Methods for manufacturing color filters

The invention relates to a method for manufacturing color filters utilizing a color electrodeposition coating which contains an anionic electrodeposition resin having a low acid value. Said method comprises coating a layer of positive photoresist onto a transparent electrically conductive substrate, exposing the substrate under a photomask or photomasks to form regions of different initial levels of exposure energy, exposing the entire surface of the substrate through an energy-incrementing way to, progressively, allow all regions of the substrate to achieve an energy sufficient to completely expose the photoresist on each corresponding region, developing stepwise each region with a same developer solution to cause the electrically conductive substrate of the corresponding region uncovered, electrodepositing said region with a color electrodeposition coating containing an anionic electrodeposition resin having a low acid value to finish the pixel arrangements of the desired colors and completely exposing the substrate. The low acid value anionic electrodeposition resin utilized in the invention has an acid value of 1 to 70 mg KOH/g. The method of the invention shows the advantages of having a high degree of freedom in pattern figures and a wide process window. Moreover, the manufacture color filters of large surface and the perfect yield rate of products are possible.

BACKGROUND OF THE INVENTION 
Flat panel displays (FPD) are products in the photoelectric industry, which 
combine the techniques of semiconductors, optics and chromatics. A trend 
is becoming increasingly recognizable in that FPD is gradually taking the 
place of the traditional cathode ray tubes (CRT). Among various flat panel 
displays, liquid crystal displays (LCD) have assumed a leading position, 
because of their light weight, thinness and capability of becoming a 
full-color display. Color filters are the key elements to render 
glistening and vivid pictures. 
A color filter comprises three main components: a black-hued matrix, a 
color filter layer and an overcoat. Currently, commercial methods for 
manufacturing color filters include: 
(1) dyeing, 
(2) etching, 
(3) pigment dispersion, 
(4) electrodeposition, and 
(5) printing. 
The dyeing method and the etching method primarily utilize dyes as the 
essential filtering materials. The advantages of using dyes as the 
essential filtering materials lie in their variant species, homogeneous 
chroma, high dyeability, high color intensity and high light 
transmissibility. Suitable dyes are disclosed in U.S. Pat. Nos. 4,820,619 
and 4,837,098. Because of the relatively inadequate light and heat 
resistance of the dyeing materials, the methods of dyeing and etching have 
been largely replaced by the pigment dispersion method and the 
electrodeposition method that use pigments as the essential filtering 
materials. Pigments have superior light and heat resistance. One simply 
has to utilize a general pigment dispersion technique to control the 
particle size of the pigment to be less than 0.1 .mu.m, these two methods 
will enable pigments to perform color intensity and light transmissibility 
close to or even the same as dyes perform. Due to the above, the pigment 
dispersion method and the electrodeposition method have become the major 
methods on which industries rely in the manufacture of color filters. 
Pigment dispersion methods, such as those disclosed in U.S. Pat. Nos. 
5,085,973 and 4,786,148 and Japan Laid-Open Patent Publication No. 
60-129739, involve the use of a photosensitive resin well dispersed in 
pigments and a photolithography technique to achieve a high resolution and 
a flexibility of pattern design. This method is currently the major 
manufacturing technique. However, due to the factors that (1) the efficacy 
of the materials is low (1%.about.2%), (2) the trend of applying to large 
sizes corresponding glass substrates is low and (3) the chances of using 
an expensive precisely aligning machine are quite frequent, the cost of 
production for such a method fails to comply with the trends of large 
sizes of color liquid displays and of lower prices. 
Electrodeposition coating processes, such as that disclosed in U.S. Pat. 
No. 4,812,387, use an electrophoresis technique to electrodeposite an 
electrodeposition resin and a pigment which are both well dispersed in 
water onto a patterned transparent electrode substrate. A filter layer of 
a uniform thickness and of a good smoothness is obtained. The 
electrodeposition coating technique is limited in its applications. Owing 
to the design of the electrodes, electrodeposition coating process can 
only use a substrate with a stripe pattern of conductive film for 
implementation. Thus, it is impossible to arrange pixels freely. 
Among all the processes for manufacturing color filters, the printing 
process is the least expensive process. However, it suffers from the 
problems of poor dimensional precision, smoothness and reliability. 
Printing processes are not well accepted by industries for making high 
quality electronic products, but are generally used in the manufacture of 
low-end products. 
To address the problems and at the same time to preserve the advantages of 
pigment dispersion and electrodeposition coating process, Nippon Oil 
Company proposed an electrodeposition lithographic method (ED-litho) for 
making color filters which combined the electrodeposition (ED) coating 
method and the lithographic (litho) technique. As disclosed in U.S. Pat. 
Nos. 5,214,541 and 5,214,542, the contents of which are incorporated 
herein by reference, Nippon Oil Company discloses foremost an 
electrodeposition lithographic method. Said method involves the steps of 
exposing a photoresist layer on a transparent electrically conductive 
layer under a photomask having patterns of more than three different 
degrees of light transmittances for one time to form regions of different 
degrees of exposure energy, using different developer solutions to remove 
the photoresist layer stepwise and electrodepositing progressively the 
red, green and blue colors onto the exposed electrically conductive 
substrate. The electrodeposition lithographic method discussed above has 
several advantages: 
(1) The method combines the techniques of electrodeposition and 
lithography. Therefore, high precision patterns can be obtained, better 
than that obtainable from the electrodeposition coating method; 
(2) The pattern figure has a high degree of freedom, and both stripe and 
non-stripe patterns can be provided; and 
(3) Because it utilizes the advantageous characteristics of an 
electrodeposition process, the coated films exhibit uniform film thickness 
and excellent smoothness. 
However, the electrodeposition lithographic method requires developer 
solutions of at least three different levels of concentrations so as to 
selectively remove the exposed photoresist at different stages of the 
development process and to electrodeposite the colors of red, green and 
blue (R, G, B) thereunto, thus it allows only a relatively narrow process 
window within which tolerance is acceptable. Moreover, it is known to use 
basic aqueous developer solutions for positive photoresist. Under such 
circumstances, there exist only very limited options in selecting an 
appropriate electrodeposition resin. Additionally, there still exists 
photoresist on the substrate before the electrodeposition of all desired 
colors is accomplished. Thus, a culing (hardened) procedure at elevated 
temperature is impossible. In the examples of this reference, a color 
electrodeposition coating comprising an anionic electrodeposition resin is 
used. The acid value of said resin is in the range of from 100 to 500 mg 
KOH/g. Such type of anionic electrodeposition resin is easily influenced 
by developer solutions. Therefore, developer solutions of higher 
concentrations can not be applied. This results in a narrow tolerance of 
developer solutions. Although cationic electrodeposition resins have 
better basic resistance, they show the disadvantages of be easily yellowed 
and having a lower transmission. During the electrodepositing process, 
such type of resin tends to reduce the indium tin oxide (ITO), which is a 
commonly used transparent electrically conductive material of the 
transparent electrically conductive substrate, to black spots. The above 
recited technical limits are believed to be the main reasons why there are 
no commercialized products produced from the process. 
Another method for making color filters which combined a electrodeposition 
(ED) coating method and a lithographic (litho) technique is disclosed in 
U.S. Pat. No. 5,641,595. The contents of said patent are incorporated 
herein by reference. Said method is characterized by utilizing the energy 
accumulate characteristic of positive photoresist in combination with 
light-curable electrodeposition resins. Said process involves the steps of 
coating a layer of positive photoresist onto a transparent electrically 
conductive substrate and exposing the positive photoresist layer to form 
regions of different initial levels of exposure energy. One of the regions 
reaches the full exposure energy of the positive photoresist. After a 
developing step, the photoresist on this region is removed and the 
corresponding electrically conductive substrate is uncovered. Said region 
is then electrodeposited to form the desired colors. When all steps of the 
method are accomplished, the substrate is subjected to an exposing step 
without alignment. The pixels electrodeposited previously are then cured 
by light. This step can avoid the electrodeposited color from being 
attacked by the developer solution used in the next stage. The regions 
which have not accumulated sufficient amounts of energy are subject to 
next exposure to ensure that the energy of the second region reaches the 
full exposure energy of said positive photoresist. After that, each region 
is developed with developer solution and electrodeposited with the desired 
color. Repeat the above steps until the arrangement of all the pixels is 
accomplished. 
This energy incremental process possesses the function of developing the 
regions of different levels of exposure energy progressively. Because the 
method combines the advantages of using the photocurable anionic 
electrodeposited resins, making up the exposure energy to allow each 
region to reach the full exposure energy of the positive photoresist, and 
curing the film formed by the electrodeposition coating, the influence of 
the basic developer solution subsequently used on the electrodeposited 
pixels is eliminated and the developing step is simplified. However, the 
photocurable electrodeposited resins require a sufficient amount of 
exposure energy to cure the electrodeposited coating so as to defend 
against the attack of developer solutions. In order to possess a filtering 
function, pigment particles are dispersed into the electrodeposited 
coating. Thus, the energy need to expose the coating becomes even greater. 
This narrows the exposure tolerance of the photoresist. Moreover, the 
addition of photosensitive groups in the electrodeposited coating enhances 
the difficulty to achieve well dispersion and stability, and adversely 
influences the yield rate of the products. 
The present invention intends to overcome the problems and to preserve the 
advantages of pigment dispersion and electrodeposition coating process for 
manufacturing color filters. The invention develops an excellent technique 
for manufacturing color filters by using a color electrodeposition coating 
containing an anionic electrodeposition resin having a low acid value in 
combination with a weak basic developed positive photoresist. Since the 
present invention utilizes an anionic electrodeposition resin having a low 
acid value in combination with a weak basic developed positive photoresist 
solution, the pixels of the corresponding regions electrodeposited 
previously can be baked at a normal drying temperature so as to defend 
against the attack of developer solutions used subsequently for developing 
other desired colors of pixels without influencing the functions of the 
photoresists. The method of the invention shows the advantages of having a 
high degree of freedom in pattern figures and a wide process window. 
Moreover, the manufacture color filters of large surface and a perfect 
yield rate of products are possible. 
SUMMARY OF THE INVENTION 
The invention relates to a method for manufacturing color filters utilizing 
a color electrodeposition coating which contains an anionic 
electrodeposition resin having a low acid value. Said method comprises 
coating a layer of positive photoresist onto a transparent electrically 
conductive substrate, exposing the substrate under a photomask or 
photomasks to form regions of different initial levels of exposure energy, 
exposing the entire surface of the substrate through an 
energy-incrementing way to, progressively, allow all regions of the 
substrate to achieve an energy sufficient to completely expose the 
photoresist on each corresponding region, developing stepwise each region 
with a same developer solution to cause the electrically conductive 
substrate of the corresponding region uncovered, electrodepositing said 
region with a color electrodeposition coating containing an anionic 
electrodeposition resin having an low acid value to finish the pixel 
arrangements of the desired colors and completely exposing the substrate. 
The low acid value anionic electrodeposition resin utilized in the 
invention has an acid value of 1 to 70 mg KOH/g. 
The method of the invention shows the advantages of having a high degree of 
freedom in pattern figures and a wide process window. Moreover, the 
manufacture color filters of large surface and the perfect yield rate of 
products are possible.

DETAILED DESCRIPTION OF THE INVENTION 
The invention relates to a method for manufacturing color filters 
comprising the steps of: 
(a) coating a layer of positive photoresist onto a transparent electrically 
conductive substrate, and exposing the positive photoresist layer to form 
three or four regions of different initial levels of exposure energy, 
wherein the exposure energy of each region is D.sub.1, D.sub.2, D.sub.3 
(and D.sub.4) progressively, D.sub.1 represents the full exposure energy 
of the positive photoresist, and D.sub.1 &gt;D.sub.2 &gt;D.sub.3 (&gt;D.sub.4); 
(b) using a developer solution to develop and to remove the region of the 
photoresist layer with the exposure energy of D.sub.1 to thereby cause a 
corresponding area of the electrically conductive substrate underlying the 
photoresist to be uncovered, and electrodepositing said region with a 
color electrodeposition coating containing a low acid value anionic 
electrodeposition resin having an acid value of lower than 70 mg KOH/g so 
as to finish the pixel arrangement of a desired color; 
(c) exposing the entire surface of the substrate with an energy IE.sub.n to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.n is the energetic difference between D.sub.n and D.sub.n+1 
and the definition of n is below: 
(i) when three regions of different initial levels of exposure energy are 
formed on the substrate, n is 1 and 2 progressively, or 
(ii) when four regions of different initial levels of exposure energy are 
formed on the substrate, n is 1, 2 and 3 progressively; 
(d) after each time of exposure in steps (c)(i) or (ii), using the same 
developer solution of step (b) to develop and to remove the photoresist of 
the region achieving full exposure to thereby cause the corresponding area 
of the electrically conductive substrate of underlying the photoresist to 
be uncovered, and then electrodepositing said region with a color 
electrodeposition coating containing an anionic electrodeposition resin 
having a low acid value to finish the pixel arrangements of other desired 
colors; 
(e) repeating steps (c) and (d) until all of the pixel arrangements are 
accomplished; and 
(f) forming an overcoat on the substrate. 
The transparent electrically conductive substrate of the invention can be 
selected from the group consisting of oxides of tin, indium and antimony, 
such as indium tin oxide(ITO), and mixtures thereof; or a commercialized 
electrically conductive glass. 
The materials for forming the black-hued matrix can be alloys or oxides of 
chromium, nickel, etc., or mixtures thereof. Alternatively, the black-hued 
matrix can be formed from an organic polymeric coating composition 
containing black pigments dispersed therein. For example, the materials 
can be electrically conductive, such as acrylate resins and epoxy resins, 
or non-electrically conductive. 
The positive photoresist (PR) to be used in the invention can be selected 
from the group consisting of novolak resins and naphthyoquinone diazide 
compounds and the derivatives thereof. Suitable positive photoresists are 
those disclosed in U.S. Pat. No. 5,645,970. The energy-accumulable 
quantity of those materials allows the regions of different initial 
exposure energy to be progressively developed. A positive photoresist 
works based on the principle that its solubility increases after being 
exposed to photoenergy, thus it becomes capable of being developed by a 
basic solution. The precise reliability of patterns of photoresists is 
high and the size accuracy is perfect. Preferably, the photoresist for use 
in the process of the present invention should have high contrast so as to 
minimize the film loss in the unexposed or underexposed areas. 
The techniques for coating photoresists can be any that conventionally 
known to persons skilled in the art such as spraying, dip coating, screen 
printing, roll coating, spin coating. Preferably, the photoresist layer 
has a thickness of 1 to 10 .mu.m, more preferably 1.5 to 5 .mu.m. 
If the photoresist layer form three regions of different degrees of 
exposure energy after exposing, the exposure energy of each region, 
D.sub.1, D.sub.2 and D.sub.3 represents from 100% to 40%, from 85% to 20% 
and from 70% to 0%, respectively. Preferably, each D.sub.1, D.sub.2 and 
D.sub.3 represents from 100% to 70%, from 70% to 40% and from 40% to 0%, 
respectively. If the photoresist layer form four regions of different 
degrees of exposure energy after exposing, the exposure energy of each 
region, D.sub.1, D.sub.2, D.sub.3 and D.sub.4, represents from 100% to 
40%, from 85% to 20%, from 70% to 5% and from 50% to 0%, respectively. 
Preferably, each D.sub.1, D.sub.2, D.sub.3 and D.sub.4, represents from 
100% to 80%, from 80% to 50%, from 50% to 30% and from 30% to 0%, 
respectively. 
The energy of full exposure required in a photoresist manufacture is 
between 80 and 1500 mJ/cm.sup.2. It can be done via a single exposure step 
using a photomask having multiple exposure density. Alternatively, it can 
be accomplished using a photomask having a predetermined exposure pattern. 
By careful movements of the photomask, regions of different degrees of 
exposure energy can be formed on the photoresist. Another alternative 
procedure is to use a plurality (three or four) of photomasks to form the 
desired three regions of different degrees of initial exposure energy 
which can be sequentially developed using the incremental exposure method 
disclosed in the present invention. The regional pattern can be stripe or 
non-stripe (such as mosaic or triangle, etc.) freely arranged one. 
A positive photoresist is typically developed by a basic developer 
solution, such as the aqueous solutions of sodium carbonate, sodium 
hydrogen carbonate, sodium silicate, tetraalkyl amine compounds, sodium 
hydroxide, potassium hydroxide, and mixtures thereof. The concentration of 
the developer solution generally ranges from 0.1 to 10 wt %, preferably 
from 0.2 to 4 wt %. The developing temperature is generally from 
10.degree. to 70.degree. C., preferably from 15.degree. to 40.degree. C. 
The time needed for the developing step is typically from 5 to 600 
seconds. 
Crosslinkable curing agents, organic solvents, neutralization agents and a 
coloring agent consisting of a dye, a pigment, or a mixture thereof can be 
added into the color electrodeposition coating containing an anionic 
electrodeposition resin having a low acid value used in the present 
invention. 
The low acid value anionic electrodeposition resin used in the present 
invention is preferably a polyester resin having carboxyl groups. The 
resin can be dissolved or dispersed in a neutralization agent. Preferably, 
said resin has an acid value of lower than 70 mg KOH/g, preferably from 20 
to 70 mg KOH/g, and a solid content of about 75%. The monomers consisting 
of the polyester resin may comprise those selected from the group 
consisting of neopentyl glycol, adipic acid, isophthalic acid, isodecanol, 
trimellitic anhydrate, butyl cellosolve and 2-butanol. 
The neutralization agent can be selected from the group consisting of 
dimethyl ethanol amine, diethyl ethanolamine, diisopropanolamine, 
triethylamine and the mixtures thereof. Crosslinkable curing agents 
suitably for use in the invention can be selected from the group 
consisting of methylation melamine resin, butylation melamine resin, 
methylation methanol melamine resin, butylation methanol melamine resin, 
benzoguanamine resin. 
The coloring agent of the present invention can be a dye, a pigment, or a 
mixture thereof. Typically, an appropriate dye can be selected from the 
group consisting of azo dyes, anthraquinone dyes, benzodifuranone dyes, 
condensed methine dyes, and mixtures thereof. The pigment can be selected 
from the group consisting of azo lake organic pigments, quinacridone 
organic pigments, phthalocyanine organic pigments, isoindolinone organic 
pigments, anthraquinone organic pigments, thioindigo organic pigments, 
chrome yellow, chrome blue, iron oxide, chrome vermilion, chrome green, 
ultramarine, Prussian blue, cobalt green, emerald green, titanium white, 
carbon black, and mixtures thereof. 
According to the process of the present invention, when three regions of 
different degrees of exposure energy are formed on the substrate, the 
substrate is pre-arranged with black-hued matrixes, and selectively or 
progressively coated with the color electrodeposition coating containing 
red, green and blue. When four regions of different degrees of exposure 
energy are formed on the substrate, a black resin is electrodeposited onto 
the last region (the fourth region) after the color electrodeposition 
coating containing red, green and blue be selectively or progressively 
electrodeposited. The developing and full-exposing steps can be repeated 
until all of the pixels arrangements are accomplished. When all of the 
pixels arrangements are accomplished in accordance with the invention, the 
substrate is preferably baked to allow the electrodeposition resin to be 
cured completely. 
Anionic electrodeposition resins show excellent storage stability (the 
property of not turning yellow), emulsification stability and pigments 
disperibility (in particularly the pigments disperibility at high 
concentration). When anionic electrodeposition resin is used in 
combination with photoresist, there still exists the photoresist on the 
substrate before the electrodeposition of all desired colors is 
accomplished. There is no way to conduct a thermal-curing procedure at 
elevated temperature. For anionic electrodeposition resin, the possibility 
of being attacked by developer solutions used subsequently still exists. 
To avoid such a disadvantage, the invention uses a color electrodeposition 
coating containing an anionic electrodeposition resin having an acid value 
of lower than 70 mg KOH/g in combination with a weak basic developed 
positive photoresist solution. The method of the invention utilizes an 
energy incremental way and develops the photoresist stepwise with 
developer solution of one single concentration. After the corresponding 
region of the electrically conductive substrate is uncovered, the region 
is electrodeposited with a color to arrange the pixel. In a word, the 
present invention is characterized by using an electrodeposition coating 
containing an anionic electrodeposition resin having an acid value of 
lower than 70 mg KOH/g in combination with a positive photoresist 
technique possessing an energy incremental function. For example, the weak 
basic developed positive photoresist solution disclosed in U.S. Pat. No. 
5,645,970 can be used. Therefore, the pixels of the corresponding regions 
electrodeposited previously can be baked at a normal drying temperature 
such as from 80 to 120.degree. C. so as to defend the attack of developer 
solutions used subsequently for developing other desired colors of pixels 
without influencing the functions of the photoresists. 
The method of the invention shows the advantages of having a high degree of 
freedom in pattern figures and a wide process window. Moreover, the 
manufacture color filters of large surface and the perfect yield rate of 
products are possible. 
Each of FIGS. 1A and 1B represents a preferred embodiment in accordance 
with the present invention. Both of the two embodiments are directed to a 
method for making color filters in which the transparent electrically 
conductive substrate has been arranged with a black-hued matrix. Said 
method comprises the following steps: 
1. pre-forming, a black-hued matrix on a transparent electrically 
conductive substrate (2); said black-hued matrix can be made from a 
conductive material or a non-conductive material as shown in (3) of FIG. 
1A(a) and (13) of FIG. 1B(a) respectively; 
2. coating a layer of positive photoresist onto a transparent electrically 
conductive substrate (2) and exposing the photoresist layer under a 
photomask or photomasks to form three regions of different initial levels 
of exposure energy, wherein the exposure energy of each region is D.sub.1 
(5), D.sub.2 (6) and D.sub.3 (7) respectively, wherein D.sub.1 represents 
the full exposure energy of the positive photoresist and D.sub.1 &gt;D.sub.2 
&gt;D.sub.3, as shown in FIG. 1A(a) and FIG. 1B(a); 
3. using a developer solution to develop and to remove the region of the 
photoresist layer with the exposure energy of D.sub.1 (5) to thereby cause 
a corresponding area of the electrically conductive substrate underlying 
the photoresist to be uncovered, and electrodepositing said region with a 
color electrodeposition coating containing an anionic electrodeposition 
resin having a low acid value, namely, conducting the electrodepositing 
arrangement of the first pixel (8), as shown in FIG. 1A(b) and FIG. 1B(b); 
4. exposing the entire surface of the substrate with an energy IE.sub.1 to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.1 is the energetic difference between D.sub.1 and D.sub.2 
in other words, IE.sub.1 =D.sub.1 -D.sub.2), at this moment, the exposure 
energy of the region whose initial exposure energy is D.sub.2 (6) has been 
accumulated to the amount of full exposure (D.sub.2 +IE.sub.1 
=D.sub.1)(6'), and the exposure energy of the region whose initial 
exposure energy is D.sub.3 (7) has not been accumulated to the amount of 
full exposure (only D.sub.3 +IE.sub.1)(7'), as shown in FIG. 1A(b) and 
FIG. 1B(b); 
5. using the same developer solution as that of step 3 to develop and to 
remove the photoresist of the region achieving full exposure (6') to 
thereby cause the corresponding area of the electrically conductive 
substrate underlying the photoresist to be uncovered, and 
electrodepositing said region with a color electrodeposition coating 
containing an anionic electrodeposition resin having a low acid value, 
namely, conducting the electrodepositing arrangement of the second pixel 
(9, 19), as shown in FIG. 1A(c)/(d) and FIG. 1B(c)/(d); 
6. exposing the entire surface of the substrate with an energy IE.sub.2 to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.2 is the energetic difference between D.sub.2 and D.sub.3 
in other words, IE.sub.2 =D.sub.2 -D.sub.3), at this moment, the exposure 
energy of the region whose initial exposure energy is D.sub.3 (7) has been 
accumulated to the amount of full exposure (D.sub.3 +IE.sub.1 +IE.sub.2 
=D.sub.1)(7"), as shown in FIG. 1A(c)/(d)and FIG. 1B(c)/(d); 
7. using the same developer solution as that of step 3 to develop and to 
remove the photoresist of the region achieving full exposure (7") to 
thereby cause the corresponding area of the electrically conductive 
substrate underlying the photoresist to be uncovered and electrodepositing 
said region with a color electrodeposition coating containing an anionic 
electrodeposition resin having a low acid value, namely, conducting the 
electrodepositing arrangement of the third pixel (10, 20) and baking the 
substrate at an elevated temperature to allow the pixels (figures) to be 
cured completely, as shown in FIG. 1A(e) and FIG. 1B(e); 
8. finally, forming an overcoat (11, 21) on the substrate to protect the 
colored filter, as shown in FIG. 1A(f) and FIG. 1B(f). 
FIG. 2 is a schematic diagram showing the various stages of another process 
for manufacturing color filters in accordance with the present invention 
in which the transparent electrically conductive substrate is not been 
arranged with a black-hued matrix. Said method comprises the following 
steps: 
1. coating a layer of positive photoresist onto a transparent electrically 
conductive substrate (2) and exposing the photoresist layer under a 
photomask or photomasks to form four regions of different initial levels 
of exposure energy, wherein the exposure energy of each region is D.sub.1 
(22), D.sub.2 (23), D.sub.3 (24) and D.sub.4 (25) respectively, wherein 
D.sub.1 represents the full exposure energy of the positive photoresist 
and D.sub.1 &gt;D.sub.2 &gt;D.sub.3 &gt;D.sub.4, as shown in FIG. 2(a); 
2. using a developer solution to develop and to remove the region of the 
photoresist layer with the exposure energy of D.sub.1 (22) to thereby 
cause a corresponding area of the electrically conductive substrate 
underlying the photoresist to be uncovered, and electrodepositing said 
region with a color electrodeposition coating containing an anionic 
electrodeposition resin having a low acid value, namely, conducting the 
electrodepositing arrangement of the first pixel (26), as shown in FIG. 
2(b); 
3. exposing the entire surface of the substrate with an energy IE.sub.1 to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.1 is the energetic difference between D.sub.1 and D.sub.2 
namely, IE.sub.1 =D.sub.1 -D.sub.2), at this moment, the exposure energy 
of the region whose initial exposure energy is D.sub.2 (23) has been 
accumulated to the amount of full exposure (D.sub.2 +IE.sub.1 
=D.sub.1)(23'), and the exposure energies of the regions whose initial 
exposure energy is D.sub.3 (24) and D.sub.4 (25) respectively have not 
been accumulated to the amount of full exposure [only (D.sub.3 
+IE.sub.1)(24') and (D.sub.4 +IE.sub.1)(25') respectively], as shown in 
FIG. 2(b); 
4. using the same developer solution as that of step 3 to develop and to 
remove the photoresist of the region achieving full exposure (23') to 
thereby cause the corresponding area of the electrically conductive 
substrate of underlying the photoresist to be uncovered, and 
electrodepositing said region with a color electrodeposition coating 
containing an anionic electrodeposition resin having a low acid value, 
namely, conducting the electrodepositing arrangement of the second pixel 
(27), as shown in FIG. 2(c)/(d); 
5. exposing the entire surface of the substrate with an energy IE.sub.2 to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.2 is the energetic difference between D.sub.2 and D.sub.3 
namely IE.sub.2 =D.sub.2 -D.sub.3), at this moment, the exposure energy of 
the region whose initial exposure energy is D.sub.3 (24) has been 
accumulated to the amount of full exposure (D.sub.3 +IE.sub.1 +IE.sub.2 
=D.sub.1)(24"), however, the exposure energy of the region whose initial 
exposure energy is D.sub.4 (25) has not been accumulated to the amount of 
full exposure (only D.sub.4 +IE.sub.1 +IE.sub.2)(25"), as shown in FIG. 
2(c)/(d); 
6. using the same developer solution as that of step 3 to develop and to 
remove the photoresist of the region achieving full exposure (24") to 
thereby cause the corresponding area of the electrically conductive 
substrate of underlying the photoresist to be uncovered and 
electrodepositing said region with a color electrodeposition coating 
containing an anionic electrodeposition resin having a low acid value, 
namely, conducting the electrodepositing arrangement of the third pixel 
(28), as shown in FIG. 2(c)/(d); 
7. exposing the entire surface of the substrate with an energy IE.sub.3 to 
impart an incremental amount of energy to all regions of the substrate, 
wherein IE.sub.3 is the energetic difference between D.sub.3 namely, 
IE.sub.3 =D.sub.3 -D.sub.4), and D.sub.4, at this moment, the exposure 
energy of the region whose initial exposure energy is D.sub.4 (25) has 
been accumulated to the amount of full exposure (D.sub.4 +IE.sub.1 
+IE.sub.2 +IE.sub.3 =D.sub.1)(25'"), and then using the same developer 
solution as that of step 3 to develop and to remove the photoresist of the 
region achieving full exposure (25'") to thereby cause the corresponding 
area of the electrically conductive substrate of underlying the 
photoresist to be uncovered, and coating said region with a layer of black 
resin, shining a UV light onto the back side of said conductive substrate 
so as to cure the black-hued matrix (29) filled in holes of the region 
under a shielding effect provided by said cured resins (26, 27, 28); the 
kinds of the materials forming the black-hued matrix and the ways to 
produce the same can comprise the following three: (1) employing a 
heat-curable positive photoresist dispersed with black coloring agents and 
using the region which has the less initial exposure energy to form 
black-hued matrix thereon, (2) employing a black electrodeposition resin 
which is of the same type as that contained in the electrodeposition 
coating and utilizing an electrodepositing method to arrange the black 
electrodeposition resin on a electrically conductive substrate, (3) 
employing a photosensitive black electrodeposition resin and baking the 
substrate at elevated temperature to cure the pixels (26, 27, 28) and the 
black-hued matrix (29) completely, as shown in FIG. 2(e); 
8. finally, forming an overcoat (30) on the substrate to protect the 
colored filter, as shown in FIG. 1A(f) and FIG. 2(f). 
The examples of the present invention are described below. It is believed 
that the other purposes, characteristics and advantages of the present 
invention can be more definitely understood through the illustration of 
the examples. 
EXAMPLES 
Example 1 
Synthesis of Polyester Resin Having a Low Acid Value 
Using a conventionally known esterifying condensation polymerization to 
carry out the synthesis of a polyester resin of low acid value. The 
species and amounts of the monomers and solvents used are as below: 
______________________________________ 
Components Amount, wt % 
______________________________________ 
neopentyl glycol 
24.53 
adipic acid 3.25 
isophthalic acid 
7.95 
isodecanol 14.40 
trimellitic anhydrate 
25.81 
buytyl cellosolve 
5.00 
2-butanol 20.00 
______________________________________ 
Place the chemical reagents as indicated above into a reactor. Stir the 
mixture under a nitrogen atmosphere at elevated temperature to carry out 
the reaction. After esterification and dewatering under reduced pressure, 
the polymerization is finished. The analytical results of the resin 
solution obtained are below: 
______________________________________ 
non-volatile components (150.degree. C. 1 hr. wt %) 
75.4 
low acid value (mg KOH/g, solid) 
48.7 
viscosity (25.degree. C., cps) 
45.2 
______________________________________ 
Example 2 
Production of the Electrodeposition Coating Containing Polyester Resin 
Having a Low Acid Value 
The species and amounts of the components of the electrodeposition coating 
containing a polyester resin of low acid value are as below: 
______________________________________ 
Components A-1 A-2 A-3 
______________________________________ 
anionic polyester resin 
95.0 95.0 95.0 
melamine resin Nikarakku .RTM. MX-40) 
8.0 
8.0 
8.0 
2-ethoxy ethanol butyl ether 
25.0 
25.0 
2-ethoxy ethanol ethyl ether 
5.0 
5.0 
neobutanol 18.0 18.0 
18.0 
triethylamine 2.5, 2.5 
2.5 
deionized water 813.5 813.5 
813.5 
phthalocyanine blue (SR-1500) 
-- 
-- 
phthalocyanine green (SAX) 
5.0 
-- 
azo lake pigment (CARMINE FB) 
-- -- 5.0 
total 1000 1000 1000 
______________________________________ 
Use the following steps to prepare the electrodeposition coating containing 
polyester resin having a low acid value: 
1) weight the anionic polyester resin, melamine resin (Nikarakku.RTM. 
MX-40), 2-ethoxy ethanol butyl ether, 2-ethoxy ethanol ethyl ether, 
neobutanol and triethylamine with the amounts shown in the above, place 
the reagents into a container, and mix them under stirring; 
2) weight the pigments with the amounts shown in the above, add them into 
the mixture, and mix them under stirring; 
3) milling-disperse the mixture with a mill, the milling beads used have an 
average particle size of from 0.8 to 1.2 .mu.m; 
4) add deionized water under stirring and emulsify the mixture; and 
5) filter the mixture with a filter of 5 .mu.m. 
Example 3 
A positive photoresist of 2.2 .mu.m thick and corresponding to a weak basic 
developer solution as disclosed in U.S. Pat. No. 5,645,970 was formed on 
an electrically conductive transparent glass substrate, which was measured 
0.7 mm in thickness and contains a pre-arranged black-hued matrix. A 
photomask with merely one-third light-transmitting area was used by 
carefully moving to conduct the energy exposure of 250, 150 and 50 
mJ/cm.sup.2 respectively (100%, 60% and 20%) to form three regions of 
different initial exposure energies. 
A developer solution containing 0.5% Na.sub.2 SiO.sub.3 was used to develop 
and to remove the 250 mJ/cm.sup.2 initial exposure region (i.e., 100% 
initial exposure region). Therefore, a resin containing a red pigment was 
electrodeposited onto the expose surface of the conductive substrate. The 
electrodeposition process was conducted at 25.degree. C. at an electrical 
voltage of 50 V, for 20 seconds. After the electrodeposition process was 
accomplished, the substrate was washed with deionized water and the 
substrate was dried at 90.degree. C. for 10 minute. The entire photoresist 
was then exposed to a light source to receive 100 mJ/cm.sup.2 incremental 
exposure energy. This caused the cumulative exposure energy in the second 
(initially 100 mJ/cm.sup.2, or 60% initial exposure energy) and third 
(initially 50 mJ/cm.sup.2, or 20% initial exposure energy) to raise to 250 
mJ/cm.sup.2 (full exposure) and 150 mJ/cm.sup.2 (60% of full exposure), 
respectively. Similarly, the same developer solution containing 0.5% 
Na.sub.2 SiO.sub.3 was then used to develop and to remove the full 
exposure region. This was followed by electrodepositing under a similar 
condition a resin containing a green pigment onto the expose surface of 
the conductive substrate and which was then dried it. Again, the entire 
photoresist was exposed to a light source to receive another 100 
mJ/cm.sup.2 of incremental exposure energy. This caused the cumulative 
exposure energy in the third to raise to 250 mJ/cm.sup.2 (100% exposure). 
The region was developed and removed using the same developer solution 
containing 0.5% Na.sub.2 SiO.sub.3. This was again followed by 
electrodepositing under a similar condition a resin containing a blue 
pigment onto the expose surface of the conductive substrate. Finally, the 
entire photoresist was exposed to receive another 100 mJ/cm.sup.2 of 
exposure energy then removed using the same developing solution containing 
0.5% Na.sub.2 SiO.sub.3. To ensure complete curing of all the colored 
layers, the whole plate was heated at 260.degree. C. for one hour. The 
arrangement of the three pixels, red, green and blue is finished. 
The foregoing description of the preferred embodiments of this invention 
has been presented for purposes of illustrated and description. Obvious 
modifications or variations are possible in light of the above teaching. 
The embodiments were chosen and described to provide the best illustration 
of the principles of this invention and its practical application to 
thereby enable those skilled in the art to utilize the invention in 
various embodiments and with various modifications as are suited to the 
particular use contemplated. All such modifications and variations are 
within the scope of the present invention as determined by the appended 
claims when interpreted in accordance with the breadth to which they are 
fairy, legally, and equitably entitled.