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In addition to their existing low-temperature
polycrystalline silicon (LTPS) TFT LCD
products, Sony Mobile Display Corporation
(SMD) has now added amorphous silicon
(a-Si) TFT LCD and capacitive touch panel
products to their product line through the
partial business transfer from Epson Imaging
Devices Corporation (EID) on December
1, 2009. (See the Side View section in this
issue for a related article.)
Improved picture quality displays are
drawing increasing attention for use in mobile
products, which are becoming increasingly
multifunctional, and automotive products as
well. In this article, we introduce both the
a-Si TFT LCD "Vistarich" technology, which
is being developed to provide screens with
improved legibility and even richer color
reproduction, and touch panel technology
that will accelerate the adoption of touch
panels in even more products and contribute
to improved operability.
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Due to the increasing functionality of mobile
equipment and the diversification of display types used in automotive equipment, in
addition to requirements for higher difinition,
wider viewing angles, and wider color
gamuts in displays used in such equipment,
there are increasing calls for faster response
times, lighter weight, more compact designs,
and ultralow power consumption as display
device characteristics.
To respond to these needs, up to now
Sony has developed, at SMD, the LTPS
"VSPECIII"*1 technology for small-size,
high-difinition displays, and EID has
developed the "Vistarich" based on a-Si
technology for medium size high-resolution
displays. Thus Sony now has two wide
viewing angle technologies.
Like the LTPS "VSPECIII" technology, the
a-Si based "Vistarich" shows minimal color
changes as the viewing angle changes
and achieves rich, high-quality images.
Also, since there is minimal unevenness
in the response speed in the middle
region of the contrast scale, it can also
achieve superb picture quality for moving
images. Furthermore, energy savings in the
backlight system and even thinner forms
will be possible due to efforts to increase
the aperture ratio.
■Features of the "Vistarich"
Technology
1. High contrast and minimal color changes
even with a narrow viewing angle
In the conventional TN (twisted nematic)*2
narrow viewing angle displays, there is
an extremely large degradation in image
contrast as one moves one's viewing angle
away from directly perpendicular to the
screen. Also, from the standpoint of tonal
reproducibility, when one views these
displays from an angle, the brightness of
the middle tones increases and there is an
inversion of tonal levels.
In contrast, the "Vistarich" displays can
maintain a contrast of 100:1 even from
a viewpoint slanted at up to 80° in any
direction and can display the midtones
correctly. As a result, these displays can
achieve truly gorgeous images with color
variations held to a minimum.
2. Lower power consumption due to high
aperture ratio and transmittance
Progress is being made in improvements
to "Vistarich" in areas such as pixel rules
and the LCD horizontal orientation, and
these devices achieve a high aperture
ratio and transmittance. This reduces the
power required by the backlight, which is
responsible for most of an LCD module's
power consumption, and contributes to
energy savings.
3. Minimal variations in response speed
at each tonal level
Compared to earlier products, "Vistarich"
displays have minimal variations in
response speeds not only in room
temperature environments, but in low-temperature
environments as well. This
can minimize residual images from motion
display. Thus these are optimal displays for
mobile equipment in which video playback
functions, such as One-Seg and DVD, have
become standard, and for car navigation
equipment.
*1 "VSPECIII" is a trademark of Sony Corporation.
*2 In TN displays, the liquid crystal molecules,
which are sandwiched between two layers
of glass, are oriented so that they twist 90°
and those liquid crystal molecules pass light
when they stand vertically. This is the most
common LCD structure.
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Sony Corporation Global Headquarters
"Vistarich" Wide Viewing Angle
Technology for 180° Left/Right
and Up/Down Viewing
Deployment of Monochrome "Vistarich"
Vol.61