Apparatus and method for forming metal patterns on three-dimensional resin molded objects

Abstract

To provide an apparatus and method for forming three-dimensional molded objects using a 3D printer while enabling the formation of electrical circuits using metallic copper, such as MID (Molded Interconnect Device, molded circuit component), on the surface thereof, as well as decorative patterns using various metals.SOLUTION: A device using platable resin ink in a 3D printer apparatus forms patterns layer by layer and forms metal patterns by electroless plating after performing a pretreatment with a catalytic metal salt solution after three-dimensional resin molding.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention relates to the three-dimensional modeling technology of 3D printers, and the formation of metal patterns involves electroless plating technology. [Background technology]

[0002] In recent years, two different technologies with different purposes have been put into practical use in the manufacturing process of three-dimensional objects. One is called MID (Molded Interconnect Device), which is a technology to manufacture three-dimensional objects by injection molding and form electrical circuits on the surface of the three-dimensional object. The other is called 3D printing, which is a technology to manufacture three-dimensional objects by stacking various materials in layers according to digital data. MID technology is intended to mass-produce objects of the same shape, and is not cost-effective for small-scale production such as development prototypes. On the other hand, 3D printing technology requires time to output because it is manufactured by stacking layers, so it is not suitable for mass production, but it has the advantage of being able to grasp an image close to the actual object during the prototype development stage. For industrial purposes, it is starting to be widely used because it can solve design and processing assembly problems in a short period of time without incurring labor costs, and in recent years, unique objects made by 3D printers have begun to be sold as products.

[0003] Although the two started with different objectives, in recent years, attempts have begun to incorporate electrical circuits into 3D printers. However, the content of these attempts is completely different from what MID aims for. While MID is premised on placing electrical circuits on the surface of a three-dimensional shape, proposed methods for 3D printing include embedding electrical circuits, including electrical components, inside a three-dimensional object, or creating the printed circuit board itself with a 3D printer and then printing the case to mount it in as a single unit.

[0004] It is said that the first time an electrical circuit was formed using a 3D printer was in 2015, when the method used was to use silver paste as the conductive material, which was patterned using a dispenser. An electrical circuit was formed on the surface of the model resin layer as it was being formed, and then electrical components were manually attached. After the electrical components and circuit were bonded together, they were then embedded in resin for modeling. Since then, several methods have been proposed, but all of them use a dispenser or inkjet to create the electrical circuit pattern, using conductive ink containing silver particles to form the electrical circuit directly on the resin. A distinctive feature of these methods is that electricity is ultimately passed through the circuit as is. Each of these proposals can be said to be committed to a method that can only be achieved with a 3D printer.

[0005] However, considering the complexity and the stability of the electrical circuit quality, it is difficult to see the prospect of commercializing these technologies. The method of forming electrical circuits directly on resin using conductive ink containing silver particles is by no means a new method. It was also attempted in the conventional manufacture of printed circuit boards, but is now only used in special cases. In other words, the reality is that it has not been accepted as a method for use in electrical circuits in products.

[0006] MID was originally a technology aimed at forming electrical circuits on the surface of injection molded products, and technological development was carried out on the premise of mass-produced products with the same performance as 2D printed circuit boards. Therefore, from the beginning, the goal was to form electrical circuits using metallic copper, and various manufacturing methods were developed. All of these metallization methods form electrical circuits using electroless copper plating technology. The reason for using electroless plating is that it is possible to plate insulating materials, but in order for this to work, a catalytic metal must be present on the surface of the material to be plated. Moreover, plating on areas other than the circuit is problematic. Therefore, the difference between the manufacturing methods proposed is how to create a circuit pattern on the seed layer, which is necessary for electroless plating, that is, the part containing the catalytic material.

[0007] As mentioned above, 3D printers used for industrial purposes are required to fulfill two different roles. One is to check for problems in design, function, and manufacturing in the early stages of product development, and the other is to create the 3D model as a product. However, in both cases, product quality is required. In that sense, the current method of manufacturing electrical circuits using 3D printers may be acceptable for personal hobbies, but for industrial use, it is difficult to be accepted on the market, either for confirmation or as a practical product, unless the electrical wiring is made of metal copper like a printed circuit board. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Application No. 2019-209237 [Patent Document 2] Patent No. 4278430 [Patent Document 3] Patent No. 4863715 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to create a method for forming a metal pattern on the electrically insulating surface of a three-dimensional object using a 3D printer device, and for making the metal pattern into a pattern of metallic copper or the like similar to that of a normal printed circuit board. Although the most common demand in the market for forming a surface metal film is thought to be for electrical circuits, there are also cases where it is required for decoration, so here the term "metal pattern" is used as a general term to mean a patterned metal film. The first challenge is how to realize a metal copper pattern on a three-dimensional object. Another challenge is to take advantage of the features of 3D printers and find a way to form the parts that function as metal patterns at the same time as forming the layers of the object, rather than adding a pattern function after the object is completed as with MID. Furthermore, for practical use, the mechanism must not be complicated and manufacturing and running costs must be low. [Means for solving the problem]

[0010] The present invention relates to a 3D printer device that uses a means for patterning with a resin other than the resin used for modeling during three-dimensional modeling, a means for metallizing the resin pattern, and a material and means that enable both patterning and metallization, as well as a method for forming a metal pattern on the surface of a three-dimensional resin model produced by the device. The method of patterning uses a device that injects liquid resin, and the resin material used for patterning is a special resin that does not contain metal, for stable injection and low running costs. This special resin is characterized by being composed of resin molecules that have the ability to bond with catalytic metals normally used in pre-plating treatment, making plating possible, and henceforth this special resin will be referred to as "platable resin." Then, instead of forming a pattern using the plateable resin after completing the three-dimensional modeling, a pattern is formed for each layer modeled. The means of metallizing the plateable resin pattern is electroless plating technology. After 3D modeling, a separate process is performed to pre-treat the plateable resin parts with a catalytic metal, and then electroless plating is performed to form the desired metal pattern. Effect of the Invention

[0011] The present invention has three or more advantages over the 3D printer method of creating electrical circuits using conductive ink as described above, and the MID method of creating electrical wiring in injection molded products. One benefit is that it enables complete early model verification during MID product development. The second benefit is the low running costs. The third benefit is that it becomes possible to form complex electrical circuits that would be impossible with MID. Furthermore, this has the effect of being fully adaptable to future 3D printer methods that will enable molding using the actual resin used in the product, rather than the conventional resins for 3D printers that have recently become available. To explain a bit more specifically,

[0012] The final process is finished with electroless plating, which creates the same metallic copper electrical circuit as MID products. Therefore, for example, confirmation and evaluation of MID development and metal decoration product development can be done reliably at low cost and in a short period of time. By simply adding an inkjet-like resin ejection device and plateable resin ink to a conventional 3D printer, it is possible to create a device that can produce metal patterns on three-dimensional objects. Furthermore, the plateable resin ink for metallization itself is made of a resin composition that does not contain metal, so ejection stability is achieved by the device, and since it does not contain precious metals, the resin ink itself is inexpensive and running costs are kept low. In addition, because patterns are formed for each layer during 3D modeling, it is possible to form metal films on the surfaces of intricate shapes, inside holes, or on the inner surfaces of cylinders, making it possible to produce metal wiring and metal films in shapes that are impossible to produce using current MID methods. Furthermore, this means and method can be used regardless of what type of resin the 3D printer handles, as long as the method involves forming a modeling pattern using a device that digitally ejects or injects resin and layering it to create a three-dimensional resin model by adapting the plateable resin ink. [Brief description of the drawings]

[0013] [Figure 1] Figure 1 shows a plateable resin toner that has been patterned and thermally fixed onto a PET film before plating (the toner resin is transparent, so the photo was taken from diagonally above). [Diagram 2] Figure 2 shows the state of the PET film with the toner pattern in Figure 1 after it was immersed in an aqueous palladium chloride solution and then electroless copper plating was performed (numbers indicate line width in μm). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention is an apparatus and method for forming a metal pattern on a three-dimensional resin object using a 3D printer that produces three-dimensional resin objects, and is realized using a three-step process. (1) A process in which a plateable resin ink device is added to a conventional 3D printer for resin modeling to eject the plateable resin ink layer by layer and form a pattern to produce a three-dimensional resin model with a plateable resin pattern on the surface. (2) a pretreatment step in which, after all layers have been modeled using the device, only the resin patterned with the plateable resin ink is bonded to a catalytic metal; (3) A process in which the target metal is revealed on the bonded catalytic metal portion by electroless plating.

[0015] The process of (1) is a process for producing a three-dimensional resin model with a pattern made of plateable resin on the surface by a 3D printer device configured according to the present invention. The contents of the plateable resin ink used in the device and the reason why it is plateable, as well as specific means for linking and operating the device for forming the pattern with the plateable resin ink with the layer resin modeling means in various 3D printers for resin modeling, are explained.

[0016] The plateable resin ink is composed of a resin that has the ability to bond with catalytic metals, and although the ink itself does not contain any metals, it is a resin material to which catalytic metals can be added later, resulting in the formation of a metal pattern by electroless plating. The use of this plateable resin ink is one of the important points of the present invention. Resins that have the ability to bond with metals are chemically equivalent to resins that have ligands. According to chemistry textbooks, a compound with a structure in which metal and nonmetal atoms are bonded is called a complex. In a complex, the ions or molecules that are coordinated to the central atom are collectively called ligands. The atoms that can be coordinated are carbon, nitrogen, oxygen, halogens, phosphorus, arsenic, sulfur, etc., and it is said that all of them have lone pairs of electrons. Among ligands, those with one atom that coordinates to the metal are called monodentate ligands, and those with multiple atoms are called multidentate ligands. Multidentate ligands are also called chelating ligands, and the more ligands there are, the stronger the binding force with the metal. In the field of organic chemistry, complexes are very often used as catalysts to control or promote chemical reactions. To give a famous example, in 210, Akira Suzuki (Professor Emeritus at Hokkaido University), Eiichi Negishi (Distinguished Professor at Purdue University), and RF from the United States won the Nobel Prize in Chemistry for realizing a cross-coupling reaction using a phosphine-based palladium complex as a catalyst.

[0017] In other words, if the ink is made primarily of a resin that has ligands that bond with catalytic metals used for plating, it will bond with the catalytic metal when immersed in an aqueous solution of catalytic metal salt, which is commonly used as a pretreatment for plating, and the catalytic effect will make electroless plating possible. In Patent Document 1, the inventors have applied the above-mentioned principle and shown that a metallic copper pattern can be obtained by using a plateable resin. Specifically, the inventors applied the principle to a liquid developer for electrophotography, and produced a liquid toner using a resin dimethylaminoethyl methacrylate having a ligand in the toner. The inventors confirmed that a toner pattern was formed by electrophotography, and that a copper pattern could be formed by electroless copper plating after immersion in an aqueous palladium chloride solution. For reference, photographs taken at that time are shown in Figures 1 and 2. Figure 1 is a photograph of a pattern developed on a PET film using a plateable resin toner and thermally fixed before plating. Since the toner is transparent, black paper was placed under the film and the photograph was taken from above at an angle. It can be seen that the toner does not contain metals. Figure 2 is a photograph of the PET film on which the toner pattern in Figure 1 was developed and fixed, and then electroless copper plating was performed after immersion in an aqueous palladium chloride solution. The numbers indicate the line width in μm, and it can be seen that a line width of 5 μm was also plated.

[0018] However, the idea of ​​applying such plateable resins to electroless plating was not new. A search of past documents reveals examples of similar applications to inkjet inks in Patent Documents 2 and 3. Specific resin molecules used in these applications include 2-ethyl-4-methylimidazole and imidazole trialkoxysilane. Toners and inks are mixed with various resins and solvents depending on the purpose, so the resin composition is selected taking into consideration the affinity with these materials. Patent Document 2 uses an alcohol solvent for imidazoles, Patent Document 4 uses a water solvent for azole silane coupling, and Patent Document 1 disperses an amine compound in an isoparaffin solvent. This shows that resins suitable for electroless plating are not limited to these. In essence, it is the resin's ligands, such as imidazole molecules or amine molecules, that make it possible to plate.

[0019] The bond between these coordinated resins and the catalytic metal is very strong, so if the ink resin has adhesive properties to the substrate, the plated metal pattern will not peel off easily from the substrate. If you want to make the ink even more adhesive to the substrate, you can make the resin ink curable by ultraviolet light or heat. After that, further hardening and adhesion can be achieved by heat treatment at 80°C to 150°C after lamination or electroless plating. Although some resins are effective at temperatures below 80°C, a long heating time is required to achieve the desired effect, making it impractical. In addition, many modeling resins may soften at temperatures above 150°C, so it is best to avoid this, even for a short time.

[0020] The type of 3D printer device equipped with a device for ejecting the above-mentioned plateable resin ink in a pattern is for resin modeling and is equipped with a nozzle or ejection device that ejects modeling resin for each layer of modeling, or a device that bonds and solidifies (including semi-solidifies) the modeling resin, and a method is selected in which each of the nozzles or devices is operated to repeat additive modeling.

[0021] The form of the resin material used in the selected 3D printer for resin modeling can be classified as liquid, powder, solid, or thermally molten. Furthermore, there are currently four names for modeling methods depending on the form of the material and the method of modeling. These methods are commonly called Material Jetting, Binder Jetting, MEX (FDM), and PBF (Powder Bed Fusion). The method known as Material Jetting involves using an inkjet-like device to eject liquid resin material according to a modeling pattern to form layers, which are then solidified with ultraviolet light, etc., and repeatedly laminated. The method known as Binder Jetting involves forming a uniform layer of resin material in powder form, then injecting a binder resin onto that layer in a desired pattern using an inkjet-like device, while simultaneously curing the binder with ultraviolet light or other means to solidify it into a pattern, and repeatedly stacking the layers. MEX (FDM) is a method in which a thermoplastic resin material that is solidified into a filament at room temperature is softened by a heated nozzle and ejected layer by layer, shaping it according to a modeling pattern, solidifying it by exposing it to room temperature, and then repeatedly layering the material. A method called PBF (Powder Bed Fusion) involves forming a uniform layer of resin material, which is a powdered solid, and then repeatedly stacking the powder by irradiating it with a laser according to the modeling pattern data to melt and solidify it. In any of the above four methods, by adding a device that ejects plateable resin ink in a pattern and providing a means for forming a plateable resin pattern for each layer formation, it is possible to create an apparatus for producing a three-dimensional resin object with a plateable resin pattern formed on the surface.

[0022] There are two specific means for patterning plateable resin for each layer using the various 3D printers mentioned above. One is a means that is applicable to all four of the modeling methods mentioned above, and is a means for forming a pattern by operating a plateable resin device after a layer of modeling resin is formed. The other is a means that is applicable to a type of method such as Material Jetting, in which the modeling resin itself is injected into a pattern by a device and solidified, or a type of method such as Binder Jetting, in which the modeling resin is a powder, and a binder is injected into a pattern by a device to bind and solidify the powder. Since these modeling devices have the same injection function as the plateable resin device, a means can be used to operate the modeling resin device and the plateable resin device together or in sync.

[0023] A method that can be applied to all four modeling methods is a method in which the plateable resin ink device operates after the modeling resin has finished forming one layer and before moving on to the formation of the next layer, to form a pattern using the plateable resin ink. However, this method operates with a time difference from the modeling resin device, so there is a disadvantage that the manufacturing time is longer than that of conventional devices that only use resin modeling, due to the operation time of the plateable resin ink device. In this case, the thickness of the resin ink that can be plated can be very thin, and in the extreme, it is sufficient if it can be formed uniformly with even a single layer of resin molecules. Therefore, the resin composition of the resin ink that can be plated is The molecular weight of the resin does not need to be large, and it is desirable for the liquid viscosity to be low. However, since the plateable resin pattern is ultimately formed only on the surface of the three-dimensional model, the original modeling resin is not layered on top of the pattern. Therefore, the thickness of the plateable resin is not an issue, so there is no need to insist on a thin layer. In addition, since the plateable resin needs to have adhesive strength to the modeling resin, it is preferable for it to have ultraviolet or heat curing functions, and if possible, it is desirable for it to have both curing functions.

[0024] In the case of the Material Jetting method and the Binder Jetting method, the device for plateable resin can be operated integrally or synchronously with the device for modeling resin, so the disadvantage of the long manufacturing time described above can be eliminated. The composition of the plateable resin ink used at that time can be the same as that of the ink that is applicable to all four modeling methods, but it can also be a resin composition that has almost the same type of resin and function as the composition of the modeling resin, and further has a group that has the function of bonding with catalytic metals added to the resin, or a resin that has the function of bonding with catalytic metals added to it. In that case, the means and method of the present invention can be fully applied to a new 3D printer method called Multi Jet Fusion, which is capable of high-speed manufacturing equivalent to injection molding with thermoplastic resins used in injection molding that have been recently proposed.

[0025] Now, let us explain the pre-treatment process (2). Since the patterned resin does not contain catalytic metal, pre-treatment to add catalytic metal is necessary. Pre-treatment is carried out as a separate process after the three-dimensional object is completed, just like the next plating process. We do not use the conventional special pretreatment agents that are usually used when electroless plating resins. The reason is that the catalytic metal adsorption function of the pretreatment agents used in conventional resin plating is different from that by ligands, and is devised so that the catalytic metal can be adsorbed to many types of resins, so selective plating on only patterned resins that can be plated is not possible. The pretreatment method used in the present invention is a method commonly used for electroless plating of conventional metals, such as nickel plating on copper and gold plating on nickel. The commonly used method is a method of pretreatment with an activation solution, such as an aqueous palladium chloride solution or an aqueous palladium sulfate solution. In this pretreatment, the catalytic metal cannot be applied to ordinary resins, i.e., resin parts that do not have ligands that bind with the catalytic metal, so the catalytic metal binds only to resin parts that have ligands that bind with the catalytic metal, making the resin ready for electroless plating. Palladium is the most commonly used catalytic metal, but other metals used in electroless plating can also be applied to the present invention. The use of such general-purpose catalytic metal materials offers cost benefits, and the catalytic metal molecules in the aqueous solution are bound only to the patterned surface layer, and all of them act on the plating metal, eliminating waste, which offers additional cost benefits.

[0026] In the step (3), electroless plating is used as a means of expressing the target metal on the catalytic metal part bonded after pretreatment. This method is an established technology that is widely used in the formation of copper wiring for conventional printed circuit boards and MIDs, so an explanation of it is omitted here. The above explanation has focused on electrical wiring made of copper metal, which is thought to be the most important and most desired object for patterning metal on resin, but any type of metal that can be electrolessly plated can be used, and it is natural that various types of metal can be used for decorative purposes.

Claims

1. A 3D printer for producing three-dimensional resin objects, A plateable resin device for injecting a plateable resin ink is provided separately from the extraction nozzle or resin injection device for forming a layer shape using the modeling resin, The nozzle for extraction or the device for injecting resin and the device for injecting plateable resin are operated for each layer to form a modeled resin layer and a patterned layer of plateable resin; The plateable resin ink does not contain metal, has a photocurable or heat curable function, or has both photocurable and heat curable functions, and contains a resin having a multidentate ligand capable of forming a metal complex in part of the resin that constitutes it, which is a 3D printer device capable of producing three-dimensional resin objects having a plateable resin pattern formed on the surface.

2. Using the 3D printer device according to claim 1, After manufacturing a three-dimensional resin object having a plateable resin pattern formed on the surface thereof, a pretreatment step using an aqueous solution of a catalytic metal salt for adsorbing a catalytic metal or catalytic metal ions onto the plateable resin pattern on the surface of the three-dimensional resin model; A method for forming a metal pattern, comprising the steps of performing an electroless plating process after the pretreatment process, thereby forming a plating metal only on the plateable resin pattern on the surface of the three-dimensional resin model.

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