LCVD coating continuous

Figure 35.14 depicts the effect of LCVD coating on the deposition of proteins on the contact lens surface in comparison with a commercially available reference lens [6]. The protein adsorptions were measured after continuous wearing, i.e., 1 week for the control and 1 month for LCVD-coated lens shown at left. The deposition on... 

The continuous operation of noncontinuous substrates, e.g., contact lenses, video disks, microsensors, etc., is performed by placing a certain number of substrate in an evacuation/transfer chamber, in which the evacuation is carried out and samples are transferred to the adjacent sample holding chamber in vacuum. The evacuated sample holders are placed on a conveyer one by one and pass through glow discharge zones. The coated substrates follow the reverse process at the downstream end of a reactor to be taken out in the ambient environment. Thus, the substrate charge is done in butch mode, but the LCVD process is done continuously. 

Considering the fact that the refractive index continues to increase after most of the polymerizable species are exhausted in the gas phase, DC LCVD of TMS in a closed system contains the aspect of LCVT of once-deposited plasma polymer coating by hydrogen luminous gas phase. In the later stage of closed-system LCVD, oligomeric moieties loosely attached to a three-dimensional network are converted to a more stable form, and significantly improved corrosion protection characteristics (compared to the counterpart in flow system polymerization of TMS) were found, details of which are presented in Part IV. Thus, the merit of closed-system cathodic polymerization is well established. 

This problem could be solved if one could crease the luminous gas inside the tube and keep feeding the monomer continuously to compensate for the consumption of monomer due to the deposition. If the luminous gas phase could be kept at a small volume within the tube (typically 2 cm of the quartz tube), and the tube could be moved with respect to the luminous gas phase, then the inside wall of a considerably long (e.g., 16 m) plastic tube could be coated uniformly by LCVD [4]. 

Contact lenses are coated with an approximately 20-nm-thick layer of a methane-based plasma polymer by a continuous mode operation, which is shown schematically in Figure 36.2. The total processing time for a contact lens is approximately 40 min, which includes drying wet contact lenses before plasma polymerization coating, evacuation, LCVD, and repressurizing for sample removal. The coating operation could be continuous for approximately 30 days between maintenance breaks. The reactor is capable of coating 30 million contact lenses a year (340 days of operation). 

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