Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-09-26
2003-04-01
Mack, Ricky (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C345S107000
Reexamination Certificate
active
06542284
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device and manufacturing methods therefor, and more particularly, relates to an electrophoretic display device wherein a display is created by causing the migration of charged color particles in a liquid by a voltage applied to electrodes, and a manufacturing method therefor.
2. Description of the Related Art
Recently, concomitant with the progress of information devices, data volume of various information has been increasing rapidly, and in addition, output of information has been performed in various forms. In general, the output of information can be roughly classified into a screen display using a display device, such as a cathode ray tube or a liquid crystal panel, and a hard-copy display printed on paper by a printer or the like. In the screen display, the need for a thinner display device having a low power consumption has been growing, and above all, a liquid crystal display device has been actively developed and commercialized as a display device which can fulfill the need describe above. However, for the current liquid crystal display devices, problems have been encountered in that letter images displayed on the screen are difficult to view depending on a viewing angle or reflection and, in addition, eyestrain caused by a flickering light source, low luminance, and the like has not been satisfactorily solved. In addition, a screen display using a cathode ray tube has a similar or superior contrast and luminescence compared to a liquid crystal display; however, since a flicker may be generated in a screen display device, the display quality cannot be similarly compared to the hard-copy display described later. In addition, the device using a cathode ray tube is large and heavy, and hence, the portability thereof is significantly inferior.
It has been believed that the hard-copy displays would have disappeared due to computerized information processing; however, a significant amount of hard-copy output has been used in practice. The reason for this is that when information is displayed on a screen, in addition to the problems relating to the display quality described above, the resolution is generally up to 120 dpi (dots per inch) and is considerably inferior to a printout on paper (generally, 300 dpi or more). Accordingly, eyestrain is larger for the screen display compared to the hard-copy display. As a result, even when information can be viewed by the screen display, a hard-copy output is frequently performed. In addition, another important reason the hard-copy display is used even though the screen display can be used is that once hard-copy information is output, a great deal of information can be laid out without being restricted by the size of a screen as in the case of the screen display, and the information thus laid out can be rearranged and can be read one by one without performing a complicated device operation. Furthermore, the hard-copy display has a superior portability since no energy is required for retaining the display, and as long as the volume of information is not significantly large, the information can be read at any time and at any place.
As described above, as long as a movie display or a frequent rewrite is not required, the hard-copy display has various features different from the screen display; however, there is a shortcoming in that a large amount of paper is consumed for a hard copy display. Accordingly, in recent years, development of rewritable recording media (recording media in which a number of cycles of recording and erasing a high visibility image can be performed, and no energy is required for retaining the image thereon) has been actively advancing. A rewritable third display method which successively possesses the features of the hard-copy display described above is referred to as a paper-like display.
Requirements for the paper-like display are rewritable, no energy consumption for retaining an image or a significantly small energy consumption therefor (memory retaining characteristic), superior portability, superior display quality, and the like. As a display method which is currently regarded as the paper-like display, for example, there may be mentioned reversible display media using a matrix system formed of a low molecular resin or a high molecular resin (disclosed in, for example, Japanese Unexamined Patent Application Publication Nos. 55-154198 and 57-82086), which performs recording/erasing by using a thermal printer head. The system described above is used for display portions of some prepaid cards; however, there are problems in that the contrast is not so high, the number of repeatable cycles of recording/erasing is relatively small, such as 150 to 500 times, and the like.
As another display method which can be used as the paper-like display, an electrophoretic display device (U.S. Pat. No. 3,612,758) invented by Harold D. Lees, et al. has been known. In addition to the patent mentioned above, Japanese Unexamined Patent Application Publication No. 9-185087 also discloses an electrophoretic display device.
FIGS. 7A and 7B
are views showing the structure and the operation principle of these electrophoretic display devices mentioned above. This display device includes a pair of substrates
1
and
2
disposed with a predetermined spacing therebetween, and electrodes
3
and
4
formed on the substrates
1
and
2
, respectively. The display surface is a side indicated by the arrow B, and the electrode
4
provided at the display surface side is transparent. In addition, between the two substrates
1
and
2
, there are provided a number of charged color particles
5
which are positively charged and are also colored in this case; an insulating liquid
6
which is colored by a dye dissolved therein so as to have a different color from that of the charged color particles; and partitions
13
which divide the spacing described above into a number of sections in the direction along the surface of the substrate so as to prevent the charged color particles from being localized and to define the spacing between the substrates.
In the display device described above, as shown in
FIG. 7A
, when a negative voltage is applied to the electrode
3
shown at the lower side in the figure, and in addition, a positive voltage is applied to the electrode
4
at the upper side in the figure, the charged color particles
5
which are positively charged are gathered so as to cover the electrode
3
at the lower side, and when this display device is viewed along the B direction in the figure, a display having the same color as that of the insulating liquid
6
is created.
In contrast, as shown in
FIG. 7B
, when a positive voltage is applied to the electrode
3
shown at the lower side in the figure, and in addition, a negative voltage is applied to the electrode
4
at the upper side in the figure, the charged color particles
5
which are positively charged are gathered so as to cover the electrode
4
at the upper side, and when this display device is viewed along the B direction in the figure, a display having the same color as that of the charged color particles
5
is created. When this operation described above is performed in each pixel unit, an optional image can be displayed by a number of pixels.
The display device shown in
FIGS. 7A and 7B
creates a display by causing the migration of the charged color particles in the direction perpendicular to the surface of the substrate in accordance with a voltage applied between the electrodes provided on the pair of substrates opposing each other. In addition to this display device, a display device disclosed in Japanese Unexamined Patent Application Publication Nos. 49-5598 and 11-202804 has been proposed in which a pair of electrodes, i.e., a first display electrode and a second display electrode, is disposed on the same substrate, and charged color particles are moved in the direction parallel to the substrate when viewed from an observer side. This display device described above create
Fitzpatrick ,Cella, Harper & Scinto
Mack Ricky
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