JP2001107255A - Method of metal plating for electrical non-conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy method of application of metal plating to a material composed of electrical non-conductor e.g. silicone rubber conventionally considered to be difficult or incapable of plating with metal. SOLUTION: Moisture curing resin is applied to the surface of a basis material composed of an electrical non-conductor, and this moisture curing resin is dried and cured to form a primer layer. Then a metallic catalyst having catalytic activity to electroless plating metal is brought into contact with the above primer layer to form a metallic catalyst layer. Further, electroless plating is applied to form a metal plating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for plating a metal on an electrically nonconductive material, and more particularly, to a method for plating a metal such as silicone rubber, polyethylene rubber or EPR (ethylene-propylene-rubber), which has been difficult or impossible. The present invention relates to a method in which metal plating can be easily applied to an electric nonconductor that has been impossible.

[0002]

2. Description of the Related Art It is generally difficult to apply metal plating to the surface of an electrically nonconductive material such as plastic.
This is because the surface of the non-conductive base material is smooth and it is difficult to form a catalytic metal layer as a pretreatment. Therefore, conventionally, mechanical treatment such as blasting or liquid honing is performed on the surface of the nonconductive substrate to roughen the surface, or after chemically roughening the surface with a strong chemical such as chromic acid,
A method of forming a metal plating layer on the surface of a base material using a catalyst has been adopted.

However, in the method of mechanically roughening the surface of a base material and applying metal plating as described above, it is difficult to perform the treatment on a complicated portion of an article having a complicated external shape, and it is difficult to uniformly perform the treatment. It is pointed out that various defects such as poor appearance after plating and poor peeling due to poor adhesion are not obtained. In addition, in a method of performing metal plating after chemically roughening the surface of a base material (etching), an appropriate treatment in accordance with the type of the base material is indispensable, and there is a disadvantage in that it is inferior in versatility.

[0004] As a treatment suitable for a base material, for example, AB
It is known to perform surface roughening on an S-based material with a sulfuric acid-chromic anhydride solution. According to this, a high quality appearance and good adhesion are obtained, and this is widely used as a standard formulation for plastic plating. Since the present invention relates to a method for plating a non-conductive material with a metal, an outline of a conventionally practiced metal plating method for an ABS-based material will be described first for the sake of understanding.

[0005] First, the surface of an ABS-based material to be plated is subjected to a roughening treatment by oxidation, for example, by etching with dichromic acid, and then a catalytic substance (described later).
Immerse in a conditioner to improve the adhesion. Subsequently, washing is performed, for example, by immersing in a catalyst bath of palladium / tin to provide a catalyst indispensable for the deposition of electroless plating, and in order to deposit the catalyst more efficiently, accelerated treatment, for example, immersion in sulfuric acid is performed. Apply.

Next, a conductive step for forming a conductive layer is performed. In the conductive step, the ABS material is immersed in, for example, a nickel electroless plating bath for a predetermined time to perform electroless plating, and electroless plating to be a conductive layer is deposited on the surface. This conductive process,
It is essential for the subsequent electroplating process. The ABS-based material that has been subjected to the conductive process is subjected to electroplating as necessary, and a metal plating layer of, for example, nickel is formed. This electroplating step is completed by immersing the ABS-based material in a nickel sulfamate bath for a predetermined period of time and energizing the conductive layer to deposit a nickel metal film to a desired thickness.

[0007] Materials other than the above-mentioned ABS materials include, for example, polyphenylene oxide resin, polypropylene resin, polycarbonate resin, polycarbonate alloy, polyacetal resin, nylon resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene sulfide resin, and polyphenylene sulfide resin. With respect to etherimide resin and the like, it is possible to form a practicable plating by an established pretreatment method including a chemical roughening step corresponding to each material.

[0008]

However, as described above, even though a pretreatment method corresponding to various resins has been established, a conductive filler may be contained in the material or an alloy may be contained.
There are many restrictions, such as the need for alloying and pre-etching with an organic solvent as a pre-treatment, so that there is a difficulty in forming a plating on a non-conductor with a low degree of freedom. Generally, plating of rubbers has not been possible with the prior art.

In recent years, interest in various water pollutants has increased, and a wide range of regulations have been imposed on the disposal of water pollutants. Therefore, it is pointed out that the waste liquid such as hexavalent chromium generated by the chemical roughening treatment using the sulfuric acid-chromic anhydride solution described above increases the cost required for post-treatment to satisfy the above regulations.

[0010]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the problems inherent in the prior art metal plating method for electrically nonconductive materials, and has been proposed to solve the problems suitably. However, it is an object of the present invention to provide a method for easily performing metal plating on an electrically nonconductive material, for example, silicone rubber or other materials, for which metal plating has conventionally been difficult or impossible.

[0011]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems and achieve the intended object, the metal plating method for an electrically non-conductive material according to the present invention employs a method in which the surface of an electrically non-conductive substrate is exposed to moisture. A curable resin is applied, and the moisture-curable resin is dried and cured to form a primer layer, and then a catalytic metal having catalytic activity on an electroless plating metal is brought into contact with the primer layer to form a catalytic metal layer. The catalyst metal layer is formed by electroless plating to form a required metal plating layer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a method for plating metal on an electrically non-conductive material according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. The inventor of the present application
By applying a moisture-curable resin primer as a pre-treatment step to a substrate made of, for example, silicone rubber, for which metal plating could not be formed until now, surface roughness can be achieved using mechanical or chemical means. It has been found that a metal plating layer having high adhesiveness can be easily formed without performing the oxidizing treatment.

As shown in FIG. 1, the method for plating metal on an electrically nonconductive material according to the present invention is roughly divided into a pretreatment step S1 and a conductive step S2. And the pre-processing step S1
As shown in FIG. 2, a moisture-curable resin 2 (described later) is applied to an electrically nonconductive base material (rubber member) 10 by means such as spray coating.
It comprises a primer applying step S11 for giving 0, and a drying step S12 for drying the primer layer 12 formed of the moisture-curable resin 20 by a predetermined means.

As shown in FIGS. 1 and 3, the conductive step S2 performed after the pre-processing step S1
A catalyst adsorption step S in which the upper primer layer 12 adsorbs a catalyst metal 22 containing desired fine metal particles exhibiting catalytic activity for electroless plating to form a catalyst metal layer 14.
21 and an electroless plating step S22 of applying a metal plating layer 16 having a predetermined thickness on the catalyst metal layer 14 by immersing the plating metal 30 in a plating bath 30 of an appropriately selected plating metal 24. After each of the above steps, the inspection in the inspection step S3 is performed to complete the application of the metal plating to the electric nonconductor. In some cases, the electroless plating step S22
Subsequently, an electrolytic plating step S23 is performed to form a thicker metal plating layer 16. The electrolytic plating step S23 is selectively performed as appropriate in accordance with various physical properties (eg, conductivity) required for the electrically non-conductive material.

The substrate to be plated in the present invention can be selected without any problem as long as it is a substance which has been extremely difficult to be metal-plated and which can impart the moisture-curable resin to the surface. I can do it. Preferable examples include silicone rubber, natural rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene / propylene rubber, polyethylene, polypropylene, and polyacetal, and other general polymer materials and highly polar inorganic materials. Can also be provided.

The moisture-curable resin used in the present invention is mainly known in the field of adhesives, and has a property of causing cross-linking in a structure by absorbing moisture in the air and solidifying by the cross-linking. Generally, a resin composition containing a resin having the same is referred to. This moisture-curable resin is applied on the substrate in a thickness of about 1 to 100 μm depending on the type of the substrate and the like. Suitable moisture curable resins include:
Examples include a moisture-curable silicone resin, a cyanoacrylate resin, or a urethane-based moisture adhesive. The moisture-curable silicone resin has a hydrolyzable functional group in the structure,
Condensation reaction occurs with the silanol group generated by the moisture to cause cross-linking, and by the condensation reaction by-product deviating from the oligomer by the condensation reaction, acetic acid type, alcohol type, oxime type, Amine type, amide type,
It is classified into aminoxy type and acetone type. The cyanoacrylate resin is widely known as an instant adhesive, and is cured by promoting a polymerization reaction in the composition by moisture. The urethane-based moisture adhesive contains an oligomer at an isocyanate group terminal in the structure, and an amino group resulting from a reaction between the isocyanate group and moisture further reacts with another isocyanate group to form a crosslink. It is produced and hardened.

Since these moisture-curable resins generally have a high viscosity, they can be applied by coating with a roll coater or the like. Since the concentration can be adjusted with a solvent such as xylene, a uniform and thin primer layer can be easily formed. Further, since the composition is cured by the atmospheric humidity, the curing rate can be easily controlled by controlling the humidity at the time of application to the substrate. Moisture-curable resins have a high physical adhesion capacity to various substances and a large number of functional groups that remain in the structure in an unreacted state after curing or that are newly generated by reaction with moisture. By capturing a catalytic metal colloid described later or a surfactant functional group that stabilizes the colloid, and consequently adsorbing a large number of the catalytic metal, indirectly provides strong adhesion of the plating layer. It is presumed that it is doing.

As the catalytic metal used in the present invention, those having catalytic activity for the electroless plating reaction described below are preferable, and examples thereof include gold, silver, ruthenium, rhodium, palladium, iridium, osmium and platinum. And
It is used under colloidal conditions. In order to produce a colloid of the catalyst metal, a method of dissolving a water-soluble salt containing the catalyst metal, adding a surfactant, and adding a reducing agent with vigorous stirring is generally used. May be used. As the surfactant, anionic or cationic, for example, soap, higher alcohol sodium sulfate, sodium alkylbenzene sulfonate,
Sodium polyoxyethylene alkyl ether sulfate and the like, lauryl trimethyl ammonium chloride, alkylbenzyl dimethyl ammonium chloride and the like are appropriately and selectively adopted according to the catalyst metal.
Since the catalyst metal layer formed here acts as a nucleus when forming a metal plating layer by electroless plating described later, it is not necessary to form a continuous layer on the primer layer, and the catalyst layer is dispersed and adsorbed. Just do it.

Further, as the metal for electroless plating used in the present invention, electroless copper, electroless copper, nickel,
Phosphorus alloy, electroless nickel-phosphorus alloy, electroless nickel-boron alloy, electroless cobalt-phosphorus alloy, electroless gold,
Electroless silver or electroless palladium may, for example, be mentioned. Depending on the degree of conductivity of the metal plating layer applied to the base material, the metal plating layer may be formed through an electrolytic plating step as needed. In this case, as the plating metal, in consideration of the transition to the electrolytic plating step, from the viewpoint of cost and stability, use is made of electroless copper or electroless nickel.
Phosphorus alloys are preferred.

The preferred embodiment of the method for plating metal on an electrically nonconductive material according to the present invention will be described below, but the present invention is not limited thereto.

[0021]

First Embodiment A silicone rubber sheet (product name: manufactured by Toshiba GE Silicone Co., Ltd.) having dimensions of 100 × 100 × 3 mm was used as a substrate used in this example. The following operation was performed to form a metal plating layer on one side of the silicone rubber sheet. As a pretreatment step, a primer application step: a 50% xylene solution of a moisture-curable silicone resin (trade name: Super X: manufactured by Cemedine Co.) is applied to the silicone rubber sheet so that the dry thickness of the primer layer becomes 10 μm. Spray applied. Drying stage: Drying was performed at a temperature of 60 ° C. for 30 minutes using a high-temperature oven capable of setting a temperature. As a conductive process, a catalyst adsorption step: palladium chloride (PdCl ₂ ) 0.089
g / L and 0.146 g / L of sodium chloride (NaCl) in a pure aqueous solution containing 0.1 g / l of stearyltrimethylammonium chloride (product name Cotamine 86P Conc).
To the main solution to which L was added, add 0.07
By vigorously stirring while adding a solution in which 6 g of sodium borohydride (NaBH ₄ ) was dissolved, a black-brown transparent palladium colloid catalyst solution was prepared. This palladium colloid catalyst solution is sufficiently applied by spray coating on the silicone rubber sheet prepared in the pretreatment step, and then the temperature is set to 100 ° C. in a high temperature oven capable of setting the temperature.
C. and dried for 30 minutes. Electroless plating stage: Electroless nickel plating bath (product name: TMP Chemical Nickel: Okuno Pharmaceutical Co., Ltd .: standard formulation)
Performed at a temperature of 10 ° C. for 10 minutes. Electroplating step: Bright nickel bath (product name # 6)
6: EBARA Eugerite Co., Ltd .: standard formulation) at a temperature of 30 ° C.
It is carried out for 30 minutes under the condition of a current intensity of 2 A / dm ² , and 12
A metal plating layer of nickel metal having a thickness of μm was formed.

In order to evaluate the adhesion of the metal plating layer obtained through each of the above steps, the sheet-like material provided with the metal plating layer was fixed to an iron plate with a moisture-curing adhesive Super X and tested. A piece was prepared, and the adhesion was measured according to "Electroplating for decoration on plastic Annex 6 Adhesion test method" specified in JIS H 8630. Specifically, two parallel cuts with a width of 10 mm are made in the metal plating layer, and the cuts are caused by the cuts, and a peeled portion of about 20 mm formed by pliers or the like is fixed to a head of a tensile tester, and the peeling is performed. The load cell value was measured by pulling under the condition that the angle between the part and the substrate (iron plate) was 90 ° and the head moving speed was 25 mm / min. The load cell value at this time was about 14.7 N / cm, and sufficient adhesion was confirmed.

[0023]

Second Embodiment As a substrate used in this embodiment, a soft polyvinyl chloride sheet having dimensions of 100.times.100.times.0.125 mm was used. On both sides of this vinyl sheet,
The following operation was performed to form a metal plating layer. As a pretreatment step, a primer application step: a moisture-curable silicone resin (trade name: Super X: manufactured by Cemedine Co.) is applied to a soft polyvinyl chloride sheet so that the primer layer has a dry thickness of 5 μm. The coating was applied by a roll coater under the supply of air. Drying step: The resin was dried at the same time as the resin was applied by supplying dry air. As a conductive process, a catalyst adsorption step: palladium chloride (PdCl ₂ ) 0.089
g / L and 0.146 g / L of sodium chloride (NaCl) in a pure aqueous solution containing 0.1 g / l of stearyltrimethylammonium chloride (product name Cotamine 86P Conc).
To the main solution to which L was added, add 0.07
By vigorously stirring while adding a solution in which 6 g of sodium borohydride (NaBH ₄ ) was dissolved, a black-brown transparent palladium colloid catalyst solution was prepared. The palladium colloid catalyst solution was sufficiently applied to the soft polyvinyl chloride sheet produced in the pretreatment step by spray coating, and then dried at a temperature of 100 ° C. for 30 minutes in a high temperature oven capable of setting the temperature. Electroless plating step: An electroless copper plating bath (product name Omnishield 1598: manufactured by Shipley Far East Co., Ltd .: standard blending) was carried out at 30 ° C. for 10 minutes. Electroplating step: Next, bright copper sulfate bath (product name UBA
C-EPII: manufactured by EBARA Eugelite Co., Ltd .: standard blending) was carried out at a temperature of 25 ° C. and a current intensity of 4 A / dm ² for 15 minutes to form a 12 μm thick copper metal plating layer.

In order to evaluate the adhesion of the metal plating layer obtained through each of the above steps, the sheet-like material provided with the metal plating layer was fixed to an iron plate with a moisture-curing adhesive Super X, and the test piece was used. It was prepared and the adhesion was measured in accordance with "Decorative electroplating on plastics Appendix 6 Adhesion test method" specified in JIS H 8630. Specifically, two parallel cuts with a width of 10 mm are made in the metal plating layer, and the cuts are caused by the cuts, and a peeled portion of about 20 mm formed by pliers or the like is fixed to a head of a tensile tester, and the peeling is performed. The load cell value was measured by pulling under the condition that the angle between the part and the substrate (iron plate) was 90 ° and the head moving speed was 25 mm / min. The load cell value at this time was about 9.8 N / cm, and sufficient adhesion was confirmed.

[0025]

Third Embodiment As a substrate used in this embodiment, an EPDM rubber sheet (manufactured by INOAC Elastomer Co., Ltd.) having dimensions of 100.times.100.times.3 mm was used. The following operation was performed to form a metal plating layer on both sides of the EPDM rubber sheet. As a pretreatment step, a primer application step: for an EPDM rubber sheet,
A 50% xylene solution of a moisture-curable silicone resin (trade name: Super X: manufactured by Cemedine Co., Ltd.) was spray-coated so that the dry thickness of the primer layer was 10 μm. Drying stage: Drying was performed at a temperature of 60 ° C. for 30 minutes using a high-temperature oven capable of setting a temperature. As a conductive process, a catalyst adsorption step: sodium tetrachloroaurate (III) (N
a pure water solution of _{aAuCl 4 · 2H 2 O) 0.199g} / L,
To a main solution to which 0.1 g / L of stearyltrimethylammonium chloride (product name Cotamine 86P Conc) was added, a solution in which 0.076 g of sodium borohydride (NaBH ₄ ) was previously dissolved in a small amount of pure water was added. While stirring vigorously, a red transparent gold colloid catalyst solution was prepared. This gold colloid catalyst solution was sufficiently applied by spray coating on the EPDM rubber sheet produced in the pretreatment step, and then washed with water. Then, it was dried at a temperature of 100 ° C. for 30 minutes in a high temperature oven capable of setting a temperature. An electroless copper plating bath (product name Omnishield 1598: manufactured by Shipley Far East Co., Ltd .: standard formulation) was carried out at a temperature of 30 ° C. for 30 minutes. Then, an activation bath containing palladium chloride (Omnishield 1501: manufactured by Shipley Far East Co., Ltd .: standard formulation) was carried out at a temperature of 25 ° C. for 1 minute, washed sufficiently with water, and finally an electroless nickel plating bath (product name) Omnishield 1580: manufactured by Shipley Far East Co., Ltd .: standard formulation) at 30 ° C. for 15 minutes. By the two-stage electroless plating described above, an EPDM rubber sheet was formed in which a copper plating layer and a nickel plating layer were formed and laminated in a thickness of 1 μm each.

In order to evaluate the adhesion of the metal plating layer obtained through each of the above steps, the sheet-like material provided with the metal plating layer was fixed to an iron plate with a moisture-curing adhesive Super X, and the test piece was used. It was prepared and the adhesion was evaluated according to the “tape test method” in the “plating adhesion test” specified in JIS H8504. Specifically, a square streak having a side of 2 mm was completely formed with a cutter to completely penetrate the metal plating layer, and a cellophane tape having a width of 12 mm was pressed for 10 seconds to be adhered. Next, the cellophane tape was instantaneously peeled off under conditions perpendicular to the metal plating layer surface, and the peeled state was confirmed. No peeling was observed in the metal plating layer according to this example. After a dipping treatment in hot water at 60 ° C. for 4 hours, a similar peeling test was performed, but no peeling occurred, and it was confirmed that a strong metal plating layer was formed.

[0027]

Fourth Embodiment A natural rubber sheet having dimensions of 100.times.100.times.1 mm was used as a substrate used in this embodiment.
The following operation was performed to form a metal plating layer on one side of the natural rubber sheet. As a pretreatment process, a primer application step: a natural rubber sheet is applied to a cyanoacrylate resin (flash adhesive: trade name Cemedine 3)
000D: manufactured by Cemedine Co.) was applied by brush coating so that the dry thickness of the primer layer became 10 μm. Drying stage: Drying was performed at a temperature of 60 ° C. for 30 minutes using a high-temperature oven capable of setting a temperature. As a conductive process, a catalyst adsorption step: palladium chloride (PdCl ₂ ) 0.089
g / L and 0.146 g / L of sodium chloride (NaCl) in a pure aqueous solution containing 0.1 g / l of stearyltrimethylammonium chloride (product name Cotamine 86P Conc).
To the main solution to which L was added, add 0.07
By vigorously stirring while adding a solution in which 6 g of sodium borohydride (NaBH ₄ ) was dissolved, a black-brown transparent palladium colloid catalyst solution was prepared. The palladium colloid catalyst solution is sufficiently applied by spray coating on the silicone rubber sheet prepared in the pretreatment step, and then the temperature is set to 100 ° C. in a high temperature oven capable of setting the temperature.
Dry at 30 ° C. for 30 minutes. Electroless plating stage: Electroless nickel plating bath (product name: TMP Chemical Nickel: Okuno Pharmaceutical Co., Ltd .: standard formulation)
The plating was performed at a temperature of 10 ° C. for 10 minutes. Electroplating step: Bright nickel bath (product name # 6)
6: EBARA Eugerite Co., Ltd .: standard formulation) at a temperature of 30 ° C.
It is carried out for 30 minutes under the condition of a current intensity of 2 A / dm ² ,
An m-thick nickel metal plating layer was formed.

In order to evaluate the adhesion of the metal plating layer obtained through each of the above steps, the sheet-like material provided with the metal plating layer was fixed to an iron plate with a moisture-curing adhesive Super X, and the test piece was used. It was prepared and the adhesion was evaluated according to the “tape test method” in the “plating adhesion test” specified in JIS H8504. Specifically, a square streak having a side of 2 mm was completely formed with a cutter to completely penetrate the metal plating layer, and a cellophane tape having a width of 12 mm was pressed for 10 seconds to be adhered. Next, the cellophane tape was instantaneously peeled off under conditions perpendicular to the metal plating layer surface, and the peeled state was confirmed. No peeling was observed in the metal plating layer according to this example. After a dipping treatment in hot water at 60 ° C. for 4 hours, a similar peeling test was performed, but no peeling occurred, and it was confirmed that a strong metal plating layer was formed.

[0029]

As described above, according to the method for plating metal on an electrically nonconductive material according to the present invention, it has been difficult or impossible to form a metal plated layer. In contrast, it became possible to easily apply metal plating having high uniformity and adhesion. For example, a conductive roller having a high nip and a high conductivity, which is indispensable for a laser printer, a copy, and the like, can be suitably produced with the addition of conductivity to a rubber member by metal plating.
In addition, the present invention has a beneficial effect that metal plating can be similarly applied to a wide variety of substances including other substances having difficulty in forming a metal plating layer. Furthermore, the use of toxic and environmentally hazardous substances such as chromium can be avoided, so that there is no post-treatment problem associated with the disposal of pollutants.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a metal plating method according to an embodiment of the present invention step by step.

FIG. 2 is a process diagram showing each stage of a pretreatment process in a metal plating method according to an embodiment of the present invention.

FIG. 3 is a process chart showing each stage of a pretreatment process in a metal plating method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base material 12 Primer layer 14 Catalyst metal layer 16 Metal plating layer 20 Moisture curable resin 22 Catalyst metal

Claims (6)

[Claims] A moisture-curable resin (20) is applied to the surface of an electrically non-conductive substrate (10), and the moisture-curable resin (20) is dried and cured to form a primer layer.
After forming (12), a catalytic metal (2
2) is contacted with the primer layer (12) to form a catalyst metal layer (14), and the catalyst metal layer (14) is subjected to electroless plating to form a required metal plating layer (16). A method for plating metal on an electrically nonconductive material, characterized in that: 2. The method according to claim 1, wherein a silicone resin is used as the moisture-curable resin (20). 3. The method according to claim 1, wherein a cyanoacrylate resin is used as the moisture-curable resin (20). 4. The method according to claim 1, wherein the moisture-curable resin (20) is applied by spray coating. 5. The method according to claim 1, wherein the moisture-curable resin (20) is applied by using a roll rotor. 6. The method according to claim 1, wherein electrolytic plating is performed subsequent to the electroless plating.