Liquid crystal element

A liquid crystal element comprises a cell structure where a liquid crystal is disposed between a pair of electrode substrates, a first electrode substrate of said pair of electrode substrates having a first resin layer formed at the surface contacting the liquid crystal of the first electrode substrate by thermal curing resulted from dehydration ring closure, the first resin layer being able to control orientation of the liquid crystal, and a second electrode substrate having a second resin layer formed at the surface contacting the liquid crystal of the second electrode substrate by thermal curing at a temperature lower than that at which the first resin layer is formed, the second resin layer being able to control orientation of the liquid crystal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a liquid crystal element using a particular 
orientation film, and more particularly, to a twisted nematic liquid 
crystal element constituted of an electrode substrate, a dyed filter and 
the particular orientation film successively laminated in this order, or 
to a ferroelectric liquid crystal element. 
2. Description of the Related Art 
In a liquid crystal television panel using a conventional active matrix 
driving system, a thin film transistor (TFT) is connected to each picture 
element in a matrix state, a gate-on-pulse is applied to the TFT to 
conduct between the source and the drain, and at this time, and image 
signals are applied from the source and accumulated in a capacitor. The 
liquid crystal (for example, twisted nematic-TN liquid crystal) is driven 
corresponding to the accumulated image signals. Then, a color filter layer 
fitted to each picture element is subjected to optical switching to effect 
color display. 
U.S. Pat. No. 4,367,924 to Clark and Lagerwall discloses a bistable 
ferroelectric liquid crystal (FLC) element. It has been tried to apply the 
ferroelectric liquid crystal element to a color display. Heretofore, in 
case of a liquid crystal element containing a color filter formed with a 
dyed layer at the electrode surface side, a dyeing medium and a material 
having a sufficient heat resistance for dyeing can not be selected. 
Therefore, the color filter is not thermally stable and the heat curing 
temperature at which an orientation controlling film is formed on the 
color filter is limited. 
As a result, one method to overcome the above problem is that an 
orientation treatment such as a rubbing treatment is applied directly to 
the surface of the color filter so that the above-mentioned orientation 
controlling film is omitted. However, the inventors have found problems 
occur as shown below. 
FIG. 1A shows a driving wave shape applied to picture elements of a 
ferroelectric liquid crystal. 
FIG. 1B shows a voltage wave shape impressed to a liquid crystal itself at 
real time. That is, when a writing pulse, V.sub.ON, is applied to the 
ferroelectric liquid crystal from the opposing cross electrodes, the 
voltage wave shape substantially applied to the ferroelectric liquid 
crystal is as shown in FIG. 1B. That is, V.sub.0 upon applying a pulse is 
decrease by .DELTA.V.sub.0 at a rate of the time constant, .pi.=RC (R: 
resistance of FLC, C: capacitance of FLC). The less the resistance R, the 
larger the voltage drop, .DELTA.V.sub.0, and upon switching the pulse 
(upon trailing of pulse), -.DELTA.V.sub.0 of an opposite polarity is 
applied to the FLC. When this .vertline.-.DELTA.V.sub.0 .vertline. is 
larger than the reverse threshold voltage .vertline.-V.sub.th .vertline., 
for example, writing of black (opposite to writing of white) is effected. 
This is attributable to an electric field of an opposition direction 
(-.DELTA.V.sub.0) generated by discharge from capacitance of the 
dielectric member layer such as an orientation controlling film connected 
to the ferroelectric liquid crystal in series upon trailing of pulse. 
Therefore, there is the following problem. As mentioned above, the liquid 
crystal element for color display contains color filters in the cell, and 
the dye in the color filter is dissolved in the ferroelectric liquid 
crystal. When such liquid crystal element is used for a long time, 
resistance R of the ferroelectric liquid crystal is lowered with the lapse 
of time until at last the value of the above-mentioned electric field of 
the opposite direction (-.DELTA.V.sub.0) exceeds the reverse threshold 
voltage resulting in the inoperativeness of the desired electro-optical 
switching. 
When a row-subsequent writing system is applied to a ferroelectric liquid 
crystal element, there is, for example, a system wherein a pulse forming a 
first display state based on a first orientation state of a ferroelectric 
liquid crystal at phase t.sub.1 (becoming a first phase) is applied to all 
or some predetermined picture elements on row, and then a pulse capable of 
reversing a first display state to a second display state based on a 
second orientation state is applied to a picture element selected by phase 
t.sub.2 (which is to become the second phase). 
According to this system, at phase t.sub.2, a pulse having a voltage less 
than the threshold voltage and of a polarity opposite to the pulse applied 
at phase t.sub.1 is applied to a picture element maintained at a first 
display state as shown in FIG. 2A. 
In the case of row-subsequent writing system, it is necessary that the 
display state written at phase t.sub.1 is maintained without being 
reversed at phase t.sub.2. Therefore, aa voltage larger than the reverse 
threshold voltage is not to be applied at phase t.sub.2, however, as the 
result of the present inventors' study, the following problem has been 
found. That is, upon changing the pusle polarity from phase t.sub.1 to 
phase t.sub.2, a voltage of -(.alpha.V.sub.0 +.DELTA.V.sub.0) where a 
&lt;.vertline.V.sub.th .vertline./.vertline.V.sub.ON .vertline. and V.sub.th 
is a threshold voltage of the ferroelectric liquid crystal, is 
substantially applied to the liquid crystal layer as shown in FIG. 2B, and 
when -(.alpha.V.sub.0 +.DELTA.V.sub.0) is larger than the reverse 
threshold voltage, the picture element which is to maintain the first 
display state is reversed to the second display state at phase t.sub.2 
resulting in that the desired display can not be formed. 
When a ferroelectric liquid crystal element is prepared, it is practically 
difficult to form a monodomain showing bistability. Nonetheless, it has 
been demanded that an orientation controlling film of high performance be 
capable of not forming multidomain or single stable domain and, further, 
that the formation of monodomain showing bistability be free from 
orientation defect. 
However, when an orientation controlling film for ferroelectric liquid 
crystal reported or published up to now is used, there is a tendency to 
form orientation defects and multidomain portions and single stable 
domain. portions coexist together with bistable domains. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a liquid crystal element 
free from the above-mentioned drawbacks. 
Another object of the present invention is to provide a liquid crystal 
element having a high reliability even though a dyed layer is contained 
therein. 
According to the present invention, there is provided a liquid crystal 
element comprising a cell structure where a liquid crystal is disposed 
between a pair of electrode substrates, a first electrode substate of said 
pair of electrode substrates having a first resin layer formed at the 
surface contacting the liquid crystal of the first electrode substrate by 
thermal curing resulted from dehydration ring closure, the first resin 
layer being able to control orientation of the liquid crystal, and a 
second electrode substrate having a second resin layer formed at the 
surface contacting the liquid crystal of the second electrode substrate by 
thermal curing at a temperature lower than that at which the first resin 
layer is formed, the second resin layer being able to control orientation 
of the liquid crystal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 3 shows a cross sectional view of a liquid crystal display device 
containing a dyed filter layer used in the present invention. 
The embodiment in FIG. 3 uses a twisted nematic (TN) liquid crystal. 1 is a 
polarizing plate, 2 a transparent substrate, 3d a transparent electrode, 4 
an orientation controlling film according to the present invention, 5 a 
sealing material which also functions as a spacer, 6 a liquid crystal, 7a 
and 7b are dyed filter layer, 3a, 3b and 3c are segment type electrodes, 
10 is an orientation controlling film according to the present invention, 
8 a transparent substrate and 9 a polarizing plate or a polarizing plate 
provided with a reflecting plate. 
According to the present invention, dyed layers 7a and 7b are provided on 
transparent electrodes 3a and 3b, respectively, and an orientation 
controlling film 10 which also can function as a protecting layer is 
provided on the dyed layers. As the materials for the dyed layers and 
orientation controlling film, it is not necessary to use particular 
materials of high heat resistance, but materials capable of being easily 
processed and desired colored layers can be selected. This is a feature of 
the present invention. According to the present invention, there is 
preferably used a film produced by heating an orientation film solution 
composed of polyvinyl alcohol and organic titanium at a weight ratio of 
1:2, or more at a temperature not higher than 220.degree. C. for 2 hours 
or less. 
The film thickness is preferably 600-2000 .ANG.. As organic titanium, there 
may be used Ti(OR).sub.4 where R is alkyl such as methyl, ethyl, propyl, 
butyl, amyl and the like, and a chelated titanium such as Ti(OH).sub.2 
[OCH(CH.sub.3)COOH].sub.2. 
As the polyvinyl alcohol used, polyvinyl alcohol having a degree of 
polymerization of 1000-3000 and a degree of saponification of 98-100% is 
preferably employed. 
As another protecting layer, there may be used a polyether amide capable of 
being shaped at a temperature lower than the thermal curing temperature by 
dehydration ring closure, and of good orientation control to the liquid 
crystal, and having a recurring unit of the following Formula (1), 
##STR1## 
where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are selected from hydrogen, 
straight or branched lower alkyl such as methyl, ethyl, propyl, butyl and 
the like, lower alkoxy such as methoxy, ethoxy, propoxy, butoxy and the 
like, and halo such as chloro, bromo and the like; R.sub.5 and R.sub.6 are 
selected from hydrogen and lower alkyl such as methyl, ethyl, propyl and 
the like; and Ar is arylene such as p-phenylene, m-phenylene and the like. 
As an organic solvent for polyether amides, there may be mentioned alcohols 
such as methanol, ethanol, isopropanol and the like, ketones such as 
acetone, methyl ethyl ketone, cyclohexanone and the like, amides such as 
N,N-dimethylformamide, N,N-dimethylacetamide and the like, sulfoxides such 
as dimethyl sulfoxide and the like, ethers such as tetrahydrofuran, 
dioxane, ethyleneglycol monomethyl ether and the like, esters such as 
methyl acetate, ethyl acetate, and the like, halogenated aliphatic 
hydrocarbons such as chloroform, methylene chloride, dichloroethylene, 
carbon tetrachloride, trichloroethylene, and the like, and aromatic 
compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, 
dichlorobenzene and the like. 
As an example of the polyether amide, "HL-1100" (tradename, manufactured by 
Hitachi Kasei K.K.) may be used. 
As an orientation controlling film 4 used for the substrate, a film having 
polyimide bond formed by dehydration ring closure at a high temperature 
may be used. The film may be produced by subjecting a polyamide acid to 
dehydration ring closure at a curing temperature of 220.degree. C. or 
higher and making into a film of, usually, 600-2000 .ANG. and preferably 
800-1500 .ANG.. 
As the polyamide, there may be used polymers having a recurring unit of 
Formula (2) or (3) below: 
##STR2## 
Before forming the polyimide film, there may be formed preliminarily on 
the electrode substrate an organosiloxane film produced with the silane 
coupling agent such as H.sub.2 NC.sub.2 H.sub.4 NHC.sub.3 H.sub.6 
Si(CH.sub.3)(OCH.sub.3).sub.2, H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 
Si(OC.sub.2 H.sub.5).sub.3, H.sub.2 NC.sub.2 H.sub.4 NHC.sub.3 H.sub.6 
Si(OCH.sub.3).sub.3 and the like. The following examples are given for 
illustrating the present invention. 
EXAMPLE 1 
An electrode plate having a transparent electroconductive coating composed 
of indium oxide in a predetermined pattern was coated with a 5% aqueous 
solution of polyvinyl alcohol (manufactured by Nihon Gosei Kagaku K.K.) by 
using a spinner, the polyvinyl alcohol thus coated was then cured, and a 
resist material was applied to the coating following by a predetermined 
patterning and removing the unnecessary polyvinyl alcohol. The electrode 
plate having a pattern of the polyvinyl alcohol film as prepared above was 
soaked in a dyeing bath (a 10 wt.% aqueous solution of a copper containing 
trisazo dye (Sumilite Supra C G L Gray, tradename, produced by Sumitomo 
Kagaku K.K.)) to dye the polyvinyl alcohol film.. To one liter of a 7 wt.% 
aqueous solution of polyvinyl alcohol was added 14 g of an organic 
titanium, Ti(OH).sub.2 [OCH(CH.sub.3)COOH].sub.2, and was sufficiently 
mixed with 0.8 l of ethylene glycol. The resulting mixture was used as an 
orientation liquid, applied to the electrode plate having the dyed layer 
by means of a spinner, and allowed to stand in a clean oven at 200.degree. 
C. to cure. The film thickness of the resulting cured orientation film of 
polyvinyl alcohol was measured by an alpha step film thickness measuring 
instrument (Alpha-step 200, tradename, manufactured by TENCOR INSTRUMENTS 
Co.) and it was 1200 .ANG.. 
To an electrode plate having an electrode pattern (common pattern) which 
paired the above-mentioned electrode pattern (segment pattern) was applied 
an aminosilane coupling agent, a 10 wt/% solution of H.sub.2 NC.sub.2 
H.sub.4 NHC.sub.3 H.sub.6 Si(CH.sub.3)(OCH.sub.3).sub.2 (KBM 602, 
tradename, produced by Shinetsu Kagaku K.K.) in isopropyl alcohol using a 
spinner, cured in an oven, and then a 5 wt.% solution of polyamide acid (a 
condensate of pyromellitic dianhydride and 4,4'-diphenyldiaminoether) in 
N-methylpyrrolidone for forming a polyimide film of Formula (2) above was 
applied to by using a spinner, and allowed to stand in a clean oven at 
300.degree. C. to cure a polyimide film by dehydration ring closure. Then, 
each electrode plate was rubbed in one direction with a felt sheet to 
effect a rubbing orientation treatment. The rubbing direction for the 
electrode plates were perpendicular to each other. Then, the electrode 
plates were adhered with an epoxy type resin adhesive and a nematic liquid 
crystal, "ZLI" (tradename, produced by Merck) was poured into the space 
between the electrode plates followed by sealing, sufficiently washing and 
drying, and then a polarizing plate was adhered to the outside of the 
electrode plate to fabricate a liquid crystal displaying device. 
EXAMPLE 2 
In place of an orientation liquid comprising a mixture of polyvinyl 
alcohol/organic titanium, a polyetheramide type material of Formula (1) 
above, HL-1100 (tradename, produced by Hitach Kasei K.K.) was applied to 
by using a spinner, and then cured at 100.degree. C. for 30 min. When 
measured by an alpha step film thickness measuring instrument, the 
resulting film was 800 .ANG.. Then a cell was fabricated following the 
procedures of Example 1. 
EXAMPLE 3 
Following the procedures of Example 1 except that a dyed layer was formed 
at the side of an electrode substrate having a common pattern, the organic 
titanium/polyvinyl alcohol film used in Example 1 was formed on said 
electrode substrate, and the polyimide film used in Example 1 was formed 
on a segment pattern, there was fabricated a cell. 
COMISON EXAMPLE 1 
Following the procedures of Example 1 except that the organic 
titanium/polyvinyl alcohol film as used in Example 1 was applied to both 
electrode substrates, there was fabricated a cell. 
COMISON EXAMPLE 2 
Following the procedures of Example 1 except that the polyimide film curing 
at 300.degree. C. as in Example 1 was applied to both electrode 
substrates, there was fabricated a cell. 
100 pieces of each of cells fabricated in Examples 1-3 and Comparison 
Examples 1-2 were produced, and the electric current upon applying a 
voltage to each cell was measured at 80.degree. C. and 95% of relative 
humidity at 100 hours, 200 hours, 300 hours and 500 hours, and the number 
of measured electric current of 5 .mu.A or more was investigated. 
Simultaneously the display performance in the display was observed. 
The results are as shown below. 
Standard of Observing the Display Performance 
A: No change is observed. 
B: A minor change is observed. 
C: A distant change is observed. 
TABLE 1 
______________________________________ 
Measurement of Electric Current 
(Number of cells showing 5 .mu.A or more) 
100 hrs. 
200 hrs. 300 hrs. 500 hrs. 
______________________________________ 
Example 1 4 8 9 13 
Example 2 3 6 10 16 
Example 3 3 7 8 12 
Comparison 
20 28 35 57 
Example 1 
Comparison 
4 6 12 21 
Exampe 2 
______________________________________ 
TABLE 2 
______________________________________ 
Liquid Crystal Display Performance 
100 hrs. 
200 hrs. 300 hrs. 500 hrs. 
A B C A B C A B C A B C 
______________________________________ 
Example 1 
71 28 1 70 29 1 68 27 5 67 25 
8 
Example 2 66 33 1 64 33 3 63 30 6 61 28 11 
Example 3 68 30 2 66 31 3 66 30 4 65 30 5 
Comparison 29 65 6 22 58 20 18 47 35 16 48 36 
7 
Example 1 
Comparison 34 61 5 32 55 13 32 46 22 30 38 32 
. 
Example 2 
______________________________________ 
As is clear from the above results, the cell produced in each of the 
examples according to the present invention has improved durability as 
compared with the cells of the comparison examples. In Comparison Example 
1 the electric current value of cell increases and therefore, the 
durability is problematic. In Comparison Example 2, it is considered that 
heating is effected at 300.degree. C. so that the dye is faded by heat and 
it is clear from Table 2 that the display performance is lowered. 
According to the present invention, as the liquid crystal 6, there may be 
used ferroelectric liquid crystals disclosed in U.S. Pat. No. 4,367,794 
other than the above-mentioned TN liquid crystal. In particular, upon 
producing monodomain of a chiral smectic phase of non-spiral structure 
giving bistability, monodomain of good bistability can be obtained when 
the orientation controlling film formed on one electrode substrate is made 
of a cured film produced by a thermal cross-linking reaction and that 
formed on the other electrode substrate is made of a cured film produced 
by a thermal dehydration ring closure reaction. 
In addition, according to the present invention, there may be used a 
ferroelectric liquid crystal showing chiral smectic I, J, K, G or F phase 
as well as chiral smectic C or H phase. 
EXAMPLE 4 
p-Desiloxybenzylidene-p'-amino-2-methylbutyl cynnamate (DOBAMBC) heated 
isotropically was poured into a cell as prepared in Example 1 except that 
the distance between the electrode substrates was 2 .mu.m and the 
direction of rubbing treatment applied to the upper and lower electrode 
substrates was parallel to the corresponding orientation treating axis, 
and then sealed. The cell was gradually cooled at a rate of 2.degree. 
C./hour to effect successively a phase transition from a smectic A phase 
to a chiral smectic C phase resulting in the formation of a chiral smectic 
phase at 63.degree. C. Observation by a polarizing microscope revealed 
that good monodomain showing bistability was formed in the ferroelectric 
liquid crystal cell. 
The ferroelectric liquid crystal cell was repeatedly subjected to the tests 
as mentioned in the previous Examples, and similar results were obtained. 
Tests similar to those in Comparison Examples 1 and 2 were conducted with 
respect to DOBAMBC, and thereby good monodomain was not produced and the 
domain showed only monostability. 
EXAMPLE 5 
Two sheets of a square glass substrate provided with a stripe-like ITO film 
of 62.5 .mu.m wide at a pitch of 100 .mu.m were prepared. One glass 
substrate was set in a vacuum vapor deposition apparatus such that the 
side having the ITO film faced downward, and a copper phthalocyanine 
pigment was deposited. The resulting copper phthalocyanine pigment 
deposited layer to be a color filter was patterned by a predetermined 
photolithographic process. To one liter of a 7 wt.% aqueous solution of 
polyvinyl alcohol was added 14 g of an organic titanium, Ti(OH).sub.2 
[OCH(CH.sub.3)COOH].sub.2, and was sufficiently mixed with 0.8 l of 
ethylene glycol. The resulting mixture was used as an orientation liquid, 
applied to the electrode plate having the color filter by means of a 
spinner, and allowed to stand in a clean oven at 200.degree. C. to cure. 
The film thickness of the resulting cured film of polyvinyl alcohol was 
measured by an alpha step film thickness measuring instrument (Alpha-step 
200, tradename, manufactured by TENCOR INSTRUMENTS Co.) and it was 1200 
.ANG.. 
Then, the surface of the polyvinyl alcohol film was subjected to a rubbing 
treatment with velvet in the direction parallel to the direction of the 
stripe electrode and this was used as "A" electrode plate. 
To the other glass substrate was applied an aminosilane coupling agent, a 
10 wt.% solution of H.sub.2 NC.sub.2 H.sub.4 NHC.sub.3 H.sub.6 
Si(CH.sub.3)(OCH.sub.3).sub.2 (KBM 602, tradename, produced by Shinetsu 
Kagaku K.K.) in isopropyl alcohol by using a spinner, cured in an oven, 
and then a 5 wt.% solution of polyamide acid (a condensate of pyromellitic 
dianhydride and 4,4'-diphenyldiaminoether) in N-methylpyrrolidone for 
forming polyimide film of Formula (2) above was applied to by using a 
spinner, and allowed to stand in a clean oven at 300.degree. C. to cure a 
polyimide film by dehydration ring closure. 
The surface of the polyimide film was subjected to a rubbing treatment with 
velvet in the direction perpendicular to the direction of the stripe 
electrode and this was used as "B" electrode plate. 
A thermosetting epoxy adhesive was applied to the circumference portion of 
A electrode plate except a portion to be a pouring port by a screen 
printing method, and then, A electrode plate was superposed on B electrode 
at a distance of 2 .mu.m held by a spacer such that their stripe pattern 
electrodes were crossed at right angles to each other, that is, the 
orientation treating axes corresponding to the rubbing treatment 
directions, respectively, were parallel to each other. 
Into the cell thus prepared was poured the following liquid crystal 
composition A (showing SmC* at 20 -78.degree. C.) in an isotropic phase 
through a pouring port, which was then sealed. The cell was gradually 
cooled to a low temperature, and kept at 40.degree. C. while a pair of 
polarizers were provided at a cross nicol state. When the state was 
observed by a microscope, it was found that there was a non-spiral 
structure free from orientation defects and there was formed SmC* (chiral 
smectic C phase) of monodomain. 
Liquid Crystal Composition A 
##STR3## 
COMISON EXAMPLE 3 
Repeating the procedures of Example 5 except that the polyvinyl alcohol 
film of A electrode plate used when the liquid crystal element of Example 
5 was produced was omitted, there was produced a liquid crystal cell for 
comparison and thus, SmC* of monodomain was obtained in a similar way. 
Liquid crystal cells of the above-mentioned Example 5 and Comparison 
Example 3 were allowed to stand at 80.degree. C. and relative humidity of 
60% for 96 hours, and resistances of the liquid crystals were measured. 
The results are shown in Table 3 below. 
TABLE 3 
______________________________________ 
Resistance before 
Resistance at 96 hours 
allowing to stand 
after allowing to stand 
______________________________________ 
Example 5 3.1 .times. 10.sup.10 ohm.cm 
3.1 .times. 10.sup.10 ohm. cm 
Comparison 3.1 .times. 10.sup.10 ohm.cm 
2.2 .times. 10.sup.7 ohm. cm 
Example 3 
______________________________________ 
The above-mentioned resistance ohm.cm was measured by applying rectangular 
pulse according to a two frequency method using the circuit of FIG. 4 and 
calculating R.sub.LC (ohm.cm) by the following formula. In the following, 
f.sub.1 =32 Hz, f.sub.2 =64 Hz and V=10 volt. 
##EQU1## 
V: Voltage for measurement f: Frequency of rectangular wave 
I.sub.C : Volue of current of capacitance component 
I.sub.R : Value of current of R component 
C.sub.LC : Capacitance of liquid crystal 
R.sub.LC : Resistance (ohm) of liquid crystal 
C.sub.LC =R.sub.LC S/d 
d: Film thickness of liquid crystal (cell gap) 
S: Electrode area 
Changing f, 
##EQU2## 
Then, after standing for 96 hours, a cross nicol polarizer was fitted to 
each liquid crystal display cell, and a 20 volt signal was applied between 
the electrodes to effect a linear subsequent driving. As a result, in case 
of the liquid crystal cell of the Example of the present invention, a 
display quality having a contrast as good as the initial time while in 
case of the liquid crystal cell of the Comparison Examples any normal 
display was not obtained. The reason is considered that -.DELTA.V.sub.O 
generating upon trailing of the applied pulse is applied to the liquid 
crystal. 
EXAMPLE 6 
In place of the orientation liquid of a mixture of polyvinyl 
alcohol/organic titanium used when A electrode plate of Example 5, HL-1100 
(tradename, produced by Hitachi Kasei K.K.) of polyether amide type 
represented by Formula (1) above was applied by a spinner, and then curing 
was effected at 100.degree. C. for 30 min. The film thickness was 800 
.ANG. when measured by an alpha step film thickness measuring instrument. 
A cell was fabricated following the procedures of Example 5. 
The cell thus fabricated was measured by a method as employed in Example 5 
and a result similar to that of Example 5 was obtained. 
EXAMPLE 7 
Repeating the procedure of Example 5 except that a polyimide film of 
Formula (3) above was used in place of the polyimide film employing for 
producing the B electrode of Example 5, there was fabricated a liquid 
crystal cell. The cell was measured by a method used in Example 5 and a 
result similar to that of Example 5 was obtained. 
According to the constitution of the present invention, at the dyed filter 
layer side it is easy to select the filter material and the orientation 
film. On the contrary, at the other substrate, there is used an 
orientation film of high humidity resistance and high insulating property 
simultaneously with functioning as a protecting film so that a display 
device having a desired colored layer can be produced with a high 
reliability and moreover, the fabrication is easy. 
In addition, it is desirable that the cell is constructed at a temperature 
not higher than 220.degree. C. so as to use the dye for coloring stably, 
and thus the dyed portion can be kept stable for a long time. 
In view of the foregoing, the present invention can give a stable color 
display even when used for a long time as a liquid crystal element for 
color display, in particular, color television display. Particularly, when 
color filter layers are fitted to a conventional dot matrix type liquid 
crystal element using twistic nematic (TN) and a protecting layer as 
mentioned above is omitted, the resistance is lowered in the TN liquid 
crystal layer, but, upon trailing of writing pulse, the display state does 
not become different from that of the writing information. 
On the contrary, in case of FLC the generation of an opposite electric 
field due to discharge of a dielectric member layer upon decrease of the 
writing pulse is attributable to writing with an information different 
from the writing information, and therefore, this is a big problem for 
color display using FLC, but according to the present invention, the 
problem can be effectively solved.