Image forming method, image forming apparatus and method for manufacturing a color filter

A voltage is applied between a first and second electrode, the first electrode being immersed into an aqueous solution in which a group of two or more dyes having different polarities, and including at least one dye able to be independently precipitated from this aqueous solution by an electrochemical reaction, are dissolved and coexist at a specified pH, and the second electrode being provided so as to cooperate with the first electrode in causing the electrochemical reaction, thereby forming a first mixed color image which is composed of the group of dyes, or another mixed color image whose colors are different to those of the first mixed color image and which is composed of the group of dyes, or a single color image which is composed of a single dye on the electrode. Thus, it is possible to realize a high quality image using dyes and safely and simply record an image at a high levels of flexibility. It is also possible to adjust the density of an image easily, and reduce the effects on the environment and energy consumption.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image forming method of using an 
aqueous liquid containing a dye to deposit the dye electrochemically, 
thereby forming an image, an image forming apparatus suitable for the 
image forming method, and a method for manufacturing a color filter using 
the image forming method. 
2. Description of the Related Art 
Methods for recording an image onto a recording medium such as paper based 
on an electric or optical signal, which are currently utilized in printers 
or the like include the dot impact recording method, the thermal transfer 
recording method, the thermal sublimation recording method, the ink jet 
recording method, and the electrophotographic method. These methods are 
roughly classified into three main groups. 
The methods, which are included in the first group are methods of bringing 
a sheet in which dye molecules are dispersed, such as an ink ribbon or a 
donor film, into contact with a medium such as paper and then the dye 
molecules are transferred to the paper by a mechanical impact or heating, 
and include the dot impact recording method, the thermal transfer 
recording method, and the thermal sublimation recording method. In these 
methods, however, consumption articles other than ink and electric power 
are necessary. Energy efficiency is also low, and running costs are high. 
Furthermore, apart from the thermal sublimation recording method, the 
image quality obtained in these methods is poor. 
The methods, which are included in the second group, are non-contact 
methods, and include an ink jet recording method of jetting ink from a ink 
head onto paper. The ink jet recording method does not require consumption 
articles other than ink and electric power. However, it is difficult to 
control the size of the ink dots, the flying direction thereof, or the 
like completely. Moreover, the ink jet recording method is not high in 
energy efficiency. 
The methods, which are included in the third group, are methods of forming 
an image on paper via an intermediate transferring member, and include the 
electrophotographic method, in which toner is adhered onto a latent image 
on a photosensitive member which is formed by laser spots and then this 
latent image is transferred onto paper to form an image. In the 
electrophotographic method, a relatively sharp and fine image can be 
formed. However, in the electrophotographic method, high voltage is 
necessary for forming a latent image on the photosensitive member, 
absorbing the toner by the photosensitive member, and transferring the 
absorbed toner onto paper. Therefore, there occur problems such as a large 
amount of power is consumed and ozone and nitrogen oxides are generated. 
All of the methods in the first, second and third groups also have the 
problem that, in general, the noise of the operation of forming an image 
is quite loud. 
Furthermore, a method is known in which a solution, in which a pigment or a 
dye is dispersed in a polymer having electrodepositing ability, is used to 
form a electrodeposited film, although it is not as common as the 
above-mentioned methods. 
Those of the methods as disclosed in, for example, Japanese Patent 
Application Laid-Open (JP-A) No. 60-23051 (Color Printing Apparatus), 
Japanese Patent Application Laid-Open (JP-A) No. 4-165306 (Method for 
Making a Color Filter), and Japanese Patent Application Laid-Open (JP-A) 
No. 7-5320 (Patterning Method, Electrodepositing-Master for Using the 
Method, and Method for Making a Color Filter And Optical Recording 
Medium). The electrodeposition film formed in these methods contains a dye 
which is fixed inside a polymer film as a supporting matrix. The dye 
content in the ectrodeposition film does not exceed 30%. Therefore, an 
image having only a low density proportional to the energy consumed energy 
can be obtained so as to resulting in problems about energy efficiency and 
cost. Furthermore, in such a method, the same number of dye-applying baths 
as the number of primary colors used in an additive color method or a 
subtractive color method are necessary for obtaining a color image or a 
color filter, and a single electrodeposition step is essential for every 
primary color. 
In view of the above respective properties, an object of the present 
invention is to provide an image forming method in which a dye can be used 
to realize high image quality, and in which the density and color of an 
image can be adjusted, which has excellent safety, is environmentally 
friendly, and has low energy consumption. 
Another object of the present invention is to provide an image forming 
method which makes the electrodepositing operation for obtaining a color 
image easier. 
Still another object of the present invention is to provide an image 
forming apparatus using the above-mentioned image forming method. 
A further object of the present invention is to provide a method for making 
a color filter using the above-mentioned image forming method. 
SUMMARY OF THE INVENTION 
The inventors paid attention to the fact that there are molecules, among 
water-soluble dye molecules, which can be independently precipitated by an 
electrochemical reaction from the aqueous solution in which they are 
dissolved, so as to complete the following present invention. 
The first image forming method according to the present invention comprises 
the step of applying a voltage between a first electrode and a second 
electrode, 
the first electrode being immersed into or brought into contact with an 
aqueous solution in which a group of two or more dyes having same 
polarities, and including at least one dye which can be independently 
precipitated from this aqueous solution by an electrochemical reaction, 
are dissolved and coexist at a specified pH, and the second electrode 
being provided so as to cooperate with the first electrode in causing the 
electrochemical reaction, 
thereby forming on the first electrode a mixed color image which is 
composed of the group of dyes. 
In this method, the dye which can be independently precipitated by an 
electrochemical reaction from the aqueous solution in which it is 
dissolved (the dye is referred to as a dye having a electrodeposition film 
forming ability, hereinafter) is deposited on the first electrode, while 
incorporating the other dyes, to form on the first electrode a mixed color 
image. 
The dyes are provided in the form of an aqueous solution, and do not have 
harmful effects on the environment or the human body. Further, consumption 
articles such as ribbons are unnecessary, except for the dye and electric 
power. The voltage applied in forming an image is only from about 0.6 to 
about 3 V, therefore a very small amount of electric power is consumed. 
Thus, running costs are low. Moreover, a high density, good quality image 
can be obtained, since the image can contain a large amount of dye. In 
this method, the density of an image can also be controlled by controlling 
the voltage between the electrodes or the period of time the voltage is 
applied. 
The second image forming method of the present invention comprises the step 
of applying voltage between a first and second electrode, 
the first electrode being immersed into or brought into contact with an 
aqueous solution in which a group of two or more dyes having different 
polarities, and including at least one dye which can be independently 
precipitated from this aqueous solution by an electrochemical reaction, 
are dissolved and coexist at a specified pH, and the second electrode 
being provided so as to cooperate with the first electrode in causing the 
electrochemical reaction, 
thereby forming, on at least the first electrode, a first mixed-color image 
composed of the group of dyes, or another mixed-color image composed of 
the group of dyes and whose colors are different to those of the first 
mixed-color image, or a single-color image composed of a single dye. 
In the second image-forming method, a first mixed-color image, or another 
mixed-color image whose colors are different to those of the first 
mixed-color image, or a single-color image, and which is composed of the 
group of dyes, is formed on at least the first electrode. The specific 
mechanism of forming the mixed color image is not clear, but it is 
supposed that it occurs when a dye with one polarity is incorporated into 
a dye with a different polarity. 
According to the second image forming method, it is possible to form an 
image having two colors from a single type of solution, reduce the steps 
of forming a color image, and make the operations for forming an image 
simple. It is also possible to adjust the density or color of an image by 
controlling the voltage between the electrodes or the period of time the 
voltage is applied. 
The image forming apparatus according to the present invention comprises: 
a bath for holding an aqueous solution in which a group of two or more 
dyes, including at least one dye which can be independently precipitated 
from this aqueous solution by an electrochemical reaction, are dissolved 
and coexist at a specified pH, 
a first electrode which can be immersed into or brought into contact with 
the aqueous solution, 
a second electrode provided so as to cooperate with the first electrode in 
causing the electrochemical reaction, and 
a voltage applying means for applying voltage between the first and second 
electrodes. 
The apparatus may also comprise a transferring means for transferring the 
image onto a recording medium. 
This image-forming apparatus has the above-mentioned advantages, and makes 
it possible to form a dye image pattern on the electrode, and if desired, 
transfer the dye image onto a medium suitable for one's needs so as to 
form documents. 
According to the color filter formation method of the present invention, a 
color filter can be formed in which an electrodeposited film serving as a 
single color image or a mixed color image is formed on a transparent 
electrode serving as the first electrode, using the above-mentioned image 
forming method. 
This method makes it possible to form a color filter, with the 
above-mentioned advantages. That is, the formation method is greatly 
simplified in comparison to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be explained in detail below. 
In the present invention, there is used an aqueous liquid in which a group 
of two or more dyes are dissolved and coexist at a specific pH value, the 
dyes including at least one dye which can be independently precipitated 
from this aqueous solution wherein the dye is dissolved by an 
electrochemical reaction. 
For example, Rose Bengal and eosin, which are fluorescein type dyes, are 
water-soluble when the pH is 4 or more, but are oxidized to be 
water-insoluble and be precipitated when the pH is lower than 4. 
Similarly, diazo-based, Pro Jet Fast Yellow 2 (manufactured by Zeneca 
Colours Marking Inc.) is water-soluble when the pH is 6 or more, but is 
precipitated when the pH is lower than 6. For reference, FIG. 2 shows the 
absorption spectrum of an aqueous solution of Pro Jet Fast Yellow 2 having 
a concentration of 20 .mu.M. 
When a solution, in which such a dye has been dissolved in pure water, is 
energized (pH 6 to 8), the dye is oxidized to be water-insoluble, thereby 
forming an electrodeposited film composed of the dye molecules on the 
anodic electrode. When a voltage is applied between electrodes so that the 
electrode on which the electrodeposited layer is formed becomes the 
cathode or when this electrode is immersed into an aqueous solution having 
a pH of 10 to 12, the dye in the electrodeposited film is reduced to be 
eluted in the aqueous solution again. For reference, FIG. 3 shows the 
absorption spectrum of an electrodeposited film of Pro Jet Fast Yellow 2 
formed on a transparent electrode of ITO. 
An oxazine type of basic dye Cathilon Pure Blue 5CH (C.I. Basis Blue 3) 
[manufactured by Hodogaya Chemical Co., Ltd.], which is a quinoneimine 
dye, or a thiazine type of basic dye, Methylene Blue (C.I. Basis Blue 9) 
is water-soluble when the pH is 10 or less, but is reduced to be 
water-insoluble and precipitated when the pH is higher than 10. Cathilon 
Pure Blue 5GH is easily dissolved into pure water so as to be present 
therein as a cation, but is water-insoluble and precipitated when the pH 
is 11 or more. For reference, FIG. 4 shows the absorption spectrum of an 
aqueous solution of Cathilon Pure Blue 5GH having a concentration of 20 
.mu.M. 
When such a dye is dissolved in pure water and energized, the dye is 
reduced to form an electrodeposited film composed of the dye molecules on 
the cathodic electrode. When a voltage is applied between the electrodes 
so that the electrode on which the electrodeposited film is formed becomes 
an anode or when this electrode is immersed into an aqueous solution 
having a pH of 8 or lower, the dye in the electrodeposited film is 
oxidized to be eluted in the aqueous solution again. For reference, FIG. 5 
shows the absorption spectrum of an electrodeposited film of Cathilon Pure 
Blue 5GH formed on a transparent electrode of ITO. 
As the dye which can be independently precipitated from the aqueous liquid 
wherein the dye is dissolved, and be used in the present invention (the 
dye is referred to as a "a dye having electrodeposition film forming 
ability" hereinafter), there is used a color former which can exhibit a 
color-developing structure under external stimulation from an acid, a 
base, and the like. Examples thereof include triphenylmethanephthalide, 
phenoxazine, phenothiazine, fluoran, indolylphthalide, spiropyran, 
azaphthalide, diphenylmethane, chromenopyrazole, leucoauramine, 
azomethine, rhodaminelactam, naphtholactam, and triazene types, more 
specifically rose Bengal, Pro Jet Fast Yellow 2, and Cathilon Pure Blue 
5GH. 
The dyes having the chemical structure represented by the general formula 
(1) have the above-mentioned characteristic. 
In the image recording method of the present invention, as the dye which 
can be independently precipitated from the aqueous solution in which the 
dye is dissolved, 
General formula (1): 
##STR1## 
In the general formula (1), Ar.sup.1 and Ar.sup.2 each independently 
represent an aryl or substituted aryl group. At least one of Ar.sup.1 and 
Ar.sup.2 has at least one substituent selected from a --COSH group and a 
--COOH group. J.sup.1 and J.sup.2 each independently represent a group 
expressed by the formulas (1), (2), or (3) shown below. L represents a 
bivalent organic linking group. X independently represents a carbonyl 
group or a group expressed by the formulae (4), (5) or (6). R.sup.1 to 
R.sup.4 each independently represent an alkyl or substituted alkyl group. 
The symbol "n" is 0 or 1. 
##STR2## 
In the formulae (1) to (3), R.sup.5 represents a group selected from H, an 
alkyl group, a substituted alkyl group, an alkoxy group, a halogen atom, 
--CN, a ureido group, and --NHCOR.sup.6 wherein R.sup.6 represents H, an 
alkyl group, a substituted alkyl group, an aryl group, a substituted aryl 
group, an aralkyl group, or a substituted aralkyl group. T represents an 
alkyl group. W represents a group selected from the group consisting of H, 
--CN, --CONR.sup.10 R.sup.11, a pyridinium group, and --COOH; m represents 
an alkylene chain having 2 to 8 carbon atoms; and B represents H, an alkyl 
group or --COOH, in which R.sup.10 and R.sup.11 each independently 
represent an alkyl or substituted alkyl group. 
##STR3## 
In the formulae (4) to (6), Z represents --OR.sup.7, --SR.sup.7, or 
--NR.sup.8 R.sup.9 ; Y represents H, Cl, or CN; and E represents Cl or CN, 
in which each of R.sup.7, R.sup.8, and R.sup.9 represents an alkyl or 
substituted alkyl group, an alkenyl or substituted alkenyl group, an aryl 
or substituted aryl group, an aralkyl or substituted aralkyl group, and 
R.sup.8 and R.sup.9 may constitute a 5 or 6-membered ring together with a 
bonded N atom. 
Specific examples of the dye represented by the general formula (1) 
relating to the present invention are shown below, but the dyes which can 
be used are not limited to the specific examples having the following 
chemical structures. 
Compound (Example-1) 
##STR4## 
Compound (Example-2) 
##STR5## 
Compound (Example-3) 
##STR6## 
Compound (Example-4) 
##STR7## 
Compound (Example-5) 
##STR8## 
Compound (Example-6) 
##STR9## 
Compound (Example-7) 
##STR10## 
Compound (Example-8) 
##STR11## 
Compound (Example-9) 
##STR12## 
Compound (Example-10) 
##STR13## 
Compound (Example-11) 
##STR14## 
Compound (Example-12) 
##STR15## 
Compound (Example-13) 
##STR16## 
Compound (Example-14) 
##STR17## 
Compound (Example-15) 
##STR18## 
Compound (Example-16) 
##STR19## 
Compound (Example-17) 
##STR20## 
Compound (Example-18) 
##STR21## 
Compound (Example-19) 
##STR22## 
Compound (Example-20) 
##STR23## 
Compound (Example-21) 
##STR24## 
Compound (Example-22) 
##STR25## 
Compound (Example-23) 
##STR26## 
Compound (Example-24) 
##STR27## 
Compound (Example-25) 
##STR28## 
Compound (Example-26) 
##STR29## 
Compound (Example-27) 
##STR30## 
Compound (Example-28) 
##STR31## 
Compound (Example-29) 
##STR32## 
Compound (Example-30) 
##STR33## 
As a dye which has no electrodeposition layer forming ability and may be 
used together with a dye having a electrodeposition layer forming ability, 
any ionic dye can be selected. Examples of the ionic dye include acridine, 
azaphthalide, azine, azulenium, azo, azomethine, aniline, amidinium, 
alizarin, anthraquinone, isoindoline, indigo, indigoid, indoaniline, 
indolylphthalide, oxazine, carotenoid, xanthine, quinacridon, quinazoline, 
quinophthalone, quinoline, quinone, guanidine, chrome chelate, 
chlorophyll, ketone imine, diazo, cyanine, dioxazine, bisazo, 
diphenylmethane, diphenylamine, squarilium, spiropyran, thiazine, 
thioindigo, thiopyrilium, thiofluoran, triallyl methane, trisazotriphenyl 
methane, triphenly methane, triphenylmethanephthalide, naphthalocyanine, 
naphthoquinone, naphthol, nitroso, bisazooxadiazole, bisazo, 
bisazostilbene, bisazohydroxyperinone, bisazofluorenone, bisphenol, 
bislactone, pyrazolone, phenoxazine, phenothiazine, phthalocyanine, 
fluoran, fluoren, flugid, perinone, perylene, benzimidazolone, benzopyran, 
polymethine, porphyrin, methine, merocyanine, monoazo, leucoauramine, 
leucoxanthine, and rhodamine type synthesized dyes; and natural dyes such 
as a turmeric, gardenia, red-malt, scallion, grape vine, beet, perilla, 
berry, corn, cabbage, and cacao. 
In the present invention, the pH of the aqueous solution is adjusted so 
that two or more dyes can coexist without producing a complex or 
precipitation. 
When the dyes contained in the aqueous solution have the same polarity 
(that is, are all anionic dyes, or cationic dyes), the above-mentioned 
coexistence can be easily accomplished. 
However, when an anionic or cationic dye aqueous solution (e.g., an aqueous 
solution of anionic Rose Bengal) is mixed with a dye aqueous solution 
containing a polymer compound (e.g., polyethyleneimine) having a polarity 
different from the anionic or cationic dye aqueous solution, they are 
neutralized producing a precipitate. However, since a dye having a 
electrodeposition film forming ability is used in the present invention to 
form an image, a polymer compound is not an essential requirement. Dyes 
having different polarities can also coexist easily in the aqueous 
solution. 
According to the present invention, an aqueous solution in which two or 
more dyes coexist is energized thus forming an image. 
When a mixture solution, in which two dyes having the same polarity are 
mixed, is energized, an electrodeposited film having the same color as 
that of the mixture solution is formed on the electrode having the 
opposite polarity to that of the dyes. When, for example a mixture 
solution of Rose Bengal (red), which is an anionic dye having a 
electrodeposition film forming ability, and Brilliant Blue (blue), which 
is an anionic dye not having this ability, are energized, a purple 
electrodeposited film, which is the same color as the mixture solution, is 
formed on the anode. This is because Rose Bengal is oxidized to be 
deposited on the anode while incorporating the ions of the Brilliant Blue. 
In such a way as described above, a mixed-color image is generally 
obtained if dyes having the same polarity are mixed. As understood from 
this example, it is sufficient if only one dye has the electrodeposition 
film forming ability when two dyes having the same polarity are mixed. 
On the contrary, when a solution, in which two dyes having different 
polarities are mixed, is energized, different images can be formed 
dependently according to the polarity of the voltage applied to 
electrodes. 
When dyes having different polarities are used, it depends on the 
properties of the dyes whether a single-color image is formed or a 
mixed-color image resulting from the mixed dyes is formed. For this 
reason, it is important to combine the optimal dyes for forming an image 
of the desired color. 
In the case of an aqueous solution in which, for example, Pro Jet Fast 
Yellow 2 (yellow), which is an anionic dye having the electrodeposition 
film forming ability, is mixed with Cathilon Pure Blue 5GH (blue), which 
is a cationic dye having the electrodeposition film forming ability, the 
color of the solution is green. This is the color resulting from the 
mixture of these two colors. As shown in FIG. 6A, when this solution is 
energized, the anionic dye A (Pro Jet Fast Yellow 2) is oxidized to be 
deposited on an anode E1 while taking in the cationic dye C (Cathilon Pure 
Blue 5GH), thereby forming an electrodeposited film F1 having the same 
color (i.e., green) as the mixture solution. On the other hand, as shown 
in FIG. 6B, a blue electrodeposited film F2 is formed on a cathode E2. 
This blue color is substantially the same as that of Cathilon Pure Blue 
5GH, i.e., the cationic dye C alone (in forming the film, the light yellow 
results from faded Cathilon Pure Blue 5GH). As understood from this, in 
the case of a mixture solution containing a mixture of two dyes having the 
electrodeposition film forming ability and different polarities, this 
ability of the respective dyes is not lost. When this solution is 
energized, electrodeposited films having different colors can be formed on 
the respective electrodes. In this example, at least one of each of the 
dyes having same polarity has the electrodeposition film forming ability. 
However, only one of the dyes having either polarity may have the 
electrodeposition film forming ability. 
The amount of dye to be deposited on the electrode changes according to 
Faraday's law. Therefore, the thickness of the electrodeposited film can 
be changed successively by controlling at least one of the applied 
voltage, the applied electric charge, or the applied current in forming a 
film, or the length of time any one of them is applied. In other words, 
the density of the electrodeposited film (i.e., the image density) can be 
changed by controlling, for example, the applied voltage. 
In the present invention, the color of the electrodeposited film (i.e., the 
image color) can be changed by controlling, for example, the applied 
voltage. FIG. 7 is a graph showing the relationship between the 
value/polarity of the voltage applied to electrodes and the ratio of the 
Y-peak (see below) to the C-peak, in the present invention method using a 
1:1 mixture solution of Cathilon Pure Blue 5GH and Pro Jet Fast Yellow 2. 
The Y-peak and the C-peak represent the height of the absorption maximum 
point in the absorption spectrum of a Pro Jet Fast Yellow 2 
electrodeposited film, and that in the absorption spectrum of a Cathilon 
Pure Blue 5GH electrodeposited film, respectively (see FIG. 7). FIG. 7 
demonstrates that the ratio of the Y-peak to the C-peak, that is, the 
color of the electrodeposited film can be changed by changing the value 
and the polarity of the voltage applied to the electrodes. 
In the present invention, the total concentration of dyes in a solution is 
usually from 0.1 mM to 1 M. The percentage of each of the dyes is not 
limited. In the case where a dye which does not have the electrodeposition 
film forming ability is included, the ratio of this dye to the dye having 
the ability may be, for example, from 1/99 to 10/1. 
FIGS. 1 and 9 illustrate apparatuses for forming an image on an electrode 
by the method according to the present invention. 
In the apparatus illustrated in FIG. 1, the first and second electrodes 1 
and 2 are connected to a non-illustrated power supply, the electrodes 1 
and 2 being platinum electrodes, and immersed into an aqueous solution 3 
in which two sorts of dyes are dissolved. A saturation calomel electrode 5 
as a reference electrode is immersed into a KCl saturated aqueous solution 
4 electrically connected to aqueous solution 3 through a salt bridge 6. 
The saturation calomel electrode 5 is connected to the power supply 
through a non-illustrated potentiometer. If the aqueous solution 3 is, for 
example a mixture solution of Rose Bengal (red) and Brilliant Blue (blue) 
in this apparatus, when a voltage is applied between the platinum 
electrodes 1 and 2 so that the platinum electrode 1 is an anode, a purple 
electrodeposited film is formed on the platinum electrode 1. If the 
aqueous solution 3 is a mixture of Pro Jet Fast Yellow 2 (yellow) and 
Cathilon Pure Blue 5GH (blue), a green electrodeposited film is formed on 
the platinum electrode which has functioned as an anode, and a blue 
electrodeposited film is formed on the platinum electrode which has 
functioned as a cathode. 
On the contrary, in the apparatus shown in FIG. 9, only the first 
electrode, i.e., the platinum electrode 1 is immersed into the aqueous 
solution 3, and the second electrode, that is, the plutonium electrode 2 
is immersed into a KCl saturated aqueous solution 8 electrically connected 
to the aqueous solution 3 through a salt bridge 7. The platinum electrodes 
1 and 2 are connected to a non-illustrated power supply. The saturation 
calomel electrode 5 as a reference electrode is immersed into the KCl 
saturated aqueous solution 4 electrically connected to a KCl saturated 
aqueous solution 8 through the salt bridge 6. The saturation calomel 
electrode 5 is connected to the power supply through a non-illustrated 
potentiometer. If the aqueous solution 3 is, for example a mixture 
solution of Rose Bengal (red) and Brilliant Blue (blue) in this apparatus, 
when a voltage is app lied between the platinum electrodes 1 and 2 so that 
the platinum electrode 1 is an anode, a purple electrodeposited film is 
formed on the platinum electrode 1. If the aqueous solution 3 is a mixture 
solution of Pro Jet Fast Yellow 2 (yellow) and Cathilon Pure Blue 5GH 
(blue), when a voltage is applied between the platinum electrodes 1 and 2 
so that the platinum electrode 1 is an anode, a green electrodeposited 
film is formed on the platinum electrode 1. When a voltage is applied 
between the platinum electrodes 1 and 2 so that the platinum electrode 1 
is a cathode, a blue electrodeposited film is formed on the platinum 
electrode 1. In this way, dye films of the two colors can be obtained from 
a single type of mixture solution merely by changing the polarity of the 
voltage applied to the electrodes. 
In the apparatuses shown in FIGS. 1 and 9, the voltage applied between the 
electrodes 1 and 2 is usually from 0.6 to 3 V. 
As shown by a substrate 80 in FIG. 10, in order to form an image having two 
colors on the same substrate, it is necessary to beforehand separate a 
surface area of a substrate into an area to which a positive voltage is to 
be applied and an area to which a negative voltage is to be applied. The 
electrode substrate 80 has a supporting body 82 composed of an insulator 
such as glass, and electrodes (e.g., platinum electrodes) 84 in a matrix 
on the supporting body 82. Preferably, the respective electrodes 84 are 
arranged and wired so that the desired positive or negative voltage is 
independently applied to the respective electrodes 84. 
The substrate 80 is used as shown in FIG. 11. That is, the two electrodes 
or areas on the substrate 80 are connected to each other through a direct 
current power supply 81, and the substrate 80 is immersed into an aqueous 
solution 86 in which two or more dyes having different polarities are 
dissolved. When a voltage is applied between the electrodes or the areas, 
two images are simultaneously formed, one of the images being a single 
color image composed of the single dye, and the other being a mixed color 
image composed of the two or more dyes. FIG. 11 illustrates the substrate 
80 wherein the single color image is formed on areas P and the mixed color 
image is formed on areas N. This method uses the same principle that is 
used in the apparatus shown in FIG. 1, and the substrate 80 has the first 
and second electrodes. 
On the other hand, as shown in FIG. 12, a counter electrode 92, two direct 
current power supplies 94 and 95, and a switch 93 are prepared, and then 
the switch 93 is connected to the counter electrode 92, a nd power 
supplies 94 and 95 so that the counter electrode 92 can be connected to 
the negative side of the power supply 94 or the positive side of the power 
supply 95. The positive side of the power supply 94 and the negative side 
of the power supply 95 are connected to an arbitrary electrode or areas on 
the substrate 80, and then the substrate 80 is immersed into an aqueous 
solution in which two or more dyes having different polarities are 
dissolved. When the switch 93 is switched to the side of the power supply 
94, a single color image or a mixed color image is formed on the arbitrary 
electrode or area on the substrate 80. When the switch 93 is switched to 
the side of the power supply 95, a mixed color image or a single color 
image is formed on the arbitrary electrode or area on the substrate 80. 
According to this method, a single color image and a mixed color image can 
be formed successively. In this case, the counter electrode 92 may be 
immersed into the aqueous solution, together with the substrate 80, or be 
immersed into an aqueous solution different from the aqueous solution into 
which the substrate 80 is immersed, by using a salt bridge. In the present 
method, the plurality of electrodes on the substrate 80 and the counter 
electrode 92 correspond to the first electrode and the second electrode, 
respectively. 
According to the present invention, when a transparent substrate is used as 
the electrode in the above-mentioned apparatus, a color filter can be made 
wherein a single or a mixed color electrodeposited film is formed on the 
transparent substrate. 
In the present invention, an image formed on the electrode may be 
transferred onto an image receiving medium such as paper. Conventional 
methods for such transfer include using static electricity, pressure, 
adhesion, chemical bonding force, wettability, or the like to transfer an 
image formed on an electrode by a deposition phenomenon. According to the 
present invention, the two following methods are preferred for 
transferring an image formed on the electrode onto an image receiving 
medium. The first is a method of bringing the electrode having a formed 
image into contact with the image receiving medium and pressing them to 
transfer the image from the electrode to the medium. As shown in FIG. 13, 
the other is a method of arranging the substrate 80 having a formed image 
and the counter electrode 92 so that they face each other, arranging an 
image receiving medium 96 between the substrate 80 and the counter 
electrode 92, and applying a voltage between the electrode 84 and the 
counter electrode 92 so that the polarity of the electrode 84 on the 
substrate 80 will be opposite to the polarity at the time the image film 
was formed. In this method, the dye adhering to the electrode 84 is moved 
toward the counter electrode 92, to transfer the dye onto the image 
receiving medium 96 arranged between the electrode 84 and the counter 
electrode 92. When the image on the electrode has a difference in density, 
that is, light and shade, it is possible to forma transferred image 
corresponding to this image. The density of the transferred image may be 
adjusted by controlling, for example, the applied voltage during the 
formation of an image film and accordingly adjusting the density of the 
image on the electrode, as described above. Alternatively, the density of 
the transferred image may be adjusted by controlling at least one of the 
voltage, the electric charge and the electric current applied in the 
transfer, or the length of time for which they are applied. 
The apparatus according to the present invention may have a means for 
removing any image-constituting particles remaining on the surface of the 
image supporting member (the remaining deposited dye particles) after the 
transfer. The method for removing the particles may be any known method 
including using a blade, a fur brush, an elastic roller, a cleaning web, 
or an air knife. 
FIG. 14 shows the schematic structure of a apparatus for forming an image 
on an electrode and transferring the formed image onto an image receiving 
medium by press. The apparatus shown in FIG. 14 has a roll 115 which can 
rotate along the direction shown by an arrow B. On the outer surface of 
the roll 115, a plurality of the first electrodes are formed which are 
divided into fine sections. Below the roll 115, a bath 114 containing a 
mixture solution 113 of dyes is arranged so that the electrodes positioned 
at the bottom of the roll 115 contact the mixture solution 113 or are 
immersed into the solution 113. The second electrode 112 is immersed into 
the bath 114. A transferring roll 116 is located over the roll 115. A 
paper 117 is fed between both the rolls 115 and 116. A cleaning blade 118 
for removing dyes remaining on the roll 115 is provided at the downstream 
side, which is viewed from the transferring roll 116, of the rotation 
direction of the roll 115. The apparatus of FIG. 14 also has a controller 
119 connected to the respective first electrodes arranged on the outer 
surface of the roll 115, and the second electrode 112. By control of the 
controller 119, a voltage is applied between the first electrodes on the 
roll 115 and the second electrode 112, so that the respective electrodes 
on the roll 115 will independently function as anodes or cathodes. 
In this apparatus, an electrodeposited film 111 formed on the first 
electrodes on the roll 115 is transferred by pressing the transferring 
roll 116 onto the paper 117 fed between the film 111 and the transferring 
roll 116 when the first electrodes on which the film 111 is formed are 
shifted to the top of the roll 115. 
FIG. 15 illustrates the schematic structure of a apparatus for forming an 
image on an electrode and then transferring the formed image onto an image 
receiving medium by applying a voltage. This apparatus is different from 
the apparatus shown in FIG. 14 in that a transferring roll 120 whose outer 
surface is composed of a conductive material is connected to the 
controller 119. In this apparatus, a voltage is applied between the 
electrode on which the electrodeposited film 111 and the transferring roll 
120 so that the polarity of the electrodes will be opposite to its 
polarity at the time an image was formed. Thus, the electrodeposited film 
111 is transferred onto the paper 117. In this apparatus, water having the 
desired pH value may be applied to the paper 117 during the transfer of 
the image. 
As illustrated in FIGS. 14 and 15, images can be formed successively by 
arranging a plurality of the first electrodes on a roll. 
To print a color image having three or more colors according to the present 
invention, an apparatus composed of combination of the apparatus shown in 
FIG. 14 or FIG. 15 with the same apparatus, or an apparatus having a roll, 
two baths containing two different sorts of mixture solutions, each of 
which contains two or more sorts of dyes, and a washing bath containing 
washing water may be used. 
In the present invention, the raw materials of the first and second 
electrodes are not limited, and may be a metal, or an organic or inorganic 
semiconductor. An electrochemically stable material, such as a noble metal 
is preferred, for example, platinum or gold, or carbon. The transparent 
substrate for manufacturing a color filter may be one wherein an electrode 
made of, e.g., ITO or a conductive polymer, is formed on a transparent 
support made of, e.g., glass or a transparent film. 
EXAMPLES 
The following describes the present invention on the basis of specific 
examples. 
Example 1 
In the apparatus shown in FIG. 9, an aqueous solution (pH=7.2) was used 
which was a mixture of a 0.02 M Rose Bengal aqueous solution (red) and a 
0.02 M BRILLIANT BLUE aqueous solution (blue). When voltage was applied 
between the platinum electrodes 1 and 2 for 30 seconds so that the 
potential difference between the saturation calomel electrode 5 and the 
platinum electrodes 1 and 2 was +1.0 V, a purple (a mixed color) thin film 
was formed on the platinum electrode 1. The platinum electrode 1 was 
withdrawn from the aqueous solution, and then, using the apparatus shown 
in FIG. 13 paper was interposed between the counter electrode 92 and the 
platinum electrode 1. When a voltage of -2.0 V was applied between these 
electrodes, an image composed of a purple thin film was formed on the 
paper. 
This example demonstrates that an mixed color electrodeposited film can be 
formed from the mixture solution of a dye having a electrodeposition film 
forming ability and a dye having the same polarity as the first dye but 
not having this ability, and that the image can be transferred onto paper 
by applying a voltage to the first electrode and the counter electrode so 
that the polarity of the first electrode will be opposite to the polarity 
which it had during formation of the film. 
Example 2 
In the apparatus shown in FIG. 9, an aqueous solution (pH=7.2) was used 
which was a mixture of a 0.02 M Pro Jet Fast Yellow (manufactured by 
Zeneca Colour Marking Inc.) aqueous solution (yellow) and a 0.02 M 
Cathilon Pure Blue 5GH (manufactured by Hodogaya Chemical Co., Ltd.) 
aqueous solution (blue). When voltage was applied between the platinum 
electrodes 1 and 2 for 30 seconds so that the potential difference between 
the saturation calomel electrode 5 and the platinum electrodes 1 and 2 was 
become +2.0 V, a green (a mixed color) thin film was formed on the 
platinum electrode 1. The platinum electrode 1 was withdrawn from the 
aqueous solution, and then was brought into contact with paper under 
pressure so as to form an image composed of a green thin film on the 
paper. 
In the apparatus shown in FIG. 9, voltage was applied between the platinum 
electrodes 1 and 2 for 30 seconds so that the potential difference between 
the saturation calomel electrode 5 and the platinum electrodes 1 and 2 was 
-2.0 V, a light yellow thin film was formed on the platinum electrode 1. 
After one minute, the color of the thin layer turned to blue. 
Subsequently, the platinum electrode 1 was withdrawn from the aqueous 
solution, and then was brought into contact with paper under pressure so 
as to form an image composed of a blue thin film on the paper. 
This example demonstrates that images having two colors can be obtained 
from a mixture solution of two sorts of dyes having different polarities 
and that the images can be transferred onto paper by pressure. 
Example 3 
In the apparatus shown in FIG. 9, an aqueous solution was used which was a 
mixture of a 0.02 M Pro Jet Fast Yellow aqueous solution (yellow) and a 
0.02 M Cathilon Pure Blue 5GH aqueous solution (blue). When voltage was 
applied between the platinum electrodes 1 and 2 for 30 seconds so that the 
potential difference between the saturation calomel electrode 5 and the 
platinum electrodes 1 and 2 was +2.0 V, a green (a mixed color) thin film 
was formed on the platinum electrode 1. The platinum electrode 1 was 
withdrawn from the aqueous solution, and then, using the apparatus shown 
in FIG. 13, paper was interposed between the counter electrode 92 and the 
platinum electrode 1. When a voltage of -2.0 V was applied between these 
electrodes, an image composed of a green thin film was formed on the 
paper. 
In the apparatus shown in FIG. 9, volt age was applied between the platinum 
electrodes 1 and 2 for 30 seconds so that the potential difference between 
the saturation calomel electrode 5 and the platinum electrodes 1 and 2 was 
-2.0 V, a blue thin film was formed on the platinum electrode 1. The 
platinum electrode 1 was withdrawn from the aqueous solution, and then, 
using the apparatus shown in FIG. 13, paper was interposed between the 
counter electrode 92 and the platinum electrode 1. When a voltage of +2.0 
V was applied between these electrodes for 30 seconds, an image composed 
of a blue thin film was formed on the paper. 
This example demonstrates that images having two colors can be obtained 
from a mixture solution of two sorts of dyes having different polarities 
and that the image can be transferred on paper by applying a voltage 
between the first electrode and the counter electrode so that the polarity 
of the first electrode will be opposite to the polarity it had during 
formation of the film. 
Example 4 
In the apparatus shown in FIG. 9, in which an ITO electrode formed on a 
glass substrate was used as the first electrode, an aqueous solution was 
used which was a mixture of a 0.02 M Pro Jet Fast Yellow aqueous solution 
(yellow) and a 0.02 M Cathilon Pure Blue 5GH aqueous solution (blue). When 
voltage was applied between the ITO electrode and the platinum electrode 2 
for 30 seconds so that the potential difference between the saturation 
calomel electrode 5 and the ITO electrode/platinum electrode 2 was +2.0 V, 
a green (a mixed color) thin film was formed on the ITO electrode. The 
absorption spectrum of this film at this time is shown in FIG. 16. 
When voltage was applied between the ITO electrode and the platinum 
electrodes 2 for 90 seconds so that the potential difference between the 
saturation calomel electrode 5 and the ITO electrode/platinum electrode 2 
was -1.0 V, a blue thin film was formed on the ITO electrode. The 
absorption spectrum of this film at this time is shown in FIG. 17. 
This example demonstrates that it is possible to form a dye film which can 
be used as a color filter on a transparent electrode. The absorption 
spectra clearly demonstrate that the resultant dye films are different 
depending on the polarity of the applied voltage. 
Example 5 
In the apparatus shown in FIG. 9, an aqueous solution was used which was a 
mixture of a 0.02 M Pro Jet Fast Yellow aqueous solution (yellow) and a 
0.02 M Cathilon Pure Blue 5GH aqueous solution (blue). When voltage was 
applied between the saturation calomel electrode 5 and the platinum 
electrodes 1 and 2 for periods of 20 seconds, so that the potential 
difference between the saturation calomel electrode 5 and the platinum 
electrodes 1 and 2 rose from 0 V to +3.0 V at intervals of +0.5 V, green 
(a mixed color) thin films having different dye densities were formed on 
the platinum electrode 1 depending on the applied voltages. The platinum 
electrode 1 was withdrawn from the aqueous solution, and then was brought 
into contact with paper under pressure so as to form an image composed of 
a green thin film having an image density depending on the applied voltage 
on the paper. 
Subsequently, in the apparatus shown in FIG. 9, when voltage was applied 
between the saturation calomel electrode 5 and the platinum electrodes 1, 
2 for periods of 20 seconds, so that the potential difference between the 
saturation calomel electrode 5 and the platinum electrodes 1 and 2 rose 
from 0 V to -3.0 V at intervals of -0.5 V, blue thin films having 
different dye densities were formed on the platinum electrode 1 depending 
on the applied voltages. The platinum electrode 1 was withdrawn from the 
aqueous solution, and then was brought into contact with paper under 
pressure so as to form an image composed of a blue thin film having an 
image density depending on the applied voltage on the paper. 
This example demonstrates that images having two colors can be obtained 
from a mixture solution of two sorts of dyes, and that the thickness of 
the dye films, that is, the density of the images is changed by the 
applied voltage to obtain transferred images having different image 
density. 
Example 6 
In the apparatus shown in FIG. 9, an aqueous solution was used which was a 
mixture of a 0.02 M Pro Jet Fast Yellow aqueous solution (yellow) and a 
0.02 M Cathilon Pure Blue 5GH aqueous solution (blue). Voltage was applied 
between the saturation calomel electrode 5 and the platinum electrodes 1 
and 2, so that the potential difference between the saturation calomel 
electrode 5 and the platinum electrodes 1 and 2 was +2.0 V. This was 
repeated while the period of time the voltage was applied was increased 
from 0 to 50 seconds at intervals of 10 seconds. As a result, green (a 
mixed color) thin films having different dye densities were formed on the 
platinum electrode 1 depending on the period the voltage was applied for. 
The platinum electrode 1 was withdrawn from the aqueous solution, and then 
was brought into contact with paper under pressure so as to form an image 
on the paper composed of a green thin film having an image density 
depending on the period the voltage was applied for. 
Subsequently, in the apparatus shown in FIG. 9, a voltage was applied 
between the saturation calomel electrode 5 and the platinum electrodes 1 
and 2, so that the potential difference between the saturation calomel 
electrode 5 and the platinum electrodes 1 and 2 was -2.0 V. This was 
repeated while the period of time the voltage was applied for was 
increased from 0 to 50 seconds at intervals of 10 seconds. As a result, 
blue thin films having different dye densities were formed on the platinum 
electrode 1 depending on the period the voltage was applied for. The 
platinum electrode 1 was withdrawn from the aqueous solution, and then was 
brought into contact with paper under pressure so as to form an image on 
the paper composed of a blue thin film having an image density depending 
on the period the voltage was applied for. 
This example demonstrates that images having two colors can be obtained 
from a mixture solution of two types of dyes, and that the thickness of 
the dye films, that is, the density of the images is changed by the period 
of time the voltage is applied to obtain transferred images having 
different image densities. 
Example 7 
In the apparatus shown in FIG. 9, an aqueous solution was used which was a 
mixture of a 0.02 M Pro Jet Fast Yellow aqueous solution (yellow) and a 
0.02 M Cathilon Pure Blue 5GH aqueous solution (blue). When a platinum 
electrode 1 was energized in 10 second periods, so that the electric 
current flowing through the platinum electrode 1 (whose surface area is 2 
cm.sup.2) increased from 0 mA to +10 mA at intervals of +1 mA, green (a 
mixed color) thin films having different dye densities were formed on the 
platinum electrode 1 dependent on the amperage of the energizing electric 
current. The platinum electrode 1 was withdrawn from the aqueous solution, 
and then was brought into contact with paper under pressure so as to form 
an image composed of a green thin film having an image density dependent 
on the amperage of the energizing electric current on the paper. 
Subsequently, in the apparatus shown in FIG. 9, when a platinum electrode 
was energized in 10 second periods, so that the electric current flowing 
through the platinum electrode 1 increased from 0 mA to -10 mA at 
intervals of -1 mA, blue thin films having different dye densities were 
formed on the platinum electrode 1 dependent on the amperage of the 
energizing electric current. The platinum electrode 1 was withdrawn from 
the aqueous solution, and then was brought into contact with paper under 
pressure so as to form an image composed of a blue thin film having an 
image density dependent on the amperage of the energizing electric current 
on the paper. 
This example demonstrates that images having two colors can be obtained 
from a mixture solution of two sorts of dyes, and that the thickness of 
the dye films, that is, the density of the images is changed by the 
amperage of the energizing electric current to obtain transferred images 
having different image densities. 
Example 8 
By sputtering, a substrate 80 shown in FIG. 10 was made which had a 
platinum electrode in a matrix form on a glass base. The electrode on the 
base was separated into an area for marking in a green color (the first 
electrode) and an area for making in a blue color (the second electrode) 
.AS shown in FIG. 11, the first and the second electrodes were connected 
to each other and then the electrodes were immersed into a mixture of a 
0.02 M Pro Jet Fast Yellow (manufactured by Zeneca Colour Marking Inc.) 
aqueous solution (yellow) and a 0.02 M Cathilon Pure Blue 5GH (Hodogaya 
Chemical Co., Ltd.) aqueous solution (blue). When voltage of 4 V was 
applied between the electrodes of both areas for 20 seconds in such a way 
that the electrode of the area for marking in a green color would be an 
anode, a thin film having a green color (a mixed color) was formed on the 
anode. Alternatively, a thin film having a blue color was formed on the 
cathode. After that, the substrate 80 was brought into contact with paper 
under pressure so as to form at the same time a pattern on the paper 
having both green and blue colors, as shown in FIG. 18. 
This example demonstrates that an image having two colors can be obtained 
from a mixture solution of two sorts of dyes by applying a voltage once 
and that an image having two colors can be obtained by a single transfer.