TWI861781B - Release film for resin sheet molding - Google Patents

Abstract

The object is to provide a release film, by which an ultra-thin layer of resin sheets, especially ultra-thin layer of ceramic green sheets, can be formed without defects by manufacturing a release film having a release layer that is extremely excellent in smoothness and releasability. A release film for resin sheet molding comprises a polyester film as a substrate and a release layer, wherein the polyester film has a surface layer A substantially free of inorganic particles, and the release layer is provided on the surface layer A, wherein the release layer is a layer obtained by curing a release layer forming composition, wherein the release layer forming composition contains at least cation-curing polydimethylsiloxane (a), wherein the regional surface roughness (Sa) of the release layer is less than 2 nm, and the number of protrusions with a height of more than 10 nm existing on the surface of the release layer is ^less than 200/mm2.

Description

Release film for resin sheet molding

The present invention relates to a release film for forming a resin sheet, and more specifically to a release film used when forming an ultra-thin resin sheet.

Conventionally, a release film having a polyester film as a substrate and a release layer laminated on the substrate has been used as an adhesive sheet or as a step film for molding resin sheets such as coatings, polymer films, and optical lenses.

The aforementioned release film is also used as a step film for molding ceramic green bodies that require high smoothness, such as multilayer ceramic capacitors and ceramic substrates. In recent years, along with the miniaturization and high capacity of multilayer ceramic capacitors, the thickness of ceramic green bodies has also tended to be thinner. The ceramic green body is molded by applying a slurry containing ceramic components such as barium titanium oxide and a binder resin on a release film and drying it. The ceramic green body obtained by printing electrodes on the molded ceramic green body and peeling it from the release film is manufactured into a multilayer ceramic capacitor through lamination, pressurization, firing, and external electrode coating.

When ceramic green sheets are formed on the surface of a release layer on a polyester film substrate, the tiny protrusions on the surface of the release layer will affect the formed ceramic green sheets, and it is easy to produce defects such as cissing or pinholes. This is the problem. In recent years, there has been a move towards further thinning of ceramic green sheets, and ceramic green sheets with a thickness of less than 1.0μm, more specifically, 0.2μm to 1.0μm, have been gradually required. For this reason, the requirements for the smoothness of the release layer surface have been further increased. In addition, the extremely tiny protrusions and foreign matter on the release layer involve the deformation of the formed ceramic green sheets, and there is a problem that it becomes easy to produce pinholes and fragments during peeling.

In addition, once the ceramic green body is made thinner, the peeling property when peeling the ceramic green body from the release film becomes more important. If the peeling force is large and uneven, the ceramic green body will be damaged during the peeling step, and sheet defects, uneven thickness, pinholes, broken pieces and other undesirable conditions will occur, which is the problem. Therefore, it is required to peel the ceramic green body with a lower and more uniform force. That is, in order to produce ultra-thin resin sheets without defects, especially to produce ceramic green bodies without defects, a release film with extremely high smoothness and excellent peeling property becomes necessary.

As release films with excellent smoothness and peeling properties, the following patent documents can be cited. For example, Patent Document 1 proposes a release film having a release layer using a radical-curing resin as a main component. Patent Document 2 proposes a release film having a smoothing layer and a release layer laminated thereon. Patent Document 3 proposes a release film having a release layer using a cation-curing epoxy resin as a main component. Patent Document 4 proposes a release film having a release layer using a cation-curing polydimethylsiloxane as a main component. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent No. 5492352. [Patent Document 2] Japanese Patent Publication No. 2015-164762. [Patent Document 3] International Publication No. 2018/079337. [Patent Document 4] Japanese Patent Publication No. 2016-079349.

[The problem that the invention wants to solve]

However, the release film of Patent Document 1 has the problem of insufficient smoothness of the release layer because the release layer is provided on a substrate film with insufficient smoothness. Furthermore, the inventors of the present invention have found through diligent research that free radical curing resins are poorly cured due to oxygen hindrance, so the surface of the release layer has poor solvent resistance, and the release layer is corroded by organic solvents used when forming the ceramic green body or printing the internal electrode, resulting in a problem of poor releasability. The invention of Patent Document 2 uses a thermosetting melamine resin in the smoothing coating layer and the release coating layer, and high heat is required to promote the curing reaction. Therefore, there is a risk that the flatness of the release film will be damaged by the heat during processing. In addition, since multiple processes are required to smooth the coating layer and the release coating layer, there is not only a risk of foreign matter being mixed into the release film, but also a risk of scratches on the release layer. There is a concern that the ceramic green body formed on the release layer will be transferred with foreign matter or scratches and cause adverse conditions.

In order to improve the poor curing caused by oxygen barrier and the poor planarity caused by processing heat, Patent Documents 3 and 4 respectively proposed a release layer using a cation-curing resin. However, the release film of Patent Document 3 has a problem of poor smoothness of the release layer surface due to the lack of smoothness of the substrate film. In addition, the release agent component disclosed in Patent Document 3 lacks reactivity, has poor solvent resistance and has problems with peeling. Since the release film of Patent Document 4 has a release layer using a liquid cation-curing polydimethylsiloxane resin as the main component, the resin will condense on the unevenness of the substrate film and the protrusions such as oligomers existing on the surface of the substrate film, which may cause problems with planarity. In addition, the cross-linking density of the release layer is low, and there are also problems with the release properties.

The present invention is based on the subject of related known technology. That is, the purpose is to provide a release film having a release layer that is particularly excellent in smoothness and releasability, and further, to provide a release film that can form an ultra-thin layer of resin sheet, especially an ultra-thin layer of ceramic green body without defects. [Means for solving the subject]

As a result of diligent research to solve the above problems, the inventors of the present invention have found that a release film having the following structure can achieve the above-mentioned purpose, thereby completing the present invention.

That is, the present invention has the following constitution. [1] A release film for forming a resin sheet, comprising a polyester film as a substrate and a release layer; the polyester film has a surface layer A substantially free of inorganic particles; the release layer is provided on the surface layer A; the release layer is a layer obtained by curing a release layer forming composition; the release layer forming composition contains cationic curing polydimethylsiloxane (a); the regional surface roughness (Sa) of the release layer is less than 2 nm; the number of protrusions with a height of 10 nm or more existing on the surface of the release layer is less than 200/ ^mm2 . [2] In one embodiment, the maximum protrusion height (Sp) of the release layer is less than 20 nm, and the total number of protrusions with a height of 5 nm or more but less than 10 nm on the surface of the release layer and the number of protrusions with a height of 10 nm or more is less than 1500/ ^mm2 . [3] In one embodiment, the cationic curing polydimethylsiloxane (a) has at least one functional group selected from vinyl ether group, cyclobutyl group, epoxy group, and alicyclic epoxy group. [4] In one embodiment, the content of the cationic curing polydimethylsiloxane (a) contained in the release layer is less than 90 mg/ ^m2 . [5] In one embodiment, the ion-curing layer forming composition further contains a cationic curing compound (b-1) having no polysiloxane skeleton; the cationic curing compound (b-1) has two or more alicyclic epoxy groups in the molecule, and the content of the cationic curing compound (b-1) is 80 mass % or more relative to 100 mass parts of the total of the cationic curing polydimethylsiloxane (a) and the cationic curing compound (b-1). [6] In one embodiment, the release layer forming composition further contains a cyclosiloxane compound (b-2) having an alicyclic epoxy group; the cyclosiloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule, and the content of the cyclosiloxane compound (b-2) is 80% by mass or more relative to 100 parts by mass of the total of the cation-curing polydimethylsiloxane (a) and the cyclosiloxane compound (b-2). [7] In one embodiment, a release layer forming composition contains an organic solvent having an SP value (δ) of 14 to 17, and the release layer forming composition contains the aforementioned organic solvent having an SP value (δ) of 14 to 17 in an amount of 10% by mass or more relative to 100 parts by mass of the total weight of the release layer forming composition. [8] In one embodiment, a release film is provided for manufacturing a resin sheet containing an inorganic compound. [9] In one embodiment, the resin sheet containing an inorganic compound is a ceramic green body. [10] In one embodiment, a release film is provided for molding a resin sheet having a thickness of 0.2 μm to 1.0 μm. [Effect of the Invention]

The release film for resin sheet molding of the present invention can improve the smoothness and releasability of the release layer, thereby inhibiting the occurrence of defects in ultra-thin resin sheets, especially ceramic green bodies.

The present invention is described in detail below. The present invention is a release film for resin sheet molding, comprising a polyester film as a substrate and a release layer; the polyester film has a surface layer A substantially free of inorganic particles; the surface layer A has a release layer; the release layer is a layer formed by curing a release layer forming composition; the release layer forming composition contains cationic curing polydimethylsiloxane (a); the regional surface roughness (Sa) of the release layer is less than 2 nm; the number of protrusions with a height of more than 10 nm existing on the surface of the release layer is less than 200 pieces/ ^mm2 .

The present invention having such a structure can provide uniform thickness without defects for resin sheets with a thickness of, for example, 0.2 μm to 1.0 μm or less, and can suppress defects such as pinholes, because the release layer has excellent smoothness and releasability. In addition, the present invention can exert the following effects. Since the release layer is provided for a substrate film with sufficient smoothness, the smoothness of the release layer can also be ensured. Furthermore, the present invention can suppress poor curing caused by oxygen barrier in the release layer and can exert high crosslinking of the release layer. The present invention that can exert such an effect can, for example, improve the solvent resistance of the surface of the release layer. By improving the solvent resistance of the release layer surface, the release layer can be prevented from being corroded by the organic solvent used when the ceramic green body is formed and the internal electrode is printed, and has high releasability. In addition, in the case of the present invention, compared with the release layer with thermosetting melamine resin, for example, high heat is not required to promote the curing reaction. Therefore, the heat during processing can be prevented from damaging the flatness of the release film. In addition, in the manufacturing method of the present invention, by going through the coating step and drying step of the present invention, the aggregation of the release layer formation composition can be suppressed, and a release film having a release layer with extremely high smoothness can be obtained.

More specifically, a release layer having extremely high smoothness can be obtained by coating a release layer-forming composition containing a predetermined amount of cationic-curing polydimethylsiloxane (a) on a surface layer A of a substrate film that does not substantially contain inorganic particles and curing the composition. Furthermore, by controlling the content of the cationic-curing polydimethylsiloxane (a) in the release layer to be below a predetermined amount, during the processing of the release layer, the cationic-curing polydimethylsiloxane (a) can be suppressed from aggregating on extremely fine foreign matter and microscopic protrusions derived from oligomers existing in the substrate film. Although the explanation should not be limited to a specific theory, by increasing the first drying temperature (enhanced drying), component (a) can be prevented from agglomerating on fine protrusions caused by the original roll. In addition, by inhibiting poor hardening due to oxygen barrier, improving the solvent resistance of the release layer surface, inhibiting the mixing of foreign matter into the release layer, and inhibiting the scratches of the release layer, it is possible to prevent damage, scratches, foreign matter, etc. during peeling of the release body such as the ceramic green body, and deformation of the sheet due to transfer. As a result, a release layer with excellent smoothness and hardness, peeling properties, and anti-contamination properties of the release layer can be obtained. In addition, during the drying of the organic solvent contained in the release layer forming composition, the cationic curing polydimethylsiloxane (a) becomes less likely to aggregate, and a release layer with excellent smoothness can be formed. Details are described below.

In addition, the present invention provides a method for manufacturing a release film for resin sheet molding in other aspects, which comprises the following steps. The coating step is to coat the release layer forming composition on the aforementioned surface layer A of the polyester film having the surface layer A, the surface layer A is a layer substantially free of inorganic particles, and the release layer forming composition contains cationic curing polydimethylsiloxane (a); the drying step is to heat and dry the polyester film coated with the release layer forming composition, the aforementioned heat drying has a first drying step and a subsequent second drying step, the drying temperature T1 in the aforementioned first drying step is higher than the drying temperature T2 in the aforementioned second drying step; and the light curing step is to irradiate active energy rays after the aforementioned drying step to cure the release layer forming composition.

In the manufacturing method related to the present invention, a highly smooth release layer can be formed by setting the manufacturing conditions when processing the release layer to a predetermined method. For example, the coating amount of the release layer forming composition, the composition of the organic solvent, the drying time, the drying temperature, etc. can be controlled. By manufacturing the release film under the conditions of the present invention, the aggregation of the cationic curing polydimethylsiloxane (a) contained in the release layer forming composition can be suppressed, and a release layer with excellent smoothness can be obtained. The details are described below.

(Polyester film) The polyester used as the base material of the polyester film of the present invention is not particularly limited, and a polyester generally used as a base material for release films can be used. Preferably, it is a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component, such as polyethylene terephthalate, polyethylene naphthalate-2,6-ethylene dicarboxylate, polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer having the components of these resins as the main components. In particular, a polyester film formed of polyethylene terephthalate is particularly suitable. In polyethylene terephthalate, the repeating unit of ethylene terephthalate is preferably 90 mol% or more, more preferably 95 mol% or more. Other dicarboxylic acid components and glycol components may also be copolymerized in small amounts, but for cost considerations, it is preferred to be made only of terephthalic acid and ethylene glycol. In addition, within the scope that does not hinder the film effect of the present invention, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, crystallization agents, etc. may also be added. Based on the reasons such as the high and low elastic modulus of the polyester film in both directions, a biaxially oriented polyester film is preferred.

The inherent viscosity of the above polyester film is preferably 0.50 dl/g to 0.70 dl/g, and more preferably 0.52 dl/g to 0.62 dl/g. When the inherent viscosity is 0.50 dl/g or more, it is better because a large amount of breakage will not occur in the stretching step. On the contrary, when it is 0.70 dl/g or less, the cutting property is good when cutting into the predetermined product width, and the size defect will not occur, so it is better. In addition, it is better that the raw material particles are fully vacuum dried. In addition, when it is recorded as "polyester film" in this manual, it means a polyester film having (laminated with) a surface layer A. In addition, in the present invention, the polyester film has a surface layer A substantially free of inorganic particles, and has the aforementioned release layer on the surface layer A. In addition, if mentioned in the specification, the polyester film further having (laminated with) a surface layer B is sometimes referred to as a "polyester film".

The method for producing the polyester film in the present invention is not particularly limited, and the methods generally used in the past can be used. For example, the polyester is melted by an extruder, extruded into a film, cooled on a rotary cooling drum to obtain an unstretched film, and the unstretched film is stretched to obtain the film. If the stretching is biaxial stretching, it is better in terms of mechanical properties and the like. The biaxially stretched film can be obtained by a method of gradually biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction in the transverse direction or in the longitudinal direction, or by a method of synchronously biaxially stretching an unstretched film in the longitudinal and transverse directions.

In the present invention, the stretching temperature of the polyester film during stretching is preferably set to be above the secondary transition point (Tg) of the polyester. The stretching in the longitudinal and transverse directions is preferably performed by 1 to 8 times, especially 2 to 6 times.

The thickness of the polyester film is preferably 12 μm to 50 μm, more preferably 15 μm to 38 μm, and even more preferably 19 μm to 33 μm. As long as the thickness of the film is 12 μm or more, there is no risk of thermal deformation during film production or during the processing of the release layer or the molding of the ceramic green body, so it is preferred. On the other hand, as long as the thickness of the film is 50 μm or less, the amount of film discarded after use will not increase significantly, which is preferred in terms of reducing the environmental load.

The polyester film may be a single layer or a multi-layer structure of two or more layers. The polyester film has a surface layer A that does not substantially contain inorganic particles. For example, it may be a single layer of surface layer A, or it may be a multi-layer structure having surface layer A and other layers (such as surface layer B described below). In the case of a laminated polyester film composed of a multi-layer structure of two or more layers, it is preferred to have a surface layer B that may contain particles on the opposite side of the surface layer A that does not substantially contain inorganic particles. In terms of the layer structure, if the layer on the side where the release layer is applied is regarded as the surface layer A, the layer on the opposite side is regarded as the surface layer B, and the core layer other than the surface layer A and the surface layer B is regarded as the layer C, then the layer structure in the thickness direction can be a layer structure such as release layer/A/B, or release layer/A/C/B. Of course, layer C can also be a multiple layer structure. In addition, the surface layer B may not contain particles. In this case, in order to give the film slippery properties when it is rolled into a roll, it is better to set a coating containing particles and a binder on the surface layer B.

The polyester film of the present invention has a surface layer A located on the surface where the release layer is applied, which does not substantially contain inorganic particles. In the present invention, since the surface layer A does not substantially contain inorganic particles, it can show the following regional surface average roughness. In the present invention, the regional surface average roughness (Sa) of the surface layer A is the regional surface average roughness (Sa) of the surface where the release layer is arranged, and the regional surface average roughness (Sa) of the surface where the release layer is arranged is 7nm or less. If Sa is 7nm or less, even the release layer layered on the surface layer A can show high smoothness, and pinholes are not easily generated during the molding of the ultra-thin layer ceramic green body layered on the release layer. Furthermore, when the release layer is formed, the protrusions on the surface layer A where the release layer components condense can be suppressed, thereby preventing the smoothness of the release layer surface from deteriorating.

The smaller the average surface roughness (Sa) of the surface layer A, the better, and it can be above 0.1nm. In one embodiment, the average surface roughness (Sa) of the surface layer A is between 0.1nm and 7nm, for example, between 0.5nm and 5nm, or between 0.5nm and 4nm. By setting it within this range, the smoothness of the release layer can be improved, and the generation of pinholes during the molding of the ultra-thin layer ceramic green body can be suppressed. Furthermore, when the release layer is formed, the protrusions of the release layer components condensed on the surface layer A can be suppressed, and the deterioration of the smoothness of the release layer surface can be prevented.

In the present invention, "substantially free of inorganic particles" means that the content of inorganic elements quantified by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if inorganic particles are not actively added to the membrane, there are still contaminants from external foreign matter, and contaminants attached to the production line or equipment during the raw material resin or membrane manufacturing steps that may be mixed into the membrane.

The polyester film substrate of the present invention may also have a surface layer B on the opposite side of the surface on which the release layer is arranged. The surface layer B preferably contains particles. By containing particles, the film has excellent slip and air removal properties, and can have excellent transportability and rollability. In particular, it is preferably containing silica particles and/or calcium carbonate particles. The total amount of particles contained in the surface layer B is 1000 ppm to 15000 ppm. At this time, the average surface roughness (Sa) of the region of the film of the surface layer B is, for example, greater than 1 nm and less than 40 nm. More preferably, it is greater than 5 nm and less than 35 nm. When the total amount of silicon dioxide particles and/or calcium carbonate particles is above 1000ppm and Sa is above 1nm, when the film is rolled into a roll, air can be evenly dispersed, and the roll-up state and planarity can be good. With this feature, for example, when manufacturing ultra-thin layer resin sheets (such as ceramic green sheets) with a thickness of 0.2μm to 1.0μm, wrinkles and deviations of the rolled ceramic green sheets can be prevented, and a release film with excellent transportability, roll-up and storage properties can be provided. In addition, when the total amount of silicon dioxide particles and/or calcium carbonate particles is less than 15000ppm and Sa is less than 40nm, the particles that function as lubricants are less likely to condense and will not produce coarse protrusions (e.g., protrusions with a height of more than 1μm). Therefore, when manufacturing ultra-thin resin sheets (e.g., ceramic green sheets), the occurrence of pinholes caused by winding can be suppressed, and resin sheets with stable quality can be provided.

In addition to silicon dioxide and/or calcium carbonate, the particles contained in the surface layer B may also be inactive inorganic particles and/or heat-resistant organic particles. From the perspective of transparency and cost, it is better to use silicon dioxide particles and/or calcium carbonate particles. Other inorganic particles that can be used include aluminum oxide-silicon dioxide composite oxide particles, hydroxyapatite particles, etc. In addition, as heat-resistant organic particles, cross-linked polyacrylic acid particles, cross-linked polystyrene particles, benzoguanamine particles, etc. can be cited. When silicon dioxide particles are used, porous colloidal silicon dioxide is preferred. When calcium carbonate particles are used, from the perspective of preventing particles from falling off, light calcium carbonate surface-treated with a polyacrylic acid polymer compound is preferred.

The average particle size of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. When the average particle size is 0.1 μm or more, the slipperiness of the release film is good, which is preferred. In addition, when the average particle size is 2.0 μm or less, the deformation of the surface layer A can be suppressed, and the uneven thickness of the ceramic green body and the occurrence of pinholes can be suppressed.

The surface layer B may contain particles of two or more different materials. In addition, it may contain particles of the same kind but with different average particle sizes. In addition, the two or more different particles may have different average particle sizes within the above range. By containing two different types of particles, the unevenness formed on the surface layer B can be highly suppressed, and both sliding properties and smoothness can be taken into account, which is better.

From the viewpoint of reducing pinholes, it is preferred that the layer on the side where the release layer is provided, namely the surface layer A, not use recycled materials in order to prevent the incorporation of particles or impurities.

The thickness ratio of the layer on the side where the release layer is provided, i.e., the surface layer A, is preferably 20% or more and 50% or less of the total layer thickness of the substrate film. As long as it is 20% or more, it is not easy to be affected by particles contained in the surface layer B from the inside of the film, and the average surface roughness Sa of the region can meet the above range, so it is better. If it is less than 50% of the total layer thickness of the substrate film, the ratio of recycled raw materials used in the co-extruded surface layer B and the above-mentioned intermediate layer C can be increased, and the environmental load becomes smaller, so it is better.

In addition, from the perspective of economy, the layers other than the surface layer A (surface layer B or the aforementioned intermediate layer C) may use 50% to 90% by mass of film scraps or recycled materials from PET bottles. This is the case, and the type and amount of the lubricant contained in the surface layer B, the particle size, and the average surface roughness (Sa) of the area preferably meet the above ranges.

In addition, based on the consideration of improving the adhesion of the release layer to be coated later or anti-static, a coating may be provided on the surface of the surface layer A and/or the surface layer B before stretching in the film forming step or after uniaxial stretching, or a corona treatment may be applied. When a coating is provided on the surface layer A, it is preferred that the coating does not substantially contain particles.

(Release layer) In the present invention, the release layer is laminated on the surface layer A. In the present invention, the release layer is a layer formed by hardening the release layer forming composition, the release layer and the release layer forming composition contain at least cation-curing polydimethylsiloxane (a), the regional surface roughness (Sa) of the release layer is 2 nm or less, and the number of protrusions with a height of 10 nm or more existing on the surface of the release layer is 200 or less/ ^mm2 . Due to such characteristics, the release layer can suppress the generation of pinholes in ultra-thin film resin sheets (such as ceramic green sheets) requiring high smoothness, and can form a resin sheet with uniform film thickness. In more detail, the release layer of the present invention can suppress poor hardening due to oxygen barrier and can show high crosslinking of the release layer. The present invention that exerts such an effect can, for example, improve the solvent resistance of the release layer surface. By improving the solvent resistance of the release layer surface, the release layer can be inhibited from being eroded by the organic solvent used when forming the ceramic green body and printing the internal electrode, and can have high releasability. In addition, according to the present invention, it is not necessary to use high heat of more than 130°C to promote the hardening reaction. Therefore, it is possible to suppress the damage to the planarity of the release film caused by the heat during processing. In addition, it can inhibit the mixing of foreign matter into the release film for resin sheet molding, inhibit the occurrence of scratches on the release layer, and inhibit the occurrence of sheet damage caused by the transfer of foreign matter and scratches to the release body such as ceramic green body.

The regional surface average roughness (Sa) of the release layer is less than 2 nm. In addition, the number of protrusions with a height of more than 10 nm on the surface of the release layer is ^less than 200/mm2. In order to avoid defects in the ceramic sheet coated and formed on the release layer, the surface of the release layer of the release film satisfies the predetermined conditions for the regional surface average roughness (Sa) and the number of protrusions with a height of more than 10 nm. As long as the regional surface roughness (Sa) is less than 2 nm and the number of protrusions with a height of more than 10 nm is less than 200/ ^mm2 , pinholes and other defects will not be generated on the ceramic sheet when the ceramic sheet is formed, and the yield is good, so it is better. More preferably, the regional surface roughness (Sa) is less than 1.7 nm, for example, it can also be less than 1.6 nm or less than 1.5 nm. In one embodiment, the regional surface roughness (Sa) is less than 1.3 nm. In addition, the regional surface roughness (Sa) may be greater than 0.1 nm, and may be greater than 0.2 nm. On the other hand, in one embodiment, the number of protrusions with a height of greater than 10 nm is less than 180/ ^mm2 , for example, ^less than 170/mm2, or less than 160/ ^mm2 . In one embodiment, the number of protrusions with a height of greater than 10 nm may be less than 120/ ^mm2 , or less than 100/ ^mm2 . In addition, the number of protrusions with a height of greater than 10 nm may be greater than 1/ ^mm2 , or, for example, greater than 10/ ^mm2 . By making the number of protrusions with a height of greater than 10 nm within the above range, defects such as pinholes will not be generated in the ceramic sheet, and excellent releasability can be achieved in a balanced manner. It is more preferable that the regional surface roughness (Sa) is less than 1.0 nm, and the number of protrusions with a height of greater than 10 nm is less than 100/ ^mm2 . The release layer having the regional surface average roughness (Sa) and the number of protrusions related to the present invention can exhibit extremely excellent smoothness.

In one embodiment, the maximum protrusion height (Sp) of the release layer is less than 20 nm. If the maximum protrusion height is within this range, defects of the ceramic sheet can be further suppressed. More preferably, the maximum protrusion height (Sp) is less than 15 nm, and more preferably less than 10 nm. In one embodiment, the total number of protrusions with a height of more than 5 nm but less than 10 nm on the surface of the release layer and the number of protrusions above 10 nm is less than 1500 pieces/ ^mm2 . If the total number of protrusions with a height of more than 5 nm but less than 10 nm on the release layer and the number of protrusions above 10 nm is less than 1500 pieces/ ^mm2 , defects of the ceramic sheet can be further suppressed, and a release layer with high smoothness can be obtained, which is better. More preferably, the total number of protrusions with a height of 5 nm or more and less than 10 nm and the number of protrusions with a height of 10 nm or more is 1000/mm ² or less, for example, 500/mm ² or less is more preferably.

The release layer associated with the release film for resin sheet molding of the present invention is a layer formed by hardening the release layer forming composition, and the release layer forming composition contains at least cationic hardening polydimethylsiloxane (a). Cationic hardening polydimethylsiloxane (a) undergoes crosslinking reaction due to cationic hardening reaction, so there will be no poor hardening caused by oxygen barrier, and it becomes a release layer with excellent solvent resistance. Therefore, there is no need to worry about the release layer being corroded by the organic solvent used in the molding of ceramic green body and the printing of internal electrodes, and a release layer with excellent peeling property can be obtained.

Furthermore, the inventors have found that in a release layer containing cationic curing polydimethylsiloxane (a), a high amount of cationic curing polydimethylsiloxane (a) is important for achieving a smooth release layer. The cationic curing polydimethylsiloxane (a) is contained in the release layer in an amount of 90 mg/m ² or less, for example, 60 mg/m ^{2 or less, preferably 50 mg/m 2 or} less, more preferably 40 mg/m ² or less, and even more preferably 30 mg/m ² or less. In addition, the cationic curing polydimethylsiloxane (a) may be contained in an amount of 20 mg/m ² or less, for example. If the content of the cationic curing polydimethylsiloxane (a) in the release layer is 50 mg/m2 or ^less , the aggregation of the polydimethylsiloxane (a) in the step of forming the release layer (e.g., the drying step) can be suppressed, and there is no need to worry about the generation of protrusions outside the scope of the present invention, and the effect of the present invention can be exerted. In one aspect, the release layer and the release layer forming composition may contain ingredients other than the cationic curing polydimethylsiloxane (a). Even in this case, although it should not be judged based on a specific theory, in the present invention, when the release layer is processed, the polydimethylsiloxane (a) may be segregated on the surface of the release layer. If the content is 50 mg/ ^m2 or less, it is not easy to aggregate, and a release layer with high smoothness can be formed. The lower the content of the polydimethylsiloxane (a) related to the present invention, the less likely it is to aggregate. As long as it is 0.1 mg/ ^m2 or more in the release layer, the uniformity of the release layer can be maintained, and a release layer with excellent coating appearance and high smoothness can be obtained. In addition, as long as it is 0.1 mg/ ^m2 or more, it is better because the peeling property is also excellent. For example, the content of polydimethylsiloxane (a) can also be 0.5 mg/ ^m2 or more. In the present invention, the release layer forming composition contains cationic curing polydimethylsiloxane (a). In addition, in the release layer formed by curing the release layer forming composition, a compound derived from the cationic curing polydimethylsiloxane (a) (cured product) exists. In this specification, the compound derived from the polydimethylsiloxane (a) existing in the release layer is sometimes referred to as cationic curing polydimethylsiloxane (a).

The cationic curing polydimethylsiloxane (a) in the present invention refers to a polydimethylsiloxane having a cationic curing functional group. The cationic curing functional group may be a reactive functional group showing cationic curability, specifically, a vinyl ether group, an oxycyclobutyl group, an epoxy group, and an alicyclic epoxy group. From the viewpoint of reactivity, it is preferred to have at least one functional group selected from an oxycyclobutyl group, an epoxy group, and an alicyclic epoxy group, and the alicyclic epoxy group is the best. By having such functional groups, a cross-linked structure can be formed through a cationic curing reaction, thus becoming a release layer with excellent solvent resistance and excellent peeling properties.

The number of cationic curable functional groups possessed by the cationic curable polydimethylsiloxane (a) only needs to be one or more. For example, by having two or more cationic curable functional groups, the cationic curing reaction becomes easier to proceed, and it is better to form an ion-bonded layer with a high crosslinking density. The position of introduction of the cationic curable functional group is not particularly limited, and it can generally be located at the side chain or end of the polydimethylsiloxane. The structure of the polydimethylsiloxane can be a linear structure or a branched structure, and even if it has a functional group other than a cationic curable functional group, it can be used without problem.

As the cationic curing polydimethylsiloxane (a), commercially available ones can be suitably used. Examples include Silicone Conis (registered trademark) UV POLY200, UV POLY201, UV POLY215, UV RCA200, and UV RCA251 manufactured by Arakawa Chemical Industries, 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 Momentive Performance Materials, and UV9440E and UV9430 manufactured by Shin-Etsu Chemical Industries, Ltd.

The weight average molecular weight of the cationic curing polydimethylsiloxane (a) is preferably 1,000 to 500,000, more preferably 5,000 to 100,000. If the weight average molecular weight is 1,000 or more, the cationic curing reaction is easy to proceed and the peeling property is excellent. If it is 500,000 or less, the viscosity will not become too high, and a release layer with excellent coating property and high planarity will be formed.

The release layer forming composition of the present invention may contain other resins in addition to the cationic curing polydimethylsiloxane (a). In this case, the film thickness of the release layer can be reduced. In the present invention, since the release layer is provided on the surface layer A of the substrate film which does not substantially contain inorganic particles, even if the film thickness of the release layer is thin, the release layer can be made to have extremely high smoothness. In addition, since the film thickness of the release layer is thin, the curing reaction is easy to proceed, and the processing can be performed at a higher speed, and the release layer can be obtained economically.

If the film thickness is further reduced, there is no need to worry about the extremely small foreign matter that exists in the release processing step being carried into the release layer. Therefore, there is no risk of protrusions from foreign matter on the surface of the release layer, and a release layer with a smooth surface as mentioned above can be obtained.

In the case of a release layer formed by curing a composition with cationic curing polydimethylsiloxane (a) as the main component, the film thickness of the release layer is preferably 0.001μm or more and less than 0.050μm. If it is 0.001μm or more, it is better because of the excellent release property. If it is less than 0.050μm, it can prevent the aggregation of the composition formed by the release layer, and form a smooth release layer, so it is better. In addition, in the present invention, when cationic curing polydimethylsiloxane (a) is used as the main component, the composition contains 50 parts by mass or more of cationic curing polydimethylsiloxane (a) relative to 100 parts by mass of the resin solids of the release layer, for example, more than 50 parts by mass, preferably more than 70 parts by mass, for example, more than 80 parts by mass, and in one embodiment, more than 90 parts by mass. In addition, it can also be an embodiment in which the resin solids of the release layer substantially entirely contain cationic curing polydimethylsiloxane (a).

The release layer forming composition of the present invention may contain a cationic curing type polydimethylsiloxane (a) and a cationic curing type resin (b). In this case, (b) is a resin different from (a), and the resin (b) is a resin without a polydimethylsiloxane structure. Specifically, it can be roughly divided into two types: a cationic curing type compound (b-1) without a polysiloxane skeleton and a cyclic siloxane compound (b-2) with an alicyclic epoxy group.

In one embodiment, the ion-forming composition contains, in addition to the cationic curing polydimethylsiloxane (a), a cationic curing compound (b-1) without a polysiloxane skeleton. Examples of cationic curing compounds (b-1) without a polysiloxane skeleton include polymers and monomers having two or more cationic curing functional groups in the molecule and without a polysiloxane skeleton. Among them, resins having two or more epoxy groups or alicyclic epoxy groups are preferred, and resins having two or more alicyclic epoxy groups are more preferred. For example, the number of alicyclic epoxy groups may be six or less. By having two or more alicyclic epoxy groups, a crosslinking reaction can be carried out through a cationic curing reaction to form a release layer with excellent solvent resistance. In addition, a crosslinking reaction is also carried out with the polydimethylsiloxane (a) contained in the release layer at the same time, so the peeling property is excellent, and the migration of the polydimethylsiloxane (a) to the ceramic green body is suppressed, which is better.

In one embodiment, the release layer forming composition contains both a cationic curable resin (b-1) without a polysiloxane skeleton and polydimethylsiloxane (a), so a release layer with high smoothness can be realized. By preparing a release layer containing compound (b-1), fine unevenness or extremely fine foreign matter, protrusions derived from oligomers, etc. existing in the base film can be buried to form an ultra-smooth release layer. In addition, since the curing reaction is carried out by ultraviolet light, a release layer with high smoothness is formed. Although the explanation should not be limited to a specific theory, it can be inferred that during the drying step of the release layer forming composition during the release layer processing, the cationic curable resin (b-1) without a polysiloxane skeleton and the polydimethylsiloxane (a) are uniformly made flat, and after the flatness is improved, hardening is performed to obtain a release layer with high smoothness. In addition, in the present invention, the polydimethylsiloxane (a) contained at the same time is segregated on the surface of the release layer during the drying step, so that a release layer with excellent releasability can be obtained.

The cationic curing compound (b-1) without a polysiloxane skeleton is preferably a low molecular weight monomer. Specifically, the number average molecular weight is preferably 200 to less than 5000, more preferably 200 to less than 2500, and more preferably 200 to less than 1000. If the number average molecular weight is 200 or more, the boiling point will not be lowered, and the cationic curing compound (b-1) will not be volatilized in the drying step of the release layer forming composition during the release layer processing, so it is preferred. If it is less than 5000, the crosslinking density of the release layer is high and the solvent resistance is excellent, so it is preferred. In addition, since it can exist in a fluid liquid state during the drying step, it has excellent leveling properties and forms an ultra-smooth release layer, which is better.

As the cation-curable compound (b-1) without a polysiloxane skeleton, commercially available ones can be suitably used. Examples of compounds having an alicyclic epoxy group include Celloxide 2021P, Celloxide 2081, Epolead GT401, EHPE3150 manufactured by Daicel, HiREM-1 manufactured by Shikoku Chemicals, THI-DE, DE-102, DE-103 manufactured by ENEOS, and the like. Examples of resins having an epoxy group include EPICLON (registered trademark) 830, 840, 850, 1051-75M, N-665, N-670, N-690, N-673-80M, N-690-75M manufactured by DIC Corporation and Denacol (registered trademark) EX-611, EX-313, EX-321 manufactured by Nagase Chemtex Corporation.

The content of the cationic curing compound (b-1) without a polysiloxane skeleton 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 100 parts by mass of the total of the cationic curing polydimethylsiloxane (a) and the cationic curing compound (b-1) in the release layer. If the content of the cationic curing compound (b-1) is set to 80% by mass or more and becomes the main component in the release layer, it is better to form a release layer with high crosslinking density and excellent releasability. In addition, the content of cationic curing polydimethylsiloxane (a) in the release layer can be reduced, and the components derived from polydimethylsiloxane (a) can be inhibited from condensing on the surface of the release layer during the drying step, which is more preferable because there is no risk of deterioration of planarity. Although the higher the content of cationic curing compound (b-1), the smoother the release layer can be, in order to ensure the release property by containing cationic curing polydimethylsiloxane (a), the cationic curing compound (b-1) is preferably 99.9% by mass or less. In the present invention, a compound (cured product) derived from a cation-curing compound (b-1) without a polysiloxane skeleton exists in the release layer of the release layer-forming composition after curing. In this specification, the compound derived from (b-1) existing in the release layer is sometimes simply referred to as a cation-curing compound (b-1) without a polysiloxane skeleton.

When the release layer forming composition contains cationic curing polydimethylsiloxane (a) and cationic curing compound (b-1), the release layer has a high crosslinking density and excellent solvent resistance, and thus becomes a release layer with excellent peeling force, which is preferred. In addition, if the cationic curing compound (b-1) is contained, it is preferred because the content of the cationic curing polydimethylsiloxane (a) can be controlled within a predetermined range while the film thickness of the release layer is increased. By increasing the film thickness of the release layer, scratches and extremely small unevenness existing in the base film can be buried, and a smooth release layer can be obtained as described above, which is preferred.

When the release layer forming composition contains cationic curing polydimethylsiloxane (a) and cationic curing compound (b-1), the film thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. If it is 0.05 μm or more, it will become a smooth release layer, so it is better. If it is 1.0 μm or less, it will not cause warping and can obtain a release film with excellent planarity, so it is better.

In one embodiment, the release layer forming composition may further include a cyclosiloxane compound (b-2) having an alicyclic epoxy group. Examples of the cyclosiloxane compound (b-2) having an alicyclic epoxy group include the compound represented by the following structural formula (chemical formula 1) (in chemical formula 1, ^R2 is an alkyl group having 1 to 4 carbon atoms). In addition, the cation-curable compound (b-2) having a cyclosiloxane skeleton preferably has at least two alicyclic epoxy groups. If there are two or more alicyclic epoxy groups, a cation-curing reaction will occur to form a release layer with a high crosslinking density, which is preferred.

[Chemical formula 1]

By using a cyclic siloxane compound (b-2) having an alicyclic epoxy group, it is preferred that a super-smooth release layer be obtained for the same reason as when the aforementioned cationic curing compound (b-1) is used. That is, minute irregularities, extremely fine foreign bodies, protrusions derived from oligomers, etc. existing in the substrate film can be filled. In addition, since the curing reaction is carried out by ultraviolet light, the compound (b-2) and the polydimethylsiloxane (a) can be uniformly flattened in the drying step of the release layer forming composition during the release layer processing, and curing is performed after the planarity is improved, so that a super-smooth release layer can be obtained. Furthermore, in the present invention, since the polydimethylsiloxane (a) contained therein will segregate on the surface of the release layer during the drying step, a release layer having excellent releasability can be obtained.

The cyclic siloxane compound (b-2) having an alicyclic epoxy group has good mutual solubility with the cationic curing polydimethylsiloxane (a), so they are mixed appropriately in the release layer and undergo cross-linking reaction with each other. Therefore, it has excellent solvent resistance and is preferably a release layer showing excellent peeling properties. In addition, the cyclic siloxane compound (b-2) has a rigid molecular skeleton due to its cyclic siloxane structure, and is preferably high in film hardness when hardened. By increasing the film hardness, the release layer becomes less likely to deform when the resin sheet (such as ceramic green body) is peeled off, and can show good peeling properties. Furthermore, the release layer is less likely to be scratched, and there is no need to worry about the scratches on the release layer being transferred to the resin sheet (such as ceramic green body) and causing adverse conditions, which is better.

If the release layer forming composition contains the cyclic siloxane compound (b-2), the adhesion of the release layer to the substrate film can be improved. If the adhesion of the release layer is improved, scratches during the conveying step can be suppressed, and there is no need to worry about the transfer of the release layer when the resin sheet is peeled off.

In one embodiment, the cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule. If the molecule has two or more alicyclic epoxy groups, a crosslinking reaction can be performed by a cationic curing reaction to form a release layer with excellent solvent resistance. In addition, it also undergoes a crosslinking reaction with the polydimethylsiloxane (a) contained in the release layer, so the release property is excellent, and the migration of polydimethylsiloxane (a) to the ceramic green body can be suppressed, so it is better. For example, the cyclic siloxane compound (b-2) has six or less alicyclic epoxy groups in the molecule.

As the cyclosiloxane compound (b-2) having an alicyclic epoxy group, commercially available ones can be used, for example, X-40-2670 and X-40-2678 manufactured by Shin-Etsu Chemical Co., Ltd.

The content of the cyclic siloxane compound (b-2) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to 100 parts by mass of the total of the cationic curing polydimethylsiloxane (a) and the cyclic siloxane compound (b-2) in the release layer. If the content of the cyclic siloxane compound (b-2) is set to 80% by mass or more and becomes the main component in the release layer, it is preferred that the release layer has a high crosslinking density and excellent releasability. In addition, the content of cationic curing polydimethylsiloxane (a) contained in the release layer can be reduced. In the present invention, the cationic curing polydimethylsiloxane (a) can be inhibited from condensing on the surface of the release layer during the drying step, and there is no need to worry about the deterioration of planarity. The higher the content of the cyclic siloxane compound (b-2), the smoother the release layer becomes. For example, in order to contain the cationic curing polydimethylsiloxane (a) and ensure the releasability, the cyclic siloxane compound (b-2) is preferably 99.9% by mass or less. In the present invention, a compound derived from the cyclic siloxane compound (b-2) (cured product) exists in the release layer of the release layer forming composition after curing. In this specification, the compound derived from the cyclic siloxane compound (b-2) existing in the release layer is sometimes simply described as the cyclic siloxane compound (b-2).

When the release layer forming composition contains the cationic curing polydimethylsiloxane (a) and the cyclic siloxane compound (b-2), the film thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. If it is 0.05 μm or more, it is preferred because a smooth release layer is obtained. If it is 1.0 μm or less, it is preferred because warping can be avoided and a release film with excellent planarity can be obtained.

In one embodiment, the release layer may include both a cationic curing resin (b-1) and a cyclosiloxane compound (b-2), and the total amount of the cationic curing resin (b-1) and the cyclosiloxane compound (b-2) may be 80% by mass or more and 99.9% by mass or less relative to 100 parts by mass of the total amount of the cationic curing polydimethylsiloxane (a), the cationic curing compound (b-1) and the cyclosiloxane compound (b-2) in the release layer.

In the present invention, a cationic curing reaction must be performed to form a release layer. Therefore, it is preferred that the release layer forming composition contains an acid generator (c). In addition, a compound derived from the acid generator (c) may exist in the release layer. Here, the compound derived from the acid generator (c) present in the release layer is sometimes referred to as the acid generator (c). The acid generator is not particularly limited and a general acid generator can be used, but by using a photoacid generator that generates acid under ultraviolet irradiation, the heat during processing can be suppressed, and a release layer with excellent planarity can be obtained, which is preferred.

From the viewpoint of reactivity, the photoacid generator is preferably a salt formed by an onium ion and a non-nucleophilic anion. In addition, an organometallic complex represented by an iron aromatic complex, a carbon cation salt represented by a barium, or a phenol substituted with an anthracene derivative or an electron-withdrawing group, such as pentafluorophenol, can also be used.

When the salt formed by the above-mentioned onium ion and non-nucleophilic anion is used as the photoacid generator, the onium ion can be, for example, iodonium, cobalt, and ammonium. As the organic group of the onium ion, a triaryl, a diaryl (monoalkyl), a monoaryl (dialkyl), a trialkyl group can be used. Benzophenone, 9-fluorene, and other organic groups can also be introduced. As the non-nucleophilic anion, hexafluorophosphate, hexafluoroantimonate, hexafluoroborate, and tetrakis(pentafluorophenyl)borate are suitable. In addition, tetrakis(pentafluorophenyl)gallium ions, anions in which several fluorine anions are substituted for perfluoroalkyl or organic groups, and other anion components can also be used.

The amount of the photoacid generator added is 0.1 to 10 mass %, preferably 0.5 to 8 mass %, relative to 100 mass parts of the total of the cationic curing polydimethylsiloxane (a) and the cationic curing compound (b-1) and/or the cyclosiloxane compound (b-2) in the ion layer. More preferably, it is 1 to 5 mass %. If it is 0.1 mass % or more, there is no need to worry about insufficient acid being generated and insufficient hardening. In addition, if it is 10 mass % or less, the amount of acid generated becomes appropriate, and the amount of acid migration to the formed ceramic green body can be suppressed, which is preferred.

In this specification, the total of 100 parts by mass of the cationic curing polydimethylsiloxane (a) and the cationic curing compound (b-1) and/or the cyclic siloxane compound (b-2) in the release layer refers to the total solid content of the cationic curing polydimethylsiloxane (a) and the solid content of the cationic curing resin (b). In addition, in the case where the release layer does not contain the cationic curing resin (b), the weight of the cationic curing polydimethylsiloxane (a) is equivalent to 100 parts by mass of the resin solid content in the release layer.

In one embodiment, the release layer forming composition includes an organic solvent having an SP value (δ) of 14 to 17, and the release layer forming composition is such that the organic solvent having an SP value (δ) of 14 to 17 is contained in an amount of 10% by mass or more relative to 100 parts by mass of the total weight of the release layer forming composition. The organic solvent having an SP value (δ) of 14 to 17 exhibits excellent solubility in the cationic curing polydimethylsiloxane (a). Therefore, in the drying step after the coating step, even if the organic solvent dries and the concentration of the cationic curing polydimethylsiloxane (a) in the release layer forming composition is increased, it can still be kept in a uniformly dissolved state, without agglomeration and well leveled, and a smooth release layer can be obtained. In addition, as long as the content is 10 mass % or more, since the cationic curing polydimethylsiloxane (a) can remain dissolved for a long time during drying, there is no need to worry about agglomeration during drying and deterioration of smoothness, so it is better. The details of the aforementioned organic solvent with a SP value (δ) of 14 or more and 17 or less will be described later.

In the present invention, additives such as adhesion enhancers and antistatic agents may be added to the release layer as long as they do not hinder the effect of the present invention. In addition, in order to improve the adhesion to the substrate, it is also preferred to apply anchor coating, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc. to the surface of the polyester film before the release coating layer is provided.

When the release film obtained by the present invention is used to release the ceramic green body, the release force is preferably 0.01 mN/mm to 2.0 mN/mm. More preferably, it is 0.05 mN/mm to 1.0 mN/mm. If the release force is 0.01 mN/mm or more, there is no need to worry about the ceramic green body bulging during transportation. If the release force is 2.0 mN/mm or less, there is no need to worry about the ceramic green body being damaged during the release.

The release film obtained by the present invention uses a highly flat substrate film, so even if the thickness of the release layer is less than 1.0 μm, or even less than 0.5 μm, or even less than 0.3 μm, the surface of the release layer can still be smooth. Therefore, the amount of solvent and resin used can be reduced, which is good for the environment, and the release film for ultra-thin ceramic green body molding can be produced at a low cost.

(Manufacturing method of release film) In another embodiment of the present invention, a manufacturing method of a release film for resin sheet molding is provided, which has the following steps. The coating step is to coat the release layer forming composition on the surface layer A of the polyester film having the surface layer A, wherein the surface layer A is a layer substantially free of inorganic particles, and the release layer forming composition contains cationic curing polydimethylsiloxane (a); the drying step is to heat and dry the polyester film coated with the release layer forming composition, wherein the heat drying comprises a first drying step and a subsequent second drying step, wherein the drying temperature T1 in the first drying step is higher than the drying temperature T2 in the second drying step; and the photocuring step is to irradiate active energy rays after the drying step to cure the release layer forming composition.

In the manufacturing method of the present invention, by enhancing the first drying condition (enhanced drying), the resin constituting the release layer is prevented from agglomerating, and a release layer with high smoothness can be obtained. Furthermore, by setting the SP value of the solvent in the release layer forming composition to a predetermined value, the resin constituting the release layer is prevented from agglomerating, and a release layer with high smoothness can be obtained. In this way, the first drying step in the present invention has a predetermined condition, and in one embodiment, a release layer with high smoothness can be obtained by using a specific solvent.

The method for producing a release film of the present invention sequentially comprises: a coating step, in which a release layer-forming composition containing at least a cationic curing polydimethylsiloxane (a) is coated on a surface layer A of a polyester film substantially free of inorganic particles; a drying step, in which the film is heated and dried using, for example, a drying oven after coating; and a photocuring step, in which active energy rays are used to cure the film after heating and drying. In particular, it is preferred to adopt a method in which the coating step, the drying step, and the photocuring step are sequentially performed.

According to the manufacturing method of the present invention, it is found that by improving the manufacturing conditions of the coating step, a release layer with high smoothness can be achieved. Specifically, by including an organic solvent with an SP value (δ) of 14 to 17 in the release layer forming composition, the aggregation of the cationic curing polydimethylsiloxane (a) can be suppressed, and an excellent release layer can be obtained. The SP value (δ) can be used to predict the solubility of a substance, and an organic solvent with an SP value (δ) of 14 to 17 exhibits excellent solubility for the cationic curing polydimethylsiloxane (a). Therefore, in the drying step after the coating step, even if the organic solvent dries up and the concentration of the cationic curing polydimethylsiloxane (a) in the release layer forming composition is increased, the cationic curing polydimethylsiloxane (a) can still be kept in a uniformly dissolved state and will not aggregate but be well leveled, thereby obtaining a smooth release layer.

The content of the organic solvent having an SP value (δ) of 14 to 17 contained in the release layer forming composition is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to 100 parts by mass of the release layer forming composition. If it is 10% by mass or more, it is preferred because the cationic curing polydimethylsiloxane (a) can remain dissolved for a long time during drying, so there is no need to worry about the deterioration of smoothness due to aggregation during drying. For example, the content of the organic solvent having an SP value (δ) of 14 to 17 is 80% by mass or less, for example, 65% by mass or less, or less than 50% by mass, relative to 100 parts by mass of the release layer forming composition.

The SP value (δ) in this manual adopts the Hidbrook solubility parameter. In practice, the Hidbrook solubility parameter can be calculated from the Hansen solubility parameters (HSP value) using formula 1. SP value (δ) = ((δ _d ) ² + (δ _p ) ² + (δ _h ) ² ) ^1/2 ... (Formula 1) Here, (δ _D ) is the dispersion force term, (δ _P ) is the polar term, and (δ _H ) is the hydrogen bond term. The way of thinking that the Hidbrook solubility parameter is decomposed into three components is the Hansen solubility parameter. In addition, the value can also be calculated using computer software such as HSPiP (Hansen Solubility Parameters in Practice). The values described in this manual use the HSP values recorded in the database in HSPiP ver4.0, and the values calculated using Formula 1 are used.

Examples of organic solvents having an SP value (δ) of 14 to 17 include n-hexane (δ: 14.9), n-heptane (δ: 15.3), n-octane (δ: 15.5), isopropyl ether (δ: 15.8), 1,1-diethoxyethane (δ: 15.9), methylcyclohexane (δ: 16.0), cycloheptane (δ: 16.5), and cyclohexane (δ: 16.8).

The coating weight of the release layer forming composition is preferably 10 g/m ² or less, and more preferably 8 g/m ² or less. If the coating weight is 10 g/m ² or less, for example, when coating is performed by gravure coating, the contact portion between the film and the gravure roll becomes less likely to cause turbulence, and a release layer with excellent smoothness can be obtained, which is better.

In the present invention, the release layer forming composition preferably contains two or more types of solvents, at least one of which is a solvent having an SP value (δ) of 14 to 17 as mentioned above, and at least one of which has a boiling point of 100°C or above. By adding a solvent with a boiling point of 100°C or above, sudden boiling during drying can be prevented, the coating can be made even, and the smoothness of the coating surface after drying can be improved. The amount of solvent added is preferably about 10% to 70% by mass relative to the entire release layer forming composition. Examples of solvents with a boiling point of 100°C or above include toluene, xylene, n-octane, cyclohexanone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monopropyl ether, isobutyl acetate, n-butanol, etc.

In the present invention, the coating liquid of the release layer forming composition is preferably filtered before application. There is no particular limitation on the filtering method, and known methods can be used, preferably using a surface type, depth type, or adsorption type box filter. By using a box filter, it is preferably used when the coating liquid is continuously fed from the tank to the application part, and filtering can be performed with high productivity and high efficiency. The filtering accuracy of the filter is preferably such that more than 99% of objects with a size of 1 μm can be removed, and more preferably, more than 99% of objects with a size of 0.5 μm can be filtered out. By using the filter with the above-mentioned filtering accuracy, foreign matter mixed in the coating liquid forming the release layer can be removed, the foreign matter attached to the release film of the present invention can be reduced, and a release layer with excellent smoothness can be obtained, which is better.

The coating liquid may be applied by any known coating method, for example, a roller coating method such as a gravure coating method or a reverse coating method, a rod coating method such as a wire rod, a die coating method, a spray coating method, an air knife coating method, or the like.

As a method for applying the release layer forming composition on the substrate film and drying it, there are well-known hot air drying, infrared heaters, etc., and hot air drying with a fast drying speed is preferred. Drying in a drying furnace is preferred, and any known drying furnace can be used without particular limitation. The drying furnace can be a roller support method or a floating method. If a roller support method is used, the range of air volume during drying can be adjusted more widely, and the air volume can be adjusted according to the type of release layer, so it is preferred.

The drying step can be divided into two drying steps: a constant rate drying step in the initial stage of drying (hereinafter referred to as the first drying step) and a decreasing rate drying step (hereinafter referred to as the second drying step). The two steps are preferably performed in the order of the first drying step and the second drying step, and can be separated by dividing the drying furnace into zones. The first drying furnace can be used for drying in the first (initial) drying step, and the second drying furnace can be used for drying in the second (later) drying step.

The inventors of the present invention have found that in order to improve the smoothness of the release layer, it is important to make the drying temperature T1 in the first drying step higher than the drying temperature T2 in the second drying step. It is preferred that the first drying furnace temperature and the second drying furnace temperature be controlled within the range described below. By manufacturing under such conditions, the constant rate drying time in the first drying step can be shortened, and the reduced rate drying time in the second drying step can be lengthened, so that a release layer with excellent planarity can be obtained.

Furthermore, the inventors of the present invention have found that it is important to increase the temperature in the first drying furnace to shorten the constant rate drying time. More specifically, the drying temperature T1 is preferably 90°C to 180°C, and preferably 100°C to 150°C. By increasing the temperature in the first drying furnace to shorten the constant rate drying time, it is preferable to prevent the cation-curing polydimethylsiloxane (a) contained in the release layer forming composition from agglomerating. The higher the temperature of the first drying furnace, the shorter the constant rate drying time, but if the temperature is too high, the planarity of the film will deteriorate due to heat, so it is preferably below 180°C. If it is above 90°C, the drying capacity becomes sufficient, so it is preferable.

The temperature in the second drying furnace is preferably 60° C. to 140° C., more preferably 80° C. to 120° C. In the second drying step, it is preferable to extend the drying time so that the surface of the release layer before light curing will not become rough, thereby improving the smoothness of the release layer.

For example, the constant rate drying time in the first drying step is preferably shorter than the decreasing rate drying time in the second drying step. This can prevent the deterioration of the film planarity, and further, drying can be performed without making the surface of the release layer rough before photocuring, thereby improving the smoothness of the release layer.

The time from coating to entering the first drying furnace is preferably 0.1 seconds to 2.5 seconds, preferably 0.1 seconds to 2.0 seconds, and the shorter the better. By shortening the time required to enter the first drying furnace, the drying time in the first drying step can be shortened, and the aggregation of the cationic curing polydimethylsiloxane (a) can be suppressed, so that a release layer with excellent smoothness can be obtained. The time required to enter the drying furnace can be calculated from the processing speed and the structure of the processing machine.

The manufacturing method of the present invention includes a photocuring step of irradiating active energy rays after the drying step to cure the release layer forming composition. In the photocuring step, the dried release layer forming composition is subjected to a cationic curing reaction by irradiating active energy rays. The active energy rays used can be ultraviolet rays, electron beams, and other known technologies, preferably ultraviolet rays. The cumulative amount of light when ultraviolet rays are used can be expressed as the product of the illuminance and the irradiation time. For example, 10mJ/ ^cm2 to 500mJ/ ^cm2 is preferred. By setting it to above the aforementioned lower limit, the release layer can be sufficiently cured, so it is preferred. By setting it to below the aforementioned upper limit, it is preferred to suppress heat damage to the film caused by the heat during irradiation, and to maintain the smoothness of the surface of the release layer, so it is preferred.

When irradiating the active energy ray, it is better to hold the inner surface of the film with a backup roller. By setting the backup roller, the distance relative to the active energy ray source can be kept constant and the irradiation can be uniform, so it is better. In addition, it is better to irradiate the active energy ray while cooling the film by cooling the surface of the backup roller. By cooling, even if the active energy ray is irradiated, the film is not easily damaged by heat, and the smoothness of the release layer surface can be maintained, so it is better.

In one aspect, the manufacturing method of the present invention provides a method for manufacturing a release film, which is used to manufacture a resin sheet containing an inorganic compound.

(Resin sheet) The resin sheet in the present invention is not particularly limited as long as it is a sheet containing resin. In one embodiment, the release film of the present invention is a release film for forming a resin sheet containing an inorganic compound. Examples of the inorganic compound include metal particles, metal oxides, minerals, and the like, such as calcium carbonate, silica particles, aluminum oxide particles, and barium titanate particles. Since the present invention has a highly smooth release layer, even in an embodiment in which the resin sheet contains such an inorganic compound, it is possible to suppress the defects that may be caused by the inorganic compound (such as damage to the resin sheet, the problem that the resin sheet becomes difficult to peel off from the release layer). The resin component that forms the resin sheet can be appropriately selected according to the application. In one embodiment, the resin sheet containing an inorganic compound is a ceramic green body. For example, the ceramic green body may contain barium titanate as an inorganic compound. In addition, the resin component may contain, for example, a polyvinyl butyral resin. In one embodiment, the thickness of the resin sheet is greater than 0.2 μm and less than 1.0 μm. For example, the present invention may provide a method for manufacturing a release film, which is used to manufacture a resin sheet containing such an inorganic compound. In addition, the method for manufacturing a release film for resin sheet molding in the present invention may also include: a step of molding a resin sheet having a thickness of greater than 0.2 μm and less than 1.0 μm.

(Ceramic green body and ceramic capacitor) Generally speaking, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, a first internal electrode and a second internal electrode are alternately arranged along the thickness direction. The first internal electrode is exposed at the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed at the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

In one embodiment, the release film of the present invention is a release film for manufacturing ceramic green bodies, and is used to manufacture such a laminated ceramic capacitor. For example, the method for manufacturing ceramic green bodies using the release film for manufacturing ceramic green bodies of the present invention to form ceramic green bodies can form ceramic green bodies having a thickness of 0.2 μm or more and 1.0 μm or less. In more detail, for example, the following method is used to manufacture ceramic green bodies. First, the release film of the present invention is used as a carrier film, and a ceramic slurry for forming a ceramic body is applied thereon and dried. The thickness of the ceramic green body is gradually required to be an extremely thin product of 0.2 μm to 1.0 μm. On the coated and dried ceramic green body, a conductive layer for forming the first internal electrode or the second internal electrode is printed. A mother laminated body can be obtained by appropriately laminating and pressing a ceramic green body, a ceramic green body printed with a conductive layer for constituting a first internal electrode, and a ceramic green body printed with a conductive layer for constituting a second internal electrode. The mother laminated body is cut into a plurality of pieces to produce a green ceramic body. The green ceramic body is fired to obtain a ceramic body. Thereafter, a first external electrode and a second external electrode can be formed to complete a laminated ceramic capacitor. [Example]

The present invention is further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments. The characteristic values used in the present invention are evaluated using the following method.

(Release layer thickness) The cut release film is embedded in resin and sliced into ultra-thin slices using a super microtome. After that, a JEM2100 transmission electron microscope manufactured by JEOL Ltd. is used to observe the cross section, and the thickness of the release layer is measured from the observed TEM image. When the thickness is too thin to be accurately evaluated by cross-sectional observation, a reflection spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., FE-3000) is used instead for measurement.

(Weight of release layer) In this specification, the weight of the release layer per 1 μm thickness is used as the weight value calculated as 1 g/m ^2. For example, when the thickness of the release layer measured by the above method is 0.2 μm, the total weight of the release layer is 0.2 g/m ^2. In addition, the weight of the cationic curing polydimethylsiloxane (a), the weight of the cationic curing resin (b), and the weight of the acid generator (c) contained in the release layer are values calculated from the mixing ratio of each component contained in the release layer forming composition and the total weight of the release layer. For example, when the release layer thickness is 0.2 μm and the release layer weight ratio of the cation-curing polydimethylsiloxane (a) is 5 parts by mass, the weight of the cation-curing polydimethylsiloxane (a) contained in the release layer is 0.01 g/m ² . In addition, the release layer weight ratio (mass %) is calculated based on the total of component (a) and component (b) being 100 parts by mass.

(Amount of release layer forming composition applied) The value calculated from the weight of the liquid consumption of the release layer forming composition used in the application step and the processing area is used.

(Time from coating to the first drying furnace) The value calculated using the film travel distance from the coating area to the first drying furnace and the processing speed.

(Regional surface roughness Sa, maximum protrusion height Sp) Using a non-contact surface shape measurement system (VertScanR550H-M100), the measurement was performed under the following conditions. The regional surface average roughness (Sa) is the average value of 5 measurements, and the maximum protrusion height (Sp) is the maximum value of 5 measurements after excluding the maximum and minimum values after 7 measurements. (Measurement conditions) ・Measurement mode: WAVE mode ・Objective lens: 50x ・0.5×Tube lens ・Measurement area 187μm×139μm (Analysis conditions) ・Surface correction: 4 corrections ・Interpolation processing: Complete interpolation

(Number of protrusions with a height of 10nm or more, number of protrusions with a height of 5nm or more) Particle analysis was performed using the measurement data showing the center value from a total of 7 measurements of the above-mentioned maximum protrusion height. Particle analysis was performed using the analysis software of VertscanR550H-M100 under the following conditions. Particle analysis was performed using the surface roughness of the above-mentioned area, the maximum protrusion height measurement, and the measurement area of the same area to calculate the number of protrusions with a maximum height of 10nm or more, or the number of protrusions with a height of 5nm or more. The number of protrusions is calculated using a value converted to ^1mm2 . (Particle analysis conditions) ・Surface correction: 4 corrections ・Storage processing: Complete interpolation ・Protrusion analysis ・Base height: Zero surface

(Ceramic sheet peeling force) The slurry composition I composed of the following materials was stirred and mixed for 10 minutes, and dispersed for 10 minutes using a bead mill with zirconia beads of 0.5 mm in diameter to obtain a primary dispersion. Then, the slurry composition II composed of the following materials was added to the primary dispersion at a ratio of (slurry composition I): (slurry composition II) = 3.4:1.0, and dispersed for 10 minutes using a bead mill with zirconia beads of 0.5 mm in diameter to obtain a ceramic slurry. (Pulp composition I) Toluene     ... Dioctyl phthalate                                                              3.3 parts by mass Polyvinyl butyral (Eslek BM-S manufactured by Sekisui Chemical Co., Ltd.)       16.3 parts by mass 1-Ethyl-3-methylimidazolium ethyl sulfate                                   0.5 parts by mass Next, the release surface of the obtained release film sample was coated with the dried slurry to a thickness of 1.0 μm using an applicator, and dried at 60°C for 1 minute to obtain a release film with a ceramic green body. The obtained release film with ceramic green body was decharged using a decharger (SJ-F020 manufactured by Keyence Corporation), and then peeled using a peeling tester (VPA-3 manufactured by Kyowa Interface Sciences, Inc., load cell load 0.1N) at a peeling angle of 90 degrees, a peeling temperature of 25°C, and a peeling speed of 10m/min. Regarding the peeling direction, a double-sided adhesive tape (made by Nitto Denko Co., Ltd., No. 535A) is attached to the SUS (stainless steel) plate attached to the peeling tester, and the release film is fixed on the double-sided adhesive tape in the form of bonding the ceramic green body side to the double-sided adhesive tape, and peeling is performed by pulling the side of the release film. The average value of the peeling force with a peeling distance of 20mm to 70mm among the measured values is calculated, and this value is used as the peeling force. The measurement is carried out 5 times in total, and the average value of the peeling force is used for evaluation. The value of the peeling force obtained is judged according to the following criteria. ○: 0.1mN/mm or more but less than 1.0mN/mm ×: 1.0mN/mm or more

(Pinhole evaluation of ceramic green body) Similar to the evaluation of the releasability of the ceramic slurry described above, a ceramic green body with a thickness of 1 μm is formed on the release surface of the release film. Next, the release film with the formed ceramic green body is peeled off to obtain a ceramic green body. The central area of the obtained ceramic green body in the film width direction is illuminated from the opposite side of the ceramic slurry coating surface within a range of 25 ^cm2 , and the pinholes that can be seen by the light penetration are observed, and visual judgment is performed according to the following criteria. 0: No pinholes are generated ×: One or more pinholes are generated

(Preparation of polyethylene terephthalate pellets (PET (I))) A continuous esterification reaction apparatus consisting of a three-stage complete mixing tank having a stirring device, a separator, a raw material loading port, and a product outlet was used as the esterification reaction apparatus. TPA (terephthalic acid) was set to 2 tons/hour, EG (ethylene glycol) was set to 2 mol relative to 1 mol of TPA, and antimony trioxide was set to an amount such that Sb atoms became 160 ppm relative to the generated PET. These slurries were continuously supplied to the first esterification reaction tank of the esterification reaction apparatus, and the reaction was carried out at 255°C at an average residence time of 4 hours under normal pressure. Next, the reaction product in the first esterification reaction tank was continuously taken out of the system and supplied to the second esterification reaction tank, and EG distilled off from the first esterification reaction tank was supplied to the second esterification reaction tank in an amount of 8 mass % relative to the generated PET. Furthermore, an EG solution of magnesium acetate tetrahydrate containing 65 ppm of Mg atoms relative to the generated PET and an EG solution of TMPA (trimethyl phosphate) containing 40 ppm of P atoms relative to the generated PET were added, and the reaction was carried out at 260° C. with an average residence time of 1 hour under normal pressure. Next, the reaction product of the second esterification reaction tank was continuously taken out of the system and supplied to the third esterification reaction tank, while 0.2 mass % of porous silica gel with an average particle size of 0.9 μm, which was dispersed at an average number of times of treatment of 5 paths at a pressure of 39 MPa (400 kg/cm ² ) using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.), and 0.4 mass % of synthetic calcium carbonate with an average particle size of 0.6 μm, to which ammonium salt of polyacrylic acid was attached at 1 mass % per unit of calcium carbonate, were added as 10% of EG slurry, and the reaction was carried out at 260°C at an average residence time of 0.5 hours under normal pressure. The esterification reaction product generated in the third esterification reaction tank was continuously supplied to the three-stage continuous polycondensation reaction device for polycondensation, filtered through a sintered filter with a 95% section diameter of 20 μm stainless steel fiber, and then super-filtered and extruded into water. After cooling, the product was cut into pieces to obtain PET pieces with an inherent viscosity of 0.60 dl/g (hereinafter referred to as PET (I)). The lubricant content in the PET pieces was 0.6 mass %.

(Preparation of polyethylene terephthalate particles (PET(II))) On the other hand, in the production of the above-mentioned PET(I) fragments, PET fragments with an intrinsic viscosity of 0.62 dl/g that are completely free of calcium carbonate, silicon dioxide, etc. particles were obtained (hereinafter referred to as PET(II)).

(Manufacturing of laminated film X1) After drying, these PET chips are melted at 285℃, melted at 290℃ by individual extruders, and filtered in two stages using a filter with 95% stainless steel fiber with a cross-sectional diameter of 15μm and a filter with 95% stainless steel particles with a cross-sectional diameter of 15μm. The PET chips are collected in a feed block and PET (I) is used as the surface. The unstretched polyethylene terephthalate sheet was obtained by laminating the unstretched polyethylene terephthalate sheet with a surface layer B (the layer opposite to the release surface) and PET (II) as the surface layer A (the layer opposite to the release surface) at a speed of 45 m/min. The sheet was extruded (cast) at a speed of 45 m/min. The sheet was electrostatically bonded on a casting drum at 30°C and cooled to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl/g. The layer ratio was adjusted to PET (I)/(II) = 60 mass %/40 mass % by calculating the discharge amount of each extruder. Next, the unstretched sheet was heated with an infrared heater and stretched 3.5 times in the longitudinal direction at a roll temperature of 80°C by the speed difference between the rolls. Afterwards, it was guided to a tenter and stretched 4.2 times in the transverse direction at 140°C. Then, it was heat treated at 210°C in the heat fixation zone. After that, it was subjected to a 2.3% relaxation treatment in the transverse direction at 170°C to obtain a biaxially stretched polyethylene terephthalate film X1 with a thickness of 31μm. The Sa of the surface layer A of the obtained film X1 was 1nm, and the Sa of the surface layer B was 28nm.

(Manufacturing of multilayer film X2) The multilayer film X2 uses E5101 (TOYO TECHNOLOGY (registered trademark) film, manufactured by TOYO TECHNOLOGY CO., LTD.) with a thickness of 25 μm. E5101 has a structure containing particles in surface layer A and surface layer B. The Sa of surface layer A of multilayer film X2 is 24 nm, and the Sa of surface layer B is 24 nm.

(Cationic curing polydimethylsiloxane (a)) (a)-1: UVPOLY215 (made by Arakawa Chemical Industries, solid content 100%)

(Cationic curing resin (b)) (b)-1: Celloxide 2021P (manufactured by Daicel, solid content 100%) (b)-2: X-40-2670 (manufactured by Shin-Etsu Chemical, solid content 100%)

(Acid generator (c)) (c)-1: CPI-101A (made by San-Apro, solid content 50%)

(Example 1) After the release layer forming composition 1 of the following composition was passed through a filter capable of removing 99% or more of foreign matter larger than 0.5 μm, it was applied to the surface layer A of the laminate film X1 using a reverse gravure in a coating amount of 5.0 g/m ^2. After that, the processing speed was adjusted so that it entered the first drying furnace after 0.5 seconds, and the first drying furnace temperature was 120°C and the second drying furnace temperature was 90°C to continuously perform heat drying. After the drying step, ultraviolet rays with a cumulative light amount of 100 mJ/cm ² were irradiated on a cooling roll using an ultraviolet irradiator (H bulb manufactured by Heraeus) to cure the release layer to obtain a release film for resin sheet molding. Furthermore, the smoothness, releasability, and pinhole evaluation of the obtained release film showed good results as shown in Table 1. Thus, the obtained release film for forming a resin sheet is a release film capable of producing a resin sheet having a thickness of, for example, 0.2 μm or more and 1.0 μm or less. In addition, the weight (mg/m ² ) of each component (a), (b), and (c) described in the table represents the content ratio per unit solid content (the weight of each component relative to the total weight of the release layer). (Desorption layer forming composition 1) Methyl ethyl ketone 24.000 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.000 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 48.000 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.039 parts by mass (b) -1 3.883 parts by mass (c) -1 0.078 parts by mass

(Example 2 to Example 4) Except for changing the composition and manufacturing method of the release layer to those described in Table 1, a release film for resin sheet molding was obtained by the same method as Example 1.

(Example 5) A release film for resin sheet molding was obtained in the same manner as in Example 1 except that a release layer forming composition 2 having the following composition was used. (Desorption layer forming composition 2) Methyl ethyl ketone 38.400 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 38.400 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 19.200 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.196 parts by mass (b) -1 3.726 parts by mass (c) -1 0.078 parts by mass

(Example 6) A release film for resin sheet molding was obtained in the same manner as in Example 2 except that the n-heptane in the release layer forming composition was replaced with cyclohexane (SP value (δ): 16.8, (δ _D ): 16.8, (δ _P ): 0.0, (δ _H ): 0.2).

(Example 7, Example 8) Except that the coating amount and solid content ratio were changed to those shown in Table 1, a release film for resin sheet molding was obtained by the same method as in Example 2. At this time, the release layer forming composition 1 was prepared in the same manner as in the organic solvent ratio.

(Example 9) A release film for molding a resin sheet was obtained in the same manner as in Example 1 except that the release layer forming composition 3 was changed to the following composition. (Release layer forming composition 3) Methyl ethyl ketone 24.000 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.000 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 48.000 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.039 parts by mass (b) -2 3.883 parts by mass (c) -1 0.078 parts by mass

(Example 10 to Example 12) Except for changing the composition and manufacturing method of the release layer to those described in Table 1, a release film for resin sheet molding was obtained by the same method as Example 1.

(Example 13) A release film for resin sheet molding was obtained in the same manner as in Example 1 except that a release layer forming composition 4 having the following composition was used. (Desorption layer forming composition 4) Methyl ethyl ketone 38.400 mass parts (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 38.400 mass parts (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 19.200 mass parts (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.196 mass parts (b) -2 3.726 mass parts (c) -1 0.078 mass parts

(Example 14) A release film for resin sheet molding was obtained in the same manner as in Example 2 except that the n-heptane in the release layer forming composition was replaced with cyclohexane (SP value (δ): 16.8, (δ _D ): 16.8, (δ _P ): 0.0, (δ _H ): 0.2).

(Example 15, Example 16) Except that the coating amount and solid content ratio were changed to those shown in Table 1, a release film for resin sheet molding was obtained by the same method as in Example 2. At this time, the release layer forming composition 3 was prepared in the same manner as in the organic solvent ratio.

(Example 17) A release film for molding an ultra-thin resin sheet was obtained in the same manner as in Example 1 except that the release layer-forming composition 5 having the following composition was used. (Release layer forming composition 5) Methyl ethyl ketone 24.950 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.950 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 49.900 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.196 parts by mass (c) -1 0.004 parts by mass

(Example 18) A release film for resin sheet molding was obtained by the same method as Example 1, except that the solid concentration was changed to that shown in Table 1 and the organic solvent ratio was prepared in the same manner as that of release layer forming composition 5.

(Example 19) A release film for resin sheet molding was obtained by the same method as Example 17 except that the manufacturing method was changed to that described in Table 1.

(Example 20) A release film for forming an ultra-thin resin sheet was obtained in the same manner as in Example 1 except that the release layer forming composition 6 was used. (Release layer forming composition 6) Methyl ethyl ketone 39.920 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 39.920 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) n-heptane 19.960 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 0.196 parts by mass (c) -1 0.004 parts by mass

(Example 21) A release film for resin sheet molding was obtained in the same manner as in Example 1 except that n-heptane in release layer forming composition 5 was replaced with cyclohexane (SP value (δ): 16.8, (δ _D ): 16.8, (δ _P ): 0.0, (δ _H ): 0.2).

(Example 22, Example 23) Except for changing the coating amount and solid concentration to those shown in Table 1, a release film for resin sheet molding was obtained by the same method as in Example 17. At this time, the release layer forming composition 5 was prepared in the same manner as in the organic solvent ratio.

(Comparative Example 1) A release film for forming an ultra-thin resin sheet was obtained in the same manner as in Example 1 except that the release layer forming composition 7 was changed to the following composition. (Desorption layer forming composition 7) Methyl ethyl ketone 24.000 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.000 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 48.000 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (b) -1 3.922 parts by mass (c) -1 0.078 parts by mass

(Comparative Example 2) A release film for forming an ultra-thin resin sheet was obtained in the same manner as in Example 1 except that the release layer forming composition 8 was changed to the following composition. (Desorption layer forming composition 8) Methyl ethyl ketone 24.000 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.000 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 48.000 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a) -1 2.941 parts by mass (b) -2 0.981 parts by mass (c) -1 0.078 parts by mass

(Comparative Example 3) A release film for forming an ultra-thin resin sheet was obtained in the same manner as in Example 1 except that the release layer forming composition 9 was changed to the following composition. (Desorption layer forming composition 9) Methyl ethyl ketone 24.000 parts by mass (SP value (δ): 19.1, (δ _D ): 16.0, (δ _P ): 9.0, (δ _H ): 5.1) Toluene 24.000 parts by mass (SP value (δ): 18.2, (δ _D ): 18.0, (δ _P ): 1.4, (δ _H ): 2.0) n-heptane 48.000 parts by mass (SP value (δ): 15.3, (δ _D ): 15.3, (δ _P ): 0.0, (δ _H ): 0.0) (a)-1 3.922 parts by mass (c)-1 0.078 parts by mass

(Comparative Example 4) Except for coating on the laminate film X2, a release film for ultra-thin layer resin sheet molding was obtained by the same method as in Example 10.

[Table 1A] Release film Substrate film Release layer (a) Cationic curing polydimethylsiloxane (b) Cationic curing resin (c) Acid generator Thickness(μm) Total weight of release layer (mg/m ² ) Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Embodiment 1 X1 (a)-1 2.0 (b)-1 194 (c)-1 3.9 0.2 200 Embodiment 2 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 3 X1 (a)-1 39 (b)-1 157 (c)-1 3.9 0.2 200 Embodiment 4 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 5 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 6 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 7 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 8 X1 (a)-1 10 (b)-1 186 (c)-1 3.9 0.2 200 Embodiment 9 X1 (a)-1 2.0 (b)-2 194 (c)-1 3.9 0.2 200 Embodiment 10 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200

[Table 1B] Release film Substrate film Release layer (a) Cationic curing polydimethylsiloxane (b) Cationic curing resin (c) Acid generator Thickness(μm) Total weight of release layer (mg/m ² ) Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Embodiment 11 X1 (a)-1 39 (b)-2 157 (c)-1 3.9 0.2 200 Embodiment 12 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200 Embodiment 13 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200 Embodiment 14 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200 Embodiment 15 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200 Embodiment 16 X1 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200 Embodiment 17 X1 (a)-1 10 - - (c)-1 0.2 0.01 10 Embodiment 18 X1 (a)-1 49 - - (c)-1 1.0 0.05 50 Embodiment 19 X1 (a)-1 10 - - (c)-1 0.2 0.01 10 Embodiment 20 X1 (a)-1 10 - - (c)-1 0.2 0.01 10

[Table 1C] Release film Substrate film Release layer (a) Cationic curing polydimethylsiloxane (b) Cationic curing resin (c) Acid generator Thickness(μm) Total weight of release layer (mg/m ² ) Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Type Weight contained in release layer mg/ ^m2 Embodiment 21 X1 (a)-1 10 - - (c)-1 0.2 0.01 10 Embodiment 22 X1 (a)-1 10 - - (c)-1 0.2 0.01 10 Embodiment 23 X1 (a)-1 10 - - (c)-1 0.2 0.01 10 Comparison Example 1 X1 - - (b)-2 196 (c)-1 3.9 0.2 200 Comparison Example 2 X1 (a)-1 147 (b)-2 49 (c)-1 3.9 0.2 200 Comparison Example 3 X1 (a)-1 196 - - (c)-1 3.9 0.2 200 Comparison Example 4 X2 (a)-1 10 (b)-2 186 (c)-1 3.9 0.2 200

[Table 2A]

[Table 2B]

[Table 2C]

Since Comparative Example 1 does not contain cationic curing polydimethylsiloxane (a), the peeling force of the ceramic sheet is large and peeling is impossible. In Comparative Examples 2 to 4, the number of protrusions with a height of more than 10 nm exceeds 200/ ^mm2 , and pinholes are generated in the green body of the released object. Furthermore, in Comparative Example 4, inorganic particles exist in the entire substrate, and the smoothness of the release film is significantly poor, resulting in damage to the green body, pinholes, etc. [Industrial Applicability]

According to the present invention, by improving the smoothness and releasability of the release layer, a release film can be provided, and even an ultra-thin layer product with a thickness of less than 1 μm can still be formed into a resin sheet with few defects, so that the resin sheet can be manufactured without worrying about defects.

Claims (10)

A release film for resin sheet molding comprises a polyester film as a substrate and a release layer; the polyester film has a surface layer A substantially free of inorganic particles; the release layer is provided on the surface layer A; the release layer is a layer formed by curing a release layer forming composition; the release layer forming composition comprises a cationic curing polydimethylsiloxane (a) and a cationic curing compound (b-1) without a polysiloxane skeleton; the content of the cationic curing polydimethylsiloxane (a) in the release layer is 50 mg/m ² or less; the cationic curing compound without a polysiloxane skeleton (b-1) contained in the release layer forming composition accounts for 80% by mass or more relative to 100 parts by mass of the total of the cationic curing polydimethylsiloxane (a) and the cationic curing compound without a polysiloxane skeleton (b-1); the regional surface roughness (Sa) of the release layer is 2 nm or less; and the number of protrusions with a height of 10 nm or more existing on the surface of the release layer is 200 pieces/mm2 or ^less . A release film for resin sheet molding as recited in claim 1, wherein the maximum protrusion height (Sp) of the release layer is less than 20 nm, and the total number of protrusions with a height of more than 5 nm but less than 10 nm existing on the surface of the release layer and the number of protrusions with a height of more than 10 nm is less than 1500 pieces/ ^mm2 . The release film for resin sheet molding as described in claim 1 or 2, wherein the cationic curing polydimethylsiloxane (a) has at least one functional group selected from vinyl ether group, cyclobutylene oxide group, epoxy group, and alicyclic epoxy group. A release film for resin sheet molding as described in claim 1 or 2, wherein the film thickness of the release layer is greater than 0.1 μm . The release film for resin sheet molding as described in claim 1, wherein the cationic curing compound (b-1) without a polysilicone skeleton has two or more alicyclic epoxy groups in the molecule. A release film for resin sheet molding as described in claim 1 or 2, wherein the release layer forming composition further contains a cyclosiloxane compound (b-2) having an alicyclic epoxy group; the cyclosiloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule; and the total amount of the cation-curing polydimethylsiloxane (a), the cation-curing compound (b-1) without a polysiloxane skeleton, and the cyclosiloxane compound (b-2) in the release layer forming composition is 80% by mass or more. A release film for resin sheet molding as described in claim 1 or 2, wherein the release layer forming composition contains an organic solvent having an SP value (δ) of 14 or more and 17 or less; the release layer forming composition contains the organic solvent having an SP value (δ) of 14 or more and 17 or less in an amount of 10 mass % or more relative to 100 mass parts of the total weight of the release layer forming composition. The release film for resin sheet molding as described in claim 1 or 2 is used to manufacture resin sheets containing inorganic compounds. As described in claim 8, the release film for resin sheet molding, wherein the resin sheet containing an inorganic compound is a ceramic green body. The release film for resin sheet molding as described in claim 1 or 2 is used to mold a resin sheet with a thickness of more than 0.2μm and less than 1.0μm.