Laminated films and methods for manufacturing laminated films

Abstract

[Problem] To provide: a laminated film that provides a resin sheet with high smoothness and good sliding properties. [Solution] A laminated film comprising: a polyester-based substrate film, a release layer, and a resin sheet disposed on the side of the release layer opposite to the substrate, wherein the resin sheet is obtained by curing a resin sheet forming composition containing a resin component (A) and a crosslinking agent (B), the resin sheet substantially does not contain particles, the film thickness (t1) of the resin sheet is 1 μm or more and 20 μm or less, the arithmetic mean height (Sa) of the surface (1) of the resin sheet is 2 nm or more and 30 nm or less, the indentation modulus (E1) of the surface (1) of the resin sheet is 2.0 MPa or more, the indentation modulus (E2) of the surface (2) of the resin sheet is 2.0 MPa or more, the absolute value of the difference between E1 and E2 is 1.5 or less, and the static friction coefficient measured by overlapping the surface (1) of the resin sheet opposite to the release layer side with the surface (2) of the resin sheet on the release layer side is 1.5 or less.

Description

Technical Field

[0001] This invention relates to laminated films containing resin sheets. In particular, it relates to laminated films containing resin sheets used in electronic components and optical applications. Background Technology

[0002] Previously, release films using polyester film as a substrate have been increasingly used as engineering films in solution film fabrication of resin sheets such as adhesive sheets, protective films, polymer electrolyte membranes, and dielectric resin sheets due to their high heat resistance and mechanical properties. In recent years, particularly for electronic components such as dielectric resin sheets used in film capacitors and resin sheets used in optical applications, high smoothness and transparency are required. Therefore, high smoothness is also required for the surface of release films used as engineering films. Consequently, the technologies described in Patent Documents 1-3 have been disclosed, proposing solutions to reduce the surface roughness of the release layer.

[0003] However, in applications such as optics, high smoothness is required to improve transparency. On the other hand, high smoothness can worsen slippage, leading to concerns about scratches and reduced yield during transport processes. Similarly, in electronic components such as film capacitors, smoothness is required to improve electrical properties such as dielectric breakdown voltage. However, excessive smoothness results in poor slippage, causing misalignment and wrinkles when winding the dielectric resin sheet onto the roller, hindering proper winding and potentially degrading the performance of the film capacitor.

[0004] To address these issues, Patent Document 4 proposes a method of adding specific particles to a resin sheet used in optical applications such as polarizing plates to give it sliding properties. Additionally, Patent Document 5 proposes a method for transferring particles from a substrate film to a resin sheet used in films for film capacitors, etc.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2012-144021

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-154273

[0009] Patent Document 3: Japanese Patent Application Publication No. 2015-182261

[0010] Patent Document 4: Japanese Patent Application Publication No. 2019-95661

[0011] Patent Document 5: International Publication No. 2020 / 039638 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] However, in the method of Patent Document 4, the resin sheet contains particles, which raises concerns about insufficient transparency due to increased internal haze. Furthermore, in the method of Patent Document 5, there are concerns about uneven particle transfer to the resin sheet and unstable slip properties.

[0014] To address the aforementioned issues, this invention proposes a laminated film that provides a resin sheet with both high smoothness and good sliding properties, while substantially free of added particles within the resin sheet.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research and found that by coating a smooth substrate film with a coating liquid containing at least a specific resin and a crosslinking agent under specific conditions and then drying / curing it, an uneven surface derived from a phase separation structure is formed on the surface of the laminated film, which successfully gives it good sliding properties and does not contain particles, etc.

[0017] The inventors further discovered that by coating, drying / curing under specific conditions, the resin and crosslinking agent of the resin sheet can be homogenized, thereby reducing the difference in physical properties between the surface and back of the resin sheet.

[0018] That is, the present invention comprises the following components.

[0019] [1] A laminated film comprising: a polyester substrate film, a release layer disposed on at least one side of the substrate film, and a resin sheet disposed on the side of the release layer opposite to the substrate.

[0020] The laminated film satisfies the following (1) to (7):

[0021] (1) The resin sheet is obtained by curing a resin sheet forming composition containing at least resin component (A) and crosslinking agent (B).

[0022] (2) The resin sheet does not actually contain particles.

[0023] (3) The film thickness (t1) of the resin sheet is greater than 1 μm and less than 20 μm.

[0024] (4) The indentation modulus (E1) of the resin sheet surface (1) is above 2.0 MPa.

[0025] (5) The indentation modulus (E2) of the resin sheet surface (2) is above 2.0 MPa.

[0026] (6) The absolute value of the difference between E1 and E2 is less than 1.5.

[0027] (7) The static friction coefficient measured by overlapping the surface (1) of the resin sheet opposite to the aforementioned release layer with the surface (2) of the resin sheet on the aforementioned release layer side is 1.5 or less.

[0028] [2] In one method, the arithmetic mean height (Sa) of the surface (1) of the resin sheet is more than 2 nm and less than 30 nm.

[0029] [3] In one method, the maximum cross-sectional height (St) of the surface (1) of the resin sheet is above 80 nm and below 1000 nm.

[0030] [4] In one embodiment, the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C.

[0031] [5] In one embodiment, the crosslinking agent (B) contained in the resin sheet accounts for more than 10% by mass of the total resin sheet.

[0032] [6] In one embodiment, the weight-average molecular weight of the resin component (A) contained in the resin sheet is 10,000 or more.

[0033] [7] In one method, the surface free energy of the release layer is 40 mJ / m 2 The following, and the adhesion energy is 3.5 mJ / m 2 above.

[0034] [8] In one embodiment, the arithmetic mean height (Sa) of the release layer side surface of the substrate film is 20 nm or less, and the maximum protrusion height (P) is 500 nm or less.

[0035] [9] In another aspect, the present invention provides a method for manufacturing a laminated film, characterized in that it is a method for manufacturing a laminated film as described above, wherein the manufacturing method involves coating a resin sheet onto a substrate film using a solution film-forming method.

[0036]

[10] In one embodiment, the present invention provides a resin sheet that satisfies the following.

[0037] (1) The resin sheet is obtained by curing a resin sheet forming composition containing at least resin component (A) and crosslinking agent (B).

[0038] (2) The resin sheet does not actually contain particles.

[0039] (3) The film thickness (t1) of the resin sheet is greater than 1 μm and less than 20 μm.

[0040] (4) The indentation modulus (E1) of the resin sheet surface (1) is above 2.0 MPa.

[0041] (5) The indentation modulus (E2) of the resin sheet surface (2) is above 2.0 MPa.

[0042] (6) The absolute value of the difference between E1 and E2 is less than 1.5.

[0043] (7) The static friction coefficient measured by overlapping one surface (1) of the resin sheet with the surface (2) of the resin sheet opposite to the aforementioned surface (1) is 1.5 or less.

[0044]

[11] In another embodiment, the present invention provides a resin sheet, which is a sheet peeled from a release film having a substrate and a release layer, wherein the surface free energy of the aforementioned release layer is 40 mJ / m 2 The following, and the adhesion energy is 3.5 mJ / m 2 above.

[0045] Here, the resin sheet of the present invention is preferably a sheet peeled from a release film having a specified surface free energy. However, it is not easy to identify the structure of the resin sheet obtained from the release film, and it is impractical to specify it based on the claims. Therefore, the release film of the present invention is specified in the form of product claims characterized by method features.

[0046] The effects of the invention

[0047] By using the laminated film of the present invention, resin sheets with high smoothness, good lubricity, and uniform physical properties can be provided. By using the resin sheets formed in the present invention, good articles can be provided for various applications. Attached Figure Description

[0048] Figure 1 A simplified cross-sectional view illustrating the structure of the present invention is provided.

[0049] Figure 2 A simplified cross-sectional view illustrating the configuration of the invention in one embodiment. Detailed Implementation

[0050] The laminated thin film of the present invention, such as Figure 1 The image shows a laminated film comprising a polyester-based substrate film 10, a release layer 11 disposed on at least one side of the substrate film 10, and a resin sheet 12 disposed on the side of the release layer 11 opposite to the substrate film 10.

[0051] For example, in optical applications, this invention can provide resin sheets that improve transparency and exhibit high smoothness. Furthermore, it can achieve both high smoothness and high slip properties, which were previously difficult to achieve; for example, it can suppress scratches introduced during transport processes and prevent a decrease in yield.

[0052] Furthermore, in electronic component applications such as film capacitors, resin sheets exhibiting high smoothness can be provided, which improves electrical characteristics such as dielectric breakdown voltage. Moreover, it achieves a balance between high smoothness and high slip properties, which were previously difficult to realize. For example, when winding the dielectric resin sheet onto a roller, it can suppress winding misalignment and wrinkle incorporation, exhibiting excellent winding performance. Therefore, it can be transported while maintaining excellent capacitor performance.

[0053] Furthermore, in this invention, the resin sheet is substantially free of particles, thus avoiding insufficient transparency due to increased internal haze. Additionally, it avoids the problem of uneven particle distribution transferred to the resin sheet, resulting in good slip properties.

[0054] (Substrate film)

[0055] This invention relates to a polyester-based substrate film. The polyester constituting the polyester film used as the substrate of this invention is not particularly limited; any polyester commonly used in film forming as a substrate film can be used. Preferably, a crystalline linear saturated polyester formed from an aromatic diacid component and a glycol component is preferred; further suitable examples include polyethylene terephthalate, polyethylene naphthalate-2,6-dicarboxylate, polybutylene terephthalate, polypropylene terephthalate, or copolymers in which these resins are the main components. Polyester films formed from polyethylene terephthalate are particularly suitable.

[0056] Polyethylene terephthalate (PET) can be made by copolymerizing PET repeating units preferably 90 mol% or more, more preferably 95 mol% or more, and copolymerizing small amounts of other dicarboxylic acids and glycols. For cost reasons, it is preferable to manufacture the film solely from terephthalic acid and ethylene glycol. Furthermore, known additives, such as antioxidants, light stabilizers, UV absorbers, and crystallizing agents, can be added to the extent that they do not impair the effects of the film of the present invention. For reasons such as high biaxial modulus of elasticity, biaxially oriented polyester films are preferred.

[0057] The intrinsic viscosity of the aforementioned polyethylene terephthalate film is preferably 0.50–0.70 dl / g, more preferably 0.52–0.62 dl / g. When the intrinsic viscosity is 0.50 dl / g or higher, breakage is more likely during the stretching process, which is undesirable. Conversely, when the intrinsic viscosity is 0.70 dl / g or lower, the cutability is good when cutting to the specified product width, and dimensional defects do not occur, which is therefore preferred. Furthermore, the raw material granules are preferably thoroughly vacuum dried.

[0058] The method for manufacturing the polyester film in this invention is not particularly limited, and conventionally used methods can be used. For example, the aforementioned polyester is melted in an extruder, extruded into a film, and cooled on a rotary cooling drum to obtain an unstretched film. This unstretched film is then stretched to obtain the desired film. For mechanical properties, biaxial stretching is preferred. The biaxially stretched film can be obtained by sequentially biaxially stretching a longitudinally or transversely uniaxially stretched film in either the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in both the longitudinal and transverse directions.

[0059] In this invention, the stretching temperature during polyester film stretching is preferably set above the secondary transformation point (Tg) of the polyester. The stretching is preferably 1 to 8 times, and particularly preferably 2 to 6 times, along both the longitudinal and transverse directions.

[0060] The aforementioned polyester film preferably has a thickness of 6 μm or more and 50 μm or less, more preferably 8 μm or more and 31 μm or less, and even more preferably 10 μm or more and 28 μm or less. If the film thickness is 6 μm or more, there are no concerns about heat deformation during film production, the processing of the release layer, or the molding of the resin sheet, which is preferable. On the other hand, if the film thickness is 50 μm or less, the roll diameter is small when rolled, which allows for a longer roll length of the molded resin sheet, and is therefore preferable.

[0061] When the polyester film used as the substrate film has a multilayer structure as described later, the overall film thickness of the substrate film falls within the range mentioned above.

[0062] The aforementioned polyester film can be a single layer or a multilayer consisting of two or more layers. Preferably, it has at least one surface layer A that is substantially free of particles on one side. In one embodiment, the polyester film serving as the substrate film has a surface layer A on the resin sheet side. When the substrate film is a laminated polyester film composed of two or more layers, it is preferable to have a surface layer B, which may contain particles, on the opposite side of the substantially particle-free surface layer A. As a laminated configuration, when the layer on the resin sheet side is designated as surface layer A, the layer on the opposite side is designated as surface layer B, and the other core layers are designated as layer C, examples of laminated structures in the thickness direction include A / B or A / C / B.

[0063] Layer C can be composed of multiple layers. Alternatively, surface layer B may not contain particles. In this case, to impart slip properties for winding the film into a roll, it is preferable to provide a coating layer containing particles and a binder on surface layer B.

[0064] In the polyester film of this invention, the surface layer A located on the surface where the resin sheet is formed is preferably substantially free of particles. Furthermore, the arithmetic mean height (Sa) of the surface layer A of the polyester film, i.e., the arithmetic mean height (Sa) of the release layer side surface of the substrate film, is preferably 20 nm or less. More preferably, the arithmetic mean height (Sa) is 10 nm or less. If Sa is 20 nm or less, it is less likely to cause pinholes and localized thickness unevenness during resin sheet forming, which is preferable. It can be said that the smaller the arithmetic mean height (Sa) of the surface layer A, the better, but it can also be 0.1 nm or more. Here, when the release layer, etc., described later is provided on the surface layer A, it is preferable that the release layer is substantially free of particles, and it is preferable that the arithmetic mean height (Sa) of the stacked release layers falls within the aforementioned range. In this invention, "substantially free of particles," for example, inorganic particles, when quantifying inorganic elements by fluorescence X-ray analysis, means a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because, even without actively adding particles to the film, contaminants from foreign matter, raw resins, or dirt adhering to pipelines and equipment during the film manufacturing process can detach and sometimes mix into the film.

[0065] The maximum protrusion height (P) of the surface layer A of the polyester film, i.e., the maximum protrusion height (P) of the release layer side surface of the substrate film, is, for example, 500 nm or less, preferably 200 nm or less, more preferably 150 nm or less, further preferably 100 nm or less, for example 85 nm or less, and particularly preferably 50 nm or less. If the maximum protrusion height (P) is 500 nm or less, no defects such as pinholes and localized thinning occur during resin sheet formation, resulting in a good yield, which is preferred.

[0066] The smaller the value of P in the surface layer A of the polyester film, the better, but it can also be 1 nm or more, or even 3 nm or more. Here, when a release layer or the like described later is provided on the surface layer A, it is preferable that the maximum protrusion height (P) of the release layer after stacking falls within the aforementioned range.

[0067] In the polyester film of this invention, from the viewpoint of film slippage and ease of air removal, the surface layer B, which forms the opposite side of surface layer A, preferably contains particles, and particularly preferably uses silica particles and / or calcium carbonate particles. The total particle content in surface layer B is preferably 5000 to 15000 ppm. In this case, the arithmetic mean height (Sa) of the film in surface layer B is preferably in the range of 1 to 40 nm, more preferably in the range of 5 to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5000 ppm or more and Sa is 1 nm or more, when the film is rolled into a roll, air can be uniformly removed, resulting in good winding posture and good planarity, thus making it suitable for manufacturing resin sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15000 ppm or less and Sa is 40 nm or less, lubricant aggregation is less likely to occur, and coarse protrusions are not formed; therefore, the quality is stable and preferred during resin sheet molding.

[0068] As for the particles contained in the aforementioned surface layer B, inactive inorganic particles and / or heat-resistant organic particles, other than silica and / or calcium carbonate, can be used. From the viewpoints of transparency and cost, silica particles and / or calcium carbonate particles are more preferred, but as other inorganic particles that can be used, examples include alumina-silica composite oxide particles and hydroxyapatite particles. Furthermore, as heat-resistant organic particles, examples include cross-linked polyacrylic acid particles, cross-linked polystyrene particles, and benzoguanamine-based particles. In addition, when using silica particles, porous colloidal silica is preferred; when using calcium carbonate particles, from the viewpoint of preventing lubricant detachment, light calcium carbonate with a surface treatment using a polyacrylic acid-based polymer compound is preferred.

[0069] 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, particularly preferably 0.5 μm or more and 1.0 μm or less. If the average particle size is 0.1 μm or more, the substrate film exhibits good sliding properties, which is preferable. Furthermore, if the average particle size is 2.0 μm or less, there is no concern about pinholes forming in the resin sheet due to coarse particles in the surface layer B, which is preferable.

[0070] The surface layer B described above may also contain particles made of two or more different materials. Alternatively, it may contain particles of the same type but with different average particle sizes.

[0071] When surface layer B does not contain particles, it is preferable that surface layer B has a slip-resistant properties due to a coating layer containing particles. This coating layer is not particularly limited, but an online coating method during the film-making process of a polyester film is preferred. When surface layer B does not contain particles but has a coating layer containing particles, for the same reasons as the arithmetic mean height (Sa) of surface layer B described above, the arithmetic mean height (Sa) of the surface of the coating layer is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm.

[0072] On the surface layer A, which is a layer on one side of the resin sheet, from the viewpoint of reducing pinholes, it is preferable not to use recycled raw materials to prevent the mixing of particles such as lubricant.

[0073] The thickness ratio of the layer on one side of the resin sheet, i.e., surface layer A, is preferably 20% to 50% of the total thickness of the substrate film. If it is 20% or more, it is less susceptible to the influence of particles contained in the surface layer B, etc., from within the film, and the arithmetic mean height (Sa) is more likely to meet the above range, which is preferable. If it is 50% or less of the total thickness of the substrate film, the proportion of recycled materials used in surface layer B can be increased, and the environmental impact is reduced, which is preferable.

[0074] Furthermore, from an economic point of view, 50-90% by mass of recycled materials from film scraps and plastic bottles can be used in the layers other than surface layer A (surface layer B or the aforementioned intermediate layer C). In this case, it is also preferable that the type, amount, particle size, and arithmetic mean height (Sa) of the lubricant contained in surface layer B meet the above-mentioned ranges.

[0075] In addition, to improve the adhesion of subsequent coatings such as release layers, or to prevent static electricity, a coating layer can be applied to the surface of surface layer A and / or surface layer B on the film before stretching or after uniaxial stretching during the film-making process, or corona treatment can be performed. When a coating layer is applied to surface layer A, the coating layer preferably does not contain particles.

[0076] (release layer)

[0077] This invention includes a release layer disposed on at least one side of a substrate film, for example, a release layer between the substrate film and a resin sheet. The resin constituting the release layer is not particularly limited; silicone resins, fluoropolymers, alkyd resins, various waxes, aliphatic olefins, etc., can be used, either alone or in combination of two or more resins. When the resin sheet described later contains a crosslinking agent, the inclusion of silicone resin improves the release properties, which is therefore preferable.

[0078] It should be noted that in this specification, the substrate and release layer laminate is sometimes simply referred to as the release film.

[0079] The release layer may, for example, contain a silicone resin. Silicone resins are resins with an intramolecular silicone structure; examples include curable silicone resins, silicone-grafted resins, and alkyl-modified silicone resins. However, from the viewpoint of migration, reactive curable silicone resins are preferred. As reactive curable silicone resins, addition reaction systems, condensation reaction systems, and UV or electron beam curing systems can be used. More preferably, low-temperature curable addition reaction systems and UV or electron beam curing systems that can be processed at low temperatures are also suitable. By using these, the coating process of the polyester film can be performed at low temperatures. Therefore, a polyester film with less thermal damage during processing and high planarity is obtained, and defects such as pinholes can be reduced during the manufacturing of the resin sheet of the film.

[0080] Examples of silicone resins used in addition reaction systems include polydimethylsiloxanes and hydrosiloxanes with vinyl groups introduced into their terminal or side chains via a platinum catalyst, followed by curing. In this case, using a resin that can cure at 120°C for less than 30 seconds allows for low-temperature processing, which is more preferable. Examples include low-temperature addition-curing (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV-curing (LTC851, BY24-510, BY24-561, BY24-562, etc.) manufactured by Dow Toray Co., Ltd.; solvent addition + UV curing (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and Dual-cure curing (X62-2835, X62-2834, X62-1980, etc.) manufactured by Shin-Etsu Chemical Co., Ltd.

[0081] Organosilicon resins used as condensation reaction systems include, for example, polydimethylsiloxanes with OH groups at the ends and polydimethylsiloxanes with H groups at the ends, which are condensed using an organotin catalyst to form a three-dimensional cross-linked structure.

[0082] Examples of UV-curable silicone resins include those that utilize the same free radical reaction as conventional silicone rubber (the most basic type), those that introduce unsaturated groups and then cure under UV light, those that decompose ononium salts to produce strong acids, thereby cleaving and crosslinking epoxy groups, and those that crosslink through the addition reaction of thiols to vinylsiloxanes. Alternatively, electron beams can be used instead of UV light. Electron beams have higher energy than UV light, and in the case of UV curing, free radical-based crosslinking reactions can occur even without an initiator. Examples of resins used include UV-curable silicones manufactured by Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, ​​X62-7629, X62-7660, etc.), UV-curable silicones manufactured by MOMENTIVE PERFORMANCEMATERIALS KK (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curable silicones manufactured by Arakawa Chemical Industry Co., Ltd. (SILCOLEASE UV POLY200, POLY215, POLY201, KF-UV265AM, etc.).

[0083] As for the aforementioned UV-curable silicone resins, acrylate-modified or epoxy-propylene-modified polydimethylsiloxanes can also be used. Mixing these modified polydimethylsiloxanes with multifunctional acrylate resins, epoxy resins, etc., and using them in the presence of an initiator, also exhibits good mold release properties.

[0084] Examples of other resins that can be used include alkyd resins modified with stearyl groups, lauryl groups, etc., acrylic resins, or alkyd resins, acrylic resins, olefin resins, etc., obtained by the reaction of methylated melamine.

[0085] Examples of amino alkyd resins obtained from the above-mentioned reactions of methylated melamine include Tesfine 303, Tesfine 305, and Tesfine 314 manufactured by Hitachi Chemical Co., Ltd. Examples of amino acrylic resins obtained from the reactions of methylated melamine include Tesfine 322 manufactured by Hitachi Chemical Co., Ltd.

[0086] When the above-described resin is used in the release layer of the present invention, it can be used alone or in combination with two or more resins. Furthermore, to adjust the peel strength, additives such as light peeling additives and heavy peeling additives can be mixed in.

[0087] In the release layer of the present invention, additives such as adhesion improvers and antistatic agents may also be added. In addition, in order to improve the adhesion with the substrate, it is preferable to pretreat the surface of the polyester film before setting the release layer by means of anchor coating, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc.

[0088] In this invention, the thickness of the release layer can be set according to its intended use and is not particularly limited. Preferably, the thickness of the cured release layer is in the range of 0.005 to 2.0 μm. If the thickness of the release layer is 0.005 μm or more, it is preferable to maintain the peeling performance. Furthermore, if the thickness of the release layer is 2.0 μm or less, the curing time is not excessively long, and there is no concern about uneven resin sheet thickness caused by reduced flatness of the release film. Additionally, since the curing time is not excessively long, there is no concern about resin aggregation forming the release coating layer, no concern about the formation of protrusions, and therefore, it is preferable to avoid the formation of pinholes in the resin sheet.

[0089] The surface free energy of the release layer disposed on the substrate film of the present invention is preferably 12 mJ / m 2 The above. More preferably, 18 mJ / m 2 The above, further optimized, is 20mJ / m 2 That's all. If it's 12mJ / m 2 Therefore, the solution used to coat the resin sheet is less prone to rebound, making it a preferred choice.

[0090] The surface free energy of the release layer disposed on the substrate film of the present invention is preferably 40 mJ / m 2 Below. More preferably 35 mJ / m 2 The following is a further optimization of 30mJ / m 2 Below. If it is 40mJ / m 2 The following resin sheets exhibit good peelability after molding, and are therefore preferred.

[0091] In this invention, the aforementioned surface free energy refers to the surface free energy of at least the surface of the release layer that is in contact with the resin sheet.

[0092] The water adhesion energy of the release layer of the present invention on the surface in contact with the resin sheet is, for example, 3.0 mJ / m. 2 Above, preferably 3.5 mJ / m 2 The above. More preferably 4.0 mJ / m 2 The above, further optimized, is 5.5 mJ / m 2 That's all. If it's 3.0 mJ / m 2In the case of the above, when the solution of the coating resin sheet is coated, the swelling of the coating end portion is suppressed, which is preferable. When the swelling of the coating end portion during coating is suppressed, when the laminated film is wound into a roll, the standing ears (in Japanese: 耳立ち) are suppressed, and the winding posture becomes good. Therefore, the flatness of the laminated film becomes good, which is preferable.

[0093] In order to improve the water adhesion ability of the surface of the release layer, it can be achieved by adding an additive to the release layer or adjusting the polymer composition. For example, if it is a silicone resin, in the polydimethylsiloxane backbone, a siloxane unit having a phenyl group in the side chain is introduced, or a silicone resin such as a T unit (3-functional) or a Q unit (4-functional) is added, thereby it can be improved.

[0094] In order to improve the water adhesion ability of the surface of the release layer, as a method other than the above, it can also be achieved by changing the composition of the silicone resin. For example, for an addition reaction system silicone resin, polydimethylsiloxane having a vinyl group introduced at the end or side chain and hydrosiloxane are heated under a platinum catalyst to be cured, and the molar amount of the Si-H group of the hydrosiloxane is changed with respect to the molar amount of the vinyl group (Si-Vy) at the end, thereby the water adhesion ability can also be changed. For example, when the Si-H is more with respect to Si-Vy, the water adhesion ability is liable to become higher, and the Si-H / Si-Vi ratio is preferably 1.0 or more, more preferably 1.5 or more, still more preferably 2.0 or more.

[0095] In the release layer of the present invention, not only the above polyester base material but also the arithmetic mean height (Sa) in the release layer is preferably 20 nm or less. Further, the arithmetic mean height (Sa) is particularly preferably 10 nm or less. If Sa is 20 nm or less, it is preferable because pinholes and local thickness unevenness are not likely to occur during resin sheet molding. It can be said that the smaller the arithmetic mean height (Sa) of the release layer is, the more preferable it is, but it can also be 0.1 nm or more.

[0096] In addition, the maximum protrusion height (P) of the release layer is, for example, 500 nm or less, preferably 200 nm or less, more preferably 150 nm or less, further preferably 100 nm or less, for example, 85 nm or less, and particularly preferably 50 nm or less. If the maximum protrusion height (P) is 500 nm or less, when the resin sheet is formed, there is no occurrence of defective points such as pinholes and local thinning, and the yield is good, which is preferable.

[0097] In the present invention, the method for forming the release layer is not particularly limited, and the following method is used: A coating solution in which a resin having releasability is dissolved or dispersed is spread on one surface of a polyester film of a base material by coating or the like, and after removing the solvent and the like by drying, heat drying, thermal curing or ultraviolet curing is performed.

[0098] The coating method for the aforementioned release layer can be any known coating method, such as gravure coating, reverse coating, bar coating, die coating, spray coating, air knife coating, and other methods that have been known for a long time.

[0099] When a thermosetting material is used in the release layer, the drying temperature during solvent drying and heat curing is preferably below 180°C, more preferably below 160°C, further preferably below 140°C, and most preferably below 120°C. The heating time is preferably below 30 seconds, more preferably below 20 seconds, and most preferably below 10 seconds. At temperatures below 180°C, the planarity of the film is maintained, minimizing concerns about uneven resin sheet thickness. At temperatures below 120°C, processing can be performed without compromising the planarity of the film, further reducing concerns about uneven resin sheet thickness, and is therefore particularly preferred.

[0100] There is no particular limitation on the lower limit of the drying temperature, but 60°C or higher is preferred. A release film can be obtained without solvent residue in the release layer at temperatures above 60°C, hence this is preferred.

[0101] When using a UV-curable material in the release layer, the drying temperature during solvent drying and heat curing is preferably below 120°C, more preferably below 100°C, and most preferably below 90°C. The heating time is preferably below 30 seconds, more preferably below 20 seconds, and most preferably below 10 seconds. At temperatures below 120°C, the planarity of the film is maintained, minimizing concerns about uneven resin sheet thickness. At temperatures below 90°C, processing can be performed without compromising the planarity of the film, further reducing concerns about uneven resin sheet thickness, making this particularly preferable.

[0102] There is no particular limitation on the lower limit of the drying temperature, but 60°C or higher is preferred. A release film can be obtained without solvent residue in the release layer at temperatures above 60°C, hence this is preferred.

[0103] When using a UV-curable material in the release layer, it is preferable to perform a curing reaction by irradiating with an active energy ray after the aforementioned solvent has dried. Known techniques such as ultraviolet light or electron beams can be used as the active energy ray, but ultraviolet light is preferred. The cumulative light intensity when using ultraviolet light can be expressed as the product of illuminance and irradiation time. For example, 10–500 mJ / cm² is preferred. 2 Setting the value above the aforementioned lower limit allows for sufficient curing of the release layer, which is therefore preferred. Setting the value below the aforementioned upper limit suppresses thermal damage to the film caused by heat during irradiation and maintains the smoothness of the release layer surface, which is also preferred.

[0104] (Resin sheet)

[0105] The laminated film of the present invention has a resin sheet disposed on the side opposite to the substrate of the release layer.

[0106] For example, the resin sheet laminated on the release film of the present invention is obtained by curing a resin sheet forming composition containing at least resin component (A) and crosslinking agent (B).

[0107] In-depth research was conducted on the resin sheet of the present invention, and it was found that when made under specific conditions, such as the resin sheet forming composition of the present invention described later, the resin component (A) and the crosslinking agent (B) can be cured in a phase-separated state, or a suitable unevenness can be formed on the surface of the resin sheet, which can exhibit the sliding properties of the resin sheet without containing particles in the resin sheet.

[0108] The mass ratio of the added resin component (A) to the crosslinking agent (B) is preferably 80% or more by mass, more preferably 90% or more by mass, and even more preferably 95% or more by mass of the total solid content of the resin sheet. If it contains 80% or more by mass, the physical properties of the resin sheet, such as strength and heat resistance, are improved, so it is preferred.

[0109] The preferred mass ratio of resin component (A) to crosslinking agent (B) is (A) / (B) = 90 / 10 to 50 / 50. If the mixing ratio of crosslinking agent (B) is 10% by mass or more, the unevenness after phase separation is easily increased, and the sliding properties are improved, which is preferred. If the mixing ratio of crosslinking agent (B) is 50% by mass or less, the film strength of the resin sheet will not decrease, and the workability as a sheet is excellent, which is also preferred. It also prevents unreacted crosslinking agent from adhering to the back side of the laminated film during winding. For example, the proportion of crosslinking agent (B) in the resin sheet is preferably 10% by mass or more and 50% by mass or less in the total resin sheet. In one embodiment, the proportion of crosslinking agent (B) in the resin sheet is 10% by mass or more and less than 50% by mass, for example, 15% by mass or more and 45% by mass or less. By including crosslinking agent (B) under such conditions, the above-mentioned effects can be achieved more effectively.

[0110] As for resin component (A), there are no particular limitations, and known resins can be used. For example, epoxy resins, phenoxy resins, polyester resins, urethane resins, fluorinated resins, acrylic resins, olefin resins, imide resins, sulfone resins, etc., can be used. One type can be used, or two or more types can be mixed. The weight-average molecular weight (Mw) of the resin component (A) used in this invention is 10,000 or more, preferably 10,000 or more and 200,000 or less, more preferably 30,000 or more and 100,000 or less. If it is 10,000 or more, the resin sheet has higher strength and better workability, so it is preferred. If it is 200,000 or less, the viscosity of the solution becomes lower and the productivity becomes better when solution film is formed, so it is preferred. The method for determining the weight-average molecular weight (Mw) is not particularly limited, and it can be determined using GPC or the like.

[0111] The crosslinking agent (B) is not particularly limited and any known crosslinking agent can be used. For example, isocyanates, melamine, carbodiimides, oxazoline, etc., can be used; one type or a mixture of two or more can be used. It is preferred to use an agent that reacts with the functional groups contained in the resin component (A). The crosslinking agent (B) contained in the resin sheet forming composition is preferably a liquid at 30°C. In this invention, the liquid only needs to be fluid; for example, the viscosity only needs to be below 10000 mPa·s. By being a liquid at 30°C, the phase separation from the resin component (A) during the drying of the solution-film formed resin sheet can be effectively promoted, and the surface irregularities of the resin sheet become easier to form, which is therefore preferred.

[0112] In the resin sheet, additives can be included in addition to the resin component (A) and crosslinking agent (B) as long as the above-mentioned range is met. However, the resin sheet is substantially free of particles. The resin sheet of the present invention, by being substantially free of particles, makes it easier to achieve, for example, in optical applications, the effect of increased transparency of the molded resin sheet, and improved electrical properties in electronic components such as dielectric sheets used in film capacitors, and is therefore preferred. For example, in optical applications, the haze of the resin sheet can be 2% or less. Alternatively, the haze can be 1% or less. In one embodiment, the haze of the resin sheet is 0.1% or more. Furthermore, for example, in electronic components such as film capacitors, the dielectric breakdown voltage of the resin sheet can be 200V / μm or more. Alternatively, the dielectric breakdown voltage can be 300V / μm or more. In one embodiment, the dielectric breakdown voltage is 500V / μm or less.

[0113] Even though the resin sheet of the present invention does not substantially contain particles, it has minute irregularities on its surface caused by phase separation of the resin component (A) and the crosslinking agent (B), thus exhibiting good sliding properties. The static friction coefficient of the resin sheet peeled from the substrate film is preferably 1.5 or less, more preferably 1.0 or less, and even more preferably 0.8 or less. A static friction coefficient of 1.5 or less provides good winding and travel properties, making handling easier when used in optical applications and electronic component applications, and is therefore preferred. The static friction coefficient of the resin sheet can be 0.1 or more.

[0114] In one method, Figure 2 In this process, the static friction coefficient measured by overlapping the surface (1) of the resin sheet shown by symbol 13, which is opposite to the release layer, with the surface (2) of the resin sheet shown by symbol 14, is 1.5 or less. The static friction coefficient measured under the aforementioned conditions is more preferably 1.0 or less, and even more preferably 0.8 or less. Alternatively, the static friction coefficient can be 0.1 or more.

[0115] Thus, by overlapping the two sides of the resin sheet and measuring the static friction coefficient within the above-mentioned range, the resin sheet of the present invention can achieve both high smoothness and excellent winding and travel properties.

[0116] The arithmetic mean roughness (Sa) of the surface (1) (the side opposite to the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is 2 nm or more and 30 nm or less, more preferably 2 nm or more and 20 nm or less, and even more preferably 2.5 nm or more and 15 nm or less. If it is 2 nm or more, the sliding properties of the resin sheet are better and this is preferred. If it is 30 nm or less, the concern about the generation of defects such as pinholes is reduced when the resin sheet is peeled off from the laminated film and only the resin sheet is wound into a roll.

[0117] The maximum cross-sectional height (St) of the surface (1) (the side opposite to the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is 80 nm or more and 1000 nm or less, more preferably 100 nm or more and 600 nm or less, and even more preferably 150 nm or more and 500 nm or less. If it is 80 nm or more, the sliding properties of the resin sheet are improved, which is preferable. If it is 1000 nm or less, the concern about the generation of defects such as pinholes is reduced when the resin sheet is peeled off from the laminated film and only the resin sheet is wound into a roll.

[0118] It should be noted that the maximum cross-sectional height (St) is the sum of the absolute values ​​of the maximum protrusion height (P) and the maximum valley depth (V).

[0119] The maximum protrusion height (P) of the resin sheet surface (1) (the side opposite to the surface in contact with the release layer) of the laminated film of the present invention is preferably 500 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, and can be 185 nm or less, for example 150 nm or less, particularly preferably 135 nm or less. For example, it can also be 100 nm or less.

[0120] If the maximum protrusion height (P) is less than 500 nm, it is preferable that no defects such as pinholes will occur when the resin sheet is peeled off from the laminated film and only the resin sheet is wound into a roll. The smaller the maximum protrusion height P, the better, but it can be 1 nm or more, 3 nm or more, for example, 35 nm or more.

[0121] By setting the arithmetic mean roughness (Sa) and maximum cross-sectional height (St) of the resin sheet surface (1) of the laminated film of the present invention within the aforementioned ranges, good sliding properties can be obtained even on surfaces with high smoothness. It is particularly preferable to control the maximum cross-sectional height (St) within the aforementioned ranges.

[0122] In one embodiment, the maximum valley depth (V) of the surface (1) of the resin sheet of the laminated film is preferably 45 nm or more and 350 nm or less, for example, 45 nm or more and 300 nm or less, preferably 45 nm or more and 250 nm or less. By having the maximum valley depth (V) within such a range, even if the maximum protrusion height (P) is within the range of 250 nm or less, it becomes easier to control the maximum cross-sectional height (St) within the aforementioned range, which can improve the sliding properties of the resin sheet, and is therefore preferred.

[0123] The arithmetic mean roughness (Sa) of the surface (2) (the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less. If it is 10 nm or less, the concern about the generation of defects such as pinholes is reduced when the resin sheet is peeled off from the laminated film and only the resin sheet is rolled into a roll.

[0124] The film thickness (t1) of the resin sheet of the present invention is 1 μm or more and 20 μm or less. More preferably, it is 1 μm or more and 10 μm or less, and even more preferably, it is 2 μm or more and 8 μm or less. If the film thickness (t1) of the resin sheet is 1 μm or more, it is less likely to break after being peeled from the substrate film, and it can be handled easily, so it is preferred. If the film thickness (t1) of the resin sheet is 20 μm or less, the wet coating film thickness does not become excessively thick during solution film formation, and it is easy to form, so it is preferred.

[0125] The indentation modulus (E1) of the surface (1) and the indentation modulus (E2) of the resin sheet of the present invention are both 2.0 MPa or more. More preferably, at least one of the indentation modulus (E1) of the surface (1) and the indentation modulus (E2) of the surface (2) is 2.2 MPa or more, for example, 2.4 MPa or more. If the indentation modulus is 2.0 MPa or more, the film strength of the resin sheet is increased, and it becomes easier to handle after peeling from the laminated film, therefore this is preferred.

[0126] The upper limit is not specifically set, but it is preferably below 20 MPa. For example, it can be below 10 MPa or below 6 MPa. If it is below 20 MPa, the resin sheet will not become excessively brittle and the handling will be good, so it is preferred.

[0127] The absolute value of the difference between the indentation modulus (E1) and the indentation modulus (E2) of the resin sheet of the present invention, |E1-E2|, is 1.5 or less, for example, less than 1.5, preferably 1.3 MPa or less. More preferably 1.0 MPa or less, and more preferably 0.5 MPa or less. If the difference in indentation modulus is 1.3 MPa or less, there is no difference in the physical properties of the resin sheet in the thickness direction, and a uniform resin sheet can be provided, which is therefore preferred. In order to achieve the above-mentioned range, it is preferable to suppress the segregation of resin component (A) and crosslinking agent (B) in the resin sheet, which can be controlled under the conditions of coating / drying.

[0128] For example, the absolute value of the difference between the indentation modulus (E1) and the indentation modulus (E2), |E1-E2|, is preferably small, and can be 0. In one embodiment, the absolute value |E1-E2| is 0.01 or more, and can be 0.05 or more. By exhibiting the above-mentioned values, the absolute value |E1-E2| results in excellent processability of the resin sheet, such as sliding properties, winding properties, and conveying properties.

[0129] The film thickness (t1) of the resin sheet is not particularly limited and can be measured using known methods. For example, the cross-section can be observed and measured using a contact thickness gauge, an optical interferometer, a scanning electron microscope, or a transmission electron microscope.

[0130] As a method for laminating the resin sheet of the present invention onto a substrate film, it is preferable to form a coating liquid containing at least the above-described resin component (A) and crosslinking agent (B), dissolved or dispersed in an organic solvent, water, etc., onto the release layer using a solution film-forming method. The coating can be performed using a known method similar to the coating method for the release layer. For example, methods already known can be used, such as gravure coating, reverse coating, bar coating, die coating, spray coating, air knife coating, etc.

[0131] After applying the aforementioned coating liquid to the release layer, a heating process is preferably included to allow for the drying and curing of the solvent. The heating method is not particularly limited; hot air, infrared radiation, or the like can be used to heat the coated laminated film. Preferably, the laminated film of the present invention is coated and dried using a roller-to-roll method, and the drying oven is particularly preferably dryer using hot air in a floating or roller-supported manner.

[0132] The drying temperature is as follows: the maximum temperature of the drying oven is preferably 60°C or higher and 160°C or lower, more preferably 70°C or higher and 140°C or lower, and even more preferably 70°C or higher and 130°C or lower. If the temperature is 60°C or higher, there is less residual solvent in the dried resin sheet, and there is no concern about a decrease in the performance of the resin sheet (e.g., electrical properties if used as a dielectric layer), which is preferable. If the temperature is 160°C or lower, there is no concern about wrinkles forming in the laminated film due to heat, which is also preferable. Furthermore, if the temperature is higher than 160°C, excessive phase separation of the resin component and crosslinking agent occurs within the resin sheet, and there is a concern about a decrease in the crosslinking density of the resin sheet; therefore, it is preferable to set the temperature to 160°C or lower.

[0133] In one embodiment, the resin sheet of the present invention is a resin sheet obtained by heating under conditions of 70°C or higher and 130°C or lower.

[0134] The time from applying the aforementioned coating liquid to entering the drying oven is preferably within 5 seconds, more preferably within 3 seconds, and even more preferably within 2 seconds. If it is within 5 seconds, the phase separation between the resin component and the crosslinking agent in the coating liquid will not occur excessively, and there is no concern about a decrease in the crosslinking density of the resin sheet, which is preferable.

[0135] After applying the aforementioned coating solution to the substrate film, the heating time in the drying oven at the maximum temperature is preferably 1 second or more, preferably 2 seconds or more. If it is 1 second or more, the reaction of the crosslinking agent will proceed, which is preferred. The upper limit of the heating time is preferably within 60 seconds, for example, less than 60 seconds, more preferably within 40 seconds, and even more preferably within 20 seconds. If it is within 60 seconds, the segregation of the crosslinking agent on the surface of the resin sheet can be suppressed to an extreme extent, without degrading the performance of the resin sheet, which is preferred.

[0136] By setting the resin sheet of the present invention to the above-described drying conditions, the phase separation of the resin component (A) and the crosslinking agent (B) can be appropriately achieved. The arithmetic mean roughness (Sa) and maximum cross-sectional height (St) of the surface (1) of the resin sheet can be controlled within the aforementioned range, thereby demonstrating good sliding properties of the resin sheet without adding particles to the resin sheet.

[0137] (Laminated thin film)

[0138] The laminated film of the present invention is used in the following steps and thereafter to peel a resin sheet from a substrate film. Therefore, if the peel force from the substrate film is 800 mN / 25 mm width or less, the resin sheet can be peeled off without breakage, which is preferable. More preferably, it is 500 mN / 25 mm width or less, even more preferably 300 mN / 25 mm width or less, and even more preferably 200 mN / 25 mm width or less. The peel force varies depending on the laminated resin sheet, and therefore can be adjusted according to the type of release layer of the substrate film.

[0139] Example

[0140] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. Furthermore, the evaluation method used in the present invention is as described below.

[0141] (Arithmetic mean height (Sa), maximum protrusion height (P), maximum valley depth (V), maximum cross-sectional height (St))

[0142] These values ​​were measured using a non-contact surface shape measurement system (Ryoka Systems Inc., VertScan R550H-M100) under the following conditions. The arithmetic mean height (Sa) is the average of five measurements. The maximum protrusion height (P) and maximum valley depth (V) were measured seven times, and the five maximum values ​​(after removing the maximum and minimum values) were used. The maximum cross-sectional height (St) is the sum of the absolute values ​​of the maximum protrusion height (P) and the maximum valley depth (V).

[0143] (Measurement conditions)

[0144] • Measurement mode: WAVE mode

[0145] • Objective lens: 10x

[0146] · 0.5× Tube lens

[0147] • Measurement area: 936 μm × 702 μm

[0148] (Analysis conditions)

[0149] • Surface correction: 4 corrections

[0150] • Supplementation: Complete supplementation

[0151] • Filter processing: Gaussian cutoff 50μm

[0152] (Surface free energy)

[0153] Under conditions of 25°C and 50% RH, droplets of water (1.8 μL) and diiodomethane (0.9 μL) were prepared on the release surface of the release film using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: DM-701 fully automatic contact angle meter), and their contact angles were measured. The contact angles were taken 10 seconds after each liquid was added to the release film. Based on the "Owens and Wendt" theory, the contact angle data of water and diiodomethane obtained by the aforementioned method were calculated. Based on the dispersion component γd of the surface free energy of the release film, hydrogen bonds, and dipole / dipole interactions, component γh was calculated, and the total of each component was used as the surface free energy γs. In this calculation, the analytical software within the contact angle meter software (FAMAS) was used.

[0154] (Water adhesion energy)

[0155] Under conditions of 25°C and 50% RH, water (10 μL droplet volume) was dropped onto the release surface of the release film using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: DM-701 fully automatic contact angle meter). The stage was continuously tilted 2 seconds after the droplet was added, and the contact angle was measured for each 1° tilt. Furthermore, the slip angle was determined as the angle at which the droplet moved 5 dots from its 0° position, and the adhesion energy was calculated from this. This calculation was performed using the analytical software within the contact angle meter software (FAMAS).

[0156] (film thickness)

[0157] The cut layered films were embedded in resin and then ultrathinly sectioned using an ultramicrotome. Subsequently, they were observed using a JEM2100 transmission electron microscope (TEM) at a direct magnification of 20,000, and the thickness of each layer of the layered film was determined from the observed TEM images.

[0158] (Peeling force)

[0159] The laminated film was cut into strips 25 mm wide and 150 mm long. One end of the substrate film was fixed, and the other end of the resin sheet was loaded. The resin sheet side was stretched at a speed of 300 mm / min, and the T-peel strength was measured. A tensile testing machine (Shimadzu AUTOGRAPH AG-X) was used for the test. The measured value is the average of 5 measurements.

[0160] Peelability is evaluated based on the measured peel force using the following criteria.

[0161] 〇: It can be peeled with a low peel force of less than 100mN / 25mm width, and can also peel from within the film without breaking.

[0162] 〇△: It can be peeled with a peeling force of 300mN / 25mm or less and greater than 100mN / 25mm width.

[0163] △: Peeling can be performed with a peel force greater than 300mN / 25mm width and less than 800mN / 25mm width. In extremely thin sections, partial rupture may sometimes occur.

[0164] ×: Unable to perform stripping.

[0165] (Evaluation of static friction coefficient and sliding properties)

[0166] The static friction coefficient of the resin sheet is determined as follows to evaluate its sliding properties.

[0167] The resin sheet was peeled off from the laminated film and fixed to the bottom of a 1.4 kg metal cuboid, thus exposing the surface (2) of the resin sheet. Next, with the surface (1) of the resin sheet exposed, it was fixed to a flat metal plate with adhesive tape. The metal cuboid was placed with surface (1) in contact with surface (2), and the static friction coefficient was measured at a tensile speed of 200 mm / min under conditions of 23°C and 65% RH.

[0168] Regarding slippage, the following criteria shall be used for judgment.

[0169] : 0.1 < μs ≤ 0.8

[0170] : 0.8 < μs ≤ 1.5

[0171] ×: Exceeds 1.5, or the coefficient of friction is too high to be measured.

[0172] (Electrical properties)

[0173] An aluminum vapor-deposited layer of film was applied to both sides of a resin sheet peeled from a substrate film, and the dielectric breakdown voltage (V / μm) was measured at room temperature. The average value at 10 measurement points was used for evaluation against the following criteria.

[0174] 〇: Dielectric breakdown voltage (BDV value) is above 300V / μm

[0175] △: Dielectric breakdown voltage is above 200V / μm

[0176] ×: Dielectric breakdown voltage is below 200V / μm

[0177] (Indentation Modulus)

[0178] The indentation modulus of the resin sheet was determined as follows.

[0179] The resin sheet is peeled from the laminated film and fixed to a stainless steel sample stage with the test surface facing upwards using double-sided tape. For the test sample, a cantilever is pressed into the sample surface using a scanning probe microscope (Shimadzu SPM-9700) under the following conditions, and the force curve is measured. Based on the shape of the obtained force curve, the elastic modulus is calculated using the JKR2-point method with the software within the device.

[0180] Cantilever: LRCH silicone probe manufactured by Team Nanotec.

[0181] (Spring constant: 0.3 N / m, radius of curvature: 250 nm, cantilever half-apex angle: 45 degrees, Poisson's ratio: set to 0.50)

[0182] Sensitivity: 150 nm / V (The sensitivity value used is the one obtained by using a stainless steel plate as a reference before measurement).

[0183] Scanning speed: 1Hz (2000nm / s)

[0184] *The indentation depth from the sample surface is approximately 20 nm.

[0185] (Preparation of polyethylene terephthalate granules (PET(I)))

[0186] The esterification reactor was a continuous esterification reactor consisting of a three-stage fully mixed tank with a stirrer, a condenser, a raw material inlet, and a product outlet. TPA (terephthalic acid) was supplied at a rate of 2 tons / hour, EG (ethylene glycol) at 2 moles per 1 mole of TPA, and antimony trioxide at 160 ppm relative to the generated PET and Sb atoms. These slurries were continuously fed to the first esterification reactor of the esterification reactor, and the reaction was carried out at atmospheric pressure, with an average residence time of 4 hours and a temperature of 255°C. Next, the reaction product from the first esterification reactor was continuously removed from the system and fed to the second esterification reactor. EG retained from the first esterification reactor was supplied to the second esterification reactor at a mass ratio of 8% relative to the generated PET. Further, an EG solution containing 65 ppm of magnesium acetate tetrahydrate relative to the generated PET and an EG solution containing 40 ppm of TMPA (trimethyl phosphate) relative to the generated PET were added. The reaction was carried out at atmospheric pressure with an average residence time of 1 hour and at 260°C. Next, the reaction product from the second esterification reactor was continuously removed from the system and fed to the third esterification reactor, while a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) was used at 39 MPa (400 kg / cm²). 2 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm, which underwent an average of 5 dispersion treatments under pressure, and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm and an ammonium salt of polyacrylic acid attached to 1% of the unit calcium carbonate, were added as 10% EG slurry. The reaction was carried out at atmospheric pressure with an average residence time of 0.5 hours and 260°C. The esterification reaction product generated in the third esterification reactor was continuously fed to a three-stage continuous polycondensation reactor for polycondensation. After filtration through a filter with 95% sintered stainless steel fibers with a cut particle size of 20 μm, the product was ultrafiltered, extruded into water, cooled, and cut into small flakes to obtain PET flakes with an intrinsic viscosity of 0.60 dl / g (hereinafter referred to as PET(I)). The lubricant content in the PET flakes was 0.6% by mass.

[0187] (Preparation of polyethylene terephthalate granules (PET(II)))

[0188] On the other hand, in the manufacturing of the above-mentioned PET flakes, PET flakes with an intrinsic viscosity of 0.62 dl / g that are completely free of particles such as calcium carbonate and silica are obtained (hereafter referred to as PET(II)).

[0189] (Preparation of polyethylene terephthalate (PET(III)) pellets)

[0190] The type and content of PET(I) particles were changed to 0.75% by mass of synthetic calcium carbonate with an average particle size of 0.9 μm relative to 1% by mass of ammonium salt of polyacrylic acid attached to each unit of calcium carbonate. Otherwise, PET flakes (hereinafter referred to as PET(III)) were obtained in the same manner as PET(I). The lubricant content in the PET flakes was 0.75% by mass.

[0191] (Manufacturing of substrate film X1)

[0192] After drying, these PET flakes are melted at 285°C and then melted again at 290°C in another melt extruder. They undergo two-stage filtration: a filter containing 95% sintered stainless steel fibers with a cut particle size of 15 μm and a filter containing 95% sintered stainless steel particles with a cut particle size of 15 μm. The fibers are then combined in the feed head and laminated with PET(I) as surface layer B and PET(II) as surface layer A. The laminate is extruded (cast) into a sheet at a rate of 45 m / min. Electrostatic sealing / cooling is then performed on a casting drum at 30°C to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio is adjusted to PET(I) / PET(II) = 60% / 40% based on the discharge rate of each extruder. Next, the unstretched sheet is heated in an infrared heater and then stretched longitudinally by 3.5 times at a roller temperature of 80°C according to the speed difference between the rollers. The film is then fed into a tenter frame and stretched 4.2 times in the transverse direction at 140°C. Next, it undergoes heat treatment at 210°C in a heat-setting zone. Following this, it is relaxed by 2.3% in the transverse direction at 170°C to obtain a substrate film X1 with a thickness of 25 μm, consisting of a biaxially stretched polyethylene terephthalate film. The surface layer A of the obtained substrate film X1 has a Sa value of 2 nm, and the surface layer B has a Sa value of 29 nm.

[0193] (Manufacturing of substrate film X2 with release layer)

[0194] On the surface layer A of the substrate film X1 obtained above, the following release coating liquid Y1 is coated by reverse gravure coating method with a wet film thickness of 5 μm. The film is then dried / cured in a hot air drying oven at 120°C for 30 seconds to obtain the substrate film X2 with a release layer. The surface Sa of the release layer is 2 nm.

[0195] (Mold release coating liquid Y1)

[0196] 48 parts by weight of toluene

[0197] 48 parts by weight of methyl ethyl ketone

[0198] Organosilicon resin composition (1)

[0199] (Thermosetting silicone coating, Si-H / Si-Vy = 3.0, solid content 30% by mass)

[0200] 3 parts by weight

[0201] SRX212P Catalyst (Pt-based solidified catalyst manufactured by Dow Toray Co., Ltd.)

[0202] 0.1 parts by weight

[0203] (Manufacturing of substrate film X3 with release layer)

[0204] Without changing the layer composition and stretching conditions of the substrate film X1, the casting speed was changed to adjust the thickness, thus producing a 12μm thick biaxially stretched polyethylene terephthalate film. A release layer identical to that of X2 was then applied to obtain the substrate film X3. The surface layer A of the resulting film X3 has a Sa value of 3nm, and the surface layer B has a Sa value of 29nm.

[0205] (Manufacturing method of substrate film X4 with release layer)

[0206] As the substrate film X4, a release layer similar to X2 is provided on the surface layer A of an A4100 (Cosmoshine (registered trademark), manufactured by Toyobo Co., Ltd.) with a thickness of 25 μm. The A4100 is configured such that it substantially does not contain particles, except that a coating layer containing particles is provided on the surface layer B side by in-line coating. The surface layer A of the substrate film X4 has a thickness Sa of 1 nm, and the surface layer B has a thickness Sa of 2 nm.

[0207] (Manufacturing method of substrate film X5 with release layer)

[0208] As the substrate film X5, a release layer similar to X2 is provided on surface layer A of E5101 (TOYOBO ESTER (registered trademark) film, manufactured by Toyobo Co., Ltd.) with a thickness of 25 μm. E5101 has a composition containing particles in surface layers A and B of the film. The Sa of surface layer A and surface layer B of the substrate film X5 is 25 nm.

[0209] (Manufacturing method of substrate film X6 with release layer)

[0210] On the surface layer A of the substrate film X1, a release coating liquid Y2 is applied using a reverse gravure coating method with a wet film thickness of 5 μm. The film is then dried / cured in a hot air drying oven at 120°C for 30 seconds to obtain a substrate film X6 with a release layer. The surface Sa of the release layer is 2 nm.

[0211] (Mold release coating liquid Y2)

[0212] 48 parts by weight of toluene

[0213] 48 parts by weight of methyl ethyl ketone

[0214] Organosilicon resin composition (2)

[0215] (Thermosetting silicone coating, Si-H / Si-Vy = 1.0, solid content 30% by mass)

[0216] 3 parts by weight

[0217] SRX212P Catalyst (Pt-based solidified catalyst manufactured by Dow Toray Co., Ltd.)

[0218] 0.1 parts by weight

[0219] (Manufacturing method of substrate film X7 with release layer)

[0220] On the surface layer A of the substrate film X1, a release coating liquid Y3 is applied using a reverse gravure coating method with a wet film thickness of 5 μm. The film is then dried / cured in a hot air drying oven at 120°C for 30 seconds to obtain a substrate film X7 with a release layer. The surface Sa of the release layer is 2 nm.

[0221] (Y3 release coating liquid)

[0222] 48 parts by weight of toluene

[0223] 48 parts by weight of methyl ethyl ketone

[0224] Organosilicon resin composition (3)

[0225] (Thermosetting silicone coating, Si-H / Si-Vy = 2.2, solid content 30% by mass)

[0226] 3 parts by weight

[0227] SRX212P Catalyst (Pt-based solidified catalyst manufactured by Dow Toray Co., Ltd.)

[0228] 0.1 parts by weight

[0229] (Example 1)

[0230] On the surface layer A of the substrate film X2, resin solution Z1 is coated using a reverse gravure coating method to achieve a film thickness of 3 μm after drying. The film is then dried in a hot air drying oven at 120°C for 10 seconds to form the resin sheet and create a laminated film. (The time from coating to entering the drying oven is 2 seconds). Details are shown in Tables 1 and 2.

[0231] (Resin Solution Z1)

[0232] 41.3 parts by weight of methyl ethyl ketone

[0233] 22.5 parts by weight of tetrahydrofuran

[0234] PKHB solution (40% by weight of solids) 30.6 parts by weight

[0235] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0236] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0237] Millionate MR-200 5.3 parts by weight

[0238] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solid content 99% by mass)

[0239] BYK-370 0.4 parts by weight

[0240] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0241] (Examples 2-3)

[0242] The substrate film was changed to that described in Table 1, but otherwise the laminated film was prepared in the same manner as in Example 1.

[0243] (Example 4)

[0244] The resin component (A) was changed to a resin solution Z6 with a different weight-average molecular weight (Mw). Otherwise, a laminated film was prepared in the same manner as in Example 1.

[0245] (Resin Solution Z6)

[0246] 41.3 parts by weight of methyl ethyl ketone

[0247] 22.5 parts by weight of tetrahydrofuran

[0248] PKHJ solution (40% by weight of solids) 30.6 parts by weight

[0249] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw57000)

[0250] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0251] Millionate MR-200 5.3 parts by weight

[0252] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solid content 99% by mass)

[0253] BYK-370 0.4 parts by weight

[0254] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0255] (Example 5)

[0256] The type of crosslinking agent was changed, and therefore, resin solution Z2 was used instead. Otherwise, the laminated film was prepared in the same manner as in Example 1.

[0257] (Resin solution Z2)

[0258] 41.3 parts by weight of methyl ethyl ketone

[0259] 22.5 parts by weight of tetrahydrofuran

[0260] PKHB solution (40% by weight, solid content) 30.6 parts by weight

[0261] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0262] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0263] Millionate MR-400 5.3 parts by weight

[0264] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 600 mPa·s, solid content 99% by mass)

[0265] BYK-370 0.4 parts by weight

[0266] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0267] (Example 6)

[0268] The type of crosslinking agent was changed, and therefore, resin solution Z3 was used instead. Otherwise, the laminated film was prepared in the same manner as in Example 1.

[0269] (Resin Solution Z3)

[0270] 41.3 parts by weight of methyl ethyl ketone

[0271] 22.5 parts by weight of tetrahydrofuran

[0272] PKHB solution (40% by weight, solid content) 30.6 parts by weight

[0273] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0274] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0275] Millionate MTL 5.3 parts by weight

[0276] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 50 mPa·s, solid content 99% by mass)

[0277] BYK-370 0.4 parts by weight

[0278] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0279] (Example 7)

[0280] The ratio of resin to crosslinking agent was changed, and therefore, resin solution Z4 was changed. Otherwise, the laminated film was prepared in the same manner as in Example 1.

[0281] (Resin Solution Z4)

[0282] 41.3 parts by weight of methyl ethyl ketone

[0283] 19.9 parts by weight of tetrahydrofuran

[0284] PKHB solution (40% by weight, solid content) 35.0 parts by weight

[0285] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0286] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0287] Millionate MR-200 3.5 parts by weight

[0288] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solid content 99% by mass)

[0289] BYK-370 0.4 parts by weight

[0290] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0291] (Example 8)

[0292] The ratio of resin to crosslinking agent was changed, so the resin solution was changed to Z5. Otherwise, the laminated film was prepared in the same manner as in Example 1.

[0293] (Resin Solution Z5)

[0294] 41.3 parts by weight of methyl ethyl ketone

[0295] 17.3 parts by weight of tetrahydrofuran

[0296] PKHB solution (40% by weight, solid content) 39.4 parts by weight

[0297] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0298] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0299] Millionate MR-200 1.8 parts by weight

[0300] (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solid content 99% by mass)

[0301] BYK-370 0.4 parts by weight

[0302] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0303] (Examples 9-11)

[0304] The substrate film was changed to the one described in Table 1, except that the laminated film was made in the same manner as in Example 1.

[0305] (Examples 12-13)

[0306] The drying temperature of the resin sheet was changed to the temperature recorded in Table 1, and otherwise the laminated film was prepared in the same manner as in Example 1.

[0307] (Comparative Example 1)

[0308] The substrate film was changed to X1 without a release layer, but otherwise, a laminated film was made in the same manner as in Example 1.

[0309] (Comparative Example 2)

[0310] The resin solution was changed to a resin solution Z6 without crosslinking agent, but otherwise, a laminated film was prepared in the same manner as in Example 1.

[0311] (Resin Solution Z6)

[0312] 41.3 parts by weight of methyl ethyl ketone

[0313] 14.7 parts by weight of tetrahydrofuran

[0314] PKHB solution (40% by weight of solids) 43.8 parts by weight

[0315] (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000)

[0316] *The solution is prepared by dissolving phenoxy resin in tetrahydrofuran.

[0317] BYK-370 0.4 parts by weight

[0318] (Manufactured by BYK Japan Co., Ltd., silicone-based surfactant)

[0319] (Comparative Example 3)

[0320] The resin sheet is formed such that the maximum cross-sectional height (St) of the surface (1) of the resin sheet is 75 nm. Otherwise, a laminated film is formed in the same manner as in Example 1.

[0321] (Refer to Example 4)

[0322] The drying conditions for the resin sheet were changed to 140°C for 60 seconds, but otherwise, a laminated film was prepared in the same manner as in Example 1. By extending the drying time, the precipitation of the crosslinking agent on the surface increased, resulting in a rougher surface and a greater difference in the indentation modulus between the surface and the interior of the resin sheet.

[0323] For the substrate films used in each embodiment, after processing the release layer, they were cured at 40°C for 3 days before use. Additionally, the resulting laminated films were also evaluated after curing at 40°C for 3 days.

[0324] [Table 1]

[0325]

[0326] [Table 2]

[0327]

[0328] The laminated sheets of the present invention obtained in the embodiments can provide, for example, resin sheets that improve transparency in optical applications, and also resin sheets exhibiting high smoothness. Furthermore, both high smoothness and high slip properties can be achieved, for example, by suppressing scratches introduced during transport processes, thus avoiding a decrease in yield.

[0329] Furthermore, in electronic component applications such as film capacitors, resin sheets exhibiting high smoothness can be provided, which improves electrical characteristics such as dielectric breakdown voltage. Moreover, both high smoothness and high slip properties can be achieved; for example, misalignment and wrinkling during winding the dielectric resin sheet onto the roller can be suppressed, resulting in excellent winding performance. Therefore, it is possible to transport the capacitor while maintaining excellent capacitor performance.

[0330] Furthermore, the resin sheet obtained in this invention is substantially free of particles, thus avoiding insufficient transparency due to increased internal haze. Additionally, it avoids the problem of uneven particle distribution on the resin sheet, resulting in good slip properties.

[0331] In contrast, Comparative Example 1 lacks the release layer of the present invention; therefore, the release properties of the resin sheet are extremely poor, making it impossible to evaluate the resin sheet. In Comparative Example 2, the resin sheet forming composition does not contain a crosslinking agent; therefore, in particular, it shows a decrease in the sliding properties of the resin sheet.

[0332] In Comparative Example 3, the maximum cross-sectional height (St) of the surface (1) of the resin sheet is not within the scope of the present invention, thus showing, in particular, the result of poor sliding properties of the resin sheet.

[0333] Industrial availability

[0334] This invention relates to laminated films containing resin sheets. In particular, it relates to laminated films containing resin sheets used in electronic components and optical applications.

[0335] Explanation of reference numerals in the attached figures

[0336] 10. Substrate film

[0337] 11. Release layer

[0338] 12 resin sheets

[0339] 13. Surface of the resin sheet (1)

[0340] 14. Surface of the resin sheet (2)

Claims

1. A laminated film comprising: a polyester-based substrate film, a release layer disposed on at least one side of the substrate film, and a resin sheet disposed on the release layer on the side opposite to the substrate. The laminated film satisfies the following (1) to (7): (1) The resin sheet is obtained by curing a resin sheet forming composition containing at least resin component (A) and crosslinking agent (B), wherein the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C. (2) The resin sheets do not actually contain particles. (3) The film thickness (t1) of the resin sheet is greater than 1 μm and less than 20 μm. (4) The indentation modulus (E1) of the resin sheet surface (1) is 2.0 MPa or higher. (5) The indentation modulus (E2) of the resin sheet surface (2) is above 2.0 MPa. (6) The absolute value of the difference between E1 and E2 is less than 1.

5. (7) The static friction coefficient measured by overlapping the surface (1) of the resin sheet opposite to the release layer with the surface (2) of the resin sheet on the release layer side is 1.5 or less.

2. The laminated film according to claim 1, characterized in that, The arithmetic mean height (Sa) of the surface (1) of the resin sheet is above 2 nm and below 30 nm.

3. The laminated film according to claim 1, characterized in that, The maximum cross-sectional height (St) of the surface (1) of the resin sheet is above 80 nm and below 1000 nm.

4. The laminated film according to claim 1, characterized in that, The crosslinking agent (B) contained in the resin sheet accounts for more than 10% by mass in the whole resin sheet.

5. The laminated film according to claim 1, characterized in that, The weight-average molecular weight of the resin component (A) contained in the resin tablet is above 10,000.

6. The laminated film according to claim 1, characterized in that, The surface free energy of the release layer is 40 mJ / m 2 The following, and the adhesion energy is 3.5 mJ / m 2 above.

7. The laminated film according to claim 1, characterized in that, The arithmetic mean height (Sa) of the release layer side surface of the substrate film is less than 20 nm, and the maximum protrusion height (P) is less than 500 nm.

8. A method for manufacturing a laminated thin film, characterized in that, It is a method for manufacturing a laminated film according to any one of claims 1 to 7, wherein the manufacturing method involves coating a resin sheet onto a substrate film using a solution film-forming method.

9. A resin sheet that satisfies the following: (1) The resin sheet is obtained by curing a resin sheet forming composition containing at least resin component (A) and crosslinking agent (B), wherein the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C. (2) The resin sheets do not actually contain particles. (3) The film thickness (t1) of the resin sheet is greater than 1 μm and less than 20 μm. (4) The indentation modulus (E1) of the resin sheet surface (1) is 2.0 MPa or higher. (5) The indentation modulus (E2) of the resin sheet surface (2) is above 2.0 MPa. (6) The absolute value of the difference between E1 and E2 is less than 1.

5. (7) The static friction coefficient measured by overlapping one surface (1) of the resin sheet with the surface (2) of the resin sheet opposite to the surface (1) is 1.5 or less.

10. The resin sheet according to claim 9, wherein, The resin sheet is a sheet peeled from a release film having a substrate and a release layer, wherein the surface free energy of the release layer is 40 mJ / m. 2 The following, and the adhesion energy is 3.5 mJ / m 2 above.

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