Navigatin Disp

8/2/2019 Navigatin Disp

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1NAACK. 13 2 4 12

_ J ! l i l l l i l l i l l l i l l l l l l 1 1 1 1 1 1 1 1 1 1 I I I I I I I i I I I I U I I I I ! I I I I I I I I I I I I I I I I I I I I I I l I I I I I I I ! I I I I I I I I I I I I I I I I ' LDEVELGPM Nf OF VISUAL-DISPLAY

AID TO AIR NAVIWI(W

Final ReportNASA Grant NGR 39-004-038? i l l l l l l l l l i l l l l i l l l l l l l L I I I I I i l l l l h l l i l l l i l l l l l l l i i l l i l l i l l l l l l l i l l l l l l l l l l l l l i l l l i i f l l l l l l l l l l f

(NASA-CR-132412) DEVELOPMENT OF74-17385,V I S U A L - D I S P l e Y A I D TO A I R N A V I G A T I O NF i n a l R e p o r t , 1 Ja n. 1 9 72 - 3 1 M a r.1973 (Drexel Univ.) 62 p HC $3.75n c l a sCSCL 17G G3/21 31068IP tGEN ^ tVN

e>^ ^ ^ F 6 Z S Z 1 2 ^ ^ G ^


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DEVLLOPIC-M OF VISUAT,-DISPLAYA ID T O A I R N A V I G A T I O NFinal Report

NASA Grant NGt 39-004-030"1 January 1972 to 31 March 1973Submitted by

Professor T. J. MatcovichDrexel Universityhiladelphia, Pennsylvania 19104


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INDEX

1.0NTRODUCTION1.1cope of Program1.2rogram Organization1.3ummary

2.0YSTEM CONCEPTS2.1escription2.2perati.on2.3esign Criteria2.4asic Cell Configuration

2.4.1arallel Configuration2.4.2erpendicular Configuratio2.4.3oltage Sensitive Cells

3.0IQUID CRYSTAL MATERIALS3.1vailable Materials3.2uality Control3.2.1torage3.2.2urification

3.3tability Tests3.3.1ifetime-3.3.1.1srandatd Cells3.3.1.2ontrolled Ambient3.3.2ailure Analysis

3.4asic Properties3.4.1 Birefring3.4.2ensity'


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4.0 DISPLAY DESIGN P.ND FAIIRTCAXION

4.1 Display Design4.1.1. Design Considerations4.1.2 Line Design4.1.3 Materials

4.1.3.1 Substrates and Conductors4.1.3.2 Covers and Sealants4.1.3.3 Liquid Crystals

4.2 Fabrication4.2.1 Process Limitations4.2.2 Perpendicular Configuration Di splays4.2.3 P arallel Configuration Displays

5.0 ELECTRONTCS

5.1 Electronic System Design5.2 Phase Detector and Register.5.3 Driver5.4 ;Decoder

6.0 SYSTEMEVALUATION AND CONCLUSIONS

6.1 System Evaluation6.1.1 Displays6.1.2 Electronics

6.2 Conclusions

7.0 BIBLIOGP.APHY


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LIST OF FIGURES

1 . 7 . Display Panel2.1 Basic Cell Configurations3.1 Birefringence as a Function of Temperature3.' Index of Refractior as a Function of Temperature3.3 Density as a Function of Temperature^.1 General Configuration of Display Model4.2 Perpendicular Line Detail4,3 Parallel Line Detail5.1 Block Diagram of Electronic System5.2 Phase Detector and Register5.3 Phase Detector Timing Diagram5.4 Integrated Circuit Driver5.5 Driver Output Voltage5.6 Decoder Concept5.7 Decoder Circuit


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1SECTION 1INTRODUCTIOP

This report is the final report on the work perfornc ed on NASA, GrantNGR 39-004-038 at Drexel. University duri.uZ, tLe period 1 January 197: to31 March 1 973. The oLjective of the protp-am was to design, develop andfabricate a liquid-crystal, visual-display ,lid to air. navigation. Tiledisplay was to be used to locate an airc-:aft on a standard navigationalchart when activated by two independent- VOR signals. A prime considerationwas to make the display sufficiently inexpensive to encourage its widespreaduse in private as well as commercial aircraft., This work is a continuationof a program started in January 1971 .

1.1 Scope of P rogram

The scope of the-program described in this report includes the designand fabrication of the liquid crystal display, the design and fabrication ofthe electronic interface between the VOR system and the display and a studyof the stability'of the liquid crystals under operating conditions. Demon-stration models were to be fabricated from available liquid crystal materials;no attempt was to be made to sy nthesize liquid crystals; but techniques were

to be developed to purify commercially available materials.1.2 Program Organization

The work described in this report was performed at Drexel University inthe graduate research laboratories of the Physics and Electrical EngineeringDepartr,,ents including; Professor Lord's laboratory in Disque Hall; andProfessor Matcovich's microelectronics laboratory in Stratton Hall. 'Three


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1. ^iunimaA ten-by-ten inch display pane.. was designed and fabricated. Pau-Js

made from aluminum-Mylar laminates were not satisfactory due to peeling andpoor line definition. Panels made from copper--Kapton laminates in theparallel line configuration geoir:^try were not satisfactory due to Kaptonresidue left in the Kapton chanrals. Panels made from copper-Kapton lami.neresin the p erpendicular line configuration geometry were satisfactory and wereused extensively in this report period.

Lifetime studies on liquid crystals were continued and extended toinclude newly available liquid crystals and testing in controlled ambients.These tests indicate that lifetimes in excess of one year are possible. Amethod for purifying liquid crystals and improved quality control techniqueswere developed.

Voltage sensitive cells were made and tested, but they do not appearto be practical for the present application.

The electronic system was designed and fabricated. A practical phasedetector and encoder was fabricated and tested, An integrated circuitdriver was designed and fabricated, but severe problems developed when itwas used to 0-4ve display cells; the cells failed after short periods ofoperation. Extensive effort was made to solve this problem, ,but it was notfully resolved even at the end of the ,program. Tests' made near the end ofthe program indicated that DC operation may be practical. A simple decoder-driver was designed based on DC operation,

A paper, "A Large, Flexible, Liquid Crystal Display Cell" was presented


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New York City. A paper, "Variation of DC Dowain Threshol& i,r- Nernatic LiquidCrystal under Continual Dynamic Scattering" was published in the Journal ofApplied Physics, Vol. 44, No, 1, January 1973 . Both papers are based on workperformed under this program during the current report period.


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4

SECTION 2

SY STEM CONCEPT-'

2.1 Description.

The navigational aid comprises two, ten-by-ten inch, ttanzparent,flexible, display panels and interface electronics for converting VOR datato directional data f or the displays. A display pane]., shown in Figure 1.1,comprises a radial pattern of electrically conductive line pairs, liquidcrystal material contained betwee.l the line pairs, and aduressing andactivating electronics.The interface electronics comprises -a pbasrdetector, encoder, register, decoder and driver.2.2 Operation

In operation two displays would be placed on a "standard navigational,chart and centered on a ppropriate VOR station locations. The directionaldata from each station would be detected and encoded and sent to the displaypanels. The panel electronics would decode the signal a nd activate theradial line most closely approximating the aircraft direction from the VORstation. The activated line would turn a "mil ky-w hite" and would be clearlydistinguishable from unselected lines. The intersection of the selected

lines on the two panels would indicate tha a ircraft's location on he chart.2.3 Design Criteria

A Drime objective of the program was to make the navigational aidsufficiently inexpensive to encourage its use in private as well as commercialaircraft. .Consequently standard integrated circuits were to be used;, thedisplay was to be integrated circuit compatible and the display itself was


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sto be inexpensive. As reported in the first annual report, the intra-

electrode spacing required in a parallel configuration cell. is 12p.Maintaining this spacing over a ten-by-tea inch square would be verydifficult if rigid electrodes were used. Consequontl.y, only flexibleelectrode materials were considered for the displays.

Since many lines were to be used on the display, the connector waspotentially a high 'cost comp


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Gone of the conductive electrodes used in this co.xfiguraticn must be

transparent. If the dynam?.c scattering phonontcnon L$ to be observed byreflected light, the back electrode should be highly r.eflective,- Tf thephenomenon is to be observed by trausmi.ttea light both electrodes musL betransparent. The optical pith length, d, is related to the electric field,L, through the relationship: E = V!d w here V is the applied voltage.

2.4.2 Perpendicular Configuration

In the perpendicular configuration shown in F igure 2.1 b the directioaof the incident light is essentially perpendicular to the cicctri.c field.In this configuration ,transparent electrodes are rot re q uired and Ua opticalpath length is independent of the electrode spacing. A highly reflectingsurface must be placed in the light beam if scattering is to be observed byreflected light.

2.4.3 Voltage Sensitive CellsInvestigations were made into utiliza.ag a recently reported eler.tro-

optic effect in nematic liquid crystals possessing positive dielectricanisotropy. This effect makes use n)f, a twisted nematic structue to providea 90 phase rotation of light passing through a thin cell Thv twistedstructure is achieved by rubbing the transparent electrodes so that thenematic molecules align along the electrodes in the direction of "nabbing.The cell is made by orienting electrodes with their alignment directionsperpendicular. The directrix of the medium then continuously rotates 900from one electrode to the other. If the cell is placed between alignedpolarizers such that one of the polarizers is oriented at 90 to the moleculadirection of its adjacent electrode, the cell then appears dark in transmitte


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light. If a voltage is applied Lo the electrodes, the rol.cculer: alifn.parallel to the. field, that is in the dirt+cti.on of light propagation. Th,^light in the cell now travels along the optic axis of the medium andexperience- no optical rotation; hence, the light is freely transm.la cd bythe alignad polarizers. This effect requires a lower voltage than dynamicscattering. In the several 1211 thick cells made, a voltage of 5 volts ACor DC provided a striking physiologi.c:al contrast ratio. It was noted,however, that this effect was very sensitive to the surface preparation ofthe Nesa electrodes and it was difficult to get a uniform orientation overthe entire electrode. Cells made from mylar electrodes with an evaporatedmetallic coating were not as functional as the mylar substrate is itselfoptically active, and interferes with the operation of the cell. Miile thiseffect provides goo6 light valve operation at low voltages, the difficultierinvolved in treating the flexible ,electrodes and maintaining the properorientation p recludes its use in the present application,


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LC'TTON 3

L1 1111) CRYSTAL IIATT RIALS3.1vailable M - i t , ! r i . a l sNematic type liquid crystals mere used in this program, Tlicsematerials, which are norcally transparent, become, milhy-- 1 ,1 11ILc ri : a fieldis aa?pliad due to the "dynamic scattering" of the incident lighL. Severalcompanies supply nematic liquid crystals on a commercial basis. hostavailable nematics are in the liquid crystal stale at temperatures above thenormal ambient; however, several are available which function at room temper-ature. These are listed together with the suppliers in A ppundix A.

3.2 . Qual.i tyControl

The quality of the liquid crystal is significantly affected by absorbedwater and gases and by.exposure to ultraviolet radiation.he effect is due-, decomposition of the liquid crystal and can occur in storage or operation.

;-lost commercial materails are reasonably pure when received, but quicklyabsorb water and gases.

The nematic-isotropic transition temperature is a convenient andaccurate measure of crystal quality.ecomposition products and dissolvedgases lower the degree of nematic order and so the transition temperature.Test results on fabricated cells indicate that the liquid crystal. transitiontemperature must be within a few degrees of its theoretical value to achievesatisfactory device operation.

Two procedures were initiated during this phase of the program toimprove the, I quality of the liquid crystals.hey are described in the


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3.2.1 StorageIn the initial ph ase of the contract the li q uid c rystal materials were

stored at roori temperature. When the transition temperature m'


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31LfeLuie

3.3.1.1. Standard Cells

The longest-lived crystal. was Merck Licristal. IV; thelongest--lived electrodes were Nesa and Nesatron glass. The most stablemetal film electrodes were those made frontell lifetimes werecomparable to those made from Ness, and Nesatron glass. Several c ells haveexceeded 589 days of continuous AC operation.

3.3.1.2 Controlled Ambient

Since liquid c_ystals are knoem to degrade when exposed tonormal aribients and ultraviolet light, lifetime tests were made on samplesheld in dry nitrogen atmospheres and shielded from light. The dry nitrogenatmosphere can be approximated in displays by hermetically sealing the celland the light shield can be approximated by use of ultraviolet filters.Since long lifetimes were expected, the cells were operated with DC excita-tion. Previo-ts tests indi cate that failure under DC operation is much morerapid than under AC ilperation Test cells were made from Varilight 1047liquid crystal and Pesa glass in the standard configuration. Cells placedin the protected ambient continued to operate after 34 weeks, of continuousDC excitation. Similar cells in the normal laboratory ambient failed afterone week of continuous DC excitation.

3.3.2 Failure AnalysisCells: made with evaporated thin metal films had a large izumber of

electrode failures. Lifetimes of these cells did not app.ar to be a measureof liquid crystal stability but rather a measure of the stability of the thin


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films. The copper electrodes used in the tests made since January 1972 we eevaporated on glass over a thin layer of chrominum to improve continuity andadhesion. Ralf of the failures in copper-electrode cells occurred in thearea where the electrode was exposed to the air.

A distinct interaction was observed between Eastman Mixture No. 11 643liquid crystal and copper and aluminum electrodes. All failures in nickelcells occurred in the region exposed to air. Half: of tko electrode failuresin silver cells occurred in the part exposed to air. Failure in cells with

gold electrodes all occurred through the liquid crystal with subsequentburning of the material; the apparent cause was local peeling of the gold.

3.4asic Properties3.4.1irefringenceThe contrast ratio obtainable in a nemaiic liquid crystal device isprimarily dependent on the optical anisotropy of theliquid crystal.heoust measurement of this anisotropy is the birefringe nce of the crystal.;consequently, -,h_ study of birefringence iniciated in the first phase ofthis program was continued in the second phase.

The birefriagence was measured by use of a wedge interferencetechnique.he wedge was placed in an electrically heated oven to providetemperature 'control and the antire assembly was placed on amicroscope stage.

The wedge was illuminated .by,a C,5 m w -He-Ne laser polarized at anangle of45 to the optic axis (molecular direction) of the rematic medium so thatthe components of the Cream perpendicula r and parallel to the optic axis areof equal. amplitude., each of these components travels through the medium

A


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with a differeuL index of refraction, for certain path lengths in the wedge,destructive interference will occur between the two component waves and aseries of eque.;.ly spaced dark fringes is seen in t l ^e wedge. An eyepiece isused to measure fringe spacing as a function of tetil:ecature. The birefrin-gence, ne - no, can be computed through the relation:

n e - no = ax cote

whera a is the wavelength of the illumination, Ox, the fringe spacing and a,the apex angle of the wedge. Figure 3.1 gives the birefringence as a functionof temperature for all the commercially available room temperature nema ticmaterials.

although liquid crystals are birefringent, their uniaxial nature makesit possible to measure the ordinary index of refraction, no, of an unor ientedsample by using a standard Abbe refractometer. The refractometer used hadprovisions for altering the temperature. Thus no was maasured as a functionof temperature,'in the same temperature interval as n e - no. Hence the valuesof both n o and n e as a function of temperature have been obtained. A subse-quent analysis of these data (along with the density measurements reportedin 3.4.2 ) will be made to test a recently proposed model' for the interactionof nematogenic molecules.

3.4.2 Density

A basic factor involved in the interactions that cause the orienting ofnematic molecules is the density of the material. t , 'lso;, the discontinuity in

1"Theory of Birefringence of Nematic Liquid Crystals," S.,^',handrasakhar,D. Kirshnamurti and N.V. Madhusudana, Molecular Crystals and LiquidCrystals, 8, 45-49 (1969).


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the e:: ansion of a sample. of li. uioystal u,tdergoin^ rui


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3 . 4

6ECTION 4DISPLAY DHSIGN A?ZD FAP,RICATION

4.1 Dis lay Design

The layout of the display, shown in Figure 4.1, has not changedappreciably from that described in the 1971 annual report. The act ive areaof the d isplay is nine inches in diameter and contains 36 l ines spaced 10apart. A ttempts were made to fabricate each of the basic cell configurationsdescribed in Section 2.4; the perpendicular configuration proved to be more

practical, but neither was fully satisfactory.4.1.1 Design Considerations

The d esign criteria to insure visibility were established in the firstphase and presented in the first annual report. The lines were to be 30 to40 mils wide and opa que. These lines Caere wide enough to be visible when,activated yet not so wide as to obscure information on the chart. T he

selected line was to be pulsed t o improve visibility and a reflective linebacking was to be used to improv e contrast.

To insure reasonable lifetime, the liquid crystal cell should behermetically sealed and should not co me in contact with the sealants orother adhesives. Excitation should be AC although recent data suggest DCcan be used (Section 3.3.1.2) if a protective ambient is provided. Firstphase data indicate operation should be in the '0-to 60 Hz range and 60 Hzwas chosen for convenience.

4.1.2 Line Designs

The preferred; perpendicular line design is shown in Figure 4.2. Thease is Mylar coated on both sides with aluminum. Th e back side aluminum is


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etched to the overall Line width to provide a reflective backing and thefront side aluminum is etched into the line pattern shown in the Figure.Aluminum metallization is preferred because of its stability in contactwith the liquid crystal (Section 3.3.1..1) and because it is a good reflector.Mylar is preferred because of its transparetiey and color (water--white). Themylar cover is coated to minimize reflections. The aluminum spacer isinten-led to keep the cover out of contact Nitth the liquid crystal.. The coverwould be sealed along the outer edge only, to prevent contact of the liquidcrystal with the sealant.

The preferred parallel line design is shown in Figure 4.3. The useof copper and Raptor reflects feotication problems. The substrate must beetched and techniques for etching Kap;.on were available. Although mylaretching processes were reported, the processing procedure could not bedetermined.

4.1.3 Materials

4.1.3.1 Substrates and Conductors

Metal-plastic laminates can be made in a large variety ofmaterials and thicknesses. Unfortunately procuring these materials inreasonable quantities was very difficult. Of the many m2'2erials sought,the following were the only materials received:

1. Kapton substrate two mils thick, coated with i oz. copper fromthe Fortlin Company.

[. Mylar substrate two ml - Is thick, coated on one side with 1 $ oz.copper and the other with ;I mil thick aluminum from TME Company.


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. Mylar subol.rate two mils Lhicl_, coated ou one silo criLh ? rail.thick sluminma audon the other with two mil dAck nl.Orainura iro,tTIE Company.

4. Transparent gold-coated, flexible plastic from Liberty GlassCompany.

5. Transparent silver-coated, flexible plastic from DuPont.

The Kapton laminate was m ade without adhesive between the copperand the KapLon. The Kapton was transparent, but had a distinct yellow color.The Mylar laminates ware m ade with a Tlylar typ e adhesive between the layers.This adhesive should have no more effect or, the. liquid crystal than the Mylarsubstrate. The Mylar was transparent and hater-wiii.te.

4.1.3.2 Covers and Seala*rts

An an tireflection coated tlexi.ble, transparent palastic materialwas obtain-d from Optical Coaling Laboratory,, Inc. for use as a cover materialfor the perpendicular cell displays. Two sealing naterials, PTV 732 andRTV738 were obtaiT^ad from Dow Corning Comp any for use in sealing the coversoverthe liquid crystal cells.

4,2 Fabrication

The display panels were fabricated by Towne Laboratories of Somerville,New Jersey, Etching techniques were developed an d evaluated at Drexel (seefirst annual report), however, the display panels were too large to befabricated in the equipment available at Drexel.

4.2.1 Process Limitations

All attempts to fabricate display panels with aluminum electrodes failed.The samples obtained had poor line definition and poor adhesion of conductor to


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substrate. The etching of fine line patterns of Lhe requi.re.d dim_ni5lor.;; inalunlnur is within tho state-of-the-arL; however, the starting; materials ru^.tbe smooth, uniform and strongly adherent-. Suitable materials could not beobtained from the suppliers since the quantities involved were small and pro-jected use uncertain. Delivery times on laminates averaged well over twomonths.

Good quality perpendicula37 geometry displays made from copper-Kaptonlaminates were obtained and used to fabricate models. The parallel geometry

displays made front the copper-Kapton laminates had good line definition, butwere defective in that considerable Kapton residue was left in the bottom ofthe Kapton channels.

4.2.2 Perpendicular Configuration Displays

The perpendicular line configuration is shown in Figure 4.2. Becauseof the long narrow geometry the liquid crystal was inserted in the line

before the cover was attached. The total. volume to be filled is less thanone microliter. Care was taken to keep the liquid crystal from the seal areaor a good seal could not be made. To accomplish the filling, a five micro-liter capacity syringe was used. The syringe had a Teflon plunger, a hollowplatinum needle and a final Teflon filter. The syringe was mounted onaprojection microscope equipped with a 40 power lens. The microscope wasenclosed in a clean hood. The lines were filled.by use of the syringe whilethey were observed on the projection screen. The liquid crystal was purifiedand its transition temperature was measured prior to use. No difficulty wasexperienced in filling the lines or keeping the seal area clean. The coversin the original models were attached by use of double sided masking tape.


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Because of the a?iffic.ul.t:ies with Cot- elece;uou cs (section 5.3) only a fi rsamples were made whic3, urire sealed with x'i'V c0, apow10.

4.2.3 Parallel Configuration Disp lays

T he p arallel configuration ce ll is shown i n F igure 4.3. T he cov er oft h e p a r a l l e l c e l l m u s t be e l e c t r i c a l l y c o n d u c t i ve a n d t r a u s p a r c a t a n d i t sconductive side must- come_ in conta ct with the liquid crystal. Two coverm aterials were obtained ; a gold coate d p a; :ic fro m L iberty Glass an d asilver coated plastic from DuPont.

Two p roblem s are encountere d in fabricating this cell. One was re m ov in;;the Kap ton fro m the channel; the other was sealing the cell. Since the chan-n e l i s f o u r i n c h e s l o n g , 0 . 0 1 5 . i n c h w i d e a n d o n l y 0 . 0 0 0 5 i n c h i n d e p t h ,filling the channel after capping was impractical.. On the other, hand whent h e c o ve r w a s p l a c e d o ve r t h e c h a n n e l a f t e r i t w a s f i l l e d , t h e l i q u i d c r y s t a lwas drawn into the cover seal area by capillary action and the cover could not beseale d . T o elim inate this p roblem , a cool ing p late was built so that thaliquid crystal could be frozen while the cov,rr was installed. The coolingplate was placed in a dry nitrogen box to p':event condensation of water vaporwhen the sa m p le was coole d . Sev eral cells were fabricated an d m echanicallystrong seals were made. However, the cells were Gaither inoperative or operatedov er sm all areas only. E x am ination showe d that the channels ha d Kap tonr e s i d u e s a t t h e bo t t o m o f t h e c h a n n e l s a n d t h a t t h e c o n d u c t o r s o n t h e p l a s t i cp e e l e d . At t e m p t s t o c l e a r t h e bo t t o m o f t h e . c h a n r . e l w e r e u n s u c c e s s f u l a n d n oother trans p arent con d uctiv e p lastics were av ailable. Because of these

- d i f f i c u l t i e s u s e o f t h i s c o n f i g u ra t i o n w a s d i s c o n t i n u e d .


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SMJO :r' 5ELMTRONICS

5.1lectronic S stem Dcsi


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2 0be a logical. zero In that case; if the t y ro flip-flops u.e+ in the 6:u,,L,1r:1Lstates, the output of G will br a lot*ical. one. It follows than that Lhcephase lag of f 9 with respect to fl is indicated by the duration of a lo,ic-A.one at the output of the EXCLUSIVE-OR gate. If the output is a l o t ; i e n l . o n ( ;for the entire period of fl the phase lag is 360 0 . A shorter output pulserepresents a proportionally smaller phase difference. This is il.lustraLed inthe timing diagram (Figure 5.3) which shows that the output of C3 is a Logical"1" for 120 0 . The output o f the EXCLUSIVE-OR gate serves as a clock input tothe JK flip-flop FF3.

The phase difference is modulated using A'AND gate Gi l and the timingoscillator f t . The output of G i l oscillates between logical "0" and "1" atthe rate of f t only when output of. G 3 and the C output of binary FF 3 arelogical "l"'s. Since FF 3 divides the frequency of f? by two, the pulse burstat the output of G i l occurs once for each two input cycles as shown in Figure5.3. The number of pulses in each -irst is proportional to the phase dif-ference between fl and f2. The timing oscillator is set at a frequency of

10.5 Kllz so that each pulse in a burst corresponds to one degree of phasedifference between the signals fl and f2.

'the number of pulses is counted by the three r l.acode counters D1, D2 andD3. The counter Al divides t1he number of YnComing }wises by a factor of ten.The counters Dz and D3 provide a 'bi nary-coded-;,idecimal count of the t)hasedifference. The registers LAI and LA2 are used to store this informationat the end of counting cycle. The output of the registers is altered only ifthe phase difference between fl and f.2 changes.

The setting and resetting of the decodecounters is accomplished bya two stage counter made of an EXCLUS IVE -OR gate and flip-flops FFy and FF5.


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These two flip-dope love tl:e:ir .1 and is irpuLs Lied to tluv output C ofFF S -- the output of the NOR bate C7 serves as ::Ire clod: inpui . Tile decodccounters ll l ,DZ and D 3 are reset if both flip--flop:; FI' 4 and Fry are inlog-Leal one state. The registers are controlled by the output Q2 of F i 51 an dthe output C of ITS.

The system was fabricated from TTL integrated - , ircuits. The circuitsused were: Texas Instruments Nos. SN741011, SN7451V , SN7472N, SN,74731a,SN749ON and Fairchild No. 9308. The SN74ION is a triple input NAND gate;

The: SN745IN is a dual, 2 wide, I input- AND-OR-INVERT circuit; the S1,17472Nis a S-K master-slave flip-flop; t he SN749ON is a decade counter and the9308 is a dual 4 bit latch. T'ne system was tested by Inserting sfmulate^:VOR signals and observing the stale of the r-gi.sters as a function of thephase difference of the input s ignals. The system operated sat-isfactority.

5.3riverThe driver used originally to drive the perpen dicular configuration

display comprised a variac, a relay ,sand a step-up transformer. The relay waused to provide the p ulsed operation and the primary source of power was the60 Hz mains. The driving voltage required for good contrast ranged from 100to 200 volts.

An integrated circuit equivalent of this driver was built around theDionics D1207N decoder and driver. This unit is rated at 225 volt maximumreverse bias. The circuit diagram for the integrated circuit driver is shoin Figure 5.4. Two square wave gereraters are used: generator I operatesat 1.5 Hz and generator II at 60 Hz. During half the 1.5 Hz cycle the


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transistor^ in the i)ioni.cei units ar k . Cr:rr. d of; and poiaLs A and Bat voltegc, V. During the othc.r h:+.i.f eyel.c the train^ 'A ors are aatcro io}turnedonand off at 60 llz produciug the voltage woveforrs a A and 1; s1u.,iin Figure 5.5. In operation,he liquid crystal cell is connected beo% c aA and B as shoran in Figure 5.5. A typical cell has am":rLrcd capPcit,trcc of6.2 pf at 60 f tz and a resistance of abouL 30 1 1.The driver circuit was f brical:cd and tested. 14hen a dur;ay resie:tmxceload was used to simulate the ccl.l the driver operated satisfactorily. Wlie:i

an operational cell was connected, the cell functioned f or n short period oftime and then failed. The failure mode was determined i;,7 bc+ a drop in cellresistance from many meguhms to a fcw oluas. Sim,.ilr,r cells operated un therelay - vriac type driver did not f ail.

Initially the failures were attributed to dirt in the liquid crystalwhich caused bridging under the influence of the high f :ir.lds. Such bridgeswould also be formed when the relay driver was used, but they wostld beburnt-out by large surges of current from the driver. Such surges could

not be obtained from the integrated driver. This theory was supported bythe following experiments. When newly fabricated calls were connected tothe relay driver and the v oltage was slowly increased some cells burned out;others shooed a large vari._-tion in resistance and then stabilized at 15 to30 megohm s. Stabilized cells could be driven by the integrated circuitdriver for periods of two weeks w ithout failure.

As a consequence of the above lata, elabor ate precautions were takento keep the liquid crystal clean, for example the use of a final Teflon filtern the filling syringe as reported in Section 4.2.2, When the carefully pre-ared cells became available and were tested there was no improvement ofperformance.


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MeaSurem^ilL of ce11 resistance and c +p..clturnce were mile to daterr.%if long RC ti:, -_ constsnL-s could lte influencing the uperating corliLions.L-veral models were proposed, but the lonW^st RC time constant obtalued inany model. was less than a mi.11isr coed which is short compared to all. thedriving .frequcncics.4The most recent theory is that the failures are due to dielectricbreakdown. I FJhcn operated at 150 volts the driver produces a field of30,000 volts/cm. Liquid crystals in parallel cells were subjected to fieldsin excess of 80,000 volts/cm and there was no indication of breakdown.However, in tha perpendicular configuration cell the etched lines can con-tain nu...,.rouc sharp p.o3act 4 ons w hich wool- serve t., i..tcusify the localfield perhaps to Lhe extent that local breakdowns occur. If this is t hecase, low conductance bridges would be formed by the breacdo5m currentswhich would be externally limited by the integrated circuit driver.

It was found in the course of these sftidies, that a cell could bedriven from a 60 V DC source if one terminal of the cell is grounded. Thecell could be pulsed at a 1 .5 Ilz rate and the visibility was comparable tothat obtained on the relay driver at higher voltages. A cell was driven inthis manner for two weeks without change in contrast or resistance. It wasthen connected to the integrated circuit driver and it failed in ten hoursof operation.

Operation on DC was not considered earlier because of anticipatedlifetime problems; however, the recent lifetime data suggest that DC operationnay be practical. The first program phase data show chat a given con trastratio can be achieved at much lower voltage operation on DC than thatrequired for operation at 60 Hz.


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.4 Decoder

The decoder design was delayed in anticipation of a solutiot, to thedriver problem. When op eraLion on a 60 V DC source was demonstrated, adecod,!r was designed based on the use of that type of drive. the decodingand drive arrangement for three lines is shown in Figure 5.6. To turn aparticular display line on, the corresponding switch must be turned on toprovide a current path between the voltage source and the ground. In theoff state these switches must withstand the 60 V DC supply voltage, have aleakage current of l ess than 1,OGG picoamps and resistance (R

o f f)-of the

order of 1.0 1 2 ohms. Commercially available MOS switches, for instance SolidState Scientific, Inc. SCL4016A, satisfy the imposed requirements on theleakage currents and the magnitude of Roff but are incapable of switching60 volts. Thus the prop osed selection system is not realizable with today'soff-the-shelves devices. Since Dionics can make a driver, that has a reversevoltage limit of 225 volts, suitable drivers should be technically feasible.

The arrangement- of the' = -omplete selection system for 36 lines is shornin Figure 5.7. Except for t he switches all components are commerciallyavailable. The 36 li,-^s are arranged in four sets, three of ten lines andone of six lines. The data in register LA 2 is decoded and used to connectthe voltage source to one of the four sets, The data in register LA 1 isdecoded and used to short one of the sets of ten lines (0 to 9) in the verticalcolumns. only one line will be connected bot h to the suppl y and to ground andso only one line will be selected. Pul sed operation can be achieved by use ofthe 3 to 5 Hz driving circuits shorn to the right of the Dionics TransistorArray:


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25

A total of nine pin:, is rcquirefI on the display panel connector:`r address signals, one for the dri ving voltage, one for the pulsing siacl.

t

and one for ground. 13

1


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i

7. 6

SUTIUii 6SYPT I 'K IMJIU!'PTUii AM) CU't f.IlS?f its

6.1 S stem Evaluation

6.1.1 Display t

i3

3

s

The display comprised a tcn-by-tea inch, flexible array of radiallines. Two designs for the radial lines were considered: parallel r_ndperpendicular configurations.

The parallel configuration line geometry was simpler but severefabrication and material. problems were encountered. lapto p free channelscould not be fabricated , -in the large displays although smaller samplescould be fabricated by exe:cisin careful process control. Flexible,transparent, conductive materials for use as electrodes were obtained, butthe conductive coating was not stable in the presenr_e of the liquid crystaland practical operating cells could not be made.

Voltage and visibility considerations led to the design of a multiple,fine-line pattern for the perpendicular, configuration lines. Suitable dis-play patterns were fabricated from copper-I:apton laminates, but attempts to

s

fabricate displays from the preferred aluminum-Mylar laminates were frus-trated by materials problems. The materials problems included quality andavailability. These problems could probably be solved if large volume pro-

duction was anticipated, but the extended fine line pattern required wouldprobably result in low yields and cons^aGucnt high cost.

Simulated operation of liquid crystal cells indicated that the longterra stability of the liquid crystal cell would be adequate if the liquidcrystal were maintained in a protective ambient.. Operation on DC may evert


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27

pracii.cal. UnfertunaC_ly, sealed di-o play cell units did not becom_ avz al:d leuntil the end of Lhc program, aad lifeti.n,e tests on these cells could not b ecom p leted. Lifcti.mes i.n excess of one year are anticipated.

6.1.2 Electronics

Th y electronic system comprised a phase detector, an encoder, a driver'and a decoder. The driver at:d decoder were to be contained on the displryand as a consequence only nine connections had to be made to the 36-linedisplay.

A practical phase detector and encoder was developed but serious problem:were encountered with the integrated circuit drives.. These problems resultedin substantial delays and precluded completion of a fully operational displaymodel. These problems were not fully resolved even at the end of the program.Indications at the end of the program that a DCdrive could be used led to thedesign of a very simple drive and decode system. The decoder canno t_ be imple-mented until a 60 V PET switch becomes available, but all other components arecommercially available integrated circuits. [Then a suitable switch becomesavailable and if DCoperation is feasible, then the proposed designs representa simple and practical electronic interface system.

6.2 Conclusions

A navigational aid of the type proposed is technically feasiblealthoughsome problems must still be solved. However, the projected low _cost for thesystem does appear attainable in the near future. Unless a need for a h ighpriced system of th! type develops, additional wo rk in this area does notappear appropriate.

9


34/62

W ,

Slita.ix l_

.;.x.....l;Lli . : l 1 . rev L.

1. "D a i11e SCa..wf7.n^C A r..'_,. I'.1C it rO^C.p L1C E ffect in fCrt S.lhWa..resf VannCic Ligri.d. Crystals.," Hei1t.alor, 7,manni zrdBarto,, Procaedinon IEEE, Vol. 56, No. 7, p. 1162 ( JuIT 1551).

2. "Note on Trcd,si-_n r Cur_ent Heasurc-:t m in Liquid Cryst'ols abdRelated Sy .,tcs ; u ]hil:.ei.cr and I;ey . .n, Physical P,i


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29

1 . 5 .APP ) A L - d' 0 t J ' , n 3 ,ol.,. : o .,, .3231470) .

16. "Rcvcroib)rrysu"lls", l l a r , . Y u ; 7 i l ,N 1 110Yn , Y O L I - i 2 ,, 1 1 1 3 1 - C d 1 ' h 11 % 3 : ! co T^Uers ,ol.. 7 ,o., p .1(1970).17. "Dynzimic Scnttc^cl.-n Poon-Til,fj,i e , :atic Liquid Crystal, "Derrick J011 1 7 , LljLla Cref,-,h Lnfl Sun LL, Appliod Physics Letta;:c.;,Vol. 16, No. 2, p. 61 (IM).18. "Electrical Field D1.1-t ribution Associated wi-th Dyn amic Sc,'ItLerinl,in Ncmatic Liquid Crystals, " Sua Lu and De rrick Jon s, AppliadPhysics Letters, Vol..6, No.12, p. 4841969).

19. "Elcetrophotographic Iioa--iiig wish Cholesteric LiquidHaas and Adr:as, Applied Optics, Vol., No. 6, p. 1203 (1963).20. "Electric Field Hysterisi- Eff ects in Ch olestr-xic Liquid Crystals,"

alamed and Rubin, Applied Physics Letters, Vol.6, No., p. 149(1969).21. "Voltage In duced Vorticity an d Optical Focusing in Liqu i d Crystals,"Penz , Physical Review Letters, Vol.' . , 1 7. 0 .5,..405 (1970).22. "New Electro Optic Effect in a Roojp . Tesiperature Keiaatic Liquid

Crystals," Haas, Adams and Elannary , Physical Review Letters,Vol.5, No. 19, p.3251970).

23. "Temperature Dapendence of Ti-efringence in Liquid Crystals,Balzaini, Physical Review Letters, p. 914 (October 1970).

24 . "Hydrodynamic Instabilities in I T eniatic Liquids Under AC ElectricFields," Orsay Liquid Crystal Group, Physical Review Letters,Vol. 25, p. 1642 (December 1970).25. "Experim


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30

29. C i - 3 - U , : , L l - ) r'f-",1!ir,IDp.22971).

30. "Li , . h t S c n t t - , 1 1 7 1 1 , 11' it, lloutciC IiUld,!;Icun P;! -tj,-, Llqv AG o o 6 ^ i e i n ,ID,.24, f . : y471).31. "Trar.rinnL Sca.ttcrin" of bight. by PvJ,ri-d Liquid Cry,.:talL.S.o3ent^nn,I D ,) .26:day 1971).

32 . "MOS Dr,tra Liquid Cry- ,tal Din p l-:y ," boscIl and Robert, SI D ,).2 b(Any 1971).

33. "Cholesti:,c 1 ' . L , wi Lic Pho ie Trviisition P l q p I n y s , " 1 ;,'YsoL1 -J .,-tI,TD,p .. 3 01 , 11%y 1971).

34. "Nematic Liquid Crystals -- C1r,-.-,-,iccro-,raph y of E Icctro1iydicdyn.-.;-.5.cInstobilitios," Kashi iM.7,I D ,.3 1 11 lli y 1971).

35. "GIILSL 110SL TnLerzctlonr; in 1,(-,ia17Ic Liquid Crystals -- A Nr-w 1"IcetroOptic E ffect," 11cilTieJarnrl L. A.z n on i, Ap p l ied P h ys ic Lz-ttcrs,Vol.3,o., - p .119680).

36 . "Solid Facts abou Liquid Crystals," R. A.oraf, Laser Focus, 1 ) . 45(September 1970).

37. "Now That th e Heat Is Off, Liquid Cryrt,, J- Can Show Their ColorsEverywhere," Joseph Castellano, Electronics,July 6, 3.970).

38 . "EloctrohydLudynEmic ln;;tabilities in rietnatic Liquid Crystals,"W. 11. Dejeu, C. J. Gerrlt8ma and Van Boater, Physics Letters,Vol.4A, No., p .038 March 1 . 9 7 1 ) .39. "Performance Characteristics of Nematic L iquid Crystal Display Devices,"L.T. Creagh, A.R. Kinetz, and R.A. Re ynolds, IEEE Trans. on ElectronDevices, Vol ED-18, No., pp. 672-67 .5,September 1971).

40. "Deformation of Nemati c Liquid Cry stals with Vertical Orientation inElectric Fields," M.F. Schickel and K. Fahrenschon tAppl. Phys. Letters,Vol. 19, pp . 391-393,1971) .

-414 "Effects of Additions of Cholesterics on Nematic Liquid Crystal ProDer-ties," B. Kerllenevich and A. Coche, J. Appl. Phys., Vol. 42, p p . 5313 -5 3 1 5 ,1971) .

42. "Electrically Controlable Domains i n Vematia Liquid Cry stals," W. Crenbeland V. Wolff, Appl. Phys. Letters, Vol. 19, pp. 213215 (1971).43. "Effects of Dopant on Display Characteristics of the Ncnatic 4-Nethoxy-benzylidence-4-Buttaniliiia," Linda T. Creagh and Allan R. Kinatz,

Meeting Abstracts-ACS Meetint, Wash., D.C.September 1971).44. "Dielectric and Ra5istivity Measurements on Rodv, ,-jTemperature Nematic 1-1BBA,F. Rondelez, D. Diquat, and G. Durand, Mal. Cryst. and Liq. Cryst.1Vol. 15, pp. 183-188 (1971) .


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31

45. "Vole. v:1-100W w TcPl AILTHry vF aWOW ,7 tie MqakdM, tcL .:,- v rJ Q UO Wch, A p p ! 1 _ , t P L Y . i ns Wters, kol. IC, I P027-17

46. Watra3lo? D i retr Mawas of Thfa OnOic YMQS.A. Som'.and N.J. RUFUIS, jonryal Ur A PP IRGphysins, Vol, 43,47. Mwory 07 hire ftine ymne of Lowtic Liquid Cr,o t ai n , " S .

D.Kr., shamIUM, mu" V-TMadbunvI p Hr, Nb laculayrywtn3s and U j ab -Crystals,ol., pp.43-69(1569).40. "OriontrOanol OrM in p-Mcryo"U " le, p-Axamsphtpunin nnd TWO Plaw-w

in th e NOWIc Phan," S. ChnadrancWx nad N.V. MhubuUnn, journ%i :Physicque, Vol,0 ,,.i. C4-24 (!(Mg).

49. On the Hnnsurewnt of HMOs oF HOrretino of Famntic Liquids,"T. HOW, H,A. 1% Inn ;W W. 'hwWr, Mccular Qrscris khd Lijul'iCanals, Vol, 16, no.53-59(1972).50. A,P,. Lord, Jr., I T.1trnnonic Invantiqotfon ov t ho C h o i e c t e r i c - r eap t i c

be published in ^foj-j - : i - j j e- r C r v it nI Fpp ATl p vi eCrvntvjS.t o


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Vari-Lig ht Corpornt- o n - io - 470C uTnA7i.y9770 Crolklin Road !Q - 47C I8J111i (P urified)Cinclnnaiti, OhioFM Laboratories 16 - 74C Merc k, L icri s tal IV500 Bl:ocutivc Avenue -5 - 75`c M erc k, L icri s tal VElmsford, New York


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tuntuû A /Z2 ~ 4/-5/72 3 6 3,8 rlcCc fiil^dD U D 1 3/20/72 - 5/ 'M/71 67 218 el,ctfci1,No. 11246 A l 3/1917I ~ 5/^/72 46 l 9 V . rz^^?.6 / 2 3 / 7 38/4/71 3 9 1^ 68/6/719/8/71 3 3 1^ 59/27/71 - 6 / 2 3 / 7 2 270 2^ 811/]7/71~ 9/13/72 3 01 3 ,4A u 8/6/718/31/71 25 2,6 rJecCroJ^ fxilC9/27/71 - 11/50i 3 9 4 . 1 4 p1ectru^z r`^lx11/17/71~ 2/23/72 10 3 4.1 e]ccLroL! 0 f x ^ ^ ^3/20/72 ~ 10/25/72 18 9 2^ 33/20/72 ~ 8/16/72 14 9 2.1C/15171 _ 6 / 4 1 7 1 71 2^2`6/28/7I .- 9/13/71 77 2,09/27/71 -10/1-5/7I 18 2,7 OIL-tcudy f/ilc1.l/I7/7l-l2/3.7/71 ul 2^ 7 electrode fniI^3/20/72 ^ 4/25/71 36 1,8 cl nc t rod e fril,.3/20/72 ~ 4/25/72 36 2^ 8 elcrtroje f`Jl,(N i 3/20/72 - 6 / 2 1 / 72 95 1^ 8 e lec Lrodu . fx3/20/72 ~ 9/13/72 177 2^ 3 electrode faileN e s s 3/19/71 ~ 5/5/71 47 1.76/28/71 ~ 7/20/7I 22 1.58/6/718/17/71 Il 1^ 69/27/71 - 3/20/72 175 2.111/1.7/73,~ 5/10/72 175 2,40ozotrno 4/20/71 ~ 0/4/71 3 7 2 I`6 / 28 / 73 . ~ 7 / 3 0 1 71 3 2 1^ 78/6/7I8/17/72 ll 1^ 85/27/71 ~ 6/23/72 270 1^ 911117/71 3/16/72 120 Z"l

Iînm18 A l 6/28/71 - 7/20/71 22 2,1 electrode {alIaCrystal 8/6/719/27/71 52 2ÔD u d " 9/27/71 ~ 11/5/7I 3 9 2 311/17/71~ 3/16/72 120 3 ^ 3 leakedA u 8/6/7110/4/71 59 2^ 29/27/71 ~ 2/28/72 154 3 " 8\11/17/7I- 3/16/72 12 0 2.5C u 6/28/7I 9/27/71 91 2^ 9 electrode faile9/27/71 ~ 1.1/5/7I 3 9 2.1 leaked' 11/17172~ 1/25172 69 2.5 electrode faileNusa 6/18/71 ~ 7/1/723 3 ^ 0` ^/6/7l7/20/7l l^ l.78/6/718/}J/7i ll 2,6, /71 11/5/71 3 9 I1 911 y 17/71 6 9 2^ 30esatruu 6/28/71 ~ 8 y 17 50 2^ 19/27/71 - 11/5 `71 3 9 2^ 0Il/l7/7I~ | -- 89 23


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