem in use. ２ Less than 10 foreign objects / 0.05m, slightly affects flatness, but can be used for limited purposes. ２ As a result, flatness is affected and the product cannot be used.

[0140] (6) Number Average Molecular Weight: The number average molecular weight was measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0141] (7) Thickness of the Release Layer After cutting the release film into small triangular pieces, a 2 nm thick Pt (platinum) layer was formed on the surface of the release layer by coating. The obtained sample was fixed in a multiaxial embedding capsule, embedded in epoxy resin, and sliced ​​perpendicular to the film surface using a microtome ULTRACUT-S to obtain an ultrathin sample with a thickness of 50 nm. The obtained ultrathin sample was then mounted on a grid and steam-stained with 2% osmic acid at 60 °C for 2 hours. Using the ultrathin sample after steam staining, the film cross section was observed using a transmission electron microscope LEM-2000 at an accelerating voltage of 100 kV, and the thickness of the release layer was measured. Measurements were performed at 10 random points, and the average value was taken as the thickness of the release layer (unit: nm).

[0142] (Alkenyl Group-Containing Silicone (A-1)) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo, device name "Ultra Planetary Mixer"), raw materials consisting of 95% by mass of silicone oil having a number average molecular weight of 3,000, in which a2 is 40 mol%, b2 is 5 mol%, c2 is 20 mol%, and d1 is 35 mol% of general formulas (II) and (III), and 5% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "LEOCOL TD-90") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-1) with a solids content of 50% by mass. The stirring speed and stirring time during emulsification were adjusted to an average emulsion particle size of 180 nm. In each example, a silicone oil in which R1 in general formulas (II) and (III) is a vinyl group or a methyl group and Y1 is represented by general formula (III) was used.

[0143]

[0144]

[0145] (Alkenyl Group-Containing Silicone (A-2)) Using an emulsifier capable of stirring the entire container (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer"), 96% by mass of silicone oil having a number average molecular weight of 6,000, in which a2 of general formula (II) and (III) is 35 mol%, b2 is 7 mol%, c2 is 20 mol%, and d1 is 38 mol%, and 4% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "Leocol TD-90") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-2) with a solids content of 50% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 185 nm by adjusting the stirring speed and stirring time during emulsification.

[0146] (Alkenyl Group-Containing Silicone (A-3)) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), 96% by mass of silicone oil having a number average molecular weight of 10,000, in which a2 of general formula (II) and (III) is 30 mol%, b2 is 10 mol%, c2 is 30 mol%, and d1 is 30 mol%, and 4% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "Leocol TD-90") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-3) with a solids content of 50% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 190 nm by adjusting the stirring speed and stirring time during emulsification.

[0147] (Alkenyl Group-Containing Silicone (A-4)) Using an emulsifier capable of stirring the entire container (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer"), 97% by mass of silicone oil having a number average molecular weight of 500, in which a2 of general formula (II) and (III) is 10 mol%, b2 is 20 mol%, c2 is 30 mol%, and d1 is 40 mol%, and 3% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "Leocol TD-90") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-4) with a solids content of 50% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 175 nm by adjusting the stirring speed and stirring time during emulsification.

[0148] (Alkenyl Group-Containing Silicone (A-5)) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), 94% by mass of silicone oil having a number average molecular weight of 15,000, in which a2 of general formula (II) and (III) is 30 mol%, b2 is 10 mol%, c2 is 40 mol%, and d1 is 20 mol%, and 6% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "Leocol TD-90") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-5) with a solids content of 50% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 195 nm by adjusting the stirring speed and stirring time during emulsification.

[0149] (Alkenyl Group-Containing Silicone (A-6)) Using an emulsifier capable of stirring the entire container (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer"), 92% by mass of silicone oil having a number average molecular weight of 20,000, in which a2 of general formula (II) and (III) is 10 mol%, b2 is 30 mol%, c2 is 30 mol%, and d1 is 30 mol%, and 8% by mass of polyoxyethylene tridecyl ether (manufactured by Lion Specialty Chemicals Co., Ltd., trade name "Leocol TD-90") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (A-3) with a solid content of 50% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 210 nm by adjusting the stirring speed and stirring time during emulsification.

[0150] (Si—H group-containing silicone (B-1) having a phenyl group) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), a1 of the general formula (I) is 60 mol%, b1 is 23 mol%, c1 is 11 mol%, and the number average molecular weight is 2,800. 95% by mass of silicone oil, and 5% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "Emulgen 109P") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (B-1) with a solid content of 40% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 180 nm by adjusting the stirring speed and stirring time during emulsification.

[0151]

[0152] (Si—H group-containing silicone (B-2) having a phenyl group) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), a1 of the general formula (I) is 50 mol%, b1 is 30 mol%, c1 is 20 mol%, and the number average molecular weight is 4,000 94% by mass of silicone oil, and as a surfactant, polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "Emulgen 109P") 6% by mass of raw materials were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (B-2) with a solid content of 40% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 190 nm by adjusting the stirring speed and stirring time during emulsification.

[0153] (Phenyl group-free Si—H group-containing silicone (C-1)) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), 96% by mass of silicone oil in which a3 in the general formula (IV) is 42 mol%, b3 is 56 mol%, and the number average molecular weight is 4,500, and 4% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "Emulgen 109P") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (C-1) with a solid content of 40% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 200 nm by adjusting the stirring speed and stirring time during emulsification.

[0154]

[0155] (Phenyl group-free Si—H group-containing silicone (C-2)) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), a3 of the general formula (IV) is 60 mol%, b3 is 40 mol%, and the number average molecular weight is 9,000. 94% by mass of silicone oil, and 6% by mass of polyoxyethylene lauryl ether (manufactured by Kao Corporation, trade name "Emulgen 109P") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample (C-2) with a solid content of 40% by mass. In addition, the emulsion particle size was adjusted to an average particle size of 210 nm by adjusting the stirring speed and stirring time during emulsification.

[0156] Aqueous Coating Composition Production Example 1 An aqueous coating composition was obtained by mixing the alkenyl group-containing silicone (A-3), the Si—H group-containing silicone having a phenyl group (B-1), and water in the proportions shown in Table 2 to a solids concentration of 4 mass %. At this time, 0.01 mass % of a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-PM-10A) and 150 ppm of a crosslinking reaction inhibitor (1-ethynylcyclohexanol) were mixed relative to the total weight of the aqueous coating composition.

[0157] <Aqueous Coating Composition Production Examples 2 to 22> Aqueous coating compositions were obtained in the same manner as in Production Example 1, except that the ingredients were mixed to the types and ratios shown in Table 2.

[0158] Example 1 Polyethylene terephthalate ([η] = 0.64 dl / g, Tg = 78°C) containing 0.1% by mass of calcium carbonate particles with an average particle size of 0.6 µm was melted in an extruder, passed through a filter with a filtration accuracy of 10 µm, extruded from a die, and cooled on a cooling drum in a conventional manner to form an unstretched film. The film was then stretched 3.3 times in the machine direction at 80°C, and the aqueous coating liquid (aqueous coating composition) obtained in Production Example 1 was uniformly coated using a roll coater so that the product thickness would be the release layer thickness shown in Table 2. The aqueous coating liquid used was one that had been prepared within 24 hours.

[0159] The coated film was then dried at 115°C, stretched 4.0 times in the transverse direction at 145°C, and further heat-set at 230°C for about 10 seconds to obtain a release film (thickness 25 µm) having a release layer formed by reacting and solidifying the aqueous coating liquid, and the evaluation was carried out. The evaluation results are shown in Table 2.

[0160] In addition, for each example and comparative example, parts of the release film that did not become products when the product rolls were collected, or parts of the release film that did not become products due to defects, etc., were crushed until the long diameter of the film pieces was approximately 5 mm or less, melted, and 40% by mass of the recycled raw material was used.

[0161] Examples 2 to 12 Release films were produced under the same conditions as in Example 1, except that aqueous coating compositions obtained in the same manner as in Production Examples 2 to 12 were used, and the above-mentioned evaluations were carried out. Detailed conditions and evaluation results are shown in Table 2A.

[0162] Comparative Examples 1 to 10 In Comparative Examples 1 to 10, release films were prepared under the same conditions as in Example 1, except that the alkenyl group-containing silicone (A) used had a molecular weight outside the range of the present invention, and the aqueous coating solutions obtained in Production Examples 13 to 22 were used, and the above-mentioned evaluations were carried out. Detailed conditions and evaluation results are shown in Table 2B.

[0163] In Example 1, release films were produced under the same conditions as in Example 1, except that the aqueous coating solutions obtained in Production Examples 6 to 10 were used instead of the aqueous coating solution obtained in Production Example 1, and the above-mentioned evaluations were carried out.

[0164]

[0165]

[0166] As shown in Table 2, in Examples 2, 5 to 7, and 10, the release layer's releasability and wettability were easily achieved, and release films were obtained with good coating uniformity and recyclability of the release layer, and good adhesion between the substrate and the release layer. Furthermore, Examples 1, 3, 4, 8, 9, 11, and 12 exhibited minimal physical properties. In contrast, Comparative Examples 1, 6, and 9, in which the main component silicone had a low molecular weight, tended to exhibit poor recyclability. Comparative Examples 2, 3, 5, 7, 8, and 10, in which the main component silicone had a high molecular weight, tended to exhibit poor coating uniformity and heavy ceramic sheet releasability. Comparative Example 4, which used only the phenyl-free Si—H group-containing silicone (C-1), exhibited heavy ceramic sheet releasability, poor adhesion, and poor recyclability.

[0167] The release film of the present invention has the advantages of easily achieving both releasability and wettability of the release layer, high coating uniformity of the release layer, good recyclability, and excellent adhesion, and is therefore of extremely high industrial utility.

Claims

1. A release film having a base film and a release layer formed by reacting and solidifying an aqueous coating composition, wherein the aqueous coating composition contains an alkenyl group-containing silicone (A) having a number average molecular weight of 1,000 or more and 14,000 or less, and a Si-H group-containing silicone (B) having a phenyl group, and the Si-H group-containing silicone (B) is represented by general formula (I). (In formula (I), a1 is a natural number selected from 1 to 50, b1 is a natural number selected from 1 to 50, and c1 is a natural number selected from 0 to 50.) 2. The release film according to claim 1, wherein the Si-H group-containing silicone (B) comprises a Si-H group-containing silicone having a number average molecular weight of 1,000 or more and 5,000 or less.

3. The release film according to claim 1, wherein the alkenyl group-containing silicone (A) is represented by the following general formula (II): (In the general formula (II), R1 may be the same or different and is an alkenyl group having from 2 to 8 carbon atoms, or a monovalent hydrocarbon group having from 1 to 16 carbon atoms, including an alkyl group or a phenyl group, provided that [SiO] ａ２ R1 bonded to the silicon atom represented by [SiO] is not an alkenyl group. ｃ２ At least one of R1 bonded to the silicon atom represented by [SiO] is the alkenyl group. ｂ２ Y1 bonded to the silicon atom represented by may be the same or different, and is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon group having 1 to 16 carbon atoms including an alkyl group or a phenyl group, or is represented by the following general formula (III), in which R1 in general formula (III) may be the same group as at least one R1 in general formula (II), and in general formula (III), R1 may be the same or different. When the total of a2, b2, c2, and all d2 is 100 mol%, a2 is 1 mol% or more, b2 is 0 mol% or more, c2 is 0 mol% or more, and d2 is 0 mol% or more.) 4. The release film according to claim 1, wherein the content of said Si—H group-containing silicone (B) is 3 to 30 parts by mass when the total of said alkenyl group-containing silicone (A) and said Si—H group-containing silicone (B) is 100 parts by mass.

5. The release film according to claim 1, wherein the release layer is formed by applying the aqueous coating composition to a substrate film before crystal orientation is completed, stretching the substrate film in at least one direction, and then heat-treating the substrate film to complete the crystal orientation.

6. The release film according to claim 1, wherein the base film is a polyester film.

7. The release film according to any one of claims 1 to 6, which is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.

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