Hard Coat Bubble

[samwkn]

I am new in this field, recently i facing some hard coat problem, We are coating 1.5, and 1.56 lens. Can any one suggest me?
1) what is the best thickness for hard coat?
2) Is it better that i chamfer at the edge before hard coating to prevent bubble?
3) i did the precleaning before ultrasonic cleaning, but i still found some small dot stick at the surface of the lens, any suggest to remove all this small dot?
4) this is my hard coat process --> a) precleanig with aceton, b) ultrasonic machine with tank1 5% NAOH and tank3 3% NAOH, c) oven 30minute d) cooling down around 15minute in flow box, e) hard coating.
Please suggest. Thank you.

[Chris Ryser]

So far you have not stated which kind of coating you apply..............thermocure or UV curable.............dipcoat or spinn coat.

[samwkn]

So far you have not stated which kind of coating you apply..............thermocure or UV curable.............dipcoat or spinn coat.

Mine one is thermocure, and is a dipcoat hard coating.

[samwkn]

My lab is a clean room grade 10K,

Mine ultrasonic cleaning is a 7tank design, which
tank1 is 5% NAOH with ultrasonic and temperature 55'C,
tank2 is DI water,
tank3 is 3% NAOH with ultrasonic temperature 55'C,
tank4 is DI water,
tank5 is DI Water with ultrasonic temperature 35'C,
tank6 is DI water with temperature 55'C
tank7 is Heater with tempeture 68'C

hard coat pre curing 68'C 4minute,
Oven Curing 90'C 3hours.

Thanks

[Chris Ryser]

Bubbles can occur by outgassing during curing, most probably some water contained in lens pores.

[samwkn]

Bubbles can occur by outgassing during curing, most probably some water contained in lens pores.

What u means is maybe the curing time after the ultrasonic is not enought?
I put the lens in the oven 90'C for 30minute. Normally how is the process?
Thank you.

[Chris Ryser]

That could be one reason. If any humidity is left in the surface it will make a bubble whe curing the hgardcoat.

[ego]

Hello Samwkn
does your coating machine pulling up the lens in hard coat or the tank of hard coat go down?
anyway you have to follow the instructions of the lacquer producer like the pulling up speed of the lens and Solid content % to get the right thickness of the coat
for the air pupal ,it comes from the laquer if it is not running in circulation for long time enough
hope this help as i `m also new to this process but i asked professional people about all these problems
Ego

[samwkn]

Thanks for your solution, What i found now the bubble is because of dust.
My lab is 10k clean room, after ultrasonic i will send the lens to the oven to cure, after oven i will send the lens to the flow box to cooling the lens.
What i suspect:
1)The process of sending those lens, the dust stick on the surface of the lens.
2)The dust stick on the lens when the lens is in the oven, The air inlet hole is no any filter for the oven. I think that the dust is coming from the air inlet hole.

[ego]

Most of these ovens soed not take air form outside,
you can dismount the oven from inside ,clean the heaters and I`m sure you will find a lot of rust on them ,clean them carefully not to brake them
and use a vacuum cleaner to remove the small dust inside
you cal also increase the time of pre curing in the machine ,it is the final step after coating the lens with lacquer
if you think that the dust comes from the way to the oven,put the lenses in a closed box to the way to the oven ,this will minimize the possibility of having dust on the way to oven
hope this help

[Chris Ryser]

Laboratory ovens are usually convection ovens that have and need an airflow to have even distribution of heat inside the oven chamber.

[Samuel Jong]

What's the pre curing/curing time and temperature in the oven after coating the lens with the lacquer?

[Chris Ryser]

That is all a question what product you are using, check your product instructions.

[Samuel Jong]

That is all a question what product you are using, check your product instructions.

We are using the lacquer from Sola and they named it SOJ-4.

[Chris Ryser]

Do not know about this one. However most thermocure temperature I know of is about 1 to 1 1/2 hours at 115C.

[ego]

Thickness has to be according to the technical data sheet ,you have to get it from your hard coat provider,you control thickness by controlling the pull up speed of the lens or the tank down velocity
according to the machine type
Also curing time has to be according th data sheet form provider .
pre-curing time is normally 7-10 min to check coating quality before final curing .

[Samuel Jong]

I do 80C for pre-curing and 110C for full-curing. And Pre-curing 15 minutes and full-curing 3 hours. Please advise.

[chip anderson]

No one is stirring up the coating material juice in the pot are they?

Chip

[ego]

Again ,it has to be done according to your hard coat provider ,for us we use SDC hard coat solution ,pre-curing is 10 min and curing is 3 hr at 120C

[Samuel Jong]

Again ,it has to be done according to your hard coat provider ,for us we use SDC hard coat solution ,pre-curing is 10 min and curing is 3 hr at 120C

Just got the info from the provider. Pre-curing is 10 min at 80C and curing is 3 hr at 115C. :cheers:

[IC-UC]

Best thickness - depends on manufacturer/type of dip coating and also the AR stack you are applying.
Dust - are you manually moving "wet" jobs around? Or is your unit enclosed and the robot does it all for you?
If the unit is enclosed, check the filtration units.
Curing time depends on resin as well as lens material. "softer" lenses need a longer time at a lesser heat like 1.6 at 100° for 3hrs, as opposed to 2hrs at 120° for CR39.

Also is the bubble a bubble or a particle? Bubbles could be becuase the unit may be sucking air. Particles could be due to the resin filter being blocked or the flow being restricted.

There are so many different areas you can look into, so please feel free to PM me or post more questions.