Method for manufacturing partially plated products, and partially plated products

Abstract

To provide a method for manufacturing partially plated products and partially plated products that can improve the working environment for people and allow the masking agent to be removed quickly even with a release agent that is safe for the human body after the plating process. [Solution] An oil-based ink mainly composed of rosin resin and alcohols is used as a masking agent to form a coating layer 20 on the plating base material 10. By volatilizing the alcohols from the coating layer, a solidified film 30 mainly composed of rosin resin is formed. Furthermore, a plating layer 50 is formed on the parts of the plating base material without a solidified film by a plating treatment using an acidic bath that does not dissolve the solidified film. Alcohols are less irritating to the eyes and have a less pungent odor than thinners, making them safer for the human body and improving the working environment. Moreover, a solidified film can be formed in a short time. In addition, the rosin resin forming the solidified film can be easily removed with alcohols.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a partially plated product in which a plating layer is formed on a part of the surface of a plating base material, and to a partially plated product. More specifically, it relates to a method for manufacturing a partially plated product in which a plating base material is masked with an oil-based ink having low eye irritation and pungent odor and not deteriorating the human working environment, and after the plating process, the masking agent can be peeled off in a short time with a peeling agent safe for the human body, and to a partially plated product.

[0002] More specifically, it relates to a method for manufacturing a partially plated product in which the masking agent is an oil-based ink mainly composed of ethanol that is safe for the human body and volatilizes quickly and rosin resin that can be easily peeled off with ethanol, and the plating process is performed with an acidic solution that does not dissolve the rosin resin, and to a partially plated product. In the present application, the acidic solution refers to a solution having a pH of 7.0 or less that does not dissolve the rosin resin.

Background Art

[0003] Conventionally, as a method for manufacturing a partially plated product, a method of masking a part of a plating base material and forming a plating layer only on the remaining part has been a well-known technique. There are mainly two methods for this well-known technique. The first method is a method of applying a masking agent made of a resin-based paint, and the second method is a method of covering the plating base material with a heat-shrinkable tube, a masking tape, or the like. The invention of the present application is a technique belonging to the first method.

[0004] The first method has the advantage that when applied by an operator, masking is possible even on a complex uneven surface, and according to silk screen printing or the like, a precise mask can be formed like a circuit pattern on a printed circuit board. However, in the first method, there is a problem that it is necessary to peel off the masking agent with an organic solvent such as thinner after plating.

[0005] Incidentally, plating factories have a mix of production lines for acidic bath plating and alkaline bath plating. Since it is prohibited to discharge organic solvents as they are, masking agents that can be removed with a common stripping agent (organic solvent) used in both acidic and alkaline baths are selected to simplify wastewater treatment.

[0006] However, resin-based plating coatings that are resistant to both acids and alkalis use thinners, which are primarily composed of highly toxic substances such as toluene, xylene, methanol, ethyl acetate, and methyl ethyl ketone, as organic solvents. As a result, they cause strong eye irritation and pungent odors, leading to a deterioration of the working environment and contributing to health problems among workers.

[0007] Furthermore, the aforementioned resin-based coating for plating has high viscosity to prevent dripping. As a result, the coating layer is thick, and it takes several hours to half a day for the coating layer to harden and dry. Moreover, when the base material for plating is a three-dimensional object such as a machine part, even if the object simply falls over while the coating layer is still hardened, the coating layer can come into contact with the workbench or other surface and peel off, resulting in a defective product. Therefore, the base material for plating must be kept upright and still, which makes the work environment poor.

[0008] Herein, we will explain the drying state of the coating layer. In this application, the drying state of the coating layer conforms to the Japanese Industrial Standards General Test Methods for Paints (JIS K 5600). Specifically, cured drying is defined as "a state in which, when the center of the coated surface is firmly pinched between the thumb and index finger, no indentation from fingerprints is left on the coated surface, no movement of the coating film can be felt, and when the center of the coated surface is rapidly and repeatedly rubbed with the fingertip, no scratches are left on the coated surface." Hereafter, the uncured state of the applied masking agent will be referred to as the coating layer, and the cured and dried state will be referred to as the solidified film, and these terms will be used to distinguish between the two.

[0009] As mentioned above, the aforementioned resin-based coating for plating tends to form a thick solidified film, and even when immersed in thinner stored in a cleaning tank and subjected to ultrasonic cleaning, it took more than 20 minutes to remove the solidified film. Moreover, even after ultrasonic cleaning, the solidified film often remained partially attached, requiring workers to scrub it off with brushes or cloths.

[0010] Therefore, when covering simple-shaped parts such as the shaft of a piston, the second method using heat-shrink tubing was actually superior in terms of workability. However, the second method had the drawback that pinholes could occur when the heat-shrink tubing was heated, potentially leading to product defects due to the formation of a plating layer in the pinhole areas, and that it could only be applied when the masking area had a simple shape.

[0011] Patent Document 1 discloses a partial plating method patented by the present applicant. According to the technology described in this document, a specific example is disclosed in which the masking agent is a plating resin coating consisting of an inert hydrocarbon derivative, a colorant, and hydrogenated petroleum naphtha (toluene, xylene, etc.), and the stripping agent is a thinner contained in the masking agent.

[0012] However, even with this technology, both the masking agent and the release agent were paint thinners with strong irritants to the eyes and a pungent odor. Toluene and other substances contained in paint thinner are excellent solvents because they can dissolve a wide range of resins, but they are also highly toxic and addictive, posing a problem as workers could experience acute poisoning symptoms even with thorough ventilation. Furthermore, because the solidified film was thick, the removal process took 10 to 30 minutes, and this technology failed to solve the problem of the removal process being time-consuming.

[0013] Patent Document 2 discloses a technology for an ultraviolet-curable resin composition for plating resists (hereinafter simply referred to as "paint"). According to this technology, the paint is applied to a plating base material by a screen printing method or the like to form a coating layer of a desired shape, and then the coating layer is cured by irradiation with ultraviolet light. Furthermore, a specific example is disclosed in which the thickness of the coating layer is 12 μm and an aqueous sodium hydroxide solution is used as a release agent.

[0014] However, according to the technology described in this document, it is necessary to irradiate the paint with ultraviolet light to cure it. Therefore, when applying paint to multiple surfaces of a three-dimensional object, such as a machine part, irradiating with ultraviolet light from only one direction may result in the paint layer on the shaded surfaces remaining uncured. This necessitates multiple irradiations with ultraviolet light, creating a time-consuming and laborious process.

[0015] Furthermore, since the coating layer remains uncured until the cumulative amount of ultraviolet light reaches a predetermined level, when applying it to three-dimensional objects where screen printing is not possible, it was necessary to select a paint with a higher viscosity compared to printing on a flat surface to prevent dripping. Consequently, when this technology's paint was applied to the aforementioned three-dimensional objects, the coating layer tended to be thicker than that produced by printing, and the time required for peeling may also be longer.

[0016] The applicant re-examined various oil-based inks, which had not been conventionally used as masking agents because they were easily peeled off in many plating processes, and conducted extensive research. As a result, the applicant discovered that by combining an acidic bath plating process with oil-based inks that had previously only been used in writing instruments, it was possible to achieve both improved working conditions and fast drying and easy peeling of the masking agent, leading to the invention of the present invention. [Prior art documents] [Patent Documents]

[0017] Patent Document 1: Japanese Unexamined Patent Publication No. 2003-183877 Patent Document 2: Japanese Unexamined Patent Publication No. 2020-105549 [Overview of the project] [Problems that the invention aims to solve]

[0018] The problem that this invention aims to solve is to provide a method for manufacturing a partially plated product and a partially plated product, which involves masking the plating base material with an oil-based ink that has little eye irritation and pungent odor and does not worsen the working environment, and after the plating process, allows the solidified film to be removed in a short time even with a human-safe stripping agent. [Means for solving the problem]

[0019] The first aspect of the present invention is a method for manufacturing a partially plated product, comprising applying a masking agent to a part of the surface of a plated base material and forming a plating layer on the remaining part of the plated base material that is not masked, the method comprising four steps in order: the first step is a degreasing step of degreasing the surface of the plated base material; the second step is a coating step of applying an oil-based ink mainly composed of resin and solvent as the masking agent to the degreased part to form a coating layer; and the third step is a solidification film of which the solvent contained in the coating layer is volatilized to form a solidified film. The invention is characterized in that the formation process is a fourth step, which is a plating process in which the plating layer is formed only on the remaining portion where the solidified film has not been formed using an acidic bath; the coating process is a process in which an oil-based ink is applied, in which the main component of the resin constituting the oil-based ink is rosin resin and the main component of the solvent is ethanol which dissolves the rosin resin, thereby forming the coating layer; and the solidified film formation process is a process in which the solidified film, whose main component is the rosin resin, is formed with an average film thickness of 0.4 μm or more and 3.0 μm or less.

[0020] The degreasing in the first step is performed before applying the masking agent, so it can be either the well-known alkaline degreasing or electrolytic degreasing, and the degreasing method is not limited. The material of the plating base material can be a conductor, such as copper, brass, nickel, iron, or stainless steel, in the case of electroplating, and a non-conductor in the case of electroless plating. The conductor may be an article on which a plating layer has been formed on the surface. The plating base material is preferably a three-dimensional object such as a gear or piston, but is not limited to this, and may also be a flat plate-like object such as a printed circuit board.

[0021] In the second step, the application of oil-based ink is preferably done by impregnating a fibrous pen tip with the oil-based ink and applying it to the plated base material like a writing instrument. However, if the plated base material has a large flat surface, it may also be applied by a paint roller, screen printing, or spraying. The oil-based ink contains a resin and a solvent that form a solidified film, with rosin resin as the main component of the resin and ethanol as the main component of the solvent. As the ethanol evaporates from the coating layer, a solidified film mainly composed of rosin resin is formed on the plated base material.

[0022] Since almost all of the ethanol evaporates from the coating layer, the weight ratio of rosin resin to ethanol in oil-based inks is not limited. Furthermore, if the ethanol content relative to the total weight of the oil-based ink is, for example, 50% by weight or more, the viscosity of the oil-based ink decreases, making application easier and facilitating the formation of a thinner solidified film, which is preferable. A thin solidified film requires less time for curing and drying of the coating layer, and the solidified film is also easier to peel off.

[0023] Ethanol is soluble in rosin resin, is less likely to cause health problems for workers, and has a low environmental impact. In addition to rosin resin and ethanol, oil-based ink may also contain other components such as colorants (pigments / dyes), colorant dispersants, other resins, and other solvents. A specific example of such oil-based ink is an oil-based marking pen, which is a writing instrument.

[0024] In the third step, volatilization means that ethanol, which is a solvent, becomes a gas and is emitted from the coating film layer under normal temperature and pressure conditions. In the step of forming a consolidated film, a consolidated film with a film thickness of at least 0.4 μm or more may be formed. Ethanol can be volatilized from the coating film layer without heating or ultraviolet irradiation to form a consolidated film, and moreover, it has weaker eye irritation and pungent odor compared to thinner, and is less likely to cause health hazards.

[0025] The test results are shown in the examples. The consolidated film formed with the oil-based ink of the present invention had an average film thickness of about 0.4 μm. This is about one-thirtieth of the film thickness compared to Patent Document 2 described above, and when immersed in ethanol stored in an ultrasonic cleaning tank, the consolidated film could be removed in about 10 seconds. Regarding the film thickness of the consolidated film, it is described in detail in the examples together with electron micrographs.

[0026] In the fourth step, the plating treatment with an acidic bath may be, for example, electroless nickel plating treatment, electro-nickel plating treatment, electro-copper plating treatment, zinc plating treatment with a zinc chloride bath, or the like. In any case, since it is a plating treatment with an acidic bath, the consolidated film mainly composed of rosin resin is not dissolved in the plating solution. The plating treatment may include an activation treatment in which the plating base material is immersed in an acidic solution prior to immersion in the plating solution to roughen its surface in order to improve the adhesion between the plating base material and the plating layer.

[0027] According to the first invention, an oil-based ink mainly composed of rosin resin and ethanol is used as a masking agent, and only an acidic solution that does not dissolve rosin resin is used for the activation treatment and plating treatment of the plating base material. As a result, compared with the conventional resin coating material for plating, the curing and drying of the coating film layer are significantly faster, the production efficiency of the partial plating product can be increased, and it is less likely to cause health hazards to the operator, so that the working environment can be improved, which has an advantageous effect not found in the prior art.

[0028] The method for manufacturing a partially plated product according to the second invention of the present invention is the first invention, characterized in that the coating step is a step of applying the oil-based ink containing ethanol in a ratio of 50% to 90% by weight relative to the total weight of the oil-based ink, and in the solidification film formation step, the coating layer is formed by the volatilization of the ethanol within 1 minute without heating or ultraviolet irradiation.

[0029] According to the second invention, in the coating process, an oil-based ink containing ethanol in a proportion of 50% to 90% by weight is applied. Because the viscosity of the oil-based ink is low, a thin coating layer can be applied, and even in a room temperature environment, the ethanol can be rapidly evaporated from the coating layer, allowing a solidified film to be formed within one minute.

[0030] This eliminates the need for heating and UV irradiation for curing and drying the coating layer, thereby increasing the production efficiency of partially plated products. In this application, a room temperature environment refers to an environment of 20°C ± 15°C as defined in the Japanese Industrial Standard (JIS Z 8703).

[0031] The third invention of the present invention is a method for manufacturing a partially plated product, which is the second invention and includes a first control step for controlling the number of times the oil-based ink is applied in layers, wherein in the first control step, the number of times the application step and the solidification film formation step are performed is counted to be between 1 and 5 times, thereby controlling the average film thickness to be between 0.4 μm and 3.0 μm.

[0032] According to the third invention, similar to the second invention, the oil-based ink is an oil-based ink containing ethanol in a proportion of 50% to 90% by weight. Therefore, the viscosity of the oil-based ink is low, making it easy to control the average film thickness, and the coating layer can be cured and dried quickly.

[0033] Furthermore, by limiting the number of times the oil-based ink is applied in layers (hereinafter simply referred to as the number of applications) to a maximum of five times, the average thickness of the solidified film is controlled to 3.0 μm or less. As a result, the solidified film is kept thin, the total amount of ethanol evaporated during the solidified film formation process is reduced, and the amount of release agent used during the solidified film removal process is also reduced, making it easier to improve the working environment.

[0034] The fourth invention of the present invention is a method for manufacturing a partially plated product, the first invention, further comprising a second control step for identifying the application area of ​​the oil-based ink, wherein the second control step is included in any period from the application step to the start of the plating process, the application step is a step of applying the oil-based ink containing a colorant as a secondary component, and in the second control step, the application area of ​​the oil-based ink is identified by the coloring state of the coating layer or the solidified film.

[0035] According to the fourth invention, the area to which the oil-based ink has been applied can be identified by the coloring state of the coating layer or solidified film. This makes it easy and reliable to identify whether or not there are any areas where the masking agent has not been applied, thereby improving work efficiency and increasing the production efficiency of partially plated products. The color of the colorant is not limited, but black, blue, red, etc., which are easily visible when applied to a metal plated base material, are preferred.

[0036] The fifth invention of the present invention is a method for manufacturing a partially plated product, which is the first to fourth inventions and further includes a fifth step of peeling off the solidified film, wherein the fifth step consists only of immersing the partially plated product on which the plating layer has been formed in a stripping solution consisting of ethanol with a concentration of 90% by volume or more and ultrasonically cleaning it.

[0037] According to the fifth invention, the deconsolidation solution is an ethanol solution that is safe for the human body, and the concentration of ethanol in the deconsolidation solution is 90% by volume or higher. This improves the working environment for people during the deconsolidation process, and also has the advantage that the deconsolidation can be removed by immersion in an ultrasonic cleaning tank alone, eliminating the need for manual wiping by workers.

[0038] The sixth aspect of the present invention is a partially plated product comprising a metal plating base material, a masking layer, and a plating layer, wherein the masking layer is a solidified film whose main component is rosin resin and is provided exposed on a selected portion of the surface of the plating base material, and the plating layer is a nickel plating layer or a copper plating layer and is provided only on the remaining portion of the surface of the plating base material excluding the portion on which the solidified film is provided, and the average thickness of the solidified film is 0.4 μm or more and 3.0 μm or less.

[0039] According to the sixth invention, the masking layer is a solidified film containing rosin resin as its main component. Since the rosin resin hardens and dries due to the evaporation of ethanol, which is the solvent, the solidified film does not contain a photopolymerization initiator, unlike UV-curing resin paints, nor does it contain heat-cured resin, unlike heat-curing resin paints.

[0040] Because the solidified film has an average thickness of 0.4 μm or more, pinholes do not occur, thus preventing the production of defective products. While there is no upper limit to the average film thickness, a thickness of 5.0 μm or less is preferable as it reduces the amount of oil-based ink used. Furthermore, since rosin resin is easily dissolved even with ethanol, which is safe for humans, thin solidified films can be easily peeled off. This provides a significant advantage over conventional technologies: the ability to provide partially plated products that do not worsen the working environment for people.

[0041] The seventh invention of the present invention is a partially plated product of the sixth invention, characterized in that the plating base material is a machine part, and the solidified film is provided on multiple surfaces of the machine part.

[0042] According to the seventh invention, the plating base material consists of a three-dimensional mechanical part, and a solidified film, which serves as a masking layer, is provided on multiple surfaces of the mechanical part. The type of mechanical part is not limited and may be, for example, a gear, plug, piston, etc. Furthermore, the average thickness of the solidified film is set to 3.0 μm or less, which makes it easy to control the film thickness by the number of times the oil-based ink is applied. As a result, even for products in which a coating layer is formed on multiple surfaces of a mechanical part, it is possible to provide a partially plated product that has high workability without the need to pay attention to dripping and peeling of the coating layer during the drying period, and in which the solidified film can be easily peeled off.

[0043] The eighth invention of the present invention is a partially plated product of the sixth or seventh invention, characterized in that the solidified film contains a colorant as a secondary component. According to the eighth invention, because the solidified film is colored, it is easy to identify the area where the solidified film is formed. This makes it easy to detect if there are any masking defects in the plating base material, and thus facilitates quality control of the partially plated product.

[0044] The proportion of colorant contained in the solidified film is not limited, but it is sufficient if the masking area is visible, so the proportion may be lower than that of a typical oil-based marking pen. For example, if the proportion of colorant is 5% to 40% by weight relative to the weight of the rosin resin forming the solidified film, the rosin resin will be the primary component of the solidified film, making it possible to create a solidified film that is less prone to pinholes even with a thin film thickness, and that is also easy to see. [Effects of the Invention]

[0045] According to the first invention of this present invention, compared to conventional resin-based coatings for plating, the curing and drying of the coating layer is significantly faster, which can increase the production efficiency of partially plated products, and it is less likely to cause health problems for workers, thus improving the working environment. These are advantageous effects not found in conventional technology. According to the second invention of this invention, heating and ultraviolet irradiation are unnecessary for curing and drying of the coating layer, thereby increasing the production efficiency of partially plated products.

[0046] According to the third invention of the present invention, the solidified film can be controlled to be thin, the total amount of ethanol evaporated during the solidified film formation process can be reduced, and the amount of release agent used during the solidified film removal process can also be reduced, making it easier to improve the working environment. According to the fourth invention of the present invention, it is possible to easily and reliably identify whether or not there are areas where the masking agent has not been applied, thereby improving work efficiency and increasing the production efficiency of partially plated products. According to the fifth invention of the present invention, the working environment for people can be improved even in the process of peeling off the solidified film, and the solidified film can be peeled off by immersion in an ultrasonic cleaning tank alone, which has the advantageous effect of eliminating the need for wiping by workers.

[0047] According to the sixth invention of this invention, it is possible to provide partially plated products that do not worsen the working environment for people, which is an advantageous effect not found in conventional technology. According to the seventh invention of the present invention, even in products in which coating layers are formed on multiple surfaces of machine parts, it is possible to provide a partially plated product that has high workability without the need to pay attention to dripping and peeling of the coating layer during the drying period, and in which the solidified film can also be easily peeled off. According to the eighth invention of the present invention, it is possible to easily detect whether a masking defect has occurred in the plating base material, and quality control of partially plated products is facilitated. [Brief explanation of the drawing]

[0048] [Figure 1] Photograph of the selection test for oil-based ink (Example 1). [Figure 2] Electron microscope image of film thickness control test (Example 1). [Figure 3] Manufacturing process diagram for partially plated products (Example 1). [Figure 4] Cross-sectional diagram of a partially plated product (Example 1). [Figure 5] Photograph of a partially plated product (Example 1). [Modes for carrying out the invention]

[0049] In manufacturing partially plated products, an oil-based ink mainly composed of rosin resin and ethanol is applied to the plating base material to form a coating layer, and a solidified film mainly composed of rosin resin is formed simply by evaporating the ethanol from the coating layer. Furthermore, by performing a plating treatment with an acidic bath that does not dissolve the solidified film, a plating layer is formed only on the remaining parts of the plating base material where the solidified film has not formed. [Examples]

[0050] In Example 1, a partially plated product and its manufacturing method will be described with reference to Figures 1 to 5. Figure 1 shows a test photograph using an oil-based marking pen available on the market, with an oil-based ink resistant to acidic baths selected. Figure 1(A) shows a photograph of the oil-based ink applied to a copper plate, and Figure 1(B) shows a photograph after electroless nickel plating treatment using an acidic bath.

[0051] Figure 2 shows a photograph of the film thickness of the solidified film observed with an electron microscope. Figure 3 shows a manufacturing process diagram of the partially plated product. Figure 4 shows a cross-sectional explanatory diagram of the partially plated product corresponding to the manufacturing process diagram in Figure 3. Figure 5 shows photographs of partially plated products manufactured using three different plating processes.

[0052] (Selection test for oil-based inks) First, the selection test for oil-based inks will be explained with reference to Figure 1 and Table 1. In the selection test, ten types of oil-based marking pens provided by nine companies were used and applied to a copper plate forming the plating base material in a straight line to form a coating layer (see Figure 1(A)). After all the coating layers had hardened and dried to form a solidified film, electroless nickel plating was performed and the dissolution state of the oil-based inks was evaluated (see Figure 1(B)).

[0053] Here, two sets of test pieces with a coated film were prepared. To facilitate comparison of the state of the oil-based ink before and after plating, one set was left with the solidified film formed (see Figure 1(A)), while only the other set was plated (see Figure 1(B)). To prevent misinterpretation of the test results, the numbers corresponding to each ink shown in Table 1 were drawn on the copper plate using Ink 1 (rosin resin), which was confirmed in preliminary tests not to dissolve in acidic solutions.

[0054] The test was conducted within the applicant's plating factory. The application of the oil-based ink and its curing and drying conditions were carried out in a plating test chamber that was heated to approximately 25°C to simulate a normal room temperature environment. Each oil-based ink coating layer cured and dried within 1 minute, forming a solidified film. The time required for curing and drying of each coating layer was confirmed beforehand by applying the oil-based ink to a copper plate and then rubbing it with a finger to ensure that it did not adhere.

[0055] The bath composition per liter of electroless nickel plating solution was as follows: nickel sulfate: approximately 20 g / L to 25 g / L; sodium hypophosphate as a reducing agent: approximately 25 g / L to 30 g / L; sodium hydroxide as a pH adjuster: approximately 1.6 g / L; lactic acid as a complexing agent: approximately 27 g / L; propionic acid as an accelerator: approximately 2 g / L; and sulfur compound as a stabilizer: approximately 2 mg / L.

[0056] The plating bath conditions were adjusted to a bath temperature of approximately 90°C and a pH of approximately 4.0 to 5.0, with air being introduced into the plating solution for agitation. Here, the plating bath time was set to approximately 60 minutes so that the thickness of the electroless nickel plating layer would be approximately 5 μm. In addition, a known palladium colloidal solution was applied to a portion of the copper plate to serve as catalyst 40 (see Figure 4), which acts as the starting point for the formation of the electroless nickel plating layer.

[0057] Next, we will describe the 10 types of oil-based marking pens in detail. For inks 1 through 9, we used black oil-based marking pens, and for ink 10, we used a blue oil-based marking pen. Although the resin components were disclosed in the safety data sheet only for ink 1, detailed component analysis was omitted for the comparative examples of inks 2 through 10 because it was found that part or almost the entire solidified film dissolved, making them unsuitable as masking agents.

[0058] Ink 1 is the black ink used in the "Twin Marker" provided by Tombow Pencil Co., Ltd., and its main component as the resin forming the solidified film is rosin resin. Ink 2 is the black ink used in the "Mackie (registered trademark)" provided by Zebra Co., Ltd. Ink 3 is the black ink used in the "Magic Ink (registered trademark)" provided by Teranishi Chemical Industry Co., Ltd. Ink 4 is the black ink used in the "Oil-Based Marker" provided by Pilot Corporation. Ink 5 is the black ink used in the "Oil-Based Marker" provided by Pentel Co., Ltd.

[0059] Ink 6 is the black ink used in Sakura Color Products Corporation's "Name Pen". Ink 7 is the black ink used in Shachihata's "Artline (registered trademark)". Ink 8 is the black ink used in Cainz Corporation's "Oil-based Marker". Ink 9 is the black ink used in ASKUL Corporation's "Oil-based Marker". Ink 10 is the blue ink used in Tombow Pencil Co., Ltd.'s "Twin Marker".

[0060] [Table 1] TIFF2026100203000012.tif75158

[0061] (Evaluation of the state of the solidified film after plating) For inks 2 and 4 through 10, as shown in the photograph in Figure 1(B) and Table 1, it was confirmed that part or almost the entire solidified film dissolved in the electroless nickel plating solution, and therefore they did not function as masking agents. In the case of ink 3, exceptionally, almost the entire solidified film dissolved, but there were also parts where the plating base material was exposed. However, it is presumed that electroless nickel plating will precipitate in these exposed areas depending on the plating time, so it is not suitable as a masking agent. On the other hand, only the solidified film formed by ink 1, which mainly consists of rosin resin, showed excellent results with no dissolution at all.

[0062] The following tests and plating treatments were conducted by the applicant using an oil-based ink (hereinafter referred to as "this oil-based ink") prepared by mixing rosin resin and ethanol. This oil-based ink is prepared by mixing rosin resin manufactured by Hayashi Pure Chemical Industries, Ltd. and anhydrous ethanol (concentration 99.5 vol%) manufactured by Daishin Chemical Co., Ltd., such that the content of anhydrous ethanol is between 50% and 90% by weight relative to the total weight of this oil-based ink.

[0063] When mixing a colorant as a secondary component into this oil-based ink, mixing the colorant at a ratio of 5% to 40% by weight relative to the total weight of the rosin resin makes it easier to visualize the area where the solidified film is formed, and because the rosin resin is the primary component of the solidified film, pinholes are less likely to occur in the solidified film even if the film is thin. The material of the colorant can be any colorant soluble in ethanol, such as a known liquid alcohol dye, but is not limited to this, and may also be a pigment. The color of the colorant should be selected from easily visible colors such as black, blue, or red, depending on the base color of the plating substrate.

[0064] (Film thickness control test) In the film thickness control test, this oil-based ink, mixed with 70% by weight of anhydrous ethanol, was applied to a copper plate. The thickness of the solidified film was then imaged using an electron microscope to test how the thickness of the solidified film changed with the number of coats applied. The ink was applied to the copper plate using a felt-tip pen with replaceable ink cartridges, filled with this oil-based ink.

[0065] Figure 2 shows images of three different film thicknesses: one coat (Figure 2(A)), three coats (Figure 2(B)), and five coats (Figure 2(C)). Furthermore, for each coat count, the film thickness in areas with thin (branch number 1), average (branch number 2), and thick (branch number 3) areas is shown side-by-side.

[0066] [Table 2] TIFF2026100203000013.tif29146

[0067] (Evaluation of film thickness control tests) As shown in Table 2, in areas with an average film thickness (hereinafter referred to as average film thickness), the average film thickness increased in direct proportion to the number of coats applied. The same result was observed in areas with a thicker film. On the other hand, in areas with a thin film, the film thickness increased approximately in direct proportion to the number of coats applied when there were 3 coats, whereas when there were 5 coats, the film thickness became thinner compared to when there were 3 coats.

[0068] According to these test results, it was found that even with five or more coats, the work becomes complicated, and it may become difficult to control the average film thickness. Furthermore, as will be described in detail with Figure 5, no masking defects occurred even when the number of coats was limited to one. Therefore, in this invention, even with plating base materials such as machine parts that tend to require many coats, the number of coats is limited to five, thereby ensuring that the average film thickness of the solidified film is formed in the range of 0.4 μm to 3.0 μm, thereby stabilizing the quality of the solidified film and improving ease of work.

[0069] Although the electron microscope images and tables are omitted due to the complexity of the data, when the ethanol content was 80% by weight, the average thickness of the solidified film could be controlled to at least 0.40 μm by counting the number of coatings two or more times. Similarly, when the ethanol content was 90% by weight, the average thickness of the solidified film could be controlled to at least 0.40 μm by counting the number of coatings three or more times.

[0070] (Curing and drying test of the coating layer) In the coating layer curing and drying test, the time required for the curing and drying of the oil-based ink was verified by rubbing the coating layer with a fingertip at predetermined intervals to see if the ink adhered to the finger. In this test, the ethanol content of the oil-based ink was set to 70% by weight, and the curing and drying times of the coating layer were compared by varying the number of applications to the metal plate: 1, 3, and 5 times. Overcoating of the oil-based ink was performed before the lower coating layer had cured and dried. In addition, a black liquid alcohol dye was added to the oil-based ink to make it easier to check for adhesion to the finger.

[0071] [Table 3] TIFF2026100203000014.tif29146

[0072] When the ink was applied in a single coat, after 15 seconds, the oil-based ink did not adhere to the fingertip even when the coating layer was repeatedly rubbed. Therefore, using 15 seconds as a baseline, the curing state was verified by rubbing the coating layers applied at 5-second intervals. It was confirmed that a solidified film had formed after 20 seconds with three coats, and after 30 seconds even with five coats. Based on these test results, this oil-based ink is expected to significantly reduce the manufacturing time of partially plated products compared to conventional resin-based coatings for plating, which require several hours for curing and drying.

[0073] Next, the manufacturing process of partially plated product 1 will be explained with reference to the manufacturing process flowchart in Figure 3 and the explanatory diagrams of each stage of the partially plated product in Figure 4. In Figure 3, the main processes (S100 to S500) are shown with solid lines, and the optional processes (S10 and S20) are shown with dashed lines.

[0074] Figure 4(A) shows the base material 10 before the degreasing process. At this time, an oil film layer 11 remains on the surface of the base material 10. Figure 4(B) shows the coating process in which the oil-based ink is applied to the base material 10 from which the oil film layer 11 has been removed by degreasing to form a coating layer 20. Figure 4(C) shows the solidification film formation process in which ethanol evaporates from the coating layer to form a solidified film 30. Figures 4(D) and 4(E) show the plating process in which a palladium colloidal solution, which is the catalyst 40, is attached to the base material, and then immersed in an electroless nickel plating solution to deposit a plating layer 50. Figure 4(F) shows the cleaning process for cleaning the solidified film. Here, a specific example in which the base material 10 is a copper plate will be explained.

[0075] In step 100, the first step, the degreasing step, is performed to remove the oil film layer on the copper plate surface by known alkaline degreasing or electrolytic degreasing (S100). In step 200, the second step, the coating step, is performed to apply the oil-based ink to the surface of the degreased copper plate to form a coating layer 20 (S200). In step 300, the third step, the solidification film formation step, is performed (S300). Here, it is sufficient to leave the plate undisturbed for approximately 30 seconds at room temperature until ethanol evaporates from the coating layer 20 and a solidification film 30 is formed.

[0076] If the second and third steps are performed only once, proceed to step 20 (S20). On the other hand, if the steps are repeated multiple times, the first control step is to count the number of times the oil-based ink is applied and ensure that it is kept within five times (S10). In step 20, the area where the solidified film 30 has formed is identified by its coloring state (S20). Identification of the coloring state can be done by visual inspection by an operator, but it is also acceptable to use an inspection camera.

[0077] If the solidified film is formed within the appropriate range, the fourth step, the plating process, involves electroless nickel plating in an acidic bath (S400). If the range of solidified film formation is inappropriate, the process returns to the first control step (S10), where the oil-based ink is reapplied and the number of coats is counted and managed. The bath composition for the plating process will be described later with reference to Figure 5.

[0078] After the plating process is complete, the fifth step, the cleaning process, is performed to clean the solidified film (S500). In the cleaning process, the plated base material 10 after the plating process is immersed in an ethanol solution that generates ultrasonic vibrations to remove the solidified film. Ultrasonic vibrations can be generated by immersing a known ultrasonic generator in a storage tank of ethanol solution. After ultrasonic cleaning, the ethanol solution adhering to the surface of the partially plated product 1 is removed by rinsing with water or the like. The concentration of the ethanol solution will be described later, along with Table 4.

[0079] Here, we will explain the plating process in detail with reference to Figure 5. Figure 5(A) shows a photograph of partially plated product 1, which has undergone electroless nickel plating on a copper plate as the base material. Figure 5(B) shows a photograph of partially plated product 2, which has undergone electrolytic nickel plating on a brass plate as the base material. Figure 5(C) shows a photograph of partially plated product 3, which has undergone electrolytic copper plating on a brass plate as the base material. In partially plated product 1, the details of the plating process were written with a glass rod, while in partially plated products 2 and 3, the details were written with a felt-tip pen. In all cases, a clip was attached to the right end of the metal plate, and the plated product was suspended so that a portion of the metal plate protruded from the plating solution. As a result, a portion of the right side of the metal plate does not have a plating layer attached.

[0080] (Electroless nickel plating treatment) The bath composition and other details for electroless nickel plating have been described above in the selection test for oil-based inks, so they are omitted here. Since the surface hardness of the electroless nickel plating layer can be increased by heating, a heating step may be included as a post-treatment for partially plated products that require high strength, such as sliding parts. Note that electroless nickel plating is not limited to nickel-phosphorus plating, but may also be known electroless nickel plating using acidic baths such as nickel-boron plating or nickel-tungsten-phosphorus plating.

[0081] (Electro-nickel plating treatment) Electroplating nickel using an acidic bath can be performed using any known acidic bath, such as a Watt bath. For example, the bath composition of the electroplating nickel solution was 250 g / L nickel sulfate, 45 g / L nickel chloride, and 40 g / L boric acid per liter of nickel plating aqueous solution. The plating conditions were a bath temperature of 40°C to 55°C, a pH of 3.5 to 4.5, and a current density of 2 A / dm². 2 From 10A / dm 2 This is sufficient. The plating bath time is not limited and can be adjusted according to the thickness of the electroplated nickel layer.

[0082] In the case of electroplating, prior to the electroplating bath, an activation treatment may be performed in which the base material is immersed in an acidic solution to activate the areas where a solidified film has not yet formed. The acidic solution used for activation can be, for example, if the base material is made of copper, a concentrated sulfuric acid solution containing 98% sulfuric acid by weight, diluted with water to a volume ratio of 1:9. The activation treatment roughens the exposed areas of the base material, improving the adhesion between the electroplated layer formed on the surface and the base material, thus making it less likely for the plating layer to peel off from the edges.

[0083] (Electroplating of copper) For electroplating nickel using an acidic bath, any known copper sulfate bath will suffice. For example, the bath composition of the electroplating solution was approximately 160 g / L to 220 g / L of copper sulfate, approximately 40 g / L to 80 g / L of undiluted sulfuric acid, and approximately 20 mg / L to 80 mg / L of chloride ions per liter of copper plating aqueous solution. The plating bath conditions were approximately 30°C, pH 1.0 or less, and current density approximately 8 A / dm². 2 The term "concentrated sulfuric acid" here refers to a sulfuric acid solution containing approximately 98% sulfuric acid by weight. The plating bath time is not limited and can be adjusted according to the thickness of the electroplated copper layer.

[0084] (Evaluation test of the cleaning process) In the evaluation test of the cleaning process, the concentration of the ethanol aqueous solution into which the plated base material was immersed was varied, and the degree of delamination of the solidified film after 10 seconds of ultrasonic cleaning and the degree of delamination after further wiping were evaluated. The ethanol aqueous solutions used in the test consisted of six types: ethanol aqueous solutions prepared by mixing anhydrous ethanol and water at concentrations of 50%, 60%, 70%, 80%, and 90% by volume, and a 99.5% by volume anhydrous ethanol solution. The results of the evaluation test are shown in Table 4 below.

[0085] [Table 4] TIFF2026100203000015.tif23164

[0086] When the ethanol concentration was 80% by volume or less, ultrasonic cleaning for only 10 seconds was insufficient to completely remove the solidified film, and additional wiping was required. On the other hand, when the ethanol concentration was 90% by volume or higher, the solidified film was completely removed within 10 seconds of cleaning, and it was confirmed that manual wiping could be omitted. Therefore, for mass-produced items such as machine parts, immersion in an ethanol aqueous solution of 90% by volume or higher is preferable.

[0087] On the other hand, even when the ethanol concentration was between 50% and 80% by volume, the solidified film could be removed simply by lightly wiping it with a cloth by a worker. Therefore, in the case of partially plated products that require a wiping process after the removal of the masking agent, such as decorative items manufactured through multiple partial plating processes, the concentration of the ethanol aqueous solution may be less than 90%.

[0088] (Evaluation test of the plating layer) In the evaluation test of the plating layer, the solidified film was washed off after the plating process, and the deposition state of the plating layer on partially plated products 1, 2, and 3 was evaluated. The subjects of the evaluation test are shown in Figure 5. Specifically, there were three cases: when an electroless nickel plating layer was formed on a copper plate (Figure 5(A)), when an electrolytic nickel plating layer was formed on a brass plate (Figure 5(B)), and when an electrolytic copper plating layer was formed on a brass plate (Figure 5(C)). The results of the evaluation test are shown in Table 5 below. In this evaluation test, the details of the plating process were written using this oil-based ink with a glass rod or felt-tip pen to form a solidified film.

[0089] [Table 5] TIFF2026100203000016.tif29168

[0090] In all plating processes, it was confirmed that a plating layer was formed that allowed for clear identification of the contours of the areas where a solidified film was formed. In other words, it was confirmed that with this oil-based ink, peeling did not occur even in thin solidified films that were not recoated, at the contour areas where peeling would normally begin. From these test results, it was confirmed that partially plated products using this oil-based ink are equivalent in quality to partially plated products using conventional resin-based plating paints in terms of the quality of the plating layer.

[0091] As described above, this oil-based ink eliminates the strong eye irritation and pungent odor of thinners in both the coating and stripping processes while maintaining the quality of partially plated products, thereby improving the working environment for people. Furthermore, the reduction in process time and improved work efficiency also reduce the burden on workers.

[0092] (others) In this embodiment, plating treatments for depositing a copper plating layer and plating treatments for depositing a nickel plating layer were described as examples, but the type of plating treatment is not limited as long as it is an acidic bath that does not dissolve the rosin resin. For example, it may be a zinc plating treatment using a known zinc chloride bath, a gold plating treatment using an acidic bath (potassium gold cyanide), a silver plating treatment using a non-cyanide silver plating bath, etc. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical scope of the present invention is indicated by the claims, not limited to the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of symbols]

[0093] 1, 2, 3... Partially plated products, 10…Plating base material, 11…Oil film layer, 20...coating layer, 30...solidified film, 40...catalyst, 50...plating layer

Claims

1. A method for manufacturing a partially plated product, comprising applying a masking agent to a portion of the surface of a plated base material and forming a plating layer on the remaining portion of the plated base material that is not masked, The process includes steps 1 through 4 in order. The first step is a degreasing step in which the surface of the plating base material is degreased. The second step is a coating step in which the oil-based ink used as a masking agent is applied to the degreased portion to form a coating layer. The third step is a solidification film formation step, in which the solvent contained in the coating layer is evaporated to form a solidified film. The fourth step is a plating process in which the plating layer is formed using an acidic bath. Furthermore, the coating step is a step of applying the oil-based ink, which mainly contains the rosin resin that forms the solidified film and alcohols capable of dissolving the rosin resin as a solvent. The aforementioned solidification film formation step is a step of forming the solidified film with an average film thickness of at least 0.4 μm. A method for manufacturing partially plated products, characterized by the following:

2. The coating step is a step of applying the oil-based ink, which contains the alcohols in a proportion of 50% to 90% by weight relative to the total weight of the oil-based ink. In the aforementioned solidification film formation step, the coating layer is formed by the evaporation of the alcohols within one minute without heating or ultraviolet irradiation. A method for manufacturing a partially plated product according to claim 1.

3. This includes a first control step for controlling the number of times the oil-based ink is applied in layers, In the first control step, the number of times the coating step and the solidification film formation step are performed is counted to be between 1 and 5 times, thereby controlling the average film thickness to be between 0.4 μm and 3.0 μm. The method for manufacturing a partially plated product according to claim 2.

4. Furthermore, the process includes a second control step for identifying the application area of ​​the oil-based ink, The second control step is included in any period from the coating step to the start of the plating process. The aforementioned coating step is a step of applying the oil-based ink, which contains a colorant as a secondary component. In the second control step, the application area of ​​the oil-based ink is identified by the coloring state of the coating layer or the solidified film. A method for manufacturing a partially plated product according to claim 1.

5. Furthermore, the process includes a fifth step of peeling off the solidified film, The fifth step is to immerse the partially plated product on which the plating layer has been formed in a stripping solution consisting of ethanol with a concentration of 90% by volume or more, and to ultrasonically clean it. A method for manufacturing a partially plated product according to any one of claims 1 to 4.

6. A partially plated product comprising a base material, a masking layer, and a plating layer, The masking layer consists of a solidified film formed by curing and drying oil-based ink, and is provided on a selected portion of the surface of the plated base material. The aforementioned plating layer consists of a nickel plating layer or a copper plating layer deposited on the surface of the plating base material by an acidic bath, and is provided in the remaining portion excluding the masking layer. The solidified film contains rosin resin as its main component, and its average film thickness is at least 0.4 μm. A partially plated product characterized by the following features.

7. The aforementioned plating base material is a metal machine part, The solidified film is provided on multiple surfaces of the machine part, The average film thickness is set to 3.0 μm or less. The partially plated product according to feature 6.

8. The solidified film contains a coloring agent as a secondary component. The partially plated product according to claim 6 or 7.

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