What You Need to Know About...Spin Coatings

By The real cost of your spin coating includes many factors. Find out how lower priced coating may end up costing you more.
With lab owners and managers looking for ways to increase profits and reduce processing costs, many labs are looking to spin coating costs and performance. When researching a scratch resistant coating the following parameters are necessary to make the right decision for your business, fabricating process, and your customers’ needs.

Stability of a coating is crucial and the length of time a coating remains viscous in a coating system can be critical to success. Most coatings when new, will have a coating thickness of 4.5-6 microns, (50 microns is the average thickness of a strand of hair). With some coating brands, viscosity will double within 24 to 48 hours of being added to the coating machinery. As viscosity rises the coating becomes thicker and application to the lens becomes uneven.

Adhesion to the lens surface is also compromised resulting in loss of scratch resistance. Higher viscosities will also affect coating thickness from the lens center to lens edge leading to tint results that are uneven and blotchy. Coating stability helps ensure consistent lenses for anti-reflective coating applications which greatly reduce AR adhesion failure to a lens. Coating stability loss and high viscosities can also result in unexpected repairs and lab down time. Unstable coatings add unwanted stress to coating pumps and machine circuitry increasing the probability of machine failure, unexpected repair costs, and lab down time.

The ability of a coating to adhere to the many different lens substrates that a lab processes is a must. If a coating adheres to polycarbonate but not to a hi-index lens it certainly limits the types of lenses that can be processed effectively by the lab or will have an adverse effect when a doctor has returns due to coating failure.

The hardness of a backside scratch resistant spin coating now has a precedent set by ANSI Z80.1-2010, which states that to be “marketed” as a scratch resistant coating the lens must be harder than an uncoated CR-39 plastic lens. For the vast majority of coatings this is true. For everyday use coating that are common in the marketplace today the scratch resistance will range from a Bayer value of 1.5 to 2.0. Coating costs are definitely being looked at by lab manager/owners. Backside spin coating can be the highest breakage point in the lab. Typically, a lab can look to spend between twelve and sixteen cents per lens for backside coating. At this small margin of difference in per lens price all it takes is one breakage out of five hundred lenses to lose everything gained by using a lesser quality coating.

The following are important points to consider when looking at the price for a bottle of coating. How many lenses is the lab processing out of that bottle of coating? How often is the lab changing out the coating in the machine due to poor performance or thickening of the coating? What are the service levels of the company supplying the coating? Does the coating company offer technical support for the coatings and machinery? What are their hours of operations? Does the product ship the same day that the order is placed? Any amount of down time for the lab is time that sales aren’t being generated. Please make an effort to question your coating supply vendor to verify if the needs of your business are being met. The end result should be maximizing lab production and growing your business dollar. Your true coating cost has many factors outside of the price of the coating itself, you need to constantly be striving for improved process control which often depends on the product quality and support of your selected vendors.

For more information on Backside Scratch Resistant Coatings, watch for information coming from Ultra Optics, or contact us directly at 1-800-365-9993, info@ultraoptics.com , or visit www.ultraoptics.com.

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May/June LabTalk 2017