TECHSiL’s Guide to UV Technology: UV Curing Fundamentals from Wavelengths to Adhesives

Ultraviolet (UV) technology is increasingly being utilised across industries from Optoelectronics to Automotive and Medical. This guide answers some frequently asked questions regarding UV technology including UV cure adhesives and LED systems, where they’re used and why you should be using them in your manufacturing processes.

What is UV technology? 

Simply, UV curing technology is using light to cure a chemical substrate. 

UV curing adhesives, or light cure adhesives, are adhesives that cure when illuminated with light. Different adhesives will cure at different wavelengths, usually within the spectrum of UV-A or ‘blue light’, approximately 365 nm to 405 nm.

Where is UV Technology Used? 

• Lens bonding
• Glob tops for diodes and LEDs
• Automotive LiDAR systems, cameras, and headlights
• Production of refractive lenses and diffractive optical elements (DOEs)
• Securing fibre optic cables, fibre arrays and wave guides
• Medical devices and needle bonding

What UV Wavelength is Optimal for…

Short UV wavelengths (> 320 nm) typically contribute to drier, tack-free surfaces. Visible light energy in the range of 400-420 nm can increase the cure speed of adhesives possessing a combination of UV and visible light photoinitiators. Contact our Technical Team for more specific guidance for your application.

What Equipment is needed for UV curing?

Typically, a UV system includes Lamp, lamp housing, reflectors, cooling system, electronic control and regulation components. Other equipment needed includes:

• UV curing material i.e. adhesive
• Safety equipment i.e protective equipment and UV meter
• Automation/dispensing equipment for industrial purposes.

What Types of UV Cure Systems are available?

There are various types of UV curing systems available depending on your application and existing process. You can choose by light source such as full spectrum UV or LED systems, or by method, with handheld options, curing chambers, spot cure, and flood cure systems available. 

The main types of UV cure adhesives are acrylics, epoxies, and silicone. Cyanoacrylates, specialised formulas and dual curing ones are also available.

How Does UV Light Curing Work in Adhesives?

UV adhesive formulations contain a type of photoinitiator, when this absorbs light of a certain wavelength and intensity, it starts a reaction, curing the adhesive.

It is important to ensure the adhesive and substrate match the curing system. For example, if the substrate transmits visible light but not UV light, you cannot use a product that contains only a UV photoinitiator; a visible light photoinitiator must be present.

What are the Benefits of using UV Cure Technologies?

• Rapid cure
• Shorter cycle times
• Reduced manufacturing costs
• Relatively easy to manage
• Good moisture and chemical resistance
• Curing temperature sensitive components
• Non yellowing and transparent options

What are the Advantages of LED Cure Technology?

LED light sources possess a monochromatic spectrum and do not emit IR radiation. They are energy efficient and curing occurs at cooler temperatures than with conventional gas discharge lamps making them suited for temperature sensitive substrates.

LEDs do not require a warm-up phase and can be switched on and off without any problems. They also have a long operating life, with the typical service life being longer than 20,000 hours

What Materials Can UV Technology Be Used On?

UV adhesives tend to bond very well to glass, plastics, metals and ceramics.

Medical grade adhesives can be used to bond medical products usually made from a range of synthetic materials, including plastics that are hard to bond.

What is the Difference Between Mercury Arc Lamps and LED UV Systems?

UV light is produced when mercury vapor passes between an electric arc. Arc lamps typically provide between 500 and 2,000 hours of lamp life.

UV light emitting diodes (LEDs) are semiconductor components that produce light when electrical current flows through them. With a life expectancy of over 20,000 hours.

How Do You Prevent UV Shadowing in Complex geometries?

Dual curing adhesives utilise two curing methods to offer fast cure, maximum bond strength, while also being able to completely cure under components and in shadow areas where light cannot reach.

Do you need to prepare a surface before UV curing?

Substrates must be prepared before bonding to ensure maximum bond strength and durability. To prepare surfaces for UV curing:

• Clean and dry the surface before applying adhesive using acetone or isopropanol.
• When using metal substrates such as aluminium lightly abrade the surface first.
• Minimise exposure of the adhesive to ambient light before use

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UV Products to Consider: 

Hoenle are UV specialists, being one of the leading suppliers of industrial UV technologies worldwide. They develop, manufacture, and market UV and LED technologies to meet customer requirements, including adhesive systems, handheld UV equipment, curing chambers, LED-UV equipment, measuring devices, lamps, sensors, and more.

For more information regarding UV technology and UV cure adhesives contact our Technical Team.