Liquid Crystal DisplaysLiquid Crystal Displays

By

Farrell RogersMaterials Research Science and Engineering Center

(MRSEC)Interdisciplinary Education Group (IEG)

University of WisconsinMadison, Wisconsin

RET ProgramSummer 2006

NanoScienceNanoScienceNanoscience involves the study and creation of materials,

devices, and systems through the manipulation of individual atoms and molecules.

o Describes research where the characteristic dimension of 1 or more plane is less than about 100 nanometers(.1 micron).

o Manufactured products are made from atoms. The properties of those products depend on how those atoms are arranged.

o If we rearrange the atoms in….o coal we get diamonds or graphite. o sand (adding a few other trace elements) we get computer

chips. o dirt, water and air we can make potatoes.

Unlike their larger or “macro” counterparts, nanoparticles often display unique properties that may be of use for various applications(Rattner & Rattner, 2003).

States of MatterStates of Matter

Solid

Liquid crystal

“fourth state of matter”

Liquid

GasImages: MacDonald, R. “Liquid Crystals - Fascinating State of Matter or "Soft is beautiful". Accessed 7-2006

Liquid Crystal – a stable phase of matter characterized by anisotropic properties without the existence of a 3-dimensional crystal lattice – generally lying between the solid and isotropic (“liquid”) phase.

What is a Liquid What is a Liquid Crystal?Crystal?

IsotropicIsotropic

vs.vs.

AnisotropicAnisotropic

Liquids and gases(uniform properties in all

directions).

Liquid Crystals have orientational order

There are 2 basic phases Nematic & Smectic

Anisotrpic substances may go through one or several

Liquid Crystal Phases

Liquid Crystal PhasesLiquid Crystal Phases

Images from Sheffield Hallum University, United Kingdom, 2006

Liquid Crystal ModelLiquid Crystal Model

Phase TransitionsPhase Transitions

Molecular Expressions, NHMFL-FSU( accessed, 2006.) http://micro.magnet.fsu.edu

Project GoalsProject GoalsMy Curriculum Research Project focused

on Liquid Crystal Explaining Liquid Crystals Explaining Polarization Adapting the LCD Watch Dissection for my students

Designing a middle grade activity to create a simple LCD Panel

Activity #1Activity #1Introducing Liquid CrystalsIntroducing Liquid Crystals

After reading a brief history and description of Liquid Crystals, students will answer some questions and use drawings to compare the 4 states of matter.

I designed a questionaire for this activity.

Activity #1Activity #1Comparing Liquid CrystalsComparing Liquid Crystals

Part II: Visualizing Liquid Crystals 1-In the box below draw how the molecules of each

of the following phases might be arranged if you could see them.

Solid Phase LC Phase Liquid Gas

Activity #2Activity #2Part 1: Polarized LightPart 1: Polarized Light

This activity involved having kids explore the properties of light using 2 polarized lenses. They will compare light from an CRT TV, LCD Screen and from an incandescent bulb.

Activity #1 PicsActivity #1 Pics

Activity #2Activity #2Part 2: “To Twist or Not to Part 2: “To Twist or Not to

Twist, a Play of Polarization”Twist, a Play of Polarization”

This is a student run Demo where different kids play different roles to demonstrate the parts of a Liquid Crystal Display.

Image: How Stuff Works, 2006

Activity #3Activity #3

Adapting the LCD Watch Dissection

MRSEC/IEG already has an excellent lab for this at http://mrsec.wisc.edu/Edetc/nanolab/watch/index.html

The only thing I would add would be testing to see if Dry Ice was cold enough to solidify the LC and prevent the LCD Panel from Functioning. (Maybe Next Year? Please :o)

Activity #4Activity #4Making a Liquid Crystal Making a Liquid Crystal

DisplayDisplayEverything seems easier once you figure it out.

I had a few obstacles such as… Which LC, How much LC, How thick the spacers should be, How much voltage, Do I need an orientational polymer, How do I apply the chemicals, etc.

MaterialsMaterials5CB Liquid Crystal

ITO Conducting Glass slides

Polyvinyl Alcohol

Polarized Lenses

Capillary tube Pipettes

Binder Clamps

9V Battery

Glass Petri dishes

Hot Plate

Alligator clamps

Copper wire

Saran Wrap

Cotton Cloth

Tweezers

Q-tips

eyedropper

LCD AlignmentLCD Alignment

When coming into contact with a finely grooved surface (alignment layer), LC molecules line up parallel along groove due to their rod-like shape.

Coating ITO glass with a layer of PVA and rubbing repeatedly creates these grooves.

Sharp Technologies, Inc. 2006

Natural state

LCD OrientationLCD Orientation

The molecules along the upper plate point in direction 'a' and those along the lower plate in direction 'b,' thus forcing the liquid crystals into a twisted structural arrangement./ (figure shows a 90-degree twist) (TN type liquid crystal)

Sharp Technologies, Inc. 2006

Unique Properties of Liquid Unique Properties of Liquid CrystalsCrystals

The orientation of Liquid Crystals can be affected by…

PressureTemperatureElectrical Field

S. Palmer, LCTec Displays, Inc. 2005

LCD PreparationLCD Preparation

Checking the ITO Glass

Rubbing the PVA to create an alignment

layer

Removing the PVA at one edge

Placing the Saran Wrap Spacers

Applying the Liquid Crystal

Placing the Polarizers at 90°

The LCD SandwichThe LCD Sandwich

Modified from S. Palmer, LCTec Displays, Inc. 2005

LCD TechnologyLCD Technology

Electrical-field

NOT Applied

Light IS transmitted

Electrical-field

IS Applied

Light NOT transmitted

LCD ResultsLCD Results

Electrical-field NOT Applied

Light IS transmitted

Electrical-field IS Applied

Light NOT transmitted

LCD In ActionLCD In Action

pics\LCD13.mov

LCD ApplicationsLCD Applications

The Nematic phase is most commonly The Nematic phase is most commonly used in Liquid Crystal Displays used in Liquid Crystal Displays

(LCD)(LCD)

Prior Knowledge Prior Knowledge and Timingand Timing

LC’s can be discussed during any of the following units:

– States of Matter/Phase Changes– Properties of Light– Electricity

Possibly make it a long term activity discussing what an LC is during Matter, then doing the Watch Dissection & LCD Fabrication during the other Units?

Standards AddressedStandards AddressedScience Nature of Science

History of Science Variables and Experimentation

Chemistry Matter

Physical Science Waves Energy Electricity

Technology & Society

Language Arts Main Idea Using Context Clues

These activities would be appropriate for Science students in grades 8-12.

ReferencesReferencesReferences:1-Rudy, Lisa Jo. “Between the Boundaries of the Known

The Molecular World between Solid and Liquid”. Copyright ©2004 University of Pennsylvania. School of Arts and Sciences Updated September 1, 2004.http://www.sas.upenn.edu/sasalum/newsltr/spring04/between_boundries.htmlAccesses 6-25-20062-How Stuff Works. Building Your Own LCD. July 2006.http://electronics.howstuffworks.com/lcd4.htmAccesses 6-25-20063- The University of Wisconsin. Materials Research Science and Engineering Center (MRSEC)-Interdisciplinary Education Group (IEG)Engineering Centers Buildinghttp://mrsec.wisc.edu/Edetc/nanolab/index.htmlAccesses 6-25-20064-Ratner, M. & Ratner, D. Nanotechnology, A Gentle Introduction to the Next Big Idea, 2003. Pearson Education, Inc.5- Kent State University. Liquid Crystal Institute,http://www.lci.kent.edu/Accessed 7-6-20066- Macdonald, R., “Liquid Crystals - Fascinating State of Matter or "Soft is beautiful". Optical Institute of the Technical University of Berlin

  Straße des 17. Juni 135, 10623 Berlin, GermanyAccessed 7-6-20067-Touch Screen infohttp://www.reedlink.com/ProductInfo~Productid~142231~ProductName~Touch-Screen-Displays.htmlAccesses 7-6-20068-Universität Hamburg Liquid Crystal Databasehttp://liqcryst.chemie.uni-hamburg.de/lcionline/liqcryst/lchistory/topics/c13b5.htmlAccesses 7-6-20069-Waclawik, Eric R. “Liquid-Crystal Displays: Fabrication and Measurement of a Twisted Nemetic Liquid Crystal Cell”. Journal of Chem. Engineering 81, no.

6, (2004) 854-858.10-Ondris-Crawford, R., Crawford, G.P., and Doane, J.W. “Liquid-Crystals, Phases of the Future”. The Physics Teacher 30, Sept. (2004) 332-339.11-Sadlej-Sosnowska, Nina. “Imposed Orientation of Dye Molecules by Liquid Crystals and an Electric Field”. Journal of Chem. Ed. 57, no. 3 (1980) 223-224.12-Daigle, Stephen M.. “Investigating the Bistibility of 4’-octyl-4-Biphenylcarbonitrile”. Liquid Crystal Institute, Kent State University (July 2004).http://clcse.lci.kent.edu/students.htmAccesses 7-12-200613- Sharp Technologies, Inc1. The Principles of LCD Technologyhttp://sharp-world.com/sc/library/lcd_e/s2_1_1e.htmAccesses 7-12-2006

Thank youThank you Wendy Crone, Ph.D.: MRSEC Director of Education, University of Wisconsin Greta Zenner, Ph.D.: MRSEC Assistant Director of Education, University of

Wisconsin MRSEC-RET program Dana Horoszewski , Ph.D.: IEG Mentor Ken Gentry, Ph.D.: IEG Mentor Dr. George Lisensky, Ph.D.: IEG Mentor, Professor of Chemistry, Beloit College University of Wisconsin NSF, Research Experiences for Teachers(RET Programs)

"We are grateful to the National Science Foundation through the Materials Research Science and

Engineering Center (MRSEC) on Nanostructured Interfaces (DMR-0079983 and DMR-0520527) at the

University of Wisconsin-Madison”