Liquid crystal cells – elements and systems – Particular structure – Interconnection of plural cells in parallel
Reexamination Certificate
2000-08-28
2002-12-17
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Interconnection of plural cells in parallel
C349S042000, C349S074000
Reexamination Certificate
active
06496238
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to the design and manufacture of large, flat-panel electronic displays and, more particularly, to the manufacture of active matrix liquid crystal display (AMLCD) type, flat-panel displays assembled in a single monolithic or monolithic-like assembly, strengthened for structural integrity, corrected for brightness and hue variations due to optical or electro-optical aberrations and structural non-uniformities, equipped with lighting means and optical means that provide large view angles while improving visual acuity and contrast, and thin film wiring in the display that is uniquely designed to avoid or compensate for non-uniformities in pixel response, brightness, and chromaticity.
BACKGROUND OF THE INVENTION
Large displays can be constructed using several established display technologies, including cathode ray tubes (CRT) and projectors of the rear view type. However, as the diagonal size of these displays increases their volume and weight increase significantly. Further, manufacturing becomes more difficult while the manufacturing cost greatly increases.
An alternative approach to implementing large direct-view displays is provided by flat-panel displays, which offer a much reduced thickness and weight. The active-matrix liquid-crystal display (AMLCD) is the most mature of these technologies. The structure of an AMLCD consists of a liquid crystal (LC) layer sandwiched between two thin glass plates with a thickness typically of 0.5 mm, 0.7 mm, or 1.1 mm. As the diagonal size of the AMLCD increases above about 20 inches, the structural integrity of the sandwich becomes insufficient; hence the mechanical assembly should be strengthened for larger sizes. At the same time, non-uniformities arising from manufacturing and operation dramatically increase and the manufacturing yield decreases.
Today's AMLCD displays have several additional drawbacks in consumer applications. In particular, the view angles are limited to values much smaller than those of the CRT. In addition, the brightness-energy efficiency is reduced by polarizers, light collimator means, and any screens used to enhance the view angles. If such direct-view AMLCDs are to compete with CRTs in consumer applications, these deficiencies must be overcome.
Recent improvements in display technologies, as disclosed in the above related patents and patent applications, have been made to overcome these deficiencies or compensate for them in large tiled AMLCDs, in which the display is assembled from several smaller, independently fabricated pieces or tiles. Many of these improvements can also be applied to large monolithic displays. These improvements can help improve the characteristics of a monolithic or monolithic-like display or compensate for artifacts resulting from imperfect manufacturing of the components or their assembly. However the substantial structural differences between monolithic and tiled displays must be considered, when the new techniques are applied to monolithic ones.
Unlike tiled displays, monolithic displays have no structural discontinuities in the seams between adjacent tiles, a fact that substantially relaxes light collimation requirements, one of the key techniques used to hide the seams in tiled displays. As a consequence, the useable aperture ratio increases, screen specifications are altered, and the need for masks decreases. Therefore, the design of the optical stack and lighting in large monolithic or monolithic-like displays is significantly different compared to large, tiled AMLCD displays.
The present invention reflects unique designs and methods for fabricating or operating large monolithic or monolithic-like AMLCDs of both color and gray-scale types using many of the techniques developed for large, tiled, flat-panel displays (FPDs). Although this specification describes most of the techniques and methods in the context of AMLCDs, many of them can be applied to other transparent, light-valve type FPDs. Characteristic of such displays is that light from a uniform, back light source is transmitted through the display assembly towards the viewer located on the front side. The light valves control the amount of primary light rays transmitted through the apertures of sub-pixels. The transmitted light from the sub-pixels mixes to form all desired brightness and hue combinations (color space) before it reaches the viewer located at a predefined viewing distance from the display. The techniques and methods transferred from tiled to large-scale, monolithic, flat-panel displays, augmented with other methods described herein, significantly improve the performance of the latter, including viewing angle, image acuity, contrast, and color uniformity. At the same time, these unique design improvements can be used to increase the manufacturing yield, compensate for imperfections arising from the fabrication and assembly of the display, and transform the fragile, large, monolithic display into a robust laminate between glass cover plates and back plates.
Robust display glass laminates can be made using adhesive films with a preferred thickness in the range from 25 to 250 &mgr;m or thicker, and optimized in compliance. The monolithic display panel, for example, can be laminated between glass cover and back plates without stressing the birefringent AMLCD glass or deforming the LC cell gap. U.S. Pat. No. 5,867,236 “CONSTRUCTION AND SEALING OF TILED FLAT-PANEL DISPLAYS”, copending U.S. patent application Ser. No. 09/490,776 and U.S. patent application Ser. Nos. 09/368,921 and 09/369,465, show laminate structures that accomplish the desired result. Laminate structures for a prototype 800×600 SVGA 38.6″ diagonal tiled display are also shown in copending patent application Ser. No. 09/268,921. A method for processing large display laminates is discussed in copending patent application Ser. No. 09/322,047 and U.S. Pat. No.
The laminate is designed with a symmetry about the image creation plane in the AMLCD glass sandwich (LC layer), which contains the weakest link to shear or bending. This link is formed by a narrow adhesive seal, typically about 5 &mgr;m thick, that joins the thin-film-transistor (TFT) substrate to the color-filter (CF) substrate around the perimeter of the display. The width of this seal may be as narrow as 1 mm or less, and it may be the only mechanical link, other than surface tension of the LC liquid layer, that holds the substrates together during handling, assembly, and field use induced stresses.
An external full face seal material, in dry film form, or a layered combination with dry film, or liquid film alone, of a preferred thickness range and preferred elastic compliance, is used to bond the robust glass cover and back plates on both sides of the AMLCD sandwich to increase the bending strength. This preferred design provides a substantially increased resistance to bending, thereby decreasing the effect of any unintentional stresses exerted on the narrow seal. The preferred thickness of the adhesive films between cover and back plates and the AMLCD sandwich are dependent on whether a mask is used on the back plate to set the light collimation angles. The relationships of these angles are shown in detail in the aforementioned patent applications.
Since such aperture masks are not needed on the back plate to direct light rays away from the seams in monolithic displays, as in tiled ones, the thickness requirement for the adhesive may be relaxed for the monolithic display laminates. Aperture masks on the cover and back plates may still be desirable in monolithic displays to optimize the visual acuity and contrast of displayed images. Alternatively, they may be removed from the display stack, if other light collimation means are preferred.
The air is controllably purged at the meniscus of the full face adhesive interface between cover and back plates and the AMLCD sandwich so that no bubble-type defects are introduced in these laminate structures during assembly. Techniques for achieving bubble free laminate assemblies for attaching
Greene Raymond G.
Krusius J. Peter
Seraphim Donald P.
Skinner Dean W.
Yost Boris
Qi Mike
Rainbow Displays Inc.
Salzman & Levy
Ton Toan
LandOfFree
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