Growing OLED Market

LIMO now offers the Activation Line UV with sGauss for the short axis profile. With increasingly better beam shaping, the new solid-state lasers can replace the excimer lasers in many areas of display manufacturing. (Image source: LIMO)

The sGauss profile (brown) has steeper flanks and a broader intensity maximum than a normal Gaussian profile (blue). This allows the laser energy to be introduced into the display foil much more effectively, increasing productivity in the LLO process by 30%. The sensitive OLEDs are less stressed, the error rate (ash rate) decreases, and the lifespan of the OLED displays increases. (Image source: LIMO)

The sGauss beam profile has significantly steeper edges. UV lasers in OLED manufacturing can achieve up to 30% higher throughput. At the same time, quality and yield of the OLEDs increase.

With their brilliant colors, OLEDs have not only conquered smartphone displays. Smartwatches, tablets, laptops, and home theaters also benefit from this new technology. Further growth is expected, especially in foldable displays and new dashboard displays in the automotive industry.

Accordingly, the industrial production of OLED displays of all sizes is progressing. In addition to simple scaling of area and throughput, higher productivity is also necessary. A new technology for beam shaping of UV lasers addresses exactly this need.

sGauss beam profile for the LLO process

A key process in OLED manufacturing is the Laser Lift-Off (LLO) process. In this process, the various functional layers of an OLED display are applied onto a plastic layer, which in turn is applied to a glass substrate. Once the OLED layers are complete, the foil is detached from the glass substrate via sublimation using a UV laser (Laser Lift-Off).

Solid-state lasers are now also available for this process. With comparable power, they are superior to the previously common excimer lasers, especially in terms of ongoing costs. Solid-state lasers deliver excellent beam quality, usually in a gauss-shaped beam profile. Several such laser sources are shaped into the required profile for LLO, up to 1,000 mm in length and less than 50 µm in width, using special micro-optics. The LIMOs Activation Line UV line beam shaping system, for example, which was awarded the renowned Prism Award in 2018, has been successfully used for years in the lift-off area of OLED manufacturing for flexible mobile displays.

The LIMO development team has now expanded the optical design of the beam shaping so that the gauss profiles form a line up to 1,000 mm long and 30 µm wide. New features include much steeper edges in the profile and a broader intensity maximum. This allows laser energy to be used much more effectively for detaching the display foil, increasing productivity in the LLO process by more than 30%. Additionally, the sensitive OLEDs are thermally less stressed (lower "ash value"), yield is increased, and the lifespan of the OLED displays is extended.

More productivity or longer laser service life

The new micro-optic for the sGauss profile is modular and can be continuously adjusted in line length and width. Existing systems can be retrofitted with an sGauss module. This allows either direct productivity gains or, with lower laser energy, significantly longer service lives with the same systems.

Besides efficiency gains, this new technology will open up additional applications, such as annealing and crystallization, for UV solid-state lasers. The optics thus become an essential part of the value creation of the UV laser system. With increasingly better beam shaping, the new systems can gradually replace excimer lasers in their domains.