Transparent photochromic material with fast light and colour control

Short summary A Spanish SME specialist in nanoencapsulation has developed a photochromic technology for fast transmitted light control. The materials obtained through this technology autonomously respond to UV light changing their colour and light transmission (%T) within seconds. This response is desired for lenses, eyewear and transportation glazing that adapt to changing weather and for smart windows for energy saving. Partners interested in commercial or R&D with technical assistance agreements are sought

Full description The Spanish SME, founded in 2014, is run by a team that accumulates on average more than 10 years of experience on photochromic materials and micro-/ nanoencapsulation. Photochromic dyes can change their colour when exposed to light. Their practical applications to ophthalmic, sport eyewear, and smart windows has driven researchers in the continuous design and synthesis of novel photochromic dyes with optimized performances in polymeric matrices. However, whereas the colour change of these dyes can be fast in liquid solutions, they are hindered and slowed down upon integration into a solid matrix such as lenses. This is perceived as an inconvenience by the users, and can compromise visibility for automotive applications such as motorcycle face shields, preventing a deeper market penetration. To avoid this, the company has developed an efficient, straightforward and universal strategy to embed commercial photochromic dyes in a polymeric material, without compromising their optimum solution absorption and isomerization kinetics. Their solution is based on trapping emulsified nanodroplets of a dye solution into a liquid‐filled nanocapsule or directly into polymeric matrix (Figure 1). This technology is capable of producing liquid-core nanostructured materials with liquid-like photochromic response. By selecting the nature of the liquid core, solid stable materials are prepared with solution‐like colour‐changing rates that are at least tenfold faster than those measured for rigid polymer thin films and particles (Figure 2). The optical material comprising this nanocapsules is prepared through a straight forward process using commercially available materials, without further modification of the components. The films manifest true liquid-like kinetics and finely tunable photochromic behaviour, with a high transparency. The films are also recyclable, show enhanced fatigue resistance and its preparation is scalable. These traits make them highly suitable for lenses, sport eyewear and smart glass applications (Figure 3). The SME is interested in establishing a commercial agreement with industrial partners willing to industrialize the production of end-products based in this patented technology to bring it onto the market. Alternatively, the SME is also open to R&D with technical assistance agreements to develop customized photochromic solutions through this technology for eyewear, automotive and smart windows manufacturing companies.

Advantages and innovations The main advantages and innovations of the technology are: • Solid materials with the fastest fading response obtained from liquid photochromic solutions. • Highly transparent materials (90 %T) with low haze (< 0.5%) on the clear state. • Versatility proven with a variety of commercial dyes, granting colour tunability. • Capability of displaying high intense colourations in the dark state (< 5 %T). • The colour change is achieved within 10 to 30 seconds, depending upon the colour intensity desired. • Preparation process optimized to the use of commercially available bulk materials and industrially proven processes. • Applicable as coatings or as flexible films to be laminated in plastic or glass devices, both for flat and curved surfaces. • The materials are completely autonomous. This makes them ideal for light and passive products such as glasses, face shields and wearable items. No wirelines or power supplies are required.

Contact / source: NEXT EEN Widgets (europa.eu)