WO2015122301A1 - 多孔質金属箔及びその製造方法 - Google Patents

多孔質金属箔及びその製造方法 Download PDF

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WO2015122301A1
WO2015122301A1 PCT/JP2015/052834 JP2015052834W WO2015122301A1 WO 2015122301 A1 WO2015122301 A1 WO 2015122301A1 JP 2015052834 W JP2015052834 W JP 2015052834W WO 2015122301 A1 WO2015122301 A1 WO 2015122301A1
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Prior art keywords
metal foil
porous metal
metal
release layer
porous
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PCT/JP2015/052834
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English (en)
French (fr)
Japanese (ja)
Inventor
尚光 井上
近藤　和夫
池田　裕一
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三井金属鉱業株式会社
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Publication of WO2015122301A1 publication Critical patent/WO2015122301A1/ja

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/08—Perforated or foraminous objects, e.g. sieves
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
    • C25D5/611—Smooth layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers

Definitions

  • the present invention relates to a porous metal foil and a method for producing the same, and more specifically to a porous metal foil having a high aperture ratio suitable for use as a transparent conductive film and a method for producing the same.
  • the touch panel generally has a configuration in which a transparent conductive film is formed as an electrode on a transparent substrate such as a glass plate.
  • the most widely used material for the transparent conductive film is ITO (indium tin oxide).
  • ITO indium tin oxide
  • ITO contains indium which is a rare metal, it is expensive and accompanied by supply concerns, and the film must be formed by sputtering, which increases equipment and manufacturing costs, and further due to heat during sputtering.
  • the base material may be distorted depending on the material of the base material.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2012-94254 discloses a transparent conductive film in which a regular fine metal wire network and a graphene sheet are combined.
  • Patent Document 2 Japanese Patent No. 4610416 discloses a capacitive touch panel using a metal as a conductive film having a mesh structure.
  • Patent Document 3 Japanese Patent No. 5282991 discloses a transparent conductive layer containing metal nanowires.
  • Patent Document 4 Japanese Patent Publication No. 2012-527071 also discloses a transparent conductive layer containing nanowires, as in Patent Document 3.
  • Patent Document 5 Japanese Patent Laid-Open No. 2013-178550 discloses a method of manufacturing a metal fine wire sheet by vapor deposition or the like using a base material having an uneven shape.
  • these technologies have various problems such as a large number of manufacturing steps and high manufacturing costs, and insufficient surface resistivity and light transmittance as a transparent conductive film, and further improvements are desired. ing.
  • Patent Document 6 International Publication No. 2010/034949 discloses a conductive grid having an irregular pattern manufactured using a mask having a network of openings having substantially vertical mask zone edges. It is disclosed.
  • the conductive grid is said to have low electrical resistance ( ⁇ 2 ⁇ ) and high light transmittance (> 80%), but the masking layer is dried to form a mask with a network of openings.
  • a complicated process such as a process for removing the masking layer must be performed, and the removed masking layer cannot be reused, resulting in a large number of manufacturing processes and a high manufacturing cost.
  • the masking layer is formed each time, it is understood that the reproducibility of the network shape obtained through the masking layer is inferior.
  • the cross-sectional shape of the strands constituting the conductive grid becomes substantially rectangular due to the edge of the substantially vertical mask zone.
  • Patent Document 7 Japanese Patent No. 4762368 discloses a porous metal foil having a two-dimensional network structure in which metal fibers are irregularly stretched.
  • the aperture ratio of the porous metal foil disclosed in this document cannot be said to be sufficiently high, and is not suitable for the use of a transparent conductive film in which a light transmittance of 85% or more is desired.
  • JP 2012-94254 A Japanese Patent No. 4610416 Japanese Patent No. 5282991 Special table 2012-527071 gazette JP 2013-178550 A International Publication No. 2010/034949 Japanese Patent No. 4762368
  • the present inventors have now found that it is possible to provide a porous metal foil that has an opening ratio that is high enough to be used as a transparent conductive film and that can be mass-produced by an inexpensive and simple process.
  • an object of the present invention is to provide a porous metal foil that has an opening ratio that is high enough to be used as a transparent conductive film and that can be mass-produced by an inexpensive and simple process.
  • the porous metal foil has a two-dimensional network structure composed of metal fibers that are irregularly stretched, and the metal fibers have a substantially semi-circular or substantially semi-elliptical cross-sectional shape.
  • a porous metal foil is provided wherein the porous metal foil has an open area ratio greater than 80%.
  • a method for producing a porous metal foil comprising: Forming a release layer made of chromium, a chromium alloy and / or a chromium oxide by performing electrolytic chromium plating on the conductive substrate, and generating a crack in the release layer by the stress of the release layer itself;
  • the release layer is electroplated with a metal that can be preferentially deposited on the cracks, and an infinite number of metal particles are grown along the cracks, thereby comprising a two-dimensional network structure composed of metal fibers and 80 Forming a porous metal foil having an open area ratio greater than%,
  • a manufacturing method is provided comprising:
  • FIG. 3 is an FE-SEM image obtained by observing the porous metal foil of Sample 1 manufactured in Example 1 from directly above.
  • 3 is an FE-SEM image obtained by magnifying and observing the metal fibers constituting the porous metal foil of Sample 1 produced in Example 1.
  • FIG. 3 is an FE-SEM image obtained by observing the porous metal foil of Sample 3 prepared in Example 1 from directly above.
  • FIG. 3 is an FE-SEM image obtained by magnifying and observing the metal fibers constituting the porous metal foil of Sample 3 prepared in Example 1.
  • FIG. 4 is a SIM image measured at an inclination angle of 60 ° C. showing a cut surface of a metal fiber constituting the porous metal foil of Sample 2 produced in Example 1 cut vertically.
  • 4 is a SIM image measured at an inclination angle of 60 ° C. showing a cut surface of a metal fiber constituting the porous metal foil of Sample 3 produced in Example 1 that is cut perpendicularly.
  • 4 is a SIM image measured at an inclination angle of 60 ° C. showing a cut surface of a metal fiber constituting the porous metal foil of Sample 4 produced in Example 1 cut vertically.
  • Example 4 is a photograph of the porous metal foil of Sample 3 peeled off with an adhesive tape in Example 3.
  • 4 is a photograph of a porous metal foil of Sample 3 that was immersed in a Cr etching solution and peeled in Example 3.
  • 6 is a graph showing the relationship between the aperture ratio measured in Example 4 and electrolytic copper plating time.
  • 6 is a graph showing the relationship between the wire diameter of a metal fiber measured in Example 4 and the electrolytic copper plating time.
  • 6 is a diagram showing light transmittance profiles in a visible light region of metal foils having various aperture ratios measured in Example 4.
  • FIG. 1 shows a schematic top view of an example of a porous metal foil according to the present invention.
  • a porous metal foil 10 according to the present invention has a two-dimensional network structure composed of metal fibers 11 that are irregularly stretched. Since this two-dimensional network structure presents a unique pattern reminiscent of the mask melon skin pattern, the applicant refers to this kind of porous metal foil as a mask melon foil.
  • the porous metal foil 10 of this invention has an aperture ratio exceeding 80%. This extremely high aperture ratio exceeding 80% enables the high light transmittance desired for the transparent conductive film (particularly, the transmittance in the visible light region).
  • Metallic transparent conductive films are already known (see, for example, Patent Documents 1 to 6).
  • Patent Document 7 discloses a porous metal foil having an irregular two-dimensional network structure, the aperture ratio is low, for example, 28% or 33%, and is not suitable for use as a transparent conductive film. Met.
  • the porous metal foil of Patent Document 7 can be manufactured by the same technique as the electrolytic copper foil except that it involves the formation of a release layer in which cracks are formed, a transparent conductive film is manufactured by this technique. If it can be done, it can be said that it is extremely convenient from the viewpoint of manufacturing cost, mass productivity and the like.
  • the transparent conductive film can be mass-produced by an inexpensive and simple process according to the manufacturing method derived from electrolytic copper foil. Because it becomes. Actually, it has never been easy to obtain a porous metal foil having an open area ratio exceeding 80% by the above approach derived from electrolytic copper foil. However, the present inventors now have an open area ratio exceeding 80%.
  • the present invention succeeded in producing a porous metal foil having an irregular two-dimensional network structure. That is, according to the present invention, it is possible to provide a porous metal foil that has an opening ratio that is high enough to be used as a transparent conductive film and that can be mass-produced by an inexpensive and simple process. Moreover, since the porous metal foil 10 is made of metal, it can have a low sheet resistance suitable for a transparent conductive film.
  • This porous metal foil 10 has an opening ratio of more than 80%, preferably 83% or more, more preferably 85% or more, further preferably 87% or more, particularly preferably 90% or more, 93% or more or 95%. That's it.
  • the higher the aperture ratio the higher the light transmittance.
  • the aperture ratio and light transmittance (especially the light transmittance in the visible light region) have a high correlation regardless of the aperture ratio, and the aperture ratio value and the visible light region Is approximately the same as or not very close to the value of light transmittance at a wavelength of.
  • the porous metal foil 10 can have a high light transmittance (particularly the light transmittance in the visible light region), and the conductivity of the metal constituting the metal fiber 11 can be improved. Combined with, it becomes a very useful foil for use as a transparent conductive film. Since the aperture ratio is desired to be high in this way, the upper limit is not particularly limited as long as desired conductivity is ensured, but the aperture ratio is realistically 98% or less, 97% or less, or 96% or less. .
  • the aperture ratio in the present invention is defined as an area aperture ratio, and is specifically measured by the following procedure. That is, an enlarged photograph of a certain area is taken from directly above with an electron microscope, and this is measured by calculating the ratio of the opening area to the area using image analysis software.
  • the metal fiber 11 is a metal fiber, and the metal to be used may be appropriately determined according to the intended use, and is not particularly limited.
  • Preferred metals comprise at least one selected from the group consisting of copper, gold, silver, nickel, cobalt, tin, and zinc.
  • “comprising” may be any metal or alloy mainly containing the above-listed metal elements, and means that it is allowed to contain other metal elements and unavoidable impurities as the balance. Preferably, it means that 50% by weight or more of the metal or alloy is composed of the metal elements listed above, and typical examples include those composed of the metal elements listed above and inevitable impurities.
  • those suitable for the transparent conductive film include at least one selected from the group consisting of copper, copper alloys, gold, silver, nickel, cobalt, tin, and zinc, and more preferably Copper from the viewpoint of conductivity.
  • the metal fiber may be a surface-treated metal fiber as a base material with a surface treatment agent containing a different type of metal from the base material. Examples of metals used for such surface treatment include nickel, cobalt, Tin and zinc are mentioned.
  • the wire diameter of the metal fiber 11 is preferably 14 ⁇ m or less, more preferably 10 ⁇ m or less, still more preferably 7 ⁇ m or less, and most preferably 4 ⁇ m or less.
  • the thin wire diameter contributes to a high aperture ratio.
  • the lower limit of the wire diameter is not particularly limited as long as desired conductivity is ensured, but from the viewpoint of handling properties, the wire diameter is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more.
  • the “wire diameter” is defined as the width (thickness) of the metal fiber 11 when the porous metal foil 10 is viewed from directly above, and includes a field emission scanning electron microscope (FE-SEM), a scanning ion microscope ( (SIM) or the like.
  • the metal fiber 11 has a substantially semicircular or substantially semi-elliptical cross-sectional shape as shown in FIG.
  • This substantially semicircular or substantially semi-elliptical cross-sectional shape is a shape imparted from the manufacturing method of the present invention as shown in FIG. 3 to be described later, but undergoes masking as disclosed in Patent Document 6.
  • the blackening process for example, the process of attaching copper oxide
  • the blackening process of the metal foil can be performed uniformly without any unevenness. Furthermore, there is also an advantage that there is little reflection of transmitted light on the side surface of the metal fiber, and a decrease in display brightness can be reduced.
  • the metal fiber 11 is preferably a branched fiber, and the porous metal foil 10 is made high by forming a two-dimensional network structure in which the branched fibers are irregularly stretched. It is possible to preferably maintain a peelable foil form while having an aperture ratio.
  • the two-dimensional network structure preferably has an irregular shape due to cracks formed on the surface of the substrate.
  • the above-described cross-sectional shape and branched shape of the metal fiber 11 are formed by connecting innumerable metal particles due to nucleation along cracks of the release layer described later. .
  • the metal particles constituting the metal fiber may no longer have a complete particle shape.
  • the metal particles constituting the metal fiber 11 are continuous in a shape having a bead-like or worm-like (caterpillar-like) seam, but may be in a shape in which the seam is not substantially observed. Therefore, as shown in FIG.
  • the metal particles constituting the metal fiber 11 have a hemispherical shape having a spherical portion 11a and a bottom portion 11b, and the bottom portions 11b of all the metal particles are on the same base surface. It can also be expressed that the spherical portions 11a of all the metal particles are located on the same side with respect to the base surface.
  • the width D of the bottom portion 11b along the basal plane becomes the wire diameter
  • the maximum cross-sectional height H of the spherical portion 11a corresponds to the thickness of the porous metal foil.
  • the basal plane and the bottom portion 11b positioned thereon reflect the planar shape of the release layer used during manufacturing.
  • the metal fiber 11 has a substantially semicircular or substantially semi-elliptical cross-sectional shape.
  • the average ratio of the maximum cross-sectional height H to the wire diameter D is not particularly limited.
  • the metal fiber 11 has a substantially semicircular cross-sectional shape, and the average ratio (H / D) of the maximum cross-sectional height H to the wire diameter D is typically 0.30 to It can be 0.70, more typically 0.40 to 0.60, even more typically 0.45 to 0.55, and most typically about 0.50. This average ratio can be adjusted by appropriately changing the plating conditions and the like.
  • the metal fiber 11 has a substantially elliptical cross-sectional shape, and the average ratio (H / D) of the maximum cross-sectional height H to the wire diameter D exceeds 0.50. It is preferably 0.50 to 2.00, more preferably 0.75 to 1.75, and particularly preferably 1.00 to 1.50. With such a ratio, the metal fiber 11 has a raised shape higher than the semicircular cross section, and the ease of peeling of the porous metal foil from the release layer after electrodeposition is improved, and the sheet resistance of the porous metal foil is improved. Is reduced.
  • Such a shape can be realized by adding an additive to the plating bath of the porous metal foil and / or lengthening the electrolysis time.
  • the porous metal foil 10 preferably has a thickness of 0.5 to 28 ⁇ m, more preferably 0.75 to 17.5 ⁇ m, still more preferably 1.5 to 12.5 ⁇ m, and particularly preferably 1.75 to 10 ⁇ m. Most preferably, the thickness is 2 to 6 ⁇ m. Within this range, handling is relatively easy while the aperture ratio is high, and sheet resistance can be reduced. However, the handling of the porous metal foil 10 may be a self-supporting form peeled from the base material, may be a form as it is coated on the base material, or may be from the base material to another base material. The thickness of the porous metal foil 10 may be appropriately set within the above range according to the form to be adopted.
  • the thickness of the porous metal foil corresponds to the maximum cross-sectional height of the metal fibers.
  • a thickness is preferably measured by a commercially available film thickness measuring device using a measuring element larger than the pore size of the porous metal foil.
  • This manufacturing method includes (1) a step of preparing a conductive base material, (2) a step of forming a cracked release layer by electrolytic chrome plating, and (3) a step of forming a porous metal foil by electrolytic plating. And (4) a step of peeling the porous metal foil as desired. Since this manufacturing method is a method derived from electrolytic copper foil, the transparent conductive film can be mass-produced by an inexpensive and simple process. Therefore, although the manufacturing method of porous metal foil is preferably performed by a continuous manufacturing method, it may be performed by a single wafer method. In particular, once a cracked release layer is formed on a conductive substrate, the release layer / conductive substrate can be reused thereafter. It becomes a possible manufacturing method, and a significant reduction in manufacturing cost can be realized.
  • FIG. 3 shows a flow of a manufacturing process of a porous metal foil according to the present invention.
  • a conductive substrate 12 is prepared as a support for producing a porous metal foil.
  • the conductive substrate may be a substrate having conductivity that can be plated, and any of inorganic materials, organic materials, laminates, and materials having a metal surface can be used. Is a metal.
  • Preferred examples of such metals include metals such as copper, nickel, cobalt, iron, chromium, tin, zinc, indium, silver, gold, aluminum, and titanium, and alloys containing at least one of these metal elements.
  • the form of the conductive substrate is not limited, and various forms of substrates such as a foil, a plate, and a drum can be used.
  • a conductive metal plate may be wound around the drum body, and the thickness of the conductive metal plate in this case is preferably 1 to 20 mm.
  • the conductive base material supports the manufactured porous metal foil during its processing or until just before its use, thereby improving the handleability of the porous metal foil.
  • using a metal foil or a metal plate as a conductive substrate means that the metal foil or metal plate as the conductive substrate can be reused as it is after the production of the porous metal foil, or can be recycled by melting and forming the foil. It is preferable because of its advantages. In that case, it is preferable that the thickness of the metal foil or metal plate is 10 ⁇ m to 1 mm, because it is possible to secure a strength that does not cause twisting in the manufacturing process of the metal foil or metal plate and the subsequent processing / conveying process. .
  • the conductive substrate 12 is subjected to pretreatment such as acid washing and degreasing to clean its surface.
  • Electrolytic chromium plating is applied to the conductive substrate 12 to form a release layer 13 made of chromium, a chromium alloy and / or a chromium oxide.
  • a crack 13a is generated in the release layer 13 by its own stress.
  • the peeling layer 13 is a layer for facilitating the peeling of the porous metal foil 10 to be formed on the peeling layer 13, can generate the crack 13 a, is easily plated with the crack 13 a, and has no crack.
  • a material having the property of being difficult to be plated at 13b is used, and specifically, chromium, a chromium alloy and / or a chromium oxide.
  • a material capable of preferentially depositing a certain kind of metal in the generated crack 13 a by plating is used as the release layer 13.
  • the formation conditions of the release layer 13 can be easily controlled, and as a result, how the cracks 13a enter the release layer 13 can be skillfully controlled. In this way, the generation ratio of the metal fibers formed along the cracks can be controlled to be low, whereby a porous metal foil having an opening ratio exceeding 80% can be realized.
  • the release layer may be formed in multiple layers. In this case, cracks may be formed only in the upper layer, and cracks may be formed not only in the upper layer but also in layers below it. It may be a thing.
  • the crack 13a is preferably controlled so as to be naturally generated by the stress of the release layer 13, and need not be formed at the same time as film formation, and is generated in the subsequent cleaning and drying process, machining, etc. Good. Cracks are usually undesirable, but the manufacturing method of the present invention is rather characterized by actively utilizing them. In particular, since cracks are usually formed such that branched lines are stretched around in a two-dimensional network, porous metal foil having an extremely high aperture ratio can be formed by forming metal fibers along the cracks. Can be obtained.
  • cracks since the occurrence of cracks is always a concern in normal film formation processes, the generation of cracks themselves is well-experienced by those skilled in the art engaged in film formation. It is possible to easily select within the range.
  • cracks may be generated by controlling the composition of the plating bath, the thickness of the release layer, the current density, the bath temperature, the stirring conditions, the post heat treatment, or the like.
  • the peeling layer 13 is a chromium plating layer made of chromium, a chromium alloy and / or a chromium oxide. Chromium has a high hardness and is excellent in terms of continuous peelability, durability and corrosion resistance, and is advantageous in that it is easily peeled off due to the formation of a passive state.
  • the thickness of the release layer 13 is preferably 4 to 120 ⁇ m, more preferably 6 to 80 ⁇ m, still more preferably 8 to 60 ⁇ m, and most preferably 10 to 40 ⁇ m. With such a composition and thickness, the porous metal foil 10 to be formed on the layer can be formed on the layer by making the release layer have a high resistance with respect to the conductive substrate while allowing the generation of cracks.
  • the thickness range of the release layer 13 described above can be unnecessarily thick when considering only the releasability, but by using a thick release layer, the generation ratio of cracks is reduced.
  • the aperture ratio of the obtained porous metal foil 10 can be significantly increased. Although the reason for this is not necessarily clear, it is considered that internal stress or internal strain is likely to be accumulated by increasing the thickness of the release layer 13, and as a result, easy generation of cracks is suppressed.
  • chromium plating solutions for electrolytic chromium plating include a sergeant bath (composition: chromic anhydride 250 g / L and sulfuric acid 2.5 g / L) and a hard chromium plating bath.
  • a sergeant bath composition: chromic anhydride 250 g / L and sulfuric acid 2.5 g / L
  • a hard chromium plating bath examples include Anchor 1127 manufactured by Meltex, HEEF-25 manufactured by Atotech, and Mac 1 manufactured by Nihon McDermid. Of these, the Sargent bath is particularly preferred because it tends to generate relatively few cracks and easily increases the aperture ratio of the porous metal foil.
  • the Sargent bath has fewer cracks than the HEEF bath containing the additive (for example, a bath containing chromic acid, sulfuric acid and HEEF-25), and thus has a high opening ratio. can get.
  • Electrolytic chrome plating may be carried out so as to obtain a desired thickness by appropriately setting the electrolysis conditions according to the composition of the chrome plating bath to be used. However, it is performed for 20 minutes or more at a current density of 30 to 100 A / dm 2. More preferably, it is 25 minutes or more at a current density of 40 to 90 A / dm 2 , more preferably 30 minutes or more at a current density of 45 to 70 A / dm 2 .
  • a Sargent bath preferably at a current density of 45 to 70 A / dm 2 , more preferably 50 to 65 A / dm 2 , still more preferably 50 to 65 A / dm 2 , particularly preferably 55 to 65 A / dm 2 , It is preferably performed for 30 minutes or more, more preferably 40 to 120 minutes, further preferably 50 to 90 minutes, particularly preferably 60 to 80 minutes.
  • the current density is higher and the chrome plating time is longer, the amount of coulomb increases, resulting in an increase in the thickness of the release layer 13.
  • the aperture ratio tends to increase as described above.
  • the aperture ratio increases at a high current density of around 60 A / dm 2 .
  • a preferable bath temperature in electrolytic chrome plating is 45 to 65 ° C, more preferably 45 to 60 ° C.
  • a stable chromium plating bath typically contains a small amount of trivalent chromium, and the amount is about 2 to 6 g / L. Further, a catalyst such as organic sulfonic acid may be added to the hard chromium plating bath.
  • concentration of chromic anhydride can be controlled by the Baume degree.
  • impurities such as iron, copper, and chloride ions affect the state of plating, care must be taken in managing the upper limit of the amount of impurities dissolved.
  • a titanium-coated lead oxide or Pb—Sn alloy can be preferably used.
  • a Ti—Pb electrode (Sn of SnF) is used. : 5%) and Exelod LD manufactured by Nippon Carlit.
  • the release layer 13 Prior to the formation of the porous metal foil by electroplating, the release layer 13 is preferably subjected to washing, drying, and heat treatment. Washing may be performed with an aqueous solvent such as water, or with an organic solvent such as acetone. Drying may be performed by either natural drying or heat drying.
  • the heat treatment is preferably performed at 80 to 180 ° C. for 2 to 16 hours, more preferably at 130 to 170 ° C. for 4 to 8 hours. This heat treatment is preferably performed in an oxygen-containing atmosphere such as an air atmosphere. By this heat treatment, the surface of the release layer 13 is oxidized, and Cr 2 O 3 is formed as a passive state. This has an advantage that the porous metal foil 10 can be easily peeled off.
  • the release layer 13 is electroplated with a metal that can be preferentially deposited on the crack 13a, and the innumerable metal particles 11 are grown along the crack 13a.
  • a porous metal foil 10 having a two-dimensional network structure composed of metal fibers and having an open area ratio exceeding 80% is formed.
  • the release layer 13 has the crack 13a having the property of being easily plated and the crack-free surface portion 13b having the property of being difficult to be plated.
  • the reason why plating with the crack 13a is facilitated is that the current is more likely to flow in the portion where the crack 13a is present than in the portion 13b where the crack 13a is not present, so that nucleation and growth occur preferentially in the crack 13a.
  • the metal that can be preferentially deposited in the crack 13a preferably comprises at least one selected from the group consisting of copper, gold, silver, nickel, cobalt, tin, and zinc, and more preferably copper, silver, And at least one selected from the group consisting of gold, and more preferably copper.
  • the conditions for the electroplating of the metal that can be preferentially deposited in cracks are in accordance with the known conditions using various known metal plating baths, except that the current density and time are set so as to give an opening ratio exceeding 80%. Just do it.
  • Such electrolytic plating is preferably performed at a current density of 0.5 to 10 A / dm 2 , more preferably 1 to 8 A / dm 2 , even more preferably 2 to 6 A / dm 2 , preferably 1 to 500 seconds, and more. It is preferably performed for 3 to 150 seconds, more preferably 5 to 75 seconds. Thus, it becomes easier to realize a high aperture ratio by performing electroplating for a short time at a considerably low current density.
  • the bath temperature is preferably 10 to 60 ° C, more preferably 15 to 55 ° C, and further preferably 20 to 50 ° C.
  • the electrolytic copper plating is preferably performed at a current density of 1 to 5 A / dm 2 for 2 to 250 seconds, more preferably 1.5 to 4 2-170 seconds at a current density of .5A / dm 2, still preferably performed 2.5 to 120 seconds at a current density of 2 ⁇ 4A / dm 2.
  • Electrolytic copper plating is preferably performed using a copper sulfate plating bath, and the preferred composition of the copper sulfate plating bath is a copper sulfate pentahydrate concentration: 150 to 320 g / L, and a sulfuric acid concentration: 15 to 200 g / L. .
  • the preferred bath temperature for copper sulfate plating is 15 to 55 ° C., more preferably 20 to 50 ° C., and further preferably 25 to 45 ° C.
  • An additive may be appropriately added to the plating solution to improve the characteristics of the metal foil.
  • preferred examples of such additives include sulfur-containing compounds such as glue, gelatin, chlorine and thiourea, and synthetic additives such as polyethylene glycol.
  • the concentration of the additive is not limited, but is usually 1 to 300 ppm.
  • the porous metal foil can be peeled off from the conductive substrate having the release layer to obtain a single porous metal foil. After peeling, it may be transferred to another substrate such as a film with an adhesive layer, or peeling itself may be performed by transfer to another substrate.
  • the peeling of the porous metal foil can be performed with an adhesive tape or by immersing in an etching solution, and various methods can be adopted.
  • this peeling step is not essential, and the substrate may be handled as a porous metal foil product with the substrate attached via the peeling layer, and may be peeled off for the first time during use.
  • Example 1 Production of Porous Metal Foil A stainless steel plate having a thickness of 0.5 ⁇ m was prepared as a conductive substrate. Chromium plating was performed on the stainless steel plate as a release layer by the following procedure. First, after dipping in acetone (99.0%, manufactured by Wako Pure Chemical Industries) for 10 seconds, the surface is cleaned by washing with pure water and drying. Next, the stainless steel plate foil was immersed in a Sargent bath in which 2.5 g / L sulfuric acid and 250 g / L chromic acid were dissolved, bath temperature: 50 ° C., current density: 60 A / dm 2 , anode: Pb, Chromium plating was performed for 72 minutes under the condition of cathode: stainless steel plate.
  • acetone 99.0%, manufactured by Wako Pure Chemical Industries
  • the stainless steel plate on which the chromium plating layer was formed was washed with acetone and then dried.
  • the thickness of the obtained chrome plating was measured by XRF (fluorescence X-ray analysis), it was about 15 ⁇ m, and numerous cracks generated by plating stress were confirmed on the surface of the chrome plating.
  • the dried chrome plating layer was heat-treated at 150 ° C. for 5 hours in an air atmosphere.
  • Copper sulfate plating was performed on the chromium plating in which the cracks occurred.
  • a stainless steel plate coated with chromium was immersed in a copper sulfate plating bath in which 25 g / L of sulfuric acid and 200 g / L of copper sulfate pentahydrate were dissolved, and the current density was 3 A / dm 2 .
  • anode Cu
  • cathode chromium plating layer, 75 seconds (sample 1), 30 seconds (sample 2), 15 seconds (sample 3), 7 seconds (sample 4) or 3 seconds (sample) 5) I went.
  • Example 2 Observation of Porous Metal Foil
  • the porous metal foils of Samples 1 and 3 obtained in Example 1 were observed from directly above with a field emission scanning electron microscope (FE-SEM).
  • the image shown in 5A was obtained.
  • the metal fibers of the porous metal foils of Samples 1 and 3 were observed with a field emission scanning electron microscope (FE-SEM)
  • the images shown in FIGS. 4B and 5B were obtained, respectively.
  • bead-like or worm-like (caterpillar-like) irregularities due to the spherical portions of the metal particles were observed on the growth surface.
  • FIG. Images shown in 6B and 6C were obtained.
  • the cross-sectional structure of the metal fiber is precipitated radially starting from the crack, and the cross-sectional shape of the metal fiber is a semicircular shape including a spherical portion and a planar bottom surface.
  • the cross section of the metal fiber has a two-layer structure, which is because the metal fiber is previously coated with carbon in order to clearly observe the processed surface. It was about 0.50 when the ratio with respect to the wire diameter D of the largest cross-section height H in a metal fiber cross section was computed.
  • Example 3 Peeling of porous metal foil (1) Peeling with adhesive tape High tackiness on the surface of samples 1 to 5 (formed on a conductive substrate through a peeling layer) obtained in Example 1 A pressure-sensitive adhesive tape (manufactured by Nitoms Co., Ltd., super-transparent double-sided pressure-sensitive adhesive sheet, product number T: 284) was attached, and the pressure-sensitive adhesive tape was peeled off. As a result, as shown in FIG. 7, the porous metal foil was peeled off in a form transferred to the adhesive tape. The peeled porous metal foil was attached to a glass plate.
  • Example 4 Measurement of aperture ratio, wire diameter and thickness
  • the aperture ratio, wire diameter and thickness of the porous metal foil obtained in Example 1 were measured as follows. (Measurement method of aperture ratio) Using an electron microscope, an SEM photograph of the porous metal foil at a magnification of 100 was taken so that the observation area was 1.137 mm 2 . Next, the image processing software: Image-J was used to identify the metal fiber portion and the opening portion, and the ratio of the opening portion area to the total observation area was calculated and used as the opening ratio.
  • FIG. 9 shows the relationship between the aperture ratio and the copper plating time
  • FIG. 10 shows the relationship between the wire diameter and the copper plating time.
  • Example 5 Relationship between aperture ratio and transmittance
  • various conditions such as chromium plating and copper sulfate plating were appropriately changed in Example 1 so that the aperture ratio was 71.0%, 46 0.0% and 13.2% porous copper foils were produced.
  • the transmittance in the visible light region of the obtained porous copper foil was measured with an absorptiometer, the result shown in FIG. 11 was obtained.
  • the porous metal foil of the present invention having an aperture ratio of 80%, preferably more than 85%, has a very high light transmittance in the visible light region (approximately more than 80%, preferably more than 85%). However, it can be seen that it is extremely suitable for the use of the transparent conductive film.

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004228057A (ja) * 2002-11-25 2004-08-12 Fuji Photo Film Co Ltd 網目状導電体及びその製造方法並びに用途
JP2009167523A (ja) * 2007-12-18 2009-07-30 Hitachi Chem Co Ltd めっき用導電性基材、その製造方法及びそれを用いた導体層パターン若しくは導体層パターン付き基材の製造方法、導体層パターン付き基材および透光性電磁波遮蔽部材
JP2011513890A (ja) * 2007-12-20 2011-04-28 シーマ ナノ テック イスラエル リミティド 微細構造化材料及びその製造方法
JP2012503715A (ja) * 2008-09-25 2012-02-09 サン−ゴバン グラス フランス サブミリメートル導電性グリッドの製造方法及びサブミリメートル導電性グリッド
WO2012137613A1 (ja) * 2011-04-08 2012-10-11 三井金属鉱業株式会社 多孔質金属箔およびその製造方法
JP2012219333A (ja) * 2011-04-08 2012-11-12 Mitsui Mining & Smelting Co Ltd 複合金属箔およびその製造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004228057A (ja) * 2002-11-25 2004-08-12 Fuji Photo Film Co Ltd 網目状導電体及びその製造方法並びに用途
JP2009167523A (ja) * 2007-12-18 2009-07-30 Hitachi Chem Co Ltd めっき用導電性基材、その製造方法及びそれを用いた導体層パターン若しくは導体層パターン付き基材の製造方法、導体層パターン付き基材および透光性電磁波遮蔽部材
JP2011513890A (ja) * 2007-12-20 2011-04-28 シーマ ナノ テック イスラエル リミティド 微細構造化材料及びその製造方法
JP2012503715A (ja) * 2008-09-25 2012-02-09 サン−ゴバン グラス フランス サブミリメートル導電性グリッドの製造方法及びサブミリメートル導電性グリッド
WO2012137613A1 (ja) * 2011-04-08 2012-10-11 三井金属鉱業株式会社 多孔質金属箔およびその製造方法
JP2012219333A (ja) * 2011-04-08 2012-11-12 Mitsui Mining & Smelting Co Ltd 複合金属箔およびその製造方法

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