null液晶材料及液晶顯示器簡介液晶材料及液晶顯示器簡介
傅永貴教授兼系主任/所長
成功大學物理系/光電所
E-mail:andyfuh@mail.ncku.edu.tw
2007-01-16 台中一中高中物理研習
(綱要)Outlines(綱要)Outlines簡介
˙市場
˙液晶簡介
液晶光學性質
液晶顯示器模式
LCD結構圖 LCD結構圖Or 3M DEBF簡介 Twisted Nematic Liquid Crystal Displays Twisted Nematic Liquid Crystal DisplaysTFT: Thin Film Transistornull2004年我國大型TFT產值比較
2004年全球大型TFT產值約346億美元,而我國產值較前一年成長67%,估計佔全球比重約38%,僅次於韓國45%;另外,日本約佔17%,排名第三(圖一)。2004年我國中小型TFT產值比較
2004年全球中小型TFT產值約102億美元,而我國產值較前一年成長140%,估計佔全球比重約12%,次於韓國78%,而日本約佔10%,排名第三。 2004年我國中小型TFT產值比較
2004年全球中小型TFT產值約102億美元,而我國產值較前一年成長140%,估計佔全球比重約12%,次於韓國78%,而日本約佔10%,排名第三。 我國大型TFT廠商營利表現比較
我國大型TFT廠商營利表現比較
韓國大型TFT廠商營利表現比較
韓國大型TFT廠商營利表現比較
null(綱要)Outlines(綱要)Outlines簡介
˙市場
˙液晶簡介
液晶光學性質
液晶顯示器模式
物質的相變 物質的相變何謂液晶? 何謂液晶? nullnull中間相
(Mesophases) 結晶狀的固體
(Crystalline Solid) 各向同性的液體
(Isotropic Liquid) null液晶的分類 1) Thermotropic (熱致液晶) 2) Lyotropic (溶致液晶)因溫度的改變而產生相變 因溶於溶劑中濃度比例的改變而產生相變 以產生相變之原因來區分Thermotropic
(熱致液晶)分子形狀排列方式nullClassification of liquid crystal:
Based on their symmetry of molecular arrangements, liquid crystals are divided into three major classes:
Nematic Phase (向列相)
Cholesteric Phase (膽固醇相)
A distorted form of the nematic phase
Smectics (近晶相) Liquid Crystals (LCs)Liquid Crystals (LCs)Nematic 液晶Nematic 液晶Nematic 液晶特性: (a) 分子的重心位置沒有次序性。
(b) 分子的排列方向存在一定程度的次序性,分子傾向平行於某個共同的方向去排列,如圖所示,我們定義這個方向為導軸 (Director Axis)以 n 表示。
(c) 導軸的方向在空間中是任意的。
(d) 導軸 n 與 – n 的狀態是不可區分的。 Cholesteric 液晶Cholesteric 液晶The Chiral NematicThe Chiral Nematic Chirality ChiralityThe methyl group on the 2nd carbon atom on the alkyl chain of the molecules extends out of the plane of the paper and the hydrogen atom extends into the plane of the paper. Therefore the 2nd carbon can be thought of as a right or left handed coordinate systemSmectic 液晶Smectic 液晶 由結構上的差異Smectic液晶又可被細分成Smectic A、B、C....等共十餘種。但結構上看,所有的Smectics相都具有層狀結構,層與層之間的距離是一定的,層間距可以用X-ray繞射方法來量測。由此可見Smectics的之次序性比Nematics高。對於任何俱備此兩種相的材料
而言,其Smectic相的溫度範圍總比Nematic相為低。 null(c) Smectic C* (SmC*) 與Smectic C相似其分子導軸之方向與層面法線方向有一夾角。但相鄰之液晶層的分子導軸會沿著層面法線作緩慢之螺旋轉動,如圖所示。此結構之形成通常可由Smectic C之液晶再加入光學活性分子或
chiral agent所形成。故又名為chiral smectic C。 外加電場對 nematic 相的影響 外加電場對 nematic 相的影響 對一 nematic 相液晶外加一電場 E,其相應的電位移 D 為
此時電場對系統之能量貢獻(每 cm3)可寫5
液晶之非均向性(Anisotropic)液晶之非均向性(Anisotropic) 由於液晶分子之形狀具有高度幾何異向性[長條狀或圓盤狀],導致其分子之排列方向具有秩序性,此一異於各向同性(isotropic)液體的特性亦表現在電性、磁性、光學及力學等各方面。當量測其介電係數(dielectric constant)、磁導率(magnetic susceptibility)、折射率(refractive index)及黏滯係數(viscosity)…等時,將因液晶分子排列方向不同而有所差異。 (綱要)Outlines(綱要)Outlines簡介
˙市場
˙液晶簡介
液晶光學性質
液晶顯示器模式
Phase shift in a birefringent material Phase shift in a birefringent material Δn= ne-no>0 正單光軸
Δn= ne-no<0 負單光軸Phase retardationE-waveO-wavenullTipping the director by the angle Ө E-wave
O-waveBirefringence of LCIndex Ellipsoid: x2/no2 + y2/no2 + z2/ne2 = 1
( For an uniaxial crystal: nx=ny=no, nz= nene) =2nd/=π/245oEzExkExEykBirefringence of LC z (optical axis)yx=x’noO nenoneff ()none/(no2sin2 + ne2cos2 )1/2 =2nd/=π/2
null(綱要)Outlines(綱要)Outlines簡介
˙市場
˙液晶簡介
液晶光學性質
液晶顯示器模式
nullLC mode?nullSource: SharpLCD Modes SURVEY OF LIQUID CRYSTAL DISPLAY MODES
SURVEY OF LIQUID CRYSTAL DISPLAY MODES
Birefringence mode
Dichroic Dye mode
Scattering mode
null▬ TN , STN (Polarization Rotation )
▬ ECB-electrically controlled birefringence (or
phase retardation) – VA, IPS, HC, Chiral-VA
▬ FLC-Ferroelectric LC
▬ Mixed mode
Birefringence ModeTwisted Nematic Liquid Crystal DisplaysTwisted Nematic Liquid Crystal DisplaysA Twisting Nematic (扭曲型LCD )A Twisting Nematic (扭曲型LCD )Normally Black : P//A V=0 , Dark StateNormally White : P⊥A V=0 , transparent State
TN-LCD作法TN-LCD作法ITO- cotaed glass
Alignment layer (spin coating)
Baking
RubbibgPretilt~20避免reverse tilt
Cell thickness?
It depends on the birefringence ∆n of LC
For 900 TN-LCD between two parallel ideal polarizers (normally
Black mode), the transmission is (unpolarized monochromatic)
RubbingTransmission of TN LCDs --- NB modeTransmission of TN LCDs --- NB mode(Gooch and Tarry)Transmission of TN LCDs --- NW modeTransmission of TN LCDs --- NW modeWhere: = 2nd/
= /2(Gooch and Tarry)null∆n.d=0.48m, 1.09 m or 1.68 m
選LC ∆n已知
d可知
6.Nematic LC+少許chiral component
避免reverse twist
7.灌充即可Typical cell gap for TN LCDsTypical cell gap for TN LCDsFirst minimum condition :5 m is a typical cell gap for first minimum TN LCDsTN LCDs ---- threshold voltageTN LCDs ---- threshold voltage Using the previous equations, one can derive the redistribution of the director in a TN cell requires a threshold voltage give by For most nematic mixtures formulated for TN displays, Vth is typically around 1 V.90TN LCD (NW) T-V curve
TN LCDs ---- Contrast Ratio TN LCDs ---- Contrast Ratio→Commonly usedPerformance of TN-LCD standard productsPerformance of TN-LCD standard productsViewing angle needs to improve: will discussed laternull(2) STN: twisting angle 180o-270o
STN & TN : Twisting angle ↑ , E-O curve sharpness ↑
→ multiplexing capability ↑, but Gray scale more difficult
Multiplexing Capability : Number of multiplexing lines N vs Selection ratioMultiplexing Capability : Number of multiplexing lines N vs Selection ratioElectrically controllable birefringence (ECB) (or phase retardation mode)
VA (Vertical Alignment)Electrically controllable birefringence (ECB) (or phase retardation mode)
VA (Vertical Alignment)LC ň 投影Θ=45o Performance of MVA-LCD Fujitsu products
MVA: Multi-domain VA (wide view angle) Performance of MVA-LCD Fujitsu products
MVA: Multi-domain VA (wide view angle) IPS (In-Plane Switching) 之操作原理
(Phase retardation mode) IPS (In-Plane Switching) 之操作原理
(Phase retardation mode)Optical Switching of
Surface Stabilized Ferroelectric Liquid Crystal (SSFLC)
(Phase retardation mode)Optical Switching of
Surface Stabilized Ferroelectric Liquid Crystal (SSFLC)
(Phase retardation mode)Surface interactions can be used to unwind the spontaneous helix, which yields a uniform FLC alignment with
Fast response
Bistability
Wide viewing angle (IPS)
nullRubbing directionSSFLCs
‧Book shelf structureLC molecule2.Dichroic Dye Liquid Crystal Displays2.Dichroic Dye Liquid Crystal DisplaysDichroic dye moleculeA∥: Elight ∥ , absorb light
A⊥: Elight ⊥ , do not absorb light
Heilmeier dichroic display
Quarter wave dichroic display
Phase change dichroic display
Dichroic Ratio (DR) ,Research Topics in TFT-LCDsResearch Topics in TFT-LCDs1) 廣視角
2) 快速應答
3) 大面積製程
4) 新背光源
5) 可撓曲:類紙式
6) TFT製程及材料