How do you overcome design limitations with optical materials?

Jon Lawson

The physical properties of materials can often limit design freedom. However, thanks to a specialised range of optical materials on offer from a UK-headquartered expert, this issue can be mitigated.

Optical materials are used in the manufacture of items such as mirrors, windows and prisms, and are designed to reflect, transmit, detect and transform light.

Included in Ellsworth Adhesives’ diverse range of optical materials are mouldable optics, optical coatings and optical encapsulants from Dowsil (formerly Dow Corning). Dowsil optical materials set out to go beyond the limits of traditional optical materials while not only offering excellent optical properties but also more resistance to impact damage and degradation from UV, heat and environmental extremes. These optical materials aim to push design boundaries by enabling LED sources to feature more complex shapes, micro-scale optical structures, multifunction parts and even undercuts that are difficult to achieve with organic polymers or glass.

Mouldable optics

Mouldable Optics can boost the long-term performance of a design beyond the capability of traditional optical materials. With unique optical properties, they are most resistant to impact damage and degradation from UV, heat and environmental extremes – a key benefit of modern optical materials compared to traditional means. Mouldable optics are also beneficial to the end user in the sense that it allows them to explore more complex designs whilst simplifying the manufacturing process.

Dowsil MS-1002 is a mouldable silicone optic designed to produce fine detail with good resistance to environmental aging. It has a medium viscosity for injection moulding, good mould flow and transparency with better heat resistance than plastic and appearing lighter than glass. There is also the option to easily mould this material into complex shapes.

MS-4002 is a unique material in the range, due to its ability to enable the moulding of complex finely detailed optical parts and secondary lenses. This mouldable silicone is a medium viscosity, fast heat curing optical moulding resin with good resistance to environmental ageing. Offering high heat transmittance and low light attenuation coefficient, it allows for better heat and UV resistance than optical grade plastics and is especially beneficial for injection moulding of secondary optics, lenses clusters, light pipes, light guides and free-form collimators.

Optical coating

Optical coatings are made up of a combination of thin film layers, designed to enhance transmission or reflection properties within an optical system. The performance of an optical coating is ultimately based upon the number of layers, which includes the thickness of the individual layers as well as the refractive index difference at the layer interfaces.

Dowsil CI-2001 white reflective optical coating provides even more freedom to go beyond the design limitations of traditional materials. This reflective coating can enhance light output and efficiency in reflectors, lightboxes, mixing chambers, backlight units and other surfaces, while ensuring high resistance to environmental ageing. CI-2001 offers many additional benefits, including additional protection from humidity, moisture and thermal stress, and excellent insulation against high voltages whilst minimising processing costs. At the same time, it eliminates the need for special storage, handling and ventilation.

Optical encapsulants

Optical encapsulants serve to enhance light output and efficiency in lighting applications. These silicone-based products have great compatibility with LED substrates while offering superior thermal stability. With a number of additional benefits – including their ability to sustain their physical and electrical properties over a wide range of temperature, humidity and other harsh environmental conditions – optical encapsulants are incredibly advantageous.

Dowsil JCR 6122 is a two-part, transparent, medium modulus LED encapsulant with very low viscosity and high transparency. It has been designed to meet the challenging needs of the LED market, with features including high adhesion, high purity, moisture resistance, thermal stability and optical transmittance.

EI-1184 is an optical encapsulant that can perform multiple functions. EI-1184 offers greater cost efficiency and a lower overall total cost of ownership while providing superior protection from moisture, thermal stress and shock and impact. Additional benefits include minimal yellowing and degradation while maintaining consistent light quality over the product lifespan.

Designed to meet the challenging needs of the optical market, Dowsil mouldable optics, optical coatings and optical encapsulants are a great choice to address tough industry demands and maintain a competitive edge.

Encompassing advanced silicone technology, users of these optic materials can enjoy a range of benefits including optimised efficiency, simplified and speed processing properties, resisted yellowing and physical degradation whilst protecting sensitive LED electronics from thermal cycling stress to perform reliably at extreme temperatures ranging from -45°C to 200°C.

Tom Harrison is with Ellsworth Adhesives.

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