Jim Watts, Principal Engineer held a presentation on Plastic Logic's colour electrophoretic displays, which are manufactured in the company's volume factory.

1. Presenting a 10.7” flexible
colour electronic paper
display fabricated using a
qualified manufacturing
process.
James D. Watts (Jim Watts) - C.Eng, M.Phil, B.Eng (Hons) DIS, MIET
Presented at the International Symposium on Electronic Paper, October 31st 2012.

2. Content
 Plastic Logic introduction
• Plastic electronics technology
• Development of flexible backplanes
• Qualified production process
 Colour display technology
• OTFT device architecture
• Spatially separated colour filter array
• Review the colour performance
• Considerations associated with EP colour
 Summary
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3. Introducing Plastic Logic
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4. Plastic Electronics Technology
Uses plastic instead of traditional silicon semiconductors
and glass
Enables a revolutionary design and form-factor
Shatterproof, Thin, Large and Light Display
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5. Company History
Display Development
10+ transistors 100+ transistors 1.2 M transistors Colour EPD 2.8 M transistors
Research, Process Development & Manufacturing
2000: Cambridge Technology 2008: Dresden Display Factory
Cambridge University Center translating research First plastic electronics factory in
Research in organic electronics into products the world
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6. R&D and Production Set-Up
Technology
Transfer
Cambridge R&D
Prototype Line (14”)
Cambridge R&D Prototype Line
 Ideal for proving new
concepts
 Highly configurable process
 New designs in < 1 month
 1” Chips to A4 displays
 R&D Engineers
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7. R&D and Production Set-Up
Technology
Transfer
Dresden Factory (Gen 3.5)
Dresden Gen. 3.5 Factory
 Backplane Manufacturing
 Qualified volume process
 Production equipment
 Fully Automated Handling
 Process, Equipment, Integration
Engineers
 Thousands of displays/week
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8. The Manufacturing Challenge
It is one thing to show a single display at a tradeshow…
...quite another to develop a high yield manufacturing process
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9. Plastic Logic’s Manufacturing Process
 Key differences in manufacturing organic and flexible
electronics:
− Utilize solution processing to fabricate OTFTs
− Process is designed to use lower temperatures which permits the
use of lower cost flexible substrates
− Exploit direct-write fabrication techniques to improve overlay
tolerances and feature registration
 Have developed unique process know-how and IP:
− Handling plastic sheets through assembly processes
− Large area deposition technologies of organic and inorganic
materials
− Cleaning and conditioning of the layers to improve device
performance
 Passed through the “Industrialisation” phase
− Reproducibility
− Homogeneity
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10. Processing challenges in the development phase
Optimising process conditions is a critical part of industrialisation process
Monitoring data from coating process in the first year (2009)
Thickness mean
Monitoring data from same process one year later
Thickness mean
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11. Display Testing and Reliability
 Flexible displays require special handling practises
 Test development for transistor and display parameters
− Definition of test specifications
− Electrical and Optical tests for production
− Test methods for OTFT and other characterisation structures
 Reliability optimization for quality and lifetime behaviour
− Accelerated test under different environmental conditions for lifetime projections
− Based on existing models for Si-based integrated circuits
− Parameters adapted to organic materials in terms of
temperature sensitivities and reaction to cycling
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12. Reliability tests
Name Test Purpose
Thermo cycling TST Mechanical robustness & CTE mismatch
High Temperature Storage HTS Storage of transport conditions
Advance Humidity Storage AHS Stability against moisture ingress
Low Temperature Storage LTS Storage of transport conditions
Real World Usage RWU Display use in non-accelerated mode
Advance Humidity Operation AHO Accelerated operation at high humidity
Low Temperature Operation LTO Accelerated operation at low temperature
Ambient Operation AO Accelerated operation at ambient conditions
Solar storage SOR Solar robustness
Altitude test ALT Pressure sensitivity
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13. Colour electrophoretic displays
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14. Colour EP Display Architecture
Colour Filter Array (CFA)
Encapsulation sheet layer
Plastic Substrate
E Ink Imaging Film
Electrophoretic
Frontplane (FP)
Plastic Logic Backplane Technology
Low Distortion Plastic
Plastic Substrate Logic Backplane
 Colour Filter patterned by multiple approaches (wet printing, sheet-to-sheet
alignment).
 During CFA pattern formation, the backplane pixel electrodes are not
visible (obscured by FP media layer).
 Backplane:
 1280 x 960 pixels (monochrome) == 640 x 480 Colour
 150PPI (monochrome) ==75PPI Colour
 Active Area: 217.6mm x 163.2mm (unchanged)
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15. Process for overlaying a colour filter
Black and White pixel array Coloured sub-pixel array Greyscale image showing overlay
Display
Colour pixel
G R
B W
170m
Schematic Plan view
Colour sub-pixel
OTFT cross-sectional
Frontplane media
view of single sub-
pixel
Pixel Electrode and Via
Pixel
Gate Capacitor Interlayer Dielectric
Gate Interconnect
Semiconductor
Gate Dielectric
Data line Drain Flexible Substrate
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16. Process for resetting distortion
Pixel
 Plastic Logic have Electrode
presented a process for
coping with the issue of
Interlayer
overlay distortion for multi- Via Dielectric
layered stacks made of
plastics
 The new process resets
distortion at the top pixel
electrode layer with no loss
in pixel performance.
 This means pre-patterned
layers can be placed on top
(eg Colour Filter)
Glass Backplane: All stack Plastic Backplane: Top Pixels
layers on a regular grid maintained on a regular grid
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17. Displaying colour – demand on single pixel driving
Displaying Red Displaying Green Displaying Blue
Displaying Cyan Displaying Yellow Displaying Magenta
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18. Colour plots - consistency
15
10
5
BATCH1
b* 0
BATCH2
BATCH3
-5
-10
-15
-15 -10 -5 0 5 10 15
a*
Data for 30 samples taken from three production batches
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19. Topic 1 - Image rendering
Topic introduction:
To display an image in colour on an electrophoretic display with a colour filter layer,
the image first needs to be processed to map to the layout of the colour filter.
Typically various parameters (i.e., saturation and brightness) are also adjusted
during this process to maximize the final colour viewing experience.
Before After
Examples of files before and after
colour conversion.
IMC application software.
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20. Topic 2 – Colour linearity
• GRBW configuration offers independent control of the
white sub-pixel
• What should we do with this?
Example 1: White sub-pixel follows minimum luminance of
the red, green and blue sub-pixels i.e., W=min{R,G,B}
Example 2: White sub-pixel follows minimum luminance
weighting of the red, green and blue sub-pixels using
{0.299Red, 0.587Green, 0.114Blue} i.e., W=lum{R,G,B}
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21. Topic 2 – Colour Linearity
(Diluted colour)
(Pure colour)
Pure colour Diluted colour
At 15th state
At 8th state
GR GR GR GR
BW .. red .. BW BW red .. BW …. driving red example when W=min{R,G,B}
GR
BW
1 .. .. 7 8 9 .. .. 15
GR
BW
GR
BW
GR
BW
GR
BW
GR
BW
GR
BW
GR
BW
The problem:
− The diagram above shows 15 transitions from dark to light for various colours. The first 7
transitions are to brighten the pure colour from black, the final 7 transitions are to brighten
the overall colour-pixel (by raising the brightness of the remaining colour sub-pixels).
− The four box diagrams placed above the chart are given as an example for the colour red.
In reality, the diagram above is more complicated as there are actually two sets of 0-15
transitions (because we can drive 16 grey levels for each)
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22. Topic 2: W=min{R,G,B}
W=min{R,G,B}
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23. Topic 2: W=lum{R,G,B}
W=lum{0.299R , 0.587G, 0.114B}
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24. Topic 3 – Drive waveform controlling blooming
Photograph revealing display effect of pixel blooming.
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25. Topic 3: Drive waveform controlling updates
• The waveform design for colour displays has a more
significant impact on the waveform update appearance
compared to monochrome displays.
• With colour there is now a risk that unwanted colours are
displayed during page turns, which can be distracting
and detrimental to the visual experience
• Minimising this effect whilst maintaining fast updates are
vital considerations when developing drive waveform
schemes.
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26. Topic 3: Drive waveform controlling updates
• Consider updating a colour pixel from white to red:
• A standard method for driving monochrome EPD, which
ensures all updating pixels finish at the same time, would
result in the sub-pixel arrangement shown below during an
update
• In this example, during this transition it could be possible to
introduce an interim state which forces the colour pixel to
momentarily display cyan.
Colour sub pixel appearance during
the display update.
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27. Summary
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28. Qualified Flexible Displays: Now Available
Display size 10.7”
Backplane Grey Levels 16
Sub-pixel density 150ppi
Contrast Ratio 12:1
Colour gamut 2% NTSC
 Highly flexible
 Paper-like finish
 Excellent readability
 Bi-stable EP media supports long
battery life
 Colour ideal for office applications
like charts and graphs
1280 x 960 Flexible Colour Display
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29. Plastic Logic’s Displays
• Plastic Logic have presented a 10.7” flexible colour electronic paper
display fabricated using its qualified manufacturing process
• The colour display is lightweight, robust and highly flexible
• Plastic Logic is constantly searching for partners wishing to create new
markets and opportunities for our display technology.
• Please visit our YouTube channel to view our latest technology
demonstrations:
− www.youtube.com/user/plasticlogic
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30. THANK YOU
Plastic Logic Ltd
34, Cambridge Science Park
Cambridge, CB4 0FX
UK
Tel.: +44 (0) 1223 706034
Email: jim.watts@plasticlogic.com
www.plasticlogic.com
This presentation is for the general purpose of supplying information. PLL shall be in no manner liable for loss arising from any party's reliance on
the contents of this presentation. Any party requiring specific advice or guidance should contact PLL separately on that specific matter.
You may need to own or be licensed to use complimentary technologies in order to use our flexible display technology in this application. It is your
responsibility to ensure that you secure such rights, if necessary.
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