Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Utilizing electromagnetic wave energy during coating
Reexamination Certificate
1999-05-24
2001-05-01
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Utilizing electromagnetic wave energy during coating
C205S123000, C205S118000, C205S157000, C205S162000, C205S221000, C205S229000, C205S317000
Reexamination Certificate
active
06224735
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for recording an image for producing a color filter used in various display devices, such as a CCD camera and a liquid crystal display device, and a color image sensor, and for recording a fine pattern on various substrates. More specifically, it relates to a process for recording an image by electrochemically depositing an electrodeposition film containing a coloring material.
BACKGROUND OF THE INVENTION
As a process for producing a color filter, a dyeing method, a pigment dispersion method, a printing method, an ink jet method and an electrodeposition method are known at present.
In the dyeing method, a water soluble polymer film is formed on a glass substrate, and the water soluble polymer film is patterned into a desired shape through a photolithography process. The substrate is then immersed in a dyeing solution to obtain a pattern of the dyed water soluble polymer. These steps are repeated for each colors, red (R), green (G) and blue (B), to obtain a color filter layer. The filter thus obtained has a high transmissibility and large variety of colors. Since the dyeing method is highly sophisticated, this method is often used in a color solid state imaging device (CCD). However, this method is inferior in light resistance because a dye is used, and the numbers of steps in the production process are large. Therefore, in recent years, a pigment dispersion method is employed for the production method of a liquid crystal display device (LCD) instead of the dyeing method.
The pigment dispersion method is the recent main stream of the production method of a color filter. In this method, a resin layer having a pigment dispersed therein is formed on a glass substrate, and the resin layer is patterned through a photolithography process. This is repeated for each colors, R, G and B, to obtain a color filter layer. While the pigment dispersion method is sophisticated, it is disadvantageous in that the numbers of steps in the process are large, and the production cost is high.
In the printing method, a step of printing an image on a substrate by using a thermosetting resin having a pigment dispersed therein is repeated for each colors, R, G and B, and the resin on the substrate is hardened by heating, to obtain a color filter layer. In this method, a photolithography process is not necessary in the formation of the R, GandB layers, but the resolution and the uniformity in film thickness are inferior.
In the ink jet method, after an ink receiving layer has been formed on a substrate with a water soluble polymer, a part of the ink receiving layer is treated to be hydrophilic, and the other part is treated to be hydrophobic, followed by spraying an ink to the hydrophilic part, to obtain a color filter layer. In this method, a photolithography process is not necessary in the formation of the R, G and B layers, but the resolution is low because the minimum pixel size is determined by the size of a droplet of the ink. Furthermore, there is a high possibility in this method that droplets of the ink is scattered to produce mixed colors between the filter layers adjacent to each other, and the yield is low.
In the electrodeposition method, a high voltage of about 70 V is applied to a transparent electrode, which has been patterned, in a electrolytic solution having a water soluble polymer and a pigment dispersed therein, to form an electrodeposition film on the electrode. These steps are repeated for each colors, R, G and B, to obtain a color filter layer. In this method, it is necessary to previously pattern the transparent electrode used as an electrode for electrodeposition by photolithography, and it cannot be used for producing a color filter of a TFT liquid crystal display because the shape of the pattern is restricted.
In a color filter of a liquid crystal display, each pixel as a micro-cell generally should be covered with a black matrix, and photolithography is generally employed for producing the black matrix. However, although fine production precision can be obtained by this method, it requires a large number of steps and a large equipment cost, which result in increase in cost. Therefore, a simple process for producing a color filter without using photolithography is demanded.
On the other hand, documents containing color images widely spread throughout society, and a demand for high resolution, is being increased along with the development of a CPU. In order to satisfy the demand, a printing method using light is proposed, and a simple technique is also demanded in production of a color filter.
Various proposals have been made for a method for forming an image by utilizing light. For example, a method for recording an image is reported in H. Yoneyama, et al.,
J. Electrochem. Soc
., p. 2414 (1985), in which pyrrole is electrolytically polymerized by irradiating with light on a Si substrate, and an image is formed by doping and dedoping of the resulting polypyrrole. This method for recording an image using polypyrrole has an advantage in that it can be conducted with a low voltage of 1.0 V or less. However, this method utilizes the color owned by polypyrrole itself and is not suitable for producing a color filter. Furthermore, a thin film cannot be produced by this method. As a method of utilizing light in the production of a color filter, JP-A-5-119209 and JP-A-5-157905 disclose a method, in which a semiconductor maintaining an exposure effect for a certain period (i.e., a semiconductor having a photo-memory property) is irradiated with light, and the semiconductor is immersed in an aqueous electrodeposition solution with applying a voltage of from 20 to 80 V, to obtain a filter layer. This method utilizes an outer photoelectric effect, in which a semiconductor is irradiated with light to increase an electric current that appears on application of a high bias voltage to the semiconductor, so as to increase the conductivity of the semiconductor. However, unevenness in electric current density is liable to be formed, and it is difficult to form a uniform film with good quality.
SUMMARY OF THE INVENTION
The invention has been made in view of the circumstances described above.
An object of the invention is to provide a process for recording an image in which input with light can be conducted, and an image of high quality can be easily recorded.
Another object of the invention is to apply the process for recording an image to a process for producing a color filter in which a photolithography technique is not used, the number of steps on production is small, and the color filter having high resolution and excellent light transmissibility can be produced with good controllability and a low cost.
The inventors have paid attention to the fact that some electrodeposition materials among water soluble polymers have a solubility which quickly changes depending on the change of pH in a solvent . For example, a certain water soluble acrylic resin is dissolved owing to ionic dissociation in a weak alkali solution having a pH of from 8 to 9, but precipitates at a pH of less than 7 since it cannot suffer ionic dissociation. In general, the solubility of polymer materials having a carboxyl group as a hydrophilic group largely change depending on the change in hydrogen ion concentration (pH) even though no structural change is accompanied. For example, some anionic aqueous dispersing agents are dissolved in water at a pH of 8 or more but precipitate at a pH of 5 or less. When these materials are dissolved in a weakly alkaline water, and a voltage is applied to a platinum electrode immersed in the solution, the following reaction of combining a hole (p) and OH
−1
ion takes place on the anode side.
20H
−1
+2p
+
→0.5(O
2
)+H
2
O
In the vicinity of the anode, the amount of hydrogen ion is increased by thus consuming the OH
−1
ion in the aqueous solution, to lower the pH. Accordingly, the solubility of the above-described polymer material is decreased to form an electrodeposition film comprising th
Akutsu Eiichi
Ohtsu Shigemi
Pu Lyong Sun
Fuji 'Xerox Co., Ltd.
Gorgos Kathryn
Keehan Christopher M.
Oliff & Berridg,e PLC
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