Process of drilling organic glasses using a thermoplastic film protecting against cracking and crazing
The present invention is drawn to a process of drilling organic glasses, comprising the steps of: (a) providing a substrate of organic glass, preferably of optical grade, (b) laminating onto at least one surface of said organic glass substrate via an adhesive layer selected from the group consisting of pressure sensitive adhesives and hot melt adhesives, a thermoplastic polymer film having a thickness of at least 40 μm and an elastic modulus of at least 3 GPa, the peel strength of the thermoplastic polymer on the organic glass substrate being higher than 1.3 N/25 mm, preferably of at least 1.5N/25 mm, (c) drilling a hole through the substrate and polymer film by means of a drill, and (d) optionally removing the thermoplastic polymer film and adhesive.
1. A process of drilling organic glasses, comprising the following steps:
(a) providing a substrate of organic glass,
(b) laminating onto at least one surface of said organic glass substrate via an adhesive layer selected from the group consisting of pressure sensitive adhesives and hot melt adhesives, a thermoplastic polymer film having a thickness of at least 40 μm and an elastic modulus of at least 3 GPa, the peel strength of the thermoplastic polymer on the organic glass substrate being higher than 1.3 N/25 mm, and
(c) drilling a hole through the substrate and polymer film by means of a drill.
2. The process as claimed in claim 1 , further comprising a step (d) of removing the thermoplastic polymer film and adhesive from the substrate.
3. The process as claimed in claim 1 , wherein the polymer of the thermoplastic polymer film is selected from the group consisting of triacetate cellulose, poly(ethylene terephthalate), polyamide, polystyrene, poly(methyl methacrylate), polycarbonate and cyclic olefin copolymers.
4. The process as claimed in claim 1 , wherein the thermoplastic polymer film having an elastic modulus of at least 3 GPa is a transparent film having a transmission of at least 90%.
5. The process as claimed in claim 1 , wherein the substrate of organic glass is an ophthalmic lens substrate.
6. The process as claimed in claim 1 , wherein the thickness of the thermoplastic polymer film is comprised between 50 μm and 1 mm.
7. The process as claimed in claim 1 , wherein the adhesive layer has a thickness comprised in the range of 1 to 50 μm.
8. The process as claimed in claim 1 , wherein a thermoplastic polymer film is laminated on both sides of the substrate.
9. A process as claimed in claim 1 wherein the organic glass is of optical grade.
10. A process as claimed in claim 1 wherein the peel strength of the thermoplastic polymer on the organic glass substrate is of at least 1.5N/25 mm.
11. The process as claimed in claim 1 , wherein the thickness of the thermoplastic polymer film is between 100 mm and 700 mm.
12. The process as claimed in claim 1 , wherein the adhesive layer has a thickness comprised in the range of 10 to 30 μm.