Mold release film

Abstract

Provided is a mold release film configured so that, when peeling off a sheet-like molding after half cutting, a problem caused by adherence of the sheet-like molding to half-cut sections is unlikely to occur. This mold release film has a substrate film and a mold release layer. Regarding the mold release layer, in a micro slurry jet erosion test with a projection force for which the erosion rate is 0.019 μm / g with respect to polymethyl methacrylate resin, the erosion rate is 0.003 μm / g or more when a slurry, obtained by dispersing polygonal alumina particles having a mean particle diameter (D50) of 0.3 μm in water, is projected.

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 (e.g., Patent Documents 1 to 4).

[0003] 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 Si—H group, a platinum group metal catalyst, and an organic solvent.

[0004] Furthermore, as a technique suitable for a method of coating a substrate film during its stretching film formation (hereinafter referred to as "in-line coating"), Patent Document 3 proposes a release film in which a release layer is formed using an aqueous coating composition containing an alkenyl group-containing silicone and an Si-H group-containing silicone. Furthermore, as an example, the document discloses a release film in which a release layer is formed using an alkenyl group-containing silicone having a number average molecular weight of 25,000 and an Si-H group-containing silicone having a number average molecular weight of 4,500.

[0005] Furthermore, Patent Document 4 discloses a method for producing a cellulose acylate film by using SiO ４／２ A release film has been proposed in which a release layer is formed using an aqueous coating composition containing an alkenyl group-containing silicone having Q units represented by the formula: and an Si—H group-containing silicone. In addition, as an example, a release film has been disclosed in which a release layer is formed using an alkenyl group-containing silicone having Q units and a number average molecular weight of 25,000, and an Si—H group-containing silicone having a number average molecular weight of 4,500.

[0006] Thus, in the past, when forming a release layer, a relatively high molecular weight unsaturated group-containing polysiloxane has generally been used so that the helical structure of polydimethylsiloxane can be easily formed on the coating surface, and this point was also the case when an organic solvent-based coating composition was used (for example, Patent Documents 1 and 2).

[0007] On the other hand, there are also attempts to improve the releasability of a release film by measuring the hardness of the release layer of the release film and adjusting the hardness of the release layer. For example, in Patent Document 5, a release layer of a release film is separately prepared as a solid body, and its rubber hardness is measured to evaluate the release properties of the release film. However, this method evaluates a solid body of a release layer that has undergone a formation history different from the manufacturing process of an actual release film, resulting in an evaluation of the release properties that is different from that of an actual release film.

[0008] Furthermore, as a technique for directly measuring the hardness of a release layer, Patent Document 6 proposes a release film for producing ceramic green sheets, which uses a polyester film as a substrate, has a release coating layer on one surface, and has a coating elastic modulus of 2.0 GPa or more measured from the surface by a nanoindentation test on the release coating layer, and has a particle-containing easy-to-slip coating layer on the other surface of the substrate. In this case, a nanoindentation test is performed using a microhardness evaluation device with an indenter at a maximum indentation depth of 50 nm to measure the coating elastic modulus of the release coating layer.

[0009] Japanese Patent Application Laid-Open No. 2003-292894 Japanese Patent Application Laid-Open No. 2003-292895 Japanese Patent No. 6077327 Japanese Patent Application Laid-Open No. 2021-11081 Japanese Patent Application Laid-Open No. 2012-6213 International Publication No. WO2019 / 065214

[0010]

[0005] When a release film is used to produce a sheet-like molded product, the sheet-like molded product, such as a ceramic green sheet, formed on the surface thereof is often half-cut using a cutting blade, and then peeled off from the release film and transported to the next process. In this case, even if the release film has sufficient releasability, the sheet-like molded product may not be properly peeled off at the part where peeling begins (the half-cut part), which leads to a decrease in yield.

[0011] The inventors investigated the cause and found that when half-cutting is performed, the sheet-like molding is deformed by the cutting blade and adheres to the half-cut portion, resulting in increased adhesion between the sheet-like molding and the release film in some areas, making it difficult to peel off from the release film.

[0012] It has been found that in order to avoid this, it is not enough to simply increase the hardness of the release layer, but it is also important to improve the toughness against microscopic physical effects.

[0013] Therefore, an object of the present invention is to provide a release film which is less likely to cause problems due to adhesion to the half-cut portion when peeling off a sheet-like molding after half-cutting.

[0014] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by forming a release layer whose erosion obtained in a micro slurry jet erosion test falls within a specific range, and have thus completed the present invention. That is, the present invention includes the following features.

[0015] [1] A release film having a base film and a release layer, wherein the release layer has an average particle diameter (D ５０ 2.) A release film having an erosion rate of 0.003 μm / g or more when a slurry of 0.3 μm polygonal alumina particles dispersed in water is projected onto the release film.

[0016] [2] The release film according to [1], wherein the release layer is formed by reacting and solidifying a reactive curing composition containing a silicone compound.

[0017] [3] The reaction curable composition is SiO ４／２ The release film according to [2], comprising an alkenyl group-containing silicone having a Q unit represented by the formula:

[0018] [4] The release film according to any one of [1] to [3], wherein the base film is a polyester film.

[0019] [5] The release film according to any one of [1] to [4], wherein the release film is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.

[0020] According to the present invention, it is possible to provide a release film that is less likely to cause problems due to adhesion to the half-cut portion when peeling off a sheet-like molding after half-cutting.

[0021] Although the details of why such an effect is obtained are not clear, it is thought that the following can be said: A release layer that has a certain level of erosion obtained in a micro-slurry jet erosion test has low toughness (brittleness) against microscopic physical actions, and therefore the release layer is likely to break without being modified during half-cutting, and therefore it is thought that the sheet-like molding adhered to the release layer can be effectively prevented from deforming and adhering to the half-cut portion. This can also be understood from the fact that little sheet-like molding remains in the half-cut portion of the release film after the sheet-like molding is peeled off.

[0022] Photographs showing examples where the half-cutting property evaluation is "◯"; Photographs showing examples where the half-cutting property evaluation is "Δ"; Photographs showing examples where the half-cutting property evaluation is "×".

[0023] The release film of the present invention is a release film having a substrate film (hereinafter sometimes referred to as "substrate") and a release layer, and the release layer has an average particle diameter (D ５０ ) The erosion rate when a slurry of 0.3 μm polygonal alumina particles dispersed in water is projected onto the test piece is 0.003 μm / g or more. First, the micro slurry jet erosion test will be described.

[0024] [Micro Slurry Jet Erosion Test] The principle of this test is to measure the shape of the wear scars caused by particle collisions and evaluate the hardness or softness of a material based on the degree of wear, but by selecting the particles and conditions, it is possible to evaluate the toughness against microscopic physical effects. The erosion rate in the MSE test can be calculated, for example, by using a Micro Slurry Jet Erosion (MSE) tester (manufactured by Palmeso Co., Ltd., device name MSE-A) to collide particles with the measurement object, measuring the erosion depth using a stylus-type shape measuring device, and then calculating the erosion rate from the erosion depth relative to the amount of particle collisions.

[0025] Generally, particles used are made of resin, metal, ceramic, etc., and have an average particle size of 10 μm or less. For quantitative comparison between measurement samples, particles of specific sizes such as polygonal alumina, spherical alumina, spherical silica, etc. can be used.

[0026] The erosion rate of the release layer in the present invention in the MSE test is measured as follows: ５０ ) A slurry containing 1% by mass of 0.3 μm polygonal alumina particles was sprayed onto the surface of the release layer from a nozzle with a diameter of 0.3 mm, with a distance of 4 mm from the nozzle tip to the sample, to cut the release layer. The cut displacement relative to the amount of slurry sprayed, and the cut depth per 1 g of slurry, were expressed as the erosion rate (μm / g). In other words, a high erosion rate indicates that the cut material is brittle and weak, while a low erosion rate indicates that the cut material is flexible and strong.

[0027] The erosion rate of the release layer in the present invention in the MSE test is 0.003 μm / g or more, preferably 0.003 μm / g or more and 0.020 μm / g or less, and more preferably 0.004 μm / g or more and 0.010 μm / g or less.

[0028] A small erosion rate of the release layer is considered to be flexible and strong. When a ceramic green sheet laminated on the surface of the release layer is half-cut, if the release layer is flexible and strong, the ceramic green sheet may not be cut cleanly and may move along with the release layer, potentially resulting in stretching or residue of the ceramic green sheet at the half-cut portion. If stretching or residue occurs at the half-cut portion, this is undesirable because it prevents uniform peeling during the peeling process. In contrast, if the erosion rate is 0.003 μm / g or higher, the release layer is brittle when the ceramic green sheet is half-cut, allowing the cut portion to be cut cleanly and instantaneously. Therefore, stretching or residue of the ceramic green sheet does not occur, allowing uniform peeling during the peeling process and ensuring stable peeling. Furthermore, an erosion rate below the upper limit of the above-mentioned preferred range is preferable because it reduces the likelihood of detachment or cohesive failure of the release layer.

[0029] The erosion rate can be increased by, for example, adjusting the density of crosslinking points of the resin contained in the release layer, specifically by using an alkenyl group-containing silicone or Si—H group-containing silicone with a lower number average molecular weight, or by using an Si—H group-containing silicone with a high molar ratio of Si—H groups. Also, the erosion rate can be increased by, for example, adjusting the density of the branched structure of the resin contained in the release layer, specifically by using SiO ４／２ By using an alkenyl group-containing silicone having a Q unit represented by the formula: the erosion rate can be increased.

[0030] In the above case, the erosion rate can be adjusted so as not to be too high by adjusting the molecular weight of the alkenyl group-containing silicone or the Si—H group-containing silicone, adjusting the molar ratio of Q units, or adjusting the molar ratio of Si—H groups. It is also possible to reduce the erosion rate by adding a modifying resin that imparts flexibility to the release layer.

[0031] Furthermore, it is possible to increase the erosion rate by using a resin with a high crosslinking density in addition to the release component, or by using a substance that increases the number of reaction sites, such as a low molecular weight crosslinking agent or coupling agent.

[0032] [Release Layer] The release layer may contain a release agent component such as a silicone compound, a long-chain alkyl group-containing compound, a fluorine-containing compound, or an acrylic compound, and may further contain a binder component, a crosslinking agent, a modifying resin, a solvent, a catalyst, a surfactant, a crosslinking reaction inhibitor, a coupling agent, etc. As the release layer, from the viewpoints of good heat resistance and releasability and easy control of the surface free energy and erosion rate, it is preferable that the release layer is a release layer formed by reacting and solidifying a reactive curable composition containing a silicone compound. Furthermore, from the viewpoints of environmental consideration and safety, a release layer formed by reacting and solidifying an aqueous coating composition is more preferable.

[0033] The aqueous coating composition is a composition having two or more alkenyl groups in the molecule and SiO ４／２ and an Si—H group-containing silicone having two or more Si—H groups in the molecule and a number average molecular weight of 1,000 or more and 5,000 or less. Each of the constituent components will be described in detail below.

[0034] (Alkenyl Group-Containing Silicone) The alkenyl group-containing silicone is a silicone having two or more alkenyl groups in the molecule and SiO ４／２ and / or an alkenyl group-containing silicone having two or more alkenyl groups in the molecule and having a Q unit represented by the formula: ４／２ It is possible to use an alkenyl group-containing silicone that does not have a Q unit represented by the following formula:

[0035] The alkenyl group-containing silicone having Q units has two or more alkenyl groups and SiO ４／２Any compound having a Q unit represented by the formula (I) and a siloxane bond in the main chain may be used, but polyorganosiloxanes having alkenyl groups at the terminal and / or side chain are preferred. Furthermore, copolymers containing dialkylsiloxane units or alkylphenylsiloxane units are preferred because they exhibit release properties while making it easy to adjust the amount of alkenyl groups in one molecule. The terminal silicon atom preferably has an alkenyl group, but may also have a trialkylsilane structure such as trimethylsilane.

[0036] The alkenyl group-containing silicone without Q units may be any compound as long as it has two or more alkenyl groups in the molecule and a siloxane bond in the main chain, but polyorganosiloxanes having alkenyl groups at the terminal and / or side chain are preferred.In addition, copolymers containing dialkylsiloxane units or alkylphenylsiloxane units are preferred because they can easily adjust the amount of alkenyl groups in one molecule while exhibiting release properties.The terminal silicon atom preferably has an alkenyl group, but may also be a trialkylsilane structure such as trimethylsilane.

[0037] In any alkenyl group-containing silicone, the alkenyl group may be introduced at one end, both ends, or a side chain, but is preferably introduced at at least one end, and more preferably introduced at both ends of the main chain. Two or more alkenyl groups are present in the molecule, preferably 2 to 20, and more preferably 2 to 10.

[0038] In the case of an alkenyl group-containing silicone having Q units, SiO ４／２ The content of Q units represented by the formula (1) is preferably 0.5 mol% or more and 30 mol% or less, and more preferably 0.5 mol% or more and 20 mol% or less, when all silicon atoms including the terminals in the molecule are taken as 100 mol%. When the content of Q units is 0.5 mol% or more, it is easy to form a dense release layer with high cohesive strength, and it is easy to achieve both releasability and wettability of the release layer. When the content of Q units is 30 mol% or less, it is easy to prevent the structure from becoming too dense and to prevent the coating film from becoming brittle.

[0039] Examples of alkenyl group-containing silicones include organopolysiloxanes represented by the following general formula (I).

[0040]

[0041] (In general formula (I), R １ are the same or different alkenyl groups having 2 to 8 carbon atoms, or monovalent hydrocarbon groups having 1 to 16 carbon atoms including an alkyl group or an aryl group, and [SiO] ｂ１ R bonded to a silicon atom represented by １ At least one of R is an alkenyl group having 2 to 8 carbon atoms; ２ are monovalent hydrocarbon groups containing 1 to 16 carbon atoms, including an alkyl group or an aryl group, which may be the same or different, and Y １ may be the same or different and are represented by general formula (Ia).

[0042]

[0043] (In general formula (Ia), R １ is R in general formula (I). １ and may be the same or different.) Y １ In the entire general formula (I) containing Y, when all silicon atoms including the terminals are taken as 100 mol%, a1 is 50 mol% or more and 98 mol% or less, b1 is 0 mol% or more and 10 mol% or less, c1 is 0 mol% or more and 30 mol% or less, and d1 is 0 mol% or more and 50 mol% or less. １ In the entire general formula (I) including １ where at least two of the groups are alkenyl groups having 2 to 8 carbon atoms.) In addition, when c1 is 0 mol % in general formula (I), that is, when the alkenyl group-containing silicone has no Q units, an example of the alkenyl group-containing silicone is an organopolysiloxane represented by the following general formula (I'):

[0044]

[0045] [SiO] ａ１ R bonded to a silicon atom represented by ２is a monovalent hydrocarbon group containing an alkyl group or an aryl group, but is preferably a monovalent hydrocarbon group having 1 to 16 carbon atoms selected from alkyl groups or aryl groups, more preferably a methyl group or a phenyl group, and even more preferably a methyl group.

[0046] [SiO] ｂ１ R bonded to a silicon atom represented by １ is a monovalent hydrocarbon group containing an alkenyl group having from 2 to 8 carbon atoms, or an alkyl group or an aryl group, and at least one of them may be an alkenyl group having from 2 to 8 carbon atoms, but is preferably an alkenyl group having from 2 to 8 carbon atoms, or a monovalent hydrocarbon group having from 1 to 16 carbon atoms selected from an alkyl group or an aryl group. １ When is a hydrocarbon group other than an alkenyl group, it is more preferably a methyl group or a phenyl group, and even more preferably a methyl group.

[0047] [SiO] ｄ１ R bonded to a silicon atom represented by １ R may be an alkenyl group having from 2 to 8 carbon atoms, or a monovalent hydrocarbon group containing an alkyl group or an aryl group, but is preferably an alkenyl group having from 2 to 8 carbon atoms, or a monovalent hydrocarbon group having from 1 to 16 carbon atoms selected from an alkyl group or an aryl group, and more preferably a monovalent hydrocarbon group having from 1 to 16 carbon atoms selected from an alkyl group or an aryl group. １ When is a hydrocarbon group other than an alkenyl group, it is more preferably a methyl group or a phenyl group, and even more preferably a methyl group.

[0048] R at both ends of the main chain １ Also [SiO] ｂ１ R bonded to a silicon atom represented by １ However, a preferred structure is an alkenyl group having 2 to 8 carbon atoms, and a terminal alkenyl group is particularly preferred because it causes relatively little steric structural hindrance when reacted with a Si—H group, and is therefore likely to improve releasability.

[0049] R bonded to the terminal silicon atom in general formula (Ia) １ Also [SiO]ｂ１ R bonded to a silicon atom represented by １ However, the preferred structure is an alkenyl group having 2 to 8 carbon atoms, which is preferable because it improves the cohesive strength of the release layer and improves the release properties of processing materials such as those that are mediated by organic solvents.

[0050] 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.

[0051] Y １ In the entirety of general formula (I) containing the formula (I), when all silicon atoms including the terminals are taken as 100 mol%, a1 is 50 mol% to 98 mol%, preferably 70 mol% to 98 mol%. Also, b1 is 0 mol% to 10 mol%, preferably 0 mol% to 5 mol%. c1 is 0.5 mol% to 30 mol%, preferably 0.5 mol% to 20 mol%. d1 is 0 mol% to 50 mol%, preferably 0 mol% to 30 mol%.

[0052] [SiO] ａ１ and [SiO] ｂ１ When the total of the structural units is 100 mol %, from the viewpoint of localizing the hydrocarbon group on the coating surface to improve releasability, [SiO] ａ１ The range of the structural units is preferably from 90 mol % to 100 mol %, and more preferably from 95 mol % to 100 mol %.

[0053] The number-average molecular weight of the alkenyl group-containing silicone is preferably 1,000 or more but less than 10,000, more preferably 3,000 or more but less than 10,000. If the number-average molecular weight is smaller than 1,000, the hydrocarbon groups tend to localize on the coating surface, making it easier to obtain sufficient releasability. On the other hand, if the number-average molecular weight is less than 10,000, the emulsification properties into aqueous coating compositions tend to be good, and uniform application also tends to be good.

[0054] (Si—H Group-Containing Silicone) The Si—H group-containing silicone may be any compound having two or more Si—H groups (i.e., two or more hydrogen atoms directly bonded to Si atoms) in the molecule and a siloxane bond in the main chain, but polyorganosiloxanes having Si—H groups in the side chain are preferred. Furthermore, copolymers containing dialkylsiloxane units or alkylphenylsiloxane units are preferred because they exhibit release properties while making it easy to adjust the amount of Si—H groups in one molecule. The terminal silicon atom may have a Si—H group, but is preferably a trialkylsilane structure such as trimethylsilane.

[0055] An example of the Si--H group-containing silicone is an organohydrogenpolysiloxane represented by the following general formula (II):

[0056]

[0057] (In general formula (II), R ３ are the same or different monovalent hydrocarbon groups containing an alkyl group or an aryl group and having 1 to 16 carbon atoms, and when a2 + b2 is 100 mol %, a2 is 30 mol % to 90 mol % and b2 is 10 mol % to 70 mol %.) [SiO] ａ２ A hydrogen atom (hydrogen group) is bonded to the silicon atom represented by R ３ is a monovalent hydrocarbon group containing an alkyl group or an aryl group, and is preferably a monovalent hydrocarbon group having 1 to 16 carbon atoms selected from alkyl groups or aryl groups.

[0058] [SiO] ｂ２ , and R bonded to the terminal Si atom ３ is a monovalent hydrocarbon group containing an alkyl group or an aryl group, and is preferably a monovalent hydrocarbon group having 1 to 16 carbon atoms selected from alkyl groups or aryl groups.

[0059] Which R ３Regarding the above, the number of carbon atoms in the alkyl group or aryl group is preferably smaller, since the steric structural hindrance is relatively small, and the crosslinking reaction is facilitated. This is also preferable from the viewpoint of fluidity and uniformity of the reaction structure in the release layer. For this reason, the alkyl group is preferably a methyl group, an ethyl group, a propyl group, a butyl group, etc., and the aryl group is preferably a phenyl group, a tolyl group, etc.

[0060] [SiO] ａ２ and [SiO] ｂ２ When the total of the structural units is 100 mol%, [SiO] ａ２ The range of the structural unit is preferably 30 mol % or more and 90 mol % or less, and more preferably 40 mol % or more and 80 mol % or less. [SiO] ａ２ When the content of the structural unit [SiO] is 30 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 good, which is preferable. ａ２ When the structural unit is 90 mol % or less, Si—H groups are less likely to remain in the release layer, the activity of the surface of the release layer is less likely to increase, and good releasability is maintained, which is preferable.

[0061] The number average molecular weight of the Si—H group-containing silicone in the present invention is preferably 1,000 or more and 5,000 or less, and more preferably 3,000 or more and 5,000 or less. 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 5,000 or less, the emulsification characteristics into the aqueous coating composition tend to be good, and the coating uniformity also tends to be good. In addition, the crosslinking reaction tends to proceed efficiently, the number of residual Si—H groups in the release layer decreases, and the releasability is good.

[0062] In the aqueous coating composition, the Si—H group-containing silicone is preferably contained in an amount of 1 part by mass to 50 parts by mass, more preferably 2 parts by mass to 40 parts by mass, and even more preferably 3 parts by mass to 30 parts by mass, per 100 parts by mass of the alkenyl group-containing silicone. When the content of the Si—H group-containing silicone is 1 part by mass or more, a sufficient number of crosslinking reaction sites are provided, which facilitates the formation of a dense crosslinked structure and improves the release layer properties, which is preferable. When the content of the Si—H group-containing silicone is 50 parts by mass or less, it is difficult for Si—H groups to remain in the release layer, which makes it difficult for the activity of the release layer surface to increase and maintains good releasability, which is preferable.

[0063] (Polyvinyl alcohol-based resin) When a modifying resin is used, it is preferable to use a polyvinyl alcohol-based resin as a modifying resin for adjusting surface free energy, etc. As the polyvinyl alcohol-based resin, polyvinyl alcohol or a copolymer thereof is used. Examples of polyvinyl alcohol copolymers include vinyl alcohol-vinyl acetate copolymers, vinyl alcohol-vinyl butyral copolymers, ethylene-vinyl alcohol copolymers, and polyvinyl alcohol-based polymers having silyl groups in the molecule, and among these, vinyl alcohol-vinyl acetate copolymers and ethylene-vinyl alcohol copolymers are preferred. When the polyvinyl alcohol-based resin is a copolymer, the repeating unit derived from vinyl alcohol is preferably 70 mol% or more and 100 mol% or less, more preferably 85 mol% or more and 99 mol% or less.

[0064] The degree of polymerization of the polyvinyl alcohol resin in the present invention can be expressed by the viscosity of a 4% by mass aqueous solution at 20°C, and the viscosity is preferably 5 mPa·s or more and 50 mPa·s or less. When the viscosity is within the above-mentioned range, miscibility in the aqueous coating composition is high, making it easier to obtain a more uniform release layer. In other words, when the viscosity is 5 mPa·s or more, the resin is less likely to flow within the coating film after the release layer is formed, which is preferable because it is less likely to deteriorate the release properties. When the viscosity is 50 mPa·s or less, the viscosity of the entire aqueous coating composition is less likely to increase, making it easier to apply uniformly.

[0065] Furthermore, polyvinyl alcohol resins can be mixed with silicone before emulsification, and can also be used as an emulsifier.

[0066] Typically, polyvinyl alcohol is obtained by polymerizing vinyl acetate to form polyvinyl acetate and then saponifying it, and the amount of saponification is expressed as the degree of saponification. In the present invention, the degree of saponification of the polyvinyl alcohol resin is preferably 85 mol% or more and 99 mol% or less. When the degree of saponification is within the above-mentioned numerical range, miscibility in the aqueous coating composition is high, making it easier to obtain a more uniform release layer. In particular, when the degree of saponification is 85 mol% or more, the adhesion to the substrate is improved while the miscibility with silicone is also improved. When the degree of saponification is 99% or less, the hydrophilicity of the release layer is not too high, the cohesive force of the release layer coating film is easily maintained, and cases where the adhesion of the release layer is deteriorated are less likely to occur.

[0067] As the polyvinyl alcohol resin, commercially available products can be used as they are, and specific examples of such commercially available products include Poval manufactured by Kuraray Co., Ltd. and Gohsenol manufactured by Mitsubishi Chemical Corporation.

[0068] When a polyvinyl alcohol-based resin is used in the release layer, it is preferably contained in an amount of 1% by mass or more and 20% by mass or less based on the release layer. A more preferred range is 1% by mass or more and 15% by mass or less, and an even more preferred range is 1% by mass or more and 10% by mass or less. When the content of the polyvinyl alcohol-based resin is within the above-mentioned numerical range, it is possible to more suitably achieve both the two properties of miscibility with silicone and adhesion between the substrate and the release layer. In other words, when the content of the polyvinyl alcohol-based resin in the release layer is 1% by mass or more, the stability of the silicone emulsion in the coating liquid is easily improved, and when it is 20% by mass or less, the release properties are less likely to deteriorate.

[0069] (Platinum-Based Catalyst) The crosslinking reaction between the alkenyl group-containing silicone and the Si—H group-containing silicone is an addition reaction, and in one embodiment, it is preferable to use a platinum-based catalyst to accelerate the reaction.

[0070] 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.

[0071] 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 and the Si—H group-containing silicone. 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 below 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 above 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.

[0072] (Aqueous Solvent) When an aqueous coating composition is used, the aqueous coating composition typically contains an aqueous solvent in addition to the alkenyl group-containing silicone and the Si—H group-containing silicone, and the aqueous solvent is preferably water. In one embodiment, an aqueous dispersion of an alkenyl group-containing silicone and an aqueous dispersion of an Si—H group-containing silicone are used to prepare the aqueous coating composition. As the aqueous dispersion of each silicone, an aqueous emulsion is preferably used.

[0073] The release layer is formed from such an aqueous emulsion, and is formed by applying an aqueous coating composition containing the aqueous emulsion (hereinafter sometimes abbreviated as "aqueous coating liquid"). By using an aqueous solvent in the aqueous coating liquid, the release layer can be formed without using explosion-proof equipment and recovery equipment that are required for organic solvents during the film formation process. If necessary, it is also possible to include a small amount of organic solvent.

[0074] (Other Components) When an aqueous coating composition is used, 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.

[0075] (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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] (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.

[0080] 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.

[0081] (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.

[0082] 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.

[0083] Preferred silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, and vinylmethyldimethoxysilane.

[0084] 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.

[0085] Furthermore, 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.

[0086] 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.

[0087] 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.

[0088] (Preparation of Silicone Water Dispersion) When an aqueous coating composition is used, 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 azihommixer, or an ultraplanetary mixer.

[0089] 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 200 nm or less, and more preferably 100 nm or more and 200 nm or less.

[0090] [Substrate Film] The substrate film in the present invention is not particularly limited, and examples thereof include sheets or films made of polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polycarbonate, polyethylene and polypropylene, polystyrene triacetyl cellulose, acrylic, polyimide, etc. Among these, films made of polyester are preferred from the viewpoints of excellent mechanical properties and heat resistance, and a good balance between these properties and price. The following explanation will be given taking polyester film as an example, but even when other resin films are used, the copolymerization components, blend components, additives, film production method, laminate structure, etc. are the same as those described below.

[0091] (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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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. This more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet. For example, a preferred embodiment is that the surface layer A substantially free of particles having a particle size of less than 1.0 μm also substantially free of particles having a particle size of 1.0 μm or more.

[0101] 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.

[0102] 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.

[0103] 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 at least inorganic particles and a binder on surface layer B to impart slip properties for winding the film into a roll.

[0104] 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 1,000 ppm or more and 15,000 ppm or less in total.

[0105] 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 1000 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 15000 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.

[0106] 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.

[0107] 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.

[0108] From the viewpoint of reducing pinholes, it is preferable that recycled raw materials 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.

[0109] 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.

[0110] 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.

[0111] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, or to prevent 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.

[0112] 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.

[0113] [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 a 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Here, polyester film before completion of crystal orientation includes unstretched film, uniaxially oriented film obtained by orienting unstretched film 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 also film that has been stretched and oriented at a low ratio in both the longitudinal and transverse directions (biaxially stretched film before final re-stretching in the longitudinal or transverse direction to complete orientation crystallization).

[0118] 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.

[0119] 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.

[0120] 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.

[0121] [Release Film Characteristics] In the present invention, the surface free energy of the release layer, as measured by the test method described below, is preferably in the range of 10 mN / m to 40 mN / m, more preferably 12 mN / m to 38 mN / m, even more preferably 14 mN / m to 36 mN / m, and particularly preferably 15 mN / m to 35 mN / m. If the surface free energy of the release layer 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 resin sheet coated on the surface of the release layer are unlikely to occur, and pinhole defects are also unlikely to occur.

[0122] [Uses] The release film of the present invention can be used as a process film used in the production of multilayer ceramic capacitors, the casting of resin sheets, etc. In particular, even when a thin 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.

[0123] 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.

[0124] (1) 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: ◎: No coating defects ○: 1 to 2 coating defects △: 3 to 5 coating defects ×: 6 or more coating defects

[0125] (2) 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 left to stand for 30 seconds. Similarly, the static contact angles of ethylene glycol and methylene iodide were measured, and the following simultaneous equations regarding 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.). (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.

[0126]

[0127] 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

[0128] (3) Erosion rate Average particle diameter (D ５０ ) 0.3 μm polygonal alumina particles (Micro Polished Alumina, manufactured by BUEHLER) were dispersed in water to prepare a slurry containing 1 mass% polygonal alumina particles based on the total mass of the slurry. A release film was fixed to the sample stage using a micro slurry jet erosion (MSE) tester (manufactured by Palmeso Co., Ltd., device name MSE-A). The projection distance of the nozzle for spraying the above slurry was set to 4 mm.

[0129] The nozzle diameter for projecting (spraying) the particles was set to 0.3 mmΦ, and the particles were collided with the surface of the release layer to cut the release layer. The spray strength at this time was determined based on the standard projection force, which was calculated in advance by cutting a polymethyl methacrylate resin (Kuraray Co., Ltd., Paraglass P, sheet thickness 2 mm) under the same experimental conditions, and the standard projection force was calculated from the cut displacement relative to the amount of slurry sprayed (i.e., the depth cut when 1 g of slurry was sprayed). The average particle diameter (D ５０ In this example, which used 0.3 μm polygonal alumina particles, the standard projection force was the projection force at which 0.019 μm / g of polymethyl methacrylate resin was removed. The erosion depth of the release layer was measured at this standard projection force. In the above tester, the projection force is adjusted by the projection air pressure, so once the projection force is determined, the projection air pressure and projection air volume are also determined.

[0130] The erosion depth was measured using a stylus surface profiler (manufactured by Kosaka Laboratory Co., Ltd., model PU-EU1, stylus tip R: 0.5 μm, load: 50 μN, measurement magnification: 50,000, measurement length: 4 mm, measurement speed: 0.1 mm / s). More specifically, tilt correction was first performed using reference areas A and B at both ends of the measurement length that were not worn. Next, the step from the reference regression line to the center C of the wear scar (average value of 50 μm width) was measured. Next, the difference between the step data at 0 g projection (untreated surface) and the step data at each projection amount was calculated to obtain the erosion depth. From the obtained projection amount-erosion depth data, the erosion rate (μm / g) was determined from the change in erosion depth when the slurry projection amount was between 0 g and 25 g.

[0131] (4) Evaluation of half-cutting property Barium titanate (BaTiO ３ 100 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical), 7 parts by mass of dioctyl phthalate, and 3 parts by mass of a dispersant (DISPERBYK-103, manufactured by BYK-Chemie) were added to a mixed solvent of toluene:ethanol = 1:1 (volume ratio), and dispersed using a ball mill to prepare a slurry.

[0132] This slurry was uniformly coated onto the release layer of a release film to a dry thickness of 2 μm, and then dried to form a ceramic green sheet. The release film with the ceramic sheet formed thereon was half-cut using a rotary die cutter (R.D.C (FB)-A4, manufactured by Tsukatani Cutting Machine Co., Ltd.) to a 16 mm x 32 mm square area from the ceramic green sheet side, approximately 3 μm deep from the release layer surface. The rotary die cutter blade had a double-edged 50° angle, a blade depth of 0.3 mm, and a blade height of 0.6 mm. The half-cut depth was adjusted by sandwiching polyester film of appropriate thickness between the rotary die cutter blade and the ceramic green sheet, and between the release film and the anvil roll. The cutting condition of the cut area was observed with an optical microscope (approximately 10x magnification) and evaluated as follows. Figures 1 to 3 show photographs of examples corresponding to the half-cut performance ratings of "Good" to "Poor." Good: No remaining ceramic green sheet was observed in the cut area. Δ: A very small amount of ceramic green sheet remains in the cut area. ×: A large amount of ceramic green sheet remains in the cut area.

[0133] (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 ◎: Number of foreign objects: 10 / 0.05m ２ Less than 10 foreign objects / 0.05m, no problem in use. ２ From the above, 30 pieces / 0.05m ２ Less than 30 foreign objects / 0.05m, slightly affects flatness, but does not pose a problem in use. ２ From the above, 100 pieces / 0.05m ２ Less than 100 foreign objects / 0.05m, usable for limited purposes. ２ As a result, the deformation of the cast surface is so noticeable that it cannot be used.

[0134] (6) Number Average Molecular Weight: The number average molecular weight was measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0135] (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).

[0136] [Example 1] Polyethylene terephthalate ([η] = 0.64 dl / g, Tg = 78°C) containing 0.25% 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 prepared within 24 hours.

[0137] The coated film was then dried at 105°C, stretched 4.7 times in the transverse direction at 150°C, and further heat-set at 235°C for approximately 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.

[0138] 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.

[0139] <Production Example 1> (Sample 1A) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Lab., device name "Ultra Planetary Mixer"), a1 in formula (1) is 100 mol%, b1 is 0 mol%, and the number average molecular weight is 9000. 95% by mass of silicone oil, and 5% by mass of polyoxyethylene tridecyl ether (manufactured by ADEKA Corporation, trade name "Adeka Toll TN-100") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample 1A 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.

[0140]

[0141] (Sample 2A) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo, device name "Ultra Planetary Mixer"), raw materials consisting of 94% by mass of silicone oil in which a2 in formula (2) is 50 mol % and b2 is 50 mol % and the number average molecular weight is 4000, and 6% 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 dispersion of Sample 2 with a solids content of 40% by mass. The emulsion particle size was adjusted to an average particle size of 170 nm by adjusting the stirring speed and stirring time during emulsification.

[0142]

[0143] (Water-based coating liquid) Water-based coating liquids were prepared so that the solid content mass of silicone for Sample 1A and Sample 2A was the blending amount shown in Table 2, and other components were as shown below. 5 mass% of the following coupling agent relative to the total mass of silicone, 50 ppm of the following platinum-based catalyst relative to the total mass of the solid content of Sample 1A and Sample 2A, and 100 ppm of the following crosslinking reaction inhibitor relative to the mass of the coating liquid were mixed, and the solid content concentration of the coating liquid was diluted with water to prepare a coating liquid having the target release layer thickness. Coupling agent: 3-glycidoxypropyltriethoxysilane (manufactured by JNC Corporation, trade name "Sila-Ace S510") Platinum-based catalyst: platinum-based catalyst emulsion (manufactured by Wacker GmbH, trade name "CATALYST EM440") Crosslinking reaction inhibitor: 1-ethynylcyclohexanol (manufactured by Alfa Lancaster) [Example 2] A release film was produced under the same conditions as in Example 1, except that the aqueous coating liquid was prepared using Sample 1B produced in Production Example 2 instead of Sample 1A in Example 1, and the above-mentioned evaluation was carried out. The results are shown in Table 2.

[0144] <Production Example 2> (Sample 1B) Using an emulsifier capable of stirring the entire container (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer"), a1 in formula (1) is 100 mol%, b1 is 0 mol%, and the number average molecular weight is 5000. 95% by mass of silicone oil, and 5% by mass of polyoxyethylene tridecyl ether (manufactured by ADEKA Corporation, trade name "Adeka Toll TN-100") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of Sample 1B 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.

[0145] [Example 3] A release film was produced under the same conditions as in Example 1, except that the aqueous coating liquid was prepared using Sample 1C produced in Production Example 3 instead of Sample 1A in Example 1, and the above-mentioned evaluations were carried out. The results are shown in Table 2.

[0146] <Production Example 3> (Sample 1C) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), a raw material consisting of 95% by mass of silicone oil in which a1 in formula (1) is 96 mol%, b1 is 4 mol%, and the number average molecular weight is 7000, and 5% by mass of polyoxyethylene tridecyl ether (manufactured by ADEKA Corporation, trade name "Adeka Tol TN-100") as a surfactant was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of Sample 1C 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.

[0147] [Example 4] A release film was produced under the same conditions as in Example 1, except that the aqueous coating liquid was prepared using Sample 1D produced in Production Example 4 instead of Sample 1A in Example 1, and the above-mentioned evaluations were carried out. The results are shown in Table 2.

[0148] <Production Example 4> (Sample 1D) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo Co., Ltd., device name "Ultra Planetary Mixer"), 95% by mass of silicone oil represented by 2 mol% of formula (A), 4 mol% of formula (B), 90 mol% of formula (C), 2 mol% of formula (D), and 2 mol% of formula (E), having a number average molecular weight of 8000, and 5% by mass of polyoxyethylene tridecyl ether (manufactured by ADEKA Corporation, trade name "Adeka Toll TN-100") as a surfactant, was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample 1D with a solid content of 45% 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.

[0149]

[0150] [Example 5] A release film was produced under the same conditions as in Example 4, except that when preparing the aqueous coating liquid in Example 4, the contents of Sample 1D and Sample 2A were changed as shown in Table 2, and the above-mentioned evaluation was carried out. The results are shown in Table 2.

[0151] Comparative Examples 1 and 2 Release films were produced under the same conditions as in Examples 4 and 5, except that the aqueous coating liquid obtained in Production Example 5 was used instead of the aqueous coating liquid obtained in Production Example 4, and the above-described evaluations were carried out. The results are shown in Table 2.

[0152] Production Example 5 (Sample 1E) Using an emulsifier capable of stirring the entire contents of a container (manufactured by N.P. Labo, device name "Ultra Planetary Mixer"), raw materials consisting of 96% by mass of silicone oil in which a1 in formula (1) is 97 mol % and b1 is 3 mol % and the number average molecular weight is 30,000, and 4% 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 1E with a solids content of 50% 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.

[0153] (Sample 2B) Using an emulsifier capable of stirring the entire container (manufactured by N.P. Labo, device name "Ultra Planetary Mixer"), raw materials consisting of 94% by mass of silicone oil in which a3 and b3 in formula (2) are 50 mol % and 50 mol %, and a number-average molecular weight of 8,000, and 6% 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 dispersion of Sample 2 with a solids content of 50% by mass. The emulsion particle size was adjusted to an average particle size of 180 nm by adjusting the stirring speed and stirring time during emulsification.

[0154] (Water-based Coating Liquid) Water-based coating liquids were prepared under the same conditions as in Production Example 1, except that the solid content mass of silicone in Sample 1E and Sample 2B was adjusted to the blending amounts shown in Table 2.

[0155]

[0156] As shown in Table 2, in Examples 1 to 5, the erosion rate was 0.003 μm / g or more, so the half-cutting property evaluation was good and problems due to adhesion to the half-cut portion were unlikely to occur when peeling off the sheet-like molding after half-cutting. In contrast, in Comparative Examples 1 and 2, the erosion rate was less than 0.003 μm / g, so despite the low surface free energy, the half-cutting property evaluation was poor and problems due to adhesion to the half-cut portion were likely to occur when peeling off the sheet-like molding after half-cutting.

[0157] In Examples 1 to 5, the surface free energy was an appropriate value, and the coating uniformity and recyclability were also good.

[0158] The release film of the present invention is less likely to cause problems due to adhesion to the half-cut portion when peeling off the sheet-like molded product after half-cutting, and is therefore easy to use as a material for various processes, is recyclable, and has extremely high industrial utility value.

Claims

1. A release film having a base film and a release layer, wherein the release layer has an average particle diameter (D) of 0.019 μm / g at a projection force that results in an erosion rate of 0.019 μm / g for polymethyl methacrylate resin in a micro slurry jet erosion test. ５０ 2.) A release film having an erosion rate of 0.003 μm / g or more when a slurry of 0.3 μm polygonal alumina particles dispersed in water is projected onto the release film.

2. The release film according to claim 1, wherein the release layer is formed by reacting and solidifying a reaction-curing composition containing a silicone compound.

3. The reaction-curable composition is SiO ４／２ The release film according to claim 2 , comprising an alkenyl group-containing silicone having a Q unit represented by the formula:

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

5. The release film according to any one of claims 1 to 4, wherein the release film is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.