Editor's note: This new blog is from our regular contributor
David
Hsieh, who was recently named IHS Markit Technology
Fellow—one of only 11 titles awarded by the company in
recognition of our most respected and experienced
analysts.
At the recent MWC 2019, a conference dedicated to mobile
technologies, attendees had a chance to glimpse foldable displays
in a number of exhibits. According to analysis from the AMOLED & Flexible Display Intelligence Service,
the foldable display could well rejuvenate the display
industry—thanks to its revolutionary form factor and a superior
picture performance delivered by OLED technology. Even so, the
potential of foldables to revive the display space is likely to
bring about disruptive changes, especially to the market for smart
handheld devices.
Various types of foldable displays have been developed to date.
A list of these devices can be found in the IHS Markit report, Samsung and Huawei Foldable Displays - Special Report -
2019. Overall, several players—including the likes of
South Korean giants Samsung Display and LG Display, China's BOE and
Visionox, and Taiwan's AUO—are all working currently on their
own versions of the foldable display. Each brand has its own
concept and unique specifications to match, most notably in
thickness and bending radius—two key variables for improving
mobility in foldable displays.
Most current developments on the foldable display have chosen to
focus on a form factor combining that of a smartphone and a tablet
PC. Yet display makers are not in a hurry to launch foldable
displays for the end-market because of formidable production
challenges, says the IHS Markit Display Dynamics insight article,
Will foldable OLED displays arrive in 2018?
The reasons are many, as can be gleaned from the discussion
below.
Ultra-thin but robust display structure
To achieve the "foldable" feature for displays, the
display technology deployed must be flexible OLED. This is because
LCD—the traditional technology utilized for display panels in
general—cannot be applied to a foldable display's flexible
substrate.
Moreover, the material for the display substrate in foldables
must be polyimide—a film-like polymer with high heat
resistance—instead of glass, the conventional component in
non-foldable panels. And for smartphone applications, a foldable
touch panel and robust cover window are necessary.
On top of these requirements, the entire display
structure—consisting of the display and touch module—must
possess a thickness level measuring less than 1.0 mm and
accommodate a bending radius of 1.5 mm. Given the numerous
semiconductors, transistors, chemical layers, and optical film
layers that are placed on the top of the display substrate, each
layer must be extremely thin so that the total thickness comes out
to less than 1.0 mm. This, indeed, poses a major challenge to
display design capabilities, since consumers are not interested in
thick foldable displays.
Design and structure also matter. Foldable displays from Samsung
devices are thinner because Samsung uses a so-called "in-fold"
design. Meanwhile, an "out-fold" design makes foldable displays
thicker from Samsung competitor Royole—a company with sales and
marketing offices in North America and Europe, and has
manufacturing sites in China. Of the two, Samsung's "in-fold"
design is harder to manufacture. Analysis on this topic can be
found in two Display Dynamics articles,Foldable OLED display prototypes from BOE, LG Display, and
Samsung Display, and Royole announces foldable smartphone FlexPai with self-supplied
AMOLED.
New materials for foldable OLED and touch cover panels
Foldable displays also need to be reliable, requiring new
materials for the display as well as for the foldable touch panel.
These new materials are the colorless polyimide and hard coat for
covering and strengthening the cover window that protects the
display; the multi-buffer and cushion for improved flexibility; and
the specialized TFT in the backplane for greater reliability.
The figure below shows the characteristics of these new
materials.
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Manufacturing yield rate and reliability
Owing to the thin structure of foldable displays and the
complexities of a still-immature process, the current yield rate
for foldable displays is less than 30% on average—well below
that of standard smartphone OLED displays at 60-70%.
Among display manufacturers, the yield rate of Samsung Display
may be superior to that of its competitors given Samsung's
experience in the process and in equipment overall. Other display
makers, lacking Samsung's advantages, will have a difficult time
matching the South Korean giant's production yield.
For displays, reliability is indicated by the number of times
the screen can be folded and unfolded before it malfunctions. So
far, there is no consensus on what this number should be in
assessing durability because foldable devices have yet to be
mass-produced. Nonetheless, the general assumption is that foldable
displays should withstand more than 200,000 instances of folding
and unfolding, with the display and touch panel or cover window
still functioning following that level of usage. Anything less
makes for an undesirable foldable display.
To guarantee a reliability measure of 200,000 times is another
major challenge for foldable displays, as shown by analysis in the
IHS Markit report, AMOLED & Foldable/Rollable Display Technology Trend -
2019.
High costs overall
The cost of producing foldable displays is high, and the
elevated cost is a direct result of the abovementioned factors that
already make production challenging to begin with: the thinner
structure required for foldable displays, the new materials
involved, the complexity of the manufacturing process, the low
manufacturing yield, and the issue of reliability.
According to the
OLED Display Cost Model, a standard 7.3" QHD OLED display
costs $50—$35 for the display and $15 for the touch model. In
comparison, a foldable 7.3" WQHD OLED foldable display costs
$100—$70 for the display and $25 for the touch module $25. As
shown by these figures, the cost of the touch module for foldable
displays is considerably higher than that in a standard
non-foldable display.
As described in the Display Dynamics piece, Cost analysis for different foldable touch solutions,
the cost of foldable displays can be lofty with the use of special
materials. While no foldable displays have been mass-produced, two
options are considered viable as touch solutions for foldables.
These two—metal mesh and silver nanowire—will contribute to
the higher cost of foldables. To this end, Samsung Display has a
distinct advantage in that it does not require either of the two
materials as a touch solution. This is because Samsung uses its own
patented Y-OCTA touch solution, which dispenses with the additional
film substrate required by non-Y-OCTA solutions.
A customized supply chain
Unlike other smartphone displays, foldable displays must
be custom-made. Display makers can mass-produce, say, 5.8" or 6.0"
full-high-definition LCD or OLED displays, and then sell higher-end
products to top-tier smartphone brands while relegating comparably
lower-quality displays to second-tier or white-box brands for
emerging markets.
However, no second-tier brands or white-box markets exist at
present for foldable displays. The brands that will be launching
foldable displays are leading names in the industry, including
stalwarts like Samsung, LG, Huawei, Xiaomi, and Lenovo. The big
brands alone can do this because for foldable displays, development
costs are very high and market prospects remain unclear. There is
simply no precedent for such a device in the past, which makes it
difficult to gauge how the market will respond if a foldable
product is, in fact, launched.
Moreover, each brand has its own design and form factor, which
means that display makers can develop only one model at a time for
an individual brand. For investors, this singular approach in the
manufacturing of a specialty product increases the risk in losing
their Return on Development Investment or Return on Design-In
(RODI).
This is also one reason why Royole and Samsung are adopting
simultaneous roles as display maker and smartphone device-maker:
the two companies can exercise greater control in the budgetary and
manufacturing aspects alike of production, reducing their overall
financial exposure.
But for other display makers without the abundant resources
enjoyed by Royole and Samsung, the failure of a foldable display
product means the manufacturer will be unable to find other
customers to absorb the high development costs that had been
incurred throughout the project. Inventories of a failed foldable
display—already rejected by the market for whatever
reason—will also be challenging to offload, exacerbating the
financial woes of the maker.
One solution to potentially avert such a catastrophe is for a
partnership between two entities—the foldable device-maker on
the one hand, and the smart-handheld device-maker on the other, as
shown in the table below. However, it remains to be seen whether
such an unlikely "marriage" of rivals will work, and whether they
can combine differing visions to come up with a successful product
that is ultimately embraced by the market.
![]()
David Hsieh, a recipient of the distinguished
title of IHS Markit Technology Fellow, is Research & Analysis
Director at IHS Markit
Posted 20 March 2019