Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-09-04
2001-10-16
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S155000
Reexamination Certificate
active
06304307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a configuration of an active matrix liquid crystal display having thin film transistors for pixels and thin film transistors for peripheral driving circuits on the same substrate.
2. Description of the Related Art
FIG. 4
shows a configuration of a panel forming a part of a conventional active matrix liquid crystal display. As apparent from
FIG. 4
, a pixel region
404
has been enclosed by an opposite substrate
405
and a sealant
402
(also referred to as “seal material”) while thin film transistors (hereinafter referred to as “TFT”) in peripheral driving circuit regions
403
have been exposed to the atmosphere.
Therefore, it has been necessary to be very careful in handling, the substrate of an active matrix liquid crystal display at a panel assembly process. Under such circumstances, there has been a need for a configuration of an active matrix liquid crystal display which makes handling in manufacturing processes easier.
Further, the presence of the opposite substrate
405
above the pixel region protects the pixel region
404
as a consequence. However, the peripheral driving circuits
403
are merely covered by a thin oxide film and actually show weakness in anti-humidity characteristics and against contamination. Problems have arisen also in the aspect of reliability.
SUMMARY OF THE INVENTION
Methods were conceived to address such problems in which peripheral driving circuits
403
of an active matrix liquid crystal display are configured to inhibit direct access thereto and, in which the region where the opposite substrate resides is extended to the areas where the peripheral driving circuits are formed to include the peripheral driving circuits in a region where a liquid crystal material is present. Such methods are disclosed in Japanese patent application No. H7-50527 (Japanese Laid-Open Aplication: H8-220560, Date of Laid-Open: Aug. 30, 1996).
However, the following problems have arisen in such a configuration.
Among steps for assembling a liquid crystal display, a step of bonding two opposite substrates generally employs a process of hardening the sealant while applying a pressure vertically to the surfaces of the substrates. For a normal liquid crystal display, spacers are interposed between the two substrates to maintain a predetermined interval between the two substrates. Therefore, a pressure is applied through the spacers to devices and the like formed on the substrates at this step.
Especially, in the case of a liquid crystal display having the configuration described above, the opposite substrate extending to the peripheral driving circuits has extended the pressure also to the peripheral driving circuits through the spacers.
In the peripheral driving circuit regions, TFTs are provided in a density higher than that in the pixel region. Therefore, when the spacers are dispersed in a uniform density throughout the substrate as in conventional liquid crystal displays, the spacers cause more damage in the peripheral driving circuits than in the pixel region. This reduces reliability and yield.
In order to solve the above-described problems, according to the present invention, an active matrix liquid crystal display is configured as follows.
Specifically, there is provided an active matrix liquid crystal display wherein thin film transistors provided in a pixel region and thin film transistors provided in peripheral driving circuit regions reside on the same substrate, characterized in that there is a difference in the dispersion density of spacers between the pixel region and the peripheral driving circuit regions.
As another configuration, there is provided an active matrix liquid crystal display wherein thin film transistors provided in a pixel region and thin film transistors provided in peripheral driving, circuit regions reside on the same substrate, characterized in that spacers are present in the pixel region and are not present in the peripheral driving circuit regions.
When an active matrix liquid crystal display is configured such that thin film transistors disposed in a pixel region and thin film transistors forming peripheral driving circuit regions of an active matrix liquid crystal display are integrated on the same substrate, in the above-described configuration, a mask is provided in the regions wherein the TFTs for the peripheral driving circuit regions reside when the spacers are dispersed to inhibit the spacers from being dispersed therein to improve the reliability of the peripheral driving circuits, thereby improving the yield of the peripheral driving circuits.
In a case that a means utilizing static electricity is used as a method of dispersing spacers, better methods for applying a voltage for generating static electricity are pursued. For example, when spacers are dispersed to improve the reliability of peripheral driving circuits, the spacers are dispersed in a lower density in the regions where the TFTs for the peripheral driving circuits reside by applying a voltage at a value different from that applied to the region where pixel TFTs reside to improve the yield of the peripheral driving circuits.
Further, when the spacers are dispersed, the dispersion density of the spacers is made lower in the regions on the stage carrying the substrates of an active matrix liquid crystal display where the TFTs for the peripheral driving circuits reside by applying a voltage thereto at a value different from that applied to the region where the pixel TFTs reside, thereby improving the yield of the peripheral driving circuits. Alternatively, when the spacers are dispersed, the voltage for generating static electricity is not applied to the regions where the TFTs for the peripheral driving circuits reside and the potential for generating static electricity is applied only to the region where the pixel TFTs reside. This allows the spacers to be selectively dispersed only in the pixel region. Further, the density of the spacers dispersed in the peripheral driving circuit regions may be reduced.
When peripheral driving circuit regions are included in a region wherein liquid crystals are present, damage to the TFTs forming the peripheral driving circuits caused by the presence of spacers is reduced by lowering the density of the spacers dispersed in the peripheral driving circuit regions or by inhibiting the spacers from being dispersed in the peripheral driving circuit regions. Thus, it is possible to improve the reliability of a liquid crystal display having a configuration wherein a pixel region and peripheral driving circuits are formed on the same substrate.
REFERENCES:
patent: 5076667 (1991-12-01), Stewart et al.
patent: 5148301 (1992-09-01), Sawatsubashi et al.
patent: 5247375 (1993-09-01), Mochizuki et al.
patent: 5250931 (1993-10-01), Misawa et al.
patent: 5278685 (1994-01-01), Iwamoto et al.
patent: 5410423 (1995-04-01), Furushima et al.
patent: 5677749 (1997-10-01), Tsubota et al.
patent: 5712495 (1998-01-01), Suzawa
patent: 5724110 (1998-03-01), Majima
patent: 5815231 (1998-09-01), Nishi et al.
patent: 62-166317 (1987-07-01), None
patent: 63-246722 (1988-10-01), None
patent: 4-163422 (1992-06-01), None
patent: 5-066413 (1993-03-01), None
Adachi Masahiro
Konuma Toshimitsu
Nishi Takeshi
Ogishima Kiyoshi
Tsuji Takahiro
Fish & Richardson PC
Nguyen Dung
Semiconductor Energy Laboratory Co,. Ltd.
Sikes William L.
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