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 a viewpoint of reliability and designability of a product in an application field of a substrate on which the metal image is formed because a conventional technique is based on a premise that thermoplastic resin is used as a substrate material.SOLUTION: A resin image is transferred on a substrate T of a curved shape by molding a substrate on which the resin image is formed using, as a mold, the substrate T itself that has been molded into a curved shape in advance such that the substrate adheres to the substrate T. Further, the resin image transfer surface of the substrate T is covered with a metal layer by a physical production method, and thereafter the resin image is removed together with the metal layer on the resin image, so that 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 6

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 substrate has 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. Then, a capacitive touch panel having a curved touch surface is produced by heating, softening, forming, and cooling the drawing flat plate (see, for example, Patent Document 1). Although disconnection due to forming is less likely to occur with conductive ink, there is a problem that it cannot be miniaturized into fine lines and its transparency is inferior compared to metal images because of its low conductivity. 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 a part of the transparent base material into a curved surface shape, a metal plating process 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 field of use, from the viewpoints of product reliability, designability, etc., there is a demand for substrates made of thermosetting resins, UV-curable resins, glass, ceramics, etc. having a curved surface shape on which a metal image is formed. 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 independent of the above two solutions (see the specification of Japanese Patent Application No. 2023-173918). 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 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 body. After coating the toner image transfer surface of the substrate T with a metal layer by a physical production method, the toner image is removed together with the metal layer on the toner image to obtain a metal image.

[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 not possible to obtain a substrate having a curved surface shape on which a metal image is formed. Therefore, as a result of intensive studies beyond the common sense of molding, the present inventors have found that if the substrate T previously molded into a curved surface shape is used as a mold and the substrate S on which a resin image 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 substrate T, and further, after coating the resin image transfer surface of the substrate T with a metal layer by a physical production method, the resin image is removed together with the metal layer on the resin image, so that a high-definition metal image can be formed on the curved surface substrate T made of a thermosetting resin, UV-curable resin, glass, ceramics, etc., and thus the present invention has been achieved.

[0008] The present invention provides a method for forming a metal image that solves the above problems. (I) (1) A step of forming a resin image on a substrate S having a flat plate shape (resin image forming step), (2) A step of transferring the resin image onto the substrate T by shaping 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 step of coating the surface of the substrate T onto which the resin image has been transferred with a metal layer by a physical production method (metal layer coating step), (4) A method for forming a metal image, comprising a step of removing the resin image together with the metal layer on the resin image (resin image removing 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 resin image is formed on the release layer by a printing method. The method for forming a metal image according to item 1 above, characterized in that. (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 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 called toner to form a resin image on the release layer. The method for forming a metal image according to item 1 above, characterized in that. (IV) Using an original plate provided with 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 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 item 3 above, characterized in that. (V) 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 having a release layer, an insulating layer, and a conductive layer serving as a back electrode are used. After bringing the release layer of the mask sheet into close contact with the substrate S and performing 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 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.

Effect 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. On the other hand, in the method of the present invention, by using the substrate T previously formed into a curved surface shape as a mold and molding the substrate S on which a resin image is formed so as to be in close contact with the substrate T, the resin image is transferred onto the substrate T. Further, after coating the resin image transfer surface of the substrate T with a metal layer by a physical production method, the resin image is removed together with the metal layer on the resin image to form a metal image. Therefore, a high-definition metal image can be formed on a curved 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

Figure 6

Embodiments 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 37 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. There is no particular limitation on the thickness of the insulating layer 10, and it may be determined in consideration of the conditions of the resin image transfer process.

[0013] In order to facilitate the transfer of the resin images 31 to 37 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 printing. For the printing method, ink containing a resin for forming the resin image is used. In the present invention, the resin images 31 to 37 need to be removed together with the metal layer thereon in the final step, and the material of the resin for forming the resin image and the solution used for removal are selected in combination with the solution (alkaline aqueous solution or organic solvent) used for removal. For example, if the resin for forming the resin image is mainly a polyvinyl acetate-based material, methanol may be selected as the solution used for removal.

[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 charged particles called toner, whereby resin images 31 to 37 are formed 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 may be composed of any conductive material such as metal, conductive oxide, carbon, graphite, conductive polymer, etc. The conductive layer 40 is disposed on the surface of the insulating layer 10 opposite to the release layer 20. The conductive layer 40 can play the above role if it is pressure-bonded to the insulating layer 10. However, if it is integrated with the release layer 20 and the insulating layer 10, it becomes easier to handle during the formation and development of the electrostatic pattern. The conductive layer 40 can be formed on the surface of the insulating layer 10 opposite to the release layer 20 by methods such as sputtering a metal film, a conductive oxide film, etc., or coating a conductive polymer film, etc., so that the release layer 20, the insulating layer 10, and the conductive layer 40 can be integrated. Alternatively, a sheet with a conductive layer 40 provided with a metal film, a conductive oxide film, a conductive polymer film, etc. on an insulating material sheet in advance can be laminated on the surface of the insulating layer 10 opposite to the release layer 20 using an adhesive layer, so that 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 (see the specification of Japanese Patent Application No. 2018-188998) proposed by the inventors. Using an original plate having a plate layer on which a relief plate, intaglio plate, or gravure plate pattern is formed and a first electrode, and a substrate S having a release layer 20, an insulating layer 10, and a conductive layer 40 serving as a second electrode, the plate layer of the original 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 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 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 (see the specification of Japanese Patent Application No. 2021-132875) proposed by the inventors. Using a mask sheet made of only a molded body of 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 having a release layer 20, an insulating layer 10, and a conductive layer 40 serving as a back electrode, the mask sheet is brought into close contact with the release layer 20 of the substrate S, 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-permeable opening and ion shielding portion of the mask sheet on the release layer 20 of the substrate S.

[0020] Next, by developing the electrostatic pattern with charged particles called toner, resin images 31 to 37 are formed on the release layer 20. In the present invention, the resin images 31 to 37 need to be removed together with the metal layer thereon in the final step, and the resin constituting the toner and the material of the solution used for removal are selected in combination with the solution (alkaline aqueous solution or organic solvent) used for removal. For example, if the resin constituting the toner is mainly a polyvinyl acetate-based material, methanol may be selected as the solution used for removal. As the toner, the electrophotographic liquid toner proposed by the present inventors can also be applied (see the specification of Japanese Patent Application No. 2019-209237). The liquid toner is advantageous in forming a resin image with high resolution as compared with the dry toner. The drying conditions immediately after development are 110°C for 3 minutes.

[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 molding die and molding the substrate S on which the resin images 31 to 37 are formed so as to be in close contact with the substrate T, the resin images 31 to 37 are transferred onto the substrate T. Examples of the method of 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 die and sucking it by vacuum. Pressure-air molding is a method of molding by heating and softening a substrate material and bringing it into close contact with a die by pressure. Vacuum molding or pressure-air molding is selected according to the type and thickness of the substrate material. The example shown in FIG. 3 or FIG. 4 uses a substrate S made of polycarbonate with an insulating layer thickness of 0.3 mm, and the substrate S is vacuum molded so as to be in close contact with a 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 37 are transferred onto the substrate T.

[0022] Since the substrate T serves as a molding die 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. For example, molded products and laminates of materials such as thermosetting resins, UV-curable resins, glass, and ceramics can be mentioned. Surface treatment (plasma treatment, corona treatment, coating of an adhesive layer, etc.) of the substrate T may be performed to improve the adhesiveness with the resin image.

[0023] FIG. 5 shows the metal layer coating process. The surface of the substrate T on which the resin images 31 to 37 are transferred is coated with a metal layer 50 by a physical production method. The physical manufacturing method, namely PVD (Physical Vapor Deposition), is a film-forming method that utilizes physical phenomena in a vacuum and is classified into sputtering methods (such as DC sputtering method, DC magnetron sputtering method, RF sputtering method, RF magnetron sputtering method, etc.), vacuum evaporation methods (such as resistance heating method, electron beam heating method, etc.), and ion plating methods (such as activated reactive evaporation method, high-density plasma assist evaporation method, etc.). When forming a metal layer, from the perspective of film-forming speed, the DC magnetron sputtering method or the vacuum evaporation method is preferred. Before forming the metal layer, surface modification of the surface to be coated with the metal layer may be performed by plasma treatment or the like.

[0024] Figure 5 shows an example using the DC magnetron sputtering method as the physical manufacturing method. A copper target was set on the cathode of the DC magnetron sputtering apparatus, and the substrate T was attached to the substrate holder. After evacuating the film-forming chamber to 10 -4 Pa, argon gas was introduced and adjusted so that the pressure became 0.2 Pa. After applying a voltage to the cathode to perform sputtering, the film-forming chamber was broken and the substrate T was taken out. The resin images 31 to 37 on the substrate T and the surface of the substrate T without the resin image were all coated with the copper layer 50.

[0025] Figure 6 shows the resin image removal process. The resin images 31 to 37 on the substrate T are removed together with the metal layer 50 on the resin image. As a result, the metal layer 50 that directly coated the substrate T remains, and metal images 51 to 56 are formed. In the example of Figure 6, after immersing in methanol for 1 minute while applying ultrasonic vibration to remove the resin images 31 to 37 together with the metal layer 50 on the resin image, it was washed with water for 1 minute. The copper images 51 to 56 formed on the substrate T had a thickness of 100 nm and a line width of 50 μm, and there were no disconnections in the hemispherical surface portion and the portion where it smoothly transitions from the hemispherical surface to the flat surface.

[0026] If necessary, electroless plating treatment, or electroless plating treatment and electroplating treatment may be performed on the metal image formed by the above method to laminate the same or different metals on the metal image formed by the above method. By performing such electroless plating treatment, or electroless plating treatment and electroplating treatment, the characteristics 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 37: 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 on a substrate S having a flat plate shape (resin image forming step), (2) A step of transferring the resin image onto the substrate T by forming the substrate S 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 step of coating the surface of the substrate T onto which the resin image has been transferred with a metal layer by a physical production method (metal layer coating step), (4) A method for forming a metal image, comprising a step of removing the resin image together with the metal layer on the resin image (resin image removing step).

2. 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 resin image is formed on the release layer by a printing method. The method for forming a metal image according to claim 1.

3. 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 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 called toner to form a resin image 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. 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, an insulating layer, and a conductive layer serving as a back electrode are used. The mask sheet is brought into close contact with the release layer of the substrate S, ion irradiation is performed through the mask sheet, and then the mask sheet is peeled off from the substrate S, thereby forming an electrostatic pattern corresponding to the ion-permeable opening and the ion-shielding portion of the mask sheet on the release layer of the substrate S. The metal image forming method according to claim 3, characterized in that.

Images