Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-05-29
2003-02-25
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C345S107000, C430S032000
Reexamination Certificate
active
06525865
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophoretic display in which a dispersion containing electrophoretic particles is enclosed into a plurality of divided cells partitioned by a bulkhead and to a method for producing the electrophoretic display.
2. Related Art of the Invention
Electrophoretics utilizing electrophoresis phenomenon have been known as devices of non-luminous type. The electrophoresis is a phenomenon where particles (electrophoretic particles) migrate due to a Coulomb's force when applying an electric field to a dispersion composed of liquid (dispersion medium) in which the particles are dispersed.
Fundamentally, the electrophoretic display has two electrodes facing each other at a predetermined length gap and dispersion inserted between the electrodes. When applying a potential difference to both electrodes, charged electrophoretic particles are pulled to either of the electrodes by the electric field generated between the electrodes. The electrode to which the particles are pulled depends on the direction of the electronic field. The dispersion medium is dyed with a dye and the electrophoretic particles are made from pigment particles, with the result that an observer can view the color of either electrophoretic particles or dye. Therefore, from a principle point of view, patterning one of the electrodes and controlling voltage applied to the electrodes enables images to be displayed.
However, since the dispersion is made of liquid, that is, flowing fluid, the electrophoretic particles scatter even when a pattern is made on an electrode, thereby resolution in display being deteriorated. To avoid such a drawback, there has been proposed a technique by a Japanese Patent Publication No. 49-32038. This publication discloses a configuration in which a bulkhead is arranged to enclose dispersion into divided minute cells. Thus electrophoretic particles contained in the dispersion are allowed to move only within each cell.
The above publication fails to disclose, however, how to fill the dispersion into each of the divided cells. Thus, electrophoretics could not be produced based on the configuration disclosed by the above patent publication.
SUMMARY OF THE INVENTION
An object of the present invention, which has been made to overcome such a situation that the conventional technique encounters, is to provide an electrophoretic display and a method for producing the same which are able to fill dispersion into each divided cell.
To achieve the above object, the present invention provides a method for producing an electrophoretic display, the method comprising a process of providing a bulkhead on a substrate so as to partition a space on the substrate into a plurality of divided cells; and a process of ejecting dispersion containing electrophoretic particles toward an opening of the bulkhead as a droplet, to charge the divided cells with the dispersion. In this method, the dispersion is ejected toward an opening of the bulkhead as a droplet, thereby each divided cell being charged with the dispersion. Because the dispersion is ejected into the divided cells as a droplet, the dispersion can be charged in a steady manner even when the divided cells are minute in size. For ejecting droplets of the dispersion, an ink jet type of ejection apparatus can be used. This enables mass production of electrophoretics with greatly shorter pixel pitches and higher fineness in display under high reliability of manufacturing.
In a preferred embodiment, the method for producing an electrophoretic display, comprising a process of providing a bulkhead on a first substrate so as to partition a space on the substrate into a plurality of divided cells; a process of ejecting a dispersion containing electrophoretic particles toward an opening of the bulkhead as a droplet, to charge the divided cells with the dispersion; a process of sealing the opening of the bulkhead with a sealer; and a process of applying a second substrate to the sealed first substrate. In this method, after the dispersion is charged into each divided cell, the opening of the bulkhead is sealed, which makes it possible to securely keep the dispersion within the divided cells. Once charged in the divided cells, there is no fear that the dispersion may leak therefrom. In addition, since no extraneous material is mixed into the dispersion, its intermediate products are easier to handle, thus providing an improved yield.
In the above production method, the method may further comprise processes of forming, on one of surfaces of the first substrate, a plurality of data lines, a plurality of scanning lines, a plurality of switching elements each placed according to each of intersections made between the scanning lines and the data lines, and a plurality of pixel electrodes each electrically connected with each switching element, the processes being carried out before the bulkhead is formed on the one of the surfaces of the first substrate. For instance, thin film transistors can be used as the switching elements. The data lines, scanning lines, and switching elements can be formed on the substrate in the processes of production of the apparatus.
In the above production method, it is preferred that the second substrate is transparent, and the method further comprises a process of forming a transparent common electrode onto the second substrate before the second substrate is applied to the sealed first substrate. This makes it possible to manufacture an active matrix type of electrophoretic display. Further, because both of the common electrode and the second substrate are made to be transparent, the second substrate has a surface on which the common electrode is not formed, so the surface can be used as a display surface.
It may also be configured that conductivity is partly or entirely given to the bulkhead, of which conductive part is used as a common electrode paired with the pixel electrodes. It may also be configured that the sealer may have conductivity and be used as a common electrode paired with pixel electrodes. It may also be configured that the sealing process includes a process of sealing the opening of the bulkhead using a non-conductive sealer employed as the sealer, and a process of giving conductivity to the non-conductive sealer. Moreover, after the opening of the bulkhead is sealed with a non-conductive sealer employed as the sealer, conductivity may be given to the non-conductive sealer, then the sealed first substrate may be applied to the second substrate. These embodiments cause the process to form the common electrode to be omitted.
In the foregoing production method, another alternative is that either one of a plurality of row electrodes or a plurality of column electrodes are formed on one of surfaces of the first substrate, and the other of the plurality of row electrodes and the plurality of column electrodes are formed on the second substrate in advance, wherein the bulkhead is formed onto the one of the surfaces of the first substrate. This method allows one to produce a passive matrix type of electrophoretic display.
For forming the bulkhead by using the foregoing production method, an alternative may be adopted in which, in the ejecting, a material of the bulkhead is ejected toward the first substrate as the droplet, thereby the bulkhead being formed. In this case, an ink jet type of ejecting apparatus can be used as a droplet ejecting apparatus. This enables a bulkhead material to be layered at a desired location with high precision, providing a minutely structured bulkhead.
Further, in forming the bulkhead by using the foregoing production method, it is preferred that the bulkhead is formed by pressing a material of the bulkhead with a stamper. This method makes it possible to manufacture finely structured bulkheads with higher productivity.
In the foregoing production method, an alternative may be configured such that a plurality of data lines, a plurality of scanning lines, a plurality of switching elements each placed according to each
Seiko Epson Corporation
Spector David N.
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