JPS6041702B2 - metal coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal film that has a good surface condition and a metallic luster by magnetron sputtering.

In recent years, vacuum plating methods such as vapor deposition, ion blating, and sputtering have come into widespread use as non-polluting plating methods.

In any of these methods, the surface temperature of the plated substrate increases, and particularly when the plated substrate is made of a material that is easily damaged by heat, such as plastic, there is a problem in that the substrate deteriorates. Among these methods, sputtering is a method in which glow discharge is performed in a low vacuum of inert gas, and the metal of the cathode (target) is knocked out by the impact of cations and adheres to the surface of the plated substrate. , the plated film can be maintained for a long time without changing the composition of the alloy, and it is also possible to plate high melting point materials.

However, this method is only applicable in limited fields because of its slow speed, high working pressure, and the above-mentioned drawbacks such as an increase in the surface temperature of the plated substrate. . In order to improve this point, a magnetron type sputtering device was developed in which a magnet is placed on the back surface of the target to apply a magnetic field perpendicular to the electric field in the discharge space. This device prevents the electrons generated during discharge from flowing into the plated substrate, which is placed facing towards the cathode (target), by bending the electrons generated by the discharge and performing a drift motion by the magnetic field. This suppresses the temperature rise of the plated substrate. In addition, this device uses long continuous orbits of magnetic field lines near the target surface, forming an electron cloud with a high density of 1゛, so it can ionize gas efficiently even at low pressures and plating even when high power is applied. Since the temperature rise of the substrate is suppressed, high-speed sputtering similar to vapor deposition is possible, and a good metal film can be formed on plated substrates that are easily damaged by heat, such as plastic.

On the other hand, this method using magnetron type sputtering has a high degree of vacuum and can obtain a high-quality plated metal film, but
The plated metal film itself tends to have large distortions due to collisions between particles during the deposition process, and the interaction with the plated substrate is also large, resulting in excellent adhesion.

This tendency does not pose a problem when the plated substrate has a coefficient of thermal expansion that is approximately the same as that of the sputtered material, but it becomes a problem especially when there is a large difference in the coefficient of thermal expansion. For example, when plastic uses glass as a plating substrate and then metal-plats it, the appearance of the plated metal film is good because soft metals such as tin and aluminum move with the thermal deformation of the substrate material, but chromium and In the case of relatively hard and brittle metals such as stainless steel, cracks and wrinkles occur in the metal coating, significantly deteriorating the appearance, as shown in FIG. This is because the plated metal film cannot follow the thermal deformation of the plated substrate, and the built-in distortion is released by creating fine net-like cracks. In particular, in recent years, it has become desirable in various fields to plate the surfaces of plastics with metal plating, such as chrome or stainless steel, which gives a solid appearance instead of aluminum plating, and this cracking phenomenon has become a big problem. It was becoming.

In view of this, the present invention aims to obtain a metal coating with excellent appearance and metallic luster by plating a plated substrate such as plastic with a metal having a significantly different coefficient of thermal expansion using magnetron sputtering. It is something to do.

That is, the present invention is characterized in that the metal film formed on a plated substrate by magnetron sputtering contains 150 to 500 ppm of carbon.

The present invention will be explained in detail below.

The method for producing a metal film in the present invention uses a target that becomes a cathode. Magnetron sputtering is performed by placing a magnet on the back surface of the target and sputtering while creating a magnetic field near the surface of the target. In this case, the inside of the device is kept in a low vacuum with an argon gas atmosphere containing hydrocarbon gas, and a voltage is applied between the target, which serves as the cathode, and the anode, to generate a glow discharge, and the bombardment of cations at this time causes a glow discharge. In this method, the metal of a target made of a sputtering material is knocked out and deposited on a plated substrate such as plastic or glass placed opposite the target to form a metal film. As the inert gas, for example, argon gas or the like is used, and as the hydrocarbon gas mixed in the inert gas, any one of acetylene, methane, ethane, butane, etc. may be used.

In this case, the cracking property of the metal film due to the partial pressure of hydrocarbon gas, that is, the occurrence of cracks and the metallic luster (specular reflectance)
The results of investigating the relationship between the two are shown in the graph of Figure 2. In this case, ABS resin was used as the plated substrate, and chromium was used as the metal to be plated. From this result, when the acetylene partial pressure is 4X 10-4T0rr or more, the metal film changes color from yellow to gray, and the specular reflectance decreases.

Moreover, when the acetylene partial pressure is 3×10 −4 T0rr or less, the specular reflectance improves and the metallic luster increases. On the other hand, when the acetylene partial pressure is less than 8 x 10-5 T0rr, cracks occur in the metal film, the diffuse reflection component increases accordingly, and the specular reflectance decreases. Therefore, by limiting the acetylene partial pressure to a range of 8 x 10-5 to 3 x 10-4 T0rr, a metal film with no cracks, excellent appearance and metallic luster can be obtained.

Analysis of the carbon content in the metal film formed in this way revealed that the carbon content changed as the acetylene partial pressure changed, and the metal film corresponded to the range of acetylene partial pressure. The carbon content inside is 150-500p
The range is pm. Therefore, according to the invention, carbon 150
Metal coatings containing ~500 ppm change in film quality due to reaction products with carbon, have weaker adhesion to plated substrates than films made of metal alone, and strain due to differences in thermal expansion coefficients cannot be sufficiently transmitted, resulting in distortion. Since stress does not increase, it is possible to prevent cracks and wrinkles from occurring even in the case of hard and brittle metals such as chrome and stainless steel.

In addition, by limiting the amount of carbon contained in the metal coating of the present invention to the above range, it also has excellent metallic luster,
A metal film with a heavy feel can be obtained. Furthermore, since the present invention is formed by magnetron sputtering, low-temperature, high-speed sputtering is possible, which is particularly effective when the plated substrate is made of plastic, which is susceptible to thermal damage. Examples of the present invention will be described below.

Example 1 A target was made of chromium as a sputtering material, and a magnet was provided on the back surface of the target to form a magnetic field parallel to the magnet on the surface of the target.

In addition, the acetylene partial pressure inside the device was set to 1 x 10-4T0rr, and argon gas was introduced into this to increase the sputtering pressure to 5 x
10-4T0rr'.

When magnetron sputtering was performed in this state at a DC voltage of 450 V and a current of 100 A, a crack-free chrome plating film with excellent metallic luster was formed on the surface of the ABS resin used as the plating substrate. The carbon content in this chromium plating film was analyzed and found to be 180 ppm. Example 2 In the above example, the acetylene partial pressure was set to 2 x 10-4T.
0rr, argon gas was introduced thereto, and magnetron sputtering was performed in the same manner as above to form a chrome plating film on the surface of the ABS resin.

This plating film has excellent metallic luster without cracking.
Further, the carbon content in this plating film was 230 ppm.

Comparative Example 1 In Example 1 above, the inside of the apparatus was made into an atmosphere containing only acetylene, and the pressure was set to 5×10 −4 T0rr.

Further, magnetron sputtering was performed at a DC voltage of 440 V and a current of 100 A. As a result, the chrome plating film formed on the surface of the ABS resin was colored yellowish gray and the specular reflectance was reduced. Comparative Example 2 In Comparative Example 1 above, the acetylene partial pressure in the device was changed to 2×
The sputtering pressure was set at 10-5T0rr, and argon gas was introduced into it to set the sputtering pressure to 5X10-4.

Further, sputtering was performed on the surface of the ABS resin at a DC voltage of 450 V and a current of 100 A. As a result, the formed chrome plating film had minute network cracks as shown in FIG. 1, and the carbon content in this plating film was 110 ppm.

Comparative Example 3 In Comparative Example 2 above, the acetylene partial pressure was changed to 4×
10-4T0rr1 sputtering pressure 5×10-4T0r
r, and ABS at DC voltage 450V and current 100A.
Sputtering was performed on the surface of the resin.

The chrome plating film formed in this way has a yellow color,
Its specular reflectance is low and the carbon content is 560ppm
It was hot.

As explained above, according to the metal film of the present invention, by including a reaction product with carbon in the plating film and regulating the carbon content within a predetermined range, the metal film can thermally expand with the plated substrate such as plastic. Even if the rates vary widely,
It has remarkable effects such as no cracking, excellent appearance, and excellent metallic luster.

[Brief explanation of the drawing]

Figure 1 is an enlarged schematic diagram (magnification: 50@) of network cracks that occur in a chrome-plated metal film. Figure 2 shows the cracking properties and specular reflectance of the metal film as a result of changes in acetylene partial pressure. It is a graph showing changes with the mouth.

Claims (1)

[Claims] 1. In a metal film formed on a plated substrate by magnetron sputtering, the metal film contains 150 to
A metal film characterized by containing 500 ppm of carbon. 2. The metal coating according to claim 1, wherein the metal coating is made of chromium.