전계방출형 신광원과 산업적 응용

정보디스플레이학회 광원연구회 세미나
전계방출형 신광원과
산업적 응용
금호전기 R&D Center
2008. 03. 28
김광복
BLU 각 광원별 비교
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Light source
CCFL
EEFL
HCFL
FFL (Hg)
FFL (Xe)
FEL
OLED
LED
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Efficiency
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Color gamut
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T-dependence
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Response time
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Environment
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Technical maturity
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Lifetime
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BLU Structure
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Copyright © Kumho Electric Inc., Research Institute, 2007
2
Local Dimming 이유
Conventional BLU
Conventional LCD TV
CCFL
BLU
BLU
LCD
Optic
al F i l m
LCD P
anel
• Low cost
• High efficiency
• High power consumption
• Low contrast, Motion blur
• Mercury pollution
Local Dimming BLU
LCD BLU
Fluorescent Lamp
(Gas Discharge)
CCFL
EEFL
HCFL
EEFL
LCD
LED
FEL
BLU
OLED
Multi chip
Power LED
CNT FEL
Discrete LED
FFL
• High contrast, No motion blur • High Cost
• Low power consumption
• Good color gamut
Copyright © Kumho Electric Inc., Research Institute, 2007
3
전계 방출 소자 란 ?
Copyright © Kumho Electric Inc., Research Institute, 2007
4
Field Emission Device
‹ FED (Field Emission Display) - Triode
- Futaba, Full Color 8.0”
VGA FED, Mo-tip [2003]
Phosphor
Packaging
R
B
Gate Electrode
e-
Anode Electrode
eInsulator
Spacer
Spacer
Frit Seal
ee-
Black MatrixG
FED
Application
LCD
- Samsung, Full Color 38.0”
HD-SVGA FED, CNT-Paste [2003]
Cathode Electrode
Driving
System
Getter
Spacer
Emitter
Switching Circuit
‹ FEL (Field Emission Lamp) - Triode
White Phosphor
- Kumho, 14” FEL(’07.12)
Packaging
Anode Electrode
Gate Electrode
e-
eInsulator
Spacer
Spacer
Frit Seal
ee-
Application
Cathode Electrode
Inverter
Getter
Spacer
Emitter
Free of Complex Switching & Driving System
Copyright © Kumho Electric Inc., Research Institute, 2007
5
전계방출형 신광원 특징
• CNT의 고효율 전계방출 특성을 응용한 평면형 면발광 램프
• 저 발열 및 광범위한 작동 온도 범위 (-30℃~90℃)
• 두께가 얇은 초박형이며, 대면적화가 용이
• 인체에 유해한 수은이 포함되지 않은 친환경 램프
• On/off, 안정화 시간이 빠름
• Dimming 조절 기능이 쉬어 소비전력 절감 효과
• 고효율, 저전력형, 장수명 램프가 가능
Copyright © Kumho Electric Inc., Research Institute, 2007
6
What’s Field emission?
- Quantum mechanical tunneling from surfaces at ~ 0.5V/Å (1897, Wood)
- Thinning of vacuum barrier by external field
- Fowler-Nordheim equation behaviors
전계방출 전류밀도 -> F-N 거동
Vacuum
EV
Φeff
Fermi Sea
J = aE2Φ-1exp(-bΦ3/2/E)
-e2/2x Weak Field
(thermionic emission) where
-eFx
J : Current density (A/cm2)
E : Applied field (V/cm)
Φ : Work function (eV)
-
Φ
EF
No Field
e
Tunneling
Metal
Distance
Intense Field
(field emission)
a ~ 1.5x10-6 (β2A/ Φ) exp(10.4/Φ1/2)
b ~ 6.44x107 Φ3/2/β = kh/r
A : emitting area (cm2)
β : geometric factor dependent on
the electrode configuration
Copyright © Kumho Electric Inc., Research Institute, 2007
7
Fowler-Nordheim Plot
J = aE2Φ-1exp(-bΦ3/2/E)
-> 전류-전압으로 표현
I = aV2exp(-b/V) :
Ln(I/V2) = -b/V + const.
(전계 방출 전류 확인)
a ~ 1.5x10-6(β2A/Φ)exp(10.4/Φ1/2)
b ~ 6.44x107 Φ3/2/β = kh/r
E 최대, Φ 최소 => 전계 방출 극대
β ∼ 2,000
구조(E)와 재료(Φ) 설계 병행
=>최적의 전자 방출 재료
Copyright © Kumho Electric Inc., Research Institute, 2007
8
Field Enhancement Factor(β)
‹Silicon type(Tip)
‹Spindt type(Tip)
E = β(V/d)
β = kh/r
Ex) 50x(50V/μm) ~ 2,500 V/μm
‹CNT type
r
β~l/r
~ μm / nm
l
~ 1,000
CNT > 1,000
To get low operation V, increase β
Copyright © Kumho Electric Inc., Research Institute, 2007
9
FED Trends (1)
5.2” Mono
PixTech
Product
10.4” VGA
PixTech
5” Mono
Futaba
4” Mono
LETI, ‘91
13.2” SVGA
Candescent
13.2” SVGA
Candescent
8.0” Mo-tip
Futaba
4.0” QVGA
Samsung
5.2” QVGA
Samsung
15” VGA
PixTech
10.4” XGA
Samsung
5.4” CNT-G
C-dream
4~5” Color
Canon/Fujitz
4.5” CNT
Samsung
9.0” CNT-diode
Samsung
15” CNT-triode
Samsung
5.0” CNT-triode
Samsung
2.4” Color
Candescent
5.6” QVGA
Motorola
5.3” QVGA
Candescent
5.2” QVGA
Candescent
4.7” NED
Motorola
26” Tip-FED
FET(Sony)
40” SED
14.5” CNT-G
Canon-Tosiba
Noritake
32” CNT-P
Samsung
5.0” CNT-P
ETRI
15” CNT-P
Samsung
40” CNT-BLU
Samsung
15” CNT-FEL
Nanopacific
5.0” CNF-P
NEXEN
<40” CNT-FEL
KUMHO
FED -> Applications
Prototype
~ 1995
13.2” SVGA
Candescent/Sony
2.6” BSD
Matsushita
1996
1997 ~ 1998
1999
2000
2001 ~ 2006
FED
LCD
- Sony, FED 26”
Mo-tip [2007]
- Futaba, Full Color 8.0”
VGA FED, Mo-tip [2003]
- Motorola, Full Color 5.6”
QVGA FED [1998, 5.]
- PixTech, Mono 12.1 XGA,
Full Color 5.6” QVGA FED [1999]
- Candescent/Sony, Full Color
13.2” SVGA FED [1999,2001]
- Matsushita, Full
Color 2.6”
BSD-FED, [2003]
Copyright © Kumho Electric Inc., Research Institute, 2007
- Samsung, Full
Color 42.0”
HD-SVGA FED,
CNT-Paste [20032004]
- KUMHO, FEL 14”
CNT-Paste [2007]
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FED Trends (2)
-Canon-Toshiba (JPN)
· Low cost, Large size SED (Surface-conduction Electron-emitter
Display) by Printing & Ink-jet Technology, 10” panel [1997]
· Developed 36”~52” HDTV SED Panel (>300cd/m2, ~160W, Driving
Volt: 15V, 8000:1) [2004, 2005, 2006]
· Target to Market : < 60” Mid-Large Size Display
· SED Inc. : ~400 man-power
(Holding with Patents problems)
-Futaba (JPN)
· Early Commercial Stage by Micro-tip Technology (5~7” Mono)
· Demo. 8”, 11.3”, 14.4” Full Color Panel at SID’07 [2007]
· Pilot Line : ~120 man-power
· Target to Market : Mid-Size
· Selling to Market with Micro-gap FED for Indicator
Copyright © Kumho Electric Inc., Research Institute, 2007
11
FED Trends (3)
-Sony / FET (JPN)
· Developed 26” SXGA(1280x1024) FED
by nano micro-tip cathode [2007]
· Micro-tip Technology Transfer
from Candescent
26” full-HD
· Developing CNT-FED
· Ready to launch to market for Broadcast from ’09
-LETI (FRN)
· Developing CNT-FED
by direct-growing of CNTs
. Demonstration 6”, mono panel
Copyright © Kumho Electric Inc., Research Institute, 2007
12
FED Trends (4)
-Noritake-Ise (JPN)
· Developing 40” panel for LCD Back-light, projection light and
electronic board [2005]
· Finished NEDO Project (~¥500 millions/year, 3yrs)
· Seek Partner to launch CNT-BLU, Lamp application
-Motorola (USA)
· Full Color 5.6”, QVGA FED by micro-tip process [1998]
· Full Color 15”, QVGA FED by micro-tip process [2001]
· CNT FED development (NED: Nano-emissive Display),
CVD-grown CNT(500℃, 2min.) 50V operation
· Target Market : 50” FED TV [2005~ ]
· Under Developing for CNT-FED
15” VGA, Micro-tip
Copyright © Kumho Electric Inc., Research Institute, 2007
13
FED Trends (5)
-Hitachi (JPN)
· Developed 4” FED and failed by MIM Technology
· Grouping CNT-FED (Hitachi Display)
· Under Developing for CNT device
-Matsushita (JPN)
· Developing BSD(Ballistic electron Surface-emitting
Display) type FED
· Developed 2.6” full color panel [2002], 10.5” full color
panel [2003]
-PFE (ENG)
· Developed 14” PFE type FED [2001]
· Low cost, large size adaptable due to printable process
Copyright © Kumho Electric Inc., Research Institute, 2007
14
FED Trends (6)
-ITRI (Tiwan)
· Developing ~7”급 CNT-FED
· Developing 20” CNT-BLU by printable-CNT
-ETRI (KOR)
· Active-matrix FED (TFT + CNT emitter)
· Developing ~7” Dynamic CNT-BLU
CNT
5”, QQVGA, CNT-FED
Source
Drain
TFT Gate
7”, CNT-FEL
Copyright © Kumho Electric Inc., Research Institute, 2007
15
FED Trends (7)
-TECO (Tiwan)
· Developing ~9”급 CNT-FEI
· Launching to market for Banking machine
Copyright © Kumho Electric Inc., Research Institute, 2007
16
FED 연구 동향 (8)
-Samsung (KOR)
10.4” micro-tip
· Developed Micro-tip FED 5.2”, 10.4”, 15”급 (‘94~’97)
· Developed CNT-FED 7”, 15”, 32”, 38”급 (’01~’03)
· Developing CNT-BLU 15” ~ 40” (’05~present)
38” CNT-FED
6” CNT-BLU
Copyright © Kumho Electric Inc., Research Institute, 2007
17
CNT 응용 기술
Copyright © Kumho Electric Inc., Research Institute, 2007
18
CNT-FEL : Requirements
Cathode
CNT
Lighting
High reliable field emitter array
Low cost
Anode
High efficiency & brightness
Good color gamut
Packaging
Mass production & Reliability
Low cost
Structure
Driving
Evaluation
High acceleration voltage
Good uniformity & fill factor
Low cost
Simple circuit & stability
Low cost
Aging & reliability
Life time
Copyright © Kumho Electric Inc., Research Institute, 2007
19
CNT : Carbon Nano Tube
‹탄소 결합체의 종류
‹탄소나노튜브의 구조 및 종류
SWNT
DWNT
‹Graphite sheet
MWNT
1985: Kroto, Smalley: C60(Fullerene) 발견 됨
1991: NEC의 Ijima에 의해 탄소나노튜브가 발견 됨(Nature지)
아크 방전법으로 다중겹 탄소나노튜브(MW-CNT)를 합성
1994: UC Berkeley의 Zettl 그룹에서 탄소나노튜브에서의 전계방출 특성이 보고됨
1996: Rice Univ.의 Smalley 그룹에 의해 단일겹 탄소나노튜브(SW-CNT)가 합성됨
Copyright © Kumho Electric Inc., Research Institute, 2007
20
Current Density (mA/cm2)
Cathode Plate : 전자방출원
‹ Paste Printable
Screen Printing
Nano-C
Mixing
Lithography
0.6
After Surface Treatment
0.5
0.4
0.3
0.2
0.1
as printed
0.0
1.6
2.0
2.4
2.8
3.2
3.6
Electric Field (V/um)
Binder
Surfactant
CNT emitters
Firing & Surface Treatment
Conducting
Particles
‹ Gate structure
Phosphor
Al layer
CNT emitter
Insulator
Cathode
Gate
<Internal Top-gate>
Copyright © Kumho Electric Inc., Research Institute, 2007
<Lateral gate>
21
4.0
Anode Plate : Phosphor efficiency
‹ Crazy-Capentry Model
Radiation recombination
at the luminescence center
e-h pair recombination energy
Depends on Host characteristics
ηcr = (1-τb) · hνem · ηtηaηesc / βg · Wg )
Back-scattering
coefficient
e-h pair transfer to the
luminescence center
e-h 광생성효율
부활성제의
성질에 의존
Escape of visible light
βg ~ 2.9 for ZnS system, 7.0 for Y2O2S
ηa ~ ηesc ~ 1 for CL phosphor
η (lm/W) =
3.14 · Aa · L
<= Emission
Va · Ia
Aa = 100cm2, L = 10,000 cd/m2
Va = 10kV, Ia = 0.8mA
@ Diode
Copyright © Kumho Electric Inc., Research Institute, 2007
η ~ 39 lm/W
22
Gate Structure : 전계 전자의 양을 조절
구 분
분 류
특
징
전 원
Top-External
Metal Mesh(누설전류)
Glass-Mesh(고가)
Triode
Top- Internal
Direct-Pattern
(공정복잡)
Triode
Tetrode
Direct-Pattern
(공정복잡)
Tetrode
Direct-Pattern
(공정간단,아킹)
Diode
전극
위치
Under
Lateral
Single
전극
수
Double
Top-Internal
Under
선택적 방법
Anode
elect
ron
CN
T
Sp
ac
er
Mesh
gate
Cathod
e
Triode
Triode
Tetrode
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23
CNT 신광원 – Lateral 평면형 (II)
‹ ㈜나노퍼시픽
Triode형 CNT 발광 모듈 개발
2005. 4.
2005. 10.
5”급 CNT Flat
17” 급 CNT Flat
Lamp
Lamp
(Bipolar Triode형)
(Bipolar Triode형)
백색휘도:
백색휘도:
10,000 cd/㎡
Efficiency: 60 lm/W
10,000 cd/㎡
Efficiency: 60 lm/W
저가형, 고신뢰성,
장수명, 고효율
공정 개발 중
63lm/W (14”제품)
Copyright © Kumho Electric Inc., Research Institute, 2007
24
CNT 신광원 – Lateral 평면형 (IV)
‹ Applied Nanotech (USA)
-. Lateral형 Triode식 CNT 발광 모듈 개발
5,000 cd/m2
IDW’06(JPN)
-. Triode식 CNT FED 모듈 개발
-. CNT 전자방출원 개발
IDW’06(JPN)
IDW’06(JPN)
Copyright © Kumho Electric Inc., Research Institute, 2007
25
CNT 신광원 – Top Gate 평면형 (V)
‹ ETRI(KR)
-> Glass내부 Taper된 미세 hole로 전자 궤적 제어 방식은 유사
-> 게이트 전극상의 전극 인가시 주기를 교번으로 진행
Gate swing 구동
E-beam
7”급 (06.12)-ETRI
Æ Fill factor를 높일 수 있기 때문에 전계방출 광원에서
휘도, 효율, 수명을 극대화시킬 수 있음.
Copyright © Kumho Electric Inc., Research Institute, 2007
26
CNT 신광원 – Top Gate 평면형 (VI)
‹ Display Tech 21 (JPN) : LCD-BLU용 광원
-> 평면형 다이오드 구조이며, 구체적인 구동/전원에 대한 근거는 부족.
-> 타일링의 개념을 도입하여 대면적 LCD-BLU용 광원으로 개발 예정
Nikkiso(JPN) : 10,000 cd/m2
’05.12 (JPN)
’07.03.02 (JPN)
’07.03.02 (Nikkei)
Copyright © Kumho Electric Inc., Research Institute, 2007
27
CNT 신광원 – 벌브형
‹ Ise-Noritake (JPN)
-. 벌브형 전계방출광원을 집중적 개발하고 있음.
-. 금속메쉬형 게이트 전극 채용하여 발열이 심하고 전류효율이 50% 수준
-. CL 특성이 우수한 광원 (50,000cd/m2)
’07.03 동경나노텍 (JPN)
‹ Toray (JPN)
-. 삼극형 전계방출광원
-. 구체적 적용된 기술 공개되지 않음.
’07.03 동경나노텍 (JPN)
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28
CNT 신광원 – 튜브형 외
‹ EPFL(스위스)
-. 이극형 전계방출 광원
-. 10,000cd/m2, 40lm/W, @ 5kV
‹ 기타 응용 광원 ; DIL(Digital Information Lighting)
FUTABA
DIL용
Copyright © Kumho Electric Inc., Research Institute, 2007
29
기타 신광원 – CNW
‹ CNW (Carbon Nano Wall) -JPN
-. Thermal CVD방식을 이용한 선택적 기판위에 에미터 성장 (고온성장)
-. 습도에 강하고 전계방출특성 우수하나 균일도 개선 필요함.
-. 일본내 산학중심으로 활발히 개발중에 있음.
-. Diode 구조로 전류제어/밝기균일도 한계성
튜브형
’06.06 (JPN)
평면형
’07.03 (Kochi-Univ. JPN)
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30
Local Dimming : CNT-BLU (Top-gate)
‹ 삼성SDI
-. Top-gate 방식의 저가 제조 공정 개발 중
-. 15”급에서 개발 이슈 해결 및 40”급 BLU 개발 중
6인치 시작품 – 삼성
32인치 시작품 – 삼성
출처:CNT BLU기술동향세미나-삼성종기원
Copyright © Kumho Electric Inc., Research Institute, 2007
31
LED, CCFL, CNT 성능 비교
12,000
18,000
8개
출처:CNT BLU기술동향세미나 재구성
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32