Seal for LCD devices and methods for making same

Details Seal for LCD devices and methods for making same Seal for LCD devices and methods for making same

1998-11-04

2002-03-19

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between fixed parts or static contact against...

Contact seal for other than internal combustion engine, or...

C349S155000, C349S190000, C277S377000

Reexamination Certificate

active

06357763

ABSTRACT:

BACKGROUND OF THE INVENTION
The present inventions relate generally to liquid crystal displays (LCDs). More specifically to methods and apparatuses for sealing LCD devices.
Today, small scale LCD devices, such as light valves are becoming more prominent. Small scale LCD devices, and light valves are typically manufactured according to certain specifications to ensure that they function properly. One criteria is that the pixel array is appropriately sealed to prevent contamination and ensure proper operation.
Referring to
FIG. 1
, a typical small scale LCD device
10
includes a die
20
containing a pixel array
22
. Pixel array
22
is typically composed of rows and columns of electrically conductive pathways. At the intersection of a row and a column of the electrically conductive pathways is a pixel. Each pixel can be turned on individually by selecting the appropriate row and column of pixel array
22
. Selection of a pixel is controlled by control circuitry, either included within the die
20
or external to the die
20
. In both cases, external control signals may be used to control the functions of the die
20
. Bond pads
25
, are usually placed around pixel array
22
, and typically connected to the pixel array
22
to allow control of the operation of the pixel array
22
.
Bond pads
25
are electrically coupled to pixel array
22
by circuitry that is normally internal to the die
20
. A glass plate
30
is typically placed over die
20
and pixel array
22
, such that the glass plate
30
overhangs the die
20
, and may cover an area of die
20
that could have contained bond pads
25
. The placement of bond pads
25
are often concentrated to one or two sides of die
20
, such that the glass plate
30
does not cover the bond pads
25
.
Die
20
is typically mounted to a substrate
80
. Substrate
80
includes a plurality of substrate pads
85
. Bond pads
25
typically are wire bonded to the substrate pads
85
by bonding wires
90
.
Typically, an adhesive seal
50
is formed between glass plate
30
and die
20
and surrounding pixel array
22
. The sealed area between glass plate
30
and pixel array
22
is commonly filled with a solution of liquid crystal materials
60
. After die
20
is properly affixed with glass plate
30
, die
20
is attached and coupled to substrate
80
, and sealed. Seal
50
contains the liquid crystal material
60
from leaking.
In typical LCD devices seal
50
often times does not maintain its integrity, which causes deformation and irregularities in the LCD devices. The failure of seal
50
to adequately adhere glass plate
30
to die
20
may cause artifacts
70
. The artifacts may extend into the active area of the pixel array, causing visual aberrations in the final LCD device. Such artifacts render the LCD device defective.
FIGS. 2
,
3
and
4
illustrate cross-sectional views of an LCD device
12
. The cross-sections depict a glass plate
30
bonded to a die
20
by a seal
50
. The interior is filled with liquid crystal material
60
.
FIG. 2
illustrates the initial shape of seal
50
immediately after glass plate
30
is attached to die
20
. Seal
50
sufficiently contains liquid crystal material
60
. During the process of handling LCD device
12
many factors contribute to the deformation of seal
50
, and LCD device
12
itself.
After glass plate
30
is attached to die
20
and LCD device
12
is filled with liquid crystal material
60
further processing steps require handling the LCD device
12
. For example, the LCD device
12
is placed on a substrate (such as substrate
80
of FIG.
1
). Also, LCD device
12
is subjected to functional testing. During these processing steps, LCD device
12
may undergo temperatures and stresses that may cause seal
50
to deform.
Referring to
FIG. 3
, many seals do not maintain their integrity during handling and/or testing of the LCD device. In typical LCD devices seal
50
is tensile. That is, seal
50
has a tendency to expand. The tensile nature of
50
becomes more troublesome during the heating and handling of the LCD device.
As illustrated, a common problem of the tensile nature of seal
50
is the delamination of liquid crystal material
60
from glass plate
30
. Heating and/or handling of the LCD device may cause thermal excursion of the liquid crystal material. The liquid crystal material will typically tend to expand. Due to the tensile nature of seal
50
, seal
50
may not contain the expanding liquid crystal material and expand outward, as illustrated. The liquid crystal material delaminates from the glass plate because the seal does not prevent the thermal excursion of the liquid crystal material.
A similar problem that causes artifacts in the LCD device is the deformation of the glass plate and/or the die.
FIG. 4
illustrates a LCD device
12
with a deformed glass plate
30
. Glass plate
30
(or die
20
) may deform or bow during heating and/or handling of the LCD device. The deformation often times causes the glass plate to separate from the liquid crystal material
60
. Again, seal
50
may not prevent the problem due to its tensile nature. The delamination of the glass plate from the liquid crystal material similarly causes artifacts in the LCD device that may render the device defective.
Therefore, current methods of sealing a LCD device may not sufficiently prevent delamination of the glass plate from the liquid crystal material. A seal that is capable of preventing the delamination of liquid crystal material from the glass plate is desired.
SUMMARY OF THE INVENTION
The present invention provides an improved seal for sealing a liquid crystal display (LCD) device. An improved seal is formed between a transparent plate and a die having a pixel array. The improved seal is configured to encircle the pixel array of the die when the die and the transparent plate are joined. The die and the transparent plate are joined together such that the improved seal is disposed between the transparent plate and the die.
In one embodiment, the improved seal is a hybrid seal. The hybrid seal includes a first seal encircling the pixel array of the die and adhesively coupling the transparent plate and the die. The hybrid seal further includes a second seal encircling the second seal.
In another embodiment, the first seal lacks a characteristic necessary for an effective seal. The second seal possesses the characteristic, such that the hybrid seal possesses the necessary characteristic.
These and other advantages of the present inventions will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawing.


REFERENCES:
patent: 3939556 (1976-02-01), Borel et al.
patent: 4023259 (1977-05-01), Kubota et al.
patent: 4037930 (1977-07-01), Matsuyama
patent: 4050786 (1977-09-01), Feldmen
patent: 4165157 (1979-08-01), Kobale et al.
patent: 4308442 (1981-12-01), Sallin et al.
patent: 4470668 (1984-09-01), Inoue et al.

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