SID 2010 – Seattle
High Efficiency Hybrid LED Backlight
for Large-area LCD TV
Presenter: Dr James Gourlay, CTO, Design LED Products Ltd
Co-author: Ian Miller, Program Manager, Scottish Enterprise
Contributor Profiles
Design LED Products Ltd
– A Technology Company based in Scotland
ITI Techmedia Ltd (part of Scottish Enterprise)
– A Research Institute based in Scotland
Design LED & ITI Techmedia developed the “Hybrid”
technology presented today
 The “Backlight Polymer Optics” R&D Program
40”
Large Area BLU Challenges
Technology suitable for LCD TV market that can be scaled to >40”
KEY SPECIFICATION PARAMETERS:
1.
Thin << 10mm
2.
Non-uniformity <15% large-scale, <1% small-scale
3.
Specific white point and uniformity
4.
Optically efficient >90%
5.
2-D Segmented to support future spatial/2-d dimming
6.
Low cost Bill Of Material
7.
Low cost manufacturing
8.
Low cost tooling (NRE etc.) for each design
9.
Supports a wide range of LED types and specifications
10. Enables a technology roadmap for future enhancements/cost reduction
11. Introduce colour RGB control for field sequential and colour dimming
Why is high Optical Efficiency needed?
Energy saving – regulation, consumer attractiveness
High optical efficiency = Reduced LED requirement
= reduced cost, reduced thermal management, better reliability
Design LED Light-Guide Technology
Patented device construction
“Composite Light-guide Structure” (UK - granted, other countries pending)
AIR
overall thickness
matches LED
Etendue
0.4mm – 1mm
AIR
substrate
matches
printing
0.05mm
-0.125mm
1. Thin transparent substrate – refractive index N1
2. Light-guide extraction feature on substrate
3. Thick transparent added light-guide – refractive index N2 (<= N1)
4.Light-guiding in composite layers and extraction from surface feature
5. Side-emitting LED embedded inside the light-guide structure
Definition of Hybrid BLU Technology
Not edge-lit
Not direct-lit
Not tiled
Hybrid
Edge-emitting/side-firing LEDs inside light-guide distributed in 2-d array
Hybrid Technology Description 1
•Developed specifically for large area LCD TV backlight
Main features
•A thin, bendable panel
•LEDs embedded inside light-guide – good coupling efficiency
•Short optical paths lengths – low light-guide loss
•Micro-prism extraction features – efficient light extraction from light-guide and controlled beam angle
SIDE ELEVATION VIEW
Top emitting light
and light-guided light
balanced at diffuser
to give uniform and
symmetrical beam
output
Light-guide
Construction
<2mm
No air gaps
Improved coupling
Integrated solution – excellent alignment of features
Microprism film is circuit substrate
LOW-COST PRINTING MANUFACTURE
Hybrid Technology Description 2
Narrow beam angle
LED
Concealment
Narrow Beam Angle
LED thickness
+>0.2mm
Substrate
SIDE ELEVATION
Good optical
coupling – LED
embedded within the
Light-guide material
2nd
Lightguide
Lightguide
Short average path
length
cm’s
LED
Heat sinking - low
thermal resistance
dielectric on metal .
LEDs distributed
across the entire
surface – not edge
LED
Reflector
Narrow beam angle of
light extracted from
Light-guide if required
Printed Micro-prisms
Printing Manufacture
Light
-guide
NO AIR GAP
Efficient Light
coupling to lightguide
+/-45o to +/-35o
FWHM,
(other values possible)
Efficient distribution
of light in light-guide
Good thermal
management
Efficient delivery of
light. Low glare.
Low-cost commodity
materials
Low cost established
manufacturing
processes
Main Technical Advantages – High Optical Efficiency AND low form factor (thinness),
supporting spatial/local dimming plus opportunities for curved lighting and R2R manufacture
Hybrid Technology Description 3
A DESIGN EXAMPLE
Standard design cell repeat to scaled to any BLU size
SMD LEDs
(white in this
example)
LED location
has an extraction
feature
inside light-guide
(not shown here)
LED positions
and pitch easily
changed
50mm
Modified
Microprism film
RGB LED
can be integrated
TOP ELEVATION PHOTOGRAPH
Short light-guide path
Thermal management distributed
across back of panel
First 40” White Hybrid BLU Demonstrator
40”
10
Successful integration into commercial 40” LCD TV for demonstration
Copyright ITI Techmedia 2009
White Hybrid Optimised Design
air gap construction 5.5 mm
SIDE
ELEVATION
2x PET diffusers (CCFL LCD TV)
Diffuser Board from CCFL LCD TV
Hybrid LED Light-guide
Heat sink
<1mm
150mm
No diffusers
Diffusers as above
Optical Efficiency Measurement 1
Eldim EZ160R
Luminance Area
Luminous
Intensity
Beam Angle
(FWHM)
Luminous
Flux
Power
consumption
Measured LED
Efficacy of Efficacy
Optical
BLU
(datasheet) Efficiency
4300 Cd/m2
0.45m2
1935 Cd
90o
3563 lm
72W
50 lm/W
62 lm/W
81%
ITI
600mm x
600mm
6600 cd/m2
0.36m2
2376 Cd
90o
4375 lm
73W
59 lm/W
62 lm/W
95%
DLED
150mm x
100mm
6000 Cd/m2
0.015m2
90 Cd
90o
166 lm
2.88W
57 lm/W
62 lm/W
91%
#2
600mm x
600mm
4400 Cd/m2
0.36m2
1584 Cd
90o
2915 lm
46W
63.4 lm/W
78 lm/W
81%
Sample
size
AU
BLU 40"
Optical Efficiency Measurement 2
XXX
Sample size
LED current
Measured
Efficacy of BLU
LED Efficacy
(datasheet)
Optical
Efficiency
150mm x
100mm
20mA
57.5 lm/W
62 lm/W
93%
Integrating sphere measurement – no diffusers, white PET reflector
40” White Hybrid BLU Demonstrator
Attribute
Display diagonal
Measurement
40”
Aspect Ratio
16:9
Light-guide/gap/diffuser stack
thickness
Light-guide Optical Efficiency
5.5mm
Luminance
7000 Cd/m2
Luminance non-uniformity
(No DBEF in system)
<15% no visible non-uniformity
Beam angle
+/- 45o
+90%
(no BEF)
1152 (60 Lm/W LEDs) measured
Number of LEDs
768 (90 Lm/W LEDs)
next design
Further reduction with DBEF
98W (60 lm/W LEDs) measured
BLU Power consumption
64W (90 lm/W LEDs)
Predicted
Further reduction with DBEF
White Hybrid Technology Roadmap
Based on 40” White LED BLU
Low performance LED
May 2010 Status
Low lumen/watt
High performance LED Next Generation
late 2010
2011
Units
High Lumen/watt
High lumen/watt
1152
550
462
60
90
100
Lm/W
1.6
2.4
2.7
Cd
o
o
o
+/-45 FWHM
+/-45 FWHM
+/-45 FWHM
Degrees
1
1.4
1.5
7000
7000
7000
Cd/m2
98
46
39
W
LED Type
LED Number in 40" Light-guide
LED Efficiency
LED Luminous Intensity at 20mA
Light-guide beam angle
DBEF Gain
BLU Luminance
BLU Power Consumption
Light-guide LED Cost Projected
DBEF Cost Projected
Light-guide Other Cost Projected
TOTAL Light-guide Cost Projected
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
US$
US$
US$
US$
performance
High
cost
Number of LEDs
Low
time
In general, the product needs high efficiency
and high colour performance LEDs
to meet market requirements.
White BLU Technology Comparisons
Technology
Optical efficiency
Description
Primary Loss contribution
60% to 90%
Top emitting LEDs in 50mm deep air cavity with strong
diffuser
Strong diffuser and cavity surfaces
Edge Lit LED
50% to 60%
Edge "mounted" LEDs with acrylic light-guide, white ink
dots
Design LED Hybrid LED
80% to+90%
Edge emitting LEDs embedded
in Hybrid
1cm's average light-guide path
in polymer
60%
Reflective
Surface absorption and lamp geometry
Direct Lit LED
Fluorescent Lamp
2.
1. LED to light-guide edge coupling,
10cm's average light-guide path in acrylic
3. White ink light extractor
Feature
Fluorescent
Tube
Direct-Lit
LED
Edge-lit
LED
Current DLED
Hybrid
Future
Design LED
Comparison
assumptions
Relative
Thickness
-
-
++
+
++
Thinner design
Relative
Weight
-
++
+
+
++
Assuming optimum heat sink fixture
Relative
Power Efficiency
-
+
-
++
+++
Efficiency of optics
assuming similar LEDs
Relative
Power saving
/Carbon footprint
-
+
-
++
+++
Based on efficiency
Life-time/thermal
management
-
++
+
++
++
Good thermal management
Curvable
-
-
+
+
++
Redesign
Relative System
Cost
++
-
-
+
++
<$10, plus LED cost in volume
BLUs Need High Optical Efficiency
High optical efficiency is a technical and commercial requirement
1.
Reduces LED number/specification
2.
Reduces Power Consumption
3.
Reduces thermal dissipation requirement
4.
Reduces cost
Hybrid RGB
Hybrid white LED
Tiled Light-guide LED
Edge-lit LED
(e.g. Samsung LED TV)
CCFL
LCD TV
System-level Energy Efficiency
(driven by optical efficiency and
spatial/colour dimming capability,
complicated by LED lm/W efficiency)
RGB Hybrid BLU Platform
To support colour spatial/3-d dimming and field sequential LCD
Summary
•
Novel integrated approach – “Hybrid” BLU Technology Platform
•
Key challenge is to achieve high optical efficiency while
retaining good uniformity with thin design
•
Status - 90% optical efficiency for a 40” BLU, with good non-uniformity
(small-scale) <10mm module thickness
•
Good luminance, beam profile and power consumption
•
Supports spatial/local 2-d dimming.
•
Supports a wide range of LED types and specifications
•
LOW COST SOLUTION – due to lower LED requirement, Bill of Material and
printing manufacturing process
•
We have demonstrators at the Author Interview session at 12noon.
Thin, energy efficient LED BLU, supporting spatial/local dimming