U.S. patent application number 10/228856 was filed with the patent office on 2003-01-09 for touch panel with improved optical performance.
Invention is credited to Blanchard, Randall D..
Application Number | 20030006971 10/228856 |
Document ID | / |
Family ID | 23437018 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030006971 |
Kind Code |
A1 |
Blanchard, Randall D. |
January 9, 2003 |
Touch panel with improved optical performance
Abstract
Sunlight can damage a conventional touch screen display and
cause the display to be quite difficult to read. Furthermore,
conventional touch screen displays are easily damaged, and, once
damaged, the entire touch screen is replaced. To address these
concerns, a touch panel includes anti-reflective coatings on the
surfaces of the top plate and the base plate that are open to the
air. These coatings substantially reduce reflections and make the
touch screen easier to read in direct sunlight. In particular, the
anti-reflective coating used on the upper surface of the base plate
is dielectric in nature to reduce reflectivity even further. This
dielectric coating includes openings to an underlying conductive
layer so that an electrical contact is made when a user deflects
the top plate into the base plate. Also, the top plate may be
detachably coupled to the base plate, advantageously by double
stick adhesive tape, so that only the top plate is replaced when
damaged. Furthermore, a resistive voltage divider may be fabricated
on the base plate. The resistive voltage divider may include a
substantially continuous strip of resistive material disposed on
the conductive layer of the base plate, and a plurality of
conductive traces disposed on the dielectric layer of the base
plate and coupled to the resistive material in selected
locations.
Inventors: |
Blanchard, Randall D.; (San
Diego, CA) |
Correspondence
Address: |
Michael G. Fletcher
Fletcher,Yoder & Van Someren
P.O. Box 692289
Houston
TX
77269-2289
US
|
Family ID: |
23437018 |
Appl. No.: |
10/228856 |
Filed: |
August 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10228856 |
Aug 27, 2002 |
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09364988 |
Jul 31, 1999 |
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Current U.S.
Class: |
345/173 |
Current CPC
Class: |
G06F 3/045 20130101;
G02B 1/116 20130101 |
Class at
Publication: |
345/173 |
International
Class: |
G09G 005/00 |
Claims
What is claimed is:
1. A touch panel display system comprising: a computer; a
controller coupled to the computer; a display screen coupled to the
computer; a touch panel coupled to the controller and being
disposed over the display screen, the touch panel comprising: a
base plate being disposed adjacent the display screen, the base
plate having a rigid substrate having an upper surface and a lower
surface, a first conductive layer disposed over the upper surface
of the rigid substrate, an anti-reflective dielectric layer
disposed over the first conductive layer, the anti-reflective
dielectric layer having openings through to the first conductive
layer, and a first anti-reflective layer disposed on the lower
surface of the rigid substrate; and a top plate being disposed in
spaced apart relation over the base plate, the top plate having a
flexible substrate having an upper surface and a lower surface, a
hard coating layer and a second anti-reflective layer disposed over
the upper surface of the flexible substrate, and an anti-reflective
conductive layer disposed on the lower surface of the flexible
substrate.
2. The system, as set forth in claim 1, wherein the display screen
comprises a liquid crystal display.
3. The system, as set forth in claim 1, wherein the top plate is
removably mounted in spaced apart relation over the base plate.
4. The system, as set forth in claim 3, comprising double stick
adhesive tape coupling the top plate to the base plate.
5. The system, as set forth in claim 4, wherein the double stick
adhesive tape comprises a relatively high tack adhesive side and a
relatively low tack adhesive side.
6. The system, as set forth in claim 5, wherein the relatively high
tack adhesive side is coupled to the top plate and the relatively
low tack adhesive side is coupled to the base plate.
7. The system, as set forth in claim 5, wherein the relatively high
tack adhesive side is coupled to the base plate and the relatively
low tack adhesive side is coupled to the top plate.
8. The system, as set forth in claim 1, wherein the second
anti-reflective layer is disposed over the hard coating layer.
9. The system, as set forth in claim 1, wherein the top plate
comprises an anti-fingerprint layer disposed over the second
anti-reflective layer and the hard coating layer.
10. The system, as set forth in claim 1, wherein the
anti-fingerprint layer comprises a hydrophobic material.
11. The system, as set forth in claim 1, wherein the rigid
substrate comprises glass.
12. The system, as set forth in claim 1, wherein the rigid
substrate comprises a first substrate portion bonded to a second
substrate portion.
13. The system, as set fort in claim 12, wherein the first
substrate portion and the second substrate portion comprise
glass.
14. The system, as set forth in claim 1, comprising a coating which
reflects solar energy outside the visible spectrum disposed on at
least one of the top plate and the base plate.
15. The system, as set forth in claim 14, wherein the coating which
reflects solar energy comprises a hot mirror capability.
16. The system, as set forth in claim 1, wherein the first
conductive layer comprises at least one of titanium and indium tin
oxide.
17. The system, as set forth in claim 1, wherein the
anti-reflective dielectric layer comprises at least one of silicon
dioxide and magnesium fluoride.
18. The system, as set forth in claim 1, wherein each opening has
an area in a range from about 2.5 mils to about 10.0 mils, and
wherein the openings have an average spacing in a range from about
10.0 mils to about 50.0 mils.
19. The system, as set forth in claim 1, wherein the first
anti-reflective layer comprises multiple layers.
20. The system, as set forth in claim 1, wherein the flexible
substrate comprises one of Mylar, Lexan, and CR-39.
21. The system, as set forth in claim 1, wherein the hard coating
layer comprises silicon dioxide.
22. The system, as set forth in claim 1, wherein the second
anti-reflective layer comprises at least one of silicon dioxide and
magnesium fluoride.
23. The system, as set forth in claim 1, wherein the
anti-reflective conductive layer comprises at least one of titanium
and indium tin oxide.
24. The system, as set forth in claim 1, wherein the touch panel
comprises a sensing circuit coupled to the first conductive layer
and to the anti-reflective conductive layer, the sensing circuit
delivering a signal correlative to a position where the first
conductive layer contacts the anti-reflective conductive layer.
25. The system, as set forth in claim 24, wherein the sensing
circuit comprises: a substantially continuous resistive member
disposed on the first conductive layer adjacent a peripheral
portion of the anti-reflective dielectric layer; and a plurality of
conductive traces disposed on the anti-reflective dielectric layer,
each of the plurality of conductive traces having a first end
coupled to a respective selected location of the resistive member
and having a second end coupled to the controller.
26. A touch screen overlay comprising: a flexible substrate having
an upper surface and a lower surface; and double stick adhesive
tape coupled to the lower surface of the flexible substrate.
27. The overlay, as set forth in claim 20, comprising a hard
coating layer disposed over the upper surface of the flexible
substrate.
28. The overlay, as set forth in claim 27, wherein the hard coating
layer comprises silicon dioxide.
29. The overlay, as set forth in claim 26, wherein the flexible
substrate comprises one of Mylar, Lexan, and CR-39.
30. The overlay, as set forth in claim 26, comprising an
anti-reflective layer disposed over the upper surface of the
flexible substrate.
31. The overlay, as set forth in claim 30, wherein the
anti-reflective layer comprises at least one of silicon dioxide and
magnesium fluoride.
32. The overlay, as set forth in claim 26, comprising an
anti-reflective conductive layer disposed on the lower surface of
the flexible substrate.
33. The overlay, as set forth in claim 32, wherein the
anti-reflective conductive layer comprises at least one of titanium
and indium tin oxide.
34. The overlay, as set forth in claim 26, wherein the double stick
adhesive tape comprises a relatively high tack adhesive side and a
relatively low tack adhesive side.
35. The overlay, as set forth in claim 34, wherein the relatively
high tack adhesive side is coupled to the flexible substrate.
36. The overlay, as set forth in claim 34, wherein the relatively
low tack adhesive side is coupled to the flexible substrate.
37. The overlay, as set forth in claim 26, comprising an
anti-fingerprint layer disposed over the flexible substrate.
38. The overlay, as set forth in claim 37, wherein the
anti-fingerprint layer comprises a hydrophobic material.
39. The overlay, as set forth in claim 26, comprising a coating
which reflects solar energy outside the visible spectrum disposed
over the flexible substrate.
40. The overlay, as set forth in claim 39, wherein the coating
which reflects solar energy outside the visible spectrum comprises
a hot mirror capability.
41. A touch screen comprising: a top plate having an upper surface
and a lower surface; a base plate having an upper surface and a
lower surface; and a member detachably coupling the lower surface
of the top plate to the upper surface of the base plate.
42. The touch screen, as set forth in claim 41, wherein the top
plate comprises a flexible substrate having an upper surface and a
lower surface.
43. The touch screen, as set forth in claim 42, wherein the
flexible substrate comprises one of Mylar, Lexan, and CR-39.
44. The touch screen, as set forth in claim 42, comprising a hard
coating layer disposed over the upper surface of the flexible
substrate.
45. The touch screen, as set forth in claim 44, wherein the hard
coating layer comprises silicon dioxide.
46. The touch screen, as set forth in claim 42, comprising an
anti-reflective layer disposed over the upper surface of the
flexible substrate.
47. The touch screen, as set forth in claim 46, wherein the
anti-reflective layer comprises at least one of silicon dioxide and
magnesium fluoride.
48. The touch screen, as set forth in claim 42, comprising an
anti-reflective conductive layer disposed on the lower surface of
the flexible substrate.
49. The touch screen, as set forth in claim 48, wherein the
anti-reflective conductive layer comprises at least one of titanium
and indium tin oxide.
50. The touch screen, as set forth in claim 41, wherein the member
comprises double stick adhesive tape.
51. The touch screen, as set forth in claim 50, wherein the double
stick adhesive tape comprises a relatively high tack adhesive side
and a relatively low tack adhesive side.
52. The touch screen, as set forth in claim 51, wherein the
relatively high tack adhesive side is coupled to the lower surface
of the top plate and the relatively low tack adhesive side is
coupled to the upper surface of the base plate.
53. The touch screen, as set forth in claim 51, wherein the
relatively low tack adhesive side is coupled to the lower surface
of the top plate and the relatively high tack adhesive side is
coupled to the upper surface of the base plate.
54. The touch screen, as set forth in claim 42, comprising an
anti-fingerprint layer disposed over the flexible substrate.
55. The touch screen, as set forth in claim 54, wherein the
anti-fingerprint layer comprises a hydrophobic material.
56. The touch screen, as set forth in claim 42, comprising a
coating which reflects solar energy outside the visible spectrum
disposed over the flexible substrate.
57. The touch screen, as set forth in claim 56, wherein the coating
which reflects solar energy outside the visible spectrum comprises
a hot mirror capability.
58. The touch screen, as set forth in claim 41, wherein the base
plate comprises a rigid substrate having an upper surface and a
lower surface.
59. The touch screen, as set forth in claim 58, comprising a
conductive layer disposed over the upper surface of the rigid
substrate.
60. The touch screen, as set forth in claim 59, wherein the
conductive layer comprises at least one of titanium and indium tin
oxide.
61. The touch screen, as set forth in claim 59, comprising an
anti-reflective dielectric layer disposed over the conductive
layer, the anti-reflective dielectric layer having openings through
to the conductive layer.
62. The touch screen, as set forth in claim 61, wherein the
anti-reflective dielectric layer comprises one of silicon dioxide
and magnesium fluoride.
63. The touch screen, as set forth in claim 58, comprising an
anti-reflective layer disposed on the lower surface of the rigid
substrate.
64. The touch screen, as set forth in claim 63, wherein the
anti-reflective layer comprises multiple layers of anti-reflective
material.
65. The touch screen, as set forth in claim 41, comprising a
sensing circuit coupled to the top plate and to the base plate, the
sensing circuit delivering a signal correlative to a position where
the top plate contacts the base plate.
66. The touch screen, as set forth in claim 65, wherein the sensing
circuit comprises: a substantially continuous resistive member
disposed on a conductive layer on the base plate adjacent a
peripheral portion of a patterned anti-reflective dielectric layer
disposed over the conductive layer on the base plate; and a
plurality of conductive traces disposed on the anti-reflective
dielectric layer, each of the plurality of conductive traces having
a first end coupled to a respective selected location of the
resistive member.
67. A method of repairing a damaged touch screen having a flexible
top plate disposed in spaced apart relation over a relatively rigid
base plate, the method comprising the acts of: (a) removing the top
plate from the base plate; and (b) disposing a replacement top
plate on the base plate.
68. The method, as set forth in claim 67, wherein act (a) comprises
the act of breaking an adhesive seal of adhesive tape holding the
top plate to the base plate.
69. A method of manufacturing a touch panel, the method comprising
the acts of: (a) providing a base plate; (b) providing a top plate;
and (c) detachably disposing the top plate over the base plate in
spaced apart relation.
70. A method of manufacturing a touch panel, the method comprising
the acts of: (a) disposing a layer of conductive material over an
upper surface of a relatively rigid substrate of a base plate; (b)
disposing a patterned layer of anti-reflective dielectric material
over the layer of conductive material, the patterned layer of
anti-reflective dielectric material having openings through to the
layer of conductive material; (c) disposing a first layer of
anti-reflective material over a lower surface of the relatively
rigid substrate of the base plate; (d) disposing a second layer of
anti-reflective material over an upper surface of a relatively
flexible substrate of a top plate; (e) disposing a layer of
anti-reflective conductive material over a lower surface of the
relatively flexible substrate of the top plate; and (f) arranging
the top plate over the base plate such that the anti-reflective
conductive material disposed over the lower surface of the top
plate is in spaced apart relation to the patterned anti-reflective
dielectric layer disposed over the upper surface of the base
plate.
71. A sensing unit for a touch panel comprising: a first plate
having a first layer of conductive material disposed on its
surface; a second plate having a second layer of conductive
material disposed on its surface and having a layer of dielectric
material disposed over the second layer of conductive material such
that a peripheral portion of the second layer of conductive
material remains exposed, the layer of dielectric material having
openings through to the second layer of conductive material; a
substantially continuous resistive member disposed over the exposed
peripheral portion of the second layer of conductive material
adjacent a periphery of the layer of dielectric material; and a
plurality of conductive traces disposed on the layer of dielectric
material, each of the plurality of conductive traces having a first
end coupled to a respective selected location of the resistive
member.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to input devices
and, more particularly, to improvements for touch panel
displays.
[0003] 2. Background of the Related Art
[0004] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
present invention which are described and/or claimed below. This
discussion is believed to be helpful in providing the reader with
background information to facilitate a better understanding of the
various aspects of the present invention. Accordingly, it should be
understood that these statements are to be read in this light, and
not as admissions of prior art.
[0005] Input devices perform the function of providing some means
for entering commands and data into a computer, data processor, or
information system. A variety of input devices are currently
available, including keyboards, light pens, data tablets, mice,
track balls, joysticks, scanners, voice recognition devices, and
touch screens. Each of these input devices exhibits various
advantages and disadvantages, and the input device or devices used
in any particular application are typically chosen to maximize the
efficient input of information into the system.
[0006] This disclosure is primarily directed to the last of the
input devices mentioned above, namely touch screens. Unlike the
other input devices mentioned above, touch screens not only act as
a data input device, they also act as a display unit. Essentially,
a touch screen is a display unit with some form of a
touch-sensitive surface. Due to this unique characteristic, touch
screens are currently utilized in a variety of different
applications, such as computer terminals, cash registers, automatic
teller machines, and automated gasoline pumps to name just a
few.
[0007] Currently, there are at least four different technologies
used for touch screens: (1) capacitive, (2) resistive, (3) surface
acoustic wave, and (4) light beam interruption. Although each of
these different types of touch screens operate in a different
manner and exhibit certain advantages and disadvantages, certain
similarities exist. For example, regardless of the type of touch
screen, the touch screen system typically includes a sensor unit,
which senses the location touched on the display, and a controller
unit, which interfaces with the sensor unit and communicates the
location information to a system computer. Thus, regardless of the
technology employed, each type of touch screen performs the same
general function.
[0008] However, it is the differences in the way that the various
types of touch screens operate that causes a designer to use one
type of touch screen over another for a particular application.
Resistive touch screens, for example, advantageously exhibit low
cost, high touch point density, and can be operated with a gloved
hand. Disadvantageously, however, resistive touch screens can be
easily damaged and exhibit poor display characteristics
(particularly in sunlight). Capacitive touch screens also provide
high touch point density and low cost, but capacitive touch screens
can be easily damaged, must be calibrated due to large temperature
changes, and cannot be operated with a gloved hand.
[0009] In contrast, surface acoustic wave touch screens have no
overlay to be damaged or to reduce the visual quality of the
display. However, surface acoustic wave touch screens typically
exhibit the highest cost and can be falsely triggered by noise,
wind, transmission signals, and insects. Touch screens that use
light beam interruption, typically called infrared touch screens,
are relatively expensive. Advantageously however, they have no
touch sensitive overlay to be damaged, exhibit high touch point
density, can be operated with heavy gloves, exhibit good immunity
to most false trigger sources, and are extremely rugged and weather
sealable. Although these advantages typically make infrared touch
screens the most suitable type of touch screen to use in outdoor
applications, high ambient light conditions, such as direct
sunlight, can cause an infrared touch screen to malfunction.
[0010] It can be seen that each type of touch screen exhibits some
disadvantage which makes it not well suited for outdoor use,
particularly in high ambient light conditions. Of the different
types of touch screens mentioned above, resistive touch screens
typically offer the lowest cost along with very good operational
performance. In a resistive touch screen, a display, such as a
liquid crystal display, resides beneath a multi-layered screen
overlay. The top layer touched by a user is a plastic layer with a
transparent metallic film on its underside. This top layer is
separated by insulating spacers from a bottom layer that has a
metallic film on its upper side. These metallic films face one
another so that the films make contact when a user presses the top
layer into contact with the bottom layer. A conductive path is
formed at the point of contact. Thus, the films act as a voltage
divider, and the voltage at the point of contact may be measured in
the X and Y directions by applying the voltage in one direction and
then the other direction. The measured voltages may then be sent to
a controller where they are converted into coordinates on the
screen and sent to a computer.
[0011] This overlay screen suffers in outdoor applications, and
particularly in sunlight, for various reasons. First, the typical
reflectance of such overlay screens is about 25%, making the
underlying display difficult to read. Second, such overlay screens
allow most of the infrared radiation from sunlight to be absorbed
by the underlying liquid crystal display, and this radiation can
cause solar thermal loading of the display which lead to display
malfunction. Third, the materials used for such overlay screens
tend to deteriorate rapidly from exposure to the ultraviolet rays
of the sun. Fourth, the top layer touched by users is easily
scratched or damaged, thus requiring the whole touch panel to be
replaced.
[0012] The present invention may address one or more of the
problems set forth above.
SUMMARY OF THE INVENTION
[0013] Certain aspects commensurate in scope with the originally
claimed invention are set forth below. It should be understood that
these aspects are presented merely to provide the reader with a
brief summary of certain forms the invention might take and that
these aspects are not intended to limit the scope of the invention.
Indeed, the invention may encompass a variety of aspects that may
not be set forth below.
[0014] In accordance with one aspect of the present invention,
there is provided a touch panel display system that includes a
computer, a controller coupled to the computer, and a display
screen coupled to the computer. A touch panel is coupled to the
controller and disposed over the display screen. The touch panel
includes a base plate being disposed adjacent the display screen.
The base plate has a rigid substrate having an upper surface and a
lower surface. A first conductive layer is disposed over the upper
surface of the rigid substrate. An anti-reflective dielectric layer
is disposed over the first conductive layer, and the
anti-reflective dielectric layer has openings through to the first
conductive layer. A first anti-reflective layer is disposed on the
lower surface of the rigid substrate. A top plate is disposed in
spaced apart relation over the base plate. The top plate has a
flexible substrate having an upper surface and a lower surface. A
hard coating layer and a second anti-reflective layer are disposed
over the upper surface of the flexible substrate, and an
anti-reflective conductive layer is disposed on the lower surface
of the flexible substrate.
[0015] In accordance with another aspect of the present invention,
there is provided a touch screen overlay that includes a flexible
substrate having an upper surface and a lower surface. Double stick
adhesive tape is coupled to the lower surface of the flexible
substrate.
[0016] In accordance with still another aspect of the present
invention, there is provided a touch screen that includes a top
plate having an upper surface and a lower surface and a base plate
having an upper surface and a lower surface. A member detachably
couples the lower surface of the top plate to the upper surface of
the base plate.
[0017] In accordance with yet another aspect of the present
invention, there is provided a method of repairing a damaged touch
screen having a flexible top plate disposed in spaced apart
relation over a relatively rigid base plate. The method includes
the acts of: (a) removing the top plate from the base plate; and
(b) disposing a replacement top plate on the base plate.
[0018] In accordance with a further aspect of the present
invention, there is provided a method of manufacturing a touch
panel. The method includes the acts of: (a) providing a base plate;
(b) providing a top plate; and (c) detachably disposing the top
plate over the base plate in spaced apart relation.
[0019] In accordance with a still further aspect of the present
invention, there is provided a method of manufacturing a touch
panel. The method includes the acts of: (a) disposing a layer of
conductive material over an upper surface of a relatively rigid
substrate of a base plate; (b) disposing a patterned layer of
anti-reflective dielectric material over the layer of conductive
material, the patterned layer of anti-reflective dielectric
material having openings through to the layer of conductive
material; (c) disposing a first layer of anti-reflective material
over a lower surface of the relatively rigid substrate of the base
plate; (d) disposing a second layer of anti-reflective material
over an upper surface of a relatively flexible substrate of a top
plate; (e) disposing a layer of anti-reflective conductive material
over a lower surface of the relatively flexible substrate of the
top plate; and (f) arranging the top plate over the base plate such
that the anti-reflective conductive material disposed over the
lower surface of the top plate is in spaced apart relation to the
patterned anti-reflective dielectric layer disposed over the upper
surface of the base plate.
[0020] In accordance with a yet further aspect of the present
invention, there is provided a sensing unit for a touch panel. A
first plate of the touch panel has a first layer of conductive
material disposed on its surface. A second plate of the touch panel
has a second layer of conductive material disposed on its surface
and has a layer of dielectric material disposed over the second
layer of conductive material such that a peripheral portion of the
second layer of conductive material remains exposed. The layer of
dielectric material has openings through to the second layer of
conductive material. -A substantially continuous resistive member
is disposed over the exposed peripheral portion of the second layer
of conductive material adjacent a periphery of the layer of
dielectric material. A plurality of conductive traces is disposed
on the layer of dielectric material, where each of the plurality of
conductive traces has a first end coupled to a respective selected
location of the resistive member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The foregoing and other advantages of the invention will
become apparent upon reading the following detailed description and
upon reference to the drawings in which:
[0022] FIG. 1 illustrates a simplified schematic diagram of a
display system;
[0023] FIG. 2 illustrates a cross-sectional view of a touch screen
display in accordance with the present invention;
[0024] FIG. 3 illustrates a partial exploded view of the touch
screen display illustrated in FIG. 2;
[0025] FIG. 4 illustrates a base plate having a resistive voltage
divider circuit in accordance with the present invention;
[0026] FIG. 5 illustrates a partial exploded view of the touch
screen display illustrated in FIG. 2 showing a detailed view of the
substrate of the base plate; and
[0027] FIG. 6 illustrates a portion of the anti-reflective
dielectric layer of the base plate illustrated in FIG. 4.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0028] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, not all features of an actual
implementation are described in the specification. It should be
appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0029] Turning now to the drawings, and referring initially to FIG.
1, a touch screen display system is illustrated and generally
designated by a reference numeral 10. The touch screen display
system 10 includes a touch screen and display assembly 12. The
touch screen is mounted in front of the display, such as a liquid
crystal display or a cathode ray tube, so that information on the
display may be read through the touch screen. Advantageously, a
face plate 13 is coupled to the assembly 12 in a manner which seals
and protects the assembly 12 from damage, such as damage caused by
impacts or weather. It should also be noted that the face plate 13
defines the periphery of an opening in which the assembly 12
resides that allows a user to contact the touch panel overlying the
display.
[0030] A controller 14 is electrically coupled to the touch screen
of the assembly 12. The controller 14 may be mounted on the
assembly 12, or it may be mounted in a separate location. When a
user inputs data into the system 10 by touching a portion of the
touch screen overlying selected indicia on the display, the
controller 14 receives information from the touch screen related to
the user inputs and converts this information to coordinate data.
The coordinate data is delivered to a computer 16 that is
electrically coupled to the controller 14. The computer 16 is also
electrically coupled to the display of the assembly 12 and,
typically, to an associated system 18 that the system 10 controls.
The computer 16 determines which displayed indicia corresponds to
the coordinate data, and it controls the display and the associated
system 18 accordingly.
[0031] As discussed previously, resistive touch panels have been
historically disadvantaged because they can be easily damaged and
because they exhibit poor display characteristics, particularly in
high ambient light conditions. Also, once a typical touch panel is
damaged, the entire touch panel usually must be replaced. These
problems and others are addressed by the touch panel and display
assembly illustrated in FIGS. 2 and 3, which includes a touch panel
20 and a display screen 22.
[0032] The touch panel 20 includes a top plate 24 and a base plate
26. As illustrated in FIG. 2, the touch panel 20 may be situated
relative to the display screen 22 such that an air gap 27 exists
between the base plate 26 and the display screen 22. This
arrangement facilitates the cooling of the display screen 22 as air
may circulate about it.
[0033] The primary structural component of the top plate 24 is a
substrate 28. The substrate 28 is advantageously selected to be a
durable, flexible, and transparent material, since it is intended
for use as a deflecting element which moves into contact with the
base plate 26 when pushed by a user. Suitable materials may include
Mylar, Lexan, and CR-39, for example. The thickness of the
substrate 28 should advantageously allow deflection into the base
plate 26 with light finger pressure, while not becoming wavy at
high temperature. Advantageously, it should also be stiff enough so
as not to make contact with the base plate 26 unless pressed. The
thickness of the substrate 28 may be in the range from about 5 to
about 20 mils, for example.
[0034] To enhance the damage resistance of the top plate 24, the
substrate 28 is coated with a hard transparent coating 30. Although
the individual needs of particular applications may be taken into
account when selecting the material for the hard coating 30, the
material should advantageously be one that will wear well when
subjected to the abuse of the general public. Such abuse may not
only include general wear and tear from normal operation of the
touch panel 20, but may also include vandalistic abuse such as
being struck with rocks, poked with sticks, cut by knives, or
burned by lighters. While it is unlikely that any material would
adequately protect the top plate 24 from all such abuses, it is
generally advisable that the hard coating 30 be selected from the
most durable material that falls within the technical and financial
constraints of a particular application. Suitable materials may
include, for instance, silicon dioxide.
[0035] The optical qualities of the top plate 24 are enhanced by
the use of one or more anti-reflective coatings 32 which may be
placed over and/or under the hard coating 30. An anti-reflective
coating is advantageously index matched to the substrate 28 to
provide low levels of reflectivity, advantageously in the range of
0.25 to 1.00%. In addition to enhancing the reflection properties
of the top plate 24, the coatings 32 also advantageously include a
"hot mirror" capability to reflect solar energy outside the visible
spectrum, i.e., infrared and ultraviolet light, to protect the
underlying elements of the touch screen 20 and the display 22 from
damage. Suitable anti-reflective materials may include silicon
dioxide or magnesium fluoride.
[0036] To improve the optical characteristics of the top plate 24
further, an anti-fingerprint coating 34 may be applied as the outer
surface of the top plate 24. The anti-fingerprint coating 34 may be
a commercially available coating that is resistant to dirt and
oils, i.e., hydrophobic, so that fingers and dirty gloves will not
smudge the top plate 24.
[0037] The underside of the substrate 28 is spaced from the upper
surface of the base plate 26 by an air gap 38. This surface of the
substrate 28 is coated with an anti-reflective conductive material
36. As described below in greater detail, it is the conductive
material 36 which makes contact with a conductive layer on the base
plate 26 when a user presses the top plate 24 and deflects it
across the air gap 38. The anti-reflective nature of the conductive
material 36 further improves the optical qualities of the top plate
24, and the conductive layer 36 is advantageously indexed matched
to the substrate 28 to reduce reflection. The conductive layer 36
may be made of titanium or indium tin oxide (ITO), for example.
[0038] The top plate 24 may be fixed to the base plate 26 in a
spaced apart relationship in a conventional manner. However, in
this embodiment, the top plate 24 is advantageously spaced from the
base plate 26 in a manner than allows the top plate 24 to be
removed from the base plate 26 so that the top plate 24 may be
separately replaced if damaged.
[0039] One particularly cost effective arrangement is the use of a
strip of double stick adhesive tape 40 that is applied about a
peripheral portion of the touch panel between the top plate 24 and
the base plate 26, as best illustrated in FIG. 3. An advantageous
type of double stick adhesive tape 40 is a high tack/low tack
Scotch brand adhesive tape available from 3M. This tape features a
carrier having a strong adhesive on one side and a repositionable
adhesive on the other side. Because the adhesive properties of such
tape may degrade with repeated use, it may be desirable to place
the high tack side of the adhesive tape 40 on the top plate 24. In
this situation, the tape 40 is retained on the top plate 24 when a
damaged top plate is removed, and a new piece of tape will be
affixed to the replacement top plate. However, as described below,
a resistive voltage divider circuit may be fabricated on a
peripheral portion of the base plate 26. Thus, it may be desirable
to provide additional protection for this circuit by placing the
high tack side of the adhesive tape 40 on the base plate 26 to
cover this circuit so that the tape 40 remains on the base plate 26
when a damaged top plate 24 is removed and replaced.
[0040] Although not specifically illustrated, other techniques may
also be used to mount the top plate 24 in a removable fashion over
the base plate 26. For instance, spacers may be provided between
the top plate 24 and the base plate 26, and the top plate 24 may be
bolted to the base plate 26. As another alternative, spacers and/or
spacer dots may be provided between the top plate 24 and the base
plate 26, and a removable bezel arrangement, or the like, may be
used to clamp or similarly hold the top plate 24 to the base plate
26.
[0041] Referring to FIGS. 3 and 4, the primary structural component
of the base plate 26 is a transparent substrate 42. The substrate
42 is advantageously selected to be relatively rigid compared to
the relatively flexible substrate 28 of the top plate 24, since it
is intended to limit deflection of the top plate 24 in order to
provide an accurate indication of the location on the screen
selected by the user. Suitable materials may include glass or
acrylic, for example. To enhance the optical properties of the
substrate 42, an anti-reflective coating 43, such as a multilayer
coating, is disposed on the lower surface of the substrate 42. A
broadband visible anti-reflective coating is typically
advantageous.
[0042] As illustrated in FIG. 5, the substrate 42 may be fabricated
from multiple layers. In this illustration, the substrate 42
includes a first glass portion 42A and a second glass portion 42B
coupled together by a sheet adhesive 42C. The second glass portion
42B provides extra support for the touch panel 20 and essentially
functions as a "vandal" glass to reduce the likelihood that severe
impacts will break the touch panel 20.
[0043] A layer of conductive material 44 is disposed on the upper
surface of the substrate 42. When a user presses the top plate 24,
the conductive material 36 on the underside of the top plate 24
should contact the conductive material 44 on the upper side of the
base plate 26. As discussed more fully below, it is the contact
between these two layers of conductive material 36 and 44 that
completes the resistive voltage divider circuit used to determine
the position on the touch screen 20 pressed by the user. However,
it is also desirable to reduce the reflection of the base plate 26
as much as possible. While an anti-reflective conductive material,
such as the anti-reflective conductive material 36, would improve
the optical qualities of the base plate 26, reflection would still
be about 8%. Other anti-reflective coatings, such as silicon
dioxide or magnesium fluoride, can reduce reflection to about 0.6%,
but these coatings are dielectric in nature. As such, the use of
these coatings over the layer of conductive material 44 would
normally prevent electrical contact between the top plate 24 and
the base plate 26.
[0044] To address this concern, a patterned anti-reflective
dielectric layer 46 is disposed over the conductive material 44. As
best illustrated by the enlarged view of the patterned
anti-reflective dielectric layer 46 depicted in FIG. 6, a plurality
of small circular holes 48 is formed in a regular pattern in the
layer 46, although other types of holes and patterns may also be
suitable. These holes 48 extend through the dielectric layer 46 to
expose the underlying conductive layer 44. Thus, when the top plate
24 is pressed by a user, the conductive layer 36 moves into contact
with the conductive layer 44 through at least one of the plurality
of holes 48 to complete the electrical circuit.
[0045] The holes 48 advantageously are between about 2.5 mil and
about 10.0 mil in diameter, and have an average spacing between
about 10.0 mil and about 50.0 mil. Values may be selected so that
between about 1.0% and about 5.0% of the surface of the underlying
conductive layer 44 is exposed. In one particularly advantageous
embodiment, the holes 48 have a diameter of about 3.0 mils and an
average spacing of about 20.0 mils, so that about 1.75% of the
underlying conductive layer 44 is exposed as very small dots. In
this embodiment, the dot array combined with the low reflectivity
properties of the dielectric material used in the layer 46 yields
an average reflectivity of about 1%.
[0046] The patterned anti-reflective dielectric layer 46 may be
formed in any suitable manner. For example, a dielectric material,
such as silicon dioxide, may be deposited in a layer over the
conductive layer 44. Then, using photoresist patterning and etching
techniques, the holes 48 may be patterned and etched.
Alternatively, a photoresist process may be used to deposit a
dielectric material, such as magnesium fluoride, onto the
conductive layer 44 in its patterned form.
[0047] It should be understood that spacer dots (not shown), which
are small insulative protrustions often used to separate opposing
conductive surfaces between a top plate and base plate of a touch
screen, may be used in the touch screen 20. However, as an
additional advantage, the use of a mostly insulated upper surface
of the base plate 26 may reduce or eliminate the usage of spacer
dots. The reduction or elimination of spacer dots serves two useful
ends. First, the cost should be reduced since the spacer dots are
not manufactured. Second, spacer dots tend to reflect light passing
through a touch screen, so the reduction or elimination of the
spacer dots correspondingly reduces or eliminates this reflected
light which adversely affects the optical qualities of a touch
screen.
[0048] The use of the dielectric layer 46 may also facilitate the
incorporation of other improvements into the touch screen 20. For
example, as illustrated in FIGS. 3 and 4, a resistive voltage
divider circuit 50 may be fabricated about a peripheral portion of
the base plate 26. Conventionally, a discrete voltage divider is
implemented about the edges of the upper conductive layer of the
base plate using a small segment of the sheet resistance of the
conductive surface. Disadvantageously, however, such a construction
provides a number of fixed voltages, so linearity is adversely
affected. To address this concern, the resistive voltage divider
circuit 50 includes a thick film resistive trace 52. The trace 52
is disposed on the conductive layer 44 and extends substantially
continuously about the outer periphery of the dielectric layer 46.
Also, to improve linearity further, the trace 52 may be tapered
toward the corners to increase resistance gradually along each of
the sides of the trace 52. It should be noted that the layer 46 and
the trace 52 are illustrated with diagonal lines for contrast
only--no crosshatching or diagonal lines are actually present on
these elements.
[0049] Four conductive traces 54A, 54B, 54C, and 54D are disposed
along a peripheral portion 56 of the dielectric layer 46.
Advantageously, this peripheral portion 56 of the dielectric layer
46 contains no holes 48 and, thus, insulates the conductive traces
54A-54D from the conductive layer 44. One end of each of the
conductive traces 54A, 54B, 54C, and 54D is coupled to a respective
corner 58A, 58B, 58C, and 58D of the resistive trace 52. The other
end of each of the conductive traces 54A, 54B, 54C, and 54D is
coupled to a respective conductive termination pad 60A, 60B, 60C,
and 60D located on one side of the peripheral portion 56 of the
dielectric layer 46.
[0050] A conductive voltage divider trace 62 is also located on
this side of the peripheral portion 56 of the dielectric layer 46.
One end of the voltage divider trace 62 is coupled to a small
conductive termination pad 64 disposed amongst the termination pads
60A, 60B, 60C, and 60D, and the other end of the voltage divider
trace 62 is coupled to a larger conductive termination pad 66. As
best illustrated in FIG. 3, the conductors of an interface cable 68
may be coupled to the pads 60A, 60B, 60C, 60D, 64, and 66 to
provide appropriate electrical signals to the controller 14.
[0051] The traces and termination pads mentioned above may be
fabricated in any suitable manner. For example, these traces and
pads may be fabricated from films deposited by a silk screening
technique or the like. Alternatively, photoresist patterning and
etching techniques may by used to form these traces and pads.
[0052] In view of the specific embodiments disclosed and discussed
above, it should be appreciated that the touch panel 20
incorporates several advantageous features that may be useful
individually or in combination. As to one advantage, the touch
panel 20 exhibits excellent optical properties due to the
arrangement of anti-reflective layers on the four surfaces of the
touch panel 20 that are adjacent the air. As to another advantage,
the top plate 24 of the touch panel 20 may be removed when damaged
and replaced without replacing any of the other elements of the
system 10. Yet another advantage stems from the use of the
patterned anti-reflective dielectric layer 46 on the base plate 26
to improve optical properties while still facilitating electrical
contact between the top plate 24 and the base plate 26. The use of
this layer 46 may further improve the optical properties of the
touch panel 20 due to the reduction or elimination of spacer dots.
Of course, the touch panel 20 also includes the resistive voltage
divider circuit 50 which improves the linearity of the voltage
sensing function of the touch panel 20 and, thus, improves the
touch point density and accuracy.
[0053] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and have been described in
detail herein. However, it should be understood that the invention
is not intended to be limited to the particular forms disclosed.
Rather, the invention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the following appended claims.
* * * * *