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![]() 產品與技術 > 電漿化學氣相沈積 Plasma-enhanced chemical vapour deposition (PECVD) is a technique wherein a plasma cloud is set up near the surface of a substrate such that pre-cursor gases are decomposed into chemically active molecules which then bombard and coat the substrate's surface. The nature of the resulting coating depends in part on the combination of pre-cursor gases. The technique is usually employed to deposit coatings onto hard substrates. For the XBHCOAT consortium, the challenge was to extend the application of PECVD to softer plastic materials such as the polycarbonate and CR39 (diethyleneglycol-bis-allylcarbonate) used in the production of ophthalmic spectacle and sunglass lenses. The aim was to improve scratch resistance, to reduce reflectivity and increase hydrophobicity. During the course of the project, its original leader, FACT Optique, was acquired by the Finnish company SCS Coatings - which had a particular interest in producing display covers for the GSM market. Consequently, polymethyl methacrylate (PMMA), a material widely used for this application, was added to the list of target polymers for coating.
There were several good reasons to look at the PECVD process. One was to find a replacement for current lacquering methods, which involve the use of environmentally objectional solvents. Another was to reduce manufacturing costs by increasing production speeds and improving reproducibility. Finally, it was expected that superior protection could double the lifetime of lenses, while multiple coatings would enhance their multifunctionality.
Progress towards an industrial technology for
coating sunglasses has been considerable, and the outlook for the
coating of display covers is equally promising. Italian research
partner played a major role in the project, having built a
prototype deposition machine, now installed at ASM, essentially
the main project deliverable. They were also instrumental in the
strategic reorganisation of the project as it changed directions
from an ophthalmic to a GSM application. Other industrial SME
participants , which will install a hybrid plating/PECVD plant for
coating sunglasses, to perfect a process for one-step antiscratch/antireflective
treatment. If this can be accomplished, it could well become
economically feasible to coat progressive ophthalmic lenses -
which have an intrinsically high added value, thus justifying the
cost of treatment in smaller batches.
Successful applications The prototype reactor is now working well, delivering homogeneous and reproducible coatings on substrates with surface areas of up to more than 1 m2. Its design is robust, and will readily accommodate extensions for automated loading and unloading.
ASM is now able to produce GSM display covers
at a rate of 20-30,000 per week, and expects to be able to move
towards a targeted 1 million per week within around one year. This
would open the door to an industry with a potential annual
turnover of At present, PMMA is the preferred material for display covers. Untreated, it is a little more transparent than polycarbonate. But coating the latter polymer also adds a degree of antireflectivity, which largely eliminates the difference - while wear resistance is a remarkable 2 000 times greater than that of uncoated PMMA.
Meanwhile, ASM has also identified another
interesting niche application in the coating of 1.2 metre-long
polycarbonate tubes that form the covers of inspection lights used
when servicing aero engines. These have been accepted by the
British Royal Air Force, and are now in small-scale production.
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