Relecura IP Intelligence Report
Blue LED Technology
Tracking it’s evolution
Relecura Inc.
www.relecura.com
[email protected]
November,
2014 2014
September
Highlights
• The Nobel Prize in physics for 2014 has been awarded to three eminent scientists- Isamu Akasaki, Hiroshi
Amano and Shuji Nakamura “for the invention of efficient blue light-emitting diodes which has enabled
bright and energy-saving white light sources”. - The Royal Swedish Academy of Sciences.
• Isamu Akasaki and Hiroshi Amano worked together at the Nagoya University primarily in developing high
quality GaN crystals and Shuji Nakamura was working on GaN based devices at the Nichia Corp during
the 90s.
• This report delves into understanding how information diffused among these inventors by mining and
exploiting information from the patent database.
• The patents pertaining to the key milestones in the LED history are analyzed to determine knowledge
transfer patterns.
• LEDs are highly energy efficient and are long lasting. They are constantly improved, getting more
efficient with higher luminous flux per unit electrical input power. The most recent record is just over
300 lm/W by CREE.
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Methodology
• Around 45 milestones in the field of LED technology are depicted using an interactive timeline.
• The report delves into the foundations of LED technology laid by eminent inventors of the first Infra-Red
(IR), Red, Yellow and Violet LEDs and analyzes if these technologies have had a direct impact on the Blue
LED invention or not.
• Analysis and conclusions are obtained by mining information from the patent database and mapping
knowledge spillovers using the patent citations network of the seminal patents.
• The technology focus and strengths of the seminal patents in Blue LED technology are understood by
using the ‘Relecura Technology Categories’ and the ‘Relecura Patent Quality’ metric.
• An analysis of the patent - US5578839 by Shuji Nakamura et al. and its citations was carried out to
understand the salient features of the invention and the various problems existing then, in the field of
GaN based hetero-structure devices.
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Key Findings
• No direct relationship between the seminal BLUE LED patents and each of IR LED patent, Red LED patent
and the yellow LED patent.
• Dense cloud of patents around the Shuji Nakamura’s patent followed by Isamu Akasaki and Maruska’s
patents indicating vast scope of use and great potential.
• A number of patents have directly built on the seminal Blue LED patents with a considerable number of
high strength patents that have stemmed from a combination of two or three of the seminal Blue LED
patents.
• Key application areas of the Blue LED invention include – Semiconductors, Optics, Lighting,
Photolithography, Medical Technologies among other areas.
• The use of the Blue LED technology in Drugs and Medical Chemistry gained prominence since 2003.
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Table of Contents
1. LED Technology
4. Blue LED Technology
• Quick Facts
• Why is the Blue LED technology so important ?
• Energy Efficiency
• Key excerpts from the seminal patent –
US5578839
• Dramatic cost reductions trends
• Citations analysis and summary of problems –
• Reduction of CO2 Emissions
US5578839
• Key considerations of LEDs and LED driver circuits
• Salient features of the invention – US5578839
• LED packaging and die design trends
• Properties of GaN based compounds
• Properties of Double Hetero-structure devices
2. LED Technology - Timeline
• Geo-Spatial patent citation network analysis of
US5578839
3. Patent Citation Analysis of Milestones
• Patent citation layout of seminal patents
• Patent graph layout with ‘Relecura Patent Quality’
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LED Technology
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LED Technology – Quick Facts
• Light Emitting Diodes (LED) are p-n junction diodes and emit light of
a particular wavelength when activated.
• LEDs are highly energy efficient and are long lasting. They are
constantly improved, getting more efficient with higher luminous
flux per unit electrical input power. The most recent record is just
over 300 lm/W by CREE.
• LEDs
are
ubiquitous
and
are
applied
in
household/industrial/automobile lighting, backlighting, medical
equipment and in a host of other applications.
Royal Swedish Academy of Sciences
• The LED lighting system market is expected to grow rapidly from
2015. In terms of revenue, the market is expected to reach $55
billion by 2020, from a mere $93 million (2012), with a high growth
rate of 92.4% CAGR (ResearchANDMarkets report, 2012).
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LED Technology – Macro level drivers
Macro level drivers in LED Lighting• Energy Efficiency
• Dramatic Cost reductions trend
• Reduction of CO2 emissions (Sustainable practices & Carbon crediting)
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LED Technology – Macro level drivers
1) Energy Efficiency:
The many levels at which Energy Efficiency in LED setups is being improved are• At an epitaxy level, one of the pivotal drivers is the furtherance of the critical production step- MOCVD (metal
organic chemical vapor deposition). Efficient production handling, better choice of layer material and substrate
material are the other driving points.
• At a chip level, multiple activities, such as the recent introduction of laser liftoff/flip-chip technology and
surface roughening, both of which minimizing light loss at the chip level.
• At a package level, initiatives are being taken to increase the amount of output light and to maintain
hermetical sealing. Various options include - changing the optical material, adding a remote phosphor light
source, using ultra-high reflectivity elements.
• At a module level, LED driver design will continuously be refined to improve wall plug efficiency, while
enhancing secondary optics can reduce light loss.
• Supporting tech (Monitoring and Lighting Control Systems)- advancements in low-power wireless
communications, and introduction of low-cost, multi-function smart sensors continue to minimize Total Cost of
Ownership of LED systems.
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LED Technology – Macro level drivers
2) Dramatic Cost Reductions Trend
• Material costs are falling. Sapphire substrate is one of the most expensive components of LED material costs today is
the sapphire substrate. Using silicon instead of sapphire can significantly reduce substrate costs.
(SiC, GaN, zinc oxide (ZnO) and silicon (Si) substrates are considered as the future LED substrates, thanks to low
lattice mismatches.)
• Downsizing the LED package.
• Shift from 2- to 4-inch wafers to 6- or 12-inch wafers can greatly improve the throughput of the MOCVD process.
• Chip on Board technologies are being explored that integrate the package and module step.
3) Reduction of CO2 emissions
• “The investment for substituting incandescent or CFL lighting with LED is a fifth of the investment for installing solar
power, calculated on a ton CO2 emission p.a. basis. Which means subsidizing LED is a more efficient investment than
subsidizing solar power from a government perspective.” – Lighting the way: Perspectives on the global lighting
market, McKinsey
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LED Technology – Design level drivers
Key considerations of LEDs/ LED driver circuit:
• Constant Current (CC) Drive requirement across a potentially wide voltage range
• Efficient SMPS (Switch Mode Power Supply) Design
• Dimmer Compatibility
• Reduction of Light Flicker
• Heat Sink design / Thermal path of LEDs (Thermal management)
• Optical Design
LED packaging and die design trends
• Chip-on-Board (COB) LEDs
• Phosphor coatings methods
• Deposited silicone primary lens systems
• New kinds of chips – (Soraa GaN on GaN , Verticle Hexagonal Chip – Verticle LED
design)
• Usage of high purity gases (NH3,N2,H2) in the MOCVD process
• High Voltage and AC LEDs
Weir, B.- High Brightness LED Driver Solutions for General Lighting World of Lighting, ON Semiconductor
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LED Technology - Timeline
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LED Technology Timeline
Click for an interactive timeline
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LED Technology Timeline
• From the timeline six milestones up to the invention of the Blue LED was considered for analyzing the technology trail and
identifying knowledge spillovers.
• The key events considered are:
Milestone
Publication
Number
Invention of the first IR- LED by Biard and US3293513
Pittman
Invention of the Red LED by Nick Holonyak
US3249473
Source
Filing Year
http://en.wikipedia.org/wiki/James_R._Biard
1962
http://en.wikipedia.org/wiki/Nick_Holonyak
1965
Invention of the Yellow LED by Craford Magnus US3873382
George
Work on Violet LED by Maruska et al. at RCA US3819974
labs
http://en.wikipedia.org/wiki/M._George_Craford
1972
http://www.oregonlive.com/siliconorest/index.ssf/2014/10/oregon_tech_ceo_says_nobel_pri.
html
http://www.sandia.gov/~jytsao/WCS.pdf
1973
http://www.sandia.gov/~jytsao/WCS.pdf
1993
Work on Blue LED by Isamu Akasaki, Hiroshi US5122845
Amano et al. at Nagoya University, Japan
Work on Blue LED by Shuji Nakamura at Nichia US5578839
Corp, Japan
1990
• For the above patents the citations was extracted from Relecura and the citation network is rendered for further analysis.
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Patent Citation Analysis of Milestones
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Patent Citation Analysis of Milestones
Key features of the graph• The nodes in the graph indicate patents.
• The edges indicate citation links between the patents.
• The size of a node indicates a specific parameter.
• The direction of knowledge flow can be understood by
following the edges in a clockwise direction.
• One level of forward and backward citations are
considered in the analysis.
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Patent Citation Analysis of Milestones
Milestone
Publication
Number
Invention of the first IR- LED by US3293513
Biard and Pitman
No. of Fwd.
Citations
117
Invention of the Red LED by Nick US3249473
Holonyak
Invention of the Yellow LED by US3873382
Craford Magnus George
17
Work on Violet LED by Maruska et US3819974
al. at RCA labs
199
Work on Blue LED by Isamu US5122845
Akasaki, Hiroshi Amano et al. at
Nagoya University, Japan
225
Work on Blue LED by Shuji US5578839
Nakamura at Nichia Corp, Japan
408
Yellow LED patent
[1972]
Violet LED patent by
Maruska
[1973]
7
Node size scaling
0
No. of Fwd. Citations
408
Blue LED patent by
Akasaki et al.
[1990]
The patent with the most number of forward citations is the one of Shuji Nakamura’s with 408
forward citations followed by Akasaki and Hiroshi’s patent with 225 forward citations.
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Red LED patent
[1965]
© Relecura Inc.
Blue LED patent by
Shuji Nakamura
[1993]
IR LED patent
[1962]
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Patent Citation Analysis of Milestones
• Number of patents which have a direct link to the seminal patents
Seminal patent of
Nakamura
Akasaki
Maruska
Nakamura & Akasaki
Akasaki & Maruska
Nakamura & Maruska
Nakamura, Akasaki & Maruska
No. of Patents
266
196
51
4
10
123
15
Yellow LED patent
[1972]
Red LED patent
[1965]
Violet LED patent by
Maruska
[1973]
• The numbers in the table illustrate the impact each seminal patent
has in the LED space.
• The IR LED, Red LED, Yellow LED inventions have a relatively lesser
impact in this tech area when compared to the Blue LED work.
This analysis also gives us an idea as to why the Blue LED inventors
were chosen for the Nobel Prize rather than the trailblazers in the
LED field.
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Blue LED patent by
Akasaki et al.
[1990]
Blue LED patent by
Shuji Nakamura
[1993]
IR LED patent
[1962]
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Patent Citation Analysis of Milestones
• The size of the node in this graph indicates its ‘Relecura Patent
Quality’ score.
Yellow LED patent
[1972]
Red LED patent
[1965]
Violet LED patent by
Maruska
[1973]
• The count of forward citations is a recognized metric for patent
quality but is a vague indicator of patent strength. ‘Relecura Patent
Quality’ is a proprietary metric related to patent valuation, quality
and monetization potential of each individual patent.
Node size scaling
0.5 Relecura Patent Quality 4.5
Blue LED patent by
Akasaki et al.
[1990]
Blue LED patent by
Shuji Nakamura
[1993]
IR LED patent
[1962]
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Patent Citation Analysis of Milestones
Milestone
Publication
Number
Relecura
Patent
Quality
Invention of the first IRLED by Biard and
Pitman
US3293513
1.5
Invention of the Red
LED by Nick Holonyak
US3249473
1
1.294
1
1
Invention of the Yellow
LED by Craford Magnus
George
US3873382
1
1.285
1.5
1
Work on Violet LED by
Maruska et al. at RCA
labs
US3819974
1
2.761
3
NA (No
backward
citations)
Work on Blue LED by
Isamu Akasaki, Hiroshi
Amano et al. at Nagoya
University, Japan
US5122845
2.5
2.431
2.5
1.533
Work on Blue LED by
Shuji Nakamura at
Nichia Corp, Japan
US5578839
4
2.717
2.5
1.2272
Highest Relecura
Patent Quality among
the seminal patents
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Average
Relecura
Patent
Quality of
Fwd. citations
2.568
Median
Relecura
Patent
Quality of
Fwd. citations
3
Average
Relecura
Patent Quality
of Bwd.
citations
1.166
Yellow LED patent
[1972]
Red LED patent
[1965]
Violet LED patent by
Maruska
[1973]
Blue LED patent by
Akasaki et al.
[1990]
Highest Relecura
Patent Quality for the
forward citations
Blue LED patent by
Shuji Nakamura
[1993]
IR LED patent
[1962]
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Patent Citation Analysis of Milestones
Red LED patent
[1965]
Yellow LED patent
[1972]
Red LED patent
[1965]
Yellow LED patent
[1972]
Violet LED patent by
Maruska
[1973]
Violet LED patent
[1973]
<-Forward Citations
Relecura Patent Quality ->
Click for an interactive graph
Click for an interactive graph
Blue LED patent by
Akasaki et al.
[1990]
Blue LED patent by
Shuji Nakamura
[1993]
Blue LED patent by
Akasaki et al.
[1990]
IR LED patent
[1962]
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Blue LED patent by
Shuji Nakamura
[1993]
IR LED patent
[1962]
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Patent Citation Analysis of Milestones
• Key Findings:
• No direct relationship between the BLUE LED patents and each of IR LED patent, Red LED patent and the yellow LED
patent.
• Dense cloud of patents around the Shuji Nakamura’s patent followed by Isamu Akasaki and Maruska’s patents.
• Considerable number of patents have directly built on the seminal Blue LED patents and a number of patents have also
stemmed from a combination of two or three of the seminal Blue LED patents.
• Shuji Nakamura’s Blue LED patent has got the highest Relecura Patent Quality among the seminal patents followed by
Akasaki and Amano’s patent.
• Considerable number of quality inventions were also built upon Maruska’s violet LED patent.
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Patent Citation Analysis of Milestones –
Blue LED patents
[email protected]
• A snapshot of three seminal patents related to the BLUE LED tech is
shown.
Click for an interactive graph
Violet LED patent by
Maruska
[1973]
• The graph is filtered to patents with degree 2 and above to reduce
density and to understand knowledge transfer patterns.
US5237182
Blue LED patent by
Akasaki et al.
[1990]
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Blue UV LED patent
assigned to Sharp
Blue LED patent by
Shuji Nakamura
[1993]
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Seminal Patents and their Citations
• Details of the patents and its citations considered in the study are
available here.
• The seminal patents considered are
Milestone
Publication
Number
Invention of the first IR- LED by Biard and US3293513
Pittman
Invention of the Red LED by Nick Holonyak
US3249473
Filing Year
Invention of the Yellow LED by Craford Magnus US3873382
George
Work on Violet LED by Maruska et al. at RCA US3819974
labs
1972
Work on Blue LED by Isamu Akasaki, Hiroshi US5122845
Amano et al. at Nagoya University, Japan
Work on Blue LED by Shuji Nakamura at Nichia US5578839
Corp, Japan
1990
1962
1965
1973
1993
• Click to view the seminal patents and their citations.
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BLUE LED Technology
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BLUE LED Technology- Why so important ?
• The Blue LED invention is a breakthrough that came after 20 years of intense research and development
since the previous milestone – The Purple LED. The Blue LED invention is not just important because of
the tremendous and prolonged amount of work and dedication that was put into it but also because it
opened avenues to a whole new world of lighting and igniting hopes of bringing light to the 1.5 billion
people who don't have it.
The Blue LED invention was the final piece of the puzzle to
create white light from an R-Y-B combination. Now, white
light is created by using either this RYB combination or by
employing a phosphor coating over a Blue LED.
This led to LEDs being used ubiquitously in
household/industrial/automobile lighting, backlighting,
medical equipment and in a host of other applications.
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http://energy.gov/eere/ssl/led-basics
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Blue LED technology- US 5578839
US 5578839 - Light-emitting gallium nitride-based compound semiconductor device by Shuji Nakamura
• The present invention relates to a light-emitting gallium nitride-based compound semiconductor device and, more
particularly, to a light-emitting compound semiconductor device having a double-hetero structure capable of emitting highpower visible light ranging from near-ultraviolet to red, as desired, by changing the composition of a compound
semiconductor constituting an active layer (light-emitting layer).
Key excerpts from the background section of the seminal patent• “All conventional LEDs are unsatisfactory in both output power and luminance, and have no satisfactory luminosity.”
• “No LED of double hetero-structure are known, in which the double hetero-structure is entirely formed of low resistivity GaN
based compounds and at same time has a light emitting layer of low resistivity, impurity doped InGaN.”
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Blue LED technology- US 5578839
On analyzing multiple level backward citations of this patent we observe that• Double hetero-structure light emitting semiconductors were developed since 1988.
• Shift from GaAs, GaP based semiconductors to GaN based compound semiconductors from 1980s.
• Patents related to Photodiodes and solar cells (employ counter mechanism to that of LEDs) act as feeders to the system
dating back to 1973.
• Insights on various experimentations on the type of substrate and buffer layer used in order to reduce lattice mismatches
for GaN based compound semiconductors from 1980s.
Summary of key technical problems from the background of the patent
• Inability to achieve LEDs of sufficient brightness in the BLUE wavelength band that are of practical use.
• Lattice mismatches in hetero-junction structures due to differences in atomic arrangement of the semiconductor and buffer
layers employed.
• Conventional epitaxial methods involve low controllability in doping impurity due to the need for high temperature of
operation.
• Difficulty in the manufacture of bulk GaN.
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Blue LED technology- US 5578839
Salient Technical Features of the Invention• Different compositions for each GaN based semiconductor
layer indicated in the figure by different dotted lines.
• All the GaN compound based layers possess Low Resistivity
(LR).
• The light emitting Indium Gallium Nitride (InGaN) layer is
impurity doped.
Field of the Invention• Visible light emitting semiconductor device which is excellent
in output power, luminance and luminosity for the first time.
• Ranging from Near UV to RED (365-620nm) (by changing
composition of light emitting layer).
http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Fundamentals/Electromagnetic_Radiation
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Blue LED technology- US 5578839
Properties of GaN based compounds• GaN, GaAlN, InGaN have a direct band gap and
BG= 1.95 eV to 6 eV. Thus requiring relatively
lesser energy to excite and improving electrical to
light conversion efficiency.
• GaN based compounds are relatively better in
stability when compared to GaAs, GaP etc.
Properties of Double Hetero-Structure devices• Relatively better luminance compared to existing
MIS (Metal-Insulator-Semiconductor) type homojunction semiconductors.
• Relatively higher light emitting output power
compared to existing MIS type semiconductors.
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1.
© Relecura Inc.
Wikipedia. 2013. Direct and indirect band gaps. [online] Available at: http://en.wikipedia.org/wiki/Direct_and_indirect_band_gaps
[Accessed: 6 Dec 2013].
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Blue LED technology- US 5578839
Experimental results described in patent
document• Obtaining a higher intensity at ~480nm
(BLUE) when the light emitting layer is doped.
• Experiments also indicate the effect of
varying the thickness of the light emitting
layer on the relative light intensity obtained.
Nakamura, Shuji. Multilayer Elements with Indium Gallium Nitride on Clad Layers, Dopes for P-n Junctions. Nichia Chemical Industries, Ltd.,
assignee. Patent US5578839. 26 Nov. 1996.
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Blue LED technology- US 5578839
Geo Spatial Layout • In this Geo-Spatial Layout, the Longitudes
correspond to the year of filing of the
patent, and the latitudes correspond to
different technology buckets.
• The nodes indicate patents and the size
of the nodes is proportional to the
number of forward citations.
• This layout consists of two level forward
and backward citations of the seminal
patent – US5578839.
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Blue LED technology- US 5578839
Observations:
• The tech areas contributing to Blue LED invention
are (From the backward citations)
a) Semiconductors
b) Photolithography
c) Optics
d) Domestic Appliances
• The prominent technologies that spun out of this
invention/technology are (From forwards)
a) Semiconductors
b) Drugs & Medical Chemistry
c) Photolithography
d) Optics
e) Lighting
• It can observed that the use of the Blue LED
technology in Drugs and Medical Chemistry gained
prominence since 2003-2005.
November 2014
Click for an interactive graph
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Blue LED technology- US 5578839
• Various Relecura Technology Categories represent
different latitudes with weighted edges connecting
‘similar’ patents.
• The size of the node is proportional to the
‘Relecura Patent Quality’ of that patent.
• It is worth noting that a significant number of links
also emerged from areas viz. Sealing materials and
drilling
fluids; Nanostructure
applications;
Dentistry – Oral care and Crystal Growth.
Unclassified
Click for an interactive graph
• The vast breadth of applications of the Blue LED
technology is clearly evident from the layout.
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Disclaimer
This document is provided for information purposes only and the contents hereof are subject to change without notice. This document,
including the information and analysis and any opinion or recommendation, is neither legal advice nor intended for investment purposes. This
document is not warranted to be error-free, nor subject to any other warranties or conditions, whether expressed orally or implied in law,
including implied warranties and conditions of merchantability or fitness for a particular purpose. Relecura Inc. specifically disclaims any
liability with respect to this document and no contractual obligations are formed either directly or indirectly by this document.
Relecura is a web-based patent and portfolio analysis platform that uses a knowledge discovery framework to simplify IP analysis for prior-art
search, technology landscaping, competitive intelligence, and IP commercialization activities. For more details visit www.relecura.com or write
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