Note: Descriptions are shown in the official language in which they were submitted.
~ ` ~
PHN.6924
KTS/AvdV
`, ~ 2~ . 74
~ ,
"Image display cell"
~. . .
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'- The invention relates to an image display
~: d~ .
~ cell having a transparent wall part and provided
'~ with an aqueous solution of a N,N'-disubstituted-4,4'-
'; blpyridinium salt as a reverslbly reducible redox
substance and a halide as a reversibly oxidizable redox
substance, which solution is in contact with at least
two inert electrodes.
' Such a cell ~rhen used as an indicator is
descrlbed~ln~Chemical Abstracts 74, 48964x (1971).
10 ~ ~ In this cell, N,N'-dimethyl-4,4~-bipyridiniumdichloride
is used as the reversibly reducible sub tance and
pota _ium chloride as the reversible oxidlzable substance.
; If a voltage higher than the threshold value is applied
across the electrodes, the bip~ridinium ion is con-
s: ~ ~ verted at the oath~ode into a blue-coloured radical ion
which colours the electrode surface and thus produces
an image. Simult'aneously, at the 'anode chloride is
converted lnto chlorine.
The known cell when used a.s an imaee display
~ c ll ha~s tha di.sadvantage that the blue-coloured radical ''
ion~l dissolved in the medium and henc~ diffuses away
rom th~ electrode. As a result, contrast of the image
i reduced. Furthermore the chlorine produced at the
- anode :is dissolvcd in t'he medium and by d:iffusion comes
PHN 6924
' ' ' ~
into contact with the blue-coloured radical ion, causing
~ the lat~er to be converted to its leuco-form. Although
,, this chemical reaction can be counteracted by incorpora- ,
;1 ting a diaphragm between the cathode and anode spaces o~
$ 5 the cell, diffusion of the blue-coloured radical ion from, the cathode to the medium of the cathode space cannot be
~-, prevented, with a resulting loss in contrast of the image.
The properties of the cell further require a potential
difference greater than the threshold value ~o be main-
.. . .
~ 10 tained across the electrodes as long as an image is to be '-
. ... :
maintained.
~-i Our Canadian Patent 950,653 which issued on
July 9, 1974 also describes an image display cell in whic,h
N, N'-disubstituted-4,4'-bipyridinium compounds are used.
In this cell the reversibly oxidizable substances are
~`- ~ either tetrachlorohydroquinone or ferrous salts. This cell
:': ~ :
has the same dlsadvantages as the above-descrlbed one.
.
Pre-published German Patent Appllcation 2,043,5~2
by Imperial Chemical Industries Ltd. (I.C.I.) and which
was published on March 11, 1971 describes an opt~cal
light filter in which N.N'-disubstltuted-4,4'-blpyrldinium
compounds are used. In many cases the bipyridinlum compounds
used produce soluble radlcal cation salts which diffuse
away from the cathode. All the oxldation products formed
at the anode are soluble in ~he medlum. Maintal,n~,ng an
~ obtalned optlcal denslty of the filter consequently
5~ requl,res an electr1c current flow such that the loss
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PHN 6924
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of coloured compound due to oxidation ;s compensated for -
by the products formed at the anode. When the filter is
used as an image display cell ,it moreover suffers from
. .:
the disadvantage that the contrast of the image decreases -~
in all the cases in which the coloured substance is not
insoluble in the medium.
It is an object of the present invention to pro-
vide an image display cell in which the image is main-
tained even if no current flows through the cell.
.~ .. . .
Netherlands Patent Application 7,116,637 by ~ -
Imperial Chemical Industries Ltd. (I.C.I.) and laid
open to public inspection and published on June 12, 1972
. i . .
describes a cell in which N,N'-di-(p-cyanophenyl)-4,4'-
;;l bipyridiniumchloride is used as the reversibly reducible
substance. In this cell the chloride ~on whlch precipi-
tates at the silver anode in the form of AgCl acts as the
reversible oxidizable component. The application as an
alternation mentions the use of the bipyridinium radical
~h~ cation chloriide as the reversibly oxidlzable substance.
In the latter case, prior to assembly of the cell the
anode is electrolytiically coa~ed wiith the sa,d radlcal
catiion, which means an additional compliication of cell
manufacture.
Although the cell according to the latter patent
applircatiion satlsf-es the requ,rement that the image
should be maintained in the absence o~ current flow, it
has d1sadvantages which are avoided by the cell according to
the present invention.
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One of these disadvantages is that the
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solubility of the bipyridinium compound used is
lower by a factor of 10 than the minimum solubility
, required to obtain~a high concentration of the sub-
stance in the medium and hence to enable a high-contrast
image to be formed in a very short time. -
In addition, in thG known cell the redox
potential at which the pyridinium compound takes up
one electron with the formation of a green-coloured
f~ 10 radical oation salt differs by only 0.2 volt from the
potential at ~hich the compound takes up a second
electron and is converted into a substantially colour-
less sabstance. Consequently the voltage applied
across the electrodes is allowed to ~-ary within very
narrow limits only, with the result that this factor
^ 3~ also seriously limits the speed at which an image can
be formed.
Anoth0r reason why in ths known cell maintaining
,, ~ ~ the correct potential difference across thc electrodes
is of importance is that the substantially colourless
compound produced by the taking up of two electrons
~ reaots very slowly only with the initial substance with
;~ the formation of the radical cation salt.
Another disadvantage of the kno~f~n cell is that
thc disp1ay electrode is not homogeneously coloured but
. ~
;-~3 ~ the colourlng is greatly dependcnt upon the shape and
disposition of the anode.
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P}IN . 69 2
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~ The image display cell according to the ~.
' invention ~hich avoids all the said disadvantages
is characterized in that the reversibly reducible
-. redox substance either is a compound of the formula .~ ...
2 ( m
~ ~ 5 R1 ~ ~ ~ - l(CH2)n~N X N~2 .2(m-~1)X (1)
~- m
~'i'.:
`:~ where
m = 0, in which case R1 and R2 represent a linear or
bra~ohed alkyI, alkenyl, alc~oxycarbonylalkyl~or phenyl-
alkyl group containlng up to ~10 carbon atoms.which may
10~ be substltuted with a halogen~or nltrlle, or a~morpho-
linooarbonylmethyl group in whlch the morphollno~group
may be~ substituted with one or two methyl groups, ~and
X ~epreseDts a monovalent anion seleoted from the group:
~ comprising ClOI, , BFI~ , N3 , Cl ,~Br , F and C6H5S03
;~L~ 1;5 ~ so, that the solubility of the substance in water exceeds
mol/l and the solubility product in water of the
: radl;cal cation salt formed by reduction of the oompound : ..
is les~ than 5 times 10 5 (concentrations in mol/l), -i
or m = I, i~n ~hich case R1 and R2 are the same and each
~ 20~ ; represent~an:alkyl eroup containing ~rom 1 to 5 carbon ..
-~ ~ atoms or a benzyl group and n - 4,
,!'` .~ X represents a ClOI~ ion, if R1 and R2 represent an
.alkyl group containing from 1 to 3 carbon atoms, or -:
a BF4 ion, if R1 and R2 represent an alkyl group con-
25~ taining fronl 2 to ~ carbon atoms or a benzyl group,
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PHN. 6924. '
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or
m = 2 or 3, in which case n = 4 and Rl and R2 each represent
' an ethyl or propyl group and X represents a BF4 or C104 ; -
ion, or the reversibly reducible redox substance is the
'~ 5 reaction product of 4,4'-bipyridyl and an CxJO-dibromoalkane ''~
.~
~ containing from 4 to 7 carbon atoms, obtained in a polar '~
~ . ~
aprotic solvent at temperatures between room temperature and
~ the boiling point of the mixture, and the reversibly oxidiz-
- '~ able redox substance is an alkali metal bromide or quaternary '
ammonium brom;de having a minimum solubility of 10 2 mol/l -
` ~i as far as the cation of the bromide does not precipitate with
the anion of the reducible redox substance.
One skilled in the art will know which of the
'.~ cat~ons used precipitate with perchlorate or borontetra- ' - '
fluoride ions. In general this is not the case with ' ~ ~
:- 1: .
lithium, sodium and quaternary ammonium ions.
It should be mentioned that compounds of the
formula l in wh~ch m = O are also used ;n the image display ;1
cell described in our Canadian Patent 984,604 which issued
on March 2,'1976. According to said Canadian Patent, however,
the revers~bly oxidizable substance is not a bromide, as in
the present inventiGn, but the'radical cation salt produced
by reduction of a compound of the formula 1. A disadvantage ; ;
o~ the'relevant cell is the'complexity of assembly, similarly
; 25 to wha~ was mentioned above with
~ . ~
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;~3~ PHN. 6924. ~ -
respect to an embodiment of the cell described in previou~ly
mentioned Netherlands Patent Application 7,116,637.
- The structure of the reaction product of
CX, C~-d;bromo-alkane and bipyridyl is not known. It may be -
assumed that the structure of a part of the reaction product
can be represented by the formula l in which n = 4 to 7, --
X = Br and Rl and/or R2 represent an ~-bromoalkyl group. -
Attempts to determine the value of m by determining the amount
.~ ......
, of covalently bound bromine in the reaction product yielded
~ lO values of a height such that it must be assumed that part of
,~ the reaction product consists of compounds having a cyclic
structure. :- ;
l~ The compounds of the formula l in which m = 2 or 3
are novel compounds. Hence the invention also relates to :;
S 15 these compounds and to their preparation--. Thé compounds - ;
are obtainable by methods known for synthesizing such com~
pounds~and by analogous methods. ~5
For example, the compounds of the formula l in which
,, - ~: : . .. . .
~ m = 2 are obtainable by reacting a~compound of the formula 2
+ ' '~
Rl ~ N ~ N+- (CH2)4 - Br. 2Br (2) -
with a compound of the'formula 3
Rl - N ~ R - (C~2)~- ; ~ ; . 3Br (3)
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~-~ Compounds of the formula 1 in whi.ch m = 3
are obtainable by reacting a compound of the formula 3
3 . with a compound of the formula 4
1 ~ ~ (CH2)4 ~ ~ N -(CH2)4Br-4Br (~J
... .
.. : 5 Compounds of the formula 2 are obtainable by
. ~ . reacting N-ethyl of N-propyldipyridylbromide with
... : 1,4-dibromobutane, whllst a reaction of a compound
of the formula 2 ~ith bipyridyl yiolds a compound of
the formula 3.~Compounds of the formu~ 4~are~obtained
~ ~ by~ reacting a compound o~ the formula 3 with 1,4-
dlbromobutane.
All the abo~e reaction~s are performed in à
polar aprotio~solvent at temperatures whlch lie bet~een
room temperature and the boiling point of the~reaction
;15~ mlxture. ~ ~
Examples of polar aprotic solvents are
dlmebhylformamide, aoetonltrlle, sulfo~lane, dimethyl-
sul~oxide, propylenecarborlate and the like.
It is o:f essential importance ~or the cell
: :according to the invention that the compounds of the
formula~1 are satisfacborily ~soluble in the medlum
so that the medium contains sufficient substance for
fast~.image formation. On the other hand, it is of
partioular lmportance for the reduction product formed
~t; :~ 25 : at the display electrode to be hardly soluble in the
~, ~, , :
. ' . pH~T .6924
.~" ' ' 2~ ,.74
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~. . .
reduced by diffusion of the coloured compound to
~i the medium.
. Compounds of the formula 1 in which m = 0
.i 5satisfy the above requirements by a suitable combination
of the substituents R1 and R2 and the anion X .
It ~as found that the solubility of these
compounds in water increases as R1, R2 and X are
smaller. It was also found that the solubility product z~
10of the reduction products of the said~compounds de-
creases as R1- R2 and X are greater.
A~branched alkyl group R1~ or Rz~ causes a
compound~of the formula 1 to have a lower solubility and !-`
thè reduction product obtained from it to have a smaller
15~solubility product than a straight-ohain alkyl group
containing the same number of carbon atoms. :
~'S ; :~ If R1 and R2 represent alkyl groups, th~
~ follo~qln~ combinations of R1, Rz~and X may be chosen:
;i, ~?,,:~ ' R1 and R2 ~ --
1 ~ C6 Cll~- . :.
::20 ~ C - C7 BF4-
"~ :C5 - Cg Br ~:
6 ~ C8 3 .
6 ~ C9 ~ : ~l-
C G ~ 0
-10~
-.S,:~, " ~ , . '
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PHN.6924
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In the case oP an anion X , as a rule an
¦ alkenyl group is chosen which has the same number
~; of carbon atoms as, or 1 carbon atom more than, the
alkyl group which is combined with said anion.
In general, an alkoxycarbonylalkyl group
~`j when combined with a given anion X has one carbon
` ~ atom less than analkyl group combined with said anion X .
As a rule, a phenylallcyl group is chosen so
as to have two carbon atoms more than an alk~l group.
. . ~ , ,
;10~ ~ If a group R1 or R3 carries a nitrlle group,
the carbon skeleton o~ R1~or R2 may as a rule~ contain
two carbon~atoms less than an~unsubstl~tuted group. ~ -
a group R1 or R2 carries a halogen~atom,
the number of oarbon Qtom3 oi the group may ln general
15 ~ be equal to tha-t of an unsubstitutad group.
A aompound used in the cell~according to
~ the invention as a reversible reduclble substance
'. .~3 ,~ b ~ (hereinafter also referred to as a viologen~f at the
cathode is converted into a blue-ooloured radiaal
20 ~ ~ oatlon by taking up an aleotron. The number o~ electrons
which a compound oan take up from the electrode is
equal to the number o~ bipyridyl groups contained in
the~molaoule. ~~
Compounds o~ the formula 1 in which m = 0
X5~ ocoupy a particular position amongst the reversibly
redu~clble compounds~used according to the invention,
beoause when reduced they form a non-porous film on
P~N . 692l~
24.4,7~ ,
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-~'` the electrodes ~hich can be erased at a particularly
high rate even ~ith potenticstatic control.
The bromine formed from bromide at the anode
j ~
is, combined with a quaternary ammonium bromide,
deposited on the anode as an insoluble salt.
~- The image display cell ~ccording to the
i ~ invention has a casing at least one wall or wall portion
- - of which is transparent, as to allow for the visual
.~,.,~ , .
~ perception of an image formed. It may be made from a
.;; ~ . . ..
synthetic materlal, a glass or the like,
The electrodes may consist of~stannic oxide,
ndiumoxide, plati~num, palladium, gold and other inert
electrode materials. ObviousIy it i5 not necessary for
all the electrodes to be made~o~ the same material.
15 ~ The electrodes~may alternabively co~nsist~o~carbon.
If the imaBe is~to be visually~perceptible, a carbon
electrods cannot be used as the display electrode because
the colour is not perceptible against a black background.
The electrccles may be formed in a variety of
s~apes, Also, more than one anode and/or cathode may
be~used.
The lmage produced may have th~ same shape
~7,'~ a the sùrface of the display electrode or as the
visible part of thi~ surface. When~a transparent electrode
25~ a~used as the display electrode, it may be deposited
on t~e inner surface of the transparent wall of the
ca~ing. Part o~ the electrode may be coa-ted with an
eleotrically non-ccnducting materlal, for example a
-12-
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~ PHN 692~1
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~ synthetic material, in which case the image will have
. the same shape as the uncoated part of the electrode
. surface. As an alternative, part of the ~all of the
cell may be screened by an external opaque mask, in
which case the image produced has the same shape as
~ ~ .
. the visible part of the display electrode.
~, ` The display electrode may alternatively be
applied to the rear wall of the casing so that the image
is viewed through the transparent wall and the~cell
liquid. However, it is nGt necessary for the lmage
electrode to be disposed on a wall of the ca.sing, but
~ A`~ t may also be disposed at another location where it
is surrounded by the cell liquid.~In this case lt may
:be preferably for the rear surface of thé eleotrode to
15~ ~ be coated with an electrically non-conducting material.
If the image is to be viewed froln two directions,
; : the display electrode may advantageously be located
; inside the cell not in contact with a wall because thus
in the case of a ~lat electrode - an image is produced
20 ~ on both major sur~aces.
Beoause in the cell according to the invention
the coloured substance adheres to~the electrode and
:~ does not disperse in the cell contents by diffusion,
: tha colour ~ormed may rapidly be removed by reversing
electrode polarity. This provides the important ad-
vantage that the response is not determined by the
,~;;- ;~æ~ spacing between the anode and the cathode. --
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:~! PHN.6921.~ ~
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, Consequently the position of the anode relative to
~ the cathode may be chosen at will. The anode may,
-~ for example, be at an angle of 90 to the cathode
or bo co-planar with it.
In the above an image has been referred to
.
which has the same shape as (the visible part of) the
.f~ display electrode, but obviously the image may alter-~
natively be built up from a number of components which
are provided by an equal number Or display electrodes
10; of the cell which are rendered operative.
If the or~each display electrode is disposed
on a transparent wall~of the cell, the contrast of~thè~
image may be increased by dispersing an lnsolublej for
example white, substance in the cell liquid. Suitable
5$ such substances are titanium oxide and b,~rium sulfate.
The cell according to the invention may be used
not only for dis~playing images but also as a voltage
dioatar. If a ~oltage higher than the minimum voltage
of about 1.5 volts required to cause the oell to respond
20;~ is, or has been, sot up across the electrodes, colour
is observed on the displa~ eleotrode.
A signal may, howe;ver, be observed by o-ther
than vlsual ~leans. Since in~the formation of colour
the surface~of tho electrode is coated with a viologon
25~ radioal~, ~the potential of the electrode relative to
the cell liquid changes. This change in potential can
be ohserved by means of a raference elec-trode.
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`j Even if the amount of electrical charge
~1~ which has passed through the cell is not enough to form
.: an amount of colouring substance sufficient to be
visually perceptible, the change in potential of the
electrode relative~ to the cell liquid can be observed
,;~ by.means of a reference electrode.
. Hence the cell may be used as a means of
~ ~ recording that a voltage has been set up across the
,~ . electrodes, causing a small amount of charge to pass
through the cell, in other words, the cell may ba used
. as a storage element. Obviously in such use of the cell
the transparent wall portion of the cell need not be
optically transparent. ~ \
Referenoe electrodes may be mads of the same \
materials as:the display electrodes, however, as an
alternative glass electrode, calomel electrodes and
~ the like may be used.
: S~ Reference slectrodes may also be used.to reduce
to a mi.nimum the time required for the formation of
~`; 20 ~ the image. If a oomparatively.high potential di.fference
. i9 set ùp across a oathode and an anode ofa~cell, thé
~ viologen in the viclnlty o~ the cathode will rapidly
.~ be reduced~ Further increase of the amaunt of reduced
viologen at the cathode will then depend upon the rate
at which viologen from the medium is conveyed to the
cathode. However, side reactions, for example the
formation of hydrogen, may occur, and this is undesirable.
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PHN.6924
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~ To prevent such side reactions the potential
; . , .
;, difference across the electrodes is chosen sothat
always a sufficient amount of viologen can diffuse to
-~! the cathode. Thus the rate at which initially colouring
matter is formed on the cathode is lower than in the
above case.
If a reference electrode disposed near the
cathode i9 used, the advantage of a rapid reaction due
to a large potential difference may be combined with the
advantage provided by the use of a smaller potential
~ difference in that side reactions are prevented.
.`~';'!1~, ` The potential difference produced across the cathode and
the reference electrode by the appllcation of~a potential
di~ferenoe across the cathode and the anode may con-
tinuously be c~ompared with a potential difference which
is~lower than, or equal to9 the maximum permlssible
potential difference between the cathode and the
reference electrode.`If9 for example, the measured
potentlal difference i9 greater, the potantial difference
across the cathode and the anode may be reduced until the
~ j. : . , :
` de~ired potential difference across the cathode and the
~' ~dr ~ refercnce electrode is reached.
;,,, ~: :
In ~neral the image display cell is operated
with a potential difference between 1.; volts and 10 volt9
Z5 ~ acro99 the display electrode and the counter electrode.
` ; A~ a rule a potential difference between 1.5 volts and
, . . .
~ 4 volts i9` applled.
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PHN 6924
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A visually perceptible image will as a rule
be obtained in about 0.01 second.
. The concentration of the viologen in the cell
liquid will usually be between 0.01 and 0.2 equivalent/
litre. In this connection, an equivalent of viologen -
means an amount of viologen which contains the same
number of bipyridyl groups as a mole of bipyridyl. - ~
Some of the compounds of the formula 1 in which ~ :
. m = 0 are known. They are obtainable by coupling
. .
bipyridyl with a halide by means of a Menskhutkin ~
reaction. The preparation of a number of compounds was -
~` described inter alia by Michaelis in J. Gen. Phys;ol. ; No. 16,859 (1933).
The resulting halides may simply be converted
into other salts. For example, the addition of silver
sulfate enables silver ha1ide to be precipi~ated, a ~-
solution of the viologen sulfate being obtalned. From
this, for examp1e, bariumsulfate may be precipitated
by the addition of a barium salt, for example barium
20~ nitrate, a solution of viologen n1trate being obtained.
The compounds o~ khe formula 1 in wh~lch m - 1
are descrifbed ln United K;ngdom patent specification
h: 1,054,397 by Imperial Chemical Industries Ltd. (I.C.I.)
and publ~shed on November 30~ 1966.
~ ~ ~The concentration of the alkall metal or quater-
nary ammonium bromide, for example tetraalkyl ammonium
brom~de, contained by the cell as a reversibly ox~dizable
substance 11s of the same order of magnltude as that of
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24.4.74
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the viologen compound. In order not to retard operation
"
of the cell, as a rule the concentration will be made
at least equal tothat of the viologen compound. ;-
The invention will npw be described more -fully
~ith reference to the following Examples.
EXAMPI,ES
;, ,; 1) A-glass cuvette two opposed walls of which
were internally coated with:an SnO2 electrode was rinsed
wlth nitrogen for 24 hours. The surface area o-f either
electrode WQS 1.5 cm2, the electrode spacing was 1 cm.
The resistance of the SnOz, which was measured by applying
a voltage to two conductive strips provided along two
opposite sides of an electrode, was 10 ohms~ ~he cell was
filled wlth an oxygen-free solution of tetramethylene
bis [4(1-éthylpyridin-4-yl)pyridiniu ~ tetraborofluoride
; (0.05 mol/litre) and NaBr (0.05 mol/litre3 in water which~
~" ~ previously had been boiled out whilst passing through
nltrogen.
A direct voltage of 2.5 volts was applied
., ,j
ZO across the electrodes ~or 250 milliseconds. As a result
,Z~ the cathode was ~oloured violet. The bromine formed at
the anode preoipitated as Br3 togethar with the tetra-
methylene bis ~4(1-ethyl-pyridin-4-yl)pyridiniunl~ ion
on the anode.
A~ter no voltage had been applied to the cell
for 1 minute9 a voltag¢ of reversed polarity was applied
'~ for 250 milliseconds, with the result that the coloured
~:';,~::
~' ~electrode wa~ decolourized.
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PHN. 692 4
24~4.74
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: 2) Example 1) was repeated with the difference
that a direct voltage of 2.5 volts was applied for
500 milliseconds. After 1 hour the coloured electrode
; was decolouri~ed by applyin~ a Yoltage of reversed
polarity for 500 milliseconds.
3) Example 1) was repea-ted with the same result,
using a cell, a side wall and part of the front 1~all
of which were coated with SnO2 electrodes.
4) Example 1) was repeated~wlth -the difference
~10 that the cell was filled with an aqueous solution of
tetramethylene bisL4 ( . -ethylpyrldin-4-yl)pyridl~lum}
tetraborofluoride (0.05 mol/litre) and tetramethyl-
ammoniumbromide (0~05 mol/litre)0
5) ~ ~ Example 1) was repeated, using aqueous solutions
15~ o~ eaoh~of the oompounds mentioned in Table~I and of
NaBr ~(0.05 mol/litre).
. ~ - ,
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~ TABLE I-
, . . . .
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1 TABLE I
R - ~ N+- ~(CH2)4- + ~T+ ~ R.2(m-~1)X
m .
- ~ :
:~ R X~u~c :~o~jlltr-
_ ~ ..
, CH3 1` Cl04 0.05
. C2H5 1 Cl04 0.05
5 ~: . C2~5 1 BF4 ~ o.05
3 7 1 C104 ~0.05
: 3 7 1 ~BF4 0.05
;; C~Hg 1 B~4~: 0.05
:: 5 1~1 ~ 1 BF4 0.05
10: ~6 ~ 2 1 BF4~ :~ ~: -5
~2H5 -:~2 : BF4 0.05:
2 5~ 3 BFL~ ~5
2 5 2 ~ ClO4 ~0.02
C2H5 ~ 3 :Cl04 ~ 0.02
5~ C5H11 ~ ~ 0~ : Br~: : 0.05
C~6H13~ .~ ~ ~Br ~ 0.05
C7H15 0 Br 0.05
: C6H5CH2 ~Br~ - ~0.05
_ _ : . ~ ~ ~
. ,~ 6) ~ Example 1):was repe~ted ~ith the diffte,renc~
20 ~ that the cell was fllleid with an aqueous solution
i of tetramethylene bis ~ benz~lpyridin-4-yl)p~ridlniumJ
; ~ tetraborofluoride (0.04 mol~lltr~e) and tetrabutylammonium-
:, ~ :broml:de (0.04 mol/litre).
7) 1 ~Exampl~ 1) was repeated with the dif~erenc~
25 ~ that~a direct voltage of 3 volts was appl:Led for
20~
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PHN~6924
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100 ~illisecondi. Then an equal voltage with reversed
polari-ty was applied for an equal period.
~ 8) Example 1) was repeated with the difference
`I that the SnO2 electrodes were replaced by In203
,~ 5 electrodes with a sheet resistance of 5 ohms.
9) Example 1) was repeated with the difference
that the cell was filled with an aqueous solution
~ of NaBr (0.05 mol/litre) and a polymeric quaternlzed
;`J`~ bipyridyl compound (0.05 equivalent/litre) obtained
10~ by reacting 1,4-dibromobutane and 4,4'-bipyridyl
in a polar aprotic solvent.
10)~ Example 1~) was re~p~eated~with~the difference ~
that the quaternized~polymeric~blpyridyl~oompound was ~ ;
pr~oduced~from bi~pyridyl and~one of~the~followin~g~
dibromoalkanes~
a~ 5-di~romop~ntane~
b);~ ,6-dibromo~exane~
c)~ 7-dibromoheptane.
Example 1) was r~p~eated with aqueous solutions
20~ of~(formula 1, m = 0)
TABLE-
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2 4 . 4 ~ 7 4
,3~
~ .
_ . . _
R1 R2 X
_ _ .
n.C3H7 n.C3H7 Cl0
i-C3~I7 i.C3H7 BF4
i.C3H7 i.C3H7 ClO
n.C4H9 ~n.C~H9 BF4
n.C4H9 n.C4H9 Cl0
n-C5H11 5 11 Br
CHC35H11 CH 5 1 ClO
C2H5 C2H5 Cl0
5 11 5 11 Cl0
3 3 4 8 3-CH3Cl~H~ BF~
3-CH3C,4H8 3 3 4 8 Br
'C6H13 n-~6H13 Cl0
n'C6 13 6 13 BF4
n'C6H13 n'C6H13 Br
n'C6H13 n- 6 13 Cl
n.cf5H13 n- 6 13
7 15 n-C7H15 BF4
'C7H15 7 15 Br
7 15 n.C7H15 ~ Cl
n'C7H15 7 15 F
7 15 .7 15
n'C7H15 7 15 6
n-C8H17 n.C8 17 Br
nC8H17 8 17 Cl
6 5 2 ~,6H5CH2 Br
-~ C6H5C3H6 6 5 3 6 Br
n.C H11 n-C7H15 Br
n.C5H11 3.5-dimethyl- BF
morpholino-
carbonylmethyl
3.5-dime-thyl- 3.5~dimethyl- F
morpholino- morpholino~
carbonylmet-hy~ carbonylme'hy]
:, - . . _____ ___
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PHN 6924
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The present invention will be described in more de-
tail with reference to the accompanying drawings in which:
Figure 1 shows a nickel plate having a pattern formed -
by grooves which can be used to form electrodes on a substrate
for an image display cell according to the present invention
and
Figure 2 shows a transparent plate which is to be
cemented to ~ype of plate shown in Figure l to form an image
~' display cell according to the present invention.
.. ,:, .
~ l0. Figure 3,which is on the same sheet as Figure l, shows
,, g ~ I p O /y r~ /~ 6 i~ a c r y ~
'' ''f'~ a Perspex, a registered trade mark for'~e~ys~re~e>substrate
~; coated with a pattern of gold film electrodes and
-i Figure 4, which is also on the same sheet as Figure 1,
i ~ shows the same type of substrate as shown in Fi~gure 3 and in-
. ~ , ... . .
dicates parts of the gold film pattern which~are covered with
an electrically insulating transparent lacquer.
12) Grooves having a depth of 0.4 mm and a width of 0.1 mm ;~;
were formed according to the pattern shown in Figure l in a
nickel plate 0.5 mm thick. A nickel wire was welded to each re-
sulting segment. The plate was then placed in a mould which
was ~illed w1th a synthetic resin in an amount such that the
...~,
grooves were filled with the resin and the attached wires pro~
I ~ truded from the resin. After the resin had hardened the as-
~ sembly was ground untll so much nickel and resin were removed
-.' 25~ from the plate that the segments were electrically disconnected
1 ~ .. . ,.~
from one another. The plate was polished and then coated with
a layer of gold by electrodeposition. A transparent plate of
Perspex formed with a recess as shown in Figure 2 was cemented - ;
to the plate. The cell was filled through the recess 12 with
~.............. . .
the same solutions as described in Example l), after which the ;
`'~ ' ' . '
~ 23
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: ':~
P~IN 6924 ;
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opening 12 was closed with a Perspex, a registered trade mark,
stoppPr and then sealed with a cement. The segments designated
by the reference numerals l to 7 were the display electrodes,
electrodes 8 to lO were the reference electrodes and electrode
11 was the counter electrode. For the operation of the cell a
circuit arrangement was used which compares the voltage set up ,
between the display electrodes and one of the reference elec-
trodes with a given signal voltage and which so controls the
current flowing through the counter electrode and the display
electrodes that the measured voltage becomes equal to the sig-
nal voltage. At a signal voltage of l volt all the operative
.~ ~ -. . .
display electrodes were coloured a deep purple after 0.01 second,
; whereupon the voltage was removed from the display electrodes.
~ 13) A Perspex~ a registe~ed trade mark, substrate was
.... ..
coated with a film of gold by vapour deposition. The pattern
of Figure 3 was then etched in ~he film. Part of the film (the
~ part shown shaded 1n Figure 4) was coated with an electrically
a insulating transparent lacquer. Subsequently a cell was con-
'j structed and operated in the manner described in Example 12). ,
) 20 14) A nickel plate was provided wlth grooves in the man-
,! ner described in Example 12) with the difference that instead
of the figure 8 a hole of 10 mm x 15 mm was formed at the centre.
.' . .
l Into this hole 25 platinum wires were inserted at right angles
....
to the plate surface to serve as display electrodes. The assembly
was embedded in resin, ground and polished in the manner described
in Example 12). Electrodes lO and ll were coated with a film
of gold. The cell was then finished and operated in the manner
! descr~bed in Example 12), with the difference that the operative
electrodes were switched off after only lO0 /us. By means of
1 30 a high-resistance voltmeter (input impedance ~ l M Q ) it was
.' . , .
~ - 24 - ~ i
PHN 6924 ^
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possib1e to detect which electrodes had been turned on and
which had not. In the first case a voltage difference of 90
millivolts was measured between the reference electrode 10
, . . . .
- and the relevant display electrode, whereas in the second case
no voltage difference was found. The information stored in
~` this manner can be erased in less than 100 /us.
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