Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2001-05-31
2004-01-13
Norton, Nadine G. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C252S079100, C252S079400, C216S024000, C216S027000
Reexamination Certificate
active
06677243
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing an optical element such as a color filter for operating as a component of a color liquid crystal device to be used typically for a color television, a personal computer, etc. or an electroluminescence element having a plurality of light-emitting layers for full color display by utilizing an ink-jet system.
2. Related Background Art
The demand for liquid crystal displays, color liquid crystal displays in particular, has been increasing in recent years, keeping pace with the technological advancement in the field of personal computers including portable personal computers. However, to further boost the demand, the cost of color liquid crystal displays must be reduced further particularly in terms of the color filters they comprise, because the color filters account for a significant portion of the overall manufacturing cost.
While various techniques have been proposed to date in an attempt to meet the above requirement and also the requirements for improving color filter performance, no satisfactory solution has been found so far. Known methods for preparing color filters will be summarily discussed below.
First, there is a dyeing method. With a dyeing method, a layer of a water-soluble polymer material is formed as a dyeing layer on a transparent substrate and subjected to a patterning operation using photolithography to produce a desired pattern, which is then immersed in a dyeing bath to obtain a colored pattern. The above sequence of operation is repeated three times to produce a colored layer comprising differently colored sections of three colors of R (red), G (green) and B (blue).
Second, there is a pigment dispersion method, for which massive research efforts have been paid in recent years. With a pigment dispersion method, a photosensitive resin layer containing a pigment in a dispersed state is formed on a transparent substrate and then subjected to a patterning operation to obtain a single color pattern. The above sequence of operation is repeated three times to produce a colored layer comprising differently colored sections of R, G and B.
Third, there is an electrodeposition method. With this method, a transparent electrode formed on a transparent substrate is patterned and immersed in an electrodeposition painting solution containing a pigment, resin and electrolytic liquid to electrodeposit a first color. This process is repeated three times to produce a colored layer comprising differently colored sections of R, G and B, which is then baked.
With a fourth method, a pigment is dispersed in a thermosetting-type resin and printed. This process is repeated three times using three different colors of R, G and B, and subsequently the resin is thermally set to produce a colored layer. With any of the above described methods, a protection layer is normally formed on the colored layer.
What is common to all the above-described methods is that a process must be repeated three times for R, G and B, consequently raising the cost. Additionally, any methods involving a large number of steps entail a problematic low yield. Furthermore, in the case of an electrodeoposition method, the profile of the pattern that can be formed by electrodeposition is quite limited, and hence the method is hardly applicable to the process of forming a liquid crystal element of the TFT type (to be used with an active matrix drive method using a TFT (thin film transistor) as switching element).
A printing method is accompanied by a problem of poor resolution and hence hardly applicable to the formation of a pattern having a fine pitch.
As an attempt to avoid the above-identified problems, efforts have been made to develop a method of manufacturing color filters that utilizes an ink-jet system. A manufacturing method using an ink-jet system provides an advantage of a simple manufacturing process and low manufacturing cost.
Additionally, an ink-jet system is applicable to manufacturing not only color filters but also electroluminescence elements.
An electroluminescence element comprises a thin film containing a fluorescent organic or inorganic compound that is sandwiched by a cathode and an anode and is adapted to generate excitons when electrons or holes are injected into the thin film for recombination, so that it can be made to emit light by means of the emission of fluorescence or phosphorescence that occurs when the excitons are deactivated. Thus, an electroluminescence element can be formed by applying a fluorescent material to be used for the electroluminescence element onto a substrate carrying TFT elements formed therein to produce a light-emitting layer there.
The ink-jet system finds applications in the manufacture of optical elements including color filters and electroluminescence elements, because it provides an advantage of a simple manufacturing process and low manufacturing cost as pointed out above. However, the manufacture of optical elements using the ink-jet system is accompanied by problems such as “intermingling of colors” and “blank areas” that are specific to the ink-jet system. These problems will be discussed below in terms of manufacturing color filters.
The problem of “intermingling of colors” arises when inks of different colors are intermingled between any two adjacent pixels (colored sections) showing different colors. With a method of manufacturing color filters, using a black matrix of an appropriate material as partition walls and forming colored sections by applying inks to the respective openings of the black matrix, inks need to be applied by a volume several times to tens of several times greater than the capacity of the openings. If the inks contain solid ingredients such as a coloring agent and a hardening component to a high concentration and hence the volume of inks to be applied is relatively small, the black matrix operates satisfactorily as partition walls and can sufficiently retain inks in the openings so that any applied ink would not flow over the black matrix to reach an adjacent colored section showing a color different from that of the ink. However, on the other hand, if the inks contain solid ingredients only to a low concentration and hence a large volume of ink has to be applied, the applied ink would flow over the black matrix and become intermingled with the other inks in adjacently located colored sections. Particularly, since there is a limit to the viscosity of ink that can be ejected stably from the nozzle of an ink-jet head and also to the concentration of the solid ingredients contained in the inks, a special and cumbersome technique is required to avoid the problem of intermingling of colors.
There have been proposed techniques for preventing intermingling of colors by utilizing the wettability of ink between the colored sections and the partition walls. For instance, Japanese Patent Application Laid-Open No. 59-75205 describes a method of forming an anti-diffusion pattern, using a poorly wettable material, in order to prevent ink from flowing into areas other than target areas. However, the above patent document does not specifically teach how to form such a pattern. On the other hand, Japanese Patent Application Laid-Open No. 4-123005 describes a method of forming partition walls for preventing intermingling of different colors by patterning a silicone rubber layer that is highly water-repellent and oil-repellent. Additionally, Japanese Patent Application Laid-Open No. 5-241011 and Japanese Patent Application Laid-Open No. 5-241012 also disclose methods of forming a silicon rubber layer on a black matrix operating as a light-shielding layer so that it can be used as partition walls for the purpose of preventing intermingling of colors.
With any of the above methods, the ink applied to such an extent that it exceeds by far the height of the partition walls is repelled by the ink-repellent surface layer of the partition walls so that the ink does not flow over the partition walls into any adjacent colored sections, and the intermingli
Iwata Kenichi
Nishida Takehito
Okada Takeshi
Okada Yoshikatsu
Sakamoto Jun-ichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Norton Nadine G.
Umez-Eronini Lynette T.
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