CA1056044A - Electro-optical device employing nematic liquid crystal - Google Patents

Abstract

Electro-optical Device Employing Nematic Liquid Crystal Abstract:
In an electro-optical element comprising a pair of electrode plates and a layer of nematic liquid crystal material having a positive dielectric anisotropy positioned between the two plate, at least one of the electrode plates is coated on its inner face with organic high molecular materials. Molecular axes of the liquid crystal are oriented uniformly on the electrode face by rubbing the coated electrode along one direction.

Description

Back~round of the Invention:
This invention relates to an electro-optical elem~nt employing nematic liquid crystal materials of a positive dielectric ani~otropy.
It is known that nematic liquid crystals (hereinafter re~erred to as "N-liquid crystals") can be used for display, light modulation and the like by utilizing their specific property that optical characteristics are changed under application of electric ~ields, magnetic fields, ultrasonic waves and the like.
Such elements compri~e, in general~ an N-liquid crystal filled and supported between two substrates disposed to confront each other with a distance smaller than about 50 ~, at least one of which is transparent, and t~e change in the molecular arrangement caused under application of electric fields, magnetic fields, ultrasonic waves and the like is utilized for light modulation.
Compounds forming such N-liquid crystal are divided into two types depending on the molecular structure and dielectric properties, one type being characterized in that the molecular axis and electric dipole are substantially vertical to each -r~

- .- . .... ~ . . , . . -.~ . : . .. - - .. . -V4~
othfr (the liquid crystal of this type will herelnafter be referred to as "Nn-liquid crystal"~ and the other being charactff3-rized in that the molecular axis and electric dipole are sub-stantially in parallel (the liquid crystal of thi~ type will hereinafter be referred to as "Np-liquid crystaln). Accordingly, the Nn-llquid cry~tal indicates an N-liquid crystal ha~ing a negatlve dielectric ani~otropy, and the Np-liquid crystal indicates an N-liQuid crystal hav~ng a positive dielectrio ani~otropy.
The conventional Np-liqu~d cry~tal electro-optic~l element~
comprisfs8 a palr of electrode plates di~posed to confront each oth~r and a Np-liquid crystal layer interpo~ed between said plates.
The molecular aXf3S of the Np-liquid cry~tal are made in parallel w~th the electrode faces and are arranged in the sub~tantially ~amff dIrect~on in a plane parallel to the electrode plate, If ~een from the directio~ vertical to the eleotrode plate, moflecular axos are arranged in the ~tate continuously distortf~d from one anothf~r betwef$n ad~acent faoea. Such anorientatlon of *he mo~;ecular ax ~ i3 prepared by rubbing the electrode ~ace along - onQ~dlrfectlf~n with fabrlcs, paper or the like and plllng the tWo

2~ rubb~d ~ trode~ in su~h a way that the rubbing directlons are at right angle~ to eac~ other. The molecular axes near by the e~t~ode~face are oriented along the rubbing direction while the~moleoular axes in the ll~uld crystal layer are oriented in the':tt~te contlnuou~y d~torted. When polar1zed llght pas~e~
2S th~F~ ~d~th~ qu~d~Grystal layerj the pola;rlzatl~n plane ~f the }ight ls rot~ted depending on the degre~ of distortlon of the ~olocular;~xl8 dir~lon. Thls distortion o~ th~ molecular axis ; dir~c;tion:can be relaxed by ~ppllcation o~ an appropriate elQctrlc field.~Accordingly, by~adJu~ting th- intensity o~ the e~ectric ,. ;- ..~

)S~044 ~ it ls made possible to ad~ust rotation of th~ polarization plane of polarized light passlng through th~ element.
When the Np-liqu~d crystal element is interposed between two polarizing plates, it changes from the llg~t-shielding state to the light-transmitting state or from the light-transmitting state to tne light-shielding state depending on the applied voltage9 and thi3 light modulation ls ut$11zed for display.
Since the light modulation process utilizing the Np-llquid crystal element provided between two polarizing plates disposed in such a way that the osclllation planes Or light ~ross to each other exh~bits a mechanism quite dlfferent from a Nn-liquid cry~tal electro-optical element, a higher contrast ratio can be obtained in use for display o~ a pattern. Further, the ~p-liquld ~lectro-optical element can be utllized for construction of a Boolean algebra generator, a loglcal product gate, a "nor" gate and a more complicated loglcal circuit. Ir an Np-llquid crystal electro-; optical element capable of responding quickly i8 employed, it canbe utillzed for display of a three-d~mensional televi~ion or ~oving picture. Fhrther~ $n the case o~ the Np-llquid crystal electro-optical element, since the waYelength region of rays of transmiss$on ~arie~ depending on the electrlc ~oltage when it changes wlthin the range of the threshold value to the saturation ~oltage,` it can be used ~or display of color~
- . In the convent~onal Np-l~qui~ crystal eléctro-optlcal elemènts, the procèsc of rubbing the electrode face directly ln one dlrection is emplGyed ~or ori~ntation of the liquid crystal molecules a~ mentioned hereinbefore.. W~th this process, however, .
lt 1~ impo3~ble to or~ent the liqu~d crystal molecules u~iformly 80 that the di5play in the.obtained element become3 unu~iform and ::

.~, , ,:
1 ~ , ~ . ._ _. , W~93/0~30 2 0 ~ 2 0 8 ~ PCT/~Sg2/049~ ~

'":
Thus, it is advantageous to provide a new phase shifter with the T1 and T2 pair of thyristor valves 206 and 208. It is also advantageous retrofit and upgrade a preexisting phase shifter for faster performance by adding the T1 and T2 pair of valves 206 and 208 to each phase.
Alternatively, a preexisting mechanical reversing switch could be replaced by the entire reversing switch assembly 203 if desired for a particular applicat:ion. Furthermore, the switching netwoxk 250 may be employed in a variable susceptance phase shifter 20, a variable source phase shifter 120, or a conventional phase shifter, such as that shown in Fig. 8A or Fig. 9A.
Fig. 6 illustrates another embodiment of a three-phase fast-acting, thyristor-augmented, phase shift control switching network 350. Several of the items numbered in Fig. 6 are the same a~ described with respect - to the Fig. 1 embodiment and have item numbers increased by 300 over the item numbers for the like components in Fig. 1. For example, the excited windings 334 are coupled to the switching network 350 by the three-phase conductors 346-348, as opposed to the single phase representation of Fig. 1, where these conductors are represented by conductors labelled 46 and 48. Also, for convenience and clarity, the regulating windings 344 and ~TC 352 for each phase are shown schematically within the switching network 350 in Fig. 6. Furthermore, for simplicity, while each of the phases designated A, B and C are shown, the illustrated embodiment will be discussed with reference to only the phase a leg, labelled 302, since it is apparent ~rom Fig. 6 that each of the phases are constructed and operate identically. The phase A leg 302 of switching network 350 may optionally include a thyristor-augmented reversing switch (not shown) as described above with reference to Fig. 5.
In Fig. 6, the load tap changer (LTC) of the previously describad embodiments has been substituted with a switched load tap changer (LTC) 309. The switched LTC
309 comprises a mechanical switch 310 (also designated as ~' ''.

, . , : 1 . .; , ~ , . . .. . . . .

`` 105~044 An object of this invention is ta provide a Np-liquid crystal element with uniform orientation of the Np-liquid crystal molecules on an electrode face.
A further object of this invention is to provide the Np-liquid crystal element with prolonged life.
A still further object of this invention is to provide the ~p-liquidcrystal element with reduced deviation of electro-optical properties among products in case of mass-pro- -~
duction.
The foregoing objects can be attained with use of the -element of which at least one electroae is coated on its interior ~-.. ...
face with a thin layer of a certain organic high molecular material or magnesium fluoride, the coated electrode face being rubbed along one direction by known means.
Thus, in accordance with the present teachings, ~-a liquid crystal electro-optical element is provided which comprises a pair of electrode plates confronting each other and a thin layer of nematic liquid crystal materiaI which has a positive dielectric anisotropy positioned between the two plates. At least one of the electrode plates is coated on its interior face with a thin layer of at least one member selected from the group consisting of urea resins, melamine :..:
resins, phenolic resins, opoxy resins, acrylic resins, unsatur- ~-ated pQlyester resins, alkyd resins, urethane resins, poly- ;~
vinyl acetate, polystyrene, cellulose resins and polybutadiene.
Particularly, in case the electrode is coated with nitrocellulose, acetylcellulose, cellulose acetate ~utyrate, cellulose acetate propionate or methylcellulose or mixture ~ -thereof, the element with good orientation of the liquid ~;
crystal molecules and excellent electro-optical properties can be o~tained, and furthermore, deviation of electro-optical D )~ ; ~

` `\
~OSb~0,44 properties among products is remarkably decreased in case of mass-production. :;:
Detailed Description of the Invention:
It was found that a Np-liquid crystal element of which the electrode plate is coated on its interior face with organic materials, particularly, a certain organic high molecular material and then rubbed with fabrics or paper along one direction is superior in orientation of the liquid crystal molecules and the life of the element to a Np-liquid crystal :
element in which the rubbing is conducted but no coating is applied.
Examples of the organic high molecular material which may . ~ '' .

:~ , ., ," , :
'. ~ :

: ' ..

- 5a -, -, , ... , ., , . - , , . . ;

1~5~

be u~ed include urea resins, melamine resin~, phenolic resin~, ~poxy resins, acryllc resinsJ unsaturated polye~ter resins, alkyd reslns, urethane resins, silicone resins, polyvinyl acetate, polystyrene, cellulose resin~ and polybutadiene~ The pr~polymer~, oligomers, monomer~ or mixtures thereo~ may al80 be u~ed for the coating material~.
The coating material is dissolved in suitable solvents, applied on the el~ctrode plates according to the known proces8es, for example, by ~pray coating, dip coating, bru~h coating, electrostati¢ coating, electrodepo~ition, roller coating or du3t coating,~and then, dried naturally or by heating. Resin films ~m~y~be al80 adhered to the electrode face under appli~ation o~
pr~sure and h~at. Further, the monomer mat~rial may be coa~0d ~, on th~ lectrode plate by vacuum-discharg~ polymerization.
15 The ;overcoat may be formed with use of a ~ingl~ coating materi:al or;1~- mixtllr~- snd also, may be o~ single layer or lam~nat~d Illm.-. ., ~ . ; .
~thi~kno~ of the overcoat i8 not particularly critical, but ln~Ga~ of tho thiCkn8SB too lar~o the re~ultlng element i8 ~8~0W~
1n~e8ponding~ Pr~rably, th~ thic~n~8s Or th~ ov~rcoab~is ~le-8~*han ~about 5 ~, more prererably le~s than l ~.
Q~the org ~ c high molecular ma~rials the phenollc r~
~ac~yl~e r-~in- ant oellulo~ resins are partl¢ul ~ly ~uit ~le:
~ ob~In ~ the elcmon$ with good orientation of t~e liquid ;~c ~ .~ole~ul~- and a prolonged li~e ~ demon~trated in the ~ ~ o~1ng Ex~pl~. Amon~he cellulos~re5in~ par~icularly,~
tho-~u~e~ nitrocellulos~, acetylc~llulo~e~ cellulo3e acet~t~
e~ llula~e acetate proplon~t~ and methyl~ellulo~e a~d ;~
~ix~ure~th~reof ~enders the re~ulting element~ excellent ~l~ctro~ptlc~l propertle~ a~ compared with the ~ase of the ., ., ~ .~ , . . .. . .

1()'~iO44 other organic high molecular materials.
The term of "cellulose resln" i~ used hereinafter a~
including the five cellulo~e type~ ~pecified abo~e. The coating of the cellulo~e resin on the electrode i8 ac¢ompli~hed by dis-solving the cellulose re~in into a suitable solv~nt ~uch asn-butyl acetate, acetone, methyl acetate, methyl ethyl ketone, methyl isobutyl ketone, butyl cellosolve and oarbitol to form a solution having a cellulose resin concentration o~ 0.1 to 5X by weight, pre~erably 0.5 to 2% by weight, and then coating the ~olut~on on the electrode according to a cu~tomary coating m~thod, ~or example, by dip coating, spray coating, brush coating, roller coating or the like. The coating i~ naturally dried or i3 dri~d by heatlng it at 40 to 80C. The abo~e-exemplified cellulos~
rë~in~oan bo u~d aingly or $n the for~ of a mixture o~ tWo or ~or~;~o~ them.
~: Th~ eledtrode coated wlth the coilulose re~in i8 then rubbed ~n~-o~e~dlrection ~veral time~ under ~pplication of a pressuro ~ofiat lea~t 1 g/c~2 wlth a brush, paper or cloth. Espec1ally g~od~or~éntatl~on can be at~ain~d ln molecul~s of the liquld 2~ ~ ~ stal~when ~ bing i~ conaùct~d und~r application Or a pressure to~00 g/cm~, and ln thl~ ca~e elements excell~nt ln the~
~ratlo can b- obtained.
~ .A~p~lr~of~the 80 ~re - treated el~ctrode plates are dlsposed t~ nf~o~t 6ach other wlth a di~tance Xept constant by a spa~er ~5 ~ . ~ quld-¢ry~*al is in~e¢ted into this ~pace d~tano~ to ~orm elem~nt,~
e~ sh~w~ data o~ the ~n1t1atlon voltsge and 8aturatlon tQg ~ ur~d ~ith r-3pect to el~mRn~ havlng an ~l~ctrad-c~-a:t~d:i~lth th~ c~llulo~ resln and element~ h~ing an ~leetrode ~os~o~s coated with an acrylic, melamlne, epoxy or phenol res~n.
Elements used for the mea~urement were prepared ~n th~ following manner.
A resin was dissolved in a 8uitabls solvent to form a solution ha~ing a resln concentration of 1,0%, and the solution was coated on a tran8parent electrode mounted glass according to the dip coating method. Drying of the overeoat was conducted at 100C. for 10 mlnutes in the case of the cellulose resin~ and ~n the ca8e o~ the other resins drying was conducted und~r th~ ;
pres~ribed curlng tem~erature and t~m~ conditions. In each coatlng the thicknes~ was ad~usted to about l~u, Then, thé
çoated electrode face wa~ rubbed with cotton cloth under appli-~ation of a pres~ure o~ 10 g/cm2 in th~ ca~e of the c~llulos~
re~ln or 30 k~/cmZ ln th~ ca~e of the other re~lns. In ~ach lS elem~nt, as th~ Np-liquid crystal material there was employed~an ~ :
~p~ u$d crystal aompositlon~aompr~slng 2T% by woight of p-~etho~
~den~-p~-n-butylanllin~, 27X by weight o~ p-ethoxybenzyli-n-bu~lanlllno, 26% by we~ght of p-ethoxyben~ylldene~
~:p ~ heptylan~lino, 10~ by weight Or p-oyan~benzylideneani1iné
. ~ .w~l~h~ of p-~yanophenyl-pt-nqoctyloxyben20at~,:and th~
~betw~n tho ~l-ctrode ~a~s wa~ ad~ustod to 7 *~ .S:~
ë~p~:c~ o ~h ro31n~2 one lot ~100 sheet~ of el-monts r-d~, ~and d~Y~atlons of the inltl~tlon volt~go and ..
n ~ol~ag- w re exam1n~d among the elements, In T~bl~
-~ ~ dégre- o~ deviatlon of the ~oltage i8 expres~d ~y the l~gth;:
th~ rr~w~ ~nd b~ the lni~l~tion voltage is meant an app~led -~
, - .. ;.: ~ ~
at whlch iO~ llght transmis~lQn was obtained and by the s~tqrat~ vol~a~e 1~ m~ant an appllod vol~age at wh~ch gO~ light t~ lo~ ~a~ ob~aln~d.

Table 1 Voltage ( Vrm~ ) Initiation Voltage upper arrow and Sa~ration Voltage lower arrow Resins 2 4 6 8 10 12 14 16 18 20 . , ,, . -- .
N~trocellulose (HIG40 manufactured by Asahi Kasei) Acetylcellulose I ,.-~
(LT_105 manufac~
tured by Daicel) ~, Cellulose Acetate ~-~
Butyra~e (EAB-171-2 manufactured by ~ >
-.' Eastman Rodak) ~ , . . .
Cellulo~e Acetate . Propionate (ASP ~_~
$ manufactured by Eastman Kodak) ~
~, ,., , . - . ,. ._. .
Methylcellulo~e ~65SH-4000 ~anufactured by Shinotsu Xagaku~
Acrylic Resln (RE-377 manufac-*ured by M~tsubi~hi:Rayon) ..~
~lamine Rcsin (D~llcan ~E#500 - manu~actured by Dainlppon Toryo) , . _ , ___ ~_ , __ __ , _ , _ _ _ . _ A . _ A_ ~
Re~i n ~Ahl3R#
6~ n~actured A~hi Kase~ ~ -. .~, Ph~c: ~osin (~ck~l manu~actured by ~ - >
De,ini~pon Ink) ~A 1~ _A~ _ , . _I ~ _~ . . - .

_ g _ ~OS~i04~

As is apparent from Table 1, in the el~ment~ having an electrode coated with the cellulo~e resin both the initiation voltage and saturation voltage are much lower than in the Qlements having an ~l~ctrode coated with an aorylic, melam$ne, epoxy or phenol resin. In fihort, the former element i3 advantageous over the latter elements in that the actuation voltage 1~ very low.
From Table 1, it i8 al80 apparent that in the oase o~ mass-productlon, deviat~on~ of th~ initiation ~oltags and saturation voltage are much 8maller among the ~ormer elementa than among the latter element~.
When tho uniformlty in the electro-optical re8ponse wa8 ally ~xamlned wlth re~peet to each o~ the ~lem~nts ~h~w~ ~n TaUe 1, it wa8 found that th~ el~ment having an electrode coated w1th th~ c~llulo~ re~in ~xhlbit~d a more uni~orm el~tro-optical re~pon~e throughout the entire element than the other elcm~nt~, Furth~r, ln the elements ha~lng an ole~trode coat~d wlth the ~ellulo8~ re~ln shown ln ~a~le 1, ther~ wa~ ob8erved no subst~ntlal d~f~renc~ o~ the actuation voltage in on~ element and lt wa~
found that ~ho dif~rence o~ the a¢~uation ~oltaga ln one ~l~ment wa- 1~ or ~Q~er.
Tabl~ 2 illustrateJ data o~ the variation range of thC
~m~x1~u~ oontPa~t ~a~lo (perCQnt tran~mi8~10n und~r no voltag-/
;p-ro-n~ tran~mi3~10n under ~aturation volta~e) d~term~n~d wlth ro*p~t to Rlemen:~ pr~pared by coatlng an el~ctrode with nitro- :
c-llulo~e and rubb~g the n$trocellulo4e ~oat under applicstion o~ pre~ure Or 1 g/~m2 to 1 k~/cm2 and element8 prqpared by ao~tln~ ~n el~troto With an acrylic, molamlne, epoxy or phenol Pes;~ ~nd rubblng th~ co~t u~er appa~cati~n o~ presJure o~ 10 ~m2 to 5Q kgJcm2. In e~eh of the element~ shown in Tabl~ 2, the coating thickness, the Np-liquid crystal material composition and the distance between the electrode faces were the same as those of the elements shown in l'able 1.
Table 2 Maximum Contrast Ratio Resin 10 20 30 40 50 60 70 80 90 100 Nitrocellulose (HIG 40 manufactured by Asahi Kasei) Acrylic Resin (RE-377 manufactured by Mitsubishi Rayon Melamine Resin (Delicon DE#5 manufactured by , Dainippon Toryo) Epoxy Resin (AER#664 , ::
manufactured by it ~ :
Asahi Kasei) l ;:~

Phenolic Resin (Beckosol ~anufacture~
by Dainippon Ink) I

As is apparent from Table 2, the elements having an electrode coated with nitrocellulose have a much higher maximum contrast ratio than the other elements and they always have a maximum ~05~i~44 contrast ratio of at least 30 s 1. Further, it was fou~d t~at wh~n the nitrocellulose coating is rubbed under appl~cation of pres~ure of 5 to 100 g/~.m2, eæpecially good contrast ratios ranging from 50 : 1 to 100 ; 1 can be obtained. Similar re~ult~
were obtained when acetylcellulose, cellulose acetate butyrate, cellulose acetate propionate and methyl cellulose wer~ used instead o~ the nitrocellulose.
The electro-optlcal characteristic~ o~ the element i8 hardly in~luen~Qd by th~ moleeular welght (degree of polymeri~ation) or degroo o~ ~ub~titutlon o~ the cellulo~e resln us~d f~r coatlng the elQctrode. Mor~ speciiically, e~en when cellulo~e r~sins dl~P~ring ln the moleeular weight tdegree of polymerizat~on) and ths degr~ a~ substltutlon are employod ~or Goating eloctrode, `thore~ ob~er~ed no ~ub~tantial dlffer~nce~ o~ the eleetro-opt~cal ~haracterl~tic~ among the re~ultlng element~ Thl~~e~:tyr- will readily b~ understood from Table 3 ~llu~tratlng dat~
o the inltiation voltage an~ saturation volta~e mea~urod wlth re,~p~ot.tc el~m~nt~ prepared by employing nltrocellulose and : ~ellulo~- aa~tMt~ butyrate re~ins d~fferlng in th~ ~iscosiky (a ~` ` 2~ Yl~¢081ty ind~ca~os a hlgher molecular welght) and the 8u~atitutlon a~-an electrode coating material. In ~ach o~ ement- ~hown ln Table 3, the rubbing pr~a~ure, the hlckn~ th~ quld crystal materlal composltion and d~ ~tan~e~b~t~ on th~ ~lectrode faces were ~he ~ame as tho~e of 2~ ~ e~ hown in Tabl~ 1~

~: ~ - , , ~ ~ , :~OS~0~4 g~
., ~
tll bt ~ ~O O N ~ r~ 0 0 ~D O
:~ ~ ~ ~ ~ ~C) N ~I N rl O O

-a~
s~l ~ J ~ 1~ N ~ ~C) N ~ ;1- N
;~ J ;t r ,0 a ~J N~i r~l ~; 0~ 0~C-- ~ ~ 1~
,~; ~ ~ ~ ~ ~ ~ ~1 ~Q ~ Il~ o o ,~ R
P ~ ~ 1 0 ~ ~ ~ ~ ~a~
'C
~ O ~1U~O
O
OO ~ ~
~ ~a ~ ~ O ~ OD O O ~U~ ~
11~~ 00 11 ~ ? rl ~e~-- ~ o o o ~ ~ o,1 ,~
~ `

3 :a ~ ~ ~ 0 ~ ~
2 bq ~ ,,9 ,~

h ~ 5 ,J
:, ~ ~ o - ~ 3 ~ ~
g ~ V ~ ~ al 1~
'~C ~ ~
~ ~ ~ ~ ~ ~ o ~2 ~ ;~; ~ I g .~ ~ U~
1 ~ 1 ~ ~ $ ~ ~ ~
' -1~)5t~044 A~ is apparent from Table 3, in each of nitrocellulose and cellulose acetate butyrate, there i8 brought about no substantial difference of the initiation and saturation voltages, namely the electro-optical characteristics, even when the molecular weight and the degree of saturation are changed. Also in the case of acetylcellulose, cellulose acetate propionate and methylcellulose, it was found that the electro-optical characte-ristics o~ the resulting elements were hardly influenced by the molecular weight and the degree of substitution.
Further, in the case of the element of this invention, the pressure to be applied at the rubblng treatment 1~ remarkably decreased,~and therefore, the rubbing treatment can be gr~atly fac1litated. Accordingly, in the caae of mas~ production, the deviation o~ the electro-optical characteri~tic~ can be highly reduced, and it is po~s~ble to prepare at low C08t8 in large qua~tltle~ the liquid crystal elem~nts. ;
~ Aooording to further embodiment of thl~ inrontion, adhe~ion of thë celluloae resi~n coat to th~ electrode fa¢e can be lmproved by:~:pr ~ d~ng b~tween th~ cellulose resin and electrode layers O a~ther~Dootting orgflnic high molecular sub~tanoe layer ha~ing ~o`od-~ ~ sion~to bothe~he cellulo~e resin A~d electrod~
~x ~ le~ Q~ ~u~h-thermosett$ng sub~tance~ ~nclude epoxy, phenolic ~ acrylie resins, and the other con~entional, t ~ o~at~i~g orEanic hlgh ~olecular ~ubstance~ may be ai8.0 us~ The:1~nterpo~ed thermose~ting ~ubstanGe layer ~hould not ~- o~hic~ne8~ too large in ~iew oi formlng further the e~ lo~ r~ln lay~r o~ said layer, and.proferably, the ~;thi~kne~ le.8,~ ~han about 1.0 ~, more preferably ~h~ range . , .
of Oil ~Q Q.5 ~.

l(~SW44 According to this invention, it was further fou~d that elements prepared by coating the electrode with magnesium fluoride and rubbing the overcoat have the same effects as the case o~
the organic high molecular coating material~. Formation o~ the overcoat of magnesium ~luoride may be effected according to the conventlonal thin-film formation of the inorganic material, for example by vacuum evaporation. The thickness of the overcoat may be less than about lJu, pre~erably less than about 0.5 ~.
This invention i9 illustrated by the following non-limitative example~.

105~044 Example 1 A glass plate of 3 X 4 cm~ provided with conductive layer of SnO2 ~ referred to a~ glass electrode in the follo~ing Ex~mples up to Example 14 ~ wa~ dipped lnto a 3 .
weight % solution sf cyanoacrylate adhe~ }5p-10 ~anufactured by TAORA Chdcal Co. Ltd ~ in acetorle~ Thu~
obtained o~ercoat was dried at room ten~peratue t and t~2en baked and drled in ~ dryer at 120-C for 30 1ainutes. The coated ~l~ctrode wa~ rubbed along one direct:ion with ~abrics under pre~r~ of lûg/¢m2 and a pair o~ the 80 pre-~xeated el~ctrode plate~ was po~itioned ~o that the rabb~ ng dir~ctlons are a~
right ~glQs to ~ch other, ~he two pla~es be~ ~rgined by an ~ngulatlng ~p~er of 4 ~ ln ~:hicJm~5~ f tbe aperture~
othex than ~ho Qp~nl~g for i~ tiag of zl ~iq~id cry~al ~terlal w~re ~led ~ith ~n ~dhe~i~re.
3 S ~ 2 The glass electrod~ ba~ dipped into a 1.0 ~e~gh~ % ~o3ut~on e of ~h0~ol~c resin (~cko~ol~ thy~a Lcohol to ~ppl~ the re~on ~olut~n on the el~etrode fae:e. The o~er~:oat w~s dr~ad at room te~p~r~tur, ~nd then b~ked ~d arled ln ~ er at 200-C for 10 ~n~t 8. ~FAe coa~d e~e¢~roae ~a~ ~b~a aloag one directlon ~: ~lth fa~r~ ~d~r pr~s~ure o~ 3û l~g~. The sa~ coll as that o~ E~le 1 ~fith t~ ~xc~ption of ~rQs~lnq ~e rubb~ng d~rec-~o~ at ~ u~gle o~ 45~ was fon~od, l~x~l~ 3 of ~ aone ~rho g~a~s ele¢~r~o wa~ dipped into ~ 200 ~ight % ~ol~ic~n ~ln ~ 45, li;h1n~t~u Kagak~ C~o.,Ltd J~an) ln hox~ ts~ appl~
solu~ic~ o~ ~ ~lel:trsde f~e. q!he o~ t wa~ dr~ea ~t ~o~ t~r~, ~d-~n b~l~od a~d drl~a in a dr~er ~t 210C
~or lû ~l~e~. ~e oo~ted ~ trode w~ bed along one dlr~ctiQql ~th ~abrlc~ ~nder p~es~ur~ of 30 Kg/~2.

10S~044 The 8ame cell as that of E~ampl~} 1 wa~ formed, the rubb~ng directions }: eing at right angle~ to each other.
Example 4 Polyester f~lm oî 1)1 ~n th~ckne~ (Lum~rror, manufacturea S ~y Toray Co. ,Ltd. ) wa~ po~itic~ned on the gla~ electroae and adhered to the electrode ~ace by pressure of 15 Rg~cm2 at 200C
T~e treated electrode wag r~bbe~ along one direction with - pressure/
~abrics ~nder o~ 30 ~/cm2. q!he same c:ell a~ that o~ Example ~ wa~ for~e~, the n~bing directions b~ing at right angles to 10 each other.
.- - . - . - . .:- .
3~a~nple 5 .
~.0 ~e~ght ~ of ure~ resin tUlo~df manufactured by M~tsui To~tsll Co.,Ltd) were dis~ol~ed ~n an equl-weight ~i~tclre of acetono ~d methanol (referre~ ~ereinafter to as mixed solvent~.
.'15 ThQ res~n ~olut~o2l was ap~lied on the glas~ electrode ~y ~oller ccat~ng and aried ~t room temperatur~ a~d t~e~ baked .
~d dried in ~ dryer at 150-C for 20 ~utesO The coated electroae gra5 rubbed along one d~rect~on under pre s~re of . . . . . . . .
- 30Rg/c~. ThQ same cell as that of }~xample 1 was formed, the rubbing directi~ns be~ng crossed at the angle of 45-C, .
~mple 6 T~e gla~ slectrode wa~ dipped lnto a 1.5 weight %
801utio~ of ~tyrene resi~ ~Stylit, Manufactured by Daido l~ogyo ~:
~ao.,~d~ ln th~ n~ed solve~t. ~e overcoat ~a~ dricd at room 2~ te~perature ana then, baked and ~Iried in ~ e~ at 180-~ ~or 10 ~ute~. ~he coa~ea elec:trod~ wa~ rubbed along one ~roction with f~brics under pre~su~e of ~g/C~12.
Tbe ~e cell a~ at of E~ample 1 was formed, th~ rabbing d~rectlon~ be~ng at right i~ngles t~ ead other 30 E~C~mP1Q 7 . ~,.

A

A resin sol~tion wa~ apE~lied o~ the glas~ elec~rod~
by dipping it ~nto a 2.5 weight ~ ~olutlon of ~l~ethan~
resin ~ V-Chroma, manufactured by ~ai Nlppon Toryo Co. ,Lt~. ~
~n the ~ix~d ~ol~nt and dri~d ~t room t~perature and ~hen, S balc~d and dried i~ a dryer at 150~C for 20 m~ntlte~.
The treat~d elec:trode wa~ r~bbed along one d~r~ction ~Ith fabri~ der pr~#sure of 30Kg/~:m2. The ~ 8 th~t of l~pl~ 1 wa~ for~ed, th~ rubbiAg dir~ctic~n~ being a~
right angles to ~ch o~er~
10 ~le 8 A 3~0 weight ~ solut~on of poly~mia2 (~ ~oera 11~, m~u~ctu~ed by 8u~o D~ko Co., Ltd.) ~n t~Q ~xe~ ol~n~
w~ ~pl~a on ~:he gl~8 elec~ pray coat~
The 0~es~:0~t wa~ arled ~t roo~ e~r t-are ~ n Wc~d and ~:S ~ ed in a ar~ar at aoo-c ~!or 20 ~v~. q!ho ~ated ~lectrodo ~aJ rub~ lo~g o~ d~xection ~ abr~cs un~l~r pr~e o~ 30 Rg~a~2. The ~ coll ~8 that of 13x~le 1 ~as forD~a, t~e ~ iag dir-ot~o~ ~ing ~t ~ght ~Igl~18 *0 ~aah o~her, .~ ~ 9 2~) A s~r s~lution w~8 applied on ~he ~la~ ~lectrode Sy~
dipping lt ~nto ~ 3.5 w~lght ~ solut~on o~ ~nyl acet:ate res~n tri~yo 1~ ~uf~:u~d by Illchia Pa~nt Ço.,~ n t~tQ l~liX~
a~3rco~ w~ dr~a at roo~ ~r~t~ and ~h~a~t0r, ~akod ~d dr~a in a dryer at 200C f~r 10 D~nu1:e~.
25 q!h~ ~oa~d ~c~ wus n~b~ed along one aire~:tion ~ith ~iG~ r pros~ of 1 }~g~. 2he s~e ce}l ~ that of E~ 1 was f~#d~ the 3~bing direc~ion~ b~ing at right ., ~ .
J tO ~a~h 0~.
~ea. 10 ~ ~0 ~ 5Iht % ~ tio~ of ~la~e r2~ Delicon, -- ~8 --lOSt~044 Manufactured by Dai Nippon Toryo ~.K.) in ~he m$xed ~olu~1On wa~ appl~ed on the gla83 electrode by spray coating.
The overcoat wa~ dried at room temperature ~nd th~reaft~r, baked and dried ~n a dryer at 190C for 15 ~inutes. T~e coated elect~ode wa~ rubbed along one direction with fabric~ ~na~r pr~ur~ of 30 ~/C~2. The sa~ cell as that of ~xampl~ 1 wa~
for~ed~ the rubbin~ direations belng at right angles to ~ach ~ther.
~1.~ 11 1~ ~he glasg ~l~ctrode wa~ dipped ~t~ a 3 ~æ~ght % ~olu~
of n~trocelSulos~ ro~in ~IG 40~ ~anu~actur~d ~y A~hi ~a~i Co.,~t~ n ~-butyl a~etate. Thus ob~ained o~r~uat wa~
dr~od ~t roo~ t~mp$rature ~D~ ths~, b~ked and drled in 2 dryer at lOO-C f~r S ~AUt~. Th~ coat~d eleGt~od~ w~ rubbod along onoe direetion ~1th fabric~ u~der pre~sur~ of 10 g~cm~. The ~ e~ll aJ that o~ Ex~ple 1 w~ ~or~ed, the r~bb~ng direc-t~ eln~ ~t right ~n~ to each o~h~r.

The gla~s d ~ctrode w~s dlpped into a 3 ~eight ~ 801ut~0n 2Q of ~a-~n ~ opro~yl ~loohol. Th~ over~oat on th~ ~loct~
~8 ~rie~l *.t r00~ ~at~e a~a t~ea, ~ea ~na ~ ~a ~r a~ l~O~C ~o~ 10 inE~ oatd ~le~ro~ ~41~
~bl3~ al~lg ~ ~ire~tion w~ abr~ nder pres~ure of 1 ~/~. ~ ~ c~ th~t of ~ fon~d, ~h~
25 ~r~b~:ng d~3tions l~ll~g ~t rlqht ~ngles to ~a~h oth~r.

h r ~ n ~ # a~l~e~ on th~ glass ¢lectx~e ~y ~pl~lag ;lt l~t~ a 3 ~a~h~ ~ ~olu~lon of a a~x~re of 9Q~
by ~o~g~t of 1.4 - ~dd3tl~n p4~ly~ P~ly~ 3o~t 30 ~a~actt~ d la~ ln~ ) ~a lo~ ~y w~ight o~ p~ lde ¢at~ly~t _ ~,9 _ , . ~ . , ., - - . . - ., .

~t~ ~ 44 in methanol. 'rhe obtained overcoat was dried at room temperature and then, baked in a dryer at 150 C for 20 minutes. The coated electrode was rubbed along one direc-tion wlth fabrics under pressure of 30 Kg/cm . The same cell as that of Example 1 was formed, the rubbing direc-tions being at right angles to each other.
A Np-liquid crystal composition consisting of 80% by weight of an equi-weight mixture of p-methoxybenzylidene-p' -m-butylaniline and p-ethoxybenzylidene-p'-m-butylaniline and 20% by weight of a compound represented by the formula, H0- ~ CH = N _ ~ N2 was injected into each cell of Examples 1 to 13 and the opening for injection was sealed with an adhesive. The liquid crystal electro-optic element obtained from the cell of Example 1 is referred to as Specimen 1 and the same applies correspondingly to Specimens 2-13. A blank ele-ment was formed by preparing the same cell as that of Example 1 except use of a non-coated electrode, injecting the above-mentioned Np-liquid crystal composition and sealing the cell.
Table 4 shows the characteristics of a light modul-ation apparatus where each element of gpecimens 1-13 and thè blank element were positioned between two polarizing plates.

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*l I : Q~c~llation plane~ of light are at r~ ght angle~ to each other.
~: O~dlla~ n pl~ne~ v~ light ~Ire ~n par~ l to each oth~r.
hr~shold and sa uration ~ eg in case eleme~t~ wer~
v~ually o~er~ed.. ThQ actu~l ~t~rat~on ~oltagQ (~or e:~pl~, ln c~u3 a p~rcent l~stht-~ra~ lon Gf 90%
attained ln the colour ch~nge o~ fr~ laclc to whl~
higher t~ he ob~ d ~al~e.
~3 Qn~ cycle ~clud~s ~ g ~l~nt~ ana at -20'C
for 14 hr~ d at 70~C for 10 hr~. w~ eh no flsld applled~
N~r~ of the l:yc~ ll the ~on~st rat~o ha~ ~eac~ed th~ so~ r~lat~ve to t~ l~for~ test. Th ~ ~t l~ber~ of thQ ~ycle ~ l~r~e ~how~ ~n ~ro~ed Jt~b~llty of o~Ientatlo~.
*~ . ) tlll S ~ ~!or 5û~2 ~ ontln~u~ appl~ed ~t SO-C a~d ~o ~:oatr~t ~ ~o r~a~ho~ a ~1~ of 1~8~
~ 50~ r~la~ at b~or~ applit~ lon of th~ flsld.
A 1~ t~ ~ d st~lllty of or~ tion.
~5 ~ 5 ~ o3~ 5~ ~z ~r~ contla~ ly ~pplled at 25-C ~r 50 bo~ M~Tpt t l~ ic~ rop~c tra~lt~on tq;~ra-~ ~ ol! ~ii~itl ~ dt~on ~ he ln~tlal appl1c U_ s~d ~t~ 1AP~ ~3f 500 ~w~ ! ~y ole~
~la~ ~ct~ 8 p~:e at 'ch ~terfaa~ b-~uid cryst~ ~rlaL ~d ~l.ectrod ~r~ 1~o }d ~a S~C d ~ 0ll ol~ ~ha lig~id gly, el~nt~ e~h~lti~g u _ ~ r~ p~d~ ~p~dl~ a~ th~ o~:e, 'l'he liquid crystal composition used in the Examples has a mesomorphic range of -15~ 61C. ' Current density per 1 cm2 through an element at the initial applica-tion and after 500 hours.
The application conditions are the same as in *5.
If the electro-chemical reaction takes plase at the interface between the liquid drystal and electrode layers, the current density becomes large. Accordingly, elements exhibiting a large increase in the current density after 500 hours show that the electro-chemical reaction proceeds rapidly and therefore, the life of the element becomes short.
Example 14 In203 was coated by vacuum evaporation on a square sheet of hard glass of a size of 5 cm x 5 cm so that the surface resistivity of 500JQcm was attained, to thereby form a transparent electrode plate having a percent transmission of 89%. Then, a 1.0% by weight solution of nitrocellulose (HIG-40 manufactured by Asahi Kasei) in n-butyl acetate was brush-coated on the electrode face and dried at 100 C. for 10 minutes. The thickness of the ~"
so formed nitrocellulose coat was about 1~ . Six pairs of the so formed electrode plates having an electrode face coated with nitrocellulose were prepared, and they were rubbed three times along one direction under application of pressures of lg/cm , 5 g/cm2,. 25 g/cm2, 125 g/cm2, 250 g/cm . and 1 Kg/cm , respectively. Then, 6 pairs of the so rubbed electrode plates were formed into 6 liquid crystal elements by employing as a Np-liquid crystal ~ -material a composition comprising 27% by weight of p-meth- ' oxybenzylidene-p'-n-butylaniline, 27% by weight of p-ethoxybenzylidene-p'-n--butylaniline, 26% by weight of p-ethoxybenzyldene-p'-n-heptylaniline, 10% by weight of p-cyanobenzylidene-aniline and 10% by weight of p-cyano-phenyl-p'-octyloxybenzoate. In each element, the distance between the electrode faces was adjusted to 7 + 1.5y .
Each element exhibited a completely uniform electro-opti-cal response throughout the entire element. These ele-ments has an initiation voltage of about 4.3 V and a saturation voltage of about 6.5 V. Each of these elements had a maximum contrast ratio of at least ~0 : 1.
Especially, the elements obtained by conducting the rubbung under 5 g/cm and 25 g/cm2 had a maximum contrast ratio of 80 : 1. .
Example 15 ---- '' ' '~ ,' In203 was coated by vacuum evaporation on a square -:
sheet of hard glass having a size of 5 cm x 5 cm so that the surface resistivity of 1 KJ~- cm2 was attained, to thereby form a transparent electrode having a percent trans- .
mission of 90%. Four pairs of the so formed electrode plates were prepared. The electrode faces were coated ~:;
according to the dip coating method of employing a 1.0% ~:

by weight solition of acetylcellulose (LT-105, manufactured ;-manufactured by Daicel~, cellulose acetate butyrate (EAB-171-2, ::.
by Lastman Kodak), cellulose acetate propionate (ASP, man- -ufactured by Eastman Kodak) or methylcellulose (65-SH-4000, -manufactured by Shinetsu Kagaku) in n-butyl acetate, and the coat was dried at 100C. for 10 minutes. In each ~ ~
pair, the thickness of the coat was about 1~.~. Then, the ~ :
electrode faces were rubbed three times in one direction :-under a pressure of 50 g/cm . Thus, 4 liquid crystal elements were prepared by employing 4 pairs of the so rubbed electrodes, differing in the electrode face-coating material.

The same Np-liquid crystal composition as used in Example 1 was employed, and the distance between the electrode was the same as in Example 1. Each of the so obtained elements exhibit-ed a completely uniform electro optical response throughout the entire element, The initiation voltage, saturation voltage, and maximum contrast ratio of the so prepared elements are shown in table 5.
Table 5 Resin Initiation Saturation Maximum Voltage (V)Volta&e (V) Contrast Ratio Acetylcellulose 5.2 12.0 50 ~

Cellulose acetate 4.4 10.6 60 1 butyrate ~ -Cellulose acetate 5.0 9.6 45 : 1 propionate Methylcellulose 4.6 8.6 65 : 1 Example 16 In2Q3 was coated by vacuum evaporation on a square sheet of hard glass of a size of 5 cm x 5 cm so that the surface resistivity of 1 K r~cm2 was attained~to thereby form a transparent electrode. A 0.3 weight /~ solution of phenolic resin (Beckosol, manufactured by Dainippon Ink Co., Ltd.) in àcetone was applied on the electrode face by brush-coating and then, dried and cured at 200C for 30 minutes. The thickness of the overcoat was about 0.3~. Further, a 1.0 weight ~/O solution of nitrocellulose (HIG 40, manufactured by Asahi Kasei Co.~ Ltd.) in n-butyl acetate was applied over the phenolic resin cost by brush-coating and then, dried at 100C for 10 minutes. The phenolic resin and nitrocellulose layers had a thickness of about 1.3~ in total.
The overcoat on the electrode was rubbed three times along one direction under pressure of 10 g/cm2. Ten liquid crystal elements were made from 20 sheets of the so treated electrode.

..... . . .. . . . . .. .

`~, The used Np-liquid crystal material and distance between electrode faces of each cell were the same as in Example 14.
All of the ten elements exhibited a completely uniform electro-optical responese throughout the entire element.
These elements had an initiation voltage of about 4.5 Vrms and a saturation voltage of about 6.5 Vrms, there being observed little difference from the case of Example 14.
Further, 10 pieces of elements of this example and 10 pieces of elements of Example 15 were subject to a -temperature cycle test (One cycle : Allowing elements to stand at -20C for 10 hours and at 70C for 14 hours).
In case of Example 14, 8 pieces of the 10 pieces brought about peeling of the overcoat off the electrodeFface after 20 cycles and thus, blowholes generated in the element.
On the contrary, in case of this example~ there was observed ~-~
no generation of blowholes in all of the elements after 20 ~ ;
cycles. -With use of a 0.3 weight % solution of urethane resin (V-chroma, Dai Nippon Toryo) in methyl ethyl ketone or a : .
0.3 weight % solution of a mixture of 90 weight % of epoxy resin ( AER #664~ Asahi Kasei ) and 10 weight % of tri ~dimethylamino methyl ~ phenol - tri -2- ethylhexate as a curing agent in butylcellosolve instead of the above-mentioned 0.1 weight % solution of phenolic resin in acetone~ the same effectc as io this example were att~ined.

_27-. .

Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A liquid crystal electro-optical element which comprises a pair of electrode plates confronting each other and a thin layer of nematic liquid crystal materials having a positive dielectric anisotropy positioned between the two plates, at least one of the electrode plates being coated on its interior face with a thin layer of at least one member selected from the group consisting of urea resins, melamine resins, phenolic resins, epoxy resins, acrylic resins, unsaturated polyester resins, alkyd resins, urethane resins, polyvinyl acetate, polystyrene, cellulose resins and polybutadiene.

2. A liquid crystal electro-optical element of claim 1 wherein the organic high molecular material is acrylic resins.

3. A liquid crystal electro-optical element of claim 2 wherein the acrylic resin is cyanoacrylate.

4. A liquid crystal electro-optical element of claim 1 wherein the organic high molecular material is phenolic resins.

5. A liquid crystal electro-optical element of claim 1 wherein the organic high molecular material is cellulose resins.

6. A liquid crystal electro-optical element of claim 5 wherein the cellulose resin is nitrocellulose.

7. A liquid crysta1 electro-optical element of claim 5 wherein the cellulose resin is acetylcellulose.

8. A liquid crystal electro-optical element of claim 5 wherein the cellulose resin is cellulose acetate butyrate.

9. A liquid crystal electro-optical element of claim 5 wherein the cellulose resin is cellulose acetate propionate.

10. A liquid crystal electro-optical element of claim 5 wherein the cellulose resin is methylcellulose.

11. A liquid crystal electro-optical element of claim 5 wherein the cellulose resin is a mixture of two or more of nitrocellulose, acetylcellulose, cellulose acetate butyrate, cellulose acetate propionate and methylcellulose.

12. A liquid crystal electro-optical element of claim 1 wherein the layer of the organic high molecular material has a thickness of less than about 5 M.

13. A liquid crystal electro-optical element of claim l wherein the layer of the organic high molecular material has a thickness of less than about 1.0 M.

14. A liquid crystal electro-optical element of claim 1 wherein the layer of the organic high molecular material consists of two layers, a thermosetting resin layer and a cellulose resin layer in sequence of access to the interior face of the electrode plate.