GB2200490A

GB2200490A - LCD devices

Info

Publication number: GB2200490A
Application number: GB08630318A
Authority: GB
Inventors: Paul Anthony Harris; Timothy Graeme Scale
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1986-12-18
Filing date: 1986-12-18
Publication date: 1988-08-03
Also published as: GB8630318D0; FR2608818A1; DE3742506A1

Description

2'd"-,'00490 1 p(X -1, Y 1.

- (LUAL 1 T T QT !)'A -:- -,:'m7. -,"E S DIL', LIMI- -yU to 'iquJ.' crystai dis-play devices.

1 -L - J_ --- - - a c ---1 -- ' I 1 7);, a:- i w,' o f m a '11 i o n 1 ' ---- - 0 aree used for a variety on instrurnient J. pr j c 1. c ck q an d th e 1 i k e 1.

r n,z? e,, 1 i t w is Ill e cla l i g.n r.r, e n. lU -1 'n av J ng -- ---- Ll op)osJ te - e.R.

n, U - 11 -- q _ d' U - f 'h= - U- cl-ys,a" are o r 9 0 o s -o i r a 11 su ch, tli a t i n the majority of the liquid crystal al-e p C1 _.... 1 al-e -no-j"k,io,ed to the and rear cf- c, e 11 - I P ., r_ --- ', - -,n la, 11 e s Ii - o f p o 11 R..---J., a +1 -,;..o n o f t h e. 'I w o p 1 a 'U e s ar, e in d the j ',-,! r, r 1: C m - j e z POOR -QUAki-TY &- 1, oto polaris-ation of une plaptees are 33. the assembly operates in pos-Itive image mode C> led ",,,,e assembly will appear n,) vol'a,,-,.e app' -L L, in the absence of a voltage, plane polarised n_ cajses -the cell to appear transparent or opaque -L I Cc_--- 1 U the orientation of the plane polariser.

When a vol'Uise is ar-nlied the molecules realign themselves to tIne electric field and the cell appears opaque a -!s as a 'It.,,T2LsUed nerLa'Uic" or 1 T', C C - -; ' ns I'Guest cell npr J_ -L. - a so called. -- U sim-,lar to TITi cells but - -1 ou C-- -- -. -- --- Z - -- -!' a dye or -v-e co- J_ )nal-ly the GE liqu2d crysta-L d-Js-,) ay i on e -plan e polar i s e When a voltage is - - J -1 ' e-.,, cell to be essentially colourless.

e n -. C-) 3 ap ' ' Jed 'I e ce l appears to be -o'lo-are-' -.;-.- -- U.1 - - to bhe nature of the dye or colourant.

o cells, Lsing means and -PiJ-IL'uers - - - - ^,--2 -e:1 7.

S - 1 p - S S JAC- Cl C.3 R b- y C_ C.. fi 1 L t -. are v- - c. ly methods c j 3 11 111 _k POOR QUALITY : reflective dj--s-,)-'La-lT in which the LCD is illuminated only by re'llected light ori.ginating from a source in front of the bransmissive LCD in which the illumination of the splay; a t s a -z:, J. s cai-)-sed by, a 11 source behind the display:

c-. trRnsLnJ-,ss-4-s.7-3 refnective transflective type which is a c=bination ef the above lighting methods.

a n d Tt is one object- of the invention to provide a liquid C- device which cain o-oerate by exterio.r light G, - W -)-J e 1 ea's + d, L f f e r e nt c o lour ef f e c t s an d wV. i ch : S - c -- E. - c o - d IZ-- n - n o n. e a s -D e c t o, '.' -p Uhe invention there is rovided a 2 c --2,.2 -- ', -L"- _; -,, s, c - i a d, -3, e d t o be e n e r g i, se d by i. n c i d e n t, r on. o 1 e x_t e- C 0 L! -2,r 1 S i -I g means a,ld back e a y- s, a t w i s t, e d n e a tb c ce; 11 a nd a g u e s t h o s t - 1, - 1 --- a dichroi c dye or ' ike colourant, and e J. n ch th. e c 0 -1 o...i r ed m e ans i s 0 f wide s-rject-rp.-!' band and the dye or li'ke colourant -E a relatively narrower band of the guest host cell is o. within the i..-i-ie band o- the coloured means, the system being -E'ro,--r, the such thq.t plane polarised ligInt emergen'U back rie,:-ns is on the guest host cell.

-provides a 4- T POOR GUALITY_ 1 a sed -,,.,,:tem a pted to be eylerg 7 s? e c - v e, ri. J1 e c om, p a c -1 1 J U - L2D S n2; exterior light comprising front -oolaris--ing Jc cell, back polarising means, a mee.ns, a twi.sted nemati'7. -- e l- h.) s - '11 c e -1, 1 c 0!-i t a i- n i n g a d i c h r o i c dy- e, a n d a c o 1 o u r e, 1 -1a'e, --he colour of +Ihe co",oured reflector rla+e e fl e -- ' 3 r -e- U - -- L, l beiro of a relatively wide spectral band and the dye of the G cell o esuest hosu a narrower band within the wide band, the s y Stt--- ar--angel stich that.

pLane -polarised light Ipack means and passes through o th.e coloured reflector and is then -"- = --. = -Z ' '-! OZ- ' n ' - -1 - r the guest hos- ce'-,, the back C:- L. 11 L. -L - and cell to +he fron' U, - -. - 1, : - - i S 2 -.-! S m e a,.-, S - e-,,-bodij-reit the -i,,-.1ven'tllon provides a transmissive LC-D system adapted to be viewed by fronri. a rear light source comprising front ne e n -'- cell a, nemat' c cel, a gties' hos a. -ichroic dye, back- polarising means and a G ilter being of colou-ed -E-lter, the colour of the coloured f de 1 band an, d 'Ish e di chroi c dye of the hos-11 cell of a narrower band within the wide band, the system being arranged such that plane polarised 1-;gvit ng L passes thron, 0-m the back -eans and s c i o n c- ir, a t i c c ell 11, t, h e t w s e U -- h POOR QUALITY the bacie--. - -L i, U polar li s J n E_ rmeans and,,.',,hen transr_itted 'hrougn t h -- f r,- n t - ---) 7 a r is i r. g m e a n S.

In a thi-_d embodiment the invention provides a cornn-pact t-ansf -LCD system which may be viewed by light L 1 e c. v e inating fro-m sources t the WD or Uo the front or rear of " t. c, ' combinp--'lon c. -- Gwo.

I U - L! - 11 Ine twisted eel! in.a cystem of the invention may be a---range:-'. to operate in positive or n egative image dis-play 1- U - U -1 0 2 e - T h_e 2 s 7, 1. ay i s, -, r e f e rab ly a mat r i x suc h as a d o t d it - i'Ll ).r ma- be well und- e-^:st ooi -- U %-_ - --- '. --- 1, 1 e x el el.0p drawings. in which is e schematic re-oresentation o-- U'-, + ructare of a t-wo colour reflective system of the nvention: a n d U -, 2 is i schematic representation cf the -re c- - ",.7c transmissive system of' the s 1ra c nven' o ri 6 POO QUALITY -ale are used 'c esersa-e nu:c.-.:-= - U Jb-- the same - L. u-' -feren- ernbodiments.

in 'he (1 m -- 1 - Figure, 1 comprises a sandwich of a front WD device of i -oo-ariser F, an LCD whIch is a TN, a back polariser B, an wnic,'1 I reflector CR. The colour a GH and a of the reflector CR may be of a wide spectral band and that G711 a nar--r.ow--=r one '1j."le wide band; in a .W - e _x Ex' in GH 5,Ies a red c. ----o L c dye -, - t, u r e be. T \T stat Lhe TN is -ess W mage mode.

- c, o:-ange and the coloured OFF state arranged to operate in ligh+ I,' ambient or, -he B is an d emierges P-lane the sta 'L.e i. e. there is passes the red c;c.-o-ired G1I.

is off The TN and -Passes through the polar4se1. "'hen the GH L - ly no applied voltage, such 1 red Lhe emergent orange coloured reflector CR and the appears to 'he observer to have a red L - -L ' U bp-cicE-round. When the GH is in the ON state i.e. there is an larised light remains e-5 volluage, the incident plane pol c, - uncoloured and reflects from the orange coloured reflector CE so that to the observer 1 - 'I n- M -- W D t')e colour appears to 1-- 1 d e re t ed Dasses back through 'H a dark 0',' state -In E a c o e.i s- ta + P p- -i.

1 71 j 7 4 91 - POR OU 1 - ALITY., M the c. a s e:p a y b -Lsius of GEL to the OF7 or 071,--uate -rise to a red or orange background - e s -oe -- t: -' ve ly -rt w- Ved that because.light incident on GH from TN ill be no' p-! &,, e PO'! -ised, no additional polarising means is e -0, u.L r e d Thus 'e-v.-,er components are requl red and 111he device -uCD of ca-t be used with high 'evels of ambient cl 1 _-I i J_ -L i n a O1rl ii n c lu d J. no a J. r e c i. s u _n 1 i gh t in one specific is used in a vehicle instrument - I- . 1 3, EL::

T.P 1) 7,U r C u -I,- -- 1,.

the a 2. the o- 1: - -11tel. the state of a vehicle systerr; - _, --c,.-i,pr c ) 1.

-'-e a low level of fuel fa non critical- e 7 am -c. 1. e- t c ir d il C a C' in e J-, - 1 0 o', to ind-lcate that engine oil -nn.jLJ- n-) ( ra-ge 1 U -L pressure has fallen to -P darigerously low 'Level (critical - 1. 1 1, 'I ---e - ---ision.

hic,e cond- - I n the n,-LO Pi,,:,rure 2, the coloured re-flectuor. CR is 1 replaced b,-., a Spectral band CO1OUr filter CF and the L r,.h+ +hr)-.).g,i the -t'Jltpi, from. the rear E-ht source nto he device which operaes n the S.Own.

M1. _ U --- - C_. 1 I-Ichroic d-e GH. is .-e 1 1 enlour CP.

the embodiment of Pli&ure 1 PR POOR QUALITY- 2 JT"iie device operates on the same lines The TN may operate in -positive or iega-,--v=- il,,orle and the GH is switched into 9Ln 0IN or 0125F state, as explained in relation to Figure 1 (1 -L -L he inven'i-.)n -s not a COMMIon CR7 orn--n,-e red: more C iMited to the embodiments shown. For and GH when immediately adjacent 1 the colours need not be than two colours may be empoyed; L- 11 - -L nE lters may be present. 1 Lhe Ii D means and -i- my be usel., i j vehicles, aircraft and the other apparatus e.g. photocopiers, calculators, I-L i i - C-1- %11

Claims

1. A compact LCD system adapted to be energised by incident exterior light comprising front polarising means and back polarising means, a twisted nematic cell and a guest host cell containing a dichroic dye or like colourant, and coloured means in which the coloured means is of a relatively wide spectral band and the dye or like colourant of the quest host cell is of a relatively narrower band within the wide band of the coloured means, the system being arranged such that plane polarised light emergent from the back polarising means is incident on the guest host cell.

2. A compact LCD system adapted to be energised in the reflective mode by incident exterior light comprising front polarising means, a twistednematic cell, back polarising means, a guest host cell containing a dichroic dye, and a coloured reflector plate, the colour of the coloured reflector plate being of a relatively wide spectral band and the dye of the guest host cell of a narrower band within the wideband, the system being arranged such that plane polarised light emerges from the back polarising means and passes through the quest-host cell on to the coloured reflector and is then reflected back through the guest host cell, the back polarising means and the twisted nematic cell - to- to the front polarising means.

3. A compact LCD system adapted to be energised in the transmissive mode by incident light from a rear light source comprising front polarising means, a twisted nematic cell, a guest host cell containing a dichroic dye, back polarising means and a coloured filter, the colour of the coloured filter being of a relatively wide spectral band and the dichroic dye of the guest host cell of a narrower band within the wide band, the system being arranged such that plane-polarised light emerges from the back polarising means and passes through the guest host cell on to the twisted nematic cell, the back polarising means and is then transmitted through the front polarising means.

4.

2 Publiskied 1988 at The Pwen, 0Mce. Stat.. Ho.l;e.. 66 71 ULgTlHolborn, Londor WC1R 4TF FurUier copies mkv be obtaine'. L-o,-,. The Paten., =-,c Sales Branch. St Lla:,v Cray. Orpingwn, Kent BR5 3RD Printed by Multiplex toechniques ltd. St Mary Cray. Kent Con- 1/E37

4. A compact LCD system according to any preceding Claim and disposed relative to light sources at the front or rear of the LCb or a combination of the two.

5. A compact LCD system according to any preceding Claim characterised in that the twisted nematic cell is arranged to operate in a positive or negative image display mode.

ZI -R - i- -6. A compact LCD system according to any preceding Claim characterised in that the display is of a dot matrix type.

A 7. A compact LCD system substantially as described- herein with reference to Figure 1 or 2.