welcome to this part two about the
liquid crystal display very old but
still very relevant technology in the
previous video we ended with this
beautiful transparent dsm LCD dsm was
replaced after only two years with this
TM twisted nematic liquid crystal
display introduced in 1974 and still
widely used today it was easier to read
than DSM and the battery life was way
better this won't watch for example as a
claimed battery life of 10 years and now
14 years later it's still running on the
same battery
in fact it needs so little power it can
run on water
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even a small static charge activates
random segments
but my favorite example isn't this
little device all the way from my
childhood
it contains a message from January 1993
all this time is been using the same
battery to me that is amazing
all right here we go it had to happen
sometime explaining with the technology
at E and LCD uses polarizers so first we
have to understand polarized light light
consists of photons while more red
lights beat they shake which is the
light wave this wave can be at any angle
now of a polarizer has microscopic slits
waves not parallel with these slits
cannot pass the result is that all
passing light waves are parallel to each
other
that was take 26 and it still didn't go
right
perhaps I should stick to drawing so
polarized light is parallel light waves
if you add a second polarizer a rotated
90 degrees all light gets blocked and
this is where the pneumatic twisted
liquid crystal comes in pneumatic means
that all molecules and crystal are
aligned parallel like here
then we take a glass plate and add super
small scratches the molecules of the
crystal aligned to the scratches now we
take a similar glass plate but rotated
90 degrees just like the polarizer the
result the molecules and the crystal
twist and 90 degrees but only if the
distance between the two plates is
exactly right this is achieved by using
glass bits of an exact size mixed in the
crystal those are the dots you see here
the twisted molecules guide the light
waves and rotate them 90 degrees this
means that the light does now pass
through the second polarizer and now
liquid crystal magic when applying an
electric current the molecules untwist
meaning that the light does not pass
through the second polarizer so all
that's left is locally applying current
in any shape you want with transparent
conducting material like the DSM I
explained in part 1
glass plates polarizers a TN LCD 2 by
default is transparent but not
completely since the passing light is
polarized part of it gets lost and here
you see why so little transparent LCDs
are sold
instead most of them look gray that is
the result of the diffuse reflective
backplate that is added for optimal
brightness the loss of light due to
polarization makes it look gray but how
about a gold color
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hmm seems to work bit darker and how
about plain white that's working
surprisingly well it doesn't have the
viewing angle of the diffused silver
leaves the riddle why did I never use it
and while we're at it let's give it a
little twist white with blue stripes
just because we can hmm Luke's medical
maybe it needs a backlight so white is
working how about fluorescent pink still
very readable looks like red now so that
means I've never seen this and done or
maybe I have G shop these watches come
in a wide spectrum of colors where
sometimes the display indeed matches the
casing and you may have noticed that
various displays are inverted how does
that work
let's use this alt calculator to
demonstrate because I can remove the top
polarizer to invert I only have to
rotate it or flip it around the liquid
crystal behaves the same the
polarization still changes I decided to
fancy up my calculator with some color
filters there goes the polarizer and
here the colors ah that looks nice yet I
did something wrong I placed the color
filter in between the two polarizers the
result rainbow colors this is even more
fancy than I anticipated not too good
for the readability though to prevent
this I have to place the color filter in
front of the polarizer northern between
the two problem solved so why is this
happening let's do some research here is
a very modern LCD a monitor and this is
a polarizer that are placed in front of
the lens the light is blocked most
transparent materials like plastic break
up the polarization that results in this
beautiful colors let's rotate the
polarizer back please cart effects are
exactly what happened with the green
filter that I used this filter also has
an influence on the polarization so
could we use transparent film to change
the color of an LCD a piece of tape
perhaps
yo brother that looks promising Wow
it also inverts the display I just get
my calculator at the next level coolness
man but there is a third way to give an
LCD cover by using a bad quality
polarizer so to speak blue being the
most seen version the polarizer of this
or 90s watch in test mode has degraded
to a level that the digits are brown
rather than black and of course
backlight can also change the color
speaking of backlight when using color
filters in front of the backlight you
can simulate a full color screen while
it's really monochrome long story short
there are plenty of ways to give a
monochrome LCD color you could make it
green and red or partially orange
negative inverted bread filled blue
filter okay then just one more this is a
hybrid display I filmed years ago
switching the stereo set on reveals a
backlit LCD but when switching to tape
it changes to transparent and when you
switch it off it becomes a not really
reflective LCD
well I think that's enough for today in
the next video
color techniques that I do not yet
understand and remarkable multicolored
this place I hope to see you then
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