Effects of copper interfacial layer on surface characteristics, adhesion and wear durability of fluorocarbon thin film sputtered onto polyimide film substrate

• A PTFE thin film was deposited onto a polyimide film substrate by r.f. sputtering.
• Hydrophobicity was enhanced due to the coating.
• The sputtered PTFE thin film onto the polyimide film substrate had poor adhesion.
• Adhesion property was increased due to introduction of copper thin film.

Sputtering is one of effective technologies to enhance functions of polymer film surfaces, and polymer film coating by the sputtering is one of the surface modification technologies. Polyimide (PI) has good thermal and chemical stabilities, and excellent mechanical property, and high performance PI films can be achieved by controlling of nanostructured surfaces, e.g., hydrophobic PI film can be applied for precision instruments such as printer transfer belt. Polytetrafluoroethylene (PTFE) has also excellent thermal and chemical stabilities, lubricant and insulating properties and hydrophobicity, however, it is difficult to form the PTFE thin film on a polymer film substrate without peeling. Although PTFE thin film was deposited onto a PI film substrate by r.f. sputtering to enhance the hydrophobicity of the PI film substrate, there still remains a serious drawback in the adhesion between the sputtered PTFE thin film and the PI film substrate. A copper (Cu) thin film was introduced between the PTFE thin film and PI film substrate (PTFE/Cu/PI). Although the surface roughness and hydrophobicity of the PTFE/PI laminate decreased due to the introduction of the Cu thin film layer, the adhesion between the sputtered PTFE thin film and PI film substrate was improved without deterioration of wear durability.