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
2003-09-02
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
C422S186300, C349S106000, C205S091000
Reexamination Certificate
active
06613486
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a color filter for CCD cameras, various display devices (e.g., liquid-crystal display devices) and color sensors and a method for forming a colored layer or a black matrix and in particularly relates to a novel method for producing a colored layer and black matrix simply and with high resolution.
2. Discussion of the Related Art
At present, color filters are produced by various methods, e.g., (1) dyeing, (2) pigment dispersion, (3) printing, (4) ink jet, (5) electrodeposition, and (6) micelle electrolysis.
Of these, the methods (1) dyeing and (2) pigment dispersion have been highly developed technically, and widely used for producing color charge-coupled devices (CCDs). One of the major disadvantages involved in these methods is high cost resulting from a number of steps required, e.g., photolithography followed by patterning.
By contrast, the methods (3) printing and (4) ink jet, although needing no photolithography step, have their own disadvantages. For example, the method (3), hardening printed thermosetting resin dispersed with a pigment, gives the product low in resolution and uniformity of thickness. The method (4), treating a specific ink-receiving layer to make it partly hydrophilic and partly hydrophobic, and spraying an ink onto the hydrophilic portion to produce a color filter layer, gives the product low in resolution and positioning accuracy, because of high probability of causing color contamination of the adjacent filter layer.
The method (5) electrodeposition applies a high voltage of around 70 V to a patterned transparent electrode in an electrolytic solution dispersed with a pigment of water-soluble polymer, to form an electrodeposited film for coating. This procedure is repeated 3 times, to obtain a color filter of R.G.B. This method needs the transparent electrode for electrodeposition, which is patterned beforehand by photolithography, and is inapplicable to TFT liquid-crystals because of limited pattern shape. No patterning step may be necessary to effect anew, if the color filter can be monolithically formed by electrodeposition with pixel electrodes on a TFT liquid-crystal substrate. The conventional electrodeposition method, however, needs electrodeposition voltage which is too high to trigger electrodeposition by an active matrix circuit on the transparent pixel electrodes. It is therefore inapplicable to electrodeposition in which a pixel electrode of TFT is used.
The method (6) micelle electrolysis is one type of electrodeposition, which utilizes the redox reaction of ferrocene as the separating material to reduce voltage for electrodeposition, and is applicable to formation of a color filter monolithically with pixel electrodes on a TFT liquid-crystal substrate. However, a TFT to which a voltage can be applied is difficult to pass a large current, because of its high internal resistance. It is therefore difficult even for micelle electrolysis to directly form a color filter on pixel electrodes using a driving circuit for TFT. Moreover, the thin film formed by micelle electrolysis tends to be contaminated with ferrocene, surfactant or the like essential for the forming process, which separate out and are included in the film as impurities, to deteriorate its transparency. Its another disadvantage is high cost, resulting from long electrodeposition time required (several ten minutes) to decrease production efficiency, and use of a high-priced ferrocene compound as the essential electrolytic solution component. In addition, it needs an alkali metal as the prerequisite supporting salt, which may adversely affect the TFT circuit and liquid crystal, making this method inapplicable.
Japanese Patent Laid-Open No. 5-5874 (1993) discloses a method for monolithically forming a color filter on a TFT substrate, which uses a TFT-driving circuit to form a color filter layer of specific color on selected pixels by electrodeposition. This method, therefore, needs an electrodeposition apparatus and special considerations, e.g., use of separate electrodes to compensate for very high internal resistance of a TFT and secure current and voltage required for forming the film by electrodeposition. It is also necessary to protect the TFT circuit from the alkali metal present in the film, which needs to keep the solution high in conductivity for electrodeposition. This, in turn, needs a supporting salt for the solution, which is one of the causes for contamination with impurities. At the same time, a TFT of low internal resistance is needed to transmit a large current, because the conventional TFT-driving circuit is unsuitable for direct electrodeposition on pixel electrodes. The conventional electrodeposition process, involving these technical problems, is difficult to apply to production of color filters using a TFT-driving circuit. As a result, a liquid-crystal display device in which a color filter substrate and TFT substrate are monolithically formed has not been commercialized.
The photocatalytic deposition method, developed by Hoshino et. al. of Chiba University, is known as one type of micelle electrolysis in which photoreactions are used for film-making. This method is described in detail by Hoshino, Katoh, Kurasako and Komon in J. of Photography Society of Japan, vol. 59, No. 2 (1996). It uses the redox reactions of ferrocene to form a film on a section not irradiated with light, and needs an external voltage, complicating the production apparatus. It is therefore unsuitable for forming fine patterns for, e.g., color filters.
It is an object of the present invention to provide a film-making method capable of forming films by a simple process. It is another object of the present invention to provide a method for forming color filters of high numerical aperture and resolution in a well controlled manner, simply and at low cost using the above method. It is still another object of the present invention to provide an electrolytic solution for forming color filters, simple film-making apparatus which needs no electrodeposition apparatus or separate electrode for electrodeposition, and apparatus for producing a color filter.
Japanese Patent Laid-Open No. 59-90818 (1984) discloses a method for forming color filters, in which an electrode of conductive transparent thin film, divided into 2 or more regions, is formed on a transparent substrate, and electrodeposition coating is repeated by applying a voltage to a selected electrode, to coat the electrodes with different colors. It describes that the color filter is applicable to a switching device of, e.g., TFT. Japanese Patent Laid-Open No. 60-23834 discloses a method for forming a matrix type multi-color display, provided with thin-film transistor arrays formed at intersections of gate lines and source lines running perpendicularly to each other; substrate comprising display electrodes each having a color filter of its own color, and connected to drains of the thin-film transistor; and the opposite substrate with an electrical conductor over the entire surface, with a display material sandwiched by the transistor arrays and transparent conductor, characterized in that the color filters and conductive sections on the transistor arrays are used as the electrodes for electrodeposition, and colored films are selectively formed on the conductive sections by repeated electrodeposition with the solution dissolving, or dispersed with, at least an electrodepositing polymer and pigment. Japanese Patent Laid-Open No. 2-24603 discloses a method for forming a color filter, with transparent electrodes formed in a given pattern on a transparent substrate and an organic pigment layer on each transparent electrode, which is obtained by immersing the substrate and electrodes for energizing in a solution with a water-insoluble organic pigment solubilized in an aqueous micelle solution of a surfactant; and forming a given pattern of the transparent electrodes by passing electricity between the electrodes for energizing to effect the
Akutsu Eiichi
Ohtsu Shigemi
Shimizu Keishi
Tomono Takao
Fuji 'Xerox Co., Ltd.
McPherson John A.
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