디스플레이기술비교 : OLED 와 LCD 구조및동작원리, 특징비교 박기찬
명암비 (Contrast Ratio)
응답속도 (Response Time)
시야각 (Viewing Angle)
Black Image OLED 는매우낮고균일한 black level 구현이가능하고, 시야각에따른빛샘도없음. AMOLED Black 휘도 구분 CR (Static) F.W. 휘도 Black 휘도 OLED >200,000:1 200 nit <0.001 nit LCD IPS ~1,600:1 450 nit ~0.3 nit VA ~5,000:1 450 nit ~0.1 nit Black Uniformity TFT-LCD LCD 는여러요인에의해서균일도저하 - Cell gap control - Rubbing - 기구간섭등 시야각 Black OLED: 자발광이므로측면시야각빛샘없음 LCD : 원천적인측면시야각빛샘존재
LCD 와 OLED 의기본구조 LCD(liquid crystal display) LCD panel signal power Backlight: LED or CCFL OLED(organic light emitting diode) OLED panel signal + power
LCD Panel 의동작원리 ( 편광판 ) (Thin Film Transistor) ( 액정 ) ( 편광판 )
LCD Module 구조
LED Backlight Edge-lit (side-lit) LED Back-lit (direct-lit) LED
LCD Panel 구조 Data 배선 Gate 배선 TFT 화소전극 Pixel electrode Common Electrode Black Matrix (ITO) Spacer Polarizer Black Matrix (BM) Color-Filter (C/F) Seal Short Color Filter Substrate TFT L/C TFT-Array Substrate Color-Filter (Blue) Alignment Layer Polarizer Bonding PAD Pixel Electrode (ITO) Storage Capacitor
Image Refresh: Line-by-Line Scanning 원본이미지 (60Hz Frame Freq.) 1/60 sec. 1/60 sec. 1/60 sec. 1/60 sec. 1H time scan #1 scan #2 scan #3 scan #4
Image Refresh: Line-by-Line Scanning 원본이미지 (60Hz Frame Freq.) 1/60 sec. 1/60 sec. 1/60 sec. 1/60 sec. scan #5 scan #6 scan #7 scan #8
Active Matrix Display data data data data gate lines or scan lines data lines
Active Matrix Addressing data for 1st line data for 2nd line
Active-Matrix LCD 구동 Gate driver IC C LC C S Data line ITO Common electrode ITO Pixel electrode Source Driver IC Gate line TFT T f (frame 주기 = 1/60 sec.) T on (1H time)
LCD 와 OLED 특징비교 LCD BM Color filter Glass Common Electrode Signal Line Pixel ITO TFT Light Liquid Crystal Glass Back Light OLED Encapsulation Glass or Metal Can Cathode Organic Layer Signal Line Bank Anode D G S TFT Active Light Glass 1. 액정의광학적이방성 좁은시야각 2. TFT 특성과계조표현의상관관계작음. 3. Backlight 필수 상대적으로두꺼운모듈구조 4. 액정분자회전으로휘도결정 느린응답속도 5. 완벽한빛차단불가능 제한된명암비, 색재현율감소 1. 광학적이방성없음. 방향과무관한명암비 2. TFT 특성에의해서전류와계조표현 고성능 TFT 필요 3. Backlight 불필요 얇은모듈구현 4. 전자의이동으로휘도결정 고속응답 5. 완벽한검정색표현가능 높은명암비, 일정한색재현율
OLED 소자구조 Electroluminescence
Active-Matrix OLED ELA-based Poly-Si TFT ( 삼성 ) IGZO TFT (LG)
AMOLED 화소구조 ELVdd ELVss
AMOLED 의전원및신호공급 Current Voltage signal ELV SS Input Gate PCB
Mobile AMOLED Display [ 삼성 Galaxy S2 ] - 800ⅹ480, 4.27 117 μm x 39 μm Blue Red Green [ Bottom View ] [ Top View ]
OLED 전압구동 OLED 에전압을인가하여구동하는경우의문제점. L OLED 장시간사용에의한특성변화 V DATA 휘도편차 V DATA
구동방식에따른 OLED 수명
Image Burn-In (Image Sticking) OLED PDP
OLED 전류구동 OLED 에전류를인가하여구동하는경우, 공정불균일성및소자열화의영향이적다. 균일한휘도를구현한다. L OLED V SUPPLY I DATA 균일한휘도 I DATA
AMOLED 화소구동원리 Active matrix 방식으로 capacitor 에전압데이터를저장한다. 이전압데이터로전류원의전류를결정해서 OLED 를구동한다. gate line I DATA V DATA V SUPPLY C STG data line
2T-1C AMOLED 화소구조 V GS V Data + V T + α gate line V SUPPLY gate line V SUPPLY I DATA C STG V GS C STG V GS I DATA data line data line
LC 응답속도개선 : Over-Driving
Motion Blur 문제 Impulse Display short duration long duration short duration long duration 1/60 sec. 1/60 sec. Hold-Type Display 1/60 sec. 1/60 sec.
Impulse Display vs. Hold-Type Display
Motion Blur 개선 60Hz Hold-Type Display 1/60 sec. 1/60 sec. 120Hz Hold-Type Display interpolated image interpolated image 1/120 sec. 1/120 sec. 1/120 sec. 1/120 sec.
소비전력비교 LCD OLED 100W 10W Dark image 100W 200W Bright image
명암비와색포화도 LCD OLED Contra st ratio ( 명암비 ) Color saturati on ( 색포화도 )
PDP (Plasma Display Panel) PDP Cell 구조
외부광에의한 PDP 명암비저하
PDP 명암비개선
PDP 의계조 (Gray Scale) 표현 PDP TV image Time Gray scale : Controlling width of sustain period in each sub-field SF1 SF2 SF3 SF4 SF5 SF6 SF7 SF8 sub-field scan line 1 2... 1080 1T 2T 4T 8T 16T 32T 64T 1TV field (1/60 sec.) 128T address sustain
PDP Specification
RGB Color Generation ETL Emitting layer Cathode HTL Anode Glass Low Efficiency
WRGB Pixel
RGB OLED 의문제점 FMM 제작편차, 처짐, shadow 효과등으로 인해서 300 ppi 이상의고정세및대형 TV 구현곤란. (Galaxy Note II: 265ppi)
Poly-Si TFT 의 V T 불균일성
Poly-Si TFT AMOLED 의 V T 보상효과 [ w/o Compensation ] [ V T Compensated ]
Samsung Galaxy AMOLED 의 V T 보상
Galaxy AMOLED 의 V T 보상원리 1 Stop emission 2 Initializing 3 Initialized 4 V T compensating 5 V T compensated 6 Resume emission
LCD 와 OLED 장단점비교 LCD OLED Contrast ratio ( 명암비 ) X O Color saturation ( 색포화도 ) X O Viewing Angle ( 시야각 ) X O Motion Blur ( 동영상끌림 ) O O Burn-in (image sticking) O X 소비전력 밝은화면 O X 어두운화면 X O 두께및무게 X O 가격 O X 수명 O?