Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
2000-09-06
2002-12-31
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
C349S106000, C427S164000, C427S165000, C427S595000
Reexamination Certificate
active
06500589
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology for forming a color filter used for a CCD camera, various display elements such as liquid crystal display elements, or a color sensor, and in particular relates to a method for manufacturing a colored layer or black matrix. More particularly, the present invention relates to a method for manufacturing a new color filter which simply forms such a colored layer or black matrix with high resolution.
2. Discussion of the Related Art
Currently, there are well-known methods for manufacturing a color filter include (1) dyeing, (2) pigment dispersion, (3) printing, (4) ink jet, (5) electrodeposition, and (6) micelle electrolysis.
Among these methods, both the dyeing and pigment dispersion methods listed above in (1) and (2) have reached a substantially complete level in terms of technology and have been used for many color solid-state image sensing devices (CCD). However, these two methods require patterning through a photolithography process, thus resulting in increased process steps at higher costs.
On the contrary, the printing and ink jet methods listed above in (3) and (4) do not require any photolithography process. However, the printing method listed above in (3), in which printing is performed on a thermosetting resin dispersed with pigment and then the resin is cured, is inferior in resolution and uniformity of film thickness. The ink jet method listed above in (4), in which a color filter layer is obtained by forming a particular ink recipient layer, making hydrophilic/hydrophobic portions on its surface through an appropriate process, and then discharging an ink onto the hydrophilic portions, has several problems with resolution and positioning accuracy because it may be more likely that an adjacent filter layer will be improperly colored.
In the electrodeposition method listed above in (5), a color filter layer of R.G.B. is obtained by repeating three times an electropainting process in which a high voltage of approximately 70 V is applied to a previously patterned transparent electrode in an electrolytic solution of water-soluble polymer dispersed with pigment to form an electrodeposition film. This method has disadvantages that patterning is limited to particular shapes and it cannot be used for TFT liquid crystal displays because the transparent electrode must have been previously patterned through a photolithography process for use as an electrode for electrodeposition. No additional patterning would be required if a color filter could be formed integrally with pixel electrodes of a TFT liquid crystal substrate through electrodeposition. However, since a prior electrodeposition method used higher electrodeposition voltages, it was very difficult to cause an active-matrix circuit to produce electrodeposits on transparent pixel electrodes and electrodeposition could not be performed using TFT pixel electrodes.
The micelle electrolysis method listed above in (6) is a kind of electrodeposition but oxidation-reduction reaction of ferrocene used as a deposition material allows the electrodeposition voltage to be reduced and a color filter can be integrally formed on a TFT liquid crystal substrate through electrodeposition. However, since a TFT has a larger internal resistance, some voltage can be applied to it but a large current cannot flow through it. Therefore, it is very difficult to form a color filter directly on pixel electrodes through a TFT drive circuit even if the micelle electrolysis method is used. In addition, a thin film formed through the micelle electrolysis method may contain as impurities ferrocene or a surface-active agent, which is essential to the film forming process but may be incorporated into the film during deposition, and thus, the formed color filter may have decreased transparency. This method has further disadvantages that the manufacturing efficiency will be decreased because it may take several tens minutes to perform electrodeposition and that it requires a higher cost because a ferrocene compound, which is a required component for the electrolytic solution, is very expensive. Moreover, any alkali metal that is required as a supporting salt cannot be used because it may adversely affect a TFT circuit or liquid crystal.
Japanese Patent Laid-Open No. 5-5874 (1993) proposes a method for integrally forming a color filter on a TFT substrate. According to this method, a color filter layer with predetermined pixels of predetermined colors is formed through electrodeposition using a TFT drive circuit. Therefore, this method requires an electrodeposition apparatus and the TFT has a very large internal resistance which may cause voltage drop to prevent a necessary current or voltage from being produced for electrodeposition, and thus, additional electrodes for electrodeposition may be required. In addition, the TFT circuit must be protected against an alkali metal contained in the film and the electrodeposition method requires an electrodeposition solution of higher conductivity and addition of a supporting salt, which may contribute to incorporation of impurities as described above. Moreover, since no typical TFT drive circuit can be used to perform electrodeposition directly on pixel electrodes, another type of TFT is required which has a small internal resistance to allow a high current to flow through it. From these reasons, such a usual electrodeposition technology might be considered very difficult to fabricate a color filter using a TFT drive circuit. Thus, no liquid crystal display element of practical level could be implemented by integrally forming a color filter substrate and a TFT substrate. Japanese Patent Laid-Open No. 59-90818 (1984) describes a method for manufacturing a color filter, comprising the steps of: providing on a transparent substrate electrodes consisting of a conductive transparent thin film divided into a plurality of regions; selecting each electrode and applying a voltage to it for electropainting; and repeating the previous steps to color different electrodes with different colors, and the specification also describes that the method is applicable to switching elements such as TFTs. Japanese Patent Laid-Open No. 60-23834 (1985) describes a method for manufacturing a matrix-type multicolor display device which comprises a plurality of gate lines and a plurality of source lines orthogonal to the gate lines with a thin film transistor array formed at each intersection therebetween, which has a substrate with a display electrode comprising a color filter of a plurality of tones and the drain of the thin film transistor connected thereto and an opposed substrate with an overall conductor formed thereon, and which has a display material sandwiched between the transistor array and the transparent conductor, including the steps of: using conductive portions of the color filter and the transistor array as electrodeposition electrodes; selectively forming a colored film on these conductive portions through electrodeposition in a solution which contains at least electrodeposition polymers and colorants dissolved or dispersed therein; and repeating the previous steps. Japanese Patent Laid-Open No. 2-24603 (1990) describes a method for manufacturing a color filter in obtaining a color filter which has a transparent electrode formed on a transparent substrate according to a predetermined pattern and has an organic pigment layer on the transparent electrode, including the steps of: immersing the substrate and an electrolytic electrode in a solution which contains a non-water-soluble organic pigment solubilized in a micelle solution of a surface-active agent; producing a current flow between the predetermined pattern of the transparent electrode and the electrolytic electrode to cause micelle electrode oxidation on the transparent electrode to deposit organic pigment molecules on the transparent electrode; and repeating the previous steps on other transparent electrode patterns with other organic pigments having different spectral char
Akutsu Eiichi
Ohtsu Shigemi
Shimizu Keishi
Tomono Takao
Fuji 'Xerox Co., Ltd.
McPherson John A.
Oliff & Berridg,e PLC
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