Cloudy Like Defect Appearance on Uncoat Substrate

[Mickey753]

Hi,

I am from lens manufacturing industry. Recently our production is encountering a cloudy like defect on lens edge.

We have evaluated different things to find root cause.

First assumption: Adhesive quality(being used for casting process) has deteriorated causing said cloudy defect
1.Proven to be not the issue, tested different tape types and still we are encountering the same issue

Second assumption: Catalyst quality slowing the reaction rate causing adhesive melting(which causes cloudy like defect)> one of the 4M Changes noticed
2. Change of Catalyst Lot: Still encountered high occurence of cloudy like defect

Third Assumption: Dry air being used isn't completely dry causing moisture contamination on mixed monomer solution
3. Installation of additional filter: lowered the said defect but still encountering

Fourth: Inner Releaser Issue
4. We have tried using another batch of similar inner releaser, it was proven to be effective lowered said defect to almost 50% but not said defect is rising again.

Do you have any idea of this particular defect mechanism? We have tried a lot of things but nothing seem to take effect to actually work. Hoping to get some sort of help from our experts.

Thank you!

[Chris Ryser]

Did you checked the molds around the edges, there might be some solvent leftovers.

[Mickey753]

Hi Chris,

Yes we did, tried every cycle washing for molds and comparing it with molds which did not undergo washing for 5 time polymerization process(also tried difference washing conditions-Still encountered said defect). Both case have similar appearance of cloudy like defect. We are using similar solvents with other monomer indices, but said defect is only encountered on one index type at an abnormally high occurrence rate.

As small scale testing, we have tried injecting different cleaning materials inside molds prior to monomer injection but it did not materialize to cloudy defect like appearance.

Right now our immediate countermeasure is raising our mixing chiller temperature, which seems to be effective in reducing said defect from 8.76% down to 2.86%. But we want to find main root cause and we still haven't up until now.

Thank you for your suggestion Chris. Would appreciate more inputs from you.

Regards.