Release film for resin sheet molding

Abstract

[Problem] To provide a resin sheet molding release film which does not cause defective resin sheets at the time of resin sheet production by forming a release film which improves release properties and has low rewinding electrification. [Solution] A resin sheet molding release film having a base film and a release layer provided on one face of the base film, the release film having a hydrophobized layer on the face of the base film opposite the release layer, the release layer being a layer formed of a cured product of a composition having a cationically curable polydimethylsiloxane (a), the water contact angle of the hydrophobized layer being 90° or more and 130° or less, the normal release force (I) of the release layer measured in the release film obtained by rewinding the release film temporarily into a roll shape and then unwinding the release film being 1.00 or more and 1.50 or less relative to the release force (II) after heating.

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 green sheets, such as those for multilayer ceramic capacitors and ceramic substrates, where high smoothness is required. In recent years, with the miniaturization and increasing capacitance of multilayer ceramic capacitors, there has been a trend towards thinner ceramic green sheets. Ceramic green sheets are formed by coating a slurry containing ceramic components such as barium titanate and binder resin onto a release film and then drying it. Electrodes are printed on the formed ceramic green sheet, and after being peeled off from the release film, the ceramic green sheet is then laminated, pressed, fired, and coated with external electrodes to manufacture multilayer ceramic capacitors.

[0004] When ceramic green sheets are formed on the surface of a release layer on a polyester film substrate, the peelability when separating the ceramic green sheets from the release film becomes important. If the peeling force is large or uneven, the following problems arise: damage to the ceramic green sheets 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 green sheets with a lower and more uniform force.

[0005] In recent years, the advancement of thin-film ceramic green sheets has gradually led to a demand for ceramic green sheets with a thickness of less than 1.0 μm, and more specifically, 0.2 μm to 1.0 μm. Therefore, the requirements for the peelability of release films have become increasingly stringent.

[0006] As a release film with excellent peelability, the following patent documents describe release films. For example, Patent Document 1 proposes a release film having a release layer in which a free radical-curable resin is used as the main component.

[0007] However, the release film in Patent Document 1 uses a free radical curing resin. Therefore, when the release layer is processed in the atmosphere, it is susceptible to oxygen hindrance, resulting in poor curing of the release layer surface. If poor curing of the release layer surface occurs, the release layer will be eroded by organic solvents during the processing of the ceramic green sheet and the printing of internal electrodes, leading to increased peeling force and impaired peeling uniformity. As a result, there is a concern that the ceramic green sheet may be damaged during peeling.

[0008] To address the aforementioned issues, Patent Document 2 proposes using a cationic curable resin as the release layer of the main component. Since the cationic curable resin does not cause oxygen hindrance, even when the release layer is processed in the atmosphere, poor curing does not occur, resulting in a release film with excellent peelability.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: International Publication No. 2013 / 145864

[0012] Patent Document 2: International Publication No. 2018 / 079337 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] However, the cationic curing resin used in the release film of Patent Document 2 has a slower reaction rate compared to the free radical curing resin. Therefore, the reaction is not terminated by irradiation with active energy rays alone, and the polymerization reaction tends to proceed over a long period of time.

[0015] Therefore, in the case of manufacturing a release film using a cationic curable resin, a release layer forming composition is coated on one side of a substrate film, and after drying, it is irradiated with active energy rays to cure the release layer forming composition. The cationic polymerization reaction is then terminated by rolling it into a roll and storing it, resulting in a release layer with excellent peelability.

[0016] Furthermore, the polymerization reaction may not be complete immediately after the material is rolled up and stored, potentially affecting the surface shape of the release layer. Therefore, it is desirable to further reduce defects in the surface shape of the release layer.

[0017] Furthermore, cationic curing resins tend to cure poorly due to the influence of water. When processing the release film, it is rolled up and stored, thus being stored with the release layer in contact with the reverse release surface of the substrate film. Therefore, due to the influence of trace amounts of moisture present on the reverse release surface of the substrate film, the time-dependent reaction of the cationic curing resin is hindered, resulting in insufficient curing of the release layer.

[0018] The poor curing of the release layer caused by the influence of the reverse release surface of the release film becomes more and more obvious as the thin film production of ceramic green sheets progresses, and a release film with better peelability is sought.

[0019] This invention was made in light of the aforementioned problems in the prior art. Specifically, its object is to provide a release film with excellent peelability that suppresses poor curing of the release layer, which is mainly composed of a cationic curable resin.

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

[0021] Solution for solving the problem

[0022] That is, the present invention comprises the following components.

[0023] [1] A release film comprising: a substrate film and a release layer disposed on one side of the substrate film,

[0024] The release film has a hydrophobic layer on the side of the aforementioned substrate film opposite to the aforementioned release layer.

[0025] The aforementioned release layer is a layer formed from the cured product of a composition having cationic curable polydimethylsiloxane (a).

[0026] The water contact angle of the aforementioned hydrophobic layer is greater than 90° and less than 130°.

[0027] The normal peel force (I) and the peel force (II) after heating of the release film obtained by temporarily rolling up and unwinding the aforementioned release film for molding resin sheets are as follows:

[0028] (II) / (I) = 1.00 or higher and 1.50 or lower.

[0029] [2] In one method, the normal peel force (I) of the release layer in the release film obtained by unwinding is less than 1500mN / 50mm.

[0030] [3] In one method, the charge of the release film roll obtained by winding the aforementioned release film into a roll is less than ±1kV when it is released at 100m / min.

[0031] [4] In one embodiment, the aforementioned hydrophobic layer is a layer formed from a cured composition of a cationic curable polydimethylsiloxane (a).

[0032] [5] In one embodiment, the thickness of the aforementioned hydrophobic layer is 0.001 μm or more and 0.5 μm or less.

[0033] [6] In one embodiment, the aforementioned release layer and the aforementioned hydrophobic layer substantially do not contain particles with a diameter of 1.0 μm or larger.

[0034] [7] In one embodiment, the aforementioned substrate film is a polyester film having a surface layer A that is substantially free of inorganic particles with a particle size of 1.0 μm or more and a surface layer B that contains particles, a release layer is stacked on the aforementioned surface layer A, and a hydrophobic layer is stacked on the aforementioned surface layer B.

[0035] [8] In one embodiment, the release film is a resin sheet molding film containing an inorganic compound.

[0036] [9] In one method, the resin sheet containing inorganic compounds is a ceramic green sheet.

[0037]

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

[0038]

[11] In one embodiment, a method for manufacturing a ceramic green sheet is provided, which is a method for manufacturing a ceramic green sheet by forming a ceramic green sheet using the above-mentioned release film for manufacturing ceramic green sheet, wherein the formed ceramic green sheet has a thickness of 0.2 μm to 1.0 μm.

[0039] The effects of the invention

[0040] The release film for resin sheet molding of the present invention has a release layer on one side of a substrate film and a hydrophobic layer on the side of the substrate film opposite to the aforementioned release layer (reverse release surface), thereby suppressing the occurrence of curing obstacles of the release layer and providing a release film for resin sheets, especially ceramic green sheets, that is defect-free and can be peeled off. Detailed Implementation

[0041] The present invention will now be described in detail.

[0042] This invention relates to a release film for resin sheet molding, comprising: a substrate film and a release layer disposed on one side of the substrate film, wherein a hydrophobic layer is provided on the side of the substrate film opposite to the aforementioned release layer (the reverse release surface). By providing a hydrophobic layer on the reverse release surface of the substrate film, the release layer and the hydrophobic layer will come into contact when stored in a roll, thus eliminating concerns about poor curing of the release layer and resulting in a release film with excellent peelability.

[0043] Furthermore, it can suppress the occurrence of poor curing of the release layer, thus reducing the deterioration of the smoothness of the release surface due to the unevenness of the anti-release surface in contact with the release surface when stored, for example, in roll form. Therefore, it can further reduce the defects in the surface shape of the release layer that may occur from the manufacturing of the release film to its use.

[0044] The release layer is preferably a cured product of a cationic curable polydimethylsiloxane (a) composition that does not cause poor curing due to oxygen hindrance. By using cationic curable polydimethylsiloxane (a), when manufacturing a release film in the atmosphere, curing can proceed stably without curing hindrance, resulting in a release film with excellent peelability.

[0045] The hydrophobic layer is preferably a cured product of a composition containing cationic curable polydimethylsiloxane (a). In one embodiment, the cationic curable polydimethylsiloxane (a) may have the same composition as the cationic curable polydimethylsiloxane (a) contained in the release layer, or it may have a different composition. Preferably, it has the same composition as the cationic curable polydimethylsiloxane (a) contained in the release layer. It should be noted that, in this specification, when using cured polydimethylsiloxane (a) with the same composition, the molecular weight, mixing amount, etc., can be appropriately adjusted when used in the hydrophobic layer.

[0046] By using cationic curable polydimethylsiloxane (a), the charged sequence of the release layer to be contacted is close when stored in a roll, and the charging is suppressed. Therefore, there is no peel charge, and the ceramic green sheet can be peeled off without defects with low force. In addition, the reverse release surface is hydrophobic, so when stored in a roll, the influence of moisture on the reverse release surface can be suppressed, and poor curing of the release layer can also be prevented.

[0047] Details of the cured polydimethylsiloxane (a) are described below.

[0048] (Polyester film)

[0049] The polyester used to form the polyester film used as the substrate film (hereinafter, sometimes referred to as substrate) in this invention is not particularly limited, and polyester formed by film molding of 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 butylene terephthalate, polyethylene terephthalate, or copolymers with components of these resins as the main components. 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, and other dicarboxylic acid components and glycol components may also be copolymerized in small amounts. For example, from a cost point of view, polyethylene terephthalate made solely from terephthalic acid and ethylene glycol is preferred. Furthermore, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizers, can be added to the extent that they do not impair the effect of the release film of the present invention. For reasons such as the high biaxial modulus of elasticity, the polyester film is preferably a biaxially oriented polyester film.

[0050] 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, less breakage occurs during the stretching process, which is therefore preferred. Conversely, when the intrinsic viscosity is 0.70 dl / g or lower, good cutability is achieved when cutting to the specified product width, and dimensional defects do not occur, which is also preferred. Furthermore, the raw material granules are preferably thoroughly vacuum dried.

[0051] It should be noted that, in this specification, when abbreviated as "polyester film", it refers to a (laminated) polyester film having surface layer A and surface layer B.

[0052] 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 biaxially stretched. 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.

[0053] 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.

[0054] 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, deformation due to heat is not a concern during film production, processing, or molding, 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 be excessive, which is preferable in terms of reducing environmental impact.

[0055] The aforementioned polyester film substrate can be a single layer or a multilayer consisting of two or more layers. For example, the substrate film can be a polyester film having a surface layer A that substantially does not contain particles with a particle size of 1.0 μm or larger and a surface layer B that contains particles. Preferably, surface layer A substantially does not contain inorganic particles with a particle size of 1.0 μm or larger.

[0056] In this method, surface layer A may also contain particles with a diameter greater than 1 nm but less than 1.0 μm. By substantially eliminating particles with a diameter greater than 1.0 μm, such as inorganic particles, surface layer A can reduce defects caused by the transfer of particle shapes from the substrate to the resin sheet.

[0057] In one method, the surface layer A also does not contain particles with a particle size of less than 1.0 μm, thereby more effectively suppressing the transfer of particle shape from the substrate to the resin sheet and causing defects.

[0058] In one embodiment, the aforementioned polyester film substrate is preferably a laminated film having at least one surface layer A that is substantially free of inorganic particles on one side. This further effectively suppresses the transfer of particle shapes from the substrate to the resin sheet, thus preventing defects.

[0059] For example, surface layer A, which is substantially free of particles with a particle size of less than 1.0 μm, is preferably also substantially free of particles with a particle size of more than 1.0 μm.

[0060] In this invention, "substantially free of particles" means, for example, in the case of inorganic particles smaller than 1.0 μm, that, when quantifying inorganic elements using fluorescence X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even without actively adding inorganic particles to the film, there is still the possibility of contaminants from foreign matter, or dirt adhering to the raw material resin or the production line and equipment during the film manufacturing process, which may detach and mix into the film. Furthermore, "substantially free of particles with a diameter of 1.0 μm or larger" means that particles with a diameter of 1.0 μm or larger are not actively included.

[0061] In the case of a laminated polyester film consisting of two or more layers, it is preferable to have a surface layer B that can contain inorganic particles on the opposite side of the surface layer A, which does not substantially contain inorganic particles.

[0062] As a layered configuration, when the layer on the side with the release layer is designated as layer A, the layer on the opposite side as layer B, and the core layer (other than these) as layer C, the layer configuration in the thickness direction can be a layered structure such as release layer / A / B or release layer / A / C / B. Of course, layer C can also consist of multiple layers. Furthermore, the surface layer B may not contain inorganic particles. In this case, to impart slip properties for winding the film into a roll, it is preferable to provide a coating on the surface layer B that contains at least inorganic particles and a binder.

[0063] In the polyester film substrate of this invention, from the viewpoint of film slippage and ease of air removal, the surface layer B opposite to the side where the release layer is formed preferably contains inorganic particles, and silica particles and / or calcium carbonate particles are particularly preferred. The content of inorganic particles is preferably 5,000 to 15,000 ppm in the surface layer B as a total of inorganic particles.

[0064] At this point, the average surface roughness (Sa) of the thin film in surface layer B is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5000 ppm or more and Sa is 1 nm or more, air can escape uniformly when the film is wound into a roll, resulting in good winding posture and good planarity, thus making it suitable for manufacturing ultrathin ceramic green sheets. In addition, when the total amount of silica particles and / or calcium carbonate particles is 15000 ppm or less and Sa is 40 nm or less, lubricant aggregation is less likely to occur, and coarse protrusions cannot be formed. Therefore, the quality of ultrathin ceramic green sheets is stable and preferred during manufacturing.

[0065] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can be used as the particles contained in layer B above. However, from the viewpoints of transparency and cost, silica particles and / or calcium carbonate particles are preferred. Other usable inorganic particles include alumina-silica composite oxide particles and hydroxyapatite particles. 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 lubricant detachment, light calcium carbonate with a surface treatment using a polyacrylic acid-based polymer is preferred.

[0066] The average particle size of the inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, particularly preferably 0.5 μm or more and 1.0 μm or less. If the average particle size of the inorganic particles is 0.1 μm or more, the release film exhibits good sliding properties, which is preferable. Furthermore, if the average particle size is 2.0 μm or less, there is no concern about adverse effects on the smoothness of the release layer surface; therefore, it is preferable to avoid the formation of pinholes in the ceramic green sheet.

[0067] In the layer on one side of the above-mentioned release layer, namely surface layer A, from the viewpoint of reducing pinholes, it is preferable not to use recycled materials to prevent the mixing of inorganic particles such as lubricants.

[0068] The thickness ratio of the layer on the side where the release layer is set, i.e., surface layer A, 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 less likely to be affected by particles contained in the surface layer B, etc., from inside the film, and the average surface roughness Sa of the area is more likely to meet the above range, which is preferable. If it is 50% or less of the total thickness of the substrate film, the proportion of recycled materials used in surface layer B can be increased, and the environmental impact is reduced, which is preferable.

[0069] 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 average surface roughness (Sa) of the lubricant contained in layer B preferably also meet the above-mentioned ranges.

[0070] In addition, in order to improve the adhesion of subsequent coatings such as release layers, or 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 in the film-making process, or corona treatment can be performed.

[0071] (release layer)

[0072] In this invention, a release layer is formed on one side of the substrate film. When using a substrate film having a surface layer A that is substantially free of inorganic particles, it is preferable to form the release layer on the surface layer A. By providing a release layer on the surface layer A that is substantially free of inorganic particles, a release layer surface with excellent smoothness can be achieved, and deformation and defects of the resin sheet provided on the release layer can be suppressed, which is therefore preferable.

[0073] The release layer is a cured product of a composition comprising cationic curable polydimethylsiloxane (a). The release layer exhibits characteristics that suppress poor curing caused by oxygen inhibition and allows for high cross-linking. This invention, for example, improves the solvent resistance of the release layer surface. By improving the solvent resistance of the release layer surface, it can suppress erosion by organic solvents used during ceramic green sheet molding and internal electrode printing, resulting in high peelability.

[0074] Furthermore, since cationic curable polydimethylsiloxane is cured under active energy rays, high temperatures above 130°C are not required during the curing reaction. Therefore, damage to the planarity of the release film caused by heat during processing can be suppressed. As a result, the introduction of foreign matter into the release film and release layer for resin sheet molding, as well as scratches, can be suppressed, and damage to the molded material such as ceramic green sheets caused by the transfer of foreign matter and scratches can be suppressed.

[0075] The normal peel force (I) and the peel force (II) after heating of the release layer in the release film of the present invention are as follows:

[0076] Release film with (II) / (I) = 1.00 or higher and 1.50 or lower.

[0077] The ratio of the normal peel force (I) to the peel force (II) after heating of the release layer of the present invention can be used to evaluate, for example, the degree of curing of the release layer by having specified conditions.

[0078] For release films, heat is sometimes applied during the process of molding resin sheets, such as ceramic green sheets, onto the release film and peeling them off.

[0079] The normal peel force (I) and the peel force after heating (II) in this invention are within a specified range, thereby exhibiting stable retention and peelability of ceramic green sheets before and after heating.

[0080] For example, it should not be interpreted according to a specific theory, but stable peelability can be exhibited if there is no difference between the normal peel force (I) and the peel force after heating (II), or if it is within the scope of the present invention. The ratio (II) / (I) of the normal peel force (I) to the peel force after heating (II) is 1.00 or more and 1.50 or less, more preferably 1.00 or more and 1.45 or less. For example, it can be 1.00 or more and 1.40 or less. For example, it can be 1.05 or more, or 1.10 or more.

[0081] If the ratio of the normal peel strength (I) to the peel strength after heating (II) is 1.50 or less, it indicates that the release layer has been fully cured with little unreacted material. This is preferred because it exhibits excellent peelability to resin sheets such as ceramic green sheets. Generally, the peel strength after heating is higher than the normal peel strength; therefore, a ratio of 1.00 or higher is preferred. Detailed evaluation methods are described later.

[0082] In this invention, the degree of polymerization of the release layer over time can be indirectly evaluated by measuring the normal peel force (I) and the peel force after heating (II) of the release film obtained by temporarily rolling up the release film for molding resin sheets into a roll and then unrolling it. Furthermore, the peel force can also be evaluated considering the effect of the planarity of the release layer caused by storage in a rolled state.

[0083] By setting a hydrophobic layer and storing it in rolls, the reaction of the release layer can be further carried out, resulting in a release layer with stable peel force and excellent surface shape, and a release film with excellent peel force after heating.

[0084] Furthermore, by ensuring that the ratio (II) / (I) of the normal peel force (I) to the peel force after heating (II) is between 1.50 and 1.00, and then winding and storing the film, the influence of the release layer on the surface shape can be further reduced compared to existing release films, maintaining high smoothness. Additionally, since this indicates that the release layer has fully cured, adhesion is less likely to occur in the rolled state, and the charge carried on the roll can be suppressed.

[0085] For example, the release layer is substantially free of particles with a diameter greater than 1.0 μm. Alternatively, particles with a diameter greater than 1 nm but less than 1.0 μm may also be present in the release layer. By being substantially free of inorganic particles with a diameter greater than 1.0 μm, the release layer can suppress the formation of pinholes in resin sheets requiring high smoothness, such as ceramic green sheets, thereby forming resin sheets with uniform film thickness.

[0086] In one embodiment, the release layer preferably has high smoothness. Therefore, it is preferable to provide the release layer of the present invention on a substrate film that is substantially free of inorganic particles, specifically substantially free of particles with a particle size of less than 1.0 μm, and preferably has a surface layer A that is substantially free of particles.

[0087] For example, a release layer that substantially does not contain particles with a particle size of less than 1.0 μm is preferably substantially free of particles with a particle size of more than 1.0 μm.

[0088] When a release layer is provided on a surface layer A that is substantially free of inorganic particles, the surface roughness Sa of the release layer region is less than 7 nm and the maximum protrusion height is less than 50 nm.

[0089] The release layer, by having such characteristics, can suppress the occurrence of pinholes in resin sheets, such as ceramic green sheets, which require high smoothness, and can form resin sheets with uniform film thickness.

[0090] The preferred release layer has an average surface roughness (Sa) of 7 nm or less and a maximum protrusion height (Sp) of 50 nm or less. The thin film surface on which the release layer is formed has the aforementioned average surface roughness and maximum protrusion height to prevent defects from occurring in the ceramic green sheet coated / formed thereon. If the surface roughness is 7 nm or less and the maximum protrusion height is 50 nm or less, no pinholes or other defects are generated during the formation of the ceramic green sheet, resulting in a good yield, which is preferable.

[0091] Furthermore, the release film of the present invention, by having the release layer and hydrophobic layer of the present invention, possesses excellent peelability to resin sheets, and when the resin sheet is wound on it and stored, the occurrence of pinholes, wrinkles, and misalignment can be suppressed. In addition, the present invention can suppress the increase of charge during roll-out. Thus, the release film of the present invention, due to its high smoothness and excellent peelability, not only allows for the good manufacture of resin sheets, but also improves the operability during film winding and transportation, suppresses the increase of charge during roll-out, thereby reducing the ingress of foreign matter.

[0092] In one embodiment, the average surface roughness (Sa) of the release layer is 5 nm or less, and the maximum protrusion height (Sp) is 30 nm or less. A lower maximum protrusion height is preferred. A smaller average surface roughness (Sa) is also preferred; it can be 0.1 nm or more, or 0.3 nm or more. Alternatively, the average surface roughness (Sa) can be 3 nm or less, for example, less than 2 nm.

[0093] The smaller the maximum protrusion height (Sp), the better; it can be above 1 nm or above 3 nm. Alternatively, the maximum protrusion height (Sp) can be below 25 nm or below 20 nm.

[0094] The release layer is preferably a cured product of a composition comprising at least a cationic curable polydimethylsiloxane (a). 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 most preferred. By having such functional groups, a cross-linked structure is formed by the cationic curing reaction, resulting in a release layer with excellent solvent resistance and excellent peelability, which is therefore preferred.

[0095] The viscosity of the cationic curable polydimethylsiloxane (a) is preferably 100 mPa·s or more and 10,000 mPa·s or less, more preferably 100 mPa·s or more and 5,000 mPa·s or less, and even more preferably 100 mPa·s or more and 1,000 mPa·s or less. If it is 100 mPa·s or more, the amount of unreacted component is reduced when stored in a roll, resulting in a fully cured release layer, which is preferred. If it is 10,000 mPa·s or less, it exhibits solubility for the organic solvents contained in the release layer forming composition, allowing for uniform coating, which is also preferred. It should be noted that the viscosity in this invention is a value measured at 25°C.

[0096] 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.

[0097] 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.

[0098] In the release layer forming composition of the present invention, other resins may be included in addition to cationic curable polydimethylsiloxane (a). When a release layer is formed on the surface layer A of a substrate film that is substantially free of inorganic particles, a release layer formed by curing cationic curable polydimethylsiloxane (a) as the main component is preferred. In this case, even if the film thickness of the release layer is thin, a release layer with extremely high smoothness can be formed, which is therefore preferable. Furthermore, because the film thickness of the release layer is thin, the curing reaction is easy to carry out, processing can be performed at a higher speed, and the release layer can be obtained economically.

[0099] 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.

[0100] It should be noted that, in this invention, when cationic curable polydimethylsiloxane (a) is the main component, the composition contains at least 50 parts by weight, for example more than 50 parts by weight, preferably more than 70 parts by weight, and for example more than 80 parts by weight, relative to 100 parts by weight of the resin solids component of the release layer. In one embodiment, it contains more than 90 parts by weight. Alternatively, the cationic curable polydimethylsiloxane (a) may be substantially included in all the resin solids component of the release layer.

[0101] In the release layer forming composition of the present invention, in addition to cationic curable polydimethylsiloxane (a), a cationic curable resin (b) without an organosilicon backbone may also be contained. In this case, (b) is a different resin from (a), and resin (b) is a substance without a polydimethylsiloxane structure.

[0102] In one embodiment, the release layer forming composition, in addition to containing a cationic curable polydimethylsiloxane (a), further contains a cationic curable resin (b) that does not have a silicone backbone. Examples of the cationic curable resin (b) that does not have a silicone backbone include polymers and monomers having two or more cationic curable functional groups within their molecules and lacking a silicone backbone. Preferably, the resin has two or more epoxy groups or alicyclic epoxy groups, and more preferably, it has two or more alicyclic epoxy groups. For example, the number of alicyclic epoxy groups may be six or less.

[0103] 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 green sheet, making it preferable.

[0104] In one embodiment, since the release layer forming composition simultaneously comprises a cationic curable resin (b) without an organosilicon backbone and polydimethylsiloxane (a), a release layer with high smoothness can be achieved. By forming a release layer containing resin (b), 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 energy rays, a release layer with high smoothness is obtained. Although it should not be explained by a specific theory, it can be speculated that during the drying process of the release layer forming composition during release layer processing, (b) 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.

[0105] The cationic curable resin (b) 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 resin (b) 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.

[0106] Cationic curable resins (b) without a silicone 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 Kasei Corporation; and THI-DE, DE-102, and DE-103 manufactured by ENEOS Corporation. Examples of resins with epoxy groups include EPICLON (registered trademark) 830, 840, 850, 1051-75M, N-665, N-670, N-690, N-673-80M, and N-690-75M manufactured by DIC Corporation; and DENACOL (registered trademark) EX-611, EX-313, and EX-321 manufactured by Nagase ChemteX Corporation.

[0107] In the manner in which the release layer contains a cationic curable resin (b) without a silicone framework, the content of the cationic curable resin (b) without a silicone framework may exceed 50 parts by mass relative to the total 100 parts by mass of the cationic curable polydimethylsiloxane (a) and the cationic curable resin (b) in the release layer, preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0108] By including a cationic curable resin (b) content of more than 50 parts by mass, for example, 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, and the flatness is not deteriorated, which is also preferred. Although a higher content of cationic curable resin (b) results in a release layer with better smoothness, in order to contain cationic curable polydimethylsiloxane (a) and ensure peelability, the cationic curable resin (b) is preferably 99.9% by mass or less.

[0109] In this invention, the release layer formed by curing the release layer composition contains a compound (cured product) from a cationic curable resin (b) that does not have a silicone framework. In this specification, the compound from (b) present in the release layer is sometimes simply referred to as a cationic curable resin (b) that does not have a silicone framework.

[0110] When the release layer forming composition comprises cationic curable polydimethylsiloxane (a) and cationic curable resin (b), 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 resin (b) 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.

[0111] When the release layer forming composition comprises cationic curable polydimethylsiloxane (a) and cationic curable resin (b), the film thickness of the release layer is preferably 0.01 μm or more and 1.0 μm or less, more preferably 0.05 μm or more and 0.5 μm or less. If it is 0.01 μm or more, a smooth release layer is obtained, which is preferred. If it is 1.0 μm or less, curling does not occur, resulting in a release film with excellent planarity, which is also preferred.

[0112] 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).

[0113] There are no particular limitations on the acid-generating agent used; any general acid-generating agent can be used. However, it is preferred to use a photoacid-generating agent that generates acid under ultraviolet light, which can suppress heat during processing and create a release layer with excellent planarity.

[0114] 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.

[0115] 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 fluorine anions with perfluoroalkyl or organic groups, or other anionic components can be used.

[0116] The amount of photoacid generator 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) and cationic curable resin (b) in the release layer. It is even more preferably 1 to 5% by mass. Setting it to 0.1% by mass or more ensures that the amount of acid generated will not become insufficient, leading to incomplete curing, which is therefore preferable. Furthermore, setting it to 10% by mass or less ensures that the amount of acid generated is appropriate, suppressing the transfer of acid to the ceramic green sheet to be formed, which is also preferable.

[0117] In this specification, the total of 100 parts by mass of cationic curable polydimethylsiloxane (a) and cationic curable resin (b) 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.

[0118] In this invention, the release layer may contain additives such as adhesion improvers and antistatic agents, without hindering the effectiveness of the invention, but preferably it is free of particles. By ensuring that the release layer is free of particles, the deterioration of the smoothness of the release layer surface and the mixing of particles into the resin sheet caused by particle shedding can be suppressed. To improve adhesion to the substrate, the polyester film surface may be pretreated with anchoring coating, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0119] (Hydrophobic layer)

[0120] A hydrophobic layer is formed on the side of the substrate film opposite to the side where the release layer is provided. When the release layer is provided on surface layer A, which contains virtually no inorganic particles or can have a very small number of particles, a hydrophobic layer is formed on surface layer B on the other side of the substrate film.

[0121] For example, the hydrophobic layer substantially does not contain particles larger than 1.0 μm. In this method, particles with a diameter of 1 nm or larger but smaller than 1.0 μm may also be present in the hydrophobic layer. Since the release layer is substantially free of inorganic particles larger than 1.0 μm, it is preferable that when the release film is rolled into a roll, there is no concern about deformation (defects) of the resin sheet due to the influence of particles present on the reverse release surface (hydrophobic layer).

[0122] The hydrophobic layer preferably contains substantially no particles with a particle size smaller than 1.0 μm, and more preferably no particles at all. By substantially containing no particles with a particle size smaller than 1.0 μm, when the resin sheet is formed on the release film and stored in a roll, there is no concern about the shape of the particles in the hydrophobic layer transferring and deforming the resin sheet, which is preferable. Furthermore, there is no concern about particles in the hydrophobic layer detaching and becoming mixed into the resin sheet, which is also preferable. In particular, by being substantially free of particles, the above-mentioned effects can be achieved more effectively.

[0123] For example, the surface layer A, which substantially does not contain particles with a particle size smaller than 1.0 μm, is preferably also substantially free of particles with a particle size larger than 1.0 μm. It should be noted that this method is the same as the method that substantially does not contain particles.

[0124] The hydrophobic layer is preferably a cured product of a composition comprising cationic curable polydimethylsiloxane (a). Because the hydrophobic layer has such characteristics that when the release film is rolled into a roll and stored, it is in contact with the release layer, thus the release layer is not affected by curing obstacles caused by moisture, and the reaction proceeds, which is preferable. Furthermore, since the release layer also comprises cationic curable polydimethylsiloxane (a), when stored in a roll, the charge sequence of the contacting release layer is close, and charging is suppressed, which is also preferable. By suppressing charging, there is no peel charge, and resin sheets such as ceramic green sheets can be peeled off with low force and without defects. In addition, it can suppress the adhesion of minute environmental foreign matter and film debris generated during slitting due to static electricity. As a result, it can prevent foreign matter from contaminating the resin sheet. For example, for the release film of the present invention, charging can also be suppressed during the roll-out process performed before the resin sheet is formed, thus preventing contamination of the release layer. Furthermore, even with resin sheets formed on the release layer, the roll-out charge can be suppressed, thus enabling the various effects described in this specification to be achieved.

[0125] The water contact angle of the hydrophobic layer of the present invention is 90° or more and 130° or less. By setting the water contact angle to this range, it is possible to reduce the amount of moisture adsorbed on the release surface of the substrate film, and there is no concern about causing curing obstacles to the release layer in the roll state, which is preferable.

[0126] In one approach, the water contact angle of the hydrophobic layer can be greater than 95° and less than 130°, for example, greater than 98° and less than 130°.

[0127] In this invention, in particular, the water contact angle of the hydrophobic layer is within the aforementioned range, and the hydrophobic layer contains the cationic curable polydimethylsiloxane (a) contained in the release layer. This reduces the amount of moisture adsorbed on the reverse release surface of the substrate film, thus more significantly resolving the problem of curing obstacles caused by the release layer when in contact with the film in a rolled state. Furthermore, when the film is rolled into a roll, the adhesion of foreign matter to the release layer can be suppressed, maintaining the high smoothness of the release layer. Moreover, it becomes less prone to moisture absorption during storage and transport in a rolled state, preventing deterioration of the roll appearance quality such as moisture-absorbing wrinkles and winding misalignment, which is therefore preferable.

[0128] The hydrophobic layer in this invention can be a cured product of a composition comprising a cationic curable resin (b) without an organosilicon backbone, in addition to a cationic curable polydimethylsiloxane (a). By using the cationic curable resin (b), the elastic modulus of the hydrophobic layer can be improved. Forming a hydrophobic layer with a high elastic modulus not only improves the operability of the release film but also suppresses unwinding charge, which is preferred. Increasing the elastic modulus of the hydrophobic layer improves the sliding properties (makes it easier to slide) between the release layer and the hydrophobic layer during roll storage. This should not be interpreted limited to a specific theory, but if the hydrophobic layer is easily smoothed, stress applied perpendicular to the surface of the release film becomes easier to escape in the horizontal direction. Therefore, the adhesion force between the release layer and the resin sheet or hydrophobic layer during roll storage can be reduced, and charging can be suppressed, which is preferred.

[0129] As an example of forming a hydrophobic cationic curable polydimethylsiloxane (a) and a cationic curable resin (b), the same examples as those used in the aforementioned release layer can be used. The composition of the release layer and the hydrophobic layer need not be exactly the same; as long as both the release layer and the hydrophobic layer contain cationic curable polydimethylsiloxane (a), a release film with the effects of the present invention can be obtained.

[0130] When a hydrophobic layer is obtained by curing a composition with cationic curable polydimethylsiloxane (a) as the main component, the film thickness of the hydrophobic layer is preferably 0.001 μm or more and 0.050 μm or less. If it is 0.001 μm or more, the curing hindrance suppression effect of the release layer in contact with the hydrophobic layer becomes sufficient, which is preferred. If it is 0.050 μm or less, the elastic modulus of the hydrophobic layer decreases, which can prevent the increase of charge during roll-out and the occurrence of adhesion in the rolled state, which is also preferred.

[0131] When the cured product of a composition comprising cationic curable polydimethylsiloxane (a) and cationic curable resin (b) without an organosilicon backbone becomes a hydrophobic layer, the content of cationic curable resin (b) without an organosilicon backbone 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 a total of 100 parts by mass. By making the content of cationic curable resin (b) 80% by mass or more, it becomes the main component in the release layer, thereby creating a hydrophobic layer with high crosslinking density and high elastic modulus, which is preferable. The film thickness of the hydrophobic layer is preferably 0.001 μm to 0.5 μm, more preferably 0.001 μm to 0.3 μm. If the film thickness of the hydrophobic layer is 0.001 μm, the curing hindrance suppression effect and the charge suppression effect of the release layer become sufficient, which is preferable. If it is 0.5 μm or less, the unevenness on the reverse release surface side will not be completely filled, resulting in excellent transportability and no adhesion during winding, which is preferable.

[0132] The surface of the hydrophobic layer is preferably rougher than the surface of the release layer. By making the surface of the hydrophobic layer rougher than the release layer, the transportability and winding properties of the roll are improved, and scratches, foreign matter ingress, and increased static charge during roll-out can be prevented. Therefore, this is preferred.

[0133] The desired effect can be achieved as long as the surface roughness Sa of the hydrophobic layer is greater than that of the release layer. Preferably, Sa is in the range of 1 to 40 nm, more preferably in the range of 2 to 30 nm, and even more preferably in the range of 3 to 20 nm. Sa is preferably 1 nm or more, which can prevent the deterioration of the transportability and winding properties of the roll. Sa is preferably 40 nm or less, which can prevent the surface shape of the hydrophobic layer from being transferred to the resin sheet and causing defects.

[0134] In this invention, a cationic curing reaction is required to form the hydrophobic layer. Therefore, the hydrophobic layer forming composition preferably contains an acid-generating agent (c). The amount and type of acid-generating agent used are the same as those for the aforementioned release layer.

[0135] Here, the water contact angle in the hydrophobic layer may include an acid-generating agent (c) within the scope of the present invention.

[0136] It should be noted that even if the composition forming the release layer and the composition forming the hydrophobic layer contain the same resin, the amount of solvent contained in each composition may differ. Therefore, the identification of the resulting polymer structure and the specificity based on its claims are not easy and may be impractical.

[0137] (Method for manufacturing release film)

[0138] In this invention, the coating of the release layer forming composition that forms the release layer is preferably carried out online during the manufacturing process of the polyester film or offline after the manufacturing of the polyester film.

[0139] In the case of online coating, the following method is preferred: a coating liquid containing a release resin dissolved or dispersed is applied to a film that is stretched and uniaxially oriented along the film flow direction (longitudinal direction), and then stretched and biaxially oriented in the transverse direction (direction orthogonal to the film flow direction) to form a release layer.

[0140] When coating offline, the following method is used: a coating solution containing a release resin is applied to one side of a biaxially oriented polyester film, and after the solvent is removed by drying, it is then dried by heating, heat curing, or UV curing.

[0141] When applying coatings online, water-based coatings are preferred. There are no particular limitations on the type of water-based coating, but the addition of water-soluble organic solvents, such as alcohols, is preferred.

[0142] There are no particular limitations on the coating solution used for offline coating, but organic solvents are preferred, especially solvents with a boiling point of 90°C or higher. By adding a solvent with a boiling point of 90°C or higher, bumping during drying can be prevented, the coating film can be leveled, and the smoothness of the dried coating film surface can be improved.

[0143] There are no particular limitations on the method for forming the hydrophobic layer. It can be processed simultaneously with the release layer on both sides, or processed on one side first and then on the opposite side. In the latter case, it is preferable to process the release layer first and then the hydrophobic layer. This is because the release layer is directly laminated with resin sheets, and therefore needs to be smoother than the hydrophobic layer. Therefore, when the hydrophobic layer is processed first, the sliding properties on the back side are good, wrinkles are less likely to be introduced during the processing of the release layer, and the coating can be applied more evenly, which is preferred.

[0144] The hydrophobic layer is preferably processed offline after the polyester film is formed, rather than online, where it is coated during the polyester film forming process. Offline processing allows for precise control of tension during coating and winding, resulting in superior operational performance.

[0145] The coating method for the aforementioned release layer forming composition and hydrophobic layer forming composition can be any known coating method, such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire rod coating, die coating, spray coating, air knife coating, etc.

[0146] For the release film of the present invention, the substrate film is transported roll to roll during the processing of the release layer and the hydrophobic layer. Therefore, after the processing of the release layer and the hydrophobic layer, the release film is wound up and stored in roll form. In addition, the molding and peeling of the resin sheet are also performed roll to roll.

[0147] The tension when winding the release film into a roll is preferably 10 N / m to 300 N / m. A winding tension of 10 N / m or higher is preferred to prevent winding misalignment. Furthermore, it prevents unwinding during storage in a roll, eliminates concerns about scratches infiltrating the release layer, and avoids increased charge during roll-out. A winding tension of 300 N / m or lower is preferred to prevent deformation and adhesion of the release film due to varying winding tightness.

[0148] When winding the release film into a roll, it is preferable to use a contact roller. The contact pressure of the contact roller is preferably 100 to 3000 N / m. If it is 100 N / m or more, it can reduce the accompanying gas mixed in during winding and suppress the occurrence of winding misalignment, which is preferable. If it is 3000 N / m or less, it can suppress the deformation of the release film based on the contact roller pressure and obtain a release film with excellent planarity, which is also preferable.

[0149] (Other features)

[0150] In this invention, the unwinding charge during the unwinding of the release film stored in a roll can be suppressed to a low level. The charge carried when unwinding the release film at a rate of 100 m / min is preferably below ±1.0 kV. If it is below ±1.0 kV, there is less concern about minute foreign matter adhering to the release film during the process, which is preferable. Furthermore, the peeling charge during the peeling of the resin sheet is also suppressed to a low level, allowing for peeling with a lower and more uniform force, which is also preferable.

[0151] For storage in the rolled-up state, there are no particular restrictions as long as the storage environment is a cool, shaded indoor place that avoids direct sunlight and high temperatures. It can be stored in a humidity-controlled environment with temperature management, as long as the humidity is within the range of 20% to 90% RH and the temperature is within the range of -5°C to 50°C, thus achieving the effects of this invention.

[0152] The peel strength in this invention is measured as follows: A release film with a release layer and a hydrophobic layer, stored in a roll at 40–50% RH and 20–25°C for 3 days, is then measured using the unrolled and collected release film. By storing the film in a roll after applying the hydrophobic layer, the reaction of the release layer is completed, resulting in a release film with excellent peel strength. The peel strength in this invention is measured by applying an adhesive tape (Nitto Denko Corporation's "31B") to the surface of the release film and performing a T-shaped peel at a stretching speed of 300 m / min. Detailed evaluation methods are described below.

[0153] The normal peel force (I) of the release layer is preferably 100 mN / 50 mm or more and 1500 mN / 50 mm or less, more preferably 100 mN / 50 mm or more and 1300 mN / 50 mm or less, and even more preferably 100 mN / 50 mm or more and 1000 mN / 50 mm or less. If it is 100 N / 50 mm or more, there is no concern about the resin sheet lifting or peeling during transportation, and the retention is excellent, so it is preferred. If it is 1500 mN / 50 mm or less, the resin sheet can be peeled off without damage, which is also preferred.

[0154] The peel strength (II) of the release layer after heating is preferably 150 mN / 50 mm or more and 2250 mN / 50 mm or less, more preferably 150 mN / 50 mm or more and 1950 mN / 50 mm or less, and even more preferably 150 mN / 50 mm or more and 1500 mN / 50 mm or less. Since heat is applied to the release film during the peeling process after molding the resin sheet onto it, the peel strength after heating allows for a more detailed evaluation of the release film's peelability. A value of 150 mN / 50 mm or more indicates excellent retention of the ceramic green sheet, and is therefore preferred. A value of 2250 mN / 50 mm or less indicates less unreacted material in the release layer, resulting in excellent peeling of the resin sheet, and is also preferred.

[0155] While not limited to a specific theory, in this invention, the release layer contains cationic curable polydimethylsiloxane (a), and the water contact angle of the hydrophobic layer is 90° or more and 130° or less. This suppresses the interference of time-dependent reactions of the cationic curable resin caused by the influence of moisture, which is believed to exist in trace amounts on the reverse release surface of the substrate film, thus solving the problem of insufficient curing of the release layer. As a result, the peel force (II) can be brought into the above range after heating. For example, in the process of molding resin sheets, when processing is carried out at a temperature of 30°C or more and 120°C or less, the resin sheet forming composition can be well maintained, and the obtained resin sheet can be easily peeled off.

[0156] Therefore, in this invention, the retention of the resin sheet forming composition and the peeling after heating can be balanced well. For example, these effects can also be achieved when the ceramic green sheet has an extremely thin thickness of less than 1.0 μm.

[0157] The ratio of the normal peel force (I) to the peel force after heating (II): (II) / (I) is preferably 1.00 or more and 1.50 or less. A large ratio of (II) / (I) indicates the presence of unreacted material in the release layer, meaning that the curing of the release layer has not been complete. If (II) / (I) is 1.50 or less, the release layer comes into contact with the hydrophobic layer when stored in a roll, thus preventing poor curing due to moisture, and the curing of the release layer is complete, which is preferable. The peel force after heating (II) is usually greater than the normal peel force (I), therefore, (II) / (I) is preferably 1.0 or more.

[0158] (Resin sheet)

[0159] In one embodiment, the release film of the present invention is not particularly limited as long as it is a resin sheet, and can be used in the manufacture of adhesives and optical films. In another embodiment, it is a release film for molding resin sheets containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, minerals, etc., such as calcium carbonate, silica particles, aluminum particles, barium titanate particles, etc.

[0160] Examples of resins include polyvinyl acetal resin and poly(meth)acrylate resin.

[0161] Because the present invention has a highly smooth release layer and a back layer with excellent smoothness, operability and antistatic properties, it can suppress defects that may be caused by inorganic compounds, such as resin sheet breakage and difficulty in peeling the resin sheet from the release layer, even when these inorganic compounds are included in the resin sheet.

[0162] The resin components used to form resin sheets can be selected appropriately based on their intended use.

[0163] In one embodiment, the resin sheet containing the inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. In another embodiment, the thickness of the resin sheet is 0.2 μm or more and 1.0 μm or less.

[0164] (Ceramic green plates and ceramic capacitors)

[0165] 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.

[0166] In one embodiment, the release film of the present invention is a release film for manufacturing ceramic green sheets, used to manufacture such multilayer ceramic capacitors.

[0167] For example, the ceramic green sheet manufacturing method using the release film for ceramic green sheet manufacturing of the present invention to form ceramic green sheets can form ceramic green sheets with a thickness of 0.2 μm to 1.0 μm.

[0168] More specifically, for example, a ceramic green sheet is manufactured as follows: First, the release film of the present invention is used as a carrier film, a ceramic slurry for forming a ceramic substrate is coated, and then dried. The ceramic green sheet is required to be extremely thin, with a thickness of 0.2 to 1.0 μm. A conductive layer for forming a first or second internal electrode is printed on the coated and dried ceramic green sheet. The ceramic green sheets, the ceramic green sheet with the conductive layer for forming the first internal electrode printed, and the ceramic green sheet 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 substrate. The unprocessed ceramic substrate is fired to obtain a ceramic substrate. Then, by forming the first and second external electrodes, a multilayer ceramic capacitor can be completed.

[0169] Example

[0170] 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.

[0171] (Thickness Measurement)

[0172] 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) manufactured by Nippon Electron, 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 Electron, FE-3000) was used for measurement.

[0173] (Surface roughness Sa, maximum protrusion height Sp)

[0174] 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.

[0175] (Measurement conditions)

[0176] • Measurement mode: WAVE mode

[0177] Objective lens: 50x

[0178] ·0.5× lens barrel

[0179] • Measurement area: 187μm × 139μm

[0180] (Analysis conditions)

[0181] • Horizontal correction: 4 corrections

[0182] • Interpolation processing: Full interpolation

[0183] (Normal peeling force (I))

[0184] The release films for manufacturing resin sheets obtained in each embodiment and comparative example were wound into rolls with a width of 400 mm and a length of 6000 m to obtain release film rolls. At this time, the winding tension was 150 N / mm and the contact roller pressure was 700 N / m. The obtained film rolls were stored at 20–25°C and 40–50% RH for 3 days before being unwound, and the release films for testing were collected. Adhesive tape ("31B" manufactured by Nitto Denko Corporation) was adhered to the release layer surface of the release film for testing, and the release film with adhesive tape was cut into strips with a width of 25 mm and a length of 150 mm. The cut release films with adhesive tape were pressed together using a 5 kg pressing roller and placed at a temperature of 22°C and a humidity of 60% for 20 hours. Then, one end of the adhesive tape was fixed, and the other end of the release film was loaded. The film was stretched at a speed of 300 mm / min on the release film side, and the T-shaped peel test was performed. The tensile testing machine ("AUTOGRAPHAG-X" manufactured by Shimadzu Corporation) was used in the test.

[0185] (Peeling force after heating (II))

[0186] Similar to the aforementioned normal peel force (I), a release film was collected for evaluation. An adhesive tape (manufactured by Nitto Denko Corporation, trade name "31B") was adhered to the surface of the release layer. The release film with the adhesive tape was cut into strips 25 mm wide and 150 mm long. The cut release films with the adhesive tape were pressed together using a 5 kg pressing roller and then heated in an oven at 70°C for 20 hours. Afterward, one end of the adhesive tape was fixed, and the other end of the release film was held. The release film was stretched and peeled at a speed of 300 mm / min, and the result was measured using a T-shaped peel test. A tensile testing machine (manufactured by Shimadzu Corporation, "AUTOGRAPHAG-X") was used for the test.

[0187] (Unwinding with electrical charge)

[0188] The release film for manufacturing resin sheets obtained in each embodiment and comparative example was wound into a roll with a width of 400 mm and a length of 6000 m to obtain a release film roll. At this time, the roll was wound with a winding tension of 150 mN / mm and a contact roller pressure of 700 N / m. After storing the release film roll in an environment of 20–25°C and humidity below 40–50% RH% for 30 days, the charge carried when unwound at 100 m / min was measured using a Kasuga Electric Co., Ltd. "KSD-0103" instrument. For the charge carried, measurements were taken every 500 m of unwound length for the portion immediately after unwinding (100 mm), and the average value was calculated.

[0189] 〇: Below ±1.0kV

[0190] ×: ±1.0kV or more

[0191] (Water contact angle)

[0192] The contact angle of water in contact with the demolding surface was measured using an automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: DM-701) at 22°C and 60% RH. The amount of water added was 1.8 μL, and the contact angle value was used 60 seconds after the addition.

[0193] (Preparation of polyethylene terephthalate granules (PET(I)))

[0194] 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 Sb atom concentration of 160 ppm relative to the generated PET. These slurries were continuously fed into 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). 2Under 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.

[0195] (Preparation of polyethylene terephthalate granules (PET(II)))

[0196] 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 (hereafter referred to as PET(II)).

[0197] (Manufacturing of the laminated thin film X1)

[0198] 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 underwent heat treatment 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.

[0199] (Manufacturing of laminated thin film X2)

[0200] 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.

[0201] (Mold release layer forming composition Y1)

[0202] 49.833 parts by weight of methyl ethyl ketone

[0203] 49.833 parts by weight of toluene

[0204] Cationic cured polydimethylsiloxane (a):

[0205] 0.316 parts by weight of polydimethylsiloxane containing alicyclic epoxy groups

[0206] (Product name: Siliconease UV POLY215, manufactured by Arakawa Chemical Industry Co., Ltd., 100% solid content)

[0207] Acid-producing agent (c) 0.018 parts by weight

[0208] (Product Name: UV CATA211, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 18%)

[0209] (Mold release layer forming composition Y2)

[0210] 47.361 parts by weight of methyl ethyl ketone

[0211] 47.361 parts by weight of toluene

[0212] Cationic cured polydimethylsiloxane (a) 0.250 parts by weight

[0213] (Product name: Siliconease UV POLY215, manufactured by Arakawa Chemical Industry Co., Ltd., 100% solid content)

[0214] Cationic curable resins without an organosilicon framework (b):

[0215] 4.750 parts by weight of 2-functional alicyclic epoxy monomer

[0216] (Product name: Celoxide2021P, manufactured by Daicel Corporation, 100% solid content)

[0217] Acid-producing agent (c) 0.278 parts by weight

[0218] (Product Name: UV CATA211, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 18%)

[0219] (Mold release layer forming composition Y3)

[0220] 44,900 parts by weight of methyl ethyl ketone

[0221] 44,900 parts by weight of toluene

[0222] 9,500 parts by weight of dipentaerythritol hexaacrylate

[0223] (Product Name: A-DPH, manufactured by Shin-Nakamura Chemical Co., Ltd., 100% solid content)

[0224] 0.500 parts by weight of polydimethylsiloxane containing acryloyl groups

[0225] (Product Name: BYK UV3500, manufactured by BYK Japan Co., Ltd., 100% solid content)

[0226] 0.200 parts by weight of initiator

[0227] (Product name: Omnirad 907, manufactured by IGM Resins, 100% solids concentration)

[0228] (Mold release layer forming composition Y4)

[0229] 47.361 parts by weight of methyl ethyl ketone

[0230] 47.361 parts by weight of toluene

[0231] Cationic cured polydimethylsiloxane (a):

[0232] 0.250 parts by weight of side-chain epoxy-modified polydimethylsiloxane

[0233] (Product name: KF-101, manufactured by Shin-Etsu Chemical Industry Co., Ltd., 100% solid content)

[0234] Cationic curable resins without an organosilicon framework (b)

[0235] 4.750 parts by weight of 3-functional epoxy resin

[0236] (Product name: Denacol EX-421, manufactured by Nagase ChemteX Corporation, 100% solids concentration)

[0237] Acid-producing agent (c) 0.278 parts by weight

[0238] (Product Name: UV CATA211, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 18%)

[0239] (Hydrophobic layer forming composition Z1)

[0240] 69.766 parts by weight of methyl ethyl ketone

[0241] 29,900 parts by weight of toluene

[0242] Cationic cured polydimethylsiloxane (a):

[0243] 0.316 parts by weight of polydimethylsiloxane containing alicyclic epoxy groups

[0244] (Product Name: Siliconease UV POLY200, manufactured by Arakawa Chemical Industry Co., Ltd., 100% solid content)

[0245] Acid-producing agent (c) 0.018 parts by weight

[0246] (Product Name: UV CATA211, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 18%)

[0247] (Hydrophobic layer forming composition Z2)

[0248] 71.041 parts by weight of methyl ethyl ketone

[0249] 23.681 parts by weight of toluene

[0250] Cationic cured polydimethylsiloxane (a) 0.250 parts by weight

[0251] (Product Name: Siliconease UV POLY200, manufactured by Arakawa Chemical Industry Co., Ltd., 100% solid content)

[0252] Cationic curable resins without an organosilicon framework (b):

[0253] 4.750 parts by weight of 2-functional alicyclic epoxy monomer

[0254] (Product name: Celoxide2021P, manufactured by Daicel Corporation, 100% solid content)

[0255] Acid-producing agent (c) 0.278 parts by weight

[0256] (Product Name: UV CATA211, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 18%)

[0257] (Hydrophobic layer forming composition Z3)

[0258] 47.361 parts by weight of methyl ethyl ketone

[0259] 47.361 parts by weight of toluene

[0260] Cationic curable resins without an organosilicon framework (b):

[0261] 5,000 parts by weight of 2 functional alicyclic epoxy monomers

[0262] (Product name: Celoxide2021P, manufactured by Daicel Corporation, 100% solid content)

[0263] Acid-producing agent (c) 0.278 parts by weight

[0264] (Method for forming the release layer)

[0265] Using a reverse gravure coating machine, the release layer forming compositions Y1 to Y4 are coated onto surface layer A of laminated film X1 or one side of laminated film X2, so that the dried film thickness reaches the specified thickness. Next, after drying in hot air at 90°C for 20 seconds, it is immediately irradiated with ultraviolet light (100 mJ / cm²) using an electrodeless lamp (H valve manufactured by Heraeus). 2 The release layer is formed by unwinding the roll-to-roll process. That is, the roll of laminated film is continuously coated, dried, and irradiated with ultraviolet light, and then rolled into a roll to obtain a roll of release film with a release layer.

[0266] (Methods for forming a hydrophobic layer)

[0267] Using a reverse gravure coating machine, the hydrophobic layer forming compositions Z1 to Z3 are applied to the side of the substrate film without a release layer, resulting in a film thickness of the specified thickness after drying. Next, after drying in hot air at 90°C for 20 seconds, the film is immediately irradiated with ultraviolet light (100 mJ / cm²) using an electrodeless lamp (H valve manufactured by Heraeus). 2 A hydrophobic layer is formed. The formation of the hydrophobic layer is carried out roll to roll. That is, the release film with the release layer is unwound, coated, dried, and irradiated with ultraviolet light in sequence, and then rolled into a roll to obtain a release film roll with both the release layer and the hydrophobic layer.

[0268] (Example 1)

[0269] A release layer is coated onto surface layer A of a laminated film X1 to form composition Y1. After the release layer is formed, a hydrophobic layer is coated onto surface layer B to form composition Z1, thereby obtaining a release film roll for resin sheet molding. The thicknesses of the release layer and the hydrophobic layer are formed in the manner shown in Table 1. Release film samples are rolled out from the obtained release film roll and collected for various evaluations. The film composition and various physical properties are shown in Table 1A.

[0270] (Examples 2-11)

[0271] A release film roll for resin sheet molding was obtained using the same method as in Example 1, comprising the substrate film, release layer, and hydrophobic layer as shown in Table 1. Release film samples were rolled out from the obtained release film rolls and collected for various evaluations. The film composition and various physical properties are shown in Table 1A or Table 1B.

[0272] This invention features a hydrophobic layer on the side of the substrate film opposite to the release layer. Therefore, when the release film is stored in a roll, the release layer contacts the hydrophobic layer, eliminating concerns about poor curing of the release layer due to moisture and resulting in excellent peelability. Furthermore, the presence of cationic curable polydimethylsiloxane on both the release layer and the hydrophobic layer suppresses static electricity buildup during unwinding. Thus, this invention can suppress the adhesion of minute environmental contaminants during processing, film debris generated during slitting, etc., due to static electricity, and can inhibit resin sheet contamination. Additionally, for example, for resin sheets with a thickness of 0.2 μm or more and 1.0 μm or less, peeling static electricity is suppressed, allowing for peeling with low peeling force.

[0273] (Comparative Examples 1 to 5)

[0274] A release film for resin sheet molding was obtained using the same method as in Example 1, comprising the substrate film, release layer, and hydrophobic layer as shown in Table 1. Comparative Examples 1 to 4 are as follows: Each evaluation was performed using a roll of release film with a release layer but without a hydrophobic layer. The film composition and various physical property values ​​are shown in Table 1B.

[0275] In Comparative Example 1, because a free radical-curing resin was used in the release layer instead of cationic-curing polydimethylsiloxane (a), poor curing occurred due to oxygen inhibition. The ratio of the peel force (II) after heating to the normal peel force (I) was high, indicating deterioration in peelability. Furthermore, the unwinding charge was also high. Comparative Examples 2-4 lacked a hydrophobic layer (a hydrophobic layer with a water contact angle of 90° or more and 130° or less). Therefore, when the release film was stored in a roll, the influence of moisture hindered the time-dependent reaction of the release layer, resulting in poor curing and deterioration in peelability. Furthermore, the unwinding charge was also high. In Comparative Example 5, the water contact angle of the hydrophobic layer was below 90°. Therefore, when the release film was stored in a roll, the effect of suppressing curing inhibition of the release layer was insufficient, indicating deterioration in peelability and unwinding charge.

[0276] [Table 1A]

[0277]

[0278] [Table 1B]

[0279]

[0280] Industrial availability

[0281] According to the present invention, by having a release layer on one side of the substrate film and providing a hydrophobic layer on the reverse release surface of the substrate film, a release film with excellent peelability and low unwinding charge is provided, and ultra-thin resin sheets with a thickness of less than 1 μm can be manufactured without worrying about producing defects.

Claims

1. A release film for molding resin sheets, comprising: a substrate film and a release layer disposed on one side of the substrate film. The release film for molding resin sheets has a hydrophobic layer on the side of the substrate film opposite to the release layer. The release layer is a layer formed from a cured composition of a cationic curable polydimethylsiloxane (a). The water contact angle of the hydrophobic layer is greater than 90° and less than 130°. The normal peel force (I) and the peel force (II) after heating of the release film obtained by temporarily rolling up and unwinding the release film for molding the resin sheet are as follows: The peel force after heating (II) / peel force under normal conditions (I) is greater than or equal to 1.00 and less than or equal to 1.

50. The average surface roughness Sa of the release layer is less than 5 nm, the average surface roughness Sa of the hydrophobic layer is in the range of 1 to 40 nm, and the average surface roughness Sa of the hydrophobic layer is greater than that of the release layer.

2. The release film for resin sheet molding according to claim 1, wherein, The normal peel force (I) of the release layer in the release film obtained by unwinding is less than 1500mN / 50mm.

3. The release film for resin sheet molding according to claim 1, wherein, When the release film roll obtained by winding the resin sheet into a roll is released at a speed of 100 m / min, the charge is less than ±1 kV.

4. The release film for resin sheet molding according to claim 1, wherein, The hydrophobic layer is formed from a cured product of a composition having cationic curable polydimethylsiloxane (a).

5. The release film for resin sheet molding according to claim 1, wherein, The thickness of the hydrophobic layer is greater than 0.001 μm and less than 0.5 μm.

6. The release film for resin sheet molding according to claim 1, wherein, The release layer and the hydrophobic layer are substantially free of particles with a diameter greater than 1.0 μm.

7. The release film for resin sheet molding according to claim 1, wherein, The substrate film is a polyester film having a surface layer A that is substantially free of particles with a particle size greater than 1.0 μm and a surface layer B that contains particles. A release layer is stacked on surface layer A, and a hydrophobic layer is stacked on surface layer B.

8. The release film for resin sheet molding according to claim 1, wherein, Resin sheets are sheets containing inorganic compounds.

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

10. The release film for molding resin sheets according to any one of claims 1 to 9, wherein, The thickness of the resin sheet is greater than 0.2 μm and less than 1.0 μm.

11. A method for manufacturing ceramic green sheets, comprising a method for molding ceramic green sheets using the release film for resin sheet molding as described in claim 9, wherein, The formed ceramic green sheet has a thickness of 0.2μm to 1.0μm.

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