Release sheet for metal film transfer

Abstract

To provide a release sheet for metal film transfer or the like that is superior in peelability of the metal film and its long-term stability even after the metal film is deposited.SOLUTION: A release sheet for metal film transfer 100 comprises at least a substrate film 11 and a release layer 31 with an adhesion face 31a. After providing a metal film M on the adhesion face 31a of the release layer 31, the metal film M is peeled and transferred from the adhesion face 31a onto a transfer object S. A free metal ion trapping layer 21 is further provided between the substrate film 11 and the release layer 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a release sheet for metal film transfer and the like.

Background Art

[0002] The demand for lithium-ion secondary batteries has been rapidly expanding in portable information terminals such as mobile phones, smartphones, and notebook personal computers, electronic devices such as portable music players and digital cameras, medical devices, next-generation clean energy vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), and electric vehicles (EV). However, recently, lithium-ion secondary batteries with higher capacity and higher output have been desired, and improving their energy density has become an urgent issue.

[0003] In order to increase the energy density of lithium-ion secondary batteries, the use of a metal lithium electrode as a negative electrode material having characteristics of a relatively low redox potential and a relatively large energy density has been studied. Conventionally, as a method for manufacturing a metal lithium negative electrode, although vapor deposition of a lithium layer on a current collector or transfer of a lithium foil on a current collector has been studied, since lithium metal is a metal with high reactivity and difficult to handle, in recent years, manufacturing by a transfer method has been studied.

[0004] Patent Document 1 discloses a transfer film including a substrate and a release layer formed on the substrate. Further, after forming an auxiliary layer of copper, aluminum, nickel, etc., which has a lower reactivity with respect to the release layer than lithium, on the release layer of this transfer film, a metal lithium film is vapor-deposited on the auxiliary layer and on the portion of the release layer where the auxiliary layer is not formed, and a manufacturing method for peeling and transferring the auxiliary layer and the metal lithium film from the release layer of this transfer film onto a current collector is disclosed.

[0005] Patent Document 2 discloses a transfer film comprising a synthetic resin base film and an inorganic release layer formed on the base film containing Li2CO3, LiF, LiCl, LiBr, Li3PO4, LiPON, etc. Furthermore, a manufacturing method is disclosed in which a metallic lithium film is formed on the inorganic release layer of the transfer film, and then the metallic lithium film is peeled off and transferred from the inorganic release layer of the transfer film onto a metal film. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-020974 [Patent Document 2] Japanese Patent Publication No. 2020-187975 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, it has been found that the transfer films described in the above-mentioned conventional Patent Documents 1 and 2 have poor peelability of the metal lithium film deposited on the transfer film, making it difficult to remove the metal lithium film from the transfer film over time, and thus making it difficult to obtain good transfer performance. Furthermore, the surface smoothness of the metal film to be peeled and transferred is poor, and considering its practical use as a metal lithium anode, improvement in the surface smoothness of the metal film is required from the viewpoint of shortening the lifespan due to dendrite generation.

[0008] The present invention has been made in view of the above problems. Specifically, the object of the present invention is to provide a release sheet for metal film transfer, etc., which has excellent peelability and stability over time even after a metal film has been formed on it. Another object of the present invention is to provide a release sheet for metal film transfer, etc., which not only has excellent peelability and stability over time, but also enables the peeling and transfer of a metal film with excellent surface smoothness. [Means for solving the problem]

[0009] The inventors diligently studied to solve the above problems. As a result, they found that the above problems could be solved by providing a free metal ion trap layer between the base film and the release layer, and thus completed the present invention.

[0010] In other words, the present invention provides various specific embodiments as shown below. [1] A release sheet for metal film transfer, comprising at least a base film and a release layer having an adhesion surface, wherein a metal film is provided on the adhesion surface of the release layer, and the metal film is then transferred and peeled off from the adhesion surface onto a transfer object, the release sheet further comprising a free metal ion trap layer between the base film and the release layer.

[0011] [2] The release sheet for metal film transfer according to [1], wherein the free metal ion trap layer is a vapor-deposited film.

[0012] [3] The free metal ion trap layer is a release sheet for metal film transfer according to [1] or [2], having a thickness of 0.1 to 500 nm.

[0013] [4] The release sheet for transferring metal films according to any one of items [1] to [3], wherein the metal film is a Li metal film or a Li alloy film.

[0014] [5] A release sheet for transferring a metal film according to any one of items [1] to [4], wherein the metal film is a vapor-deposited film.

[0015] [6] A release sheet for transferring a metal film according to any one of [1] to [5], wherein the metal film is a metallic lithium electrode.

[0016] [7] A release sheet for transferring a metal film according to any one of items [1] to [6], wherein the metal film is the negative electrode of a lithium secondary battery.

[0017] 〔8〕The base film is one selected from the group consisting of a polyethylene terephthalate film, a polybutylene terephthalate film, and a polyethylene naphthalate film, and is the release sheet for metal film transfer according to any one of 〔1〕~〔7〕.

[0018] 〔9〕The base film further includes a matte layer on the surface opposite to the release layer, and has the matte layer, the base film, the free metal ion trap layer, and the release layer in this order, and is the release sheet for metal film transfer according to any one of 〔1〕~〔8〕.

[0019] 〔10〕The release layer contains a fluororesin layer and / or a fluorine-modified resin, and is the release sheet for metal film transfer according to any one of 〔1〕~〔9〕.

[0020] 〔11〕The release layer has a thickness of 10 to 400 nm, and is the release sheet for metal film transfer according to any one of 〔1〕~〔10〕.

[0021] 〔12〕The oxygen permeability of the free metal ion trap layer (in accordance with JIS K-7126, 25 °C, 80% RH) is 60 ml / m 2 / day / MPa or less, and is the release sheet for metal film transfer according to any one of 〔1〕~〔11〕.

[0022] 〔13〕A release sheet for metal film transfer comprising at least a base film, a free metal ion trap layer, a release layer having an adherent surface, and a metal film formed on the adherent surface, in this order.

Advantages of the Invention

[0023] According to the present invention, even when a metal film is formed, it is an object to realize a release sheet for metal film transfer or the like that is excellent in the peelability of the metal film and its stability over time. Further, according to a preferred embodiment of the present invention, not only is the peelability of the metal film and its stability over time excellent, but it is also possible to realize a release sheet for metal film transfer or the like that can peel and transfer a metal film excellent in surface smoothness. And, in the formation of the metal film, relatively large man-hours and time are required such as in the vapor deposition method or the sputtering method. According to the present invention, even when stored in a state where the metal film is formed on the adherent surface of the release layer, the peelability of the metal film is kept good, so that it can be stored for a relatively long period of time in the state after the formation of the metal film. As a result, it is also possible to improve the efficiency of supply chain management and the like.

Brief Description of Drawings

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a release sheet 100 for metal film transfer. [Figure 2] FIG. 2 is a table comparing the peel transfer performance of Examples 1-5. [Figure 3] FIG. 3 is a schematic flow showing an example of the usage method of the release sheet 100 for metal film transfer.

Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Also, the dimensional ratios in the drawings are not limited to the illustrated ratios. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited thereto. In this specification, for example, the numerical range notation of "1 to 100" includes both the lower limit value "1" and the upper limit value "100". The same applies to the notation of other numerical ranges.

[0026] <Release Sheet for Metal Film Transfer> Figure 1 is a schematic cross-sectional view showing the general configuration of a release sheet 100 for metal film transfer according to one embodiment of the present invention. The release sheet 100 for metal film transfer in this embodiment comprises at least a base film 11, a free metal ion trap layer 21 provided on the surface 11a side of the base film 11, and a release layer 31 provided on one surface 21a side of the free metal ion trap layer 21. In this embodiment, a mat layer 41 is provided on the surface 11b side of the base film 11 opposite to the surface 11a. The surface of the release layer 31 that is exposed upward is the adherend surface 31a on which the metal film M is provided. After providing the metal film M on this adherend surface 31a, the release sheet 100 for metal film transfer functions as a release transfer material that transfers and peels the metal film M (transfer material) from the adherend surface 31a onto the transfer target S.

[0027] The release sheet 100 for metal film transfer in this embodiment has a laminated structure (4-layer structure) in which a base film 11, a free metal ion trap layer 21, and a release layer 31 are arranged in at least this order, and a mat layer 41 is provided on the surface of the base film 11 opposite to the release layer 31. In this laminated structure, the release layer 31 is located on the outermost surface of the front side of the release sheet 100 for metal film transfer, and is positioned in an exposed state on the outermost surface of the release sheet 100 for metal film transfer. The surface of the release layer 31 on the adherend side 31a may be provided with any layer, such as a protective layer that can be peeled off during use, as needed. In addition, the surfaces of the base film 11 and the free metal ion trap layer 21 may be subjected to any surface treatment, such as antistatic treatment or primer treatment, as needed.

[0028] In this specification, "provided on one (or the other) side of ~" means not only the configuration in which the free metal ion trap layer 21 is directly placed on the surface 11a of the base film 11 and the release layer 31 is directly placed on the surface 21a of the free metal ion trap layer 21, as in this embodiment, but also configurations in which any layer (e.g., a primer layer, adhesive layer, etc.) not shown is interposed between the surface 11a of the base film 11 and the free metal ion trap layer 21, or between the surface 21a of the free metal ion trap layer 21 and the release layer 31, so that the base film 11, the free metal ion trap layer 21, and the release layer 31 are spaced apart. In other words, any layer such as an antistatic layer, a primer layer, or a protective layer may be provided between the base film 11 and the free metal ion trap layer 21 as needed. Furthermore, a laminated structure comprising at least the base film 11, the free metal ion trap layer 21, and the release layer 31 means a structure in which any of the above-mentioned arbitrary layers are further provided between the layers of these three layers. The following describes each configuration in detail.

[0029] (Base film) The base film 11 supports the free metal ion trap layer 21 and the release layer 31. The constituent material of the base film 11 is not particularly limited as long as it can support the free metal ion trap layer 21 and the release layer 31. From the viewpoint of dimensional stability, mechanical strength, and weight reduction, thermoplastic or thermosetting synthetic resin films are preferably used, and thermoplastic resin films are more preferably used. Specific examples include, but are not particularly limited to, polyester films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, ABS (acrylonitrile-butadiene-styrene) film, polyimide film, polyamide film, polyamide-imide film, polystyrene film, polycarbonate film, and polyvinyl chloride film. These can be used individually or in any combination and ratio of two or more. Laminated films using these in any combination can also be suitably used. In this specification, "(meth)acrylic" is a concept that includes both acrylic and methacrylic. Among these, from the viewpoint of heat resistance and dimensional stability, polyester film, polyimide film, polycarbonate film, (meth)acrylic film, and laminated films using any combination thereof are preferred as the base film 11, and more preferably polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN).

[0030] The base film 11 described above may be an unoriented film or an oriented film, but from the viewpoint of mechanical properties and surface smoothness, a uniaxially oriented film or a biaxially oriented film is preferred, and a biaxially oriented film is more preferred. Furthermore, from the viewpoint of heat resistance during film formation of the free metal ion trap layer 21, the glass transition temperature of the resin of the base film 11 is preferably 50 to 300°C, more preferably 55 to 250°C, and even more preferably 60 to 200°C.

[0031] The appearance of the base film 11 may be transparent, translucent, colorless, or colored, and is not particularly limited, but a high light transmittance is preferred. Specifically, a transparent resin film with a total light transmittance Tt (according to JIS K7361-1) of 80% or more when light is incident perpendicularly from the thickness direction of the base film 11, i.e., at an incident angle of 0°, is preferred, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 92% or more. In this specification, the total light transmittance Tt refers to the value measured with a haze meter (for example, NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.)).

[0032] The thickness of the base film 11 can be set appropriately according to the required performance and application, and is not particularly limited. From the viewpoint of weight reduction and thinning, the thickness of the base film 11 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and particularly preferably 7 μm or more, with the upper limit preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 120 μm or less. Furthermore, from the viewpoint of improving adhesion with the free metal ion trap layer 21 and the mat layer 41, various known surface treatments such as anchoring treatment and corona treatment can be applied to the surface 11a and surface 11b of the base film 11 as needed. Also, from the same viewpoint, the base film 11 may be a base film having an easy-adhesion layer on its surface.

[0033] (Free metal ion trap layer) The free metal ion trap layer 21 is a layer provided on the surface 11a side of the base film 11. In this embodiment, the free metal ion trap layer 21 is a thin film made of a metal oxide or an inorganic oxide. By providing the free metal ion trap layer 21, the decrease in the peelability of the release layer 31 can be suppressed, and the time-dependent stability of the peelability of the release layer 31 can be improved. The material used to form the free metal ion trap layer 21 is not particularly limited as long as it can trap free metal ions and be made into a thin film. For example, transition metals, typical metals, typical nonmetals, etc., represented by element symbols such as Si, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, and Sn can be used. These may be used individually or as oxides. Among these, oxides such as Si and Al are preferred from the viewpoint of free metal ion trapping ability and thin film density, and silicon dioxide (silica), aluminum oxide (alumina), and composite oxides of silicon dioxide and aluminum oxide (silica-alumina) are preferred, with silicon dioxide (silica) being more preferred. In this context, silicon oxide refers to various silicon oxides such as SiO and SiO2, or mixtures thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al2O3, or mixtures thereof. When the metal film M is an alkali metal such as metallic Li, silicon oxide or aluminum oxide, which have excellent trapping properties for free alkali metals, are particularly preferred.

[0034] The free metal ion trap layer 21 is preferably a deposited film of the metal oxide or inorganic oxide described above, from the viewpoint of trapping free metal ions and the density of the thin film. The deposited film referred to here means, for example, a vacuum deposited film formed by vacuum deposition, a PVD film formed by PVD (physical vapor deposition) methods such as sputtering, or a CVD film formed by CVD (chemical vapor deposition) methods such as ion plating or plasma vapor deposition. From the viewpoint of productivity and stability, the free metal ion trap layer 21 is more preferably a vacuum deposited film. These deposition methods can be carried out by methods known in the industry, for example, Al, Al2O3, SiO2, etc. can be used as the deposition source material, resistance heating, high-frequency induction heating, electron beam heating, etc. can be used as the heating method, oxygen, nitrogen, water vapor, etc. can be used as the reactive gas, and reactive deposition can be carried out using means such as ozone addition or ion assistance.

[0035] The free metal ion trap layer 21 has an oxygen permeability of 60 ml / m³ (according to JIS K-7126, 25°C, 80%RH) as measured using an oxygen permeability measuring device. 2 Preferably less than / day / MPa, and more preferably 50 ml / m 2 Less than / day / MPa, more preferably 40 ml / m² 2 The pressure is less than / day / MPa. By using a free metal ion trap layer 21 with such high gas barrier properties, the decrease in the release properties of the release layer 31 can be further suppressed, and the time-dependent stability of the release properties of the release layer 31 can be further improved.

[0036] Furthermore, the thickness (average film thickness) of the free metal ion trap layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 0.1 to 500 nm, more preferably 1.0 to 150 nm, and even more preferably 5.0 to 70 nm. When the thickness of the free metal ion trap layer 21 is within the above preferred numerical range, the trapping ability of free metal ions and surface smoothness tend to improve, and the peeling and transferability of the metal film M of the release layer 31 tends to be enhanced.

[0037] By providing the free metal ion trap layer 21, the decrease in the peelability of the release layer 31 can be suppressed, and the time-dependent stability of the peelability of the release layer 31 can be improved. Specifically, as shown in Figure 2, compared to Example 1, which does not have the free metal ion trap layer 21, Examples 2-5, which have the free metal ion trap layer 21, exhibit superior peel transfer performance of the metal film M, and the time-dependent deterioration of the peel transfer performance of the metal film M is suppressed. In this example, Example 1 is a PET film with a thickness of 12 μm as the base film 11, on which a fluororesin coating layer with an average thickness of approximately 200 nm is provided as the release layer 31. Example 2 involves providing a silicon oxide coating layer with an average thickness of approximately 40 nm as a free metal ion trap layer 21 on a PET film with a thickness of 12 μm as the base film 11, and further providing a fluororesin coating layer with an average thickness of approximately 200 nm as a release layer 31 on the free metal ion trap layer 21. Example 3 involves providing a PET film with a thickness of 12 μm as the base film 11, a coating layer of aluminum oxide with an average thickness of approximately 40 nm as the free metal ion trap layer 21, and further providing a fluororesin coating layer with an average thickness of approximately 200 nm as the release layer 31 on top of the free metal ion trap layer 21. Example 4 involves providing a PET film with a thickness of 12 μm as the base film 11, a vacuum-deposited film of silicon dioxide with an average thickness of approximately 40 nm as the free metal ion trap layer 21, and further providing a fluororesin coating layer with an average thickness of approximately 200 nm as the release layer 31 on top of the free metal ion trap layer 21. Example 5 involves a PET film with a thickness of 12 μm as the base film 11, on which a vacuum-deposited film of aluminum oxide with an average thickness of approximately 40 nm is provided as the free metal ion trap layer 21, and further on which a fluororesin coating layer with an average thickness of approximately 200 nm is provided as the release layer 31. Here, we relatively evaluate the peel-and-transfer performance after 24 hours when a vapor-deposited film of metallic Li with a thickness of approximately 10 μm is formed as a metal film M on the adherend surface 31a of the upper surface of the release layer 31 in Examples 1-5, and the peel-and-transfer performance after further storage at 23°C in an extremely dry state for 5 days after the 24 hours have elapsed. The reason for these effects is not entirely clear, but it is presumed that by providing the free metal ion trap layer 21, the release of metal ions and mass transfer from the metal film M to the release layer 31 and the base film 11 are inhibited, and as a result, excessive changes in the physical properties of the base film 11 and the release layer 31 are suppressed.

[0038] (Release layer) The release layer 31 is a layer provided on the surface 21a side of the free metal ion trap layer 21. The release layer 31 is located on the outermost surface side of the release sheet 100 for metal film transfer in this embodiment, and peels off and transfers the metal film M provided on its adhesion surface 31a onto the transfer target S. In addition, a peelable protective layer may be provided in front of the adhesion surface 31a of the release sheet 100 for metal film transfer in this embodiment for the purpose of protecting the adhesion surface 31a before use. In this case, when using the sheet, the protective layer is peeled off to expose the adhesion surface 31a, and then the release sheet 100 for metal film transfer in this embodiment is used for peeling off and transferring the metal film M.

[0039] The type of material used to make up the release layer 31 is not particularly limited, as long as it can peel off and transfer the metal film M onto the transfer target S. For example, if a silicone resin is used as the release layer 31, the alkali metal film M tends to be difficult to peel off, and good peel-off transferability is not obtained. Therefore, it is preferable that the release layer 31 does not contain silicone resin. Specific examples of materials used to make up the release layer 31 include, but are not particularly limited to, fluororesins, fluoro-modified resins, melamine resins, amino alkyd resins, epoxy resins, epoxy-melamine resins, acrylic resins, cellulose resins, urea resins, polyolefin resins, cycloolefin resins, paraffins, rubber-based elastomers, etc. These can be used individually or in any combination and ratio of two or more. Among these, fluororesins, fluoro-modified resins, and melamine resins are preferred from the viewpoint of surface smoothness, residue generation due to cohesive breakdown, peel-off transferability, and stability over time, and fluororesins and / or fluoro-modified resins are more preferred. Note that fluororesins and fluorine-modified resins refer to resins that contain fluorine atoms in their molecules (fluororesins). Preferred fluororesins and / or fluorine-modified resins include, but are not limited to, polytetrafluoroethylene (PTFE), perfluoroalkoxyalkanes (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-perfluorodioxole copolymer (TFE / PDD), polyvinyl fluoride (PVF), and copolymers containing these as copolymer components. In addition to the mold-releasing resin described above, the release layer 31 may also contain various additives known in the industry, as long as they do not excessively inhibit the effects of the present invention. Examples of such additives include, but are not limited to, surface modifiers, lubricants, fluorescent whitening agents, flame retardants, antibacterial agents, antifungal agents, ultraviolet absorbers, light stabilizers, heat stabilizers, antioxidants, plasticizers, leveling agents, flow regulators, defoaming agents, surfactants, dispersants, storage stabilizers, crosslinking agents, and silane coupling agents. Furthermore, the material may contain curing catalysts such as aluminum-based catalysts, tin-based catalysts, titanium-based catalysts, and zirconia-based catalysts, curing aids, crosslinking agents such as isocyanate compounds, and catalysts such as tin-based catalysts and aluminum-based catalysts. The proportion of these is not particularly limited, but it is generally preferable that each is 0.01 to 5% by mass in terms of solid content relative to the total resin components contained in the molded diffusion layer 21.

[0040] The thickness (average film thickness) of the release layer 31 can be set appropriately according to the desired performance and is not particularly limited, but is preferably 10 to 400 nm, more preferably 30 to 350 nm, and even more preferably 50 to 300 nm. When the thickness of the release layer 31 is within the above preferred numerical range, good surface smoothness, peel transferability, and stability over time tend to be easily obtained, and the generation of residue due to cohesive failure tends to be suppressed.

[0041] (Matte layer) The mat layer 41 is a surface irregularity layer provided as needed on the surface 11b side of the base film 11. By providing the mat layer 41, it is possible to adjust, for example, the slipperiness during transport of the release sheet 100 for metal film transfer and the adhesion during winding of the release sheet 100 for metal film transfer, thereby increasing productivity. The constituent material of the mat layer 41 can be any material known in the industry and is not particularly limited. Examples include vinyl resin, vinyl acetal resin, polyester, polyamide, polyolefin, (meth)acrylic resin, polyolefin, polyurethane, cellulose resin, isocyanate resin, and phenolic resin, but is not particularly limited to these. These can be used individually or in any combination and ratio of two or more. Laminated films using these in any combination can also be suitably used.

[0042] The degree of surface roughness of the mat layer 41 is not particularly limited, but the arithmetic mean roughness (Ra) is preferably 0.5 to 2.5 μm, more preferably 0.5 to 2.5 μm, and even more preferably 0.5 to 2.5 μm. When the Ra of the mat layer 41 is within the above preferred numerical range, good transportability and adhesion tend to be easily obtained. The arithmetic mean roughness (Ra) can be determined using an atomic force microscope "Nanocute system" (product name, manufactured by Hitachi High-Tech Science Corporation, probe: Si single crystal probe, measurement mode: DFM mode, image processing: flattening (XY) once) in accordance with the measurement method in accordance with JIS B0601:2001.

[0043] The thickness (average film thickness) of the mat layer 41 can be set appropriately according to the desired performance and is not particularly limited, but is preferably 0.3 to 3.0 μm, more preferably 0.5 to 2.5 μm, and even more preferably 1.0 to 2.0 μm. When the thickness of the mat layer 41 is within the above preferred numerical range, good transportability tends to be easily obtained, and the adverse effects of transferring the surface irregularities to the release layer 31 when it is in roll form tend to be suppressed.

[0044] The release sheet 100 for metal film transfer in this embodiment may have other functional layers laminated on it in addition to the layers described above, as long as it has the functions of the present invention. Examples of such functional layers include, but are not limited to, an antistatic layer, an anti-blocking layer, a smooth-slip layer, a hard coat layer, an ultraviolet absorbing layer, an easy-adhesion layer, and an adhesive layer.

[0045] (How to use) Figure 3 is a schematic flow chart showing an example of how to use the metal film transfer release sheet 100 of this embodiment. In this embodiment, first, the metal film transfer release sheet 100 is prepared (step S1), and a metal film M is applied to the adhesion surface 31a located on the outermost surface of the metal film transfer release sheet 100 (step S2). The metal film transfer release sheet 100 with the metal film M applied is represented as metal film transfer release sheet 101. Then, the metal film M of the metal film transfer release sheet 101 is brought into close contact with the object to be transferred S (step S3), and heated as necessary. The metal film transfer release sheet 101, which is in close contact with the object to be transferred S and the metal film M, is represented as metal film transfer release sheet 102. After that, the metal film M is peeled off and transferred from the adhesion surface 31a of the metal film transfer release sheet 102 onto the object to be transferred S (step S4). Through this peeling transfer, a laminate of the metal film M and the object to be transferred S is obtained as the transfer product T.

[0046] Examples of metal films M used here include, but are not limited to, Al (aluminum), Zn (zinc), Cu (copper), Fe (iron), Ni (nickel), Cr (chromium), Mo (molybdenum), Au (gold), Ag (silver), and Cu (copper). The metal film M may be a single metal composed of one metal element, or an alloy containing at least one metal element. In this specification, the term "metal film M" encompasses not only a film of a single metal itself, but also a film of an alloy containing two or more metal elements.

[0047] The metal film M is preferably an alkali metal film, and more preferably a Li metal film or a Li alloy film. Alkali metal films tend to cause a decrease in the release properties of the release layer 31 and are prone to deterioration of release properties over time, so the effects of the present invention tend to be more apparent. Furthermore, there is a growing demand for Li metal films and Li alloy films as metallic lithium electrodes or lithium secondary battery negative electrodes, and by using this method, the productivity of metallic lithium electrodes can be increased, making it possible to provide high-quality metallic lithium electrodes at low cost. The Li metal film and Li alloy film may be metallic lithium, lithium alloy, oxide of a lithium alloy, or lithium oxide. As a non-limiting example, the lithium alloy may be an alloy of lithium with one or more metals selected from the group Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn. In this case, the metal film M may have a surface oxide film formed on it, may be partially altered by oxygen or moisture, or may contain impurities.

[0048] Furthermore, the method for forming the metal film M is not particularly limited and can be any known manufacturing method in the industry. For example, known thin-film formation techniques such as vacuum deposition, sputtering, ion plating, plasma vapor deposition, and atomic layer deposition can be used. From the viewpoint of productivity, cost, and surface smoothness of the resulting metal film M, it is preferable that the metal film M is a deposited film. The metal film M may be applied to the entire surface of the adherend 31a or to a portion of the adherend 31a in a patterned manner.

[0049] The thickness (average film thickness) of the metal film M can be set appropriately according to the desired performance and is not particularly limited, but may be 0.01 to 100 μm, more preferably 0.05 to 75 μm, and even more preferably 0.10 to 50 μm. When the thickness of the metal film M is within the above preferred numerical range, good peel-and-transfer properties tend to be easily obtained, and it tends to be easier to realize a high-energy-density metallic lithium electrode or a lithium secondary battery anode.

[0050] The transfer target S can be appropriately set according to the desired performance and is not particularly limited. As the transfer target S, for example, paper substrates such as fine paper, art paper, coated paper, resin coated paper, cast coated paper, cardboard, synthetic paper, and impregnated paper, or various resin films can be used. Alternatively, as mentioned in the above example, in the case of a Li metal film or Li alloy film used as a metallic lithium electrode or a lithium secondary battery anode, those used in current collectors in the relevant art are preferably used. In this case, as the transfer target S, for example, copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and composites consisting of combinations thereof can be used. The above stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and as the above alloy, an aluminum-cadmium alloy may be used. In addition, calcined carbon, non-conductive polymers surface-treated with conductive materials, conductive polymers, etc. can be used as the transfer target S.

[0051] As described in detail above, the metal film transfer release sheet 100 of this embodiment allows for good peeling of the metal film M from the adherend surface 31a of the release layer 31 even after the metal film M has been formed, and maintains good peelability of the metal film M over a long period of time. Furthermore, the metal film transfer release sheet 100 of this embodiment allows for the peeling and transfer of a metal film M with excellent surface smoothness, and residue from the release layer 31 is less likely to adhere to the smooth surface of the metal film M after the peeling and transfer of the metal film M. Moreover, the metal film transfer release sheet 100 (metal film transfer release sheet 101) with the metal film M attached, or the metal film transfer release sheet 101 (metal film transfer release sheet 102) in close contact with the transfer object S, can be stored for a long period of time, improving productivity and streamlining supply chain management. Therefore, the release sheets 100, 101, and 102 for metal film transfer in this embodiment are particularly useful as release sheets that offer high productivity, low cost, and high performance.

[0052] Furthermore, the present invention also provides the following various embodiments. [1] A step of preparing a release sheet for metal film transfer, comprising at least a base film, a free metal ion trap layer, and a release layer having an adhesion surface. A step of providing a metal film to the adhered surface of the release sheet for metal film transfer, The process of bringing the release sheet for metal film transfer into close contact with the metal film on the object to be transferred, and The process includes at least the step of peeling and transferring the metal film from the adherend surface of the release sheet for metal film transfer to the transfer body, A method for manufacturing a transfer metal film.

[0053] [2] A step of preparing a release sheet for metal film transfer, comprising at least a base film, a free metal ion trap layer, and a release layer having an adhesion surface. A step of providing a Li metal film or Li alloy film on the adherend surface of the release sheet for metal film transfer, The steps of bringing the release sheet for metal film transfer into close contact with the Li metal film or the Li alloy film on the object to be transferred, and The process includes at least the step of peeling and transferring the Li metal film or the Li alloy film from the adherend surface of the release sheet for metal film transfer to the transfer body, A method for manufacturing a metallic lithium electrode. [Industrial applicability]

[0054] The release sheet for metal film transfer of the present invention is excellent in the peelability and stability of the metal film over time, and furthermore, it is possible to peel and transfer a metal film with excellent surface smoothness. Therefore, it can be widely and effectively used as a release sheet for metal film transfer, and is particularly effective as a release sheet used in the manufacture of metallic lithium electrodes and lithium secondary battery negative electrodes. [Explanation of symbols]

[0055] 100 ···Release sheets for metal film transfer 101 ···Release sheet for metal film transfer with metal film M provided 102...Release sheet for metal film transfer, adhering to the transfer target S on a metal film M. 11 ···Base film 11a...Surface 11b...Surface 21 ···Free metal ion trap layer 21a...Surface 31...Release layer 31a...Adhesive surface 41 ···Matte layer M...Metal film S...transfer target T ···Transfer

Claims

1. A release sheet for metal film transfer, comprising at least a base film and a release layer having an adhesion surface, wherein a metal film is applied to the adhesion surface of the release layer, and the metal film is then transferred and peeled off from the adhesion surface onto a transfer object, A free metal ion trap layer is further provided between the substrate film and the release layer. The release layer comprises a fluororesin layer and / or a fluoromodified resin. The oxygen permeability of the free metal ion trap layer (according to JIS K-7126, 25°C, 80% RH) is 60 ml / m² / day / MPa or less. Release sheet for metal film transfer.

2. The free metal ion trap layer is a deposited film. The release sheet for metal film transfer according to claim 1.

3. The free metal ion trap layer has a thickness of 0.1 to 500 nm. The release sheet for metal film transfer according to claim 1.

4. The metal film is a Li metal film or a Li alloy film. The release sheet for metal film transfer according to claim 1.

5. The metal film is a vapor-deposited film. The release sheet for metal film transfer according to claim 1.

6. The metal film is a metallic lithium electrode. The release sheet for metal film transfer according to claim 1.

7. The aforementioned metal film is the negative electrode of a lithium secondary battery. The release sheet for metal film transfer according to claim 1.

8. The base film is one selected from the group consisting of polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film. The release sheet for metal film transfer according to claim 1.

9. The aforementioned base film further comprises a mat layer on the surface opposite to the release layer, The mat layer, the base film, the free metal ion trap layer, and the release layer are arranged in this order. The release sheet for metal film transfer according to claim 1.

10. The release layer has a thickness of 10 to 400 nm. The release sheet for metal film transfer according to claim 1.

11. A base film and A free metal ion trap layer, A release layer having an adhesion surface, The metal film formed on the surface to be adhered, It must have at least these in this order, The release layer comprises a fluororesin layer and / or a fluoromodified resin. The oxygen permeability of the free metal ion trap layer (according to JIS K-7126, 25°C, 80% RH) is 60 ml / m² / day / MPa or less. Release sheet for metal film transfer.

12. A release sheet for metal film transfer, comprising at least a base film and a release layer having an adhesion surface, wherein a metal film is applied to the adhesion surface of the release layer, and the metal film is then transferred and peeled off from the adhesion surface onto a transfer object, A free metal ion trap layer is further provided between the substrate film and the release layer. The release layer comprises a fluororesin layer and / or a fluoromodified resin. The free metal ion trap layer contains any of silicon oxide, aluminum oxide, or a composite oxide of silicon oxide and aluminum oxide. Release sheet for metal film transfer.

13. The oxygen permeability of the free metal ion trap layer (according to JIS K-7126, 25°C, 80% RH) is 60 ml / m². 2 It is less than or equal to / day / MPa The release sheet for metal film transfer according to claim 12.

14. A base film and A free metal ion trap layer, A release layer having an adhesion surface, The metal film formed on the surface to be adhered, It must have at least these in this order, The release layer comprises a fluororesin layer and / or a fluoromodified resin. The free metal ion trap layer contains one of the following: silicon oxide, aluminum oxide, or a composite oxide of silicon oxide and aluminum oxide. Release sheet for metal film transfer.

Images