In recent times, the demand for spectacle frames fitted with glass or poly-carbonate Rx lens has increased significantly, which may be connected to the rise in usage of spectacles for various reasons such as increased screen time on computers, tablets, smart phones etc. The article in Times of India dated 17/6/21 is ample proof of the same. The lenses that are used in spectacle frames must undergo a rigorous process right from cutting, polishing, grinding etc., before they are fitted in the spectacle frames. The process requires an adhesive tape to be applied to the concave/convex side of the lens before it is processed to spectacle lens, and the tape becomes an integral accessory during the process. The Adhesive Specialities R&D Team has recently achieved success in manufacturing the adhesive tape that is applied to the glass or poly-carbonate lens before the start of its transformation process.
The transformation procedure from glass/poly-carbonate lens to optical Rx lens requires continuous processing on the lens like cutting, polishing, grinding etc. During the process, the lens must be shielded from damages such as scratches or any particles settling over it. To enable protection amidst the process, a specialized adhesive tape known as Ophthalmic Lens Tape is applied for protection. The tape is one of the most recent inhouse developments by Adhesive Specialities.
Blocking, grinding and de-blocking process.
The Ophthalmic Lens Tape is a single-sided adhesive tape which acts as a protective layer on the convex/concave side of the lens before it is mounted on to the blocker/tooling machine. The tape allows for the polishing and grinding process to be carried out efficiently by preventing scratches/particles damaging the glass/poly-carbonate lens during the process. The tape is blue in colour, which makes it easy to distinguish during removal after the process
The lens undergoes various procedures before it becomes suitable for spectacle frames. In the very first step of the process, the Ophthalmic Lens Tape is applied on the convex/concave side of the lens and thereafter it is put in a holding tray. The lens processors, depending on the tooling machine, either uses liquid wax(non-alloy) or liquid alloy (alloy is made from 7 different metals heated at about 50ºC). The liquid wax or liquid metal solidifies in an attachment on the applied Ophthalmic Lens Tape and acts as a holding tool for the tooling machine during the processing of the lens.
The next step is a grinding process, this step gives the lens its corrective effect by “carving” the concave side with a diamond head followed by the polishing process.
The next step is deblocking, where the alloy or wax gently gets removed without the danger of lens breakage. At this stage, the tape has to be removed too.
Depending on the material used during the blocking process, Adhesive Specialities has developed two kinds of Ophthalmic Lens Tape, one is known as Ophthalmic Lens Tape for wax blocking and the other is known as Ophthalmic Lens Tape for Alloy blocking. The processors using wax as the preferred method of holding the lens, will have to use Ophthalmic Lens Tape – Wax, (the processors with high-speed imported machines, will generally use wax- based blocking methods) whereas other processors would prefer using alloy- based blocking systems.
Ophthalmic Lens Protection Tape
Ophthalmic Lens Protection Tape is applied manually to the convex side of a lens, providing a protective film for the surface during the grinding process and peels cleanly without effort from the lens after de-blocking.
Fundamental characteristics of the tape:
- Allows even the highest index lenses to be taped easily and securely.
- Conformable for all types of lens styles and base curves: low edge lifting
- Superior adhesion to a variety of lens types
- Clean removal from all lens types
- Available in bespoke designs
- Low torque to ensure accurate edging
- Available on white liner
- Colour: Light blue
- Available in reel and sheet form.
