What is a Mi­croLED dis­play?

Ja­son Snell ex­plains why you should be ex­cited by it

iPad&iPhone user - - CONTENTS -

Re­cent ru­mours sug­gest that Ap­ple has been re­search­ing a new dis­play type known as Mi­croLED for sev­eral years, and is quite far along. We could start see­ing Ap­ple-pro­duced Mi­croLED dis­plays in Ap­ple Watch within the next two years, with phones and maybe even tablets.

Be cau­tiously op­ti­mistic about this new dis­play tech­nol­ogy. Mi­croLEDs have the po­ten­tial to be su­pe­rior to OLED in many ways, and could be the dom­i­nant dis­play tech­nol­ogy in new prod­ucts in a decade. Here’s why Mi­croLED is worth get­ting ex­cited about.

Thin­ner than OLED

One of the big ad­van­tages of OLED dis­plays over tra­di­tional LCDs is that they’re thin­ner, and Mi­croLED should be thin­ner still.

Tra­di­tional LCD screens, like those on ev­ery iPhone (ex­cept the iPhone X) and iPad, are com­prised of sev­eral lay­ers. The lit­tle red, green, and blue sub-pix­els don’t ac­tu­ally emit light. Rather, there are red, green, and blue fil­ters in front of a white back­light, with a liq­uid crys­tal layer be­tween them. Add in po­lar­iz­ers and glass sub­strates and you’ve got a rel­a­tively thick dis­play sand­wich.

OLED dis­plays use or­ganic com­pounds that emit red, green, or blue light when a cur­rent is passed through them. So, the lit­tle sub-pix­els emit their own light, and no back­light is needed. You also don’t need the liq­uid crys­tal layer, and only one po­lar­iz­ing layer. Hence, the dis­play is a lot thin­ner.

Mi­croLEDs are sim­i­lar to OLEDs, but they use a gal­lium nitride in­or­ganic ma­te­rial, sim­i­lar to what is found in tra­di­tional coloured LEDs. In fact, they’re a lot like reg­u­lar coloured LEDs, only shrunk way down. Be­cause the lit­tle sub-pix­els are emis­sive (they cre­ate their own light like OLEDs), they don’t need a back­light or liq­uid crys­tal layer. But they also don’t need a po­lar­izer at all, and only a thin glass layer on

top. They can be even thin­ner than OLED, and much thin­ner than reg­u­lar LCDs.

More ef­fi­cient

The su­per small LEDs in Mi­croLED dis­plays are more ef­fi­cient at turn­ing elec­tric­ity into pho­tons. Ba­si­cally, they pro­duce more ‘bright­ness per watt’ than ei­ther tra­di­tional LCD or OLED dis­plays. It’s still a new prod­uct that hasn’t been fully com­mer­cial­ized yet, but some

es­ti­mates say that Mi­croLED should use about half the en­ergy as OLED to pro­duce an equiv­a­lent bright­ness. Other es­ti­mates say the en­ergy sav­ings will be much greater. That’s good news for any de­vice, be­cause the dis­play is one of the big­gest bat­tery drain­ers to­day. But it’s es­pe­cially wel­come in tiny de­vices such as the Ap­ple Watch, where there’s no room for a big­ger bat­tery. With Mi­croLED, an Ap­ple watch could be slim­mer with­out sac­ri­fic­ing its all-day bat­tery life.

Higher res­o­lu­tion

LCDs and OLED dis­plays don’t dif­fer all that much in their max­i­mum res­o­lu­tion. The Sony Z5 Pre­mium crammed a full 4K res­o­lu­tion into a 5.5in dis­play – a stun­ning 806 pix­els per inch.

Though not in a prod­uct yet, Google and LG have de­vel­oped an OLED dis­play for VR that mea­sures 4.3 inches and boasts 18 megapix­els. That’s a whop­ping 1443 pix­els per inch.

There have been no com­mer­cial Mi­croLED prod­ucts re­leased, but the in­di­vid­ual red, green, and blue LEDs can be, well, mi­cro­scopic. We’re talk­ing about less than 100 mi­crons. It has the po­ten­tial for many times the res­o­lu­tion of ei­ther tra­di­tional LCD or OLED. We’re talk­ing ‘full 4K dis­play on an Ap­ple Watch’ res­o­lu­tion, or sev­eral thou­sand pix­els per inch. The first Mi­croLED dis­plays are al­most cer­tainly not go­ing to be that high-res­o­lu­tion, but the tech­nol­ogy is ca­pa­ble of that res­o­lu­tion and more.

You may have heard of OLED screens dis­play­ing ‘burn in’. Ba­si­cally, when the dis­play shows the same image in the same place for a very long time, it starts

to leave a ‘ghost’ of it­self so you al­ways see it there. It hap­pens on all sorts of screens; the LCD on your car dash­board may have faded in­ter­face el­e­ments that just don’t go away.

The LEDs in Mi­croLED dis­plays are far less sus­cep­ti­ble to this than the or­ganic com­pounds in OLEDs, or the liq­uid crys­tal layer in tra­di­tional LCDs. Burn-in shouldn’t be a concern for most Mi­croLED prod­ucts.

Su­per-fast switch­ing times, perfect for VR

One of the big ad­van­tages of OLED over LCD is the tech­nol­ogy’s very fast switch­ing times (the time it takes for each pixel to fully change colour). Slow switch­ing times can re­sult it blur­ring and smear­ing when ob­jects quickly across the dis­play.

The best LCDs can fully switch colours in a few mil­lisec­onds (thou­sands of a sec­ond). OLED dis­plays have switch­ing speeds mea­sured in mi­crosec­onds (mil­lionths of a sec­ond). That’s why they’re used in VR head­sets, feature high re­fresh rates and ‘pulse’ the pix­els one for just a brief frac­tion of each frame. LCDs just don’t switch fast enough for a good VR ex­pe­ri­ence.

Mi­croLEDs have switch­ing speeds that sound more like mi­crochips than dis­plays – they’re mea­sured in the nanosec­onds (bil­lionths of a sec­ond). The su­per high res­o­lu­tions in tiny sizes, com­bined with ul­tra­fast switch­ing speeds, make Mi­croLEDs perfect for VR and AR head­sets.

Su­pe­rior colour, con­trast, and bright­ness

Mi­croLEDs should be ca­pa­ble of pro­duc­ing brighter dis­plays with near-in­fi­nite con­trast ra­tios (be­cause black pix­els are en­tirely off), mak­ing them fan­tas­tic for HDR. The much higher max­i­mum bright­ness will make Mi­croLED dis­plays much eas­ier to read in di­rect sun­light, too. Mi­croLEDs are said to be ca­pa­ble of a broader range of colour, which means wider colour gamuts, and they can be more pre­cisely con­trolled for bet­ter colour ac­cu­racy.

The down­side: high cost

If there’s a down­side to Mi­croLED, it’s cost. The LEDs are man­u­fac­tured al­most like sil­i­con chips, and then trans­ferred onto a back­plane full of tiny gates to con­trol the elec­trodes that con­nect to the LEDs. It’s like trans­fer­ring parts of a com­puter chip onto an­other com­puter chip. This is done over and over again in

batches, and er­rors are pos­si­ble at ev­ery step. Un­til pro­duc­tion re­ally scales up, Mi­croLEDs are go­ing to be ex­pen­sive; some es­ti­mates say three to four times as ex­pen­sive as OLEDs. Even­tu­ally, if a lot of large-scale Mi­croLED fac­to­ries come on­line and the man­u­fac­tur­ing process be­comes more re­li­able, the cost should drop quite a lot, even­tu­ally reach­ing par­ity with OLEDs and po­ten­tially even as low as high-qual­ity LCDs.

When is Mi­croLED com­ing?

Ac­cord­ing to Bloomberg’s re­port, Ap­ple has been work­ing on this tech­nol­ogy in a se­cret lab since it

pur­chased Mi­croLED re­search firm LuxView back in 2014. For years, Ap­ple has been work­ing on a process to cre­ate consumer-grade Mi­croLEDs in a 62,000-square-foot man­u­fac­tur­ing fa­cil­ity. Ap­ple can ap­par­ently pro­duce all parts of the dis­play, in­clud­ing the back­planes, TFTs, and screen driv­ers.

The re­search fa­cil­ity, Bloomberg claims, can turn out “a hand­ful” of fully op­er­a­tional Mi­croLEDs at a time of the size needed for an Ap­ple Watch, though they are not ac­tu­ally in­te­grated into Ap­ple Watches.

It ap­pears that it is Ap­ple’s in­ten­tion to de­velop a process to ef­fi­ciently pro­duce consumer-ready Mi­croLEDs, start­ing in the Ap­ple Watch size, and then con­tract ac­tual pro­duc­tion out to a third party with much big­ger fa­cil­i­ties. The Bloomberg re­port makes it sound like an Ap­ple Watch with a Mi­croLED dis­play is prob­a­bly not com­ing this year, but may very well land in 2019 or 2020.

If the tech­nol­ogy were to ap­pear in an iPhone, it would likely be two or three years af­ter its Ap­ple Watch de­but.

VR dis­plays pulse on and off very rapidly for ‘low per­sis­tence’ to re­duce blur­ring. OLEDs are great for this, and Mi­croLEDs will be even bet­ter

A cross-sec­tion of LCD, OLED, and MicroLED dis­play lay­outs

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