Release film for resin sheet molding

Abstract

The present application aims to provide a release film which can form a resin sheet of an ultra-thin layer, particularly a ceramic green sheet of an ultra-thin layer, without defects by forming a release film having a release layer with particularly excellent smoothness and peelability. A resin sheet molding release film having a polyester film as a base material and a release layer, wherein the polyester film has a surface layer A substantially free of inorganic particles, and the release layer is formed on the surface layer A, and the release layer is a layer formed by curing a release layer-forming composition, and the release layer-forming composition contains a cationically curable polydimethylsiloxane (a), and the area surface roughness (Sa) of the release layer is 2 nm or less, and the number of protrusions of 10 nm or more in height present on the surface of the release layer is 200 / mm 2 The following.

Description

Technical Field

[0001] This invention relates to a release film for molding resin sheets, and more specifically, to a release film used in molding ultrathin resin sheets. Background Technology

[0002] Previously, release films, which used polyester film as a substrate and had a release layer stacked on it, were used as process films for molding resin sheets such as adhesive sheets, cover films, polymer films, and optical lenses.

[0003] The aforementioned release film is also used as a process film in the molding of ceramic blanks requiring high smoothness, such as those for multilayer ceramic capacitors and ceramic substrates. In recent years, with the miniaturization and increasing capacitance of multilayer ceramic capacitors, there has been a trend towards thinner ceramic blanks. The ceramic blank is formed by coating a slurry containing ceramic components such as barium titanate and binder resin onto the release film and then drying it. Multilayer ceramic capacitors are manufactured by laminating, pressing, firing, and coating external electrodes onto the ceramic blanks obtained by printing electrodes on the formed ceramic blanks and peeling them off from the release film.

[0004] When ceramic preforms are formed on the surface of a release layer on a polyester film substrate, minute protrusions on the release layer surface can affect the formed ceramic preform, leading to defects such as shrinkage cavities and pinholes. In recent years, with the development of thin-film ceramic preforms, there is a growing demand for ceramic preforms with a thickness of less than 1.0 μm, more specifically 0.2 μm to 1.0 μm. Therefore, the requirements related to the smoothness of the release layer surface have become more stringent. Furthermore, extremely small protrusions and foreign matter on the release layer can cause deformation of the formed ceramic preform, resulting in technical problems such as pinholes and sheet breakage during peeling.

[0005] Furthermore, with the development of thin-film ceramic sheets, the peelability when separating ceramic sheets from the release film has become increasingly important. If the peeling force is large or uneven, the following problems arise: damage to the ceramic sheet during the peeling process, resulting in sheet defects, uneven thickness, pinholes, sheet breakage, and other undesirable conditions. Therefore, it is also required to peel the ceramic sheet with a lower and more uniform force. In other words, to manufacture ultra-thin resin sheets, especially ceramic sheets, without defects, a release film with extremely high smoothness and excellent peelability is needed.

[0006] As release films with excellent smoothness and peelability, the following patent documents can be cited as examples. For instance, Patent Document 1 proposes a release film having a release layer whose main component is a free radical curable resin. Patent Document 2 proposes a release film with a structure in which a smoothing layer and a release layer are stacked. Patent Document 3 proposes a release film having a release layer whose main component is a cationic curable epoxy resin. Patent Document 4 proposes a release film having a release layer whose main component is a cationic curable polydimethylsiloxane.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5492352

[0010] Patent Document 2: Japanese Patent Application Publication No. 2015-164762

[0011] Patent Document 3: International Publication No. 2018 / 079337

[0012] Patent Document 4: Japanese Patent Application Publication No. 2016-079349 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] However, in the release film of Patent Document 1, since a release layer is provided for the substrate film with insufficient smoothness, there is a technical problem that the smoothness of the release layer is insufficient. Furthermore, the inventors conducted in-depth research and found that free radical curing type resins can cause poor curing due to oxygen inhibition, resulting in poor solvent resistance on the surface of the release layer. This leads to problems such as the release layer being eroded by organic solvents used during ceramic blank forming and internal electrode printing, resulting in poor peelability.

[0015] In the technical solution of Patent Document 2, thermosetting melamine resin is used in both the smoothing coating layer and the release coating layer, requiring high temperatures to promote the curing reaction. Therefore, the planarity of the release film may be damaged due to the heat during processing. Furthermore, since multiple processes are required for the smoothing coating layer and the release coating layer, not only can foreign matter be mixed into the release film, but scratches may also be generated in the release layer. These foreign matter and scratches can be transferred to the ceramic blank formed on the release layer, potentially causing defects.

[0016] Patent documents 3 and 4 propose the use of cationic curable resins for release layers to improve poor curing caused by oxygen inhibition and poor planarity caused by processing heat. However, in the release film of patent document 3, the lack of smoothness in the substrate film results in poor surface smoothness of the release layer. In addition, the release agent components disclosed in patent document 3 lack reactivity, have poor solvent resistance, and also have peelability issues.

[0017] In the release film of Patent Document 4, because the release layer uses liquid cationic curable polydimethylsiloxane resin as its main component, the resin may accumulate at unevenness in the substrate film and at protrusions such as oligomers present on the surface of the substrate film, potentially causing problems with planarity. Furthermore, the low crosslinking density of the release layer also leads to issues with peelability.

[0018] This invention was made against the backdrop of the technical problems of these prior art. That is, its object is to provide a release film that has a release layer with particularly excellent smoothness and peelability, and further, to provide a release film that can be used to form ultra-thin resin sheets, especially ultra-thin ceramic blanks, without defects.

[0019] Solution for solving the problem

[0020] In order to solve the above-mentioned technical problems, the inventors conducted in-depth research and found that the above-mentioned objectives can be achieved by using a release film having the following structure, thereby completing the present invention.

[0021] That is, the present invention comprises the following components.

[0022] [1] A release film for molding resin sheets, comprising a polyester film as a substrate and a release layer.

[0023] The polyester film has a surface layer A that is substantially free of inorganic particles.

[0024] The release layer is present on the surface layer A.

[0025] The release layer is a layer formed by curing a release layer composition.

[0026] The release layer forming composition comprises cationic curable polydimethylsiloxane (a),

[0027] The surface roughness (Sa) of the release layer is below 2 nm.

[0028] The number of protrusions with a height of 10 nm or more on the surface of the release layer is 200 per mm. 2 the following.

[0029] [2] In one embodiment, the maximum protrusion height (Sp) of the release layer is less than 20 nm, and the total number of protrusions with a height of 5 nm or more but less than 10 nm existing on the surface of the release layer, together with the number of protrusions with a height of 10 nm or more, is 1500 per mm. 2 the following.

[0030] [3] In one embodiment, the cationic cured polydimethylsiloxane (a) has at least one functional group selected from vinyl ether, oxetyl, epoxy, and alicyclic epoxy.

[0031] [4] In one embodiment, the content of cationic cured polydimethylsiloxane (a) in the release layer is 90 mg / m³. 2 the following.

[0032] [5] In one embodiment, the release layer forming composition further comprises a cationic curable compound (b-1) that does not have a silicone framework.

[0033] The cationic curable compound (b-1) has two or more alicyclic epoxy groups in its molecule, and the content of the cationic curable compound (b-1) is more than 80% by mass relative to the total 100 parts by mass of the cationic curable polydimethylsiloxane (a) and the cationic curable compound (b-1).

[0034] [6] In one embodiment, the release layer forming composition further comprises a cyclic siloxane compound (b-2) having an alicyclic epoxy group.

[0035] The cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups in its molecule, and the content of the cyclic siloxane compound (b-2) is more than 80% by mass relative to the total 100 parts by mass of the cationic cured polydimethylsiloxane (a) and the cyclic siloxane compound (b-2).

[0036] [7] In one embodiment, the release layer forming composition contains an organic solvent with an SP value (δ) of 14 or more and 17 or less, and the release layer forming composition contains said organic solvent with an SP value (δ) of 14 or more and 17 or less in an amount of 10% by mass relative to 100 parts by mass of the total weight of the release layer forming composition.

[0037] [8] In one embodiment, a release film is provided for manufacturing a resin sheet containing an inorganic compound.

[0038] [9] In one embodiment, the resin sheet containing the inorganic compound is a ceramic blank.

[0039]

[10] In one embodiment, a release film is provided for molding resin sheets with a thickness of 0.2 μm or more and 1.0 μm or less.

[0040] The effects of the invention

[0041] The release film for resin sheet molding of the present invention can improve the smoothness and peelability of the release layer, thereby suppressing the occurrence of defects in ultra-thin resin sheets, especially ceramic blanks. Detailed Implementation

[0042] The present invention will now be described in detail.

[0043] This invention relates to a release film for resin sheet molding, comprising a polyester film as a substrate and a release layer.

[0044] The polyester film has a surface layer A that is substantially free of inorganic particles.

[0045] A release layer is present on surface layer A.

[0046] The release layer is a layer formed by the curing of the release layer composition.

[0047] The release layer forming composition comprises cationic curable polydimethylsiloxane (a),

[0048] The surface roughness (Sa) of the release layer is below 2 nm.

[0049] The number of protrusions with a height of 10 nm or more on the surface of the release layer is 200 per mm. 2 the following.

[0050] Because of the excellent smoothness and peelability of the release layer, the present invention with this configuration can provide a uniform thickness without defects and suppress defects such as pinholes for resin sheets with a thickness of 0.2 μm to 1.0 μm or less.

[0051] Furthermore, the present invention achieves the following effects. In the present invention, since a release layer is provided on a substrate film with sufficient smoothness, the smoothness of the release layer is also ensured. Further, the present invention, in the release layer, can suppress poor curing caused by oxygen inhibition and can achieve high cross-linking of the release layer. The present invention, which achieves this effect, for example, can improve the solvent resistance of the release layer surface. By improving the solvent resistance of the release layer surface, it is possible to suppress the erosion of the release layer by organic solvents used during ceramic blank forming and internal electrode printing, and it can have high peelability.

[0052] Furthermore, in the present invention, for example, compared to a release layer made of thermosetting melamine resin, high temperatures are not required to promote the curing reaction. Therefore, it is possible to suppress the damage to the planarity of the release film due to heat during processing. In addition, in the manufacturing method of the present invention, by performing the coating process and drying process of the present invention, it is possible to suppress the aggregation of the release layer forming composition, and to obtain a release film having a release layer with extremely high smoothness.

[0053] More specifically, by coating a release layer forming composition containing a specified amount of cationic curable polydimethylsiloxane (a) onto a surface layer A of a substrate film that is substantially free of inorganic particles, and then curing it, a release layer with extremely high smoothness can be obtained.

[0054] Furthermore, by controlling the content of cationic curable polydimethylsiloxane (a) in the release layer to below a specified amount, it is possible to suppress the aggregation of cationic curable polydimethylsiloxane (a) into minute foreign matter and tiny protrusions from oligomers present in the substrate film during the processing of the release layer. While not limited to a specific theory for explanation, by increasing the first drying temperature (by strengthening drying), it is possible to prevent component (a) from aggregating into the fine protrusions caused by the original roll.

[0055] Furthermore, by suppressing poor curing caused by oxygen inhibition, improving the solvent resistance of the release layer surface, suppressing the incorporation of foreign matter into the release layer, and suppressing scratches on the release layer, it is possible to prevent damage to the ceramic blank or other demolded objects during peeling, as well as sheet deformation caused by the transfer of foreign matter. As a result, a release layer with excellent smoothness, hardness, peelability, and contamination prevention against the demolded layer can be obtained.

[0056] Furthermore, during the drying of the organic solvent contained in the release layer forming composition, the cationic-curable polydimethylsiloxane (a) becomes less prone to aggregation, resulting in a release layer with excellent smoothness. Details will be described later.

[0057] In another embodiment of the present invention, a method for manufacturing a release film for molding resin sheets is provided, comprising the following steps.

[0058] The coating process involves coating a release layer onto the surface layer A of a polyester film having a surface layer A to form a composition, wherein...

[0059] Surface layer A is a layer that does not actually contain inorganic particles.

[0060] The release layer forming composition comprises cationic curable polydimethylsiloxane (a);

[0061] The drying process involves heating and drying the polyester film coated with the release layer to form the composition.

[0062] The heating and drying process includes a first drying step and a subsequent second drying step.

[0063] The drying temperature T1 in the first drying process is higher than the drying temperature T2 in the second drying process;

[0064] The photocuring process involves irradiating the release layer with active energy rays after the drying process, causing the release layer to solidify.

[0065] In the manufacturing method of the present invention, in particular by specifying the manufacturing conditions for processing the release layer, a release layer with high smoothness can be formed. Examples include controlling the coating amount of the release layer forming composition, the organic solvent content, the drying time, and the drying temperature. By manufacturing the release film under the conditions of the present invention, the aggregation of cationic curable polydimethylsiloxane (a) contained in the release layer forming composition can be suppressed, resulting in a release layer with excellent smoothness. Details will be described later.

[0066] (Polyester film)

[0067] The polyester used to form the polyester film, which serves as the substrate of this invention, is not particularly limited. A polyester formed by film molding from a polyester commonly used as a substrate for release films can be used. Crystalline linear saturated polyesters formed from aromatic diacids and glycols are preferred, such as polyethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, polyethylene terephthalate, polyethylene terephthalate, or copolymers with components of these resins as the main components are more suitable. Polyester films formed from polyethylene terephthalate are particularly suitable. The repeating unit of polyethylene terephthalate in polyethylene terephthalate is preferably 90 mol% or more, more preferably 95 mol% or more. Other dicarboxylic acid components and glycols may also be copolymerized in small amounts. From a cost perspective, polyethylene terephthalate made solely from terephthalic acid and ethylene glycol is preferred. Furthermore, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizing agents, can be added to the extent that they do not impair the effect of the film of the present invention. Based on reasons such as the difference in biaxial elastic modulus, the polyester film is preferably a biaxially oriented polyester film.

[0068] The intrinsic viscosity of the aforementioned polyester film is preferably 0.50 to 0.70 dl / g, more preferably 0.52 to 0.62 dl / g. When the intrinsic viscosity is 0.50 dl / g or higher, a large amount of breakage will not occur during the stretching process, which is therefore preferred. Conversely, when the intrinsic viscosity is 0.70 dl / g or lower, the shearability is good when cut to the specified product width, and dimensional defects will not occur, which is also preferred. Furthermore, the raw material granules are preferably thoroughly vacuum dried.

[0069] It should be noted that, in this specification, the term "polyester film" refers to a polyester film having (with) a surface layer A. Furthermore, in this invention, the polyester film has a surface layer A that is substantially free of inorganic particles, and the release layer is present on the surface layer A.

[0070] It should be noted that, as mentioned in the specification, the polyester film further having (stacked) surface layer B is sometimes simply referred to as "polyester film".

[0071] The method for manufacturing the polyester film in this invention is not particularly limited, and conventionally used methods can be used. For example, the polyester can be melted in an extruder, extruded into a film, cooled with a rotary cooling drum to obtain an unstretched film, and then stretched. Biaxial stretching is preferred from the perspective of mechanical properties. The biaxially stretched film can be obtained by sequentially biaxially stretching a longitudinally or transversely uniaxially stretched film in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in both the longitudinal and transverse directions.

[0072] In this invention, the stretching temperature during polyester film stretching is preferably above the secondary transformation point (Tg) of the polyester. It is preferable to stretch the film by 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0073] The thickness of the aforementioned polyester film is preferably 12–50 μm, more preferably 15–38 μm, and even more preferably 19–33 μm. If the film thickness is 12 μm or more, it will not deform due to heat during film production, the processing of the release layer, or the molding of ceramic blanks, etc., which is preferable. On the other hand, if the film thickness is 50 μm or less, the amount of waste film after use will not become excessive, which is preferable in terms of reducing environmental impact.

[0074] The aforementioned polyester film can be a single layer or a multilayer consisting of two or more layers. The polyester film has a surface layer A that is substantially free of inorganic particles. For example, it can be a single layer of surface layer A or a multilayer structure having surface layer A and other layers, such as surface layer B described later.

[0075] In the case of a laminated polyester film consisting of two or more layers, it is preferable to have a surface layer B, which may contain particles, on the opposite side of the surface layer A, which is substantially free of inorganic particles. As a laminated structure, if the layer on the side coated with the release layer is designated as surface layer A, the layer on its opposite side is designated as surface layer B, and the remaining core layers are designated as layer C, then the layer structure in the thickness direction can be a laminated structure of release layer / A / B, or release layer / A / C / B, etc. Of course, layer C can also be a multi-layered structure. Furthermore, surface layer B may not contain particles. In this case, to impart slidability for winding the film into a roll, it is preferable to provide a coating containing particles and an adhesive on surface layer B.

[0076] In the polyester film of this invention, surface layer A, located on the surface of the coating release layer, is substantially free of inorganic particles. Because surface layer A is substantially free of inorganic particles, it can exhibit the following regional average surface roughness.

[0077] In this invention, the average surface roughness (Sa) of the area of ​​surface layer A is the same as the average surface roughness (Sa) of the area where the release layer is disposed, and the average surface roughness (Sa) of the area where the release layer is disposed is 7 nm or less. If Sa is 7 nm or less, the release layer laminated on surface layer A can also exhibit high smoothness, and pinholes and the like are less likely to occur during the molding of ultra-thin ceramic blanks laminated on the release layer. Furthermore, when the release layer is formed, protrusions on surface layer A caused by the aggregation of release layer components can be suppressed, and the deterioration of the smoothness of the release layer surface can be prevented.

[0078] The smaller the average surface roughness (Sa) of the surface layer A region, the better; it can be 0.1 nm or more. In one embodiment, the average surface roughness (Sa) of the surface layer A region is 0.1 nm or more and 7 nm or less, for example, 0.5 nm or more and 5 nm or less, or 0.5 nm or more and 4 nm or less. Within such a range, the smoothness of the release layer can be improved, and the occurrence of pinholes and the like can be suppressed during the molding of stacked ultrathin ceramic blanks. Furthermore, during the formation of the release layer, protrusions on the surface layer A caused by the aggregation of release layer components can be suppressed, and the deterioration of the smoothness of the release layer surface can be prevented.

[0079] In this invention, "substantially free of inorganic particles" means a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when inorganic elements are quantified using fluorescence X-ray analysis. This is because even without actively adding inorganic particles to the film, there is still the possibility of contaminants from foreign matter, dirt adhering to the raw material resin or the production line and equipment during the film manufacturing process, mixing into the film.

[0080] In the polyester film substrate of this invention, a surface layer B may also be present on the side opposite to the surface where the release layer is disposed. Surface layer B preferably contains particles. By including particles, the film exhibits excellent slip properties and ease of air expulsion, resulting in excellent transportability and rollability. Particularly preferred are silica particles and / or calcium carbonate particles.

[0081] The total amount of particles contained in surface layer B is 1000 to 15000 ppm. At this time, the average surface roughness (Sa) of the thin film of surface layer B is, for example, 1 nm or more and 40 nm or less. More preferably, it is 5 nm or more and 35 nm or less. When the total amount of silica particles and / or calcium carbonate particles is 1000 ppm or more, and Sa is 1 nm or more, air can escape uniformly when the film is rolled into a roll, and the winding posture can be good, resulting in good planarity. Based on these characteristics, for example, when manufacturing ultrathin resin sheets, such as ceramic blanks, with a thickness of 0.2 μm or more and 1.0 μm or less, wrinkles and positional displacement of the rolled ceramic blank can be prevented, and a release film with excellent transportability, winding, and storage properties can be provided.

[0082] Furthermore, when the total amount of silica particles and / or calcium carbonate particles is less than 15,000 ppm and the Sa is less than 40 nm, the particles that also act as lubricants are less likely to aggregate and form large protrusions (e.g., protrusions with a height of more than 1 μm). Therefore, when manufacturing ultra-thin resin sheets, such as ceramic blanks, it is possible to suppress the occurrence of pinholes caused by winding and to provide resin sheets with stable quality.

[0083] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used as particles in surface layer B. Silica particles and / or calcium carbonate particles are preferred from the viewpoints of transparency and cost. Other usable inorganic particles include alumina-silica composite oxide particles and hydroxyapatite particles. Furthermore, heat-resistant organic particles include cross-linked polyacrylic acid particles, cross-linked polystyrene particles, and benzoguanamine particles. When using silica particles, porous colloidal silica is preferred. When using calcium carbonate particles, from the viewpoint of preventing particle shedding, lightweight calcium carbonate with a surface treatment using a polyacrylic acid-based polymer is preferred.

[0084] The average particle size of the particles added to 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 is 0.1 μm or more, the release film exhibits good sliding properties, which is therefore preferred. Furthermore, if the average particle size is 2.0 μm or less, deformation of surface layer A is suppressed, thereby preventing uneven thickness and pinholes in the ceramic blank.

[0085] The surface layer B described above may also contain particles of two or more different raw materials. Alternatively, it may contain particles of the same type but with different average particle sizes. Furthermore, the two or more different particles may have different average particle sizes within the aforementioned range. By containing two different types of particles, the unevenness formed in the surface layer B can be highly controlled, achieving a balance between slippage and smoothness, thus it is preferred.

[0086] In surface layer A, which serves as the layer on the side where the release layer is set, from the viewpoint of reducing pinholes, it is preferable not to use recycled materials to prevent the mixing of particles or impurities.

[0087] The thickness ratio of the surface layer A, which is the layer on the side where the release layer is set, is preferably 20% or more and 50% or less of the total thickness of the substrate film. If it is 20% or more, it is difficult for particles contained in the surface layer B, etc., to affect the film from the inside, and the average surface roughness Sa of the region can meet the above-mentioned range, so it is preferred. If it is 50% or less of the total thickness of the substrate film, it is possible to increase the proportion of recycled raw materials used in the co-extruded surface layer B and the aforementioned intermediate layer C, thereby reducing the environmental impact, so it is preferred.

[0088] Furthermore, from an economic point of view, 50-90% by mass of recycled materials from film scraps and plastic bottles can be used in layers other than surface layer A (surface layer B or the aforementioned intermediate layer C). In this case, the type, amount, particle size, and regional average surface roughness (Sa) of the lubricant contained in surface layer B preferably meet the above-mentioned ranges.

[0089] In addition, to improve the adhesion of subsequent coatings such as release layers and to prevent static electricity, a coating can be applied to the surface of surface layer A and / or surface layer B on the film before stretching or after uniaxial stretching during the film-forming process, or corona treatment can be performed. When a coating is applied to surface layer A, the coating is preferably substantially free of particles.

[0090] (release layer)

[0091] In this invention, a release layer is laminated on surface layer A. In this invention, the release layer is a layer formed by curing a release layer forming composition, and the release layer and the release layer forming composition contain at least cationic curable polydimethylsiloxane (a). The surface roughness (Sa) of the release layer region is less than 2 nm.

[0092] The number of protrusions with a height of 10 nm or more on the surface of the release layer is 200 per mm. 2 the following.

[0093] By giving the release layer such characteristics, it is possible to suppress the occurrence of pinholes in resin sheets, such as ceramic blanks, which require high smoothness, and to form resin sheets with uniform film thickness.

[0094] More specifically, the present invention, in the release layer, can suppress poor curing caused by oxygen inhibition and can achieve high cross-linking of the release layer. The present invention, which achieves such effects, can, for example, improve the solvent resistance of the release layer surface. By improving the solvent resistance of the release layer surface, it is possible to suppress the erosion of the release layer by organic solvents used during ceramic blank forming and internal electrode printing, and it can have high peelability.

[0095] Furthermore, the present invention does not require a high temperature of 130°C or higher to promote the curing reaction. Therefore, it is possible to suppress damage to the planarity of the release film caused by heat during processing. In addition, it is possible to suppress the occurrence of scratches caused by foreign matter mixing into the release film and release layer for resin sheet molding, and to suppress damage to the demolded body such as ceramic blanks caused by the transfer of foreign matter and scratches.

[0096] The average surface roughness (Sa) of the release layer area is less than 2 nm. Additionally, the number of protrusions with a height of 10 nm or more present on the surface of the release layer is 200 per mm. 2 The following conditions must be met for the surface of the release layer of the release film to prevent defects in the ceramic sheet coated and formed thereon. The average surface roughness (Sa) and the number of protrusions of 10 nm or more in the aforementioned area must meet the specified conditions.

[0097] If the surface roughness (Sa) of the region is less than 2nm and the number of protrusions with a height of more than 10nm is 200 / mm 2 The following method ensures that the ceramic sheet does not produce defects such as pinholes during the ceramic sheet forming process, resulting in a good yield, and is therefore preferred.

[0098] More preferably, the regional surface roughness (Sa) is 1.7 nm or less, for example, 1.6 nm or less, or 1.5 nm or less. In one embodiment, the regional surface roughness (Sa) is 1.3 nm or less. Alternatively, the regional surface roughness (Sa) can be 0.1 nm or more, or 0.2 nm or more.

[0099] On the other hand, in one embodiment, the number of protrusions with a height of 10 nm or more is 180 per mm. 2 For example, 170 pieces / mm 2 The following can also be 160 pieces / mm2 Below. In one embodiment, the number of protrusions with a height of 10 nm or more can be 120 per mm. 2 The number can be below 100 per mm². Additionally, protrusions with a height of 10 nm or more can have a count of 1 per mm². 2 The above, for example, can also be 10 pieces / mm. 2 above.

[0100] By ensuring that the number of protrusions with a height of 10nm or more is within the above range, defects such as pinholes will not occur in the ceramic sheet, and it can also achieve better and more even release properties.

[0101] Further preferred features include a surface roughness (Sa) of less than 1.0 nm and a height of more than 10 nm, with a protrusion count of 100 per mm. 2 the following.

[0102] The release layer with the regional surface average roughness (Sa) and number of protrusions of the present invention can exhibit extremely excellent smoothness.

[0103] In one embodiment, the maximum protrusion height (Sp) of the release layer is 20 nm or less. By keeping the maximum protrusion height within such a range, defects in the ceramic sheet can be further suppressed. More preferably, the maximum protrusion height (Sp) is 15 nm or less, and even more preferably 10 nm or less.

[0104] In one embodiment, the total number of protrusions with a height of 5 nm or more and less than 10 nm existing on the surface of the release layer, plus the number of protrusions with a height of 10 nm or more, is 1500 per mm. 2 The following is achieved by ensuring that the total number of protrusions with a height of 5 nm or more and less than 10 nm, and the total number of protrusions with a height of 10 nm or more on the release layer, is 1500 per mm. 2 The following method can further suppress defects in ceramic sheets and obtain a release layer with high smoothness, therefore it is preferred.

[0105] More preferably, the total number of protrusions with a height of 5 nm or more but less than 10 nm and the total number of protrusions with a height of 10 nm or more is 1000 per mm. 2 Below, for example, 500 pieces / mm is further preferred. 2 the following.

[0106] The release layer of the release film for resin sheet molding of the present invention is a layer formed by curing a release layer forming composition, which contains at least a cationic curable polydimethylsiloxane (a). The cationic curable polydimethylsiloxane (a) undergoes a cross-linking reaction through a cationic curing reaction, thus avoiding poor curing caused by oxygen inhibition, resulting in a release layer with excellent solvent resistance. Therefore, the release layer is not corroded by organic solvents used during ceramic sheet molding, internal electrode printing, etc., and a release layer with excellent peelability can be obtained.

[0107] Furthermore, the inventors have discovered that in a release layer containing cationic curable polydimethylsiloxane (a), the amount of cationic curable polydimethylsiloxane (a) is important for achieving a release layer with high smoothness.

[0108] Cationic cured polydimethylsiloxane (a) is preferably used in the release layer at a concentration of 90 mg / m³. 2 For example, 60mg / m 2 Below, 50mg / m 2 The following contains, more preferably, 40 mg / m² 2 The following, and more preferably, is 30 mg / m² 2 Below. Additionally, for example, cationic cured polydimethylsiloxane (a) can also be 20 mg / m³. 2 the following.

[0109] If the content of cationic cured polydimethylsiloxane (a) in the release layer is 50 mg / m 2 The following can suppress the aggregation of polydimethylsiloxane (a) in the process of forming the release layer, such as the drying process, and prevent the generation of a large number of protrusions outside the scope of the present invention, thereby achieving the effect of the present invention.

[0110] In one embodiment, the release layer and the release layer forming composition may also contain components other than cationic curable polydimethylsiloxane (a). In this case, judgments should not be based on specific theories, but in this invention, during the processing of the release layer, polydimethylsiloxane (a) can segregate on the surface of the release layer, if the content is 50 mg / m³. 2 The following materials are difficult to aggregate and can form a release layer with high smoothness.

[0111] The lower the content of polydimethylsiloxane (a) in this invention, the more difficult it is to aggregate, but if it is 0.1 mg / m³ in the release layer... 2 The above ensures the leveling properties of the release layer, resulting in a release layer with excellent coating appearance and high smoothness. Additionally, if the concentration is 0.1 mg / m³... 2The above properties also indicate excellent peelability, making it a preferred choice. For example, the content of polydimethylsiloxane (a) can also be 0.5 mg / m³. 2 above.

[0112] In this invention, the release layer forming composition comprises cationic curable polydimethylsiloxane (a). Furthermore, the release layer formed by curing the release layer forming composition contains a compound (cured product) derived from the cationic curable polydimethylsiloxane (a). In this specification, the compound derived from (a) present in the release layer is sometimes simply referred to as cationic curable polydimethylsiloxane (a).

[0113] In this invention, cationic curable polydimethylsiloxane (a) refers to a polydimethylsiloxane having cationic curable functional groups. Cationic curable functional groups are reactive functional groups exhibiting cationic curability; specifically, examples include vinyl ether groups, oxetyl groups, epoxy groups, and alicyclic epoxy groups. From a reactivity point of view, it is preferable to have at least one functional group selected from oxetyl groups, epoxy groups, and alicyclic epoxy groups, with alicyclic epoxy groups being the most preferred. Having such functional groups allows for the formation of a cross-linked structure through a cationic curing reaction, resulting in a release layer with excellent solvent resistance and excellent peelability; therefore, this is preferred.

[0114] The cationic curable polydimethylsiloxane (a) may have one or more cationic curable functional groups. For example, having two or more cationic curable functional groups makes the cationic curing reaction easier, resulting in a release layer with high crosslinking density, which is preferred. The location of the cationic curable functional group is not particularly limited; it is typically present on the side chains or at the ends of the polydimethylsiloxane. The structure of the polydimethylsiloxane can be either a linear or branched structure, and it can be used without problems even if it contains functional groups other than the cationic curable functional group.

[0115] Cationic curable polydimethylsiloxane (a) can be appropriately used in commercially available products. Examples include Silcolease (registered trademark) UV POLY200, UV POLY201, UV POLY215, UV RCA200, and UV RCA251 manufactured by Arakawa Chemical Industry Co., Ltd.; X-62-7622, ​​X-62-7629, X-62-7660, KF-101, KF-105, X-22-343, X-22-169AS, X-22-169B, X-22-163, X-22-173BX, X-22-173DX, and X-22-9002 manufactured by Shin-Etsu Chemical Industry Co., Ltd.; and UV9440E and UV9430 manufactured by Momentive Performance Materials Inc.

[0116] The weight-average molecular weight of the cationic curable polydimethylsiloxane (a) is preferably 1,000 to 500,000, more preferably 5,000 to 100,000. A weight-average molecular weight of 1,000 or higher facilitates the cationic curing reaction and provides excellent peelability, thus it is preferred. A weight-average molecular weight of 500,000 or lower results in a viscosity that is not too high, providing a release layer with excellent coatability and high planarity, thus it is also preferred.

[0117] In the release layer forming composition of the present invention, other resins may be included besides cationic curable polydimethylsiloxane (a). In this case, the film thickness of the release layer can be reduced. In the present invention, since the release layer is provided on the surface layer A of a substrate film that is substantially free of inorganic particles, a release layer with extremely high smoothness can be formed even if the film thickness of the release layer is relatively thin. In addition, since the film thickness of the release layer is relatively thin, the curing reaction is easier to carry out, processing can be performed at a higher speed, and the release layer can be obtained economically.

[0118] Furthermore, if the film thickness is thin, minute foreign matter present in the substrate film, demolding process, etc., will not be mixed into the demolding layer. Therefore, no protrusions caused by foreign matter will be generated on the surface of the demolding layer, and a demolding layer with a smooth surface as described above can be obtained.

[0119] When a release layer is formed by curing a composition with cationic curable polydimethylsiloxane (a) as the main component, the film thickness of the release layer is preferably 0.001 μm or more and less than 0.050 μm. A thickness of 0.001 μm or more results in excellent release properties and is therefore preferred. A thickness of less than 0.050 μm prevents the release layer from agglomerating into a smooth release layer and is also preferred.

[0120] It should be noted that, in this invention, when cationic curable polydimethylsiloxane (a) is the main component, the composition contains 50 or more, for example, more than 50 parts by mass, preferably 70 or more, for example, 80 or more parts by mass, of cationic curable polydimethylsiloxane (a) relative to 100 parts by mass of the resin solids component of the release layer; in one embodiment, it contains 90 or more parts by mass. Alternatively, the cationic curable polydimethylsiloxane (a) may be substantially included in all the resin solids component of the release layer.

[0121] In the release layer forming composition of the present invention, in addition to cationic curable polydimethylsiloxane (a), a cationic curable resin (b) may also be contained. In this case, (b) is a resin different from (a), and resin (b) is a substance that does not have a polydimethylsiloxane structure. Specifically, it is roughly divided into two types: cationic curable compounds (b-1) that do not have an organosilicon backbone and cyclic siloxane compounds (b-2) that have alicyclic epoxy groups.

[0122] In one embodiment, the release layer forming composition, in addition to containing cationic curable polydimethylsiloxane (a), further contains a cationic curable compound (b-1) that does not have an organosilicon backbone. Examples of the cationic curable compound (b-1) that does not have an organosilicon backbone include polymers and monomers having two or more cationic curable functional groups within their molecules and lacking an organosilicon backbone. Preferably, resins having two or more epoxy groups or alicyclic epoxy groups are preferred, and more preferably, resins having two or more alicyclic epoxy groups are preferred. For example, the number of alicyclic epoxy groups may also be six or less.

[0123] A release layer with excellent solvent resistance is formed by cross-linking through a cationic curing reaction using two or more alicyclic epoxy groups. Furthermore, since it also undergoes a cross-linking reaction with the polydimethylsiloxane (a) contained in the release layer, it exhibits excellent peelability and can suppress the transfer of polydimethylsiloxane (a) to the ceramic blank, making it preferable.

[0124] In one embodiment, since the release layer forming composition simultaneously comprises a cationic curable resin (b-1) without a silicone backbone and polydimethylsiloxane (a), a release layer with high smoothness can be achieved. By forming a release layer containing compound (b-1), fine irregularities, tiny foreign matter, oligomer protrusions, etc., present in the substrate film can be filled, resulting in an ultra-smooth release layer. Furthermore, since the curing reaction is carried out by ultraviolet light, a release layer with high smoothness is obtained. Although it should not be interpreted according to a specific theory, it can be speculated that during the drying process of the release layer forming composition during release layer processing, (b-1) and (a) are uniformly leveled, and after curing with improved flatness, a release layer with high smoothness can be obtained. In addition, in this invention, the polydimethylsiloxane (a) contained therein segregates on the surface of the release layer during the drying process, thus a release layer with excellent peelability can be obtained.

[0125] The cationic curable compound (b-1) without an organosilicon framework is preferably a low molecular weight monomer. Specifically, the number average molecular weight is preferably 200 or more and less than 5000, more preferably 200 or more and less than 2500, and even more preferably 200 or more and less than 1000. When the number average molecular weight is 200 or more, the boiling point does not decrease, and the cationic curable compound (b-1) will not volatilize during the drying process of the release layer forming composition during release layer processing, which is preferred. When the number average molecular weight is less than 5000, the crosslinking density of the release layer increases, and the solvent resistance is excellent, which is also preferred. In addition, since it can exist in a fluid liquid state during the drying process, it has excellent leveling properties and becomes an ultra-smooth release layer, which is also preferred.

[0126] Cationic curable compounds (b-1) without an organosilicon framework can be appropriately used commercially available products. Examples of compounds with alicyclic epoxy groups include CELLOXIDE 2021P, CELLOXIDE 2081, EPOLEAD GT401, and EHPE3150 manufactured by Daicel Corporation; HiREM-1 manufactured by Shikoku Chemical Co., Ltd.; and THI-DE, DE-102, and DE-103 manufactured by ENEOS Co., Ltd. Examples of epoxy-containing resins include DIC Corporation's EPICLON (registered trademark) 830, 840, 850, 1051-75M, N-665, N-670, N-690, N-673-80M, N-690-75M, and Nagase ChemteX Corporation's DENACOL (registered trademark) EX-611, EX-313, EX-321.

[0127] The content of the cationic curable compound (b-1) without an organosilicon framework is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to the total 100 parts by mass of the cationic curable polydimethylsiloxane (a) and cationic curable compound (b-1) in the release layer.

[0128] By including the cationic curable compound (b-1) at a content of 80% by mass or more as the main component in the release layer, a release layer with high crosslinking density and excellent peelability is obtained, which is therefore preferred. Furthermore, reducing the content of cationic curable polydimethylsiloxane (a) in the release layer can suppress the aggregation of components from polydimethylsiloxane (a) on the surface of the release layer during the drying process, thus preventing deterioration of planarity, which is also preferred. Although a higher content of cationic curable compound (b-1) results in a release layer with better smoothness, in order to include cationic curable polydimethylsiloxane (a) and ensure peelability, the cationic curable compound (b-1) is preferably 99.9% by mass or less.

[0129] In this invention, the release layer formed by curing the release layer composition contains a compound (cured product) derived from a cationic curable compound (b-1) that does not have a silicone framework. In this specification, the compound derived from (b-1) present in the release layer is sometimes simply referred to as a cationic curable compound (b-1) that does not have a silicone framework.

[0130] When the release layer forming composition comprises cationic curable polydimethylsiloxane (a) and cationic curable compound (b-1), the release layer has a high crosslinking density, resulting in a release layer with excellent solvent resistance and excellent peel strength, which is preferred. Furthermore, if cationic curable compound (b-1) is included, the film thickness of the release layer can be increased while maintaining the content of cationic curable polydimethylsiloxane (a) within a specified range, which is also preferred. By increasing the film thickness of the release layer, damage and minute unevenness present in the substrate film can be filled in, resulting in a smooth release layer as described above, which is also preferred.

[0131] When the release layer forming composition comprises cationic curable polydimethylsiloxane (a) and cationic curable compound (b-1), the film thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more results in a smooth release layer, which is preferred. A thickness of 1.0 μm or less allows for the production of a release film with excellent planarity and no curling, which is also preferred.

[0132] In one embodiment, the release layer forming composition may further contain a cyclic siloxane compound (b-2) having an alicyclic epoxy group. Examples of cyclic siloxane compounds (b-2) having an alicyclic epoxy group include substances such as those shown in the following structural formula (Chemical Formula 1) (in Chemical Formula 1, R...). 2(The alkyl group has 1 to 4 carbon atoms). Furthermore, the cationic curable compound (b-2) having a cyclic siloxane framework preferably has at least two alicyclic epoxy groups. If there are two or more alicyclic epoxy groups, the cationic curing reaction proceeds, resulting in a release layer with high crosslinking density, which is therefore preferred.

[0133] [Chemical Formula 1]

[0134]

[0135] By using a cyclic siloxane compound (b-2) having alicyclic epoxy groups, an ultra-smooth release layer is achieved for the same reasons as when using the cationic curable compound (b-1), which is therefore preferred. That is, it can fill in fine irregularities, minute foreign matter, oligomer protrusions, etc., present in the substrate film. Furthermore, since the curing reaction is carried out by ultraviolet light, during the drying process of the release layer forming composition during release layer processing, compound (b-2) and polydimethylsiloxane (a) are uniformly leveled, and curing is performed after the planarity is improved, thus obtaining an ultra-smooth release layer. Moreover, in this invention, since the polydimethylsiloxane (a) contained therein segregates on the surface of the release layer during the drying process, a release layer with excellent peelability can be obtained.

[0136] Since the cyclic siloxane compound (b-2) with alicyclic epoxy groups has good compatibility with the cationic curable polydimethylsiloxane (a), it is moderately mixed in the release layer and undergoes a crosslinking reaction with each other. Therefore, it becomes a release layer with excellent solvent resistance and excellent peelability, which is preferred. Furthermore, since the cyclic siloxane compound (b-2) has a cyclic siloxane structure, it has a rigid molecular framework, increasing the film hardness during curing, which is also preferred. By increasing the film hardness, the release layer becomes less prone to deformation when peeling off resin sheets, such as ceramic blanks, exhibiting good peelability. Furthermore, the release layer becomes less prone to scratches, and scratches on the release layer will not transfer to the resin sheet, such as the ceramic blank, causing adverse conditions, which is also preferred.

[0137] If the release layer forming composition contains a cyclic siloxane compound (b-2), the adhesion of the release layer to the substrate film is improved, which is preferred. Improved adhesion of the release layer can suppress scratches during the transport process, and furthermore, the release layer will not transfer during resin sheet peeling, which is also preferred.

[0138] In one embodiment, the cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups within its molecule. By having two or more alicyclic epoxy groups within its molecule, it undergoes a cross-linking reaction via cationic curing, resulting in a release layer with excellent solvent resistance. Furthermore, since it also undergoes a cross-linking reaction with the polydimethylsiloxane (a) contained in the release layer, it exhibits excellent peelability and can also suppress the transfer of polydimethylsiloxane (a) to the ceramic preform, making it preferable.

[0139] For example, cyclic siloxane compounds (b-2) have fewer than 6 alicyclic epoxy groups in their molecules.

[0140] Cyclic siloxane compounds (b-2) with alicyclic epoxy groups can be commercially available. Examples include X-40-2670 and X-40-2678 manufactured by Shin-Etsu Chemical Co., Ltd.

[0141] Relative to the total 100 parts by mass of cationic-cured polydimethylsiloxane (a) and cyclic siloxane compound (b-2) in the release layer, the content of cyclic siloxane compound (b-2) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. By setting the content of cyclic siloxane compound (b-2) to 80% by mass or more and using it as the main component in the release layer, a release layer with high crosslinking density and excellent peelability is obtained, which is therefore preferred. In addition, the content of cationic-cured polydimethylsiloxane (a) in the release layer can be reduced. In this invention, the aggregation of cationic-cured polydimethylsiloxane (a) on the surface of the release layer can be suppressed during the drying process, and the planarity is not deteriorated, which is therefore preferred. The higher the content of the cyclic siloxane compound (b-2), the better the smoothness of the release layer. For example, in order to contain cationic curable polydimethylsiloxane (a) and ensure peelability, the cyclic siloxane compound (b-2) is preferably 99.9% by mass or less.

[0142] In this invention, the release layer formed by curing the release layer composition contains a compound (cured product) derived from the cyclic siloxane compound (b-2). In this specification, the compound derived from the cyclic siloxane compound (b-2) present in the release layer is sometimes simply referred to as the cyclic siloxane compound (b-2).

[0143] When the release layer forming composition comprises cationic curable polydimethylsiloxane (a) and cyclic siloxane-based compound (b-2), the film thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more results in a smooth release layer, which is preferred. A thickness of 1.0 μm or less allows for the production of a release film with excellent planarity and no curling, which is also preferred.

[0144] In one embodiment, the release layer may simultaneously comprise a cationic curable resin (b-1) and a cyclic siloxane compound (b-2), wherein the total amount of the cationic curable resin (b-1) and the cyclic siloxane compound (b-2) relative to a total of 100 parts by mass of cationic curable polydimethylsiloxane (a), cationic curable compound (b-1), and cyclic siloxane compound (b-2) in the release layer may be 80% by mass or more and 99.9% by mass or less.

[0145] In this invention, a cationic curing reaction is required to form the release layer. Therefore, the release layer forming composition preferably contains an acid-generating agent (c). Additionally, compounds derived from the acid-generating agent (c) may be present in the release layer. Here, the compounds derived from the acid-generating agent (c) present in the release layer are sometimes simply referred to as acid-generating agent (c).

[0146] There are no particular limitations on the acid-generating agent used; any general acid-generating agent can be used. However, photo-acid-generating agents that generate acid under ultraviolet irradiation are preferred because they can suppress heat during processing and create a release layer with excellent planarity.

[0147] From a reactivity point of view, it is appropriate to use salts composed of ononium ions and non-nucleophilic anions as photoacid generators. Alternatively, organometallic complexes, such as iron aromatic complexes, carbocation salts, such as tropylium, anthracene derivatives, and phenols substituted with electron-withdrawing groups, such as pentafluorophenol, can also be used.

[0148] When using salts composed of onium ions and non-nucleophilic anions as photoacid-producing agents, onium ions can be, for example, iodonium, sulfonium, or ammonium. Organic groups used as onium ions can be triaryl, diaryl (monoalkyl), monoaryl (dialkyl), or trialkyl; benzophenone, 9-fluorene, or other organic groups can also be introduced. Non-nucleophilic anions are suitable for use as hexafluorophosphate, hexafluoroantimonate, hexafluoroborate, or tetra(pentafluorophenyl)borate. Additionally, tetra(pentafluorophenyl)gallium ions, anions obtained by replacing certain fluoride anions with perfluoroalkyl or organic groups, or other anionic components can be used.

[0149] The amount of photoacid-generating agent added is 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, relative to the total 100 parts by mass of cationic curable polydimethylsiloxane (a), cationic curable compound (b-1), and / or cyclic siloxane compound (b-2) in the release layer. It is even more preferably 1 to 5% by mass. By setting it to 0.1% by mass or more, the amount of acid generated will not become insufficient, leading to inadequate curing, which is preferred. Furthermore, by setting it to 10% by mass or less, the amount of acid generated becomes appropriate, which can suppress the amount of acid transferred to the ceramic blank to be formed, which is also preferred.

[0150] In this specification, the total of 100 parts by mass of cationic curable polydimethylsiloxane (a), cationic curable compound (b-1), and / or cyclic siloxane compound (b-2) in the release layer refers to the total solid content of cationic curable polydimethylsiloxane (a) and cationic curable resin (b). It should be noted that in a release layer that does not contain cationic curable resin (b), the weight of cationic curable polydimethylsiloxane (a) is equivalent to 100 parts by mass of the resin solid content in the release layer.

[0151] In one embodiment, the release layer forming composition contains an organic solvent with an SP value (δ) of 14 or more and 17 or less, and the release layer forming composition contains the aforementioned organic solvent with an SP value (δ) of 14 or more and 17 or less in an amount of 10% by mass relative to 100 parts by mass of the total weight of the release layer forming composition.

[0152] Organic solvents with an SP value (δ) of 14–17 exhibit excellent solubility for cationic curable polydimethylsiloxane (a). Therefore, even if the concentration of (a) in the release layer forming composition increases due to the drying of the organic solvent after the coating process, it can maintain a uniformly dissolved state, avoid aggregation, and achieve clean leveling, resulting in a smooth release layer.

[0153] In addition, if the content is 10% by mass or more, the cationic curable polydimethylsiloxane (a) can remain in a dissolved state for a long time during drying, so it will not aggregate during drying and thus deteriorate the smoothness, which is preferred.

[0154] Details of the aforementioned organic solvents with an SP value (δ) of 14 or higher and 17 or lower will be described later.

[0155] In this invention, additives such as adhesion enhancers and antistatic agents may be added to the release layer without hindering its effectiveness. Furthermore, to improve adhesion to the substrate, it is preferable to pretreat the polyester film surface before applying the release coating layer, such as by anchoring coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment.

[0156] For the release film obtained by the present invention, the peeling force when peeling off the ceramic blank is preferably 0.01 mN / mm or more and 2.0 mN / mm or less. More preferably, it is 0.05 mN / mm or more and 1.0 mN / mm or less. When the peeling force is 0.01 mN / mm or more, the ceramic blank will not float during transportation, which is preferred. When the peeling force is 2.0 mN / mm or less, the ceramic blank will not be damaged during peeling, which is also preferred.

[0157] The release film obtained by this invention uses a highly planarized substrate film, thus enabling a smooth surface even when the thickness of the release layer is 1.0 μm or less, further 0.5 μm or less, or further 0.3 μm or less. Therefore, it is possible to reduce the amount of solvent and resin used, making it environmentally friendly and enabling the inexpensive production of release films for ultrathin ceramic sheet forming.

[0158] (Method for manufacturing release film)

[0159] In another embodiment of the present invention, a method for manufacturing a release film for resin sheet molding is provided, comprising the following steps:

[0160] The coating process involves coating a release layer onto the surface layer A of a polyester film having a surface layer A to form a composition, wherein...

[0161] The surface layer A is a layer that is substantially free of inorganic particles.

[0162] The release layer forming composition comprises cationic curable polydimethylsiloxane (a);

[0163] The drying process involves heating and drying the polyester film coated with the release layer composition, wherein...

[0164] The heating and drying process includes a first drying step and a subsequent second drying step.

[0165] The drying temperature T1 in the first drying process is higher than the drying temperature T2 in the second drying process;

[0166] The photocuring process involves irradiating an active energy line after the drying process to cure the release layer into a composite material.

[0167] The manufacturing method of the present invention, by enhancing the first drying conditions (by enhancing drying), can prevent the aggregation of the resin constituting the release layer and obtain a release layer with high smoothness.

[0168] Furthermore, by setting the SP value of the solvent in the release layer forming composition to a specified value, it is possible to prevent the aggregation of the resin constituting the release layer, thereby obtaining a release layer with high smoothness.

[0169] Thus, the first drying step of the present invention has specified conditions, and in one embodiment, by using a specific solvent, a release layer with high smoothness can be obtained.

[0170] The method for manufacturing the release film of the present invention comprises, in sequence: a coating step, wherein a release layer forming composition containing at least cationic curable polydimethylsiloxane (a) is coated onto a substantially inorganic particle-free surface layer A of a polyester film; a drying step, wherein the film is heated and dried, for example, in a drying oven after coating; and a photocuring step, wherein the film is cured using active energy rays after heating and drying. A method performing the coating step, drying step, and photocuring step in that order is particularly preferred.

[0171] According to the manufacturing method of the present invention, it has been found that a release layer with high smoothness can be achieved by studying the manufacturing conditions in the coating process. Specifically, by containing an organic solvent with an SP value (δ) of 14 to 17 in the release layer forming composition, the aggregation of cationic curable polydimethylsiloxane (a) can be suppressed, resulting in an excellent release layer. The SP value (δ) can be used to predict the solubility of a substance, and organic solvents with an SP value (δ) of 14 to 17 exhibit excellent solubility for cationic curable polydimethylsiloxane (a). Therefore, in the drying process after the coating process, even if the concentration of (a) in the release layer forming composition increases due to the drying of the organic solvent, a uniformly dissolved state can be maintained, preventing aggregation and achieving clean leveling, resulting in a smooth release layer.

[0172] The content of organic solvent with an SP value (δ) of 14 to 17 in the release layer forming composition is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to 100 parts by mass of the release layer forming composition. If it is 10% by mass or more, the cationic curable polydimethylsiloxane (a) can remain in a dissolved state for a longer period during drying, thus preventing aggregation and deterioration of smoothness during drying, which is preferable. For example, the content of organic solvent with an SP value (δ) of 14 to 17 is 80% by mass or less, for example 65% by mass or less, or even less than 50% by mass, relative to 100 parts by mass of the release layer forming composition.

[0173] The SP value (δ) in this specification uses the Hildebrand solubility parameter. The Hildebrand solubility parameter can be experimentally calculated using the Hansen solubility parameters (HSP value) as shown in Equation 1.

[0174] SP value (δ) = ((δ) d ) 2 +(δ p ) 2 +(δh ) 2 ) 1 / 2 ...(Equation 1)

[0175] Here (δ) D ) is the dispersion term, (δ) P ) is the polar term, (δ) H The concept of decomposing the Hildebrand solubility parameter into three components is the Hansen solubility parameter, where is the hydrogen bond force term.

[0176] Alternatively, computer software such as HSPiP (Hansen Solubility Parameters in Practice) can be used to calculate the values. The values ​​described in this specification are calculated using Equation 1 based on the HSP values ​​recorded in the database within HSPiP ver4.0.

[0177] Examples of organic solvents with SP values ​​(δ) of 14 to 17 include n-hexane (δ: 14.9), n-heptane (δ: 15.3), n-octane (δ: 15.5), isopropyl ether (δ: 15.8), 1,1-diethoxyethane (δ: 15.9), methylcyclohexane (δ: 16.0), cyclopentane (δ: 16.5), and cyclohexane (δ: 16.8).

[0178] The preferred coating amount of the release layer forming composition is 10 g / m². 2 The following, or more preferably, is 8g / m 2 The following applies if the coating amount is 10g / m². 2 In the following cases, for example, when coating is performed by gravure coating, it is less likely to cause liquid disturbance at the joint between the film and the gravure roller, and a release layer with excellent smoothness can be obtained, which is therefore preferred.

[0179] In this invention, the solvent contained in the release layer forming composition is preferably two or more, and at least one of them is preferably a solvent with an SP value (δ) of 14 to 17 as described above, and at least one of them has a boiling point of 100°C or higher. By adding a solvent with a boiling point of 100°C or higher, sudden boiling during drying can be prevented, the coating film can be leveled, and the smoothness of the dried coating film surface can be improved.

[0180] As for the amount added, it is preferable to add about 10 to 70% by mass relative to the overall composition forming the release layer. Examples of solvents with a boiling point of 100°C or higher include toluene, xylene, n-octane, cyclohexanone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monopropyl ether, isobutyl acetate, and n-butanol.

[0181] In this invention, filtration is preferably performed on the coating liquid before the release layer is formed. There are no particular limitations on the filtration method; known methods can be used, but surface-type, depth-type, or adsorption-type cartridge filters are preferred. Using a cartridge filter allows for continuous transport of the coating liquid from the tank to the coating section, thus enabling efficient and productive filtration, which is preferable. Regarding the filtration precision, a filter capable of removing 99% or more of substances with a size of 1 μm is preferred, and a filter capable of removing 99% or more of substances with a size of 0.5 μm is even more preferred. Using a filter with the above-mentioned filtration precision removes foreign matter mixed in with the coating liquid forming the release layer, reduces foreign matter adhering to the release film of this invention, and results in a release layer with excellent smoothness, which is also preferable.

[0182] As for the coating method of the above-mentioned coating liquid, any known coating method can be applied, such as roll coating methods such as gravure coating, reverse roll coating, bar coating, mold coating, spray coating, air knife coating, etc.

[0183] Methods for coating the release layer forming composition onto a substrate film and then drying include known methods such as hot air drying and infrared heaters, but hot air drying, which has a fast drying speed, is preferred. Drying is preferably performed in a drying oven, but there are no particular limitations, and known drying ovens can be used. Regarding the type of drying oven, both roller-supported and floating types are acceptable, but roller-supported types are preferred because they allow for a wider range of airflow adjustment during drying, enabling the airflow to be adjusted to match the type of release layer.

[0184] The drying process can be divided into two steps: a constant-rate drying step at the beginning (hereinafter referred to as the first drying step) and a deceleration drying step (hereinafter referred to as the second drying step). Preferably, the two steps are performed consecutively in the order of the first drying step and the second drying step. This can be distinguished by dividing the drying oven into different zones; the first (initial) drying step can be performed using the first drying oven, and the second (later) drying step can be performed using the second drying oven.

[0185] The inventors have discovered that, in order to improve the smoothness of the release layer, it is important that the drying temperature T1 in the first drying step is higher than the drying temperature T2 in the second drying step. The temperatures of the first and second drying ovens are preferably set to the ranges described later. By manufacturing under such conditions, the constant-rate drying time in the first drying step can be shortened, the deceleration drying time in the second drying step can be extended, and a release layer with excellent planarity can be obtained, which is therefore preferable.

[0186] Furthermore, the inventors have found that increasing the temperature inside the first drying oven and shortening the constant-rate drying time is important.

[0187] More specifically, the drying temperature T1 is preferably 90°C or higher and 180°C or lower, and more preferably 100°C or higher and 150°C or lower. Increasing the temperature inside the first drying oven and shortening the constant-rate drying time prevents the aggregation of the cationic curable polydimethylsiloxane (a) contained in the release layer forming composition, which is therefore preferred. While a higher temperature in the first drying oven and a shorter constant-rate drying time are preferable, excessively high temperatures can lead to deterioration of the film's planarity due to heat; therefore, a temperature of 180°C or lower is preferred. A temperature of 90°C or higher is also preferred as it provides sufficient drying capacity.

[0188] The temperature inside the second drying oven is preferably 60°C or higher and 140°C or lower, more preferably 80°C or higher and 120°C or lower. In the second drying process, by slowing down the drying time, drying can be carried out without roughening the surface of the release layer before photocuring, thereby improving the smoothness of the release layer, which is therefore preferred.

[0189] For example, the constant-rate drying time in the first drying step is preferably shorter than the deceleration drying time in the second drying step. This prevents the deterioration of the film's planarity and allows drying without roughening the surface of the release layer before photocuring, thus improving the smoothness of the release layer.

[0190] The time from coating to entering the first drying oven is preferably 0.1 seconds or more and 2.5 seconds or less, more preferably 0.1 seconds or more and 2.0 seconds or less, and the shorter the better. By speeding up the time until entering the first drying oven, the drying time in the first drying process can be shortened, the aggregation of cationic curable polydimethylsiloxane (a) can be suppressed, and a release layer with excellent smoothness can be obtained, which is therefore preferred. The time until entering the drying oven can be calculated based on the processing speed and the structure of the processing machine.

[0191] The manufacturing method of the present invention includes a photocuring process in which the release layer is cured by irradiating an active energy ray after a drying process.

[0192] In the photocuring process, the dried release layer is subjected to a cationic curing reaction by irradiation with active energy rays. Known technologies such as ultraviolet light and electron beams can be used as the active energy rays, with ultraviolet light being preferred. The cumulative light intensity when using ultraviolet light can be expressed as the product of illuminance and irradiation time. For example, 10–500 mJ / cm² is preferred. 2 Setting the value above the aforementioned lower limit allows for sufficient curing of the release layer, which is therefore preferred. Setting the value below the aforementioned upper limit suppresses thermal damage to the film during irradiation and maintains the smoothness of the release layer surface, which is also preferred.

[0193] When irradiating with active energy rays, it is preferable to use a support roller to hold the back side of the film. By providing a support roller, the distance to the active energy ray source can be kept constant, thus enabling uniform irradiation, which is preferred. Furthermore, it is preferable to irradiate with active energy rays while cooling the surface of the support roller and the film. By cooling, the film is less susceptible to heat-induced damage even when irradiated with active energy rays, maintaining the smoothness of the release layer surface, which is also preferred.

[0194] In one embodiment, the manufacturing method of the present invention provides a method for manufacturing a release film, the release film being used to manufacture a resin sheet containing an inorganic compound.

[0195] (Resin sheet)

[0196] The resin sheet in this invention is not particularly limited to any sheet containing resin. In one embodiment, the release film of this invention is a release film for molding resin sheets containing inorganic compounds. Examples of inorganic compounds include metal particles, metal oxides, minerals, etc., such as calcium carbonate, silica particles, aluminum particles, barium titanate particles, etc. Because this invention has a release layer with high smoothness, even in embodiments where the resin sheet contains these inorganic compounds, defects that may be caused by inorganic compounds, such as resin sheet breakage and difficulty in peeling the resin sheet from the release layer, can be suppressed.

[0197] The resin components forming the resin sheet can be appropriately selected according to the application. In one embodiment, the resin sheet containing inorganic compounds is a ceramic blank. For example, the ceramic blank may contain barium titanate as an inorganic compound. Alternatively, polyvinyl butyral resin may be included as a resin component.

[0198] In one embodiment, the thickness of the resin sheet is 0.2 μm or more and 1.0 μm or less.

[0199] For example, the present invention can provide a method for manufacturing a release film, which is used to manufacture resin sheets containing inorganic compounds. Additionally, the method for manufacturing a release film for resin sheet molding according to the present invention may include a step of molding a resin sheet with a thickness of 0.2 μm or more and 1.0 μm or less.

[0200] (Ceramic blanks and ceramic capacitors)

[0201] Typically, multilayer ceramic capacitors have a cuboid ceramic substrate. Inside the ceramic substrate, a first internal electrode and a second internal electrode are alternately arranged along the thickness direction. The first internal electrode is exposed at a first end face of the ceramic substrate. A first external electrode is located on the first end face. The first internal electrode is electrically connected to the first external electrode in the first end face. The second internal electrode is exposed at a second end face of the ceramic substrate. A second external electrode is located on the second end face. The second internal electrode is electrically connected to the second external electrode in the second end face.

[0202] In one embodiment, the release film of the present invention is a release film for manufacturing ceramic blanks, used to manufacture such multilayer ceramic capacitors.

[0203] For example, the ceramic blank manufacturing method using the release film for ceramic blank manufacturing of the present invention to form ceramic blanks can form ceramic blanks with a thickness of 0.2 μm or more and 1.0 μm or less.

[0204] More specifically, for example, a ceramic blank is manufactured as follows: First, the release film of the present invention is used as a carrier film, a ceramic slurry for forming the ceramic matrix is ​​coated, and then dried. The ceramic blank is required to be extremely thin, with a thickness of 0.2 to 1.0 μm. A conductive layer for forming the first or second internal electrode is printed on the coated and dried ceramic blank. The ceramic blanks, the ceramic blanks with the conductive layer for forming the first internal electrode printed, and the ceramic blanks with the conductive layer for forming the second internal electrode printed are appropriately stacked and pressed to obtain a master laminate. The master laminate is divided into multiple parts to produce an unprocessed ceramic matrix. The unprocessed ceramic matrix is ​​fired to obtain a ceramic matrix. Then, by forming the first and second external electrodes, a multilayer ceramic capacitor can be completed.

[0205] Example

[0206] The present invention will be further described in detail below using examples, but the present invention is not limited to these examples in any way. The characteristic values ​​used in the present invention are evaluated using the following methods.

[0207] (Thickness of release layer)

[0208] The cut release films were embedded in resin and then ultrathinly sliced ​​using an ultramicrotome. Cross-sectional observation was then performed using a JEM2100 transmission electron microscope (TEM), and the film thickness of the release layer was determined based on the observed TEM images. In cases where the thickness was too thin to be accurately evaluated in cross-sectional observation, a reflectance spectrophotometer (Otsuka Electronics Co., Ltd., FE-3000) was used for measurement.

[0209] (Weight of the release layer)

[0210] In this specification, the weight of the release layer is set at 1 g / m for every 1 μm of thickness. 2 The calculated weight value. For example, if the release layer thickness measured using the above method is 0.2 μm, the total weight of the release layer is 0.2 g / m. 2 Furthermore, the weights of the cationic curable polydimethylsiloxane (a), the cationic curable resin (b), and the acid-generating agent (c) contained in the release layer are calculated using the mixing ratios of each component in the release layer forming composition and the total weight of the release layer. For example, when the release layer thickness is 0.2 μm and the weight ratio of the cationic curable polydimethylsiloxane (a) in the release layer is 5 parts by mass, the weight of (a) contained in the release layer is 0.01 g / m. 2 It should be noted that the release layer weight ratio (mass%) is calculated based on a total of 100 parts by mass for components (a) and (b).

[0211] (Amount of the release layer forming composition)

[0212] The values ​​are calculated using the liquid consumption weight and processing area of ​​the composition formed by the release layer used in the coating process.

[0213] (Time from coating to the first drying oven)

[0214] The values ​​are calculated based on the film travel distance from the coating section to the first drying oven and the processing speed.

[0215] (Surface roughness Sa, maximum protrusion height Sp)

[0216] The surface shape was measured using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. The average surface roughness (Sa) of the area was the average of 5 measurements, and the maximum protrusion height (Sp) was the maximum value among 5 measurements after excluding the maximum and minimum values ​​from 7 measurements.

[0217] (Measurement conditions)

[0218] • Measurement mode: WAVE mode

[0219] Objective lens: 50x

[0220] ·0.5× lens barrel

[0221] • Measurement area: 187μm × 139μm

[0222] (Analysis conditions)

[0223] • Horizontal correction: 4 corrections

[0224] • Interpolation processing: Full interpolation

[0225] (Number of protrusions with a height of 10nm or more, number of protrusions with a height of 5nm or more)

[0226] For all seven measurements of the maximum protrusion height mentioned above, particle analysis was performed using the measurement data representing the center value. Particle analysis was performed using Vertscan R550H-M100 analysis software under the following conditions: Particle analysis was performed on the same measurement area as the area measured for the surface roughness and maximum protrusion height mentioned above, and the number of protrusions with a maximum height of 10 nm or more, or the number of protrusions with a maximum height of 5 nm or more, was calculated. The protrusion count was converted to 1 mm. 2 The converted value.

[0227] (Particle analysis conditions)

[0228] • Horizontal correction: 4 corrections

[0229] • Storage and handling: Complete interpolation

[0230] Collision Analysis

[0231] • Reference height: Zero plane

[0232] (Ceramic sheet peeling force)

[0233] Slurry composition I, containing the following materials, was stirred and mixed for 10 minutes. Then, using a bead mill, it was dispersed for 10 minutes with zirconia beads of 0.5 mm diameter to obtain a primary dispersion. Next, slurry composition II, containing the following materials, was added to the primary dispersion to achieve a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0. The mixture was then further dispersed for 10 minutes using a bead mill with zirconia beads of 0.5 mm diameter to obtain a ceramic slurry.

[0234] (Slurry Composition I)

[0235]

[0236] (Slurry Composition II)

[0237]

[0238] Next, a slurry with a dry thickness of 1.0 μm was applied to the release surface of the obtained release film sample using an applicator, and dried at 60°C for 1 minute to obtain a release film with ceramic blanks. After eliminating static electricity with a destatic motor (Keyence Corporation, SJ-F020), the release film with ceramic blanks was peeled using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3, load sensor load 0.1N) at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 10 m / min. As the peeling direction, double-sided adhesive tape (Nitto Denko Co., Ltd., No. 535A) was adhered to the SUS plate attached to the peel tester, and the release film was fixed on it by bonding the ceramic blank side to the double-sided tape. Peeling was performed by stretching the release film side. The average peel force from 20 mm to 70 mm in the obtained measurements was calculated and taken as the peel force. The peel force was measured a total of 5 times, and the average value was used for evaluation. The results were judged according to the following criteria based on the obtained peel force values.

[0239] ○: Above 0.1 mN / mm and less than 1.0 mN / mm

[0240] ×: 1.0mN / mm or more

[0241] (Evaluation of pinholes in ceramic blanks)

[0242] Similar to the aforementioned evaluation of the peelability of the ceramic slurry, a 1 μm thick ceramic preform was formed on the release surface of the release film. Next, the release film containing the ceramic preform was peeled off to obtain the ceramic preform. In the central region of the obtained ceramic preform along the film width direction, at a depth of 25 cm... 2 Within a certain range, light is shone from the opposite side of the ceramic slurry coating surface, and the formation of pinholes visible through the light is observed. Visual judgment is made according to the following criteria.

[0243] ○: No pinholes were generated.

[0244] ×: More than one pinhole was generated.

[0245] (Preparation of polyethylene terephthalate granules (PET(I)))

[0246] As the esterification reactor, a continuous esterification reactor consisting of a stirring device, a condenser, and a three-stage fully mixed tank with a raw material inlet and a product outlet was used. TPA (terephthalic acid) was set at 2 tons / hour, EG (ethylene glycol) at 2 moles relative to 1 mole of TPA, and antimony trioxide at an amount of Sb atoms relative to 160 ppm of generated PET. These slurries were continuously supplied to the first esterification reactor of the esterification reactor, and the reaction was carried out at atmospheric pressure, with an average residence time of 4 hours and a temperature of 255°C. Next, the reaction product from the first esterification reactor was continuously extracted from the system and fed to the second esterification reactor. EG removed by distillation from the first esterification reactor was supplied to the second esterification reactor at a mass ratio of 8% relative to the generated PET. Then, an EG solution containing magnesium acetate tetrahydrate at a mass ratio of 65 ppm Mg atoms relative to the generated PET and an EG solution containing TMPA (trimethyl phosphate) at a mass ratio of 40 ppm P atoms relative to the generated PET were added. The reaction was carried out at atmospheric pressure with an average residence time of 1 hour and at 260°C. Next, the reaction product from the second esterification reactor was continuously extracted from the system and fed to the third esterification reactor, where it was dispersed using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) at 39 MPa (400 kg / cm²). 2 Under pressure, 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm (after an average of 5 dispersion treatments) and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm and an ammonium salt of polyacrylic acid attached to calcium carbonate (1% by mass relative to calcium carbonate) were added to form a 10% EG slurry. The reaction was carried out at atmospheric pressure with an average residence time of 0.5 hours and a temperature of 260°C. The esterification reaction product generated in the third esterification reactor was continuously fed to a three-stage continuous polycondensation reactor for polycondensation. After filtration through a filter made of sintered stainless steel fibers with a 95% particle size cutoff of 20 μm, the product was ultrafiltered, extruded into water, cooled, and cut into small flakes to obtain PET flakes with an intrinsic viscosity of 0.60 dl / g (hereinafter referred to as PET(I)). The lubricant content in the PET flakes was 0.6% by mass.

[0247] (Preparation of polyethylene terephthalate granules (PET(II)))

[0248] On the other hand, in the manufacture of the above-mentioned PET(I) flakes, PET flakes with an intrinsic viscosity of 0.62 dl / g that are completely free of particles such as calcium carbonate and silica are obtained (hereinafter referred to as PET(II)).

[0249] (Manufacturing of the laminated thin film X1)

[0250] After drying, these PET flakes were melted at 285°C and then melted again at 290°C using another melt extruder. This resulted in a two-stage filtration process: a filter with 95% 15μm particle size cutoff made from sintered stainless steel fibers and a filter with 95% 15μm particle size cutoff made from sintered stainless steel granules. The filtration was then combined in the feed head and layered with PET(I) as surface layer B (reverse demolding side layer) and PET(II) as surface layer A (demolding side layer). The layers were extruded (cast) into sheets at a speed of 45 m / min. Electrostatic sealing was then performed on a casting drum at 30°C to achieve electrostatic sealing and cooling, yielding unstretched polyethylene terephthalate sheets with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted to PET(I) / (II) = 60% by mass / 40% by mass, calculated based on the discharge rate of each extruder. Next, the unstretched sheet was heated with an infrared heater and stretched longitudinally by 3.5 times at a roller temperature of 80°C through the speed difference between the rollers. Then, it was fed into a tenter frame and stretched transversely by 4.2 times at 140°C. Following this, it was heat-treated at 210°C in a heat-setting zone. Afterward, it underwent a 2.3% relaxation treatment transversely at 170°C to obtain a biaxially stretched polyethylene terephthalate film X1 with a thickness of 31 μm. The surface layer A of the obtained film X1 has a Sa value of 1 nm, and the surface layer B has a Sa value of 28 nm.

[0251] (Manufacturing of laminated thin film X2)

[0252] As the laminated film X2, E5101 (TOYOBOESTER (registered trademark) film, manufactured by Toyobo Co., Ltd.) with a thickness of 25 μm was used. E5101 has a structure containing particles in surface layer A and surface layer B. The Sa of surface layer A and surface layer B of the laminated film X2 is 24 nm.

[0253] (Cationic-cured polydimethylsiloxane (a))

[0254] (a)-1: UV POLY215 (manufactured by Arakawa Chemical Industry Co., Ltd., 100% solids)

[0255] (Catonic curing resin (b))

[0256] (b)-1: Celoxide 2021P (manufactured by Daicel Corporation, 100% solids)

[0257] (b)-2: X-40-2670 (manufactured by Shin-Etsu Chemical Industry Co., Ltd., 100% solids)

[0258] (Acid-producing agent (c))

[0259] (c)-1: CPI-101A (manufactured by SAN-APRO Co., Ltd., solid content 50%)

[0260] (Example 1)

[0261] On the surface layer A of the laminated film X1, after passing the release layer forming composition 1 containing the following components through a filter capable of removing more than 99% of foreign matter larger than 0.5 μm, a reverse gravure printing plate is used to achieve a coating weight of 5.0 g / m². 2 The coating is applied in a specific manner. Then, the processing speed is adjusted so that the product enters the first drying oven after 0.5 seconds, and continuous heating and drying are performed at 120°C in the first drying oven and 90°C in the second drying oven. After the drying process, the product is irradiated with a cumulative light dose of 100 mJ / cm² using a UV irradiation machine (SAN-APRO Co., Ltd., H-valve). 2 Ultraviolet light is used to cure the release layer, thereby obtaining a release film for resin sheet molding. Furthermore, the smoothness, peelability, and pinholes of the obtained release film were evaluated, and the results are shown in Table 1.

[0262] Thus, the resulting release film for molding resin sheets is, for example, a release film capable of manufacturing resin sheets with a thickness of 0.2 μm or more and 1.0 μm or less.

[0263] It should be noted that the weights (mg / m³) of each component (a), (b), and (c) listed in the table are... 2 This indicates the content ratio of each solid component (the weight of each component relative to the total weight of the release layer).

[0264] (Mold release layer forming composition 1)

[0265]

[0266]

[0267] (Examples 2-4)

[0268] Except for changing the composition and manufacturing method of the release layer as described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 1.

[0269] (Example 5)

[0270] Except for the release layer composition 2 formed using the following components, a release film for resin sheet molding was obtained using the same method as in Example 1.

[0271] (Mold release layer forming composition 2)

[0272]

[0273] (Example 6)

[0274] In addition to replacing n-heptane in the release layer forming composition with cyclohexane (SP value (δ): 16.8, (δ D ): 16.8, (δ P ): 0.0, (δ H Apart from 0.2), a release film for resin sheet molding was obtained using the same method as in Example 2.

[0275] (Examples 7 and 8)

[0276] Except for changing the coating amount and solid content ratio as described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 2. This time, it was prepared in the same manner as the release layer forming composition 1, with the same organic solvent ratio.

[0277] (Example 9)

[0278] Except for the release layer forming composition 3 which is changed to the following composition, a release film for resin sheet molding is obtained by the same method as in Example 1.

[0279] (Composition 3 for forming the release layer)

[0280]

[0281] (Examples 10-12)

[0282] Except for changing the composition and manufacturing method of the release layer as described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 1.

[0283] (Example 13)

[0284] Except for the release layer composition 4 formed using the following components, a release film for resin sheet molding was obtained using the same method as in Example 1.

[0285] (Mold release layer forming composition 4)

[0286]

[0287]

[0288] (Example 14)

[0289] In addition to replacing n-heptane in the release layer forming composition with cyclohexane (SP value (δ): 16.8, (δ D ): 16.8, (δ P ): 0.0, (δ H Apart from 0.2), a release film for resin sheet molding was obtained using the same method as in Example 2.

[0290] (Examples 15 and 16)

[0291] Except for changing the coating amount and solid content ratio as described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 2. This time, it was prepared in the same manner as the release layer forming composition 3, with the same organic solvent ratio.

[0292] (Example 17)

[0293] Except for the release layer forming composition 5 using the following components, an ultra-thin resin sheet molding release film was obtained using the same method as in Example 1.

[0294] (Composition 5 for forming the release layer)

[0295]

[0296] (Example 18)

[0297] Except for changing the solid component concentration to that recorded in Table 1 and further preparing the release film 5 with the organic solvent ratio and the release layer in the same manner, a release film for resin sheet molding was obtained using the same method as in Example 1.

[0298] (Example 19)

[0299] Except for changing to the manufacturing method described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 17.

[0300] (Example 20)

[0301] Except for changing to release layer forming composition 6, a release film for molding ultrathin resin sheets was obtained using the same method as in Example 1.

[0302] (Composition 6 for forming the release layer)

[0303]

[0304] (Example 21)

[0305] Except for changing n-heptane in release layer forming composition 5 to cyclohexane (SP value (δ): 16.8, (δ D ): 16.8, (δ P ): 0.0, (δ H Apart from 0.2), a release film for resin sheet molding was obtained using the same method as in Example 1.

[0306] (Examples 22 and 23)

[0307] Except for changing the coating amount and solid component concentration as described in Table 1, a release film for resin sheet molding was obtained using the same method as in Example 17. This time, it was prepared in the same manner as the release layer forming composition 5, with the same organic solvent ratio.

[0308] (Comparative Example 1)

[0309] Except for the release layer forming composition 7 with the following composition, an ultra-thin resin sheet molding release film was obtained using the same method as in Example 1.

[0310] (Mold release layer forming composition 7)

[0311]

[0312] (Comparative Example 2)

[0313] Except for the release layer forming composition 8, which is changed to the following composition, a release film for molding ultrathin resin sheets is obtained by the same method as in Example 1.

[0314] (Mold release layer forming composition 8)

[0315]

[0316] (Comparative Example 3)

[0317] Except for the release layer forming composition 9 with the following composition, an ultra-thin resin sheet molding release film was obtained using the same method as in Example 1.

[0318] (Mold release layer forming composition 9)

[0319]

[0320] (Comparative Example 4)

[0321] In addition to coating the laminated film X2, an ultrathin resin sheet molding release film was obtained using the same method as in Example 10.

[0322] [Table 1A]

[0323]

[0324] [Table 1B]

[0325]

[0326] [Table 1C]

[0327]

[0328] [Table 2A]

[0329]

[0330] [Table 2B]

[0331]

[0332] [Table 2C]

[0333]

[0334] Comparative Example 1, lacking cationic cured polydimethylsiloxane (a), exhibited high peel strength and was unable to be peeled. In Comparative Examples 2-4, the number of protrusions with a height greater than 10 nm exceeded 200 per mm. 2 Pinholes are generated in the green sheet that is being demolded. Furthermore, in Comparative Example 4, inorganic particles are present in the substrate, which significantly reduces the smoothness of the demolded film, resulting in damage and pinholes in the green sheet.

[0335] Industrial availability

[0336] According to the present invention, by improving the smoothness and peelability of the release layer, a release film with few defects can be provided even for ultra-thin sheets with a thickness of less than 1 μm, thereby enabling the manufacture of resin sheets without producing defects.

Claims

1. A release film for molding resin sheets, comprising a polyester film as a substrate and a release layer, The polyester film has a surface layer A that is substantially free of inorganic particles. The release layer is present on the surface layer A. The release layer is a layer formed by curing a release layer composition. The release layer forming composition comprises cationic curable polydimethylsiloxane (a). The surface roughness (Sa) of the release layer is below 2 nm. The number of protrusions with a height of 10 nm or more on the surface of the release layer is 200 per mm. 2 the following, The maximum protrusion height (Sp) of the release layer is less than 20 nm, and the total number of protrusions with a height of 5 nm or more but less than 10 nm on the surface of the release layer, plus the number of protrusions with a height of 10 nm or more, is 1500 per mm. 2 the following.

2. The release film for resin sheet molding according to claim 1, wherein, The cationic cured polydimethylsiloxane (a) has at least one functional group selected from vinyl ether, oxetyl, and epoxy groups.

3. The release film for resin sheet molding according to claim 1, wherein, The release layer contains 90 mg / m³ of cationic cured polydimethylsiloxane (a). 2 the following.

4. The release film for resin sheet molding according to claim 1, wherein, The release layer forming composition also contains a cationic curable compound (b-1) that does not have an organosilicon framework. The cationic curable compound (b-1) has two or more alicyclic epoxy groups within its molecule. The content of the cationic curable compound (b-1) is 80% by mass or more, relative to a total of 100 parts by mass of the cationic curable polydimethylsiloxane (a) and the cationic curable compound (b-1).

5. The release film for resin sheet molding according to claim 1, wherein, The release layer forming composition also contains a cyclic siloxane compound (b-2) having an alicyclic epoxy group. The cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups within its molecule. The content of the cyclic siloxane compound (b-2) is 80% by mass or more, relative to a total of 100 parts by mass of cationic cured polydimethylsiloxane (a) and cyclic siloxane compound (b-2).

6. The release film for resin sheet molding according to claim 1, wherein, The release layer forming composition contains an organic solvent with an SP value (δ) of 14 or higher and 17 or lower. The release layer forming composition contains, at least 10% by mass, an organic solvent with an SP value (δ) of 14 or more and less than 17, relative to 100 parts by mass of the total weight of the release layer forming composition.

7. The release film for molding resin sheets according to any one of claims 1 to 6, wherein it is a release film for manufacturing resin sheets containing inorganic compounds.

8. The release film for resin sheet molding according to claim 7, wherein, Resin sheets containing inorganic compounds are ceramic blanks.

9. The release film for molding resin sheets according to any one of claims 1 to 6, wherein it is a release film for molding resin sheets with a thickness of 0.2 μm or more and 1.0 μm or less.

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