U.S. patent application number 09/855695 was filed with the patent office on 2001-09-13 for position sensing liquid crystal display and method for fabricating the same.
Invention is credited to Ahn, Young Soo, Bae, Sung Joon.
Application Number | 20010020987 09/855695 |
Document ID | / |
Family ID | 19523967 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010020987 |
Kind Code |
A1 |
Ahn, Young Soo ; et
al. |
September 13, 2001 |
Position sensing liquid crystal display and method for fabricating
the same
Abstract
A position sensing liquid crystal display includes a liquid
crystal display panel having a first substrate and a second
substrate bonded together, and a position sensing digitizer formed
as an integral unit on a first or rear surface of at least one of
the substrates, whereby minimizing a display panel thickness and
allowing an accurate position sensing.
Inventors: |
Ahn, Young Soo; (Anyang-si,
KR) ; Bae, Sung Joon; (Sungnam-si, KR) |
Correspondence
Address: |
SONG K. JUNG
LONG ALDRIDGE & NORMAN, LLP
SIXTH FLOOR
701 PENNSYLVANIA AVENUE, N.W.
Washington
DC
20004
US
|
Family ID: |
19523967 |
Appl. No.: |
09/855695 |
Filed: |
May 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09855695 |
May 16, 2001 |
|
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|
09183638 |
Oct 30, 1998 |
|
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Current U.S.
Class: |
349/12 |
Current CPC
Class: |
G06F 3/0412 20130101;
G02F 1/13338 20130101; G06F 3/0444 20190501; G02F 1/1339 20130101;
G02F 1/133512 20130101 |
Class at
Publication: |
349/12 |
International
Class: |
G02F 001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 1997 |
KR |
57476 |
Claims
What is claimed is:
1. A liquid crystal display panel, comprising: a first substrate
having front and rear surfaces; a second substrate having front and
rear surfaces, the front surface of the second substrate including
a plurality of pixel electrodes and abutting against the rear
surface of the first substrate; and a digitizer having intersecting
grids fabricated on at least one of the front and rear surfaces of
the first and second substrates.
2. A liquid crystal display panel of claim 1, wherein the rear
surface of the first substrate includes a black matrix layer having
intersecting grids at a predetermined interval.
3. A liquid crystal display panel of claim 2, wherein the digitizer
is fabricated on the front surface of the first substrate, the
intersecting grids of the digitizer being substantially aligned
with the intersecting grids of the black matrix layer.
4. A liquid crystal display panel of claim 3, wherein the
intersecting grids of the digitizer are made of a conductive
material.
5. A liquid crystal display panel of claim 4, wherein the
conductive material is one of metal and Indium Tin Oxide.
6. A liquid crystal display panel of claim 2, wherein the
intersecting grids of the black matrix layer are the intersecting
grids of the digitizer, wherein the intersecting grids of the black
matrix layer are fabricated with a conductive material.
7. A liquid crystal display panel of claim 2, wherein the digitizer
is fabricated on the rear surface of the second substrate, the
intersecting grids of the digitizer being substantially aligned
with the intersecting grids of the black matrix layer.
8. A liquid crystal display panel of claim 1, further including
input signal portions fabricated in the vicinity of four corners of
the digitizer, the input signal portions providing a position
signal to the intersecting grids of the digitizer for detecting a
stylus position.
9. A liquid crystal display panel of claim 1, further including
input signal portions fabricated substantially in the middle of
each side of the digitizer, the input signal portions providing a
position signal to the intersecting grids of the digitizer for
detecting a stylus position.
10. A liquid crystal display panel of claim 8, further including
compensating resistors connected between the input signal portions
and the intersecting grids of the digitizer, wherein the
compensating resistors formed near the input signal portions have a
higher resistivity than the compensating resistors formed farther
away from the input signal portions to provide substantially equal
potential to the intersecting grids of the digitizer.
11. A liquid crystal display panel of claim 9, further including
compensating resistors connected between the input signal portions
and the intersecting grids of the digitizer, wherein the
compensating resistors formed near the input signal portions have a
higher resistivity than the compensating resistors formed farther
away from the input signal portions to provide substantially equal
potential to the intersecting grids of the digitizer.
12. A liquid crystal display panel of claim 10, further including
at least one equipotential line connected between the input signal
portions and the compensating resistors, wherein the equipotential
line has a lower resistivity than the compensating resistors.
13. A liquid crystal display panel of claim 11, further including
at least one equipotential line connected between the input signal
portions and the compensating resistors, wherein the equipotential
line has a lower resistivity than the compensating resistors.
14. A liquid crystal display panel of claim 9, wherein the
compensating resistors include a tree shape of repetitive sequence
of layers of: primary interconnections between adjacent grids,
secondary interconnections between adjacent primary
interconnections, and tertiary interconnections between adjacent
secondary interconnections.
15. A display device using a liquid crystal display panel,
comprising: a controller that controls displayed images of the
liquid crystal display panel; a first substrate having front and
rear surfaces; a second substrate having front and rear surfaces,
the front surface of the second substrate including a plurality of
pixel electrodes and abutting against the rear surface of the first
substrate; and a digitizer having intersecting grids fabricated on
at least one of the front and rear surfaces of the first and second
substrates.
16. A display device of claim 15, wherein the rear surface of the
first substrate includes a black matrix layer having intersecting
grids at a predetermined interval.
17. A display device of claim 16, wherein the digitizer is
fabricated on the front surface of the first substrate, the
intersecting grids of the digitizer being substantially aligned
with the intersecting grids of the black matrix layer.
18. A liquid crystal display panel of claim 17, wherein the
intersecting grids of the digitizer are made of a conductive
material.
19. A liquid crystal display panel of claim 18, wherein the
conductive material is one of metal and Indium Tin Oxide.
20. A liquid crystal display panel of claim 16, wherein the
intersecting grids of the black matrix layer are the intersecting
grids of the digitizer, wherein the intersecting grids of the black
matrix layer are fabricated with a conductive material.
21. A liquid crystal display panel of claim 16, wherein the
digitizer is fabricated on the rear surface of the second
substrate, the intersecting grids of the digitizer being
substantially aligned with the intersecting grids of the black
matrix layer.
22. A liquid crystal display panel of claim 15, further including
input signal portions fabricated in the vicinity of four corners of
the digitizer, the input signal portions providing a position
signal to the intersecting grids of the digitizer for detecting a
stylus position.
23. A liquid crystal display panel of claim 15, further including
input signal portions fabricated substantially in the middle of
each side of the digitizer, the input signal portions providing a
position signal to the intersecting grids of the digitizer for
detecting a stylus position.
24. A liquid crystal display panel of claim 22, further including
compensating resistors connected between the input signal portions
and the intersecting grids of the digitizer, wherein the
compensating resistors formed near the input signal portions have
higher resistivity and the compensating resistors formed farther
away from the input signal portions to provide substantially equal
potential to the intersecting grids of the digitizer.
25. A liquid crystal display panel of claim 23, further including
compensating resistors connected between the input signal portions
and the intersecting grids of the digitizer, wherein the
compensating resistors formed near the input signal portions have
higher resistivity and the compensating resistors formed farther
away from the input signal portions to provide substantially equal
potential to the intersecting grids of the digitizer.
26. A liquid crystal display panel of claim 24, further including
at least one equipotential line connected between the input signal
portions and the compensating resistors, wherein the equipotential
line has lower resistivity than the compensating resistors.
27. A liquid crystal display panel of claim 25, further including
at least one equipotential line connected between the input signal
portions and the compensating resistors, wherein the equipotential
line has lower resistivity than the compensating resistors.
28. A method for fabricating a liquid crystal display panel having
a digitizer, comprising the steps of: providing a first substrate
having front and rear surfaces; providing a second substrate having
front and rear surfaces, wherein the second substrate has a first
display region in the front surface; forming a plurality of pixel
electrodes in the first display region of the front surface of the
second substrate; securing the front surface of the second
substrate to the rear surface of the first substrate; and
fabricating intersecting grids of the digitizer on at least one of
the front and rear surfaces of the first and second substrates.
29. A method of claim 28, wherein before securing the front surface
of the second substrate to the rear surface of the first substrate,
surrounding the first display region with a sealing material to
define a first surrounded region; and surrounding the first
surrounded region with the sealing material, wherein when the first
and second substrates are secured together, the sealing material
surrounding the first surrounded region substantially prohibits the
intrusion of a foreign substance.
30. A method of claim 28, wherein before securing the front surface
of the second substrate to the rear surface of the first substrate,
providing the second substrate to define a second display region;
forming pixel electrodes in the second display region of the second
substrate; surrounding the first display region with a sealing
material to define a first surrounded region; surrounding the
second display region with the sealing material to define the first
surrounded region; surrounding the first and second surrounded
regions with the sealing material, wherein when the first and
second substrates are secured together, the sealing material
surrounding the first and second surrounded regions substantially
prohibits the intrusion of a foreign substance.
31. A method of claim 29, wherein the intersecting grids of the
digitizer are fabricated on at least one of the front and rear
surfaces of the first and second substrates and in the first
display region.
32. A method of claim 30, wherein the intersecting grids of the
digitizer are fabricated on at least one of the front and rear
surfaces of the first and second substrates and in the first
display region and the intersecting grids of a second digitizer is
fabricated in the second display region.
33. A method of claim 32, wherein the first and second substrates
are scribed to separate the first display region from the second
display region, each one of the first and second display regions
having the digitizer.
34. A method of claim 28, wherein the digitizer is formed of a
conductive material.
35. A method of claim 34, wherein the digitizer is formed one of
Indium Tin Oxide and metal.
36. A liquid crystal display panel formed by the method of claim
28.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a position sensing liquid
crystal display (PSLCD), and more particularly to a position
sensing liquid crystal display and a method for fabricating the
same, in which position sensors, such as digitizers, are formed
after bonding of upper and lower plates of the liquid crystal
display.
[0003] 2. Discussion of the Related Art
[0004] In general, the liquid crystal display at large is provided
with an upper plate, a lower plate, and a liquid crystal sealed
between the upper plate and the lower plate. The upper plate has a
black matrix layer, a common electrode, and color filter layers of
R (red), G (green), and B (blue) for displaying colors disposed
thereon. The lower plate has data lines and gate lines crossing the
other to form a matrix of pixel regions, each having a thin film
transistor and a pixel electrode. That is, as shown in FIG. 1, the
lower plate 1 is provided with a matrix of thin film transistors,
each having a gate electrode gate extended from a scan line, a
source electrode S and a drain electrode extended from a data line
disposed at fixed intervals. Each of the pixel regions is provided
with a pixel electrode 2a having the drain electrode D of the thin
film transistor 2 connected thereto. The upper plate 3 is provided
with a matrix form of the black matrix layer 4 for blocking
transmission of light for parts excluding the pixel electrodes 2a
on the lower plate 1. There are R, G, and B color filter layers 5
between the black matrix layer 4, each for displaying a color. A
common electrode 6 is formed extended to the color filter layer 5
and the black matrix layer 4. Upon selective application of driving
signals to the scanning lines and the data lines from external
driving circuits, the liquid crystal display displays an image.
Though the aforementioned liquid crystal display has been designed
only to display images according to the external driving signals,
recently researches are underway in which the liquid crystal
display is provided with additional position sensors for efficient
use of the display in a notebook computer. That is, if a character
or graphic is drawn with a stylus (an electronic pen) on the liquid
crystal display equipped with the position sensors, the character
or graphic is displayed as drawn.
[0005] A related art position sensing liquid crystal display will
be explained with reference to the attached drawings. FIG. 2
illustrates a first example of the related art position sensing
liquid crystal display.
[0006] Referring to FIG. 2, the first example of the related art
position sensing liquid crystal display has a digitizer for sensing
a position additionally provided outside of a general liquid
crystal display independently, i.e., provided with a liquid crystal
display 21 and a digitizer panel 23. There is a position sensing
layer 23a (hereafter called, "digitizer"), a compensating resistor
region 25 around the digitizer 23a for compensating a voltage
difference, and signal applying parts 27a, 27b, 27c, and 27d at
four corners of the compensating resistor region 25 for applying a
position sensing signal. In the aforementioned position sensing
liquid crystal display, when the signal applying parts 27a and 27b
are applied at a position signal and the signal applying parts 27c
and 27d are grounded, the digitizer 23a has a potential
distribution from upper side to lower side thereof. When the signal
applying parts 27a and 27c are applied at a position signal and the
signal applying parts 27b and 27d are grounded, the digitizer 23a
has a potential distribution from right side to left side thereof.
Thus, when a stylus 29 is brought into contact with a point on the
digitizer 23a after selective application of a position sensing
signal to the signal applying parts 27a, 27b, 27c, and 27d, a
present position of the stylus 29 can be sensed and determined. In
the sensing of the position, a voltage of the position of the
digitizer 24a at which the stylus 29 is brought into contact is
used. The position sensing of even a finger tip touch can be made,
which is displayed in turn on a liquid crystal display.
[0007] FIG. 3 illustrates a second example of the related art
position sensing liquid crystal display. The second PSLCD has a
position sensing digitizer provided inside a liquid crystal display
panel. As explained in connection with FIG. 1, the second PSLCD is
provided with metal, an insulating film, and a semiconductor layer
on a glass for displaying an image, wherein a position sensing
layer is embodied using the glass of an image data input electrical
device. That is, the second PSLCD is provided with an upper plate
21a, a lower plate 21b, and a digitizer 23a between the upper plate
21a and the lower plate 21b. As explained, the upper plate 21a has
the black matrix layer (not shown), a color filter layer, and an
ITO layer of a common electrode formed thereon. The lower plate 21b
has data lines 31, gate lines 33, and pixel electrodes (not shown),
and the digitizer 23a has a compensating resistor region 25 around
the digitizer and signal applying parts 27b and 27d at four corners
of the compensating resistor region 25 (signal applying parts 27a
and 27c are not shown).
[0008] In the second PSLCD, when the signal applying parts 27a,
27b, 27c, and 27d are applied of a position signal, the digitizer
23a exhibits a potential distribution. Accordingly, when stylus 29
is brought into contact with the display, a voltage at the contact
point is sensed, thereby allowing to sense the present position. A
finger tip touch on the display can be also sensed. Thus, upon a
stylus 29 is brought into contact with a position sensing digitizer
23a after selective application of position signal through signal
applying parts 27a, 27b, 27c, and 27d, the PSLCD can sense the
present position of the stylus 29 by using a capacitive coupling
between the digitizer 23a and the stylus 29.
[0009] However, the aforementioned related art PSLCD has the
following problems. First, the first PSLCD is cumbersome to carry
because of the digitizer provided additionally on the outside of
the LCD, which makes the LCD thicker and bulkier.
[0010] Second, in the case of the second PSLCD, the severe signal
interference and the non-uniform potential distribution of a
position sensing layer caused by capacitive coupling between the
position sensing layer in the digitizer and the common electrode
disposed on opposite sides of an insulating film impedes accurate
position sensing and degrades the picture quality.
[0011] Third, in a case of the first conventional PSLCD, the
inaccurate voltage compensation caused by the misaligned digitizer
with respect to the panel causes an inaccurate position
sensing.
SUMMARY OF THE INVENTION
[0012] Accordingly, the present invention is directed to a position
sensing liquid crystal display and a method for fabricating the
same that substantially obviates one or more of the problems due to
limitations and disadvantages of the related art.
[0013] An object of the present invention is to provide a position
sensing liquid crystal display and a method for fabricating the
same which can sense an accurate position of the stylus.
[0014] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0015] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, a liquid crystal display panel has a first substrate
having front and rear surfaces, a second substrate having front and
rear surfaces, the front surface of the second substrate including
a plurality of pixel electrodes and abutting against the rear
surface of the first substrate, and a digitizer having intersecting
grids fabricated on at least one of the front and rear surfaces of
the first and second substrates.
[0016] According to one aspect of the present invention, the rear
surface of the first substrate includes a black matrix layer having
intersecting grids at a predetermined interval. Preferably, the
digitizer is fabricated on the front surface of the first
substrate, the intersecting grids of the digitizer being
substantially aligned with the intersecting grids of the black
matrix layer. The intersecting grids of the digitizer may be made
of a conductive material, such as metal or Indium Tin Oxide.
Instead of providing a digitizer separate from the black matrix,
the intersecting grids of the black matrix layer may be used as the
intersecting grids of the digitizer, in which the intersecting
grids of the black matrix layer are fabricated with a conductive
material.
[0017] In another aspect of the present invention, the digitizer
may be fabricated on the rear surface of the second substrate, the
intersecting grids of the digitizer being substantially aligned
with the intersecting grids of the black matrix layer.
[0018] In another aspect of the present invention, input signal
portions may be fabricated in the vicinity of four corners of the
digitizer. The input signal portions provide a position signal,
such as an input voltage, to the intersecting grids of the
digitizer for detecting a stylus position. Alternatively, the input
signal portions may be fabricated substantially in the middle of
each side of the digitizer.
[0019] In the liquid crystal display panel with the digitizer
according to the present invention, there are compensating
resistors connected between the input signal portions and the
intersecting grids of the digitizer. The compensating resistors
formed near the input signal portions preferably have a higher
resistivity than the compensating resistors formed farther away
from the input signal portions to provide substantially equal
potential to the intersecting grids of the digitizer. The
compensating resistors include a tree shape of repetitive sequence
of layers of primary interconnections between adjacent grids,
secondary interconnections between adjacent primary
interconnections, and tertiary interconnections between adjacent
secondary interconnections.
[0020] In addition, there is at least one equipotential line
connected between the input signal portions and the compensating
resistors. Preferably, the equipotential line has a lower
resistivity than the compensating resistors.
[0021] The PSLCD having a digitizer may be used with a controller
that controls displayed images of the liquid crystal display panel.
Such controller is necessary for using the PSLCD in computing
devices and display devices.
[0022] The PSLCD having a digitizer may be fabricated by providing
a first substrate having front and rear surfaces; providing a
second substrate having front and rear surfaces, wherein the second
substrate has a first display region in the front surface; forming
a plurality of pixel electrodes in the first display region of the
front surface of the second substrate; securing the front surface
of the second substrate to the rear surface of the first substrate;
and fabricating intersecting grids of the digitizer on at least one
of the front and rear surfaces of the first and second
substrates.
[0023] Before securing the front surface of the second substrate to
the rear surface of the first substrate, it is preferable to
surround the first display region with a sealing material to define
a first surrounded region, and surround the first surrounded region
with the sealing material. Therefore, when the first and second
substrates are secured together, the sealing material surrounding
the first surrounded region substantially prohibits the intrusion
of any foreign substance.
[0024] In an alternative method, it is preferable to fabricate
multiple display regions on one substrate. To accomplish this task,
before securing the front surface of the second substrate to the
rear surface of the first substrate, provide the second substrate
to define a second display region having a second set of pixel
electrodes; form pixel electrodes in the second display region of
the second substrate; surround the first display region with a
sealing material to define a first surrounded region; surround the
second display region with the sealing material to define the first
surrounded region; surround the first and second surrounded regions
with the sealing material. When the first and second substrates are
secured together, the sealing material surrounding the first and
second surrounded regions substantially prohibits the intrusion of
a foreign substance.
[0025] In the above processes, the intersecting grids of the
digitizer are fabricated on at least one of the front and rear
surfaces of the first and second substrates and in the first
display region. Thereafter, the first and second substrates are
scribed to separate the first display region from the second
display region, each one of the first and second display regions
having the digitizer.
[0026] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0028] FIG. 1 illustrates a section of a liquid crystal
display;
[0029] FIG. 2 illustrates a first related art position sensing
liquid crystal display;
[0030] FIG. 3 illustrates a second related art position sensing
liquid crystal display;
[0031] FIG. 4 illustrates a position sensing liquid crystal display
in accordance with a preferred embodiment of the present
invention;
[0032] FIG. 5 illustrates a plan view of a liquid crystal
display;
[0033] FIG. 6 illustrates a partial cut away view of glass
substrates having a sealing material bonded thereto;
[0034] FIG. 7 illustrates a partial cut away view of another glass
substrate having a sealing material bonded thereto;
[0035] FIG. 8 illustrates a perspective view of a position sensing
liquid crystal display in accordance with a first embodiment of the
present invention;
[0036] FIG. 9 illustrates a perspective view of a position sensing
liquid crystal display in accordance with a second embodiment of
the present invention;
[0037] FIG. 10 illustrates a compensating resistor region used in
the present invention;
[0038] FIG. 11 illustrates a perspective view of a position sensing
liquid crystal display in accordance with a third embodiment of the
present invention;
[0039] FIG. 12 illustrates a plan view of a position sensing liquid
crystal display in accordance with a fourth embodiment of the
present invention;
[0040] FIG. 13 illustrates another embodiment of the compensating
resistor region used in the present invention; and
[0041] FIG. 14 illustrates a flow chart showing the steps of a
method for fabricating a PSLCD according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. In the present invention,
a unitary digitizer is provided at a back side of a liquid crystal
display panel. FIG. 4 illustrates a system of a position sensing
liquid crystal display in accordance with a preferred embodiment of
the present invention.
[0043] Referring to FIG. 4, the position sensing liquid crystal
display in accordance with a preferred embodiment of the present
invention includes a liquid crystal display panel 21 having a first
substrate 21a (hereinafter called, "an upper plate") and a second
substrate 21b (hereinafter called, "a lower plate") bonded
together, and a digitizer 23a formed on a back surface of either
the first substrate 21a or the-second substrate 21b.
[0044] Referring to FIG. 5, in the position sensing liquid crystal
display in accordance with a preferred embodiment of the present
invention, a plurality of black matrix patterns 71 is preferably
formed on the first substrate 21a, and color filter layers 73
(shaded portion) are formed between the black matrix layer patterns
71 for displaying colors. Then an overcoat layer (not shown) is
formed on an entire surface inclusive of the color filter layer 73.
An ITO layer (not shown) for use as a common electrode is formed on
the overcoat layer.
[0045] A matrix of data lines 75 and gate lines 77 are formed on
the second substrate 21b. A thin film transistor (TFT) is formed at
every crossing of the data lines 75 and the gate lines 77. After
formation of required patterns on the first substrate 21a and the
second substrate 21b, respectively, the first substrate 21a and the
second substrate 21b are bonded with a sealing material. That is,
for a simplification of a fabrication process, patterns for a
plurality of displays are concurrently formed on a sheet of glass
substrate, and the completed glass substrate is cut into display
regions, which are bonded with the sealing material according to
the following process.
[0046] FIG. 6 illustrates a partial cut away view of the first
glass substrate and the second glass substrate bonded with a
sealing material. In FIG. 6, there are multiple LCD panels formed
on the substrate, each panel individually surrounded by a sealing
material. Referring to FIG. 6, the sealing material 45 is applied
around each liquid crystal sealing region of a display region in
one pair of glass substrates 41, each having an area enough to
fabricate a plurality of liquid crystal displays. A peripheral
sealing material 45a having an opening 45b is applied to surround
all the display regions or panels. The opening 45b is formed having
a length sufficient enough to prevent permeation of etchant used
during a digitizer formation process and to prevent compression of
air between the pair of glass substrate 41 during bonding process.
Then each display region is separated. The pair of glass substrates
41 is sufficiently large to fabricate a plurality of liquid crystal
display panels. Each display panel separated from the large glass
substrates 41 is injected with liquid crystal into the liquid
injection region 43 through a liquid injection port 47 provided at
a portion of the sealing material, the liquid crystal injection
port 47 is sealed, and a polarization plate is bonded at the back
of each display, to complete a liquid crystal display.
[0047] FIG. 7 illustrates a partial cut away view of glass
substrates of the present invention having an alternative display
panel configuration and having a sealing material applied thereto.
Referring to FIG. 7, the sealing material 85 is applied around each
liquid crystal injection region 83 of display regions defined on a
glass substrate 81 for the first time. Then sealing material 85a is
applied for the second time at an outer periphery of the sealing
material 85, spatially spaced from the sealing material 85. The
sealing material is applied twice around the display region, for
prevention of unwanted etching of pads (PAD) of the display by
etchant used during a digitizer formation process which follows.
That is, the sealing material is applied twice around the display
region, to protect the pads against HF solution when display
regions are separated. Then an outer sealing material 85b having an
opening 85c is applied to surround all the display regions. The
opening 85c is formed having a length sufficient enough to prevent
permeation of etchant used during a digitizer formation process and
to prevent compression of air between the first and second glass
substrates 21a and 21b during bonding process. After applying the
sealing materials twice around each display region and bonding the
first substrate 21a and the second substrate 21b, a digitizer 23a
is formed on a back side of at least one of the substrates 21a and
21b.
[0048] The aforementioned PSLCD of the present invention will be
explained in more detail. FIG. 8 illustrates a plan view of a
position sensing liquid crystal display in accordance with a first
embodiment of the present invention. Referring to FIG. 8, the PSLCD
in accordance with a first embodiment of the present invention
includes a liquid crystal panel 21 having a first substrate 21a and
a second substrate 21b bonded together, a digitizer 23a having
X-axis grids 51a and Y-axis grids 51b at a back surface of at least
one of the substrates 21a and 21b, and signal applying parts 27a,
27b, 27c, and 27d at four corners of the liquid crystal display
panel 21 for applying a position signal to the X-axis grids 51a and
the Y-axis grids 51b. The digitizer 23a is directly patterned on
the back surface of either the first substrate 21a or the second
substrate 21b of ITO or metal which has a high resistance. If the
X-axis grids 51a and the Y-axis grids 51b are formed of a metal,
the metal is patterned such that the X-axis grids 51a and the
Y-axis grids 51b are aligned or matched with the black matrix
pattern (see FIG. 5) formed on the first substrate 21a, for
obtaining a high aperture.
[0049] In order to make the black matrix pattern and the metal
pattern, the same alignment key used in formation of the black
matrix pattern on the first substrate 21a is used in metal
patterning. Alternatively, if the X-axis grids 51a and Y-axis grids
51b are formed of ITO, which is transparent, the X-axis grids 51a,
Y-axis grids 51b and the black matrix pattern 71 may not need to be
matched. The X-axis grids 51a and the Y-axis grids 51b form a
matrix with either an insulating layer or direct contact between
the X-axis grids 51a and the Y-axis grids 51b.
[0050] There is a compensating resistor region 53 between the
signal applying parts 27a, 27b, 27c, and 27d and the digitizer 23a
for transferring the position signal from the signal applying parts
27a, 27b, 27c, and 27d to the X-axis grids 51a and the Y-axis grids
51b. The compensating resistor region 53 includes equipotential
maintaining resistors 53b and equipotential compensating resistors
53c. The equipotential maintaining resistors 53b transmit the
position signal provided through the signal applying parts 27a,
27b, 27c, and 27d to the equipotential compensating resistors 53c,
and the equipotential compensating resistors 53c compensate
voltages such that the position signal received from the
equipotential maintaining resistors 53b has an equal potential on
entire surfaces of the X-axis and Y-axis grids.
[0051] In the aforementioned first embodiment of the present
invention, a position can be sensed using a stylus after
application of a position signal through the signal applying parts
27a, 27b, 27c, and 27d preferably at four corners of the liquid
crystal display panel 21. In this instance, a position of a stylus,
or a finger tip, can be sensed. First, position sensing in a case
of a stylus touch will be explained.
[0052] Referring to FIG. 8, the position signal provided through
the signal applying parts 27a, 27b, 27c, and 27d is applied to the
X-axis grids 51a and the Y-axis grids 51b through the compensating
resistor region 53 having the equipotential maintaining resistors
53b and the equipotential compensating resistors 53c. When the
stylus 29 is brought into contact at an arbitrary spot of the
digitizer 23a, a capacitive coupling is formed between the stylus
29 and a pertinent grid. Upon measuring and calculating the
capacitive coupling, the position of the stylus 29 can be detected.
If not a stylus touch, but a finger tip touch, is to be detected, a
position signal is applied the same as above, and a leakage current
flowing through a capacitive coupling between the finger tip, which
is a virtual ground, and a pertinent grid is measured in each of
the signal applying parts and calculated again, to sense the
position of the finger tip.
[0053] FIG. 9 illustrates a plan view of a position sensing liquid
crystal display in accordance with a second embodiment of the
present invention. In the second embodiment, the position sensing
digitizer 23a is not separately patterned in the X-axis and Y-axis
grids, but formed as an integral unit.
[0054] Referring to FIG. 9, the position sensing liquid crystal
display in accordance with the second embodiment of the present
invention includes a liquid crystal display panel 21 having a first
substrate 21a and a second substrate 21b attached together, a
position sensing digitizer 23a on a back surface of at least one of
the substrates 21a and 21b of the liquid crystal display panel 21
formed as an integral unit with the liquid crystal display panel
21, and signal applying parts 27a, 27b, 27c, and 27d in the near
vicinity of four corners of the liquid crystal display panel 21 for
applying a signal to the digitizer 23a. There are equipotential
maintaining resistors 53b and equipotential compensating resistors
53c provided between the signal applying parts 27a, 27b, 27c, and
27d and the digitizer 23a.
[0055] Preferably, the digitizer 23a is formed of an ITO layer,
which is transparent. Accordingly, when a position signal is
selectively applied to the signal applying parts 27a, 27b, 27c, and
27d, the stylus makes contact with a point on the digitizer 23a and
a capacitive coupling between the stylus and the digitizer 23a is
calculated, and thus a position of the stylus on the digitizer 23a
can be measured.
[0056] FIG. 10 illustrates a partial plan view of a PSLCD in
accordance with the first and second embodiments of the present
invention. Referring to FIG. 10, the PSLCD in accordance with the
first and second embodiments of the present invention includes a
signal applying part 27a for applying a voltage, a digitizer 23a
having a plurality of X-axis grids 51a and Y-axis grids 51b, and
compensating resistor regions 53 for providing equal potential from
the signal applying part 27a to the X-axis and Y-axis grids 51a and
51b in the digitizer 23a by regulating the potential with
resistors. The compensating resistor region 53 has node resistors
53a, equipotential maintaining resistors 53b, and equipotential
compensating resistors 53c. The equipotential maintaining resistors
53b are formed at four sides of the digitizer 23a, and the
equipotential compensating resistors 53c are connected between the
equipotential maintaining resistors 53b and the X-axis and Y-axis
grids 51a and 51b in the digitizer 23a.
[0057] The node resistor 53a transmits a position sensing signal
provided from the signal applying part 27a to the equipotential
maintaining resistors 53b. The equipotential compensating resistors
53c compensate voltages such that the nearest and farthest X-axis,
and Y-axis grids 51a and 51b from the signal applying part 27a are
at an equal potential. To accomplish this effect, the equipotential
compensating resistors 53c are patterned to have different lengths
as shown in FIG. 10. The position sensing signal passes through the
signal applying part 27a, the node resistor 53a, the equipotential
maintaining resistor 53, and the equipotential compensating
resistor 53c, and finally applied to the X-axis and Y-axis grids
51a and 51b. A longer equilibrium compensating resistor provides a
greater voltage drop between two points.
[0058] FIG. 11 illustrates a perspective view of a position sensing
liquid crystal display in accordance with a third embodiment of the
present invention. In the third embodiment, the signal applying
parts 27a, 27b, 27c, and 27d for applying a position signal for
detecting a position are disposed substantially in the middle of
each side of the digitizer 23a.
[0059] Referring to FIG. 11, the PSLCD in accordance with the third
embodiment of the present invention includes a liquid crystal
display panel 21 having a first substrate 21a affixed to a second
substrate 21b, a digitizer 23a having X-axis and Y-axis grids 51a
and 51b on a back surface of at least one of the substrates 21a and
21b, and signal applying parts 27a, 27b, 27c, and 27d at middle of
sides of the liquid crystal display panel 21 for applying a
position signal to the X-axis and Y-axis grids 51a and 51b. The
X-axis and Y-axis grids 51a and 51b are preferably formed of ITO or
metal.
[0060] Moreover, there is a compensating resistor region 53 between
the signal applying parts 27a, 27b, 27c, and 27d and the X-axis and
Y-axis grids 51a and 51b. The compensating resistor region 53
includes equipotential maintaining resistors 53b and equipotential
compensating resistors 53c. The equipotential maintaining resistors
53b transmit the position signal provided through the signal
applying parts 27a, 27b, 27c, and 27d to the equipotential
compensating resistors 53c, and the equipotential compensating
resistors 53c compensate voltages such that the position signal
received from the equipotential maintaining resistors 53b has an
equal potential on entire surfaces of the X-axis and Y-axis grids.
In the third embodiment of the present invention, the signal
applying parts 27a, 27b, 27c, and 27d are positioned preferably in
the middle of the four sides of the digitizer 23a to minimize the
separation distance from the signal applying parts 27a, 27b, 27c,
and 27d to the nearest and the farthest grids (X-axis and Y-axis
grids).
[0061] FIG. 12 illustrates a perspective view of a position sensing
liquid crystal display in accordance with a fourth embodiment of
the present invention. Referring to FIG. 12, the PSLCD includes a
liquid crystal display panel 21 having a first substrate 21a and a
second substrate 21b bonded together, a digitizer 23a on a back
surface of at least one of the substrates 21a and 21b, and signal
applying parts 27a, 27b, 27c, and 27d in the middle of the sides of
the liquid crystal display panel 21. The digitizer 23a is
preferably formed as an integral part of at least one of the
substrates 21a and 21b as opposed to a separate unit. There is a
compensating resistor region between the signal applying parts 27a,
27b, 27c, and 27d and the digitizer 23a for compensating voltages
such that the position signal provided from the signal applying
parts 27a, 27b, 27c, and 27d is substantially at an equal potential
all over the digitizer 23a. The operation of the fourth embodiment
PSLCD of the present invention is omitted as the operation is the
same with the first embodiment of the present invention.
[0062] FIG. 13 illustrates an alternative embodiment of the
compensating resistor region in the third and fourth embodiments of
the present invention. Referring to FIG. 13, another embodiment of
the compensating resistor region includes a tree shape of
repetitive sequence of layers of primary interconnections 130
between adjacent grids(Y-axis or X-axis grids), secondary
interconnections 133 between adjacent primary interconnections 130,
and tertiary interconnections 135 between adjacent secondary
interconnections 133. According to this, lengths of the
equipotential compensating resistors 130, 133, and 135 can be
patterned the same all over the regions of the digitizer so that
the position signal provided through the signal applying part 27a
(27b, 27c, and 27d are not shown) is linearly equipotential. The
X-axis grids 51a and the Y-axis grids 51b in the digitizer 23a form
a matrix with either an insulating layer or with direct contact
between the X-axis grids 51a and the Y-axis grids 51b. Thus, by
forming the equipotential compensating resistors in the
hierarchical or tree shape with repetitive sequential layers of
primary, secondary, tertiary, interconnections, lengths of passes
of a position signal applied from the signal applying part 27a to
respective grids can be patterned the same, hence achieving
substantially the same potential in X-axis and Y-axis grids.
[0063] A method for fabricating a PSLCD of the present invention
will be explained with reference to the flow chart shown in FIG.
14. Referring to FIG. 14, the method for fabricating a PSLCD of the
present invention starts with forming a first and a second
substrate (S101) and bonding the first and second substrates
together (S102). Then a highly resistant ITO (or metal) pattern is
formed on a back surface of at least one of the first and second
substrates, for use as a digitizer (S103). A low resistance metal
pattern is formed around the highly resistant pattern for use as
compensating resistors (S104). The joined first and second
substrates are scribed (S105). Liquid crystal is then injected
through a liquid injection port (S106), and then the liquid
injection port is sealed (S107). A polarizer and a protection films
are attached (S108) to complete a fabrication process of a
PSLCD.
[0064] For reference, the present invention is applicable to
displays in which two substrates are bonded together, such as TFT,
IPS mode LCD, STN mode LCD, and the like.
[0065] As described above, the PSLCD and the method for fabricating
the same of the present invention have the following advantages.
First, because the digitizer is directly formed on one of the upper
or lower plates, a separate digitizer glass is dispensed with, thus
minimizing thickness and weight of a PSLCD.
[0066] Second, the formation of the digitizer grid pattern using
the same alignment key used in patterning the upper and lower
plates allows an exact alignment of patterns of the substrate and
the digitizer, thus improving an aperture ratio and dispensing with
the requirement for a position correction due to a
misalignment.
[0067] Third, the formation of a digitizer on a back surface of
either the upper or lower plate in place of the inside of the LCD
panel, which provides greater spaces between various layers in the
LCD panel and the digitizer and minimizes parasitic capacitances
between the various layers and the digitizer, allows an accurate
position sensing.
[0068] Fourth, the digitizer can be formed adaptive to a size of
the LCD panel.
[0069] Fifth, the shorter distance from the finger tip to the
position sensing digitizer can improve a position sensing
sensitivity because a magnitude of a signal flowing through the
finger, a virtual ground, becomes greater when a fixed magnitude of
a position sensing signal is applied.
[0070] Sixth, the formation of the compensating resistors which
compensates an equipotential of the digitizer in tree-shaped
repetitive layers allows an accurate sensing of a position as an
accurate equipotential can be provided from the signal applying
part to the grids of the digitizer.
[0071] Seventh, the patterning of the digitizer on the front
surface of the first substrate or the rear surface of the second
substrate after bonding the first and second substrates prevents
damage of the black matrix layer formed on the rear surface of the
first or upper substrate.
[0072] Eighth, the double application of sealing material around
the liquid crystal injection region and display region in
separation of every display region can protect pads of the display
exposed outside of the display region.
[0073] It will be apparent to those skilled in the art that various
modifications and variations can be made in the position sensing
liquid crystal display and method for fabricating the same of the
present invention without departing from the spirit or scope of the
invention. Thus, it is intended that the present invention covers
the modifications and variations of this invention provided they
come within the scope of the appended claims and their
equivalents.
* * * * *