Glass manufacturing – Processes – With shaping of particulate material and subsequent fusing...
Reexamination Certificate
1999-12-10
2002-07-02
Fiorilla, Christopher A. (Department: 1731)
Glass manufacturing
Processes
With shaping of particulate material and subsequent fusing...
C427S162000, C427S163300, C427S190000, C427S510000
Reexamination Certificate
active
06412305
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of flat panel displays, and in particular, to the manufacture of opaque rib structures for plasma addressed liquid crystal (PALC) displays.
BACKGROUND INFORMATION
Flat panel displays, e.g., liquid crystal displays, are known. Recently, the use of plasma channels to address a liquid crystal display (LCD) has become known. For example, U.S. Pat. Nos. 4,896,149, 5,036,317, 5,077,553, 5,272,472, 5,313,223, the disclosures of which are all hereby incorporated by reference, each disclose such a structure. This type of display technology provides an active addressing matrix suitable for high-line-count displays, and is a competitive alternative to the known thin-film transistor (TFT) active matrix approach.
These plasma channel panels are also referred to herein as plasma addressed liquid crystal (PALC) displays. This type of plasma display panel is generally formed of two parallel substrates separated from each other to form a discharge space between the substrates, which is filled with a discharge gas, such as a mixture of helium, neon and xenon. The inner-facing surface of each of the substrates bears a pattern of spaced parallel electrodes, with the electrodes on one substrate being oriented, for example, in a direction orthogonal to the direction of the electrodes on the other substrate. The electrode bearing surfaces of the substrates are typically covered with a dielectric layer, and red, green and blue phosphors are separately located in discrete areas on the internal surface of the dielectric layer on one of the two substrates. The dielectric layers are generally lead-based glass frits fired between 500 and 600° C., depending on their formulation and the level of uniformity required. The displayed picture is produced by plasma discharges which are induced locally in the gas by applying a suitable voltage between the electrodes of one substrate and the electrodes of the other substrate. Ultraviolet light emitted locally by the gas discharge induces luminescence of the neighboring phosphors.
A PALC display relies on the highly non-linear electrical behavior of a relatively low pressure (e.g., 10 to 100 Torr) gas, e.g., He, confined in parallel channels. A cross section of a portion of a PALC display
100
is shown in
FIG. 1. A
pair of parallel electrodes
101
A (anode) and
101
C (cathode) is deposited in each channel
102
on a rear glass plate
101
G, for example, forming the bottom of the channels, and a very thin dielectric sheet
103
, e.g., a glass micro-sheet of about 50 &mgr;m thickness, forms the top of the channels
102
. A liquid crystal layer
104
on top of the micro-sheet
103
is the optically active portion of the display
100
. A cover sheet
105
, e.g., a passive glass plate of about 1.1 mm, with transparent conducting electrodes, e.g., made from indium-tin oxide (ITO), running perpendicular to the plasma channels
102
, lies on top of the liquid crystal
104
. Conventional polarizers
106
, color filters
107
, and back lights
108
, like those found in other conventional liquid crystal displays, are also commonly used, as illustrated.
When voltages are applied to the transparent electrodes, since there is no ground plane, the voltages are divided among the liquid crystal, the micro-sheet, the plasma channel, and any other insulators intervening between the transparent electrode and whatever becomes the virtual ground. As a practical matter, this means that if there is no plasma in the plasma channel, the voltage drop across the liquid crystal will be negligible, and the pixels defined by the crossings of the transparent electrodes and the plasma channels will not switch. If, however, a voltage difference sufficient to ionize the gas is first applied between the pair of electrodes in a plasma channel, a plasma forms in the plasma channel so that it becomes conducting, and constitutes a ground plane. As a result, for pixels atop this channel, the voltages will be divided between the liquid crystal and the micro-sheet only. This places a substantial voltage across the liquid crystal and causes the pixel to switch. Igniting a plasma in the channel causes the row above the channel to be selected. Because the gas in the channels is non-conducting until a well-defined threshold voltage between the electrode pair is reached, the rows are extremely well isolated from the column voltages unless selected. This high non-linearity allows large numbers of rows to be addressed without loss of contrast.
In order to avoid luminous cross-talk between neighboring regions and improve the contrast in such displays, opaque barrier ribs
110
are disposed on at least one of the substrates (typically the rear one) forming electrically insulated discharge cells. The barrier rib structure is typically periodic with a pitch of, for example, from 200 &mgr;m to 400 &mgr;m, depending on the panel resolution. These ribs are, for example, about 30-100 &mgr;m wide and 100-200 &mgr;m thick (i.e., high).
Alternatively, a closed cell design has been employed having square cells which are about 200-400 &mgr;m on each side. The “ribs” which form these square cells are about 30 &mgr;m to 70 &mgr;m wide and about 30 to 200 &mgr;m high. Plasma panels of this type are described, for example, in U.S. Pat. No. 4,853,590, as well as Japanese Patent Application Nos. J04255638 and J04075232. The networks of parallel barrier ribs mentioned above delimit columns of pixels which can be addressed independently. The two perpendicular networks of electrodes allow ionization of the gas at the selected pixels. The ultraviolet radiation emitted by the ionized gas causes the excitation of areas of phosphorescent products associated with said pixels according to the configuration of an image which is to be displayed.
In the past, the barrier ribs have typically been made either by a silk-screening method, or by sandblasting from a deposited layer of frit. Related co-pending U.S. application Ser. No. 08/820,206, referenced above, discloses micro-molding processes for making the barrier ribs. One disadvantage associated with these micromolding methods, particularly when depositing opaque rib materials, is the possibility of depositing a thin film of opaque material on the glass substrate between rib structures. Conventional screen printing and photolithography-based methods typically avoid residual film formation between the ribs. However, for low cost processes in which it is desirable to limit the number of printing steps, screen printing and photolithography-based methods are limited to producing low thickness ribs, e.g., about 20 microns. Conventional methods, however, typically use solvent based materials which can cause difficulties in maintaining rib shapes, particularly high aspect ratio ribs, usually requiring additional consolidation steps to maintain rib shape. Accordingly, a need exists for improved methods of manufacturing opaque rib structures for PALC displays.
SUMMARY OF THE INVENTION
This invention provides novel methods for making opaque rib structures for flat panel displays that utilize micro-molding techniques but that do not leave a residual film of opaque material between the rib structures. The invention also provides improved micromolding methods that result in improved structures and lower manufacturing costs.
According to an aspect of the invention, a method of manufacturing opaque rib structures for use in a flat panel display, such as a plasma addressed liquid crystal (PALC) display, includes providing a substrate and an intaglio collector having cavities formed in its surface complimentary to the desired size and spacing of the barrier ribs. A hardenable glass paste which includes a glass frit and a hardenable, settable or curable medium (hereinafter referred to collectively as “curable”), e.g., an ultra-violet sensitive medium, is provided into the collector cavities to define rib structures. Useful curable media should be micromoldable and easily removed by burning, and include both thermoplastic and thermosetting materials.
Corning Incorporated
Fiorilla Christopher A.
Klee Maurice M.
LandOfFree
Method of manufacturing opaque rib structures for display panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing opaque rib structures for display panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing opaque rib structures for display panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2873067