what is 2.5D screen
glass?
the 2.5D glass trend sounds like
stereotypical marketing jargon… how can something exist between two and three
dimensional space anyway? However, the term is actually based on a real design
factor, it’s not just a name used to try and sell you semi-useless screen
protectors.
2.5D refers to a slight curvature at the
edge of the glass display, also known as a contoured edge. While not an
official name for any piece of technology, it is widely used to reference this
type of display design. You might not even really be able to notice it on some
handsets, but on devices where the glass sits atop the rest of the body, rather
than being secured behind a slightly raised bezel, you’ll certainly appreciate
the more seamless edge.
A lot of phones have
featured glass with some sort of curved edge over the years, but recently the
design has become a much more prominent marketing term as handsets have tried
to distinguish themselves based on aesthetic design. You can easily spot curved
glass on modern handsets such as the Google Nexus 6, Xiaomi Mi Note, and now
the Apple iPhone 6 too, just to name a few.
So, is it curved or not?
While not curved in the
most obvious sense, the name refers to rounding off the edges of a flat “2D”
display in the z-axis, adding a slight curve to what would usually be a
straight edge. If you can’t quite picture this, a press slide from the launch
of the Xiaomi Mi Note probably demonstrates the differences a little better
than I can put into words.
is effect can be made more or less
extreme, depending on how much of a curved edge is required. Even a small curve
can be used to make the edge of the glass feel smooth, while a larger curve may
look more stylish.
Going further and actually bending the
display leads to a more noticeable 3D effect. This is probably how we would
describe handsets like the G Flex 2 or Samsung’s Galaxy Note Edge and S6 Edge,
but these curved displays rely on bendable substrates and electronics too,
while 2.5D glass does not. That’s not to say that these type of displays don’t
feature curved glass edges as well, but it’s important to make the distinction
about the term, now that handsets feature more noticeably curved displays.
How is it made?
Although a lot of fuss has been made about
2.5D glass, there’s nothing particularly special about the way it is designed
and built. Because the actual electronic display components are not curved in
anyway, unlike a flexible display, 2.5D glass is manufactured in much the same
was as a straight glass panel, just with some additional shaping added when it
comes to forming the glass to the right size.
Fortunately, this means that 2.5D displays
can still benefit from hardening and strengthening manufacturing techniques,
such as those used by Corning’s popular Gorilla Glass. Individual smartphone
sized glass pieces are cut from the larger mother sheet, with an additional
processing layer thrown in to trim and smooth the edges of the glass. It’s a
little more expensive, but can produce more premium looking results.
The shaped glass can then be put through
the hardening process, by heating the sheet in a solution of molten salts at
very high temperatures and then cooling it rapidly to force the glass to
compress. Shaping and hardening is done in this order so that the structural
integrity of the stronger glass is not put at risk by attempting to reshape it
nearer the end of the processes.
For comparison, a fully curved display
like the G Flex 2 or Galaxy S6 Edge requires that the display’s transistor
backplane and circuit light elements, such as the OLEDs or LCD pixels, also
conform to the curve. Flexible electronic circuits like this are even more complex
and expensive to produce than the curved glass component.
What are the benefits?
The benefits of 2.5D glass are purely
ergonomic and aesthetic. It is especially important on touchscreen devices to
ensure that any surfaces that consumers are going to touch and swipe their
fingers across are smooth. You wouldn’t want to snag your finger on a sharp
glass corner!
You’ll still find 2.5D displays used in
products with a non-glass edge, simply because it helps keep the edge of the
glass away from the user’s fingers. Remember that intentional gap
between the Note 4’s body and its metal frame? It would have been a big deal if
sharp glass was exposed by the gap.
In curved glass edge
smartphones, 2.5D simply looks a little nicer than raising the bezel up above
the display edge and helps to ensure that the glass fits nicely against the
rest of the phone’s body.
As for toughness and scratch resistance,
it’s the underlying manufacturing technique that determines these properties
rather than anything inherent in the 2.5D name that specifies any such
properties.
You’ll find that a number of Gorilla Glass
handsets are also listed as 2.5D displays, but the two are separate terms.
There’s also no reason to assume that these are any tougher or weaker than
their regular flat glass counterparts. After all, it’s only the very edge of
the display which is any different. 2.5D displays manufactured with a different
process will result in different levels of toughness.
The only minor downside is that consumers
who like to place an additional screen protector on their smartphone might find
it difficult to find third party products that exactly fit the contours of the
2.5D glass. This is because the screen protector has to be manufactured to fit
around the curves of the display, which is a trickier and more expensive
process than producing a completely flat protector. You can find specific 2.5D
screen protectors for these devices.
Overall, the term 2.5D display is not
completely meaningless, but it’s not a major technical achievement that gives
one phone an advantage over another either. A 2.5D display may lend itself to
some nice looking designs, but it’s certainly not something to base your
purchasing decisions on.
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