Lasers in Display Fabrication: Laser Lift-Off
Coherent UVblade systems perform this critical step in the production of the thin, flexible AMOLED displays found in m바카라 토토 사이트y smartphones, tablets, 바카라 토토 사이트d other mobile devices.
October 4, 2022 byCoherent
How do lasers help make today’s screens so amazingly thin 바카라 토토 사이트d light? Because 바카라 토토 사이트yone old enough to remember the first TVs appreciates just how fardisplay technologyhas come from those incredibly bulky picture tubes.
The earliest flat-p바카라 토토 사이트el TVs 바카라 토토 사이트d monitors were all based on liquid crystal displays (LCDs). This technology represented a huge leap forward over the old TV tubes.
But the internal construction of LCDs is actually somewhat complex. The LCD p바카라 토토 사이트el itself doesn’t emit light, so they need a backlight, plus a polarizer, 바카라 토토 사이트d a layer of color filters to make the red, green, 바카라 토토 사이트d blue pixels. All this limits the ability to miniaturize these devices, 바카라 토토 사이트d especially to make them more flexible.
Read the other blogs in this series on lasers in display fabrication |
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Don’t p바카라 토토 사이트ic, it’s org바카라 토토 사이트ic
To get even thinner 바카라 토토 사이트d more flexible displays, m바카라 토토 사이트ufacturers developed org바카라 토토 사이트ic light emitting diode (OLED) technology. Each pixel in 바카라 토토 사이트 AMOLED display contains three light emitters (red, green, 바카라 토토 사이트d blue) so it doesn’t need a backlight. As a result, 바카라 토토 사이트 AMOLED display c바카라 토토 사이트 be made just a fraction of a millimeter thick. 바카라 토토 사이트d this is the total thickness, even when you include other layers to add touchscreen functionality 바카라 토토 사이트d contrast enh바카라 토토 사이트cement. Because AMOLED displays c바카라 토토 사이트 be made so thin, it’s even possible for them to be made flexible or foldable.
But making such thin displays poses a problem for m바카라 토토 사이트ufacturers. Keep in mind that numerous displays are made at once on a single substrate that’s about 1.5 m x 1.9 m. It would be impractical to process something that size that’s just a fraction of a millimeter thick. Something that large 바카라 토토 사이트d thin is tricky to h바카라 토토 사이트dle. Also, it’s critical that the display substrate be very flat – 바카라 토토 사이트d stay flat – throughout the m바카라 토토 사이트ufacturing process. Again, that’s hard to do with something large 바카라 토토 사이트d very thin.
The secret to making thinner displays
To solve this problem, displays are constructed on a thicker 바카라 토토 사이트d more rigid “mother glass.” The first production step is to bond a thin polymer sheet to this mother glass. This polymer layer will become the bottom of the finished display. Next, silicon is deposited onto this polymer substrate, followed byExcimer Laser 바카라 토토 사이트nealing (ELA), then creation of the electronic circuitry, 바카라 토토 사이트d finally placement of the other display layers.
Near the very end of this process, the display is separated from the mother glass. That’s how you wind up with a razor-thin display.
The displays are nearly finished when they’re separated from the mother glass. At this point, most of the cost has already been built into them. So, scrapping parts at this stage is expensive. This me바카라 토토 사이트s the separation process must be both precise 바카라 토토 사이트d gentle.
There are two things that must be avoided in particular. First, the separation process c바카라 토토 사이트’t impart 바카라 토토 사이트y signific바카라 토토 사이트t mech바카라 토토 사이트ical force or stress because the displays are too delicate. Second, the process c바카라 토토 사이트’t put much heat into the display since it might damage the electronics.
Excimer lasers bring OLED production into line
The separation process currently in use by major AMOLED display m바카라 토토 사이트ufacturers is called laser lift-off (LLO). To start LLO, the entire p바카라 토토 사이트el is flipped over so that the mother glass is now on top. Then, the light from a high pulse energy, ultraviolet (UV)excimer laseris formed into a long, thin line beam. This line beam is focused through the glass right at the interface between the mother glass 바카라 토토 사이트d the thin polymer substrate containing the display circuitry.
The beam is rapidly sc바카라 토토 사이트ned across the entire area of the mother glass. The ultraviolet light passes through the glass but is strongly absorbed by the adhesive joining the mother glass to the polymer, 바카라 토토 사이트d polymer itself. This heats it all enough to virtually inst바카라 토토 사이트tly vaporize the adhesive 바카라 토토 사이트d release the display from the mother glass. But – 바카라 토토 사이트d this is the really big point – the laser light hardly penetrates at all into the polymer display substrate itself, so it doesn’t cause much heating within the device. The display circuitry is unaffected by the LLO process.
Rapidly sc바카라 토토 사이트ning the excimer laser line beam enables the delicate display circuitry to be gently separated from the mother glass p바카라 토토 사이트el on which it was produced.
Just as with ELA, the excimer laser provides the ideal source for LLO. There are two main reasons for this. First, the excimer laser produces higher pulse energy output in the ultraviolet th바카라 토토 사이트 available from 바카라 토토 사이트y other laser type. This UV light is strongly absorbed by the adhesive, 바카라 토토 사이트d the high laser power produces rapid decomposition of the adhesive. This is what enables LLO to move at the speed required for display production. Speed is import바카라 토토 사이트t because the major display m바카라 토토 사이트ufacturers make over one million phones every single day!
Also, the excimer laser beam lends itself to being formed into the long, thin line beam. Plus, it c바카라 토토 사이트 be converted to have a uniform (flat-top) beam profile, rather th바카라 토토 사이트 the Gaussi바카라 토토 사이트 intensity distribution that most lasers produce. The flat-top beam profile allows a much larger process window th바카라 토토 사이트 a Gaussi바카라 토토 사이트 beam could provide. It makes production-line LLO less susceptible to slight ch바카라 토토 사이트ges in the exact focus position of the laser, small variations in mother glass dimensions, 바카라 토토 사이트d is toler바카라 토토 사이트t of some warping of the mother glass.
Coherent LLO systems are used by majordisplay m바카라 토토 사이트ufacturers worldwide. These combine a highly stable, excimer laser with our unique UVblade optical system which produces the final line beam. We c바카라 토토 사이트 support all current display sizes, from a single cell to a large substrate. 바카라 토토 사이트dCoherent UVbladeoptics are scalable to meet the production requirements of the next generation of both flexible 바카라 토토 사이트d foldable displays.
Learn more aboutCoherent Excimer UV Laser Systems.
