Metal image forming method

Abstract

To solve a problem of difficulty in providing a substrate made of thermosetting resin, UV curable resin, glass, ceramics, or the like having a curved surface shape on which a metal image is formed from the viewpoint of reliability and designability of a product in an application field of a substrate on which a metal image is formed because a conventional technique is based on a premise that thermoplastic resin is used as a substrate material.SOLUTION: A substrate T itself molded into a curved surface shape in advance is used as a mold, a substrate on which resin images 31 to 36 capable of being plated are formed is molded so as to adhere to the substrate T, so that the resin images are transferred onto the substrate T of the curved surface shape, catalytic ability is imparted to the resin images, and electroless plating treatment is performed. Then, high-definition metal images 51 to 56 are formed on the substrate T of the curved surface shape made of thermosetting resin, UV curable resin, glass, ceramics, or the like.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for forming a metal image. More specifically, it relates to a method for forming a metal image on a metal having an overall or partial curved surface shape.

Background Art

[0002] Substrates with metal images formed thereon are used in products such as touch panels, EL lights, electromagnetic shields, antennas, and heating elements. Usually, the substrates have a flat shape or a gently curved surface shape. This is because if the metal image is formed into a shape with a large curvature, disconnection will occur. As a first solution, a drawing flat plate having an electrode layer with a plurality of electrode regions is created by using a conductive ink composed of a conductive substance and a binder on a flat plate made of a thermoplastic resin, and the drawing flat plate is heated, softened, formed, and cooled to produce a capacitive touch panel having a curved touch surface (see, for example, Patent Document 1). Although the conductive ink is less likely to cause disconnection during forming, compared with metal images, it has a problem that it cannot be made into fine lines due to its low conductivity and has poor transparency. As a second solution, first, a catalyst layer is provided on the surface of a transparent base material made of a thermoplastic resin, and further, a shielding layer having a large number of fine line grooves reaching the surface of the catalyst layer is formed on the catalyst layer. Next, after forming the whole or part of the transparent base material into a curved surface shape, a metal plating treatment is performed to form fine lines of a conductive metal in the fine line grooves (see, for example, Patent Document 2). By this method, the transparency of the substrate made of a thermoplastic resin on which a metal image is formed is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above technical field, from the viewpoints of product reliability, designability, etc., there is a need for substrates made of thermosetting resins, UV curable resins, glass, ceramics, etc. having a curved surface shape with a metal image formed thereon. However, both of the above two solutions are premised on using a thermoplastic resin as the substrate material, and it has been difficult to meet the above requirements.

[0005] The present invention proposes a method for forming a metal image to solve the above problems.

Means for Solving the Problems

[0006] On the other hand, the present inventors have proposed a method for forming a metal image on an arbitrary substrate by a method unrelated to the above two solutions (see the specification of Japanese Patent Application No. 2023-123863). That is, without using a photoreceptor, an electrostatic pattern is directly formed on the release layer of a substrate S composed of a release layer, an insulating layer, and a conductive layer, and this electrostatic pattern is developed with electroplatable charged particles called toner to form a high-resolution toner image, and this toner image is transferred onto an arbitrary substrate T serving as a transfer target. Catalytic ability is imparted to this toner image, and by performing electroless plating treatment, a high-definition metal image is formed on an arbitrary substrate T.

[0007] However, even if a substrate made of a thermosetting resin, UV curable resin, glass, ceramics, etc. is used as the substrate T in this method, it is impossible to obtain a substrate having a curved surface shape with a metal image formed thereon. Therefore, as a result of intensive studies beyond the common sense of molding, the present inventors have found that if the substrate T that has been previously molded into a curved surface shape is used as a mold, and the substrate S on which a resin image capable of plating is formed is molded so as to be in close contact with the substrate T, the resin image can be transferred onto the curved surface-shaped substrate T, and further, by imparting catalytic ability to the resin image and performing electroless plating treatment, a high-definition metal image can be formed on a curved surface-shaped substrate T made of a thermosetting resin, UV curable resin, glass, ceramics, etc., and thus the present invention has been achieved.

[0008] A metal image forming method for solving the above problems is provided by the present invention. (I) (1) A step of forming a plating - capable resin image on a substrate S having a flat - plate shape (resin image forming step), (2) A step of transferring the resin image onto a substrate T by molding the substrate S so that the resin image surface of the substrate S adheres to the surface of the substrate T having a curved - surface shape in whole or in part (resin image transfer step), (3) A metal image forming method characterized by comprising a step of imparting catalytic ability to the resin image on the substrate T and performing electroless plating treatment (electroless plating treatment step). (II) The flat - plate - shaped substrate S is composed of an insulating layer made of a thermoplastic resin film or sheet or a composite thereof and a release layer provided on one side of the insulating layer, and a plating - capable resin image is formed on the release layer by a printing method. The metal image forming method according to item 1 above. (III) The flat - plate - shaped substrate S is composed of an insulating layer made of a thermoplastic resin film or sheet or a composite thereof, a release layer provided on one side of the insulating layer, and a conductive layer provided on the opposite surface of the release layer. First, an electrostatic pattern is formed on the release layer, and then the electrostatic pattern is developed with charged particles capable of plating, which are called toner, so as to form a plating - capable resin image on the release layer. The metal image forming method according to item 1 above. (IV) Using an original plate having a plate layer on which a relief plate, intaglio plate, or gravure plate - like pattern is formed and a first electrode, and a substrate S having a release layer, an insulating layer, and a conductive layer serving as a second electrode. The plate layer of the original plate is brought into close contact with the release layer of the substrate S, and an appropriate voltage sufficient to discharge the gap between the pattern of the plate layer and the release layer is applied between the first electrode of the original plate and the second electrode of the substrate S, thereby forming an electrostatic pattern corresponding to the pattern of the plate layer on the release layer of the substrate S. The metal image forming method according to item 3 above. (V) It consists of a molded body made only of a conductive material or a laminate of an insulating material and a conductive material, and includes a mask sheet having a predetermined ion-permeability opening, a release layer, an insulating layer, and a conductive layer serving as a back electrode. Using a substrate S, the release layer of the mask sheet and the substrate S are brought into close contact, and after ion irradiation is performed through the mask sheet, the mask sheet is peeled off from the substrate S, thereby forming an electrostatic pattern corresponding to the ion-permeability opening and the ion-shielding portion of the mask sheet on the release layer of the substrate S. The method for forming a metal image according to claim 3, characterized in that

Effects of the Invention

[0009] In the prior art, in order to form a substrate on which a conductive layer is formed or a metal image is to be formed into a curved surface shape, the substrate material is limited to a thermoplastic resin. In contrast, in the method of the present invention, by using the substrate T that has been previously formed into a curved surface shape as a mold and molding the substrate S on which a resin image capable of plating has been formed so as to be in close contact with the substrate T, the resin image is transferred onto the substrate T, and further, a catalytic ability is imparted to the resin image and an electroless plating treatment is performed to form a metal image. Therefore, a high-definition metal image can be formed on a curved surface substrate T made of a thermosetting resin, a UV-curable resin, glass, ceramics, or the like.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0011] FIG. 1 shows an example of the resin image forming process. In the case of FIG. 1, resin images 31 to 36 capable of being plated are formed on the release layer 20 by a printing method.

[0012] The substrate S is composed of an insulating layer 10 and a release layer 20 provided on one side of the insulating layer 10. The insulating layer 10 is a film, sheet or composite thereof made of a thermoplastic resin. For example, films, sheets or composites thereof made of amorphous polyethylene terephthalate (A-PET), glycol-modified polyethylene terephthalate (G-PET), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polypropylene (PP) can be preferably used. Among these, films or sheets made of A-PET, G-PET or PC are particularly preferred. The thickness of the insulating layer 10 is not particularly limited and may be determined in consideration of the conditions of the resin image transfer process.

[0013] In order to facilitate the transfer of the plating-capable resin images 31 to 36 on the substrate S onto the substrate T, a release layer 20 is provided on the insulating layer 10. Thin films such as silicone-based resins, fluorine-based resins, olefin-based resins, and melamine-based resins formed by a coating method or the like can be used as the release layer 20. The thickness of the release layer is preferably 0.03 to 0.4 μm.

[0014] Examples of the printing method include screen printing, gravure offset printing, and inkjet. As the printing method, an ink containing a resin having a functional group with a ligand function that incorporates a metal to form a complex is used. Examples of the functional group include an amino group, a carboxyl group, a hydroxyl group, and a thiol group. The resin images 31 to 36 formed by the printing method have a function of adsorbing a catalytic metal or a catalytic metal ion.

[0015] FIG. 2 shows another example of the resin image forming process. In the case of FIG. 2, first, an electrostatic pattern is formed on the release layer 20, and then the electrostatic pattern is developed with electroplatable charged particles called toner, thereby forming electroplatable resin images 31 to 36 on the release layer 20.

[0016] The substrate S is composed of a conductive layer 40 that serves as an electrode during the formation of the electrostatic pattern, an insulating layer 10, and a release layer 20. The configurations of the insulating layer 10 and the release layer 20 are the same as those in the case of FIG. 1.

[0017] Since the conductive layer 40 only needs to play a role of supplying an electric field during the formation of the electrostatic pattern or stabilizing the charged charges on the release layer 20, it can be composed of any conductive material such as metal, conductive oxide, carbon, graphite, conductive polymer, etc. The conductive layer 40 is disposed on the opposite surface of the insulating layer 10 from the release layer 20. The conductive layer 40 can play the above role if it is pressure-bonded to the insulating layer 10, but if it is integrated with the release layer 20 and the insulating layer 10, it will be easier to handle during the formation and development of the electrostatic pattern. By forming the conductive layer 40 on the opposite surface of the insulating layer 10 from the release layer 20 by methods such as sputtering a metal film, a conductive oxide film, etc., or coating a conductive polymer film, etc., the release layer 20, the insulating layer 10, and the conductive layer 40 can be integrated. Alternatively, by laminating a conductive layer-attached sheet provided with a conductive layer 40 such as a metal film, a conductive oxide film, a conductive polymer film, etc. on an insulating material sheet on the opposite surface of the insulating layer 10 from the release layer 20 using an adhesive layer, the release layer 20, the insulating layer 10, and the conductive layer 40 can be integrated.

[0018] An example of the method for forming an electrostatic pattern is shown below. This method applies the high-definition electrostatic printing method (refer to the specification of Japanese Patent Application No. 2018-188998) proposed by the inventors. A master plate including a plate layer on which a relief plate, intaglio plate, or gravure plate-shaped pattern is formed and a first electrode, and a substrate S including a release layer 20, an insulating layer 10, and a conductive layer 40 serving as a second electrode are used. The plate layer of the master plate is brought into close contact with the release layer 20 of the substrate S, and an appropriate voltage sufficient to discharge the gap between the pattern of the plate layer and the release layer 20 is applied between the first electrode of the master plate and the second electrode of the substrate S, thereby forming an electrostatic pattern corresponding to the pattern of the plate layer on the release layer 20 of the substrate S.

[0019] Another example of the method for forming an electrostatic pattern is shown below. This method applies the electrostatic printing method (refer to the specification of Japanese Patent Application No. 2021-132875) proposed by the inventors. A mask sheet made of only a conductive material or a laminate of an insulating material and a conductive material and having a predetermined ion-permeable opening, and a substrate S including a release layer 20, an insulating layer 10, and a conductive layer 40 serving as a back electrode are used. The mask sheet is brought into close contact with the release layer 20 of the substrate S, and after ion irradiation through the mask sheet, the mask sheet is peeled off from the substrate S, thereby forming an electrostatic pattern corresponding to the ion-permeable opening and ion-shielding portion of the mask sheet on the release layer 20 of the substrate S.

[0020] Next, the electrostatic pattern is developed with electroplatable charged particles called toner, thereby forming electroplatable resin images 31 to 36 on the release layer 20. As the electroplatable charged particles, the liquid toner for electrophotography proposed by the inventors can be applied (refer to the specification of Japanese Patent Application No. 2019-209237). The liquid toner is advantageous for forming a high-resolution resin image as compared with a dry toner. This toner contains a resin having a functional group with a ligand function that incorporates a metal to form a complex. Examples of the functional group include an amino group, a carboxyl group, a hydroxyl group, and a thiol group. The resin images 31 to 36 formed on the release layer 20 by development have a function of adsorbing a catalytic metal or a catalytic metal ion.

[0021] FIG. 3 shows an example of the resin image transfer process in the case of FIG. 1, and FIG. 4 shows an example of the resin image transfer process in the case of FIG. 2. By using the substrate T itself as a mold and molding the substrate S on which the electroplatable resin images 31 to 36 are formed so as to be in close contact with the substrate T, the resin images 31 to 36 are transferred onto the substrate T. Examples of the method for molding the substrate S include vacuum molding and pressure air molding. Vacuum molding is a method of molding by heating and softening a substrate material and fitting it to a mold and then sucking it in a vacuum. Pressure air molding is a method of molding by heating and softening a substrate material and bringing it into close contact with a mold by pressure. Depending on the type and thickness of the substrate material, vacuum molding or pressure air molding is selected. In the example shown in FIG. 3 or FIG. 4, the substrate S made of polycarbonate with an insulating layer thickness of 0.3 mm is vacuum molded so as to be in close contact with the substrate T made of glass with a hemispherical surface in the central part and a flat peripheral part and a thickness of 0.5 mm, whereby the resin images 31 to 36 are transferred onto the substrate T.

[0022] Since the substrate T serves as a mold when molding the substrate S, heat resistance is required. Further, it may be made of any material as long as it has the surface properties (surface roughness, wetting index, etc.) necessary for the resin image to adhere. Examples include molded articles and laminates of materials such as thermosetting resins, UV curable resins, glass, and ceramics. Surface treatment of the substrate T (such as plasma treatment, corona treatment, coating of an adhesive layer, etc.) may be performed to improve the adhesiveness with the resin image.

[0023] FIG. 5 shows the electroless plating process. By immersing in a solution containing a catalytic metal, the catalytic metal is deposited only on the resin images 31 to 36 to impart catalytic ability. When the catalytic metal is adsorbed as ions, depending on the situation, an additional step of reducing and metallizing with hypophosphorous acid, formalin, etc. may be required. Examples of the catalytic metal include palladium, copper, gold, platinum, etc. After imparting catalytic ability to the resin images 31 to 36, by performing an electroless plating process, metal images 51 to 56 are formed on the resin images 31 to 36. In the example of FIG. 5, the substrate T on which the resin images 31 to 36 were transferred was treated with the following catalyst-imparting liquid, electroless nickel plating bath, or electroless copper plating bath.

[0024] [Catalyst-imparting liquid, electroless nickel plating bath, and electroless copper plating bath] The composition of the catalyst-imparting liquid is shown in the following table. TIFF2025102592000002.tif65116 The composition of the electroless nickel plating bath is shown in the following table. TIFF2025102592000003.tif39117 The composition of the electroless copper plating bath is shown in the following table. TIFF2025102592000004.tif46115

[0025] After the substrate T on which the resin images 31 to 36 were transferred was immersed in the above catalyst-imparting liquid at 40°C for 5 minutes and then washed with water at room temperature for 1 minute, the resin images 31 to 36 were imparted with catalytic ability. Next, the substrate T was immersed in an electroless nickel plating bath at pH 8.0 and 70°C for 10 minutes and then washed with water, whereby nickel images 51 to 56 were formed on the resin images 31 to 36. Alternatively, the substrate T was immersed in an electroless copper plating bath at 25°C for 12 minutes and then washed with water at room temperature for 1 minute, whereby copper images 51 to 56 were formed on the resin images 31 to 36. Both the nickel image and the copper image formed on the substrate T had a thickness of 0.5 μm and a line width of 10 μm, and there was no disconnection in the hemispherical surface portion and the portion where the transition from the hemispherical surface to the flat surface occurred.

[0026] If necessary, an electroplating treatment may be performed on the metal image formed by the electroless plating treatment to laminate the same or different metals on the metal image. By performing such an electroplating treatment, the properties such as the strength and conductivity of the entire metal image including the laminated portion can be improved. Industrial applicability

[0027] The present invention can be used in various industrial fields such as the commercial printing field in addition to the electronics field.

Explanation of reference numerals

[0028] 10: Insulating layer 20: Release layer 31: Resin image 32: Resin image 33: Resin image 34: Resin image 35: Resin image 36: Resin image 40: Conductive layer S: Substrate S T: Substrate T 51: Metal image 52: Metal image 53: Metal image 54: Metal image 55: Metal image 56: Metal image

Claims

1. (1) A step of forming a resin image capable of being plated on a flat substrate S (resin image forming step), (2) A step of transferring the resin image onto the substrate T by molding the substrate S so that the resin image surface of the substrate S adheres to the surface of the substrate T having a curved surface shape in whole or in part (resin image transfer step), (3) A method for forming a metal image, comprising a step of imparting catalytic ability to the resin image on the substrate T and performing electroless plating treatment (electroless plating treatment step).

2. The flat substrate S is composed of an insulating layer made of a thermoplastic resin film or sheet or a composite thereof and a release layer provided on one side of the insulating layer, and a resin image capable of being plated is formed on the release layer by a printing method. The method for forming a metal image according to Claim 1.

3. The flat substrate S is composed of an insulating layer made of a thermoplastic resin film or sheet or a composite thereof, a release layer provided on one side of the insulating layer, and a conductive layer provided on the opposite side of the release layer. First, an electrostatic pattern is formed on the release layer, and then the electrostatic pattern is developed with charged particles capable of being plated called toner, thereby forming a resin image capable of being plated on the release layer. The method for forming a metal image according to Claim 1.

4. Using an original plate provided with a plate layer on which a relief plate, intaglio plate, or gravure plate pattern is formed and a first electrode, and a substrate S provided with a release layer, an insulating layer, and a conductive layer serving as a second electrode, bringing the plate layer of the original plate into close contact with the release layer of the substrate S, and applying an appropriate voltage sufficient to discharge the gap between the pattern of the plate layer and the release layer between the first electrode of the original plate and the second electrode of the substrate S, thereby forming an electrostatic pattern corresponding to the pattern of the plate layer on the release layer of the substrate S. The method for forming a metal image according to Claim 3.

5. Using a mask sheet made of a molded body of only a conductive material or a laminate of an insulating material and a conductive material and having a predetermined ion-permeable opening, and a substrate S provided with a release layer, an insulating layer, and a conductive layer serving as a back electrode, bringing the mask sheet into close contact with the release layer of the substrate S, performing ion irradiation through the mask sheet, and then peeling the mask sheet from the substrate S, thereby forming an electrostatic pattern corresponding to the ion-permeable opening and ion shielding portion of the mask sheet on the release layer of the substrate S. The method for forming a metal image according to Claim 3.

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