Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Magnetic or pressure excitation
Reexamination Certificate
1998-10-30
2001-09-04
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Magnetic or pressure excitation
Reexamination Certificate
active
06285417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Discussion of the Related Art
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
2
a
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
2
a
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.
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.
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
23
a
(hereafter called, “digitizer”), a compensating resistor region
25
around the digitizer
23
a
for compensating a voltage difference, and signal applying parts
27
a,
27
b,
27
c,
and
27
d
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
27
a
and
27
b
are applied at a position signal and the signal applying parts
27
c
and
27
d
are grounded, the digitizer
23
a
has a potential distribution from upper side to lower side thereof. When the signal applying parts
27
a
and
27
c
are applied at a position signal and the signal applying parts
27
b
and
27
d
are grounded, the digitizer
23
a
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
23
a
after selective application of a position sensing signal to the signal applying parts
27
a,
27
b,
27
c,
and
27
d,
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
24
a
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.
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
21
a,
a lower plate
21
b,
and a digitizer
23
a
between the upper plate
21
a
and the lower plate
21
b.
As explained, the upper plate
21
a
has the black matrix layer (not shown), a color filter layer, and an ITO layer of a common electrode formed thereon. The lower plate
21
b
has data lines
31
, gate lines
33
, and pixel electrodes (not shown), and the digitizer
23
a
has a compensating resistor region
25
around the digitizer and signal applying parts
27
b
and
27
d
at four corners of the compensating resistor region
25
(signal applying parts
27
a
and
27
c
are not shown).
In the second PSLCD, when the signal applying parts
27
a,
27
b,
27
c
and
27
d
are applied of a position signal, the digitizer
23
a
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
23
a
after selective application of position signal through signal applying parts
27
a,
27
b,
27
c,
and
27
d,
the PSLCD can sense the present position of the stylus
29
by using a capacitive coupling between the digitizer
23
a
and the stylus
29
.
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.
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.
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
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.
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.
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.
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 abutti
Ahn Young Soo
Bae Sung Joon
Dudek James A.
LG.Philips LCD Co. , Ltd.
Long Aldridge & Norman LLP
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