液晶物理學(xué)2LCD顯示原理

1、Chapter 2 LCD顯示原理1液晶以分子排列分類(lèi)Nematic liquid crystal線(xiàn)狀液晶LCD用液晶之主流排列特點(diǎn):分子傾向指著某個(gè)特定方向2液晶之介電異向性液晶之介電常數(shù)值越大產(chǎn)生的induce dipole越大介電異向性決定LC之轉(zhuǎn)動(dòng)3Induced Dipole04LC birefringence n定義n|nn= n|- nLCLCn會(huì)改變?nèi)肷涔獾钠襁M(jìn)而讓LCD產(chǎn)生顯示的效果EEEEEE5液晶配向之方法配向過(guò)程: 配向膜印刷 rubbing process 玻璃對(duì)組注入LCInject LCPanel assemblyAttach SpacersApply Seal

2、antRubbingCell ProcessApply PI FilmSeal6Homogenous alignment (ECB)Homeotropic alignmentTwisted alignment (Twisted nematic)Hybrid alignment配向過(guò)程: 配向膜印刷 rubbing process 玻璃對(duì)組注入LC常見(jiàn)液晶配向排列模式Alignment film7晶體光學(xué)光入射液晶之可能現(xiàn)象和效應(yīng)吸收(absorption)和穿透(transmission)折射(refraction)和反射雙折射效應(yīng)(birefringence effect) 旋光效應(yīng)(pol

3、arization rotation effect)散射(scattering)繞射(diffraction)色散(dispersion) 8Polarized WaveLinear PolarizationCircular PolarizationLeft-hand/Right-handElliptical Polarization9Polarization of Optical Waves光偏極化之物理機(jī)制: (1) Dichroism (selective absorption)(2) Birefringence (double refraction)(3) Reflection(4)

4、ScatteringEx: dichroism10相位延遲與偏振狀態(tài)之關(guān)係 = 0 或 時(shí), 電場(chǎng)為線(xiàn)偏極化, 偏振方向與x軸之夾角 = /2 且 時(shí), 電場(chǎng)為圓偏極化(正號(hào)為左圓;負(fù)號(hào)為右圓偏振) 若 時(shí), 電場(chǎng)為橢圓偏極化且主軸在x或y軸上(3)其餘狀況為橢圓偏振0/2-/2-/43/4-/4-3/4E=Ex(z,t)+Ey(z,t)11為相位差12=0Time increases線(xiàn)偏振圓偏振=/2ExEyEyExEyExExEyExEyEyExEyExExEy(Assume Eox=Eoy)圖示相位延遲與偏振狀態(tài)之關(guān)係13雙折射晶體種類(lèi)光在一晶體內(nèi)傳播時(shí)若看到兩種折射率則此晶體為雙折射晶

5、體(例如液晶)光在雙折射晶體內(nèi)的折射率值跟光的入射角度和偏振有關(guān)單光軸晶體nx=ny nz雙光軸晶體nx ny nz14k正單光軸晶體之折射率橢圓球nxnynzneffno正單光軸晶體 nx=ny01. 顯示器用液晶為正單光軸液晶2. 棒狀液晶為正單光軸光入射時(shí)單光軸晶體之雙折射特性短軸 no=nx=ny光入射晶體時(shí):晶體之兩個(gè)折射率值分別為k垂直平面和折射率橢圓球產(chǎn)生之橢圓截面之長(zhǎng)短軸橢圓截面長(zhǎng)軸15k負(fù)單光軸晶體(negative uniaxial)之折射率橢圓球nxnynzneffno負(fù)單光軸晶體 nx=nynzBirefringence n=neff-no 時(shí),旋光效應(yīng)NWV=0As

6、V increasesi.e. u1,=90o, =0o1st minimum and polarization rotation effect(NW)43TN之e-mode和o-mode入射光偏振和第一層LC分子平行e-mode入射光偏振和第一層LC分子垂直o-mode44對(duì)比的定義CR對(duì)比高對(duì)比低NW黑畫(huà)面電壓白畫(huà)面電壓45視角的定義CR10No Gray-Scale Inversion Color Dispersion (uv0.004)46顯示器座標(biāo)定義Normal= 0: Viewing Angle: Viewing Direction=0=180=270=90=0=180=270=

7、90Normal= 0: Viewing Angle: Viewing Direction上下左右47Iso-Contrast Contour204060800030609012015018021024027030033048TN-LCD的視角限制Bright stateDark stateLC residual phaseLC optical anisotropy視角不足等對(duì)比(iso-CR)圖CR=1049TN-LCD的視角限制LC directorUpperRightLowerLeftTop ViewUpperLowerGlass substrateSide ViewLC directo

8、rGlass substrateGrey Scale Inversion50GSI angleGray Scale Inversion(GSI)的定義51n=0Gray Scale Inversion(GSI)原理LC (液晶分子)光52Gray Scale Inversion(GSI)原理V1V1V2V2V1V2V1V2Gary scale inversion灰階反轉(zhuǎn)53灰階反轉(zhuǎn)(Gray Scale Inversion)54CIE (Commission Internationale de lEclairage ) x-y色座標(biāo)顏色用座標(biāo)來(lái)表示越靠近邊界顏色越飽和白色座標(biāo)?55GSICol

9、or dispersion視角的定義56NTSC Ratio(色域)的定義National Television System CommitteeEBU: European Broadcasting Union NTSC ratio = 100 %NTSCRGBcolor gamutColor saturation index 57High NTSC ratioLow NTSC ratioNTSC ratio 色彩飽和度58Equivalent Circuit of a PixelCapacitorLC layer59LCD Module StructureModulePolarizerCF

10、(Color Filter)LCArrayCell (Panel)Back Light + PCBPolarizer60Definition of Resolution 1-pixel including R,G,B 3-sub-pixel1-G-sub-pixel61CF頻譜Backlight頻譜LCD顯色原理B/LCF= outputx62RGBCMYWRGB混色關(guān)係63Aperture Ratio of a PixelEffective area= Aperture Ratio64QVGA: 320 xRGBx240VGA: 640 xRGBx480SVGA: 800 xRGBx600X

11、GA: 1024xRGBx768SXGA: 1280 xRGBx1024SXGA+: 1400 xRGBx1050UXGA: 1600 xRGBx1200Some terminology of display resolution NTSC: 525-linePAL: 625-lineHDTV: 1920 x1080VCD: 352x288DVD: 720 x576QCIF+a: 220 x176QCIF: 144x176Data DisplayVideo Display65Passive Matrix LCD (PM-LCD) vs. Active Matrix LCD (AM-LCD) PM-LCD: TN/STN 1.無(wú)開(kāi)關(guān)元件 2.沒(méi)有操作的畫(huà)素會(huì)受其他 畫(huà)素寫(xiě)入電壓的影響 3.中低解析度, 低單價(jià)產(chǎn)品AM-LCD: 1.以TFT作為畫(huà)素(pixel)開(kāi)關(guān)及儲(chǔ) 存電容 2.適合高解析度66TFT的作用因TFT元件的動(dòng)作類(lèi)似一個(gè)開(kāi)關(guān)(Switch)，液晶元件的作用類(lèi)似一個(gè)電容，藉Switch的ON/OFF對(duì)電容儲(chǔ)存的電壓值進(jìn)行更新/保持。SW ON時(shí)信號(hào)寫(xiě)入(加入、記錄)在液晶電容上，在以外時(shí)間 SW OFF，可防止信號(hào)從液晶電容洩漏。在必要時(shí)可將保持電容與液晶電容並聯(lián)，以改善其保持特性.保持電容- 儲(chǔ)存電容TFT元件加入電壓液晶67GDSDSGT