Suppliers expect adoption of interior surface lighting to increase over next three to seven years

Interior surface lighting is where "light meets surface", and this is achieved by concealing lighting behind a layer of fabric within the surfaces of a vehicle's passenger compartment. According to IHS Markit research, vehicle buyers nowadays prefer vehicle exteriors with hidden or concealed light sources as a distinctive decorative appearance for their vehicles. Similarly, the use of concealed interior lighting may also prove to be a desirable decorative feature. This type of lighting has recently gained traction, driven by changing consumer preferences. IHS Markit expects this technology to grow faster in premium vehicles in Europe, in terms of the adoption rate.

What is surface lighting in a car?

Interior lighting is generally used for two purposes: one is to provide general area illumination, and the other is to feature lighting of specific objects, either for aesthetic or functional reasons. In surface lighting, the light source, such as a light-emitting diode (LED), is recessed into the interior structure of the vehicle and covered with a layer of fabric. The light source is invisible when it is not in use. However, the light from it shines through the fabric or the foam layer when illuminated. A light-transmitting member, such as a light bar, light panel, or light pipe, can be used to provide illumination over a specified area from one or more LED light sources. Such type of lighting arrangement can be mounted inside a vehicle in various locations, such as on vertically oriented pillars, door panels, seat backs, seat fronts, and console sides. Such lighting can be as narrow as a pinpoint or as broad as the entire headliner of the vehicle roof.

According to Scottish LED lighting technology company designLED, generally, two types of approaches can be used: the edge-lit approach and the direct-lit approach. In the conventional edge-lit approach, to reduce the number of LEDs used to illuminate a surface, light-guiding optics are used to spread the light over a large area, with a thin form factor. Usually, the light-guiding optics are injection-molded polymethyl methacrylate (PMMA) plates, with LED modules located at one or more edges of the light-guiding plate. Sometimes, woven optical fiber technology is used. In the direct-lit approach, which is suitable for dynamic-addressable "pixels" of backlighting of surface materials, more conventional matrix arrays of LEDs are used. One of the features of the direct-lit approach is that a small LED pitch (with a small distance between the devices) is needed owing to the thinness required. Therefore, a huge number of LEDs are needed in the solution to cover large areas.

Key suppliers

Dräxlmaier is helping automakers use light as an innovative kind of brand communication in the premium segment. In surface lighting, the company offers Paspol, which is a variant of ambient lighting. In the Paspol system, a fiber optic light is integrated into leather or vinyl surfaces. The company also offers MP Paspol, which is a combination of MP light and Paspol—a uniformly illuminated, flexible light guide that is encased in leather, the surface of which in turn is given a micro-perforated laser-treated pattern.

Continental currently focuses on integrating digital functions in decorative surfaces, such as light integration into surfaces. The latest example is its translucent Acella Hylite, which was launched in May 2019. This material enables special lighting effects that can be used, for example, for backlighting a vehicle door. "Varying light sources can be used to create customized color effects or to light up warning signals on surfaces not previously used. It will soon be possible, for instance, to integrate functions directly in the surfaces," Dr. Alexander Jockisch, head of business development and marketing for surface materials in Continental's Benecke-Hornschuch Surface Group business unit said at the time of unveiling the product in July 2017.

designLED offers a hybrid solution between the edge-lit approach and the direct-lit approach. The company offers a mechanically flexible, light-guide plate-type solution, but with LEDs distributed in a matrix array inside the light guide. This enables the dynamic-addressable capability delivered by the direct-lit system, with the thinness associated with the edge-lit system.

French startup EFI Lighting, a subsidiary of the EFI Automotive Group, is focused on addressing the challenges of integrating lighting into the vehicle's interior surface and develop flexible lighting for curved surfaces. The company's Lightex technology is a patented optical fiber weaving and surface treatment principle developed for light diffusion. EFI's light guides are flexible tubes containing a bundle of optical fibers specially designed to uniformly diffuse light over their full length.

Another German player, SCHOTT, offers linear fiber optic light guides that focus light in a specific direction, highlight textures, and instill a feeling of comfort. According to the company website, SCHOTT SideLight is a patented technology using glass fiber optics and can be used in the panoramic roof, center console, and door panels, among other areas. In combination with highly effective LEDs, homogeneous lighting effects can be created even if available space is limited. Another offering is SCHOTT MultiLight, which combines several functionalities in a single light guide harness using only one light source. It can be used in the instrument panel, door panel, center console, and glove box.

Market outlook

Interior surface lighting is expected to offer some interesting growth and value generation opportunities in the vehicle lighting systems market. Surface lighting will give more options for personalization of vehicles and thus provide growth opportunities for suppliers working in this field. In surface lighting, use of different materials can help create various effects, including matte, glossy, and chrome. Surface-mounted LEDs will allow designers to place lights where it was not possible earlier.

IHS Markit anticipates adoption of surface lighting in vehicles will gain significant traction around 2022-23, with most of this growth expected to be driven by the luxury vehicle segment. The Audi A4 and Q3, the Jaguar F‑PACE, and the Mercedes-Benz GLC Coupé are some of the luxury models that already feature this type of lighting technology. The European market is expected to drive the highest growth for surface lighting applications initially, followed by the US and mainland Chinese markets.

Dr. James Gourlay, chief technical officer (CTO) and technical director at designLED told IHS Markit in an interview that much of the company's focus in Europe is on "premium and luxury models" because consumers in this segment are more discerning and have more disposable income, prompting them to demand and purchase this upscale feature to acquire uniqueness or "bragging rights". Gourlay added, "Inevitably, this will cascade to higher-volume, lower-cost models in time as the designLED-patented technology allows for reduced LED count and most likely will be implemented in all but utility of budget models." "Ultimately though, we see adoption taking place already, scaling over the next 3-7 years and reaching maturity in 8-10 years," Gourlay added. According to Gourlay, designLED is "already seeing significant momentum in Asia as time to market is significantly shorter, and Asian, especially Chinese manufacturers, are proving faster at getting innovation into the market to meet emerging needs and desires from the consumer in the areas of personalization and customization".

Dräxlmaier believes increasing consumer preferences for value-added features in a vehicle that offer a balance of functionality and aesthetic appeal will fuel growth of the automotive interior surface lighting market. "The market for interior surface lighting is driven by factors such as high individualization and the demand for premium interiors," Thomas Wallner, head of Product and Innovation Marketing at Dräxlmaier Group, told IHS Markit in an interview.

There are certain challenges to integrating lighting into interior surfaces, including limited installation space and heat from the light source. The light source used should be a low-heat light source, such as LED or a flexible light pipe as it resolves any problems associated with heat from the light source. "As the requirements grow from lines of light to surface areas of light, the development of thin, integrated, and cost-effective solutions becomes more difficult. If further "light where you want it" or addressable dynamic areas are required, then this becomes more difficult," added Gourlay.

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