A Guide to Understanding Optically Clear Adhesive Tape

Your phone screen just fell off (devastating, I know—how else are you supposed to check your Fantasy football lineup?). Now you’re left holding a fragile piece of glass, completely clueless about how to reattach it.

One thing’s for sure, office tape isn’t going to cut it. So, what kind of adhesive could hold everything together without blocking your view?

Engineers design optically clear adhesives specifically to function without being seen. As a flexible material converter, we’ve used a range of optically clear adhesive tapes for our customers’ electronic, medical, and industrial projects

Before you build your latest product, you’ll want to ensure it has the optical clarity it needs. The following article will teach you about optically clear adhesives, how they’re used, and how to find the most suitable one for your project.

What is an Optically Clear Adhesive?

An OCA tape, also known as an optically clear adhesive tape, is a specially designed transparent adhesive film that joins clear materials such as glass or plastic. This allows products such as monitors and testing equipment to remain usable. 

OCA TAPE APPLICATIONS 

The primary purpose of an OCA tape is to act as a transparent bond holding two substrates in place. Examples of this include:

• Screens
• Monitors
• Backlight assemblies
• Face mounting
• Testing kits 

OCA is responsible for bonding the internal components of electronics without obstructing interfaces. It also joins diagnostic and testing kit components (lab-on-a-chip blood and urine tests, etc.) for accessible viewing in microfluidics and medicine. Optically clear mounting adhesives are used to hang window details and backlights.

Which Tapes Are Optically Clear?

Most optically clear adhesive tapes are transfer tapes: thin adhesive film tapes with release liners. These tapes function well in OCA bonding applications because they lack a carrier, which essentially makes them a strip of clear double-sided adhesive.

Acrylic is the most common optically clear adhesive due to its resistance to long-term color degradation, such as yellowing. Occasionally, you might encounter a silicone optically clear adhesive for more sensitive applications, but most optically clear tapes are acrylic transfer tapes. 

The Levels of Optical Clear Adhesive

Different products require different levels of optical clarity. For example, the transparency needed for packing tape is likely far below the standard for any touchscreen protector.

• Class I: This is the highest optical clarity and aesthetic appeal standard (handheld device lenses, optical instrumentation, and displays).
• Class II: This designation is used where a highly aesthetic, quality product is desired (printed labels, decorative features, and permanent device applications).
• Class III: This title applies when aesthetic concerns are secondary to the product's functionality (packaging, protective masking, and parts that aren’t visible on the final product). 

The higher the optical clarity required, the more expensive your material will be. In addition, a clear view means stricter error standards, which will lead to a higher quality control cost. 

How to Find the Best Optically Clear Adhesive 

As the product developer, you’ll want the most suitable tape for your project. Part of that choice is considering price and manufacturability. Let’s review some common pitfalls of optically clear adhesive tape. 

1. SELECT THE RIGHT MATERIAL

Inventors are often surprised to discover that one of the biggest questions when choosing optically clear adhesive is: do you actually NEED it?

Multiple levels of optical clarity exist, and the vast majority of projects don’t require the Class I OCA we mentioned above. For this reason, when customers come to us with transparent designs, we often recommend near-optically clear materials. However, near-optically clear adhesives will degrade in color slightly over time, whereas optically clear adhesives resist discoloration entirely. 

Because the difference in usability is often slight, but the cost is far reduced, many businesses benefit financially from using near-optically clear tape rather than OCA.

2. FIND A PROPER MANUFACTURING ENVIRONMENT

Maintaining a proper manufacturing environment is crucial to working with optically clear adhesive tape. So, how do you know your manufacturer follows the guidelines to reach these standards?

Not every optically clear component needs to be built in a cleanroom. Once again, this comes down to near vs total optical clarity. However, for full-clarity components that might be affected by contaminants like dust, dirt, hair, or other particles, the rigorous filtering process of an ISO 7 standard cleanroom will keep them clean. 

Defining your product’s needs and seeking out the appropriate manufacturing environment is essential to finding the right converter. 

3. VERIFY THE QUALITY CONTROL PROCESS 

Building optically clear designs is essentially the same as working with transfer tapes, except there’s more importance placed on avoiding bubbles.

Air bubbles trapped during adhesive lamination can cause unwanted distortions in the final product, so quality inspections often focus on finding bubbles and other imperfections. 

Scratches, digs, or haze in an adhesive product are also considered defects, along with dust, dirt, hair, and other contaminants discovered during the quality control process.

When you order optically clear components, you’ll want to ensure you’re sourcing parts from trusted sources who manufacture pieces accurately to your specifications. 

In addition, have you considered whether you need to seal and ship OCA parts inside impermeable membranes? This will protect them from moisture damage and other costly mistakes. Sometimes OCA applications require special care and instructions for a successful product. 

Are you building an optically clear part design? Contact Strouse for a quote to continue your product development journey. Strouse will help you create accurate parts with high levels of manufacturability. 

If you have any questions about optically clear tape applications, please contact us or visit our OCA materials page.

Originally published: October 31, 2023