Sdc varnish

[brandon76]

Has anyone had some experience with the hardcoat varnish from SDC? DOes it really turn yellowish as it ages? Is this a sign of it losing it's properties and thus in a phase of deterioration? Thanks in advance for your replies.

[Mauro.Airoldi]

I work with SDC hard coating from several years and never see this troubles, What coating are you using?
We test the coated lenses with QUV panel till 120 hours of UV ad at the end we don't see yellowish in the hard coating... some yellowish appeare in 1.6 and more in 1.67 lenses but it is lenses troubles, it is not comming from HC.

[brandon76]

Hi Mauro,

Glad to hear and greatly appreciate your reply. Just to make myself clear, my concern is not about our lenses turning yellowish after hardcoating them. In fact, we do not see any visual change in clarity between now and when the varnish was still very fresh. My concern is about our hardcoat lacquer turning yellowish around two months of usage. It was originally very clear.

As mentioned it is from SDC and its code is MP1179. This lacquer is already almost six months in our tank. We are just regenerating 25% every month apart from the daily varnish refilling that we do. Adhesion is still good so I'm not really sure if it is practical to change the full batch.

Since you have mentioned coating 1.6 and 1.67 lenses, I was wondering if you see any issues if we would coat such lenses with a primer before dipping them in the hardcoat tank? We find this to have better adhesion than relying on the surface activation from our caustic tanks. But I'm not sure if this can cause other problems because the technical data sheet of the primer we are using (PR1165) specifies this product only as a pre-coat for polycarbonate lenses. Thanks.

[Rafael]

I have no experience about MP1179, only with MP1154D. It turns, yellow-brown after some weeks. With combination PR1165+MP1154D ther were no adhesion or any other problems except more interfernce on 1.6&1.67, how it is with the MP1179 i don´t know but you have to precure the primer, and cool down the lenses befor dipping in MP1179.
Only Problem on PR1165 is then the primer is producing with contact to air some rubber like deposit in the tank, in the overflow tank.
Are you running many tint products?Have you noticed an increase of coating thicknes related to pot livetime on the MP1179, without compensating it with withdraw speed?

[brandon76]

Thanks Rafael for sharing your experience. I'm happy to know that we could use our primer for lenses other than polycarbonate. As I've said, during our tests adhesion seemed to be better for 1.6 and 1.67 with primer than without.

Regarding your question about whether our coating thickness increases as the varnish gets older, we are able to control this using the flow modifier from SDC. This means we do not need to compensate by increasing the withdrawal speed. We have very few tinting requirements. But our procedure is to tint before we hardcoat since the varnish we are using is a non-tintable one.

May I ask you how often do you change your MP1154D?

[Francois Chemoptic]

Hi Brandon,

I have worked with SDC in the past and I can tell you that I know that lacquer pretty well; everything you are describing I can testify. We made a new coating taht you may use as a straight replacement for 1154D. The only differences are: 1) QUVT is better due to exclusive sourcing of a key ingredient; 2) you don't need any flow modifier; 3) we can offer it 30% cheaper than SDC; 4) we can optimize your process based on the machine and the tap water you can get for rinsing.

[hardcoat engineer]

Hi, I am also using SDC Varnish.I use PDR199X2 FOR 1.5 INDEX.The varnish is initially very clear.But it darkens with time.We use tinted lenses too much and as we tint before hardcoating ,maybe the tinting looses it colour.We are using it for 4 months and the adhesion is good.we do not use primer.

[Francois Chemoptic]

Hi! the main issue is coming from the etching/rinsing process. This is something I'm pretty familiar with...I may fix this all if you just consider using our lacquer which is identiacl to the one you are currently using since the SDC patent is expired...