Multilayer structure and method for manufacturing same
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2026-04-02
- Publication Date
- 2026-07-08
Abstract
Description
Laminated structure and method for manufacturing the same
[0001] The present invention relates to a laminate structure including a resin substrate and a metal layer, and a method for producing the same.
[0002] Establishing a technology for coating a resin substrate with a metal layer such as a plating layer has made it possible to replace a portion of a product that was previously made solely of metal materials with a resin material, resulting in various advantages, such as reduced product weight and cost, improved freedom of shape, and easier mass production. On the other hand, it is known that the adhesion between a resin substrate and a metal layer (particularly a plating layer) is poor. The most commonly used measure for improving the adhesion between a resin substrate and a plating layer is to roughen the surface of the resin substrate (see, for example, Patent Documents 1 to 4).
[0003] Patent Document 1 discloses treating plastics with an etching solution containing permanganate and an inorganic acid before metal plating the plastics. Patent Document 2 discloses a pretreatment method for electroless plating the surface of a polycarbonate molded article, in which the polycarbonate molded article is immersed in an alkaline aqueous solution and then surface-treated with an aqueous solution of a hydrogen carbonate compound and ozone.
[0004] Patent Document 3 discloses a resin plating method in which syndiotactic polystyrene resin is electrolessly plated and then electroplated, and discloses an ozone water treatment in which the syndiotactic polystyrene resin is brought into contact with an aqueous ozone solution as a pre-plating treatment instead of chromic acid etching, etc. Patent Document 4 discloses a pre-plating method for the surface of an ABS resin in which the ABS resin is treated with a solution containing persulfuric acid obtained by electrolyzing sulfuric acid alone.
[0005] Furthermore, techniques for improving the adhesion between a resin substrate and a plating layer by methods other than roughening the surface of the resin substrate have been investigated (for example, Patent Documents 5 to 8).
[0006] Patent Document 5 discloses a method for forming a functional film on a resin product by the steps of: (1) introducing acidic groups into the resin product; (2) treating the resin product from step (1) with a metal ion-containing liquid; and (3) reducing the resin product from step (2) to form a metal film on the resin product.
[0007] Patent Document 6 discloses that the surface of a polyethylene terephthalate resin is etched, a catalyst is applied, and then an ethyl alcohol solution containing ammonia is used in the process of electroless copper plating. By chemically dissolving and modifying the surface of the polyethylene terephthalate resin, the chemical adhesion between the metal and the surface of the plated object is strengthened, thereby improving the adhesion strength of the copper plating film.
[0008] Patent Document 7 discloses a plated article consisting of a substrate, a primer layer, a plating undercoat layer, and a metal plating film, in which the adhesion between the primer layer and the plating undercoat layer is improved by controlling the type and content of synthetic resin contained in the plating undercoat layer.
[0009] Patent Document 8 discloses a method of forming a primer layer on the surface of an electrically non-conductive substrate by drying and curing a synthetic resin latex, then forming a catalyst metal layer on the primer layer, and then subjecting the catalyst metal layer to electroless plating to form a metal plating layer.
[0010] Japanese Patent Application Laid-Open No. 2008-31513 Japanese Patent Application Laid-Open No. 2002-121678 Japanese Patent Application Laid-Open No. 2012-52214 Japanese Patent No. 6953484 Japanese Patent No. 3475260 Japanese Patent Application Laid-Open No. 7-180062 Japanese Patent No. 5780635 Japanese Patent Application Laid-Open No. 2001-107257
[0011] The surface roughening techniques for resin substrates disclosed in Patent Documents 1 to 4 use chemicals with strong oxidizing power, which raises concerns about environmental impact and waste liquid disposal issues. The surface treatment techniques for resin substrates disclosed in Patent Documents 5 to 8 do not use such chemicals, but the adhesive strength between the resin substrate and the metal layer is unstable, and there is a risk that the adhesiveness between them cannot be improved.
[0012] Therefore, an object of the present invention is to provide a laminated structure that can be produced without using a chemical solution with strong oxidizing power and that has high adhesion between a resin substrate and a metal layer, and a method for producing the same.
[0013] According to one aspect of the present invention, there is provided a laminated structure comprising: a resin substrate having a substrate body and a modified layer covering the surface of the substrate body; and a metal layer covering the surface of the modified layer, wherein the oxygen element concentration on the surface of the modified layer is 17 atomic % or more and 30 atomic % or less, and the modified layer has a needle-like structure on the surface in a cross-sectional view.
[0014] According to another aspect of the present invention, there is provided a method for producing a laminated structure, comprising: a surface treatment step of treating the surface of a resin substrate to form a surface-treated resin substrate having a substrate body and a softened layer covering the substrate body; a heat treatment step of heat-treating the surface-treated resin substrate to harden the softened layer and form a modified layer; and a metal layer formation step of dissolving a portion of the surface of the modified layer by a plating method to form a needle-like structure and forming a metal layer on the surface of the modified layer including the needle-like structure, wherein the oxygen element concentration of the modified layer is 17 atomic % or more and 30 atomic % or less.
[0015] According to the present invention, it is possible to provide a laminated structure that can be produced without using a chemical solution having a strong oxidizing power and that has high adhesion between a resin substrate and a metal layer, and a method for producing the same.
[0016] FIG. 1 is a schematic perspective view of a laminated structure according to a first embodiment. FIG. 2A is a schematic enlarged cross-sectional view of the laminated structure taken along line X-X in FIG. 1. FIG. 2B is a schematic enlarged cross-sectional view of a portion of the laminated structure shown in FIG. 2A. FIG. 3A is a schematic enlarged cross-sectional view illustrating a method for manufacturing a laminated structure according to a first embodiment. FIG. 3B is a schematic enlarged cross-sectional view illustrating a method for manufacturing a laminated structure according to a first embodiment. FIG. 3C is a schematic enlarged cross-sectional view illustrating a method for manufacturing a laminated structure according to a first embodiment. FIG. 3D is a schematic enlarged cross-sectional view illustrating a method for manufacturing a laminated structure according to a first embodiment. FIG. 4A is a TEM image showing needle-like structures formed on the surface of a modified layer of a laminated structure. FIG. 4B is a TEM image showing needle-like structures formed on the surface of a modified layer of a laminated structure. FIG. 4C is a TEM image showing needle-like structures formed on the surface of a modified layer of a laminated structure. FIG. 5 shows elemental mapping of O (oxygen) element by TEM-EDX of the laminated structure.
[0017] The present inventors have conducted extensive research to improve the adhesion between a resin substrate and a metal layer in a laminate structure in which the resin substrate and the metal layer are laminated, and as a result have found for the first time that the adhesion between the resin substrate and the metal layer can be improved by increasing the oxygen element concentration on the surface of the resin substrate in contact with the metal layer and by providing a needle-like structure on that surface.
[0018] Hereinafter, a laminated structure according to the first embodiment and a method for manufacturing the same will be described with reference to the drawings.
[0019] [Embodiment 1] (Laminated Structure 10) FIG. 1 is a schematic perspective view of a laminated structure 10 according to an embodiment, FIG. 2A is a schematic enlarged cross-sectional view of the laminated structure 10 taken along line X-X in FIG. 1 (a cross-section in the thickness direction of the resin substrate 20), and FIG. 2B is a schematic enlarged cross-sectional view of a portion of FIG. 2A. As shown in FIGS. 1 and 2A, the laminated structure 10 includes a resin substrate 20 and a metal layer 40 provided on the surface 20a of the resin substrate 20. The resin substrate 20 includes a substrate body 22 and a modified layer 21N covering the surface 22a of the substrate body 22. The surface 22a of the substrate body 22 is preferably entirely covered by the modified layer 21N, but may not be partially covered. In the example of the laminated structure 10 shown in FIG. 2A, the surface 22a of the substrate body 22 is entirely covered by the modified layer 21N. The modified layer 21N is located on the surface 20a side of the resin substrate 20, and the surface 21Na of the modified layer 21N coincides with the surface 20a of the resin substrate 20. Therefore, the metal layer 40 covers the surface 21Na of the modified layer 21N. It is preferable that the surface 20a of the resin substrate 20 is entirely covered by the metal layer 40, but it does not have to be partially covered.
[0020] The oxygen element concentration of the surface 21Na of the modified layer 21N is 17 atomic % or more and 30 atomic % or less. The oxygen element concentration (atomic %) refers to the oxygen element concentration when the sum of the element concentrations of oxygen (O), carbon (C), nitrogen (N), and copper (Cu) on the surface 21Na of the modified layer is taken as 100 atomic %. The oxygen element concentration within this range indicates the presence of an appropriate amount of oxygen-based functional groups on the surface 21Na of the modified layer 21N. The oxygen-based functional groups form chemical bonds with the metal layer 40 covering the surface 21Na of the modified layer 21N. Therefore, the presence of an appropriate amount of oxygen-based functional groups on the surface 21Na is believed to enhance adhesion between the resin substrate 20 and the metal layer 40. If the oxygen element concentration is less than 17 atomic %, the adhesion between the resin substrate 20 and the metal layer 40 may not be sufficiently improved. If the oxygen element concentration is greater than 30 atomic %, the strength of the modified layer 21N may be reduced for the following reasons.
[0021] Oxygen elements are introduced when the chemical bonds of the polymers in the resin are broken during the surface treatment process (details will be described later). Therefore, the oxygen element concentration in the modified layer 21N of the laminate structure 10 serves as an indicator of the degree of severance of chemical bonds in molecular chains during the surface treatment process. The heat treatment process performed after the surface treatment process can recombine the broken chemical bonds and even generate new chemical bonds. Therefore, if the degree of severance of chemical bonds during the surface treatment is appropriate, the strength of the modified layer 21N can be sufficiently restored and even improved by undergoing heat treatment. However, if the severance of chemical bonds during the surface treatment proceeds excessively, the molecular weight is reduced due to oxygen introduction and bond dissociation, resulting in reduced heat resistance. Therefore, even if heat treatment is performed, the strength of the modified layer 21N cannot be fully restored. An oxygen element concentration of 30 atomic % or less can be inferred to indicate that the severance of chemical bonds during the surface treatment was appropriate, thereby suppressing a decrease in the strength of the modified layer 21N.
[0022] The concentrations of various elements on the surface 21Na of the modified layer 21N are measured by XPS (X-ray photoelectron spectroscopy). The XPS measurement conditions are as follows: an XPS spectrometer (e.g., Quantes manufactured by ULVAC-PHI, Inc.) is used, and qualitative, semi-quantitative, and chemical state analyses are performed on a rectangular area of 1000 μm × 200 μm on the surface 21Na as the measurement region. In analyses using XPS, the analysis depth is typically several nanometers.
[0023] The oxygen element concentration on the surface 21Na of the modified layer 21N is preferably higher than that of the substrate body 22. In other words, it can be seen that the modified layer 21N is formed by treating the surface 20a of the resin substrate 20 to increase the oxygen element concentration. Because the oxygen element concentration on the surface 21Na of the modified layer 21N is higher than that of the substrate body 22, the effect of further increasing the adhesion between the resin substrate 20 and the metal layer 40 can be obtained compared to when the metal layer 40 is directly formed on the surface of the substrate body 22.
[0024] Furthermore, the modified layer 21N has a higher oxygen element concentration throughout its entirety than the resin substrate 20. Therefore, the modified layer 21N can also be referred to as an "oxygen-concentrated layer." As will be described later, needle-shaped structures N are formed on the surface 21Na of the modified layer 21N. Since these needle-shaped structures N also have a higher oxygen element concentration than the resin substrate 20, they are considered to be part of the modified layer (oxygen-concentrated layer) 21N. However, the "surface 21Na of the modified layer 21N" refers to the surface excluding the needle-shaped structures N.
[0025] The extent of the modified layer 21N can be identified using the following method. First, the laminated structure 10 is cut in the thickness direction of the resin substrate 20, and a thin section sample is prepared from the cross section. The thin section sample is analyzed using TEM-EDX, focusing on the boundary between the resin substrate 20 and the metal layer 40, to obtain a TEM image and oxygen (O) elemental mapping. The approximate extent of each layer (substrate body 22, modified layer 21N, and metal layer 40) is confirmed using the TEM image. Next, within the range corresponding to the modified layer 21N on the elemental mapping, a region with a high oxygen elemental concentration is identified in detail to determine the modified layer (or oxygen-enriched layer) 21N (the region enclosed by dashed lines in FIG. 5 ).
[0026] The thickness 21Nt (FIG. 2B) of the modified layer 21N is preferably 10 nm or more and 5000 nm or less. The thickness 21Nt of the modified layer 21N is confirmed using a TEM image at a magnification of 300,000 times. The thickness 21Nt refers to the "maximum dimension of the modified layer 21N" when measured in the thickness direction of the laminated structure 10 within an arbitrary field of view. As shown in FIG. 5, the surface (interface with the metal layer 40) and the back surface (interface with the substrate body 22) of the modified layer 21N may not be flat. Even in this case, the maximum dimension of the modified layer 21N identified in the oxygen (O) element mapping measured within an arbitrary field of view is defined as the thickness 21Nt of the modified layer 21N. The thickness of the modified layer 21N can be measured by one TEM-EDX measurement, but in order to improve the measurement accuracy, the TEM-EDX measurement is performed at different positions (for example, 2 to 6 positions) of the thin sample, and the data of the thickness 21Nt of the modified layer 21N obtained are arithmetically averaged to obtain the average thickness (21Nt ave ) may be the thickness of the modified layer 21N of the resin substrate 20 included in the laminated structure 10.
[0027] In the cross-sectional view of the laminated structure 10 according to the first embodiment, the modified layer 21N has needle-like structures N on its surface 21Na (FIGS. 2A and 2B). These needle-like structures N can exert an anchoring effect, which is expected to improve adhesion between the resin substrate 20 and the metal layer 40. In this specification, the term "needle-like structures N" refers to elongated protrusions that can be confirmed in a TEM image at a magnification of 300,000 times, and have an aspect ratio (Nt / Nw) of 2 or more of the length Nt to the width Nw, and the length Nt is 30 nm or more.
[0028] In this specification, the "needle-like structure N" is not limited to a structure with a pointed tip. The needle-like structure N includes various shapes, such as a tapered structure like the needle-like structure N1 and a rounded tip like the needle-like structure N2, as shown in FIG. 2B. Furthermore, like the needle-like structure N1, the longitudinal direction may be substantially perpendicular to the surface 21Na of the modified layer 21N, or may be inclined relative to the surface 21N.
[0029] Although the surface 21Na of the modified layer 21N is illustrated as a flat plane in FIG. 2B, it may not actually be flat (see FIGS. 4A to 4C). In such cases, the curved surface is identified from the position of the "valley" between adjacent needle-like structures N, and the surface 21Na of the modified layer 21N is defined. Specifically, on the surface 21Na of the modified layer 21N observed in a TEM image at 300,000x magnification, a point is marked at the lowest position of the valley (the point where the slope of the tangent changes from positive to negative, i.e., the inflection point). A point is marked at each valley within the field of view (black dots in FIGS. 4A to 4C), and a straight line (line segment) is drawn between two adjacent points (two-dot chain lines in FIGS. 4A to 4C). Because each line segment is tangent to another line segment at at least one of its endpoints, the line segments form a continuous polygonal line. This polygonal line is referred to as the "surface 21Na of the modified layer 21N." As will be described later, the length of each line segment corresponds to the width Nw of the needle-like structure N separated from the modified layer 21N by that line segment.
[0030] It is assumed that there is "one" valley between adjacent needle-like structures N, and one point is assigned to one valley. If one valley has multiple inflection points, only the lowest inflection point among those inflection points is assigned a point. The work of assigning points to the valleys may be done manually by a person through visual inspection, or may be done automatically by image analysis software.
[0031] The method for measuring the width Nw and length Nt of the needle-like structures N (N1 to N3) will be described. The width Nw of the needle-like structure N is the distance between the points on both sides of the target needle-like structure N. As can be seen from the above description and Figures 4A to 4C, the width Nw of the needle-like structure N corresponds to the length of the line segment separating the target needle-like structure N from the modified layer 21N (referred to as the "line segment at the base of the needle-like structure N"), among the multiple line segments drawn to define the surface 21Na of the modified layer 21N. The length Nt of the needle-like structure N (N1 to N3) is the distance from the intersection of the longitudinal axis (longitudinal axis) of the needle-like structure N and the outline of the needle-like structure N (usually at or near the apex of the needle-like structure N) to the intersection of the longitudinal axis and the line segment at the base of the needle-like structure N. The longitudinal axis is a line drawn extending in the longitudinal direction of the needle-like structure N and passing through approximately the center of the width of the needle-like structure N. The longitudinal axis can be manually pulled by a human being through visual inspection.
[0032] 4A to 4C show TEM images of actual needle-like structures N. In each figure, the TEM image on the left shows the needle-like structure N (enclosed in a dashed ellipse) to be analyzed, and the TEM image on the right shows the outline of the needle-like structure N drawn with a dashed line, with its width Nw and length Nt illustrated.
[0033] As described above, the needle-like structures N have an aspect ratio Nt / Nw of 2 or more, and preferably have a length Nt of 30 nm or more. This improves the anchoring effect of the needle-like structures N, and can further increase the adhesion between the resin substrate 20 and the metal layer 40.
[0034] The resin substrate 20 is not particularly limited, and examples thereof include acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), acrylonitrile styrene acrylate (ASA), silicone composite rubber-acrylonitrile-styrene (SAS), Noryl, polypropylene, polycarbonate (PC), polycarbonate alloy, acrylonitrile styrene, polyacetate, polylactic acid, polystyrene, polyamide, aromatic polyamide, polyethylene, polyether ketone, polyethylene terephthalate, The polymer may include one or more selected from the group consisting of polybutylene terephthalate, polysulfone, polyether ether sulfone, polyetherimide, modified polyphenylene ether, polyphenylene sulfide, polyphenylene oxide, polyamide, polyimide, modified polyimide, epoxy resin, cycloolefin polymer, polynorbornene, perfluoroalkoxy fluoropolymer, polytetrafluoroethylene, and vinylidene fluoride, vinyl resin, phenol resin, polyacetal, nylon, liquid crystal polymer, etc., and copolymers of the above polymers.
[0035] The metal layer 40 of the laminated structure 10 preferably contains one or more selected from the group consisting of Fe, V, Ni, Ti, Ca, Ag, Zn, Al, Mg, Rh, Pt, Au, Pd, Co, Mn, and Cu.
[0036] (Manufacturing Method of Laminated Structure 10) Next, a manufacturing method of the laminated structure 10 will be described. Figures 3A to 3D are schematic enlarged cross-sectional views illustrating the manufacturing method of the laminated structure 10. The manufacturing method of the laminated structure 10 includes: 1) a surface treatment step of treating the surface 200a of the resin substrate 200 to form a surface-treated resin substrate 201 including a substrate main body 22 and a softened layer 210 covering the substrate main body 22; 2) a heat treatment step of heat-treating the surface-treated resin substrate 201 to harden the softened layer 210 and form a modified layer 21; and 3) a metal layer formation step of dissolving part of the surface 21a of the modified layer 21 by plating to form needle-like structures, and forming a metal layer 40 on the surface 21Na of the modified layer 21N including the needle-like structures N.
[0037] Step 1) Surface Treatment Step: A resin substrate 200 is prepared, and its surface 200a is subjected to a surface treatment (softening treatment). This results in a surface-treated resin substrate 201, which includes a substrate body 22 and a softened layer 210 covering the substrate body 22. One example of the surface treatment is ultraviolet irradiation (UV irradiation). By irradiating the surface 200a of the resin substrate 200 with ultraviolet (UV) light, some of the chemical bonds of the molecules in the resin at the surface 200a are broken (FIG. 3A). By breaking the chemical bonds at the surface 200a of the resin substrate 200 in this manner (sometimes referred to as modifying the surface 200a (surface modification)), a softened layer 210 is formed (FIG. 3B). As described in detail below, oxygen-based functional groups are introduced into the portions of the polymer chains (main chains and side chains) where the chemical bonds are broken, thereby increasing the oxygen element concentration in the softened layer 210 (and the modified layer 21N formed from the softened layer 210). Therefore, the oxygen element concentration in the modified layer 21N can be an index for determining the degree of severance of chemical bonds in polymer chains during the surface treatment process.
[0038] Two mechanisms are assumed for the severing of chemical bonds. First, it is thought that the chemical bonds of the molecules in the resin are severed by the energy of the UV irradiated onto the resin substrate 200. This severing mechanism is sometimes referred to as "direct severing." Another mechanism is that the energy of the UV irradiated onto the resin substrate 200 generates ozone from oxygen in the air, and this ozone then severs the chemical bonds of the molecules in the resin. This severing mechanism is sometimes referred to as "indirect severing."
[0039] Furthermore, the severing of chemical bonds includes the severing of chemical bonds in the main chains of the molecules (polymers) of the resin that constitutes the resin substrate 200, and the severing of chemical bonds in the side chains of the polymers.
[0040] When the chemical bonds of the main chain are severed, it is presumed that some of the severance sites recombine to regenerate the original chemical bonds, while functional groups are introduced into the remaining severance sites, maintaining the main chain in a severance state. Examples of functional groups include acid groups, carboxyl groups, and other functional groups having an -O-H structure at their terminals. The mechanism by which functional groups (particularly functional groups having an -O-H structure) are introduced is as follows: in the case of direct severance, radicals generated by the severance of chemical bonds in the resin (mainly the surface 200a of the resin substrate 200) react with oxygen in the air, introducing O into the severance sites of the chemical bonds, which then react with moisture in the air, introducing an -O-H structure. In the case of indirect severance, when ozone severs the chemical bonds of molecules in the resin, O is introduced into the severance sites of the chemical bonds, which then reacts with moisture in the air, introducing an -O-H structure.
[0041] When the chemical bond of the side chain is broken, a functional group can be introduced at the broken site by the same mechanism as in the case of the main chain.
[0042] At the surface 200a of the resin substrate 200, the strength of the surface 200a is reduced (the surface 200a is softened) due to the severing of chemical bonds of molecules in the resin (particularly the severing of chemical bonds of the main chain).
[0043] The irradiation time and irradiation intensity of UV irradiation are selected so that a softened layer 210 with an appropriate softness is formed from the surface 200a to an appropriate depth, and a sufficient amount of oxygen-based functional groups are introduced into the softened layer 210. For example, the irradiation time is 10 seconds to 30 minutes, and the irradiation intensity is 5 to 250 mW / cm. ２ If the UV irradiation time is too short, the amount of functional groups introduced into the softened layer 210 will be insufficient, making it impossible to sufficiently improve the oxygen element concentration in the modified layer 21N. Furthermore, even if the subsequent heat treatment process is performed, the surface hardening effect may be insufficient. On the other hand, if the UV irradiation time is too long, the surface 200a of the resin substrate 200 will be excessively damaged (i.e., the chemical bonds in the polymer will be severed), and the surface strength may remain reduced and not recover even after the heating process.
[0044] In addition to UV irradiation, other surface modification methods include plasma treatment, corona treatment, and electron beam irradiation, and surface modification can be performed by one or more of these. Any of these methods can modify the surface 210a of the resin substrate 200 by cleaving some of the chemical bonds of the molecules of the resin material present on the surface 200a. This forms a softened layer 210 on the surface 200a of the resin substrate 200, resulting in a surface-treated resin substrate 201 that includes the softened layer 210 and the unsoftened substrate body 22 ( FIG. 3B ).
[0045] Step 2) Heat Treatment Step The surface-treated resin substrate 201 is heated to harden the softened layer 210 and form the modified layer 21 ( FIG. 3C ). This forms a resin substrate 202 including the modified layer 21. Note that at this stage, the modified layer 21 does not include the needle-like structures N on the surface 21a. In Patent Documents 5 to 8, no heat treatment is performed to harden the softened layer. Therefore, in step 3) described below, the softened layer 210 may be removed, making it difficult to achieve stable bonding between the resin substrate 20 and the metal layer 40.
[0046] The reason why the modified layer 21 that is harder than the original resin substrate 200 can be formed by heat-treating the softened layer 210 is not clear, but the following mechanism is assumed.
[0047] As described above, the surface treatment step in step 1) cuts chemical bonds, and functional groups containing an —O—H structure can be introduced at the cut sites. Subsequent heat treatment causes dehydration condensation between two adjacent functional groups, forming new bonds between the functional groups. Here, the new bonds formed between the functional groups introduced at the cut sites of the main chain can be considered to be the result of the main chain bonds that existed before the cuts being cut, and then rebonding with the functional group inserted between the cut sites (i.e., rebonding of the main chain).
[0048] On the other hand, the new bond formed between the functional groups introduced at the cleavage site of the side chain is a "bond between side chains" that did not exist before the cleavage. A more concrete example is as follows: In a certain molecule in the resin, a side chain terminates in a functional group, but the chemical bond to that functional group is severed, and instead a new bond is formed between the cleavage site of the side chain of another molecule. In other words, the side chain that terminated in a functional group now bonds with the side chain of an adjacent molecule. Therefore, after the heat treatment process, the number of chemical bonds between molecules increases compared to before the surface treatment process, and the strength of the resin increases.
[0049] Due to this mechanism, it is believed that the number of intermolecular chemical bonds increases on the surface of the resin material compared to before the surface treatment process, and as a result, a modified layer 21 that is harder than the substrate body 22 (formed from unmodified resin material) can be formed.
[0050] The heat treatment temperature must be lower than the melting point of the resin material constituting the surface-treated resin substrate 201, and can be, for example, 60° C. to 300° C. The heating time can be set appropriately according to the heating temperature, and is, for example, 1 minute to 120 minutes.
[0051] It is important to perform the heat treatment step before the step 3) metal layer formation step described below. The softened layer 210 before the heat treatment has low resistance to the plating solution. Therefore, if the step 3) metal layer formation step is performed before the heat treatment step and the softened layer 210 is brought into contact with a chemical solution (e.g., a plating solution in an electroless plating bath), most of the softened layer 210 may dissolve into the plating solution. Because the needle-like structure N is formed by partial dissolution of the modified layer 21, it is difficult to form the needle-like structure N if the step 3) metal layer formation step is performed with the softened layer 210, from which most of it has dissolved. By performing the step 2) before the metal layer formation process (plating process) in the step 3) metal layer formation step to improve the surface strength of the resin substrate in advance, it is possible to prevent most of the softened layer 210 from dissolving into the plating solution in the step 3) metal layer formation step. That is, after step 3) metal layer formation step, the modified layer 21 (oxygen-enriched layer) remains partially (needle-shaped) on the surface of the resin substrate 20, and the oxygen-based functional groups have the effect of improving the adhesion between the resin substrate 20 and the metal layer 40. Furthermore, the modified layer 21 is partially eluted into the plating solution, so that a modified layer 21N having a needle-shaped structure N can be formed.
[0052] Step 3) Metal Layer Formation Step A metal layer 40 is formed by plating to cover the surface 21a of the modified layer 21 (FIG. 3D). The metal layer 40 can be formed by electroless plating. When the resin substrate 202 (FIG. 3C) including the modified layer 21 is immersed in a plating bath for electroless plating, the surface 21a of the modified layer 21 is partially dissolved, forming needle-like structures N (FIG. 3D). Then, a metal layer 40 is formed on the surface 21Na of the modified layer 21N including the needle-like structures N (FIG. 2A).
[0053] Known plating solutions, plating conditions, etc., can be used for electroless plating. Prior to electroless plating, the surface 20a of the resin substrate 20 (the surface 21a of the modified layer 21) is preferably pretreated by a known pretreatment method such as the addition of a catalyst. The metal layer 40 may further include an electrolytic plated layer covering the electroless plated layer.
[0054] In this manner, the laminated structure 10 shown in FIG. 2A can be manufactured.
[0055] Various tests were carried out using samples prepared under the following conditions.
[0056] (Sample Preparation) A COP (cycloolefin polymer) sheet and an LCP (liquid crystal polymer) sheet measuring 50 mm long x 50 mm wide x 0.1 mm thick were prepared as resin substrate samples 200. A laminate structure 10 was prepared from the resin substrate sample according to the procedure shown in Figures 3A to 3C. Measurement samples were prepared according to the processing conditions for each sample in Table 1. Detailed conditions for each processing are shown in Tables 2 to 5.
[0057] (Samples No. 1 to 5) In Samples No. 1 to 5, a COP sheet was used as the resin substrate 200. When a COP sheet was used, basically, treatment A (UV irradiation), treatment B1 (heat treatment in the atmosphere), treatment C (electroless plating), and treatment D (electrolytic plating) were performed. However, in Sample No. 1, treatment B1 was omitted, as will be described later.
[0058] Samples Nos. 3 and 4 are examples, and each sample (laminate structure) was produced using a manufacturing process that satisfied the conditions of this embodiment. As shown in Table 1, treatment A (UV irradiation) was performed for 15 or 20 minutes, followed by treatment B1 (heat treatment in air), treatment C (electroless plating), and treatment D (electrolytic plating). Treatment C (electroless plating) involved treatments C1 to C5 in Table 4 performed in this order, and treatment D (electrolytic plating) involved treatments D1 and D2 in Table 5 performed in this order. The metal layer 40 was formed into a two-layer structure by electroless plating (treatment C) and electrolytic plating (treatment D). The metal element contained in the metal layer 40 was primarily Cu.
[0059] Sample No. 1 is a comparative example, and a sample (laminated structure) was produced under the same conditions as Samples Nos. 3 and 4, except that Treatment B1 (heat treatment in air) was not performed. Sample No. 2 was produced under the same conditions as Samples Nos. 3 and 4, except that Treatment A (UV irradiation) was performed for 5 minutes. Sample No. 5 was produced under the same conditions as Samples Nos. 3 and 4, except that Treatment A (UV irradiation) was performed for 30 minutes.
[0060] (Samples Nos. 6 to 9) Samples Nos. 6 to 9 used an LCP sheet as the resin substrate 200. When an LCP sheet was used, basically, treatment A (UV irradiation), treatment B2 (vacuum heating treatment), treatment C (electroless plating), and treatment D (electrolytic plating) were performed. However, in sample No. 6, treatment B2 was omitted, as will be described later.
[0061] Samples No. 7 and 8 are examples, and samples (laminate structures) were produced using a manufacturing process that satisfied the conditions of this embodiment. As shown in Table 1, treatment A (UV irradiation) was performed for 15 or 20 minutes, and treatment B2 (vacuum heating treatment), treatment C (electroless plating), and treatment D (electrolytic plating) were also performed.
[0062] Sample No. 6 is a comparative example, and a sample (laminate structure) was produced under the same conditions as Samples Nos. 7 and 8, except that Treatment B2 (vacuum heating treatment) was not performed. Sample No. 9 is a comparative example, and a sample (laminate structure) was produced under the same conditions as Samples Nos. 7 and 8, except that Treatment A (UV irradiation) was performed for 30 minutes.
[0063] (1. XPS Measurement) XPS measurement was performed on each sample under the following conditions. First, the metal layer 40 was removed from the sample having the metal layer 40 by wet etching to expose the surface 20a of the resin substrate 20 (corresponding to the surface 21Na of the modified layer 21N). Using an XPS spectrometer (Quantes manufactured by ULVAC-PHI, Inc.), XPS measurement of the exposed surface was performed at an arbitrary position on the surface 21Na, with a rectangular area of 1000 μm × 200 μm as the measurement region, under the following conditions: Photoelectron take-off angle: 45° X-ray beam diameter: 100 μmφ Photoelectron pass energy: 224 eV
[0064] (2. Cross-sectional TEM-EDX) Each sample was cut in the thickness direction, and thin section samples were prepared from the cross sections and subjected to TEM-EDX analysis under the following conditions: FE-TEM / EDX (JEOL JEM-F200 / Noran system 7) Thin sections were prepared using the FIB lift-out method and observed Acceleration voltage: 200 kV Magnification: 300,000 times Field of view: 400 nm x 400 nm
[0065] When one or more needle-like structures N (protrusions with an aspect ratio (Nt / Nw) of 2 or more and a length Nt of 30 nm or more) were observed, the sample was judged to have a "needle-like structure present," whereas when no needle-like structures N were present, the sample was judged to have no needle-like structure. Figures 4A and 4C show TEM images of Sample No. 3 observed at different positions. Figure 4B shows a TEM image of Sample No. 7. Figure 5 shows elemental mapping of oxygen (O) element obtained by EDX analysis of Sample No. 3.
[0066] (3. Adhesion: 90° Peel Evaluation) To measure the adhesion between the resin substrate 20 and the metal layer 40, the peel strength of the metal layer 40 was measured for each sample. The measurement was performed in accordance with JIS C 6471:1995 and JIS C 6481:1996.
[0067] The measurement conditions and measurement procedures were as follows. Measurement equipment: RTF-1210 manufactured by A&D Co., Ltd. Measurement method: Peel copper foil width: 10 mm, 90° peel, peel speed: 50 mm / min Measurement procedure (1) Each sample was prepared using the procedure described above. However, for the electrolytic plating (step D), the plating time was adjusted appropriately to obtain thick electrolytic copper plating. The target film thickness of the electrolytic copper plating was 30 μm. (2) Two parallel slits were made in the metal layer 40 with a cutter. The distance between the two slits was set to 10 mm, and the copper foil on both sides was removed, leaving the copper foil between the slits (10 mm wide). A peel test was performed by gripping one end of the copper foil with a jig and pulling it in a 90° direction relative to the surface of the resin substrate.
[0068] The measurement results are shown in Table 1.
[0069]
[0070]
[0071]
[0072]
[0073]
[0074] Samples Nos. 3, 4, 7, and 8 are examples produced by the manufacturing method according to embodiment 1. In each sample, the oxygen element concentration on the surface 21 a of the modified layer 21 was 17 atomic % or more and 30 atomic % or less, and needle-like structures N were also formed. As a result, the adhesion between the resin substrate 20 and the metal layer 40 was high.
[0075] In Samples No. 1 and 6, a heat treatment process after UV irradiation was not performed during the production of each sample, so although a softened layer 210 was formed on the surface 20a of the resin substrate 20, a hard modified layer 21 was not formed. Therefore, the softened layer 210 was completely removed in the metal layer formation process. In Sample No. 1, since the softened layer 210 was completely removed, the oxygen element concentration on the surface 20a of the resin substrate 20 was low, and the needle-like structure N was not formed. On the other hand, in Sample No. 6, an LCP sheet containing oxygen elements was used as the resin substrate 200, so the oxygen element concentration on the surface 20a of the resin substrate 20 apparently met the requirements of embodiment 1. However, since the softened layer 210 was not present, the needle-like structure N was not formed. As a result, in Samples No. 1 and 6, the adhesion between the resin substrate 20 and the metal layer 40 was low.
[0076] In sample No. 2, the UV irradiation time during sample preparation was too short, resulting in an insufficient amount of oxygen-based functional groups introduced into the softened layer 210, and the oxygen element concentration on the surface 21Na of the modified layer 21N could not be sufficiently improved. As a result, although the modified layer 21 was present on the surface 20a of the resin substrate 20 and the needle-shaped structure N was formed, the adhesion between the resin substrate 20 and the metal layer 40 was low.
[0077] In Samples No. 5 and 9, the UV irradiation time during the preparation of each sample was too long, resulting in an excessive amount of oxygen-based functional groups being introduced into the softened layer 210 (i.e., the oxygen element concentration on the surface 21Na of the modified layer 21N was excessively high), and the softened layer 210 was excessively damaged. Therefore, even after a subsequent heat treatment process, the hardness could not be sufficiently improved. As a result, although the modified layer 21 was present on the surface 20a of the resin substrate 20 and the needle-shaped structure N was formed, the hardness of the modified layer 21 was insufficient, and the adhesion between the resin substrate 20 and the metal layer 40 was low.
[0078] The disclosure of this specification may include the following aspects: <1> A laminated structure comprising: a resin substrate including a substrate body and a modified layer covering the surface of the substrate body; and a metal layer covering the surface of the modified layer, wherein the oxygen element concentration on the surface of the modified layer is 17 atomic % or more and 30 atomic % or less, and the modified layer has a needle-like structure on the surface in a cross-sectional view.
[0079] <2> The laminate structure according to <1>, wherein the oxygen element concentration on the surface of the modified layer is higher than the oxygen element concentration in the substrate body.
[0080] <3> The laminate structure according to <1> or <2>, wherein the modified layer has a thickness of 10 nm or more and 5000 nm or less.
[0081] <4> The resin substrate is selected from the group consisting of acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), acrylonitrile styrene acrylate (ASA), silicone composite rubber-acrylonitrile-styrene (SAS), Noryl, polypropylene, polycarbonate (PC), polycarbonate alloy, acrylonitrile styrene, polyacetate, polylactic acid, polystyrene, polyamide, aromatic polyamide, polyethylene, polyether ketone, polyethylene terephthalate, polybutylene terephthalate, poly The laminate structure according to any one of <1> to <3>, comprising one or more selected from the group consisting of sulfone, polyether ether sulfone, polyetherimide, modified polyphenylene ether, polyphenylene sulfide, polyphenylene oxide, polyamide, polyimide, modified polyimide, epoxy resin, cycloolefin polymer, polynorbornene, perfluoroalkoxy fluoropolymer, polytetrafluoroethylene, and vinylidene fluoride, vinyl resin, phenol resin, polyacetal, nylon, liquid crystal polymer, and copolymers of these polymers.
[0082] <5> A method for producing a laminated structure, comprising: a surface treatment step of treating the surface of a resin substrate to form a surface-treated resin substrate having a substrate main body and a softened layer covering the substrate main body; a heat treatment step of heat-treating the surface-treated resin substrate to harden the softened layer and form a modified layer; and a metal layer formation step of dissolving a part of the surface of the modified layer by a plating method to form needle-like structures and forming a metal layer on the surface of the modified layer including the needle-like structures, wherein the oxygen element concentration of the modified layer is 17 atomic % or more and 30 atomic % or less.
[0083] <6> The method for producing a laminate structure according to <5>, wherein in the surface treatment step, the surface of the resin substrate is subjected to one or more treatments selected from the group consisting of UV irradiation, plasma treatment, corona treatment, and electron beam irradiation.
[0084] This application claims priority based on Japanese Patent Application No. 2023-189651, filed on November 6, 2023, the entire contents of which are incorporated herein by reference.
[0085] 10 Laminated structure 20 Resin substrate 21N Modified layer 22 Substrate body 40 Metal layer
Claims
1. A resin substrate comprising a base material body and a modified layer covering the surface of the base material body, A metal layer covering the surface of the modified layer, Includes, The oxygen element concentration on the surface of the modified layer is 17 atomic percent or more and 30 atomic percent or less. In cross-sectional view, the modified layer is a laminated structure having a needle-like structure on its surface.
2. The laminated structure according to claim 1, wherein the oxygen element concentration on the surface of the modified layer is higher than the oxygen element concentration of the substrate body.
3. The laminated structure according to claim 1, wherein the thickness of the modified layer is 10 nm or more and 5000 nm or less.
4. The aforementioned resin substrates include acrylonitrile butadiene styrene (ABS), polycarbonate / acrylonitrile butadiene styrene (PC / ABS), acrylonitrile styrene acrylate (ASA), silicone-based composite rubber-acrylonitrile-styrene (SAS), Noryl, polypropylene, polycarbonate (PC), polycarbonate alloy, acrylonitrile styrene, polyacetate, polylactic acid, polystyrene, polyamide, aromatic polyamide, polyethylene, polyether ketone, polyethylene terephthalate, and polybutylene terephthalate. The laminated structure according to claim 1, comprising one or more selected from the group consisting of polysulfone, polyetherethersulfone, polyetherimide, modified polyphenylene ether, polyphenylene sulfide, polyphenylene oxide, polyamide, polyimide, modified polyimide, epoxy resin, cyclo-oflefin polymer, polynorbornene, perfluoroalkoxy fluoropolymer, polytetrafluoroethylene, and vinylidene fluoride, vinyl resin, phenolic resin, polyacetal, nylon, liquid crystal polymer, and copolymers of these polymers.
5. A method for manufacturing a laminated structure, A surface treatment step involves treating the surface of a resin substrate to form a surface-treated resin substrate comprising a substrate body and a softened layer covering the substrate body, A heat treatment step is performed by heat-treating the surface-treated resin substrate to harden the softened layer and form a modified layer. The process includes a metal layer formation step in which a portion of the surface of the modified layer is dissolved by a plating method to form a needle-like structure, and a metal layer is formed on the surface of the modified layer including the needle-like structure, A method for manufacturing a laminated structure, wherein the oxygen element concentration of the modified layer is 17 atomic percent or more and 30 atomic percent or less.
6. The method for manufacturing a laminated structure according to claim 5, wherein in the surface treatment step, one or more treatments selected from the group consisting of UV irradiation, plasma treatment, corona treatment, and electron beam irradiation are performed on the surface of the resin substrate.