WO2025182889A1 - Resin composition for plating, plated article, and plating method - Google Patents

Abstract

Provided is a resin composition for plating comprising a surface layer region that includes a surface to be plated and a base layer region that is a region other than the surface layer region. The surface layer region has a weight-average molecular weight larger than that of the base layer region.

Description

Resin composition for plating, plated product, and plating method

This disclosure relates to a resin composition for plating, a plated product, and a plating method.

The technology of forming metal plating on insulating resin materials is used in a wide range of fields, including the formation of automotive and electronic parts, due to its lighter weight, lower costs, freedom in part shape design, and production efficiency.

Japanese Patent Application Laid-Open No. 2008-31513 Japanese Patent Application Laid-Open No. 2002-121678 JP 2012-52214 A Patent No. 6953484 Patent No. 3475260 Japanese Patent Application Publication No. 7-180062 Patent No. 5780635 Japanese Patent Application Laid-Open No. 2001-107257

Since resin materials cannot form a metallic bond at the interface with the plating, their adhesion can be inferior compared to plating on metal. Various methods have been devised to adhere metal plating films to resin materials. Examples include a method of roughening the surface of the resin material to be plated by etching to create an anchoring effect (Patent Documents 1 to 4), a method of introducing functional groups into the surface of the resin material to form chemical bonds with the catalytic metal ions and/or plating metal (Patent Documents 5 and 6), and a method of forming an adhesive layer on the surface of the resin material and then forming a metal plating through this adhesive layer (Patent Documents 7 and 8).

However, when a metal plating film is formed on a resin material, the strength of the material may be inferior compared to when a metal plating film is formed on a metal material, and there is a risk that the metal plating film formed on the surface of the material to be plated will peel off along with the surface region including the surface to be plated. For example, in conventional methods that involve etching a resin material, the surface region including the surface to be plated is roughened, reducing the strength of that surface region and potentially causing the surface portion of the resin composition to peel off.

This disclosure has been made in light of the above-mentioned problems. Specifically, the primary objective of this disclosure is to provide a resin composition for plating that can form a metal plating film with excellent adhesion, a plated product that has a suitable metal plating film with excellent adhesion on a resin composition, and a plating method that can form a suitable metal plating film with excellent adhesion on a resin composition.

The inventors of the present application have come up with the invention of a resin composition for plating, a plated product, and a plating method that achieve the above-mentioned primary objectives.

The resin composition for plating according to one embodiment of the present disclosure comprises a surface region including a surface to be plated, and a base region other than the surface region,
The surface region has a weight average molecular weight greater than that of the base region.

Further, a plating method according to an embodiment of the present disclosure includes a surface treatment step of forming a surface region including a surface to be plated in a resin material;
a plating step of plating the surface to be plated,
the surface treatment step includes irradiating the surface to be plated with energy rays in an oxygen-containing atmosphere,
The surface layer region has a weight average molecular weight greater than that of the base layer region, which is the region other than the surface layer region.

The plating resin composition and plating method according to one embodiment of the present disclosure provide plated articles with suitable metal plating films that have excellent adhesion.

FIG. 1 is a graph showing differential molecular weight distribution curves measured for each of the surface layer region and the base layer region of the resin composition for plating according to the first embodiment of the present disclosure.

The following describes specific embodiments of the present disclosure. Please note that the applicant provides the following explanations and examples to enable those skilled in the art to fully understand the present disclosure, and that they are not intended to limit the subject matter described in the claims. In other words, the present disclosure is not particularly limited to the preferred embodiments described below, and can be modified as appropriate within the scope of its intended purpose. Note that for convenience, the present disclosure may be divided into embodiments and examples, taking into account ease of explanation or understanding of the main points, but partial substitution and/or combination of configurations shown in different embodiments is possible. In describing such embodiments, redundant explanations of substantially identical matters may be omitted, and only differences may be described. In particular, similar effects resulting from similar configurations may not be mentioned in each embodiment.

Furthermore, in this specification, "above" an element refers not only to the case where it is in contact with the top surface of the element, but also to the case where it is not in contact with the top surface of the element. In other words, "above" an element does not only refer to a position above the element that is separated from it, i.e., an upper position above the element via another object, or an upper position with a gap, but also to a position directly above the element that is in contact with it. Furthermore, "above" does not necessarily mean above in the vertical direction. "Above" merely indicates the relative position of an element.

Unless otherwise specified, the various numerical ranges referred to in this specification are intended to include the lower and upper limit numerical values themselves. Furthermore, the term "about" means that there may be a variation or difference of a few percent, for example, ±10%.

As used in this specification, "vertical" and "substantially vertical" do not necessarily mean completely "vertical," but include slight deviations therefrom (for example, within a range of ±10° from completely vertical, e.g., ±5°).

[Resin composition for plating use according to the present disclosure]
The resin composition for plating has a surface to be plated on which a metal plating film is formed. The resin composition for plating has a surface region including the surface to be plated and a base region other than the surface region. In other words, the resin composition for plating of the present disclosure has two regions: a surface region and a base region other than the surface region. The surface region is a region including the surface to be plated and has a constant thickness extending from the surface to be plated toward the interior of the resin composition for plating. The base region is a region other than the surface region including the surface to be plated, and the surface region and base region can be considered to be regions stacked together. For example, when the surface to be plated is viewed as the upper surface, the base region corresponds to the region below the surface region. In other words, the surface region corresponds to the region above the base region in the resin composition. The surface region and base region may be in contact with each other in the vertical direction of the resin composition when the surface to be plated is viewed as the upper surface. Hereinafter, the vertical direction of the resin composition for plating when the surface to be plated is viewed as the upper surface will be referred to as the "thickness direction of the resin composition for plating."

The surface region may be a region 10 μm thick extending from the surface to be plated toward the interior of the resin composition for plating. That is, in the resin composition for plating, the surface region can be the region extending from the surface to a depth of 10 μm along the thickness direction from the surface to be plated. In other words, if the surface to be plated is considered to be the upper surface, the lower region extending more than 10 μm along the thickness direction from the surface to be plated can correspond to the base region. For example, the surface region can also be referred to as the "surface zone," "outer region," or "layer containing the surface to be plated." On the other hand, the base region can also be referred to as the "bulk region," "main region," or "lower region." Alternatively, the "surface region" and "base region" can simply be referred to as the "first region" and "second region," respectively.

The plating resin composition of the present disclosure has different molecular weight distributions in the surface layer region and the base layer region. Figure 1 shows the differential molecular weight distribution curves of the surface layer region and base layer region of a plating composition according to one embodiment of the present disclosure, measured using gel permeation chromatography (GPC). As shown, the differential molecular weight distribution curve of the surface layer region has a gentler slope on the high molecular weight side compared to the differential molecular weight distribution curve of the base layer region. This means that the surface layer region contains more high molecular weight components than the base layer region. In short, the plating resin composition of the present disclosure is more polymerized in the surface layer region compared to the base layer region. Therefore, the surface layer region can also be referred to as the "polymer region" and the base layer region as the "low molecular weight region."

In this configuration, the weight average molecular weight of the surface layer region is greater than the weight average molecular weight of the base layer region. In other words, the weight average molecular weight of the base layer region is smaller than the weight average molecular weight of the surface layer region. In this way, although the surface layer region and the base layer region are regions that exist within the resin composition, which is a continuous, integrated product, their weight average molecular weights are different from each other.

The weight-average molecular weight of the polymer contained in each region of the plating resin composition may be measured using, for example, gel permeation chromatography (GPC) (e.g., Tosoh's high-temperature GPC device, HLC8120GPC) and calculated using a polystyrene standard sample as a reference. Measurement by GPC may be performed under conditions that take into account the solubility and separation characteristics of the materials used in the plating resin composition. For example, conditions such as column temperature and flow rate may be set appropriately depending on the type of material used in the plating resin composition. Furthermore, an appropriate combination of solvent and column may be selected depending on the solubility and separation characteristics of the materials used in the plating resin composition. Specifically, a column may be selected that is compatible with the solvent used in the plating resin composition and does not interact with the plating resin composition dissolved in the solvent. Such solvents and columns may be commercially available. While not particularly limited, the solvent and column combinations described in Agilent Technologies' Technical Publication 5991-6802JAJP, for example, may be used.

This structure allows the resin composition of the present disclosure to have different molecular structures in the surface layer region and the base layer region. Because the surface layer region is polymerized, the metal plating film formed on the surface to be plated can adhere more favorably to the surface to be plated. The reason for this effect is not entirely clear, and although not limited to a particular theory, it is thought that the polymerized surface region allows the metal plating film to interact with the many functional groups that may be present on the surface to be plated.

The peeling mode of a metal plating film from a resin composition does not simply involve the metal plating film peeling off from the surface to be plated, but also includes the metal plating film formed on the surface to be plated peeling off together with the surface region including the surface to be plated. For example, in methods that involve etching a resin composition, the surface region including the surface to be plated is roughened, reducing the strength of the surface region, and even if a metal plating film is formed on the surface to be plated, there is a risk that the surface region of the resin composition will peel off together.

The resin composition for plating disclosed herein has a larger weight-average molecular weight in the surface region, while having a smaller weight-average molecular weight in the base region, thereby improving the strength of the surface region. This makes it possible to effectively prevent the metal plating film formed on the surface to be plated from peeling off together with the surface region, including the surface to be plated. In other words, by polymerizing the surface region, the resin composition for plating disclosed herein prevents the metal plating film from peeling off, which would otherwise be accompanied by destruction of the surface region, and makes it possible to form a metal plating film that adheres more effectively to the resin composition.

Furthermore, according to the present disclosure, while the strength of the surface layer region is improved through polymerization, the weight average molecular weight of the base layer region is relatively low compared to that of the surface layer region. Here, an increase in weight average molecular weight can result in an increase in the hardness of the resin composition. Therefore, according to the present disclosure, by having the surface layer region of the resin composition have a high weight average molecular weight while the base layer region has a relatively low weight average molecular weight, it is possible to favorably adhere a metal plating film to the plated surface without increasing the hardness of the resin composition as a whole. This can be a particularly useful effect when the resin composition for plating is a flexible resin.

When the resin composition for plating disclosed herein is a flexible resin composition, the base layer region has a lower weight-average molecular weight than the surface layer region, allowing for the formation of a suitably adherent metal plating film in the surface layer region without impairing the flexibility of the resin composition. Generally, when plating on a material using a flexible resin that can be deformed by bending or other means, the metal plating film is prone to peeling due to deformation of the material, so high adhesion of the metal plating film is required. In some cases, deformation of the material may destroy the surface layer region, including the surface to be plated, causing the metal plating film to peel off along with the surface to be plated. However, improving the strength of the material to prevent peeling on the surface to be plated and destruction of the surface layer region can reduce the flexibility of the material. In other words, there is a trade-off between suppressing peeling to improve adhesion and maintaining flexibility.

The resin composition for plating of the present disclosure has a surface region with high strength, which can prevent damage to the plated surface having a metal plating film in the surface region. Furthermore, by having a base layer region with a low weight-average molecular weight, the resin composition for plating as a whole can exhibit suitable flexibility. This makes it possible to achieve a favorable balance between the adhesion of the metal plating film and the flexibility of the resin composition. As a result, the resin composition for plating of the present disclosure can also be used favorably in parts such as flexible substrates that are required to have flexibility that allows deformation, such as bending.

Examples of materials for the resin composition for plating include at least one selected from the group consisting of polyester polymers, silicone polymers, acrylic polymers, polyolefin polymers, and copolymers thereof.

More specifically, materials for plating resin compositions include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polystyrene (PS), polyethersulfone (PES), polycarbonate (PC), triacetyl cellulose (TAC), polybutylene terephthalate (PBT), polysilane, polysiloxane, polysilazane, polycarbosilane, polyacrylate, polymethacrylate, polymethyl acrylate, polyethyl acrylate, polyethyl methacrylate, cycloolefin copolymer (COC), cycloolefin polymer (COP), polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polyacetal (POM), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), perfluoroalkyl polymer (PFA), and styrene acrylonitrile copolymer (SAN). These materials may be used alone or in combination of two or more.

The shape of the resin composition for plating is not particularly limited and can be in a variety of shapes. For example, the resin composition for plating can be in the form of a film or sheet. As described above, the resin composition for plating disclosed herein has a surface layer region and a base layer region with different weight-average molecular weights, thereby making it possible to favorably achieve both the adhesion of the metal plating film and the flexibility of the resin composition. Therefore, even when the resin composition for plating is formed from a flexible resin material in the form of a film or sheet, such as a flexible substrate, it is possible to provide a plated product that favorably achieves both adhesion and flexibility.

The weight-average molecular weight of the surface layer region can be, for example, 1.01 times or more, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more, the weight-average molecular weight of the base layer region. When the weight-average molecular weight of the surface layer region relative to the weight-average molecular weight of the base layer region is within the above-mentioned range, a plating resin composition can be provided that is capable of forming a metal plating film with excellent adhesion. Furthermore, when the plating resin composition is formed from a flexible resin material, it is possible to achieve a favorable balance between the adhesion of the metal plating film formed on the plated surface and the flexibility of the resin composition on which the metal plating film is formed.

There is no particular upper limit to the weight average molecular weight of the surface layer region relative to the weight average molecular weight of the base layer region. However, the difference in weight average molecular weight between the surface layer region and the base layer region can affect the overall strength of the resin composition. If the strength of the resin composition is important, the weight average molecular weight of the surface layer region can be, for example, no more than three times, and preferably no more than two times, the weight average molecular weight of the base layer region.

In the resin composition for plating, the weight-average molecular weight may gradually decrease from the surface to be plated to the base region. For example, the weight-average molecular weight may gradually decrease moving from the surface region to the base region. In one embodiment, within the surface region, the weight-average molecular weight may gradually decrease from the surface to be plated to the base region. In other words, the weight-average molecular weight in the surface region may gradually increase from the interior of the resin composition for plating to the surface to be plated. This structure suppresses sudden fluctuations in the weight-average molecular weight within the resin composition for plating, thereby reducing the degree of variation in hardness between the surface region and the base region. This reduces stress concentration caused by excessive fluctuations in hardness between the surface region and the base region, and can suppress the occurrence of damage such as cracks and breaks in the resin composition caused by such stress concentration.

The change in weight-average molecular weight from the surface region to the base region can be confirmed by measuring the weight-average molecular weight of multiple samples taken at regular intervals along the thickness direction of the plating resin composition from the surface region to the base region of the plating resin composition. For example, sampling may be performed at 5 μm intervals along the thickness direction of the plating resin composition from the outermost surface in the surface region of the plating resin composition toward the base region, and the obtained samples may be measured using GPC. The sampling method is not particularly limited, but can be performed, for example, by reactive ion etching (RIE).

In one embodiment, oxygen-containing groups are present at least in the surface region of the plating resin composition. The plating resin composition contains oxygen-containing groups in the surface region, which includes the surface to be plated. Oxygen-containing groups may also be contained in the base region. The oxygen-containing group may be, for example, at least one group selected from the group consisting of an oxo group, a hydroxyl group, an alkoxy group, a carboxyl group, and an alkoxycarbonyl group. Alternatively, the surface region may contain bridging oxygen atoms contained in the polymer structure.

The oxygen-containing groups and/or bridging oxygen atoms contained in the resin composition for plating may be present in greater amounts in the surface region than in the base region. For example, in the resin composition for plating, the C:O element concentration ratio in the surface region may be greater than the C:O element concentration ratio in the base region. This means that the oxygen atom content in the surface region is greater than the oxygen atom content in the base region. For example, in the surface region, the oxygen atom content may gradually decrease from the surface to be plated toward the base region. In other words, the oxygen atom content in the surface region of the resin composition for plating may gradually increase from the interior of the resin composition for plating toward the surface to be plated.

The oxygen contained in the plating resin composition can bond with the metal components contained in the metal plating film, thereby contributing to improved adhesion of the metal plating film to the surface to be plated. Furthermore, the inclusion of oxygen-containing groups in the surface to be plated improves the hydrophilicity of the surface to be plated, and allows the metal plating film to adhere to the surface to be plated via chemical bonds. The element concentration ratio and oxygen atom content can be measured, for example, using X-ray photoelectron spectroscopy (XPS).

As described above, the resin composition for plating disclosed herein is capable of improving adhesion through chemical bonding, unlike the physical adhesion improvement effect achieved by roughening the surface to be plated, such as the anchor effect. Therefore, according to the present disclosure, a metal plating film can be formed on a resin composition for plating with a smooth surface, without roughening the surface of the resin composition for plating. This makes it possible to provide plated products with a smoother metal plating film and excellent appearance.

For example, the surface of the resin composition for plating may have a maximum height roughness Rz of less than 1 μm. The surface to be plated of the plating composition may be a smooth surface with an Rz of less than 1 μm. If the surface to be plated is roughened, the adhesion of the plating can be improved, but when a member plated on the surface of the resin composition is used in the high frequency band (e.g., the 5 GHz and 6 GHz bands), the conductive properties may deteriorate and transmission loss may increase. According to the present disclosure, the plating can be adhered to a smooth surface with an Rz of less than 1 μm without the need for surface roughening. This can suppress transmission loss in the high frequency range. Therefore, the resin composition for plating of the present disclosure can provide a plated member that can be used effectively even in the high frequency range.

The ten-point average roughness Rz can be measured by a known method using an atomic force microscope (AFM). For example, Rz can be determined by using an AFM to measure a 1 μm x 1 μm measurement area on the surface of the resin composition for plating (the surface to be plated).

[Plating method of the present disclosure]
Next, a plating method according to the present disclosure will be described. The plating method according to the present disclosure includes a surface treatment step of forming a surface region including a plated surface of a resin material, and a plating step of forming a metal plating film on the plated surface.

The surface treatment step involves irradiating the surface to be plated with energy rays to increase the weight-average molecular weight of the surface region of the resin material, thereby forming a surface region with a higher weight-average molecular weight than the base region. Therefore, the surface treatment step can also be understood as a step of forming the above-mentioned resin composition for plating from the resin material.

The surface treatment step involves irradiating the resin material with energy rays from the surface to be plated, where a metal plating film will be formed in the subsequent plating step. In other words, the surface to be plated may be irradiated with energy rays in the surface treatment step. The energy ray irradiation is carried out in an oxygen-containing atmosphere. The oxygen-containing atmosphere may be, for example, air or a mixed gas atmosphere of oxygen gas and an inert gas. Examples of inert gas include nitrogen and argon. When the resin material is irradiated with energy rays in an oxygen-containing atmosphere, the main chain and/or side chain of the resin molecule in the surface region are cleaved, and hydrogen atoms are separated. Next, functional groups such as oxo groups, hydroxyl groups, alkoxy groups, carboxyl groups, and alkoxycarbonyl groups are generated by the surrounding oxygen atoms. The generation of such functional groups increases the molecular weight of the region irradiated with the energy rays. This allows the formation of a surface region with a relatively high weight-average molecular weight.

Functional groups that contribute to an increase in the weight-average molecular weight can be generated by energy rays irradiated onto the resin material. By irradiating energy rays from the plated surface side, the largest number of functional groups can be generated on the plated surface, which is the outermost surface of the resin material, and the amount of functional groups generated by energy ray irradiation can decrease as you move from the plated surface toward the interior of the resin substrate. Therefore, according to the method disclosed herein, the plated surface contains the largest number of functional groups, and the amount of functional groups can decrease as you move from the plated surface toward the base layer region (i.e., the interior side of the resin material). This makes it possible to form a resin composition for plating that has a surface layer region with a higher weight-average molecular weight than the base layer region. Furthermore, it is possible to form a resin composition for plating in which the weight-average molecular weight gradually decreases from the surface layer region to the base layer region.

Energy beam irradiation can include light irradiation, electron beam irradiation, and plasma irradiation. Examples of energy beams that can be used to irradiate the resin material include light rays such as far ultraviolet, ultraviolet, near ultraviolet, and infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, neutron beams, and plasma flows. Considering the efficiency of severing the molecular chains of the resin material and/or forming functional groups, and the ease of obtaining irradiation equipment, it is more preferable that the energy beam irradiated be ultraviolet or electron beam.

The surface treatment step may further include heating the resin material. The surface treatment step may further include heating the resin material in addition to irradiating the surface to be plated with energy rays. Heating may be performed simultaneously with and/or after energy ray irradiation. Preferably, heating is performed simultaneously with energy ray irradiation. Heating in combination with energy ray irradiation causes a dehydration condensation reaction of molecules having oxygen-containing groups generated by energy ray irradiation. The inventors of the present application have newly discovered that a resin composition obtained through the generation of oxygen-containing groups by energy ray irradiation and the subsequent dehydration condensation reaction by heating treatment significantly contributes to improving the adhesion of metal plating films. Without being limited to a particular theory, it is believed that this dehydration condensation reaction causes molecules in the surface region that were cut by energy ray irradiation to recombine with each other via bridging oxygen atoms, thereby increasing the molecular weight of the surface region and improving its strength. Furthermore, the surface region contains bridging oxygen atoms in the polymer structure. As mentioned above, the bridging oxygen atoms contained in the surface region contribute to improving the adhesion of the metal plating film to the plated surface. Thus, by further including a heat treatment in the surface treatment step, it is possible to effectively improve the strength of the surface region and the adhesion of the metal plating film to the plated surface.

The heating temperature used in the surface treatment step may be, for example, 80°C or higher and 300°C or lower, and preferably 100°C or higher and 300°C or lower. The heating time may be 1 minute or higher and 5 minutes or lower. Heating within the above-mentioned temperature range and time period causes the generation of oxygen-containing groups and the subsequent dehydration condensation reaction, which can improve the adhesion of the metal plating film on the resin composition.

After the surface treatment step, the resulting plating resin composition is then subjected to the plating step. In the plating step, a metal plating film may be formed on the surface to be plated of the plating resin composition using a known plating method. The type of plating is not particularly limited, and either wet plating or dry plating may be performed, for example.

For example, the plating resin composition obtained in the surface treatment step may be subjected to electroless plating. In the plating step, various electroless plating processes can be performed, with no particular limitation on the type of metal, such as electroless nickel plating, electroless copper plating, or electroless silver plating. Furthermore, the electroless plating process may be performed using a known plating method.

Furthermore, a metal plating film formed by electroless plating may be subjected to a further plating process. For example, a resin composition having a metal plating film may be subjected to further electroless plating. Alternatively, electroplating may be performed successively on a metal plating film formed by electroless plating. This allows a multi-layer metal plating film to be formed on the resin composition.

A demonstration test was conducted in accordance with this disclosure.

Example 1
The resin material used was a 100 mm x 100 mm x 0.1 mm sheet of cycloolefin polymer (COP) (ZEON Corporation, Zeonor® ZF-16). The surface of the resin material to be plated was irradiated with UV light using a UV irradiation device (Multiply Corporation, MHU-110BK) at 25°C in the atmosphere. The UV irradiance was 8.5 mW/cm, and the irradiation time was 15 minutes. Electroless copper plating was performed on the plating resin composition obtained after UV irradiation. The plated product was then subjected to a vacuum heat treatment at 120°C for 60 minutes, followed by electrolytic copper plating on the electroless copper-plated film to obtain a final plated product. The target film thickness of the electrolytic copper plating was 30 μm. The treatment conditions for electroless copper plating and electrolytic copper plating are shown in Tables 1 and 2, respectively.

Example 2
A plated product was obtained under the same conditions as in Example 1, except that the resin composition was heated at 100° C. simultaneously with the UV irradiation.

Example 3
A plated product was obtained under the same conditions as in Example 1, except that electron beam irradiation was performed using an electron beam irradiation device (EC250, manufactured by I-Electron Beam Co., Ltd.) instead of UV irradiation. The electron beam irradiation was performed at an acceleration voltage of 250 kV and an absorbed dose of 250 kGy. The irradiation time was 10 seconds.

(Comparative Example 1)
Electroless copper plating and electrolytic copper plating were carried out under the same plating conditions as in Example 1, without UV irradiation, to obtain plated products.

(Measurement of weight average molecular weight)
The weight average molecular weight of the surface layer region and base layer region of the resin material of the obtained plated product was measured under the following conditions.
・Equipment: High temperature GPC device (manufactured by Tosoh Corporation, equipment No. HT-GPC-3, HLC-8321GPC/HT)
Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, RI-8020)
Column: TSKgel GMHXL (2 columns) + G2500HXL (1 column) (7.8 mm x 30 cm, manufactured by Tosoh Corporation)
Solvent: Toluene (Nacalai Tesque)
・Flow rate: 1.0mL/min
Column temperature: 80°C
・Injection volume: 0.200mL
Standard sample: Monodisperse polystyrene (manufactured by Tosoh Corporation)

(Evaluation of Adhesion)
The adhesion of the resulting plated products was evaluated by 90° peel test in accordance with JIS C 6471:1995 and JIS C 6481:1996. Specifically, a 10 mm wide cut was made in the electrolytic plating film with a cutter, one end was pinched with a jig, and a peel test was performed in the 90° direction. The measurement conditions and procedure were as follows:
Measuring device: RTF-1210 manufactured by A&D Co., Ltd.
Measurement conditions: Peel copper foil width 10 mm, peel direction 90°, peel speed 50 mm/min

Table 3 shows the weight-average molecular weight measurement results and adhesion evaluation results for each of the plated products of Examples 1 to 3 and the Comparative Example.

As shown in the results in Table 3, the plated products of Examples 1 to 3, which underwent a surface treatment step including energy ray irradiation, differed from the plated products of the Comparative Example, which did not undergo a surface treatment step, in that the weight-average molecular weight in at least the surface region increased, and the weight-average molecular weight in the surface region exceeded the weight-average molecular weight in the base region. Furthermore, the plated products of Examples 1 to 3, which have a larger weight-average molecular weight in the surface region, had higher adhesion strength than the plated product of the Comparative Example, which had the same weight-average molecular weight in the surface and base regions. Furthermore, the plated product of Example 2, in which the weight-average molecular weight in the surface region was further increased by performing a surface treatment step involving heating, was found to have even higher adhesion strength than the plated product of Example 1, in which the difference in weight-average molecular weight between the surface and base regions was relatively small. This demonstrates that having a larger weight-average molecular weight in the surface region contributes to improved adhesion strength.

Furthermore, the plated product of Example 3, which was irradiated with electron beams instead of UV radiation, also exhibited a weight-average molecular weight in the surface region that exceeded that of the base layer region, and adhesion strength was significantly improved compared to the comparative example. On the other hand, when the plated products of Examples 1 to 3 were bent to a bending radius of 0.5 mm, only the plated product of Example 3 exhibited slight whitening in appearance. This is presumably because electron beam irradiation increased the weight-average molecular weight not only in the surface region but also in the base layer region, reducing the difference in weight-average molecular weight between the surface and base layer regions and reducing the flexibility of the resin composition itself. This demonstrates that a plated product with superior flexibility can be obtained when the weight-average molecular weight in the base layer region is smaller than that in the surface region.

The above describes embodiments of the present disclosure, but these are merely typical examples. Those skilled in the art will readily understand that the present disclosure is not limited to these, and that various other embodiments are possible without departing from the spirit and scope of the present disclosure.

It should be noted that the embodiment of the present disclosure as described above includes the following preferred aspects.
<1> A surface layer region including a surface to be plated and a base layer region other than the surface layer region,
The surface layer region has a weight average molecular weight greater than that of the base layer region.
<2> The resin composition for plating according to <1>, wherein the weight average molecular weight of the surface layer region is 1.1 to 2.0 times the average molecular weight of the base layer region.
<3> The resin composition for plating according to <1> or <2>, wherein the surface layer region and the base layer region are regions present within the resin composition for plating, which is a continuous, integrated body.
<4> The resin composition for plating use according to any one of <1> to <3>, wherein the weight average molecular weight gradually decreases from the surface layer region to the base layer region.
<5> The resin composition for plating according to any one of <1> to <4>, wherein the weight average molecular weight in the surface region gradually decreases from the surface to be plated toward the base region.
<6> The resin composition for plating use according to any one of <1> to <5>, wherein the surface to be plated is a smooth surface.
<7> The resin composition for plating use according to any one of <1> to <6>, wherein the oxygen atom content in the surface layer region is greater than the oxygen atom content in the base layer region.
<8> The resin composition for plating use according to any one of <1> to <7>, wherein the resin composition for plating use is a flexible resin composition.
<9> A plated product having a metal plating film on the surface to be plated of the resin composition for plating according to any one of <1> to <8>.
<10> A surface treatment step of forming a surface region including a surface to be plated in a resin material;
a plating step of plating the surface to be plated,
the surface treatment step includes irradiating the surface to be plated with energy rays in an oxygen-containing atmosphere,
The plating method, wherein the surface region has a weight average molecular weight greater than that of a base region other than the surface region.
<11> The method according to <10>, wherein the surface treatment step further comprises heating the surface region.
<12> The method according to <11>, wherein the heating is carried out at least one of simultaneously with the energy ray irradiation and after the energy ray irradiation.
<13> The method according to <11> or <12>, wherein the heating is performed by heating the surface region in a temperature range of 80°C or higher and 300°C or lower.
<14> The method according to any one of <10> to <13>, wherein the energy ray irradiation is performed on the resin material from the side of the surface to be plated.
<15> The method according to any one of <10> to <14>, wherein the energy beam irradiation is carried out using any one selected from the group consisting of ultraviolet light, infrared light, and an electron beam.

The above effects are merely exemplary, and the present disclosure is not limited to the above, and additional effects may also be provided.

Claims (15)

The plated substrate has a surface region including a surface to be plated, and a base region other than the surface region,
The surface layer region has a weight average molecular weight greater than that of the base layer region. The resin composition for plating according to claim 1, wherein the weight average molecular weight in the surface layer region is 1.1 to 2.0 times the average molecular weight in the base layer region. The plating resin composition according to claim 1 or 2, wherein the surface layer region and the base layer region are regions present within the plating resin composition, which is a continuous, integrated body. The resin composition for plating according to any one of claims 1 to 3, wherein the weight-average molecular weight gradually decreases from the surface layer region to the base layer region. The resin composition for plating according to any one of claims 1 to 4, wherein the weight average molecular weight in the surface region gradually decreases from the surface to be plated toward the base region. The plating resin composition according to any one of claims 1 to 5, wherein the surface to be plated is a smooth surface. The plating resin composition according to any one of claims 1 to 6, wherein the oxygen atom content in the surface layer region is greater than the oxygen atom content in the base layer region. The resin composition for plating use according to any one of claims 1 to 7, wherein the resin composition for plating use is a flexible resin composition. A plated product having a metal plating film on the surface to be plated of the plating resin composition according to any one of claims 1 to 8. a surface treatment step of forming a surface region including a surface to be plated in a resin material;
a plating step of plating the surface to be plated,
the surface treatment step includes irradiating the surface to be plated with energy rays in an oxygen-containing atmosphere,
The plating method, wherein the surface region has a weight average molecular weight greater than that of a base region other than the surface region. The method of claim 10, wherein the surface treatment step further comprises heating the surface region. The method of claim 11, wherein the heating is carried out at least one of simultaneously with the energy beam irradiation and after the energy beam irradiation. The method of claim 11 or 12, wherein the heating comprises heating the surface region at a temperature in the range of 80°C or higher and 300°C or lower. The method according to any one of claims 10 to 13, wherein the energy beam irradiation is performed on the resin material from the side of the surface to be plated. The method according to any one of claims 10 to 14, wherein the energy beam irradiation is carried out using any one selected from the group consisting of ultraviolet light, infrared light, and an electron beam.