Optical Bonding Issues using UV agent

[cps13]

Hi,

I have a product which is essentially a handheld device with a small screen in, to be exact... a LS027B7DH01 Sharp 2.7” 400 x 240 Transflective LCD. This is then bonded to a clear plastic window using Novachem Optimax 6435 adhesive. The adhesive is cured using a UV light, a high power light but not an oven.

The problem I am having is that even using a clean room environment, removing all dirt/dust/grease and not handling the components by hand, I am still getting a lot of curing issues.

When the adhesive is laid down it appears fine, no air bubbles and a clear finish. However after/during curing little pockets appear under the plastic window, even right in the middle so i'm unsure how air could even enter and end up where it is.

Has anybody had experience with doing this who could offer suggestions as to why?

Cheers

 

[Harald Kapp]

The bubbles are likely to be the result of outgassing, a common problem when pouring epoxy. Gases (air) that are solved in the liquid adhesive and dissolve into bubbles during curing.
Common methods for reducing these bubbles are:

1. Careful handling of the adhesive (as little stirring as possible)
2. Curing the adhesive while in a partial vacuum (very low pressure) to allow the gasses to exit the adhesive before it cures
3. Curing the adhesive under high pressure to prevent the bubbles from forming