Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-12-28
2001-11-13
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S190000
Reexamination Certificate
active
06317186
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a liquid crystal display device whereby sealing material is applied to peripheral portions of two substrates of the liquid crystal display device.
2. Related Art
The liquid crystal cell is used as a display panel of a wristwatch, a desk top calculator, etc. A recent field of a use of the liquid crystal cell has been broadened to a mobile apparatus (an information terminal device) or a large size display device.
FIGS.
1
(
a
)-(
c
) show a structure of a prior art liquid crystal cell formed by sealing the peripheral portions of two substrates face to each other by the sealing material, such as epoxy resin. FIG.
1
(
a
) shows a plan view of the structure of one substrate of the liquid crystal cell. FIG.
1
(
b
) shows a cross section along a cutting line A-A′. Particularly, in the FIG.
1
(
a
), a pixel region
13
, i.e. the display region, within the liquid crystal cell and the sealing scheme of the sealing material
30
are shown.
A first substrate
20
is made of a flat and hard glass plate. A major part of an upper surface of the first substrate
20
is the pixel region, i.e. the display region
13
on which colored layers forming R, G and B color filters (CF) are formed. The sealing material
30
is applied in a peripheral portion extending along the outer edge of the display region
13
of the first glass substrate
20
except a small portion which is later used as an entrance for the liquid crystal material. Small size spacers
40
are scattered on an entire area of the display region
13
to keep a thickness of a liquid crystal material to a constant value. A second substrate
10
is made of the flat and hard glass plate. A plurality of pixels, each of which includes a thin film transistor (TFT), are formed on the surface of the second substrate
10
to face each pixel on the first substrate
20
. The second substrate
10
and the first substrate
20
are faced to each other, and the applied sealing material
30
is deformed to bond the two substrates
10
and
20
. The sealing material
30
, such as the epoxy resin, is cured by heating the bonded substrates and the liquid crystal cell is sealed. The liquid crystal material is put into the liquid crystal cell through the entrance by a method well known in the art, and the final product of the liquid crystal cell is completed.
The FIG.
1
(
c
) schematically shows the deformed sealing material
30
on the corner region
42
during the sealing process in the prior art liquid crystal cell. Initially, the sealing material
30
on the corner region
42
is applied, as shown by hard lines
39
. In the process for positioning the second substrate
10
on the sealing material
30
, the sealing material on both the regions adjacent to the corner region
39
is moved and pressed toward the corner of the display region
13
resulting the pressed sealing material with an arc like edge
38
shown by a dash line.
The pixel region
13
in a side region
44
is generally formed to come near to an edge
36
of the sealing material
30
to insure the large display region
13
. If the arc like edge
38
of the sealing material
30
in the corner region, however, extends toward the inside of the substrate
20
, it covers the corner
15
of the pixel region
13
. If the corner
15
of the pixel region
13
is covered by the sealing material
30
, a defect of the displayed image is generated in the corner
15
. To keep a good display quality in a corner region
42
, it is necessary to keep away the corner
15
of the display region
13
from the inside edge
38
of the sealing material
30
. In this case, however, it is required to broaden the space between the horizontal edge of the pixel region
13
and the inside edge
36
of the sealing material
30
to realize the large pixel region
13
, resulting in that a use of a large substrate
20
is required.
Japanese Published Unexamined Patent Application 4-20929 discloses a liquid crystal cell in which an uneven portion is formed along peripheral portion of each of two substrates, a sealing material is applied on the uneven portion, and the two substrates are faced to each other and sealed. By providing the uneven portion on the portions on which the sealing material is applied, a strong adhesive strength is obtained, a penetration of water component into the liquid crystal cell is suppressed, and a reliability of a display panel is guaranteed.
Japanese Published Unexamined Patent Application 52-45947 discloses a technology for forming a groove along a peripheral edge of one of glass substrates of a liquid crystal cell. In a process for sealing the two glass substrates, an excess sealing material flows into the groove, so that a straight edge of the sealing material facing to a display area without an undesired wave like shape is realized. Since the edge of the sealing material facing to the display area is a straight line, a product value of the liquid crystal display panel is increased.
These prior art references, however, do not teach an improved method for applying the sealing material onto the corner regions of the substrate.
With the recent development of the mobile devices, such as a notebook computer, a personal data assistant (PDA), a handy phone, the requirement of the liquid crystal panel with the narrow frame region has been increased. To satisfy the technical requirement of the liquid crystal cell with the narrow frame region, it has been required to apply the sealing material used for sealing the two substrates onto the corner regions without partially overlapping with the corners
15
of the display region
13
.
These prior art references discussed above do not teach a technology of the fabrication of the liquid crystal cell for narrowing the frame region surrounding the corner region of the display region.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for applying the sealing material onto the corner regions of the substrate to realize the liquid crystal cell with the large display region.
According to the present invention, a liquid crystal cell is fabricated by sealing two substrates whereby a sealing material is placed on side regions and corner regions surrounding a display region. The sealing operation comprises the steps of: forming a difference of level at each boundary of the side region and the corner region on one surface of a first substrate for providing the corner region with a height which is lower than a height of the side region; applying the sealing material on the side regions and the corner regions on the one surface of the first substrate; and positioning a second substrate on the sealing material on the one surface of the first substrate, and decreasing a distance between the first substrate and the second substrate to collapse the sealing material applied on the side regions and the corner regions to thereby seal the first and second substrates.
In an alternate embodiment, the two substrates sealed by a sealing material placed on regions adjacent to edges of the substrates, and the sealing operation comprises the steps of: applying a sealing material on side regions and corner regions surrounding a display region on one surface of a first substrate; positioning a second substrate on the sealing material on the one surface of the first substrate, and decreasing a distance between the first substrate and the second substrate to collapse the sealing material applied on the side regions and the corner regions to seal the first and second substrates, wherein the step of applying the sealing material applies U shaped sealing material in the corner region, which extends toward a corner of the substrate, whereby an inside edge of the collapsed sealing material of one leg portion of the U shaped sealing material and an inside edge of the other leg portion of the U shaped sealing material form the substantially right angled corner during the step of collapsing the sealing material.
REFERENCES:
patent: 5742006 (1998-04
Lee Ho Chong
Miwa Koichi
Noquchi Michikazu
Seraphim Donald Philip
Skinner Dean William
International Business Machines - Corporation
Parker Kenneth
Qi Mike
Scully Scott Murphy & Presser
Underweiser, Esq. Marian
LandOfFree
Method for sealing corner regions of a liquid crystal display 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 for sealing corner regions of a liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for sealing corner regions of a liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2598301