Silver-containing film and contact material

Abstract

A silver-containing film comprising a silver layer and particles in contact with the silver layer, wherein the particles are composed of a non-conductive hydrocarbon-based polymer having a melting point of 130°C or lower, and wherein the hydrocarbon-based polymer does not include a side chain in a unit molecular structure except for at the terminals, and does not include elements other than carbon and hydrogen in the unit molecular structure.

Description

Silver-containing films and contact materials 【0001】 This disclosure relates to silver-containing films and contact materials. 【0002】 CO ２ With stricter emission regulations, an increase in electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs), which have a lower reliance on fossil fuels, is expected. Because these vehicles require daily battery charging, the contact materials connecting the external power source to the vehicle must withstand a significantly greater number of insertions and removals compared to those used in conventional vehicles. Furthermore, high current flow is required to shorten the charging time. To minimize heat loss at the contacts, it is necessary to apply a surface treatment with low surface contact resistance to both the vehicle body and power source contacts. In this field, highly conductive (low contact resistance) silver (Ag) plating is often used, but the hardness of Ag plating films is generally low, and "seizing" is likely to occur when Ag surfaces slide against each other, making wear a challenge when repeated insertions and removals (sliding) are performed. 【0003】 Therefore, current contact materials for electric vehicle charging terminals require a significantly thicker silver plating film (tens of micrometers thick) compared to the typical silver plating film (several micrometers thick) applied to contact materials, in order to prevent the base material from being exposed due to wear caused by repeated insertion and removal (sliding). This means an increase in the amount of silver required to manufacture charging terminals, leading to higher material costs. Furthermore, forming a thick silver plating film by electroplating requires a long electroplating process, which presents a challenge in terms of significantly reduced productivity. 【0004】 To address these problems, it is effective to cover the surface of the contact material with a silver-containing film that has an abrasion-inhibiting effect, instead of an Ag plating film. Patent documents 1 and 2 disclose a contact material in which the surface is covered with a silver-containing film (particle co-deposited Ag plating film) in which particles of a non-conductive organic compound are contained in a silver layer. 【0005】 Japanese Patent Publication No. 2022-154356 Japanese Patent Publication No. 2024-006857 【0006】Patent documents 1 and 2 describe particles of nonconductive organic compounds contained in a silver-containing film, which have a specific functional group or specific bond (for example, a fluoro group (-F), a methyl group (-CH)) within their unit molecular structure. ３ ), carbonyl group (-C(=O)-), amino group (-NR １ R ２ Particles of organic compounds containing hydroxyl groups (-OH), ether bonds (-O-), and ester bonds (-C(=O)-O-) are disclosed. Because these organic compounds have complex functional group structures, they often require advanced manufacturing processes, which can increase the cost of manufacturing silver-containing films or make it difficult to procure raw materials for manufacturing silver-containing films. 【0007】 This invention has been made in view of the above circumstances, and one of its objectives is to provide a silver-containing film that has sufficient wear resistance, is relatively inexpensive to manufacture, and has readily available raw materials. Another objective of this invention is to provide a contact material having such a silver-containing film. 【0008】 One aspect of the present invention is a silver-containing film comprising a silver layer and particles in contact with the silver layer, wherein the particles are made of a non-conductive hydrocarbon polymer having a melting point of 130°C or lower, and the hydrocarbon polymer does not contain side chains in its unit molecular structure except at the ends, and does not contain elements other than carbon and hydrogen in its unit molecular structure. 【0009】 Aspect 2 of the present invention is the silver-containing film according to aspect 1, wherein the hydrocarbon polymer is a polyethylene polymer. 【0010】 A third aspect of the present invention is a silver-containing film according to aspect 1 or 2, wherein the silver layer has a silver content of 50% by mass or more and 100% by mass or less. 【0011】 Aspect 4 of the present invention is a silver-containing film according to any one of aspects 1 to 3, wherein the particle size D50 at which 50% of the cumulative volume from the fine particle side of the cumulative particle size distribution of the particles is 100 μm or less. 【0012】 Embodiment 5 of the present invention is a silver-containing film according to any one of Embodiments 1 to 4 that satisfies formula (1). 0 ≤ A ｐ / (A ｐ + A Ａｇ ) × 100 ≤ 12.0...(1) In formula (1), A ｐ is the area of the portion of the particles buried in the silver layer in the cross-section in the thickness direction of the silver-containing film, and A Ａｇ is the area of the silver layer in the cross-section in the thickness direction of the silver-containing film. 【0013】 Aspect 6 of the present invention is a contact material including a conductive substrate and a silver-containing film according to any one of Aspects 1 to 5 that covers at least a part of the surface of the conductive substrate. 【0014】 According to one aspect of the present invention, it is possible to provide a silver-containing film having sufficient wear resistance, relatively low manufacturing cost, and easy raw material procurement, and a contact material provided with the silver-containing film. 【0015】Figure 1A is a schematic cross-sectional view in the thickness direction of a silver-containing film according to one embodiment of the present invention. Figure 1B is a schematic cross-sectional view in the thickness direction of a silver-containing film according to another embodiment of the present invention. Figure 2 is a schematic cross-sectional view in the thickness direction of a contact material according to one embodiment of the present invention. Figure 3A is a cross-sectional SEM image in the thickness direction of a sample of a contact material equipped with a silver-containing film made by particle co-deposition plating. Figure 3B is an image cropped from Figure 3A showing only the silver-containing film. Figure 3C is a binarized image of Figure 3B. Figure 4A is a graph showing the measurement results of the wear resistance evaluation test of sample No. 1 of Example 1. Figure 4B is a graph showing the measurement results of the wear resistance evaluation test of sample No. 2 of Example 1. Figure 4C is a graph showing the measurement results of the wear resistance evaluation test of sample No. 3 of Example 1. Figure 4D is a graph showing the measurement results of the wear resistance evaluation test of sample No. 4 of Example 1. Figure 4E is a graph showing the measurement results of sample No. Figure 4F is a graph showing the measurement results of the wear resistance evaluation test for sample No. 6 of Example 1. Figure 4G is a graph showing the measurement results of the wear resistance evaluation test for sample No. 7 of Example 1. Figure 4H is a graph showing the measurement results of the wear resistance evaluation test for sample No. 8 of Example 1. Figure 4I is a graph showing the measurement results of the wear resistance evaluation test for sample No. 9 of Example 2. Figure 4J is a graph showing the measurement results of the wear resistance evaluation test for sample No. 10 of Example 2. Figure 5 is a graph showing the measurement results of the contact resistance of samples No. 1, 9 and 10 of Example 3. 【0016】<Silver-containing films 1, 11> Figures 1A and 1B are schematic cross-sectional views of the thickness direction of silver-containing films 1 and 11 according to embodiments of the present invention. Silver-containing films 1 and 11 include a silver layer 2 and particles 3 in contact with the silver layer 2. The "particles 3 in contact with the silver layer 2" may be particles 3 that are in contact (adhered) to the surface 2a of the silver layer 2, as shown in Figure 1A, or particles 3 that are in contact with the silver layer 2 in a state of co-deposited (embedded) in the silver layer 2, as shown in Figure 1B. In Figure 1B, some of the particles 3 are partially embedded in the silver layer 2, and the remaining particles 3 are completely embedded in the silver layer 2, but the invention is not limited to this, and all particles 3 may be partially embedded, or all particles 3 may be completely embedded. However, if all particles 3 are completely embedded in the silver layer 2, it is desirable to remove a part of the silver layer 2 to expose the particles 3 before use. 【0017】 (Particle 3) Particle 3 consists of a non-conductive hydrocarbon polymer with a melting point of 130°C or lower, composed only of carbon and hydrogen except for the ends. The hydrocarbon polymer has side chains (e.g., fluoro group (-F), methyl group (-CH)) within its unit molecular structure. ３ ), carbonyl group (-C(=O)-), amino group (-NR １ R ２ Hydrocarbon polymers do not contain functional groups such as hydroxyl groups (-OH). Furthermore, hydrocarbon polymers do not contain bonds containing elements other than carbon and hydrogen (i.e., elements that are neither carbon nor hydrogen) within their unit molecular structure (for example, ether bonds (-O-), ester bonds (-C(=O)-O-)). In addition, hydrocarbon polymers may contain branched structures within the macroscopic polymer chain structure formed by the linkage of unit molecular structures. In other words, hydrocarbon polymers are not limited to unbranched polymers, but may also be branched polymers. Moreover, the ends of hydrocarbon polymers may be terminated with the functional groups described above, and may contain elements other than carbon and hydrogen. 【0018】The inventors have discovered for the first time that silver-containing films 1 and 11 can achieve extremely excellent wear resistance by containing particles 3 made of hydrocarbon polymers having the properties described above. Patent documents 1 and 2 use particles made of organic polymers containing the functional groups or bonds described above as particles contained in the silver-containing film, and using such particles yields a silver-containing film with good wear resistance and excellent heat resistance. On the other hand, because such organic polymers have complex functional group structures, advanced manufacturing processes are often required, which can result in high manufacturing costs for silver-containing films or make it difficult to procure raw materials for silver-containing films. 【0019】 The inventors diligently conducted research to obtain silver-containing films 1 and 11 that could achieve both improved wear resistance and reduced manufacturing costs and ease of raw material procurement. They discovered for the first time that by using particles 3 made of a non-conductive hydrocarbon polymer with a melting point of 130°C or lower in the silver-containing films 1 and 11, extremely excellent wear resistance equivalent to or better than that of the silver-containing films disclosed in Patent Documents 1 and 2 can be achieved. Furthermore, since hydrocarbon polymers do not have complex functional group structures, they are easy to manufacture, and as a result, the manufacturing cost of the silver-containing film can be reduced, and the raw materials for the silver-containing film can also be easily procured. 【0020】 The mechanism by which silver-containing films 1 and 11, which contain particles 3 made of non-conductive hydrocarbon polymers with a melting point of 130°C or lower, exhibit extremely excellent wear resistance is assumed to be as follows. However, the present invention is not limited to the assumed mechanism described herein. Hydrocarbon polymers have a simple structure that does not contain functional groups or side chains in their unit molecular structure, so they generally have a low melting point and low molecular structural stability. Therefore, hydrocarbon polymers are thought to easily decompose during sliding and easily convert into surface reaction films (tribo films, lubricating films). Furthermore, by limiting the hydrocarbon polymers to those with a melting point of 130°C or lower, decomposition during sliding becomes particularly likely, and it is estimated that the effect of reducing the friction coefficient of silver-containing films 1 and 11 is remarkably excellent. 【0021】In addition, since the melting point of the hydrocarbon-based polymer that constitutes the particles 3 is low, the heat resistance of the silver-containing films 1 and 11 is inferior to that of the silver-containing films disclosed in Patent Documents 1 and 2. Therefore, when applying the silver-containing films 1 and 11 to a contact material that generates a large amount of heat, such as an application that requires energization with a large current (for charging EVs, PHEVs, etc.), it is desirable to provide a means for cooling the silver-containing films 1 and 11 in order to prevent seizure. On the other hand, general electronic devices such as personal computers and mobile phones are used with low-current energization, so the amount of heat generated at the contact material is small. Therefore, it is not necessary to cool the silver-containing films 1 and 11. Thus, the silver-containing films 1 and 11 with low heat resistance are particularly suitable as contact materials for general electronic devices. 【0022】 That the hydrocarbon-based polymer that constitutes the particles 3 does not contain a functional group in the unit molecular structure can be confirmed by analysis methods such as FT-IR (Fourier transform infrared spectrophotometry), pyrolysis GC-MS (pyrolysis gas chromatography mass spectrometry), and TOF-SIMS (time-of-flight secondary ion mass spectrometry). When analyzing, only the particles 3 may be analyzed, or the entire silver-containing films 1 and 11 including the particles 3 may be analyzed. 【0023】 The melting point of the hydrocarbon-based polymer is measured in accordance with JIS K7121:2012 "Method for Measuring the Transition Temperature of Plastics". 【0024】 The hydrocarbon-based polymer that constitutes the particles 3 is non-conductive. That is, the particles 3 are non-conductive particles. Therefore, even when the particles 3 fall off from the silver-containing film 1 due to sliding, there is no risk of short circuit caused by the particles 3. Here, "non-conductive" means not showing conductivity. For example, the volume resistivity measured based on ASTM D257 is generally 10 ３ [Ω·cm] or more. 【0025】 Examples of the hydrocarbon-based polymer include polyethylene-based compounds. 【0026】The particle size of the particles 3 can be appropriately changed according to the type of hydrocarbon-based polymer used, the required characteristics, etc. In particular, it is desirable that the particle size is such that it is difficult to inhibit the energization of the contact material. For example, as shown in FIG. 1B, when the particles 3 are buried (eutectic) in the silver layer 2, it is desirable that more than half of all the particles have a particle size that can be completely buried in the silver layer 2 (that is, a particle size smaller than the thickness 2t of the silver layer 2). Note that it is not necessary for more than half of all the particles 3 to actually be completely buried in the silver layer 2. 【0027】 The thickness 2t of the silver layer 2 used for the contact material is usually 100 μm or less from the viewpoint of manufacturing cost. Therefore, it is preferable that the particle size D50 (which may be simply referred to as "D50") of 50% cumulative volume from the fine particle side of the cumulative particle size distribution of the particles 3 is 100 μm or less. Thereby, more than half of all the particles 3 can have a particle size that can be completely buried in the silver layer 2. When the particles 3 are arranged (coated or adhered) on the surface of the silver layer 2 as shown in FIG. 1A, the particle size of the particles 3 is not limited by the thickness 2t of the silver layer 2. 【0028】 The D50 of the particles 3 can be obtained by removing the silver layer 2 of the silver-containing layer 11 by dissolution or the like and measuring the remaining particles 3 with a laser diffraction type particle size distribution measuring device. 【0029】 (Silver layer 2) From the viewpoint of conductivity, it is preferable that the silver content of the silver layer 2 is 50 mass% or more and 100 mass% or less. The silver layer 2 can be an Ag plating layer. As the silver layer 2, in addition to soft Ag plating, hard Ag plating, bright Ag plating, and semi-bright Ag plating, etc. used for the surface treatment of ordinary contact materials, Ag alloy plating may be used for the purpose of improving corrosion resistance (such as sulfidation resistance) and wear resistance. However, since wear resistance can be mainly imparted by the particles 3, when there is no purpose other than wear resistance, the silver layer 2 preferably contains, for example, 90 mass% or more of silver, more preferably 95 mass% or more, still more preferably 99 mass% or more, and most preferably formed from a pure silver plating layer (silver content is 100 mass%). The higher the silver content, the more excellent the conductivity of the silver-containing layers 1 and 11 obtained. 【0030】As described above, the thickness 2t of the silver layer 2 can be, for example, 100 μm or less. To measure the thickness of the silver layer 2, first, samples of the silver-containing films 1 and 11 are cut in the thickness direction of the silver-containing films 1 and 11 (in the case of a contact material 100 in which silver-containing films 1 and 11 are formed on the surface 4a of a conductive substrate 4, as shown in Figure 2, this substantially coincides with the direction perpendicular to the surface 4a of the conductive substrate 4). A cross-sectional SEM image of the cross section is obtained to identify the silver layer 2 and measure its thickness. In the SEM image, the silver layer 2 is a relatively bright (i.e., whitish) area. If there are irregularities on the surface 2a of the silver layer 2, the average line of these irregularities is used as the reference line when measuring the thickness 2t of the silver layer 2. The same method is used to determine the reference line for the lower surface 2b of the silver layer 2. The distance between these reference lines is then taken as the thickness 2t of the silver layer 2. The cross-sectional SEM image is taken at a magnification of 1000x, so that the vertical direction of the observation field approximately coincides with the thickness direction of the silver-containing films 1 and 11. The field of view is, for example, 140 μm vertically and 200 μm horizontally. 【0031】 (Particle co-deposition rate) When the particles 3 are embedded in the silver layer 2, as in the silver-containing film 11 in Figure 1B, it is preferable that the following equation (1) is satisfied: 0 (%) ≤ A ｐ / (A ｐ +A Ａｇ ) × 100 ≤ 12.0 (%) ... (1) In equation (1), A ｐ A is the area of ​​the portion of the particles embedded in the silver layer in a cross-section in the thickness direction of the silver-containing film, Ａｇ This is the area of ​​the silver layer in the cross-section in the thickness direction of the silver-containing film. 【0032】 Equation (1) means that the area ratio of particles 3 embedded in the silver layer 2 relative to the entire silver-containing film 11 is 0% or more and 12.0% or less. Since the silver layer 2 containing particles 3 can be formed by the co-deposition plating method (a method of electroplating by placing particles in a plating solution and stirring), the area ratio of the embedded particles is sometimes referred to as the "particle co-deposition rate". 【0033】Although the particles 3 contained in the silver-containing film 11 contribute to the wear resistance of the silver-containing film 11, they are non-conductive. Therefore, if the content of particles 3 in the silver-containing film 11 increases, the conductivity of the silver-containing film 11 may decrease. The particle co-deposition rate is preferably 12.0% or less, which can suppress a significant decrease in the conductivity of the silver-containing film 11 and achieve conductivity similar to that of conventional contact materials equipped with an Ag plating film. The particle co-deposition rate is more preferably 10.0% or less. Note that when the particles 3 are in contact with the surface 2a of the silver layer 2, as shown in Figure 1A, the particle co-deposition rate is 0%. 【0034】 Area A of silver layer 2 Ａｇ This can be determined by binarizing a cross-sectional SEM image parallel to the film thickness direction of the silver layer 2 using image processing software (e.g., "ImageJ"). Specifically, the area A of the silver layer 2 is obtained by following the procedure shown in Figures 3A to 3C. Ａｇ To determine the area of ​​the silver layer 2, in the cross-sectional SEM image of the contact material shown in Figure 3A, the silver layer 2 may appear relatively bright (i.e., whitish), while the protective layer of the cross-sectional SEM sample may appear relatively dark (i.e., blackish). The silver layer 2 (and the particles 3 embedded in the silver layer 2) are trimmed from the SEM image (Figure 3B). Then, for example, the brightness between the silver layer 2 and the protective layer is used as a threshold for binarization (Figure 3C), and the area of ​​the bright part is the area of ​​the silver layer 2, A. Ａｇ In the case of a cross-sectional SEM image, if there are irregularities on the surface 2a of the silver layer 2, the area of ​​the silver layer 2 may be determined by using the average line of these irregularities as the boundary line between the silver layer 2 and the upper layer (for example, the protective layer of the sample for cross-sectional SEM). The same applies to the lower surface 2b of the silver layer 2. 【0035】 On the other hand, the area A of the portion of the multiple particles 3 embedded in the silver layer 2 ｐ This represents the area of ​​the dark portion (corresponding to the hydrocarbon polymer) after binarization (Figure 3C), excluding the portion that protrudes outside the surface 2a of the silver layer 2. In the cross-sectional SEM image, if there are irregularities on the surface 2a of the silver layer 2, the average line of these irregularities is used as the boundary line between the silver layer 2 and the upper layer (for example, the protective layer of the cross-sectional SEM sample), and the area of ​​the particles 3 on the silver layer 2 side of this boundary line is considered to be the portion embedded in the silver layer 2. The same applies to the lower surface 2b of the silver layer 2. 【0036】 The particles contained in the silver-containing films 1 and 11 according to the embodiments of the present invention basically consist only of particles 3 made of hydrocarbon polymers. However, without departing from the object of the embodiments of the present invention, the silver-containing films 1 and 11 may also contain small amounts of other particles other than the hydrocarbon polymer particles 3 (for example, the total amount of these particles may be 10% or less by volume of the total particles). 【0037】 As another example, the silver-containing films 1 and 11 may contain a small amount of inorganic particles (for example, 10% or less by volume of the total particles). As yet another example, the silver-containing films 1 and 11 may contain conductive particles. However, it is preferable that the amount of conductive particles be as small as possible, as this can suppress short circuits at the contacts due to the shedding of conductive particles. For example, it is preferable that 50% or more by volume of the particles contained in the silver-containing films 1 and 11 are non-conductive particles 3, more preferably 60% or more by volume, 70% or more by volume, 80% or more by volume, or 90% or more by volume, and even more preferably that all (100% by volume) are non-conductive particles 3. 【0038】 <Contact Material 100> Figure 2 shows a contact material 100 equipped with a silver-containing film 11. The contact material 100 includes a conductive substrate 4 and a silver-containing film 11 that covers at least a portion of the surface 4a of the conductive substrate 4. Because the contact material 100 is equipped with the silver-containing film 11 according to this embodiment, it has extremely excellent wear resistance, is inexpensive to manufacture, and has easy raw material procurement. The conductive substrate 4 may be, for example, a metal foil made of copper or a copper alloy. The contact material 100 may include other layers (for example, a strike plating layer, etc.) to achieve the objectives of the present invention. The contact material 100 may include a silver-containing film 1 as shown in Figure 1A instead of the silver-containing film 11. 【0039】 <Method for manufacturing contact material 100> In manufacturing the contact material 100 equipped with a silver-containing film 11, a predetermined amount of particles 3 are dispersed in a silver (or silver alloy) plating solution, and an electric current is passed through it while stirring to perform a silver plating treatment on a conductive substrate 4. This makes it possible to form a silver-containing film 11 in which a predetermined amount of particles 3 are embedded (co-deposited) in the silver layer 2. 【0040】In the process of electroplating by dispersing particles 3 in a plating solution, the following reactions (A) and (B) proceed simultaneously: - (A) A reaction in which the dispersed particles in the solution are electrostatically or physically adsorbed (in contact) with the surface of the conductive substrate 4. - (B) A reaction in which the silver layer 2 is deposited (grown) on the surface of the conductive substrate 4. Then, the particles 3 adsorbed on the conductive substrate 4 in (A) are incorporated into the silver layer 2 deposited in (B), resulting in "eutectoid formation". Under conditions in which eutectoid plating proceeds steadily, the particles 3 adsorbed in the initial stages of the reaction are incorporated into the silver layer 2, and at the same time, the adsorption of new particles 3 occurs. For this reason, even when the plating process is stopped, the exposure of particles 3 on the outermost surface can often be seen. In a normal eutectoid plating process, a contact material 100 containing particles 3 in which some are embedded in the silver layer 2 and the remaining parts are exposed on the surface of the silver layer 2 can be easily manufactured. 【0041】 Here, the amount of particles 3 co-deposited into the silver layer 2 (for example, the area ratio of particles 3) is determined by the balance between the adsorption frequency of (A) and the plating film growth rate of (B). Therefore, it is possible to change the amount of co-deposited particles by changing the plating conditions, such as the amount of particles 3 dispersed in the plating solution. For example, by performing the plating process using a plating solution that does not contain particles 3 towards the end of the plating process, or by changing the stirring speed of the plating solution to reduce the adsorption frequency of (A), it is possible to create a layer on the outermost surface of the plating where particles 3 do not co-deposit, thereby producing a silver-containing film 11 in which all particles 3 are embedded in the silver layer 2. 【0042】 One example of a method for manufacturing a contact material containing a silver-containing film 1 as shown in Figure 1A is to form a silver layer 2 without particles 3 on the surface 4a of a conductive substrate 4 by plating, and then apply a dispersion liquid containing particles 3 to the surface 2a of the silver layer 2, and evaporate the dispersion medium. 【0043】 The embodiments of the present invention will be described in more detail below with reference to examples. The embodiments of the present invention are not limited by the following examples, and can be implemented with appropriate modifications within the scope that is consistent with the spirit described above and below, and all such modifications are included within the technical scope of the embodiments of the present invention. 【0044】<Preparation of a sample for wear resistance evaluation (silver-containing film: particle-coated plating)> The wear resistance of the silver-containing film 1, in which particles 3 come into contact with (adhere to) the surface 2a of the silver layer 2 (Ag plating), was evaluated. A pure copper plate with a thickness of 0.3 mm was used as the plating substrate, and the surface was degreased by acetone cleaning. Next, as the base for the plating process, a commercially available Strike Ag plating solution (Dyne Silver GPE-ST manufactured by Yamato Kasei Co., Ltd.) was used, and a Pt-coated Ti plate was used as the counter electrode at 5 A / dm ２ A current density of approximately 0.1 μm was applied for 1 minute to perform a strike Ag plating treatment. Subsequently, a commercially available non-cyanide semi-bright Ag plating solution (Dain Silver GPE-SB, Yamato Kasei Co., Ltd.) was used, with a pure Ag plate as the counter electrode, and a current density of 3 A / dm was applied. ２ A semi-gloss Ag plating layer approximately 10 μm thick was formed by applying current at the specified current density for 5 minutes. Samples for evaluating abrasion resistance (Ag plating sample: Sample No. 1, particle-coated plating samples: Samples No. 2-8) were prepared by dropping a solution of particles suspended in alcohol onto the surface of the semi-gloss Ag plating layer and drying it. 【0045】 In sample No. 1, the particle alcohol suspension was not applied. The particles used to prepare samples No. 2 to 8 were as follows: Sample No. 2 (Polypropylene (PP)): Seishin Corporation, Polypropylene powder (PPW-5J), particle size 5 μm Sample No. 3 (Polyethylene (PE)): Mitsui Chemicals, Polyethylene powder (Mipelon PM-200), particle size 10 μm Sample No. 4 (Polyethylene (PE)): Shamrock, Polyethylene powder (S-379 H), particle size 9 μm Sample No. 5 (Polyethylene (PE)): Sumitomo Seika, Polyethylene powder (Flowbeads CL-2080), particle size 11 μm Sample No. 6 (Polyethylene (PE)): Shamrock, Polyethylene powder (S-394 N1), particle size 6 μm 7 (Polyethylene (PE)): Shamrock, polyethylene powder (S-395 N2), particle size 6 μm. Sample No. 8 (Polyethylene (PE)): Honeywell, polyethylene powder (AC umist B6), particle size 6 μm. 【0046】<Wear Resistance Evaluation Test> As a reciprocating sliding test using a ball-on-disk test device (CSM: Tribometer), a mating material consisting of a φ6 mm high-carbon chromium bearing steel (SUJ2) ball was slid against the metal-organic compound composite material under test. One cycle consisted of one reciprocation with a vertical load of 1 N, a sliding width (sliding stroke) of 10 mm, and an average sliding speed of 30 mm / second. The test was performed for 50 cycles. The maximum value of the coefficient of friction (ratio of horizontal load to vertical load) was measured in each sliding cycle, and the coefficient of friction μ up to the 50th cycle was read. Excluding the data from the initial cycles (cycles 1-4) where the coefficient of friction (sliding state) had not yet stabilized, the arithmetic mean (average coefficient of friction μ) of the coefficient of friction μ from cycles 5 to 50 was calculated. ａｖｅ The average friction coefficient μ was calculated for two samples (n=2) used for wear resistance evaluation. ａｖｅ We calculate the arithmetic mean of these values, and the average friction coefficient μ of the two samples. ａｖｅ（２） This was done. , μ ａｖｅ（２） A value of ≤0.400 is considered to have extremely excellent friction-improving effects and is classified as "Excellent". μ ａｖｅ（２） A score of 0.400 was marked as "Fail". "Excellent" was considered a pass, and "Fail" was considered a fail. 【0047】 The results above are summarized in Table 1 and Figures 4A to 4H. 【0048】 【0049】 Samples No. 4 to 8 (Figures 4D to 4H), which satisfy the requirements of the embodiments of the present invention, were confirmed to maintain a stable low coefficient of friction (0.185 to 0.234) up to the 5th to 50th cycle. Furthermore, the average coefficient of friction μ of the two samples for samples No. 4 to 8 was confirmed to be... ａｖｅ（２） It satisfied the ≤0.400 requirement and demonstrated excellent friction-improving effects. 【0050】 Sample No. 1 (Comparative Example) is a simple Ag plating layer in which the silver-containing film does not contain hydrocarbon polymer particles, therefore the average friction coefficient μ of the two samples is... ａｖｅ（２） The ratio was remarkably high at 1.058, and since it easily seized up with the mating material, it was confirmed to have poor wear resistance. 【0051】Sample No. 2 (Comparative Example) contains polypropylene particles in the silver-containing film, and the average friction coefficient of the two samples is μ ａｖｅ（２） The average coefficient of friction μ was 0.417, which was superior to that of sample No. 1 in terms of wear resistance. ａｖｅ（２） Since the value was >0.400, it was not possible to achieve the extremely excellent wear resistance required in the embodiment of the present invention. 【0052】 Sample No. 3 (Comparative Example) contains high-melting-point (136°C) polyethylene particles in the silver-containing film, and the average friction coefficient of the two samples is μ ａｖｅ（２） The value was 0.931, which was superior to sample No. 1. However, the average coefficient of friction μ ａｖｅ（２） Since the value was >0.400, it was not possible to achieve the extremely excellent wear resistance required in the embodiment of the present invention. 【0053】 <Preparation of Abrasion Resistance Evaluation Samples (Silver-Containing Film: Particle Co-deposition Plating)> The abrasion resistance of a silver-containing film 11 in which particles 3 were co-deposited (embedded) in a silver layer 2 (Ag plating) was evaluated. Similar to Example 1, a pure copper plate was used as the plating substrate and subjected to strike Ag plating to a thickness of approximately 0.1 μm, followed by co-deposition plating. The co-deposition plating was performed using the same plating solution and conditions as those used to form the semi-gloss Ag plating layer in Example 1. A predetermined amount of particles 3 were dispersed in the plating solution, and the plating process was carried out while stirring. This produced abrasion resistance evaluation samples (particle co-deposition plating samples: samples No. 9-10) in which each particle was incorporated (co-deposited) into the Ag plating layer. A surfactant (dispersant) was added to the plating solution to prevent aggregation of particles in the Ag plating layer and to maintain a stable dispersion state. The amount of particles dispersed in the plating solution (amount dispersed in the solution), the type and amount of surfactant used, and the particle co-deposition rate are shown in Table 2. Sample No. In both cases 1 and 2, the particle co-deposition rate was 12.0% or less. 【0054】<Wear Resistance Evaluation Test> The obtained particle eutectoid plated samples were subjected to friction sliding tests under the same conditions as in Example 1. However, the number of samples tested was limited to three (n=3). The arithmetic mean of the friction coefficient μ for cycles 5 to 50, excluding the data from the initial cycles (cycles 1 to 4), was calculated (average friction coefficient μ). ａｖｅ ) is calculated, and the average friction coefficient μ of the three samples is calculated. ａｖｅ（３） That's what I decided. 【0055】 【0056】 Samples No. 9 and 10 (Figures 4I and 4J), which satisfy the requirements of the embodiments of the present invention, were confirmed to maintain a stable low coefficient of friction (0.125 to 0.157) from the 5th to the 50th cycle. Furthermore, the average coefficient of friction of the three samples μ for samples No. 9 and 10 was confirmed to be... ａｖｅ（３） It satisfied the ≤0.400 requirement and demonstrated excellent friction-improving effects. 【0057】 <Measurement of Contact Resistance> For samples No. 1, 9, and 10, the contact resistance was measured using an electrical contact simulator (manufactured by Yamazaki Seiki Kenkyusho). The applied loads were 2N, 3N, 4N, and 5N, and the contact resistance was measured at each load. The contact resistance was measured at three locations, and the average of the obtained measurements is summarized in Table 2. Figure 5 shows a graph plotted with the applied load on the horizontal axis and the contact resistance (average value) on the vertical axis. 【0058】 【0059】 As can be seen from Table 3 and Figure 5, samples No. 9 and 10 (particle co-deposition plating samples) had contact resistance equivalent to that of sample No. 1 (Ag plating sample). This confirms that a contact material equipped with a silver-containing film 11 made of particle co-deposition plating can achieve conductivity equivalent to that of a contact material equipped with a silver-containing film made of an Ag plating layer. Furthermore, the contact resistance values ​​of samples No. 1, 9, and 10 were sufficiently low, at 0.50 [mΩ] or less, under all load conditions from 2 to 5 N. Since the particles used in the particle co-deposition plating of samples No. 9 and 10 were non-conductive particles, no short circuits occurred due to particle detachment in samples No. 9 and 10. 【0060】This application is based on a priority claim to Japanese Patent Application No. 2024-217710, filed on December 12, 2024, and Japanese Patent Application No. 2025-204036, filed on November 26, 2025. Japanese Patent Applications No. 2024-217710 and No. 2025-204036 are incorporated herein by reference. 【0061】 1.11 Silver-containing film 100 Contact material 2 Silver layer 2a Surface of the silver layer 2b Underside of the silver layer 3 Particles 4 Conductive substrate 4a Surface of the conductive substrate

Claims

1. A silver-containing film comprising a silver layer and particles in contact with the silver layer, wherein the particles are made of a non-conductive hydrocarbon polymer having a melting point of 130°C or lower, and the hydrocarbon polymer does not contain side chains in its unit molecular structure except at the ends, and does not contain elements other than carbon and hydrogen in its unit molecular structure.

2. The silver-containing film according to claim 1, wherein the hydrocarbon polymer is a polyethylene polymer.

3. The silver-containing film according to claim 1, wherein the silver layer has a silver content of 50% by mass or more and 100% by mass or less.

4. The silver-containing film according to claim 1, wherein the particle size D50 at which 50% of the cumulative volume from the finest particle side of the cumulative particle size distribution of the particles is 100 μm or less.

5. A silver-containing film according to claim 1, satisfying formula (1). 0 ≤ A ｐ / (A ｐ +A Ａｇ ) × 100 ≤ 12.0 ... (1) In equation (1), A ｐ A is the area of ​​the portion of the particles embedded in the silver layer in a cross-section in the thickness direction of the silver-containing film, Ａｇ This is the area of ​​the silver layer in the cross-section in the thickness direction of the silver-containing film.

6. A contact material comprising a conductive substrate and a silver-containing film according to any one of claims 1 to 5, covering at least a portion of the surface of the conductive substrate.

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