U.S. patent application number 15/942049 was filed with the patent office on 2019-10-03 for touch sensor for display with shield.
The applicant listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Nick CLARK, Tim Michael SMEETON.
Application Number | 20190302959 15/942049 |
Document ID | / |
Family ID | 68056158 |
Filed Date | 2019-10-03 |
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United States Patent
Application |
20190302959 |
Kind Code |
A1 |
CLARK; Nick ; et
al. |
October 3, 2019 |
TOUCH SENSOR FOR DISPLAY WITH SHIELD
Abstract
A display device includes a display panel including a plurality
of sub-pixels; a shield electrode that is made of a first
conductive and opaque material, is located directly on the display
panel, overlaps a portion of the display panel in between a portion
of the plurality of sub-pixels, and is connected to a touch sensor
controller; an insulating layer that covers the shield electrode; a
touch sensor electrode that is made of a second conductive and
opaque material, is located on the insulating layer, overlaps a
portion of the display panel in between some of the plurality of
sub-pixels, and overlaps the shield electrode; and a feedline is
connected to the touch sensor electrode, overlaps a portion of the
display panel in between a portion of the plurality of sub-pixels
that is not overlapped by the touch sensor electrode, and routes
the touch sensor electrode to the touch sensor controller.
Inventors: |
CLARK; Nick; (Oxford,
GB) ; SMEETON; Tim Michael; (Oxford, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Osaka |
|
JP |
|
|
Family ID: |
68056158 |
Appl. No.: |
15/942049 |
Filed: |
March 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 3/0412 20130101;
G06F 3/0443 20190501; G06F 2203/04112 20130101; G06F 3/04164
20190501; G06F 2203/04107 20130101; G06F 3/0418 20130101; G06F
3/044 20130101 |
International
Class: |
G06F 3/041 20060101
G06F003/041; G06F 3/044 20060101 G06F003/044 |
Claims
1. A display device comprising: a display panel including a
plurality of sub-pixels; a shield electrode that is made of a first
conductive and opaque material, is located directly on the display
panel, overlaps a portion of the display panel in between a portion
of the plurality of sub-pixels, and is connected to a touch sensor
controller; an insulating layer that covers the shield electrode; a
touch sensor electrode that is made of a second conductive and
opaque material, is located on the insulating layer, overlaps a
portion of the display panel in between some of the plurality of
sub-pixels, and overlaps the shield electrode; and a feedline that
is made of the second conductive and opaque material, is connected
to the touch sensor electrode, overlaps a portion of the display
panel in between a portion of the plurality of sub-pixels that is
not overlapped by the touch sensor electrode, and routes the touch
sensor electrode to the touch sensor controller.
2. The display device of claim 1, wherein the shield electrode, the
touch sensor electrode, and the feedline overlaps only a
non-emission region between the plurality of sub-pixels.
3. The display device of claim 1, wherein the shield electrode is
provided with a same voltage or substantially a same voltage as the
touch sensor electrode.
4. The display device of claim 1, wherein the shield electrode is
electrically isolated from the touch sensor electrode.
5. The display device of claim 1, wherein a width of a portion of
the shield electrode that overlaps the feedline is wider than a
width of the feedline.
6. The display device of claim 5, wherein the shield electrode
includes a connecting portion connecting the portion of the shield
electrode that overlaps the feedline to a portion of the shield
electrode that overlaps an adjacent feedline, and a width of the
connecting portion is narrower than the width of the feedline.
7. The display device of claim 1, wherein a pattern of the shield
electrode between the feedline and an adjacent feedline is the same
or substantially the same as a pattern of the touch sensor
electrode.
8. The display device of claim 1, wherein a width of a portion of
the shield electrode overlapping the feedline is equal or
substantially equal to a width of the feedline.
9. The display device of claim 8, wherein the shield electrode
includes a connecting portion connecting the portion of the shield
electrode that overlaps the feedline and a portion of the shield
electrode that overlaps an adjacent feedline, and a width of the
connecting portion is equal to or substantially equal to the width
of the feedline.
10. The display device of claim 1, wherein the feedline includes a
serpentine or zig-zag pattern in between adjacent sub-pixels of the
plurality of sub-pixels.
11. The display device of claim 1, wherein the shield electrode is
wider than the touch sensor electrode adjacent to a corner of the
touch sensor electrode or the feedline.
12. The display device of claim 1, wherein a triangular shaped
portion of the shield electrode extends beyond an edge of the touch
sensor electrode or the feedline in an area adjacent to a corner of
the touch sensor electrode or the feedline in which the shield
electrode overlaps.
13. The display device of claim 1, wherein a curved shaped portion
of the shield electrode extends beyond an edge of the touch sensor
electrode or the feedline in an area adjacent to a corner of the
touch sensor electrode or the feedline in which the shield
electrode overlaps.
14. The display device of claim 1, wherein a distance between an
edge of the touch sensor electrode and a nearest edge of one of the
plurality of the sub-pixels is at least a distance which provides a
direction at an angle relative to perpendicular to a front surface
plane of the display device between the edge of the touch sensor
electrode and the nearest edge of the sub-pixel which is equal to a
maximum escape angle for light from the one of the plurality of
sub-pixels.
15. The display device of claim 1, wherein a distance between an
edge of the feedline and a nearest edge of one of the plurality of
the sub-pixels is at least a distance which provides a direction at
an angle relative to perpendicular to a front surface plane of the
display device between the edge of the touch sensor electrode and
the nearest edge of the sub-pixel which is equal to a maximum
escape angle for light from the one of the plurality of
sub-pixels.
16. The display device of claim 1, wherein a distance between an
edge of the shield electrode and a nearest edge of one of the
plurality of the sub-pixels is at least a distance which provides a
direction at an angle relative to perpendicular to a front surface
plane of the display device between the edge of the touch sensor
electrode and the nearest edge of the sub-pixel which is equal to a
maximum escape angle for light from the one of the plurality of
sub-pixels.
17. The display device of claim 1, wherein the display panel is an
emissive display panel.
18. The display device of claim 1, wherein a coverage of the first
conductive and opaque material and the second conductive and opaque
material of the touch sensor in a plan view of a feedline region is
between about 50% and about 150% of a coverage of the first
conductive and opaque material and the second conductive and opaque
material of the touch sensor in a touch electrode region.
19. The display device of claim 1, wherein the a coverage of the
first conductive and opaque material and the second conductive and
opaque material of the touch sensor in a plan view of a feedline
region is between about 80% and about 120% of the coverage of the
first conductive and opaque material and the second conductive and
opaque material of the touch sensor in a touch electrode
region.
20. The display device of claim 1, wherein the feedline overlaps
the shield electrode.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention is directed to a touch sensor for an
electronic display system. More specifically, the present invention
relates to a self-capacitive touch sensor and a shield electrode
provided directly on an electronic display panel and a method of
fabricating the same.
2. Description of the Related Art
[0002] An electronic display is a device, panel, or screen that
visually presents images, text, or video that is transmitted
electronically. Examples of electronic displays are used as
components in televisions, computer monitors, digital signage,
smart phones, and tablet computers. Display devices can either emit
light, i.e., emissive type, or modulate light, i.e., non-emissive
type.
[0003] An organic light emitting-diode (OLED) display device is an
emissive type electronic display that includes an organic light
emitting display panel and driver electronics to control the
organic light emitting display panel. The organic light emitting
display panel includes a matrix of sub-pixels with each sub-pixel
including an organic light emitting-diode and a driving thin-film
transistor (TFT). OLED displays are multi-color with a wide viewing
angle, high contrast, and fast response speed.
[0004] An OLED display panel includes a pixel layer having colored
sub-pixels, typically a combination of red, green, and blue (R, G,
B). The pixel layer is typically constructed with two electrodes
and an organic light-emitting layer between the two electrodes. The
two electrodes include an anode electrode and a cathode electrode,
which are applied with different voltages. The pixel layer is
usually protected by an encapsulation or sealing layer that may
include multiple thin layers or a sealing substrate.
[0005] A liquid crystal display (LCD) is a non-emission type
display that includes a liquid crystal panel and driver electronics
to control the liquid crystal panel. LCD panels include a series of
cells that can each be driven independently to modulate input
light. An active-matrix liquid-crystal display (AMLCD) includes a
matrix of cells or sub-pixels with each sub-pixel including a
switching TFT. The TFTs store the electrical state of each
sub-pixel on the display while all the other sub-pixels are being
updated. The sub-pixels typically include a corresponding red,
green, or blue color filter driven in combination to form a color
gamut.
[0006] A typical LCD includes an array substrate including the TFTs
and connecting signal lines, an opposing substrate including the
color filter, and a liquid crystal layer in between the two
substrates. The driving electronics are used to create a voltage
potential between a pixel electrode and a common electrode at each
pixel to modulate adjacent liquid crystals in the liquid crystal
layer.
[0007] The OLED display and LCD are increasingly popular, but other
pixelated emissive and non-emissive type electronic display
technologies are also well known.
[0008] Touch screens are widely used with electronic displays,
especially for smart phones and mobile electronic devices. A touch
screen is an input device that can be joined with an electronic
display device to facilitate user interaction and control. Such
devices typically include a touch sensor mounted on a surface of an
electronic display that displays interactive information and
control electronics to interpret a touch on the touch sensor.
[0009] Touch screen devices detect the location of an external
touch or gesture of a finger, stylus, or similar object that occurs
at or near the surface of the touch sensor. Such touch screens
include a matrix of transparent conductive elements or electrodes
that form a touch sensor that overlay the display device and
separate control electronics to determine the location of the touch
object near or in contact with the touch sensor. Touch sensors are
typically transparent so the user can view displayed information on
the display device through the touch-sensor. By physically
touching, or nearly touching, the touch sensor in a location
associated with displayed information, a user can select an
operation associated with the displayed information. The touch
sensor detects the touch and then electronically interacts with the
control electronics, or controller, to determine and output the
touch location. The output signal of the touch location is input to
a processor that associates the touch location or gesture with the
displayed information to execute a programmed task associated with
the displayed information as a graphic user interface.
[0010] Touch screens can use a variety of technologies, including
resistive, inductive, capacitive, acoustic, piezoelectric, and
optical to locate a touch or gesture on a sensor.
[0011] Capacitive touch-screens are of at least two different
types: self-capacitive and mutual-capacitive. Self-capacitive
touch-screens use an array of transparent electrodes on the sensor
in combination with the touching object to form a temporary
capacitor, a capacitance of which is detected. Mutual-capacitive
touch-screens use an array of transparent electrode pairs that form
capacitors, a capacitance of which is affected by the touching
object. In both types, each capacitor in the array is sensed to
detect a touch, and the physical location of the touch-detecting
electrode in the touch-screen corresponds to the location of the
touch.
[0012] As mentioned, touch sensors are typically transparent or
formed to be invisible to the user and minimize optical
distractions and artifacts. While interacting with the display
panel, the touch sensor should minimize ambient reflection,
maximize display transmission, not interfere with display viewing
angle, and not cause any Moire patterns or other optical
interference effects. Electrically, the touch sensor should be
highly conductive and uniform to maximize sensitivity and minimize
voltage potential gradients. Touch sensors are either transparent
conductive materials or conductive elements that are spaced apart
and are too small to be seen by the user.
[0013] A typical transparent touch sensor includes a patterned
coating of a conventional transparent conducting material (TCM)
such as a transparent conducting oxide (TCO) or indium tin oxide
(ITO). Disadvantages of such designs include limited transparency
and conductivity and increased sensitivity to mechanical or
environmental stress. Thicker layers of conventional TCM increase
conductivity and resistance to stress but reduce the transparency
of the electrodes.
[0014] For increased conductivity and to overcome issues of touch
sensors made from conventional TCM, touch sensors can be made from
grid patterns of fine metal wires, meshes, or conductive traces.
These micro-wires are opaque, but are meant to be fine enough and
spaced apart so that they are normally not detectable by the user.
Although more uniformly conductive than conventional TCM designs,
patterns of micro-wire electrodes can visibly interact with pixels
in a display and cause Moire patterns and other optical
interference artifacts.
[0015] In order to reduce the device thickness as much as possible,
the touch sensor can be formed directly on the display, and the
display and touch sensor can be manufactured in the same process.
This can result in the reduction of production costs compared with
production of the display and touch sensor as separate components
and subsequently combining them together. However, because a
manufacturing defect in the touch sensor results in the wasted
production of the display, features that increase the manufacturing
yield of the touch sensor are advantageous.
SUMMARY OF THE INVENTION
[0016] To overcome the problems described above, a preferred
embodiment of the present invention provides a display device
including a display panel including a plurality of sub-pixels; a
shield electrode that is made of a first conductive and opaque
material, is located directly on the display panel, overlaps a
portion of the display panel in between a portion of the plurality
of sub-pixels, and is connected to a touch sensor controller; an
insulating layer that covers the shield electrode; a touch sensor
electrode that is made of a second conductive and opaque material,
is located on the insulating layer, overlaps a portion of the
display panel in between some of the plurality of sub-pixels, and
overlaps the shield electrode; and a feedline that is made of the
second conductive and opaque material, is connected to the touch
sensor electrode, overlaps a portion of the display panel in
between a portion of the plurality of sub-pixels that is not
overlapped by the touch sensor electrode, and routes the touch
sensor electrode to the touch sensor controller.
[0017] The above and other features, elements, characteristics,
steps, and advantages of the present invention will become more
apparent from the following detailed description of preferred
embodiments of the present invention with reference to the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1A is a side view of an OLED display panel and touch
sensor according to a preferred embodiment of the present
invention.
[0019] FIG. 1B is a plan view of the OLED display panel showing
three OLED sub-pixels from FIG. 1A.
[0020] FIG. 2 is a graph of parasitic capacitance with different
separations between a touch electrode and an upper display
electrode of an adjacent OLED sub-pixel.
[0021] FIG. 3 is a plan view of a touch panel configuration
according to a preferred embodiment of the present invention.
[0022] FIG. 4 is a plan view of a shield electrode structure
according to a preferred embodiment of the present invention.
[0023] FIG. 5 shows a representative portion of an OLED display
panel with a first sub-pixel distribution layout according to a
preferred embodiment of the present invention.
[0024] FIG. 6 shows a representative portion of an OLED display
panel with a second sub-pixel distribution layout according to a
preferred embodiment of the present invention.
[0025] FIG. 7A shows a configuration of feedlines according to a
preferred embodiment of the present invention.
[0026] FIG. 7B shows a configuration of a touch electrode according
to a preferred embodiment of the present invention.
[0027] FIG. 8 shows a configuration of a touch electrode,
feedlines, and a shield electrode according to a preferred
embodiment of the present invention.
[0028] FIG. 9 is a representative side view of an OLED display
panel including a shield electrode with the same width as the
feedline and a shield electrode wider than the feedline in
accordance with a preferred embodiment of the present
invention.
[0029] FIGS. 10A-10C show a preferred embodiment of the present
invention where the shield electrode area is increased in regions
where the touch electrode includes an internal corner.
[0030] FIG. 11 shows a representative portion of touch electrode
and a shield electrode similar to that in the views of FIGS.
10A-10C with a misalignment.
[0031] FIG. 12 shows a calculated model of the percentage of touch
electrode area overlapped by the shield electrode against a
relative percentage of only horizontal alignment error for a
configuration of preferred embodiments of the present invention
where the width of the touch electrode is the same as the width of
the shield electrode in between subpixels.
[0032] FIG. 13 shows a configuration of a touch electrode,
feedlines, and a shield electrode according to a preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] Preferred embodiments of the present invention provide a
self-capacitive touch sensors for use with electronic displays. In
a preferred embodiment of the present invention, a shield electrode
pattern layer can be provided directly on the encapsulation layer
of an OLED pixel layer or a substrate of an LCD closest to the
sub-pixels and connected to a touch sensor controller. In addition,
in a preferred embodiment of the present invention, a touch sensor
pattern layer can be formed or disposed directly on an insulation
layer covering the shield electrode pattern and connected to a
touch sensor controller to detect an external touch input. For
convenience, the touch sensors of various preferred embodiments of
the present invention will be described below with respect to an
OLED display, but one of ordinary skill in the art will appreciate
that the present touch sensors can be used with LCDs or any
suitable electronic display technology.
[0034] A display panel includes a collection of sub-pixels on a TFT
substrate covered with a continuous transparent encapsulation
material or substrate. A touch sensor includes a collection of
touch electrodes and associated feedlines which connect the touch
electrodes to a touch sensor controller. This creates a touch
system that detects the position, in up to 3 dimensions, of a touch
object relative to the display. The assembly of both the display
panel and the touch sensor is referred to as the display
device.
[0035] As noted above, self-capacitive operation means that the
capacitance of an electrode is measured between the touch electrode
and a ground, a reference voltage of the touch sensor controller,
or another portion of a display. In a mutual-capacitive operation,
the capacitance is measured between different touch electrodes.
Self-capacitive designs have the advantage of being more sensitive
than mutual-capacitive designs.
[0036] Rather than combining two separate display panel and touch
sensor components, the touch sensors of preferred embodiments of
the present invention can be formed or disposed directly on the
display panel to significantly reduce or minimize thickness.
[0037] A number of challenges and design requirements exist when
developing a touch sensor for operation with an electronic display.
The touch sensor wiring and an adjacent electrode of the display
panel can create a parasitic capacitance. By reducing the distance
between a touch electrode or feedline and an electrode on the
display panel, electromagnetic forces between the touch electrode
or feedline and the electrode on the display panel will generate
increased parasitic capacitance. This can be best illustrated by
the well-known parallel plate capacitor equation, C=.epsilon.A/d
where, d is the distance between the touch electrode or feedline
and the display electrode at the reference potential, .epsilon. is
the permittivity of the dielectric separating the touch electrode,
and A is the area overlapping between the touch electrode or
feedline and the display electrode at the reference potential. A
touch sensor formed directly on an OLED display is therefore
susceptible to high parasitic capacitances. In particular, the OLED
cathode electrode may be formed directly below the encapsulation
layer and only separated from the touch electrodes and feedlines
by, for example, 10 .mu.m.
[0038] It is advantageous to significantly reduce or minimize
parasitic capacitance that is created between the touch sensor
electrode and a closest electrode of the OLED pixel. First, the
touch electrode and the feedline that connects the touch electrode
to the touch controller form a series resistor-capacitor (RC)
circuit where the voltage across the capacitor has an exponential
response with a time-constant related to the RC. Therefore,
reducing the parasitic capacitance reduces the charge time of the
capacitor formed between the touch electrode and feedline and the
OLED sub-pixel electrode to allow faster operation. Second, many
available touch sensor controllers impose limits on the size of the
parasitic capacitance and by reducing the absolute parasitic
capacitance, the preferred embodiments of the present invention
offer the widest compatibility with available touch sensor
controllers.
[0039] To allow for a wide range of user input and compatibility
with modern software systems, touch sensors require the ability to
simultaneously detect multiple user touches. For a self-capacitive
design, this can only be achieved by sensing of individual touch
electrodes. Individual electrode sensing requires that each
electrode is fed by an individual feedline routed past adjacent
touch electrodes. In conventional designs, owing to the low
conductivity of the feedline material, the feedlines are made wide
to keep their resistance low. For larger panels, the wide feedlines
necessitate large spacing between touch electrodes. The increase in
touch electrode pitch will reduce touch resolution.
[0040] Further, wide feedlines can necessitate use of touch
electrodes of varying size to ensure sufficient space for passing
feedlines and varying sizes of the touch electrodes introduces
non-uniformity of parasitic capacitance and sensitivity between
touch electrodes causing poor sensitivity and inconsistent touch
response across the touch sensor. To reduce the difference in
capacitance values or dynamic range among the touch electrodes,
maintain sensitivity across the touch sensor, and minimize the
complexity and cost of the touch sensor controller, it is desirable
that the capacitance, the RC constant, the size of touch
electrodes, and the spacing between them be controlled and uniform
across the touch sensor.
[0041] It is noted that a portion of the parasitic capacitance is
attributed to the touch electrode and another portion of the
parasitic capacitance is attributed to its associated feedline.
False detection occurs when the touch sensor incorrectly reports
the detection of the touch object due to the touch object's effect
on the capacitance of a feedline. That is, a change in capacitance
of a feedline caused by a touch object can be wrongly interpreted
as a touch to be detected at the electrode that the feedline is
connected to. Therefore, for the same reasons as outlined above, it
is advantageous to reduce the parasitic capacitance and the
sensitivity, i.e., maximum change in capacitance on the
introduction of the touch object to the feedlines.
[0042] As mentioned above, a small RC constant is desired.
Therefore, it is beneficial to increase the material conductivity
to reduce the resistance of the feedlines and touch electrodes. In
addition to making the design more tolerant to high capacitances,
higher conductivity/lower resistance materials allow for longer
feedlines, larger touch sensor designs, and reduced power
consumption.
[0043] With respect to optical performance of the display panel
combined with the touch sensor, any light emitted by or through the
display panel but blocked by the touch sensor will require more
power to match the light output of a display panel without touch
capability. This must be considered across the full range of
viewing angles. For instance, in the case of a touch sensor
including touch electrodes or feedlines of opaque material
according to a preferred embodiment of the present invention,
increases in the thickness of the opaque material, reduction in the
horizontal proximity between the opaque material and sub-pixels,
and an increase in the vertically proximity between the opaque
material and sub-pixels of the display panel may cause blocking of
emitted light propagating in a direction that would otherwise be
emitted, as shown for the light labelled BL in FIG. 1A. Light
propagating in a direction that would otherwise be emitted is any
light emitted from the sub-pixel which propagates in a direction
which would be transmitted into air (i.e. would not be subject to
total internal reflection at the interface between the display
device and air). This describes the maximum escape angle, measured
relative to the normal of the front surface of the display device,
of light for the medium the light is propagating within, which is
arc sin(1/n), where n is the refractive index of the medium the
light is propagating in, for example, the encapsulation layer
ENCAP. Also, any non-uniformity in the appearance, caused by both
the emitted light and the reflected ambient light, of the display
panel with touch sensor detracts from its optical quality.
[0044] Preferred embodiments of the present invention solve the
above described problems as described in detail below.
[0045] FIG. 1A is a side view of a display device 100 including an
OLED display panel OLED and touch sensor TS of a preferred
embodiment of the present invention. As shown in FIG. 1A, the
display device 100 includes a substrate SUB, a TFT layer TFT on the
substrate SUB, a lower display electrode LDE and a bank BNK on the
TFT layer TFT, an OLED sub-pixel SUB-PIX on the lower display
electrode LDE, an upper display electrode UDE on the OLED sub-pixel
SUB-PIX, and an encapsulation layer ENCAP covering the OLED
sub-pixel define the OLED display panel OLED. FIG. 1A shows three
OLED sub-pixels SUB-PIX. FIG. 1B is a plan view of the OLED display
panel OLED showing three OLED sub-pixels SUB-PIX. Light is emitted
from the OLED sub-pixels SUB-PIX, and regions in between the OLED
sub-pixels SUB-PIX are non-emissive regions NER. In FIG. 1A, the
lower and the upper display electrodes LDE, UDE can include a
single cathode or anode electrode or a plurality of cathode or
anode electrodes. As shown in FIG. 1A, the OLED sub-pixel SUB-PIX
includes charge transport layers CTL1, CTL2 and a light emitting
layer EML. A conductive and opaque material is provided on the
encapsulation layer ENCAP and is patterned to define a shield
electrode SE. An insulating layer INS is provided on the shield
electrode SE. Preferably, the insulating layer INS can be, for
example, one of silicon nitride, silicon oxide, polyimide, and
acrylic, or any other suitable material. The touch electrodes and
feedlines of the touch sensor TS are made of an electrically
conductive and opaque material on the insulating layer INS, as
shown in FIG. 1A. Optionally, dummy and/or enhancement electrodes
can also be defined in the same electrically conductive and opaque
material layer as the touch electrodes and feedlines. Dummy
electrodes are electrodes which are not connected to a voltage
source such that they are electrically floating. Enhancement
electrodes are electrodes which are connected to a voltage source,
for example from the touch sensor controller. Dummy electrodes and
enhancement electrodes may be disposed in between two touch
electrodes, in between two feedlines, and in between a touch
electrode and a feedline. Dummy electrodes and enhancement
electrodes can be used to increase the sensitivity (change in
capacitance) of touch electrodes in response to a touch and improve
the visual appearance of a display by providing similar average
coverage of conductive and opaque material of the touch sensor in
different regions of the display device. Optionally, a polarizer
POL and/or cover material CVR can be laminated on the touch sensor
TS with optically clear adhesive OCA.
[0046] As illustrated in FIG. 1A, the insulating layer INS provides
separation and electrical isolation between the shield electrode SE
and the touch sensor TS. Both the shield electrode SE and the touch
sensor TS are preferably patterned between the OLED sub-pixels such
that they do not overlap with the sub-pixels. Therefore, there is
no reduction in emitted light EL at and close to the normal viewing
angle. Also, as compared with a conventional transparent touch
sensor that is continuous over the display panel, the parasitic
capacitance between the touch sensor TS and upper display electrode
UDE is reduced due to the reduced area of the touch electrodes and
feedlines. The shield electrode SE is provided to reduce the
parasitic capacitance between the touch sensor TS and the upper
display electrode UDE by blocking the electric field between the
touch electrodes and the upper display electrode UDE. Preferably,
the insulating layer INS between the touch sensor TS and shield
electrode SE is very thin (e.g., less than about 10 .mu.m,
preferably less than about 1 .mu.m, and most preferably about 100
nm), in order to maximize the effectiveness of the shield electrode
by reducing the parasitic capacitance. A thin insulating layer INS
also reduces the vertical proximity between the conductive and
opaque materials of the touch sensor TS and emissive regions of the
sub-pixels, thereby reducing the extent of, or eliminating,
blocking by the touch sensor TS of light emitted by the sub-pixels
which propagates in a direction which would otherwise be emitted
from the display device (i.e. reducing the extent of, or
eliminating, blocked light BL).
[0047] The calculated effects of a shield electrode on parasitic
capacitance is shown in the graph of FIG. 2. This graph shows the
result of a 3-dimensional finite element numerical analysis of the
parasitic capacitance, with and without a shield electrode, between
a touch electrode and upper display electrode of an OLED sub-pixel
where the shield electrode and touch electrode or the touch
electrode alone is deposited directly on the encapsulation layer of
the OLED display. The graph in FIG. 2 plots the ratio of the
parasitic capacitance of a touch electrode with the shield present
C.sub.Shield to parasitic capacitance of the touch electrode
without the shield present C as the vertical axis with respect to
the sub-pixel pitch of the display panel along the horizontal axis
with three different distances of separation (.delta.) between the
touch electrode and shield electrode. The touch electrode is
patterned with a regular square grid structure having a pitch equal
to the sub-pixel pitch and with wire sections 5 .mu.m wide. The
shield electrode is patterned to be aligned with and to have an
identical shape as the touch electrode. The upper display electrode
of the OLED is a continuous conducting layer. For the structure
with a shield layer, the distance between the upper display
electrode and the shield electrode is 10 .mu.m. For the structure
without a shield electrode, the distance between the upper display
electrode and the touch electrode is 10 .mu.m. The shield electrode
is electrically isolated from the touch electrode but is driven at
the same potential as the touch electrode. The results show that
the parasitic capacitance is significantly reduced by the shield
electrode. Advantageously, the shield electrode significantly
reduces the parasitic capacitance even though the shield electrode
does not overlap with the sub-pixels.
[0048] The touch electrodes and feedlines may preferably be defined
in a single layer of conductive and opaque material. This allows
for low cost manufacturing. The conductive and opaque material can
be, for example, one of titanium, aluminum, copper, silver, gold,
molybdenum, zinc, tungsten, nickel, tin, platinum, graphene, or any
alloy thereof, but is not limited thereto. Optionally, the
conductive and opaque material can be a stack of multiple layers,
for example, a sequence of Ti/Al/Ti layers or combination of the
other materials mentioned, but is not limited thereto. The same
conductive and opaque material(s) is preferably deposited and
patterned to define all of the touch electrodes and feedlines in a
shared process, but different materials, deposition process and
patterning process may be used for the touch electrodes and
feedlines. The conductive and opaque material of the shield
electrode can be, for example, one of titanium, aluminum, copper,
silver, gold, molybdenum, zinc, tungsten, nickel, tin, platinum,
graphene, or any alloy thereof, but is not limited thereto.
Optionally, the conductive and opaque material of the shield
electrode can be a stack of multiple layers, for example, a
sequence of Ti/Al/Ti layers or combination of the other materials
mentioned, but is not limited thereto. Preferably the material of
the shield electrode and the material of the touch sensor have
similar optical reflectivities, thereby providing similar visual
appearance with respect to reflection of ambient light under some
embodiments of the present invention. The conductive and opaque
material may be deposited by evaporative coating in a vacuum and
patterned using a standard photoresist and etch process, for
example, with a wet chemical etch or a reactive gas etch. An
insulating layer INS of silicon oxide or silicon nitride may be
deposited by plasma enhanced chemical vapor deposition; and an
insulating layer INS of acrylic or polyimide may be deposited from
a chemical precursor solution. Furthermore, because the shield
electrode SE and touch sensor TS are each preferably defined in
single layers of the conductive and opaque material, all of the
conductive and opaque material is located close to the plane of the
light emission from the OLED. This reduces the extent of, or
eliminates, blocking of light from the OLED sub-pixels SUB-PIX
which propagates in a direction which would otherwise propagate at
a high polar viewing angle (a polar viewing angle .theta. is shown
in FIG. 1A). An example of a direction of blocked light BL is shown
in FIG. 1A. This configuration is preferable to a configuration
using conventional TCMs in thick layers because these materials are
only partially transparent and cannot be used in thick layers
without causing high absorption or reflection of light from the
OLED sub-pixels SUB-PIX.
[0049] Preferably the conductive and opaque material has a
conductivity significantly higher than that provided by
conventional TCMs. Therefore, the parasitic capacitance of the
touch electrodes and feedlines can be lowered without increasing
resistance. Thus, the conductive and opaque material of touch
sensors of preferred embodiments of the present invention can be
very thin and narrow with low resistance.
[0050] Also, the conductivity of the conductive and opaque material
of preferred embodiments of the present invention is high enough
that a feedline may have a width small enough to be entirely
between adjacent sub-pixels, while not overlapping with these
sub-pixels. Thus, the problems associated with wide feedlines
discussed above is avoided. Furthermore, increased conductivity of
feedlines allows for larger designs (i.e., touch sensors on display
panels with larger areas such that the feedlines connecting
electrodes to a touch panel controller are long) without their
resistance becoming problematically high.
[0051] FIG. 3 shows an exemplary grid layout of the touch
electrodes 300 with an individually connected feedline 310
according to a preferred embodiment of the present invention. The
outlines of the touch electrode 300 and the connected feedline 310
in FIG. 3 indicate the outer extents of the touch electrodes 300
and feedlines 310; the structure whereby the touch electrodes 300
and feedlines 310 are not overlapping with the sub-pixels is not
shown. At the sub-pixel scale, the edges of the touch electrodes
300 and feedlines 310 may not be straight lines, as in FIG. 3. In
this configuration, not all of the sub-pixels of the display panel
are enclosed within a touch electrode 300. As shown in FIG. 3, the
feedlines 310 are routed to a touch sensor controller 320 that is
at an edge of or off the display panel. The touch sensor controller
320 can be directly bonded to a substrate of the display panel or
connected to the feedlines 310 using another connection method.
FIG. 3 also shows a shield electrode 330 connected to the touch
sensor controller 320 via a shield feedline 340. The outline of the
shield electrode 330 indicates the outer extent of the shield
electrode 300; the structure whereby the shield electrode is not
overlapping with the sub-pixels is not shown. At the sub-pixel
scale, the edges of the shield electrode 330 may not be straight
lines, as in FIG. 3. Overall, FIG. 3 shows a self-capacitive touch
sensor and a shield layer of a display panel each made from a
conductive and opaque material that has higher conductivity than
conventional TCM devices, wherein the conductive and opaque
materials of the touch sensor and shield layer do not overlap the
sub-pixels.
[0052] An alternative shield electrode structure can be seen in
FIG. 4, in which first regions of the shield electrode 430 (i.e.,
the square regions) align with the positions of the touch
electrodes 300 in the touch sensor layer. Preferably the size
and/or shape of the first regions of the shield electrode 430 are
similar or identical to those of the touch electrodes 300 they are
aligned with. FIG. 4 shows that multiple first regions of the
shield electrode 430 are each connected together and are routed
with multiple shield feedlines 440 to the touch sensor controller
420.
[0053] Preferred embodiments of the present invention preferably
include the grid layout patterns of the touch electrodes 300 and
feedlines 310 and the shield electrode 330 and 430 and shield
feedlines 340 and 440 as shown in FIGS. 3 and 4. However, such an
arrangement is not mandatory. Preferred embodiments of the present
invention may also include different sub-pixel layouts, such as the
first and second sub-pixel distributions, as shown in FIGS. 5 and
6, for example.
[0054] FIG. 5 shows a representative portion of the OLED display
panel with the first sub-pixel distribution layout where edges of
the sub-pixels (R, G, B) 500 are aligned parallel or substantially
parallel with a rectangular display panel edge DPE.
[0055] FIG. 6 shows a representative portion of the OLED display
panel with the second sub-pixel distribution layout where edges of
the sub-pixels (R, G, B) 600 are aligned at 45.degree. with the
rectangular display panel edge DPE.
[0056] In all sub-pixel distributions, the sub-pixels can be of
different sizes and shapes or of equal size (e.g., red sub-pixels
may be different size and shape compared with green subpixels). The
sub-pixels can be grouped into one or more groups of equal size
and/or the same color. For example, the sub-pixel shape may be
square, rectangular, rounded, have rounded corners, curved edges,
or 5 or more straight edges. One sub-pixel may include more than
one separate emissive region, each of which emits substantially the
same color of light, for example.
[0057] The operation of the touch sensor involves the repeated
measurement, simultaneously or in-turn, of the capacitance, with
respect to a touch sensor controller reference voltage or ground,
of each touch electrode. Optionally, the operation of the touch
sensor involves the repeated measurement, simultaneously or in
turn, of the capacitance, with respect to an electrode of the OLED
(preferably the upper display electrode UDE), of each touch
electrode. There are various techniques to measure capacitance,
including but not limited to, Charge transfer, Delta-sigma
modulation, Relaxation oscillator, and Charge time measurement. All
techniques will involve the application of one or many voltage (the
drive voltage) pulses to the touch electrodes such that an electric
field is projected from the touch electrodes.
[0058] Additionally, a same voltage potential can preferably be
applied to the shield electrode 330 and 430 that is applied to the
touch electrodes 300. The voltage potential can be applied as a
series of pulses synchronized with the touch electrode drive signal
or as a fixed voltage. Because the shield electrode 330 and 430 is
at the same potential as the touch electrodes 300, no electric
field and, therefore, no parasitic capacitance is generated between
the shield electrode 330 and 430 and the touch electrodes 300.
However, a parasitic capacitance will exist between the shield
electrode 330 and 430 and the upper display electrode UDE.
Therefore, the shield electrode 330 and 430 is electrically
isolated from the touch electrodes 300 so that this parasitic
capacitance does not affect sensing of a touch by the touch sensor.
That is, although the shield electrode 330 and 430 and the touch
electrodes 300 are driven at the same potential, they are isolated
from one another such that there is no electrical connection
between the shield electrode 330 and 430 and the touch electrodes
300.
[0059] As discussed above, when a touch object comes within close
proximity to the touch electrode, the interaction of the projected
electric field from the touch electrode and the touch object causes
a change in charge held on the touch electrode and, therefore, a
change in its capacitance. Therefore, by detecting a change in
capacitance, the presence of a touching object can be determined.
Because the touch electrodes are patterned in a touch sensor array
on the display panel, depending on which touch electrode indicates
a change in capacitance, the location of the touch on the touch
sensor and display panel can be determined.
[0060] FIGS. 7A and 7B show a preferred embodiment of the present
invention. FIG. 7A shows a representation of touch sensor feedlines
710 (shaded areas) and a shield electrode 730 with respect to the
second pixel distribution layout. FIG. 7A shows a feedline region
of the touch sensor, showing four feedlines 710 routing vertically
in the figure. FIG. 7B shows a representation of a portion of a
touch electrode 740 and a shield electrode 730 in a touch electrode
region of the touch sensor. In the touch electrode region, the
conductive and opaque material of the shield electrode 730
preferably has the same pattern as the conductive and opaque
material in the touch electrode 740, so the shield electrode 730 is
not distinguishable from the touch electrode 740 in the plan view
of FIG. 7B. In the feedline region of FIG. 7A, the conductive and
opaque material of the shield electrode 730 has the same pattern as
the conductive and opaque material in the touch electrode and thus
the shield electrode 730 is not distinguishable under the feedlines
710 in FIG. 7A.
[0061] The average coverage of conductive and opaque material in
the touch sensor layer in the feedline region is lower than the
average coverage in the touch electrode region, owing to the gaps
which enable electrical isolation of adjacent feedlines. The region
over which the average coverage is determined is at least an area
of the display panel that includes a 2x2 array of sub-pixels.
Preferably, the feedlines 710 are patterned as shown in FIG. 7A
such that the total area of the feedlines 710 routed around the
sub-pixels 700 is reduced or minimized while maintaining a low
resistance electrical connection along its length. Reducing or
minimizing the area of the feedline 710 reduces the parasitic
capacitance and also the sensitivity to touch in the feedline 710
which reduces the false detection problem. Preferably, in touch
electrode regions, the conductive and opaque material is in between
every sub-pixel included in the touch electrode 740 as illustrated
in FIG. 7B.
[0062] In the feedline region like that of FIG. 7A, the shield
electrode 730 preferably has a similar pattern and average coverage
of conductive and opaque material as in the touch electrode region.
FIG. 7A shows that the shield electrode 730 is present underneath
the feedline 710 and continues where the feedline 710 is not
present. Therefore, the average coverage of the conductive and
opaque material in either touch electrode 740 or shield electrode
730 layer in a plan view projection is similar in both the touch
electrode region and feedline region. This provides uniform
reflection of ambient light and light output from the sub-pixels
across the display panel. This ensures that no undesirable patterns
are clearly visible between touch electrode and feedline regions
and that all areas of the display panel have similar viewing
characteristics. Preferably, the average coverage of conductive and
opaque material in either the touch sensor or shield electrode
layer in a plan view projection in feedline regions is between
about 50% and about 150% of the coverage in touch electrode
regions, and more preferably between about 80% and about 120%, to
provide acceptably low visibility of differences between the two
regions.
[0063] In a feedline region, the gap between adjacent feedlines 710
and the gap between feedlines 710 and adjacent touch electrodes
(not shown) may be as wide as up to the pitch between adjacent
sub-pixels, as shown in FIG. 7A, while maintaining the maximum
density of feedlines 710, where the pitch is the distance between
the center of a sub-pixel 700 and the center of an adjacent
sub-pixel 700. As a result of this large gap, the probability of
short circuiting from manufacturing defects in patterning extra
conductive material is reduced. This preferred embodiment of the
present invention can be applied to both the first pixel
distribution (e.g., FIG. 5) and second pixel distribution (e.g.,
FIG. 6) layouts.
[0064] FIG. 8 shows a preferred embodiment of the present invention
that includes a representation of a touch electrode 850, feedlines
810, and a shield electrode 830 with respect to the first pixel
distribution layout. FIG. 8 shows a touch electrode region TER and
a feedline region FR. The coverage of conductive and opaque
material in the touch sensor layer is similar to that discussed
above with respect to FIGS. 7A and 7B for a feedline region and a
touch electrode region. In this preferred embodiment, in the touch
electrode region TER, the shield electrode is the same width as the
touch electrode 850, thus is not seen. However, in the feedline
region FR, the shield electrode 830 is wider than the feedlines
810. FIG. 8 shows that the shield electrode 830 overlaps with the
feedlines 810 and extends out to be wider than the feedlines 810
without overlapping the sub-pixels 800. The increased width of the
shield electrode 830 further reduces the feedline parasitic
capacitance, and also reduces sensitivity to touch associated with
the feedline (i.e., it has the effect of reducing or eliminating
occurrences of a false touch detection). The increased width of the
shield electrode 830 reduces the parasitic capacitance by shielding
the fringing electric fields at the edges of the feedlines 810 and
also reduces the strength of the projected electric field and the
feedline sensitivity.
[0065] FIG. 9 shows a representative side view of a display device
900 comparing a shield electrode 930 having the same width as the
feedline 910 on the left side of the figure and a shield electrode
935 wider than the feedline 910 on the right side of the figure.
Remaining portions of the display device 900 are preferably similar
to those discussed with respect to FIG. 1 and are not described
again for the sake of brevity. FIG. 9 represents that the fringing
electric field 995 on the right side of the figure with the shield
electrode 935 wider than the feedline 910 in between sub-pixel
regions 950 is reduced as compared to the fringing electric field
990 on the left side of the figure.
[0066] In another preferred example for a feedline region, when the
shield electrode is wider than the feedline, the distribution of
conductive and opaque material in the shield layer may be adjusted
to provide an average coverage of conductive and opaque material in
either the touch sensor or the shield electrode layer in a plan
view projection which is similar to the average coverage in a touch
electrode region. With respect to FIG. 8, for example, the
conductive and opaque material of the shield electrode 830 in
between adjacent feedlines 810 is preferably configured so that the
average coverage of conductive and opaque material across the
display panel is uniform. Advantageously, the average area coverage
of conductive and opaque material in the touch electrode regions is
similar to or the same as the average area coverage of conductive
and opaque material in the feedline regions, even though there is
additional shielding of the feedlines 810. This preferred
embodiment of the present invention can be applied to both the
first pixel distribution (e.g., FIG. 5) and second pixel
distribution (e.g., FIG. 6) layouts.
[0067] FIG. 10A shows a preferred embodiment of the present
invention where an area of the shield electrode 1030 is increased
in regions where the touch electrode or feedline has an internal
corner or internal curved edge (hereafter referred to as a
"corner"). FIG. 10A shows the touch electrode 1090 and shield
electrode 1030 in a touch electrode region, but similarly this
feature may be applied to a feedline region. The purpose of this
preferred embodiment is to decrease the variation in electrical
properties (e.g., parasitic capacitance of a touch electrode or
feedline) from display device to display device caused by the
random error in alignment between the shield electrode 1030 and the
touch electrode or feedline during fabrication. Because the shield
electrode 1030 reduces the electric field between the touch
electrode or feedline and an upper display electrode UDE, the
effectiveness of the shield electrode 1030 in reducing parasitic
capacitance is determined by the area where the touch electrode or
feedline overlap the shield electrode. By increasing the area of
the shield electrode 1030 where the touch electrodes or feedlines
have internal corners, the change in the area of the touch
electrode or feedline overlapped by the shield electrode 1030 that
is caused by misalignment between the two layers is reduced.
[0068] FIG. 10A shows a representative portion of an OLED display
in which the conductive and opaque material of a touch electrode
1090 and the shield electrode 1030 surround sub-pixels 1000. For
clarity, FIG. 10B shows only the shield electrode 1030 and the
sub-pixels 1000, and FIG. 10C shows only the touch electrode 1090
and the sub-pixels 1000. The width .beta. 1035 of a line forming a
portion of the touch electrode 1090 and the underlying shield
electrode 1030 is shown in FIG. 10B and FIG. 10C. A width .alpha.
of a leg 1040 of a triangle representing an increase of the
conductive and opaque material of the shield electrode 1030 near
the internal corners of the touch electrode 1090 is shown in FIG.
10B. Accordingly, with the preferred embodiment of the present
invention shown in FIG. 10A, there is no misalignment between the
shield electrode 1030 and the touch electrode 1090.
[0069] FIG. 11 shows a representative portion of an OLED display in
which a shield electrode 1130 and the touch electrode 1190 are
provided. However, FIG. 11 shows an alignment error .gamma. between
the shield electrode 1130 and the touch electrode 1190.
[0070] Using the parameters described above, FIG. 12 shows a
calculated model of percentages of a touch electrode area
overlapped by the shield electrode plotted against a relative
percentage of only horizontal alignment error for a configuration
where the width of the touch electrode is the same as the width of
the shield electrode in between subpixels. The vertical dashed line
in FIG. 12 represents a location where the alignment error .gamma.
equals the width .beta. of the touch electrode and the shield
electrode lines. Several examples of preferred embodiments of the
present invention are plotted with varying relationships of the
length a of the leg 1040 of the corner regions to the width .beta.
of the touch electrode and the shield electrode lines. The plotted
dotted line represents a case where there is no increase in area of
the shield electrode near the internal corners of the touch
electrode and the solid lines represent cases where an increased
area of the shield electrode is provided.
[0071] From FIG. 12, it can be seen that increases in the shield
electrode area in internal angle corners caused by larger values of
the length a result in a smaller reduction in overlapped area as
the alignment area increases. In FIG. 10, adjacent to an internal
corner in the touch electrode or feedline, the shield electrode
1030 extends beyond the touch electrode or feedline with a
triangular shape. In another preferred embodiment, adjacent to an
internal corner of the touch electrode or feedline, the shield
electrode 1330 extends beyond the touch electrode to a curved edge
which is concave with respect to the adjacent sub-pixel 1300, as
shown in FIG. 13.
[0072] By increasing the shield electrode area in the internal
angle corners only, the optical performance of the display panel at
high viewing angles is still maintained. In particular, this shield
electrode structure reduces variation in parasitic capacitance
between devices due to misalignment between the shield and the
touch electrodes or feedlines without causing additional blocking
of light from the sub-pixel which propagates in a direction which
would otherwise be directly emitted from the display device. As is
apparent from FIG. 1A, the conductive opaque material of the shield
electrode SE, touch electrode or feedline of the touch sensor TS
may block light from the sub-pixel SUB-PIX which would otherwise be
directly emitted from the display if the horizontal separation
between the edge of the sub-pixel SUB-PIX and the opaque material
is below a particular value for a given vertical proximity VP
between the layers. Preferably for this, and all previous
embodiments, the shield electrode, touch electrode, and feedline
are between sub-pixels with sufficiently high separation from the
edge of the sub-pixel that no light which would otherwise be
directly emitted from the display is blocked, and therefore the
brightness of the emitted light for high polar viewing angles is
not reduced.
[0073] Referring again to the shield shapes in FIG. 10 and FIG. 13,
since the additional shield area is in the corners furthest from
the sub-pixel 1000, 1300, the distance between the edge of the
sub-pixel 1000, 1300 and the opaque material of any of the shield
electrode, touch electrode and feedline may still remain the same
as or larger than the separation discussed above at the center of
an edge of a sub-pixel 1000, 1300. Optionally, the sub-pixel can be
configured to have rounded corners, can be round, can be defined as
a multi-sided polygon, or can be provided in any other desirable
shape such that the minimum horizontal proximity of the sub-pixel
emissive regions to the shield electrode is not reduced even when
the shield electrode area is increased in the internal corners.
[0074] Although described here for internal corners, the additional
shield material may also be used around external corners of the
touch electrodes and feedlines. This is particularly advantageous
for feedlines because they may have a higher ratio of number of
external corners divided by number of internal corners than touch
electrodes.
[0075] Preferably for all previous embodiments, the conductive and
opaque material of the touch electrodes, feedlines and shield
electrode is distributed between sub-pixels with sufficiently high
separation from the edge of the sub-pixel, measured in the plane of
the display device, that no light which would otherwise be directly
emitted from the display device is blocked, and therefore the
brightness of the emitted light for high polar viewing angles is
not reduced. To achieve this, a suitable minimum separation between
the edge of the sub-pixel and the conductive and opaque material
provides a direction between the edge of the sub-pixel and the edge
of the conductive and opaque material which is at an angle relative
to the direction perpendicular to the plane of the display device
that is equal to the maximum escape angle for light emitted from
the sub-pixel.
[0076] It should be understood that the foregoing description is
only illustrative of preferred embodiments of the present
invention. Various alternatives and modifications can be devised by
those skilled in the art without departing from the present
invention. Accordingly, the present invention is intended to
embrace all such alternatives, modifications, and variances that
fall within the scope of the appended claims.
* * * * *