U.S. patent application number 10/778431 was filed with the patent office on 2004-08-19 for touch screen panel with integral wiring traces.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Bottari, Frank J., LaCourse, Michele L., Marble, Andrea C..
Application Number | 20040160424 10/778431 |
Document ID | / |
Family ID | 22658347 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040160424 |
Kind Code |
A1 |
Bottari, Frank J. ; et
al. |
August 19, 2004 |
Touch screen panel with integral wiring traces
Abstract
A method of manufacturing a touch panel wherein a glass
substrate is coated with a resistive layer; a pattern of conductive
edge electrodes and a conductive wire trace pattern are applied to
the resistive layer; the conductive edge electrodes are
electrically isolated from the conductive wire traces; and a
protective insulative border layer is applied over the edge
electrodes and the wire traces. A touch panel which includes a
glass substrate coated with a resistive layer on one surface
thereof; a pattern of edge electrodes on the resistive layer; a
wire trace pattern on the resistive layer; a trench in the
resistive layer between the wire trace pattern and the edge
electrode pattern; and a protective insulative border layer over
the edge electrode pattern and the wire traces.
Inventors: |
Bottari, Frank J.; (Acton,
MA) ; Marble, Andrea C.; (Lowell, MA) ;
LaCourse, Michele L.; (Pepperell, MA) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
22658347 |
Appl. No.: |
10/778431 |
Filed: |
February 16, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10778431 |
Feb 16, 2004 |
|
|
|
09773979 |
Feb 1, 2001 |
|
|
|
6727895 |
|
|
|
|
60179874 |
Feb 2, 2000 |
|
|
|
Current U.S.
Class: |
345/173 |
Current CPC
Class: |
Y10T 29/49128 20150115;
Y10T 29/49155 20150115; G06F 3/045 20130101; Y10T 428/24917
20150115; Y10T 428/24926 20150115 |
Class at
Publication: |
345/173 |
International
Class: |
G09G 005/00 |
Claims
What is claimed is:
1. A method of manufacturing a touch panel, the method comprising:
coating an insulative substrate with a resistive layer; applying a
pattern of conductive edge electrodes to the resistive layer and
applying a conductive wire trace pattern to the resistive layer;
electrically isolating the conductive edge electrodes from the
conductive wire traces; and applying an insulative material at
least between the edge electrodes and the wire traces.
2. The method of claim 1 in which the conductive layer is a tin
antimony oxide composition.
3. The method of claim 1 in which the insulative substrate is
glass.
4. The method of claim 1 in which the step of applying the pattern
of conductive edge electrodes and the wire trace pattern includes
screen printing silver/frit paste on the resistive layer in the
form of the edge electrode pattern and the wire trace pattern.
5. The method of claim 1 in which the step of electrically
isolating includes using a laser beam to ablate the resistive
material between the edge electrodes and the wire traces and the
resistive material between the wire traces.
6. The method of claim 1 in which the step of applying an
insulative material includes applying a protective insulative
border layer over the edge electrodes and the wire traces by screen
printing an insulative composition over the edge electrodes and the
wire traces.
7. The method of claim 6 in which the insulative composition is a
lead borosilicate glass composition.
8. The method of claim 1 further including the step of firing the
applied edge electrodes, the wire traces, and the insulative border
layer.
9. The method of claim 8 in which firing includes subjecting the
panel to an elevated temperature in a first period of time to burn
off any organic material and then a dwell period at the elevated
temperature to cure the elect odes and wire trace materials and to
fuse the insulative border layer material.
10. The method of claim 9 in which the elevated temperature is
between 500.degree. C.-525.degree. C., the first time period is
approximately 5 minutes, and the dwell period is approximately 2-3
minutes.
11. A touch panel comprising: a substrate coated with a resistive
layer on one surface thereof; a pattern of edge electrodes on the
resistive layer; a wire trace pattern on the resistive layer; and a
trench in the resistive layer between the wire trace pattern and
the edge electrode pattern to electrically isolate the wire trace
pattern from the edge electrode pattern.
12. The touch panel of claim 11 in which the resistive layer is a
tin antimony oxide composition.
13. The touch panel of claim 11 in which the substrate is a
glass.
14. The touch panel of claim 11 in which the pattern of edge
electrodes is made of a silver/frit paste composition.
15. The touch panel of claim 11 in which the wire trace pattern is
formed from a silver/frit paste composition.
16. The touch panel of claim 11 further including a protective
insulative border layer over the edge electrode pattern and the
wire traces.
17. The touch panel of claim 16 in which the protective insulative
border layer is formed from a lead borosilicate glass
composition.
18. A method of manufacturing a touch panel, the method comprising:
coating an insulative substrate with a resistive layer; apply a
pattern of conductive edge electrodes to the resistive layer and
applying a conductive wire trace pattern to the resistive layer;
removing the resistive layer at least between the wire traces and
the edge electrodes to electrically isolate them from each other;
applying an insulative material over both the wire traces and the
edge electrodes to protect them; and co-firing the edge electrodes,
the wire traces, and the insulative material all at the same time.
Description
RELATED APPLICATIONS
[0001] This application is related to application Ser. No.
09/169,391 filed Oct. 9, 1998 entitled TOUCH PANEL WITH IMPROVED
LINEAR RESPONSE AND MINIMAL BORDER WIDTH ELECTRODE PATTERN.
FIELD OF THE INVENTION
[0002] This invention relates to a touch screen panel with integral
wiring traces which eliminates the bulky and unreliable prior art
external wiring associated with touch screen panels and lowers the
cost of manufacturing touch screen panel assemblies.
BACKGROUND OF THE INVENTION
[0003] Touch screen panels generally comprise an insulative (e.g.,
glass) substrate and a resistive layer disposed on the insulative
substrate. A pattern of conductive edge electrodes are then formed
on the edges of the resistive layer. The conductive electrodes form
orthogonal electric fields in the X and Y directions across the
resistive layer. Contact of a finger or stylus on the active area
of the panel then causes the generation of a signal that is
representative of the X and Y coordinates of the location of the
finger or stylus with respect to the substrate. In this way, the
associated touch panel circuitry connected to the touch panel by
wiring traces can ascertain where the touch occurred on the
substrate.
[0004] Typically, a computer program generates an option to the
user (e.g. "press here for `yes` and press here for `no`") on a
monitor underneath the touch screen panel and the conductive
electrode pattern assists in detecting which option was chosen when
the touch screen panel was touched by the user.
[0005] The application referred to above relates to an improved
edge electrode pattern on the resistive layer of the touch screen
panel. The instant application relates to an improvement in the
prior art wiring harnesses attached to the touch screen.
[0006] There are typically four insulated individual wires, each
extending along and around the edges of the touch screen panel to
each corner of the touch screen panel where the insulation is
removed and the wire is hand soldered to a terminal electrode on
the panel at each corner of the panel.
[0007] One or more additional layers, usually tape, are often used
to secure the wires to the edges of the panel and there may be an
insulative layer between the wires and the edge electrodes of the
panel to electrically isolate the wires from the edge
electrodes.
[0008] The problem with such prior art devices are numerous. The
solder joints are often not very reliable and create solder bumps
on the smooth surface. Moreover, the act of soldering the ends of
each wire to the corner electrodes can damage the electrodes or
even crack the substrate of the touch panel. Also, this assembly
process is labor intensive and hence costly.
[0009] To reduce noise, a noise shield may be place under the
wires. Adequate noise protection, however, may not always be
possible. Also, the assembled touch screen panel does not have a
finished appearance. Instead, the taped on wires are bulky and
readily noticeable and detract from the appearance of the touch
screen panel.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of this invention to provide a
touch screen panel with integral wiring traces.
[0011] It is a further object of this invention to provide a touch
screen panel with integral wiring traces which is more reliable
than prior art touch screen panel assemblies.
[0012] It is a further object of this invention to provide a touch
screen panel which has a more finished, neat, and low profile
appearance.
[0013] It is a further object of this invention to provide a method
of manufacturing a touch screen panel with integral wiring
traces.
[0014] It is a further object of this invention to provide such a
method of manufacturing a touch screen panel with integral wiring
traces which eliminates the possibility of damaging the corner
electrodes of the touch screen panel and which eliminates the
possibility of damaging the touch screen substrate.
[0015] It is a further object of this invention to provide such a
method of manufacturing a touch screen panel with integral wiring
traces which is less labor intensive and less costly than prior art
methods.
[0016] It is a further object of this invention to provide a touch
screen panel with integral wiring traces and a protective coating
over both the wire trace pattern and the edge electrode
pattern.
[0017] It is a further object of this invention to provide a method
of manufacturing such a touch screen panel in which the conductive
silver paste of the edge electrode pattern and the wire trace
pattern is co-fired with the protective coating thereby resulting
in a cost and time savings.
[0018] This invention results from the realization that a more
reliable, less labor intensive, less costly, and more aesthetically
pleasing low profile touch screen panel assembly can be effected by
integral wiring traces wherein the prior art individual wires are
replaced with a wire trace pattern deposited on the resistive layer
of the touch screen panel right on the panel either by printing or
by some other method and then electrically isolating the wire trace
pattern from the edge electrode pattern by laser etching or some
other technique.
[0019] This invention features a method of manufacturing a touch
panel, the method comprising coating a glass substrate with a
resistive layer; applying a pattern of conductive edge electrodes
to the resistive layer and applying a conductive wire trace pattern
to the resistive layer and electrically isolating the conductive
edge electrodes from the conductive wire traces.
[0020] The conductive layer is typically a tin antimony oxide
composition and the glass substrate may be a soda lime glass
composition.
[0021] The step of applying the pattern of conductive edge
electrodes and the wire trace pattern typically includes screen
printing silver/frit paste on the resistive layer in the form of
the edge electrode pattern and the wire trace pattern. The step of
electrically isolating includes using a laser beam to ablate the
resistive material between the edge electrodes and the wire traces.
The step of applying a protective insulative border layer usually
includes screen printing an insulative composition over the edge
electrodes and the wire traces. The insulative composition is
preferably a lead borosilicate glass composition.
[0022] The panel is subjected to an elevated temperature in a first
period of time to burn off any organic material and then a dwell
period at the elevated temperature to cure the electrodes and wire
trace materials and to fuse the insulative border layer
material.
[0023] The elevated temperature is typically between 500.degree.
C.-525.degree. C., the first time period is approximately 5
minutes, and the dwell period is approximately 2-3 minutes.
[0024] A touch panel in accordance with this invention includes a
glass substrate coated with a resistive layer on one surface
thereof; a pattern of edge electrodes on the resistive layer; a
wire trace pattern on the resistive layer; a trench in the
resistive layer between the wire trace pattern and the edge
electrode pattern to electrically isolate the wire trace pattern
from the edge electrode pattern; and a protective insulative border
layer over the edge electrode pattern and the wire traces.
[0025] The resistive layer may be a tin antimony oxide composition
and the glass substrate may be a soda lime glass composition. The
pattern of edge electrodes and the wire trace pattern is preferably
made of a silver/frit paste composition. The protective insulative
border layer is preferably formed from a lead borosilicate glass
composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Other objects, features and advantages will occur to those
skilled in the art from the following description of a preferred
embodiment and the accompanying drawings, in which:
[0027] FIG. 1 is a schematic view of a prior art touch screen panel
assembly;
[0028] FIG. 2 is a schematic view of the touch screen panel of the
subject invention just before the edge electrode pattern and the
wire trace pattern are screen printed on the resistive it)
coating;
[0029] FIG. 3 is a schematic view of the touch screen panel of the
subject invention after the edge electrode pattern and the wire
trace pattern are screen printed on the edges of the touch screen
panel;
[0030] FIG. 4 is a side cut-away view of a portion of the touch
screen panel of the subject invention showing how a wire trace is
electrically isolated from the electrodes of the edge electrode
pattern;
[0031] FIG. 5 is another cross-sectional view of a portion of the
touch screen panel of the subject invention after the protective
insulative border layer is deposited over the edge electrode
pattern and the wire trace pattern;
[0032] FIG. 6 is a chart showing the preferred firing dwell times
and temperatures associated with manufacturing the touch screen
panel of the subject invention; and
[0033] FIG. 7 is a flow chart depicting the primary manufacturing
steps associated with the method of making the touch screen panel
assembly in accordance with this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0034] Prior art touch screen panel 10, FIG. 1, includes substrate
12 which usually includes an insulative layer (e.g., glass), a
resistive layer over the primary working surface of the insulative
layer, and a pattern of conductive edge electrodes 14 and terminal
electrodes, usually corner electrodes 16, on the resistive layer as
is known in the art. There are additional corner electrodes (not
shown) one at each other corner 18, 20, and 22 of the touch screen.
The edge electrodes 14 repeat in some predetermined patterned
fashion along each edge 24, 26, 28, and 30 of panel 10.
[0035] Wires 32, 34, 36, and 38 extend to each corner electrode and
with their ends stripped of insulation are soldered to the
respective corner electrodes in order to generate the appropriate
electrical field across the working surface 40 of panel 10. So, for
example, wire 32 extends along edges 24 and 26 of panel 10 to the
corner electrode (not shown) at corner 18; wire 34 extends along
edge 24 of panel 10 to corner electrode 16; wire 38 extends alone
edges 24 and 30 of panel 10 to a corner electrode (not shown) at
corner 20; and wire 36 extends along edge 24 of panel 10 to a
corner electrode (not shown) at corner 22. In some prior art
embodiments, an insulative tape and then an insulated noise shield
layer 44 may be laid between the wires and the edge electrodes and
to electrically isolate edge electrodes 14. A hole is then formed
in the insulative tape proximate each corner electrode as shown at
46 in order to solder the ends of each wire to the appropriate
corner electrode. Alternatively, the tape ends proximate each
corner electrode. In other embodiments, the wires are simply taped
to the edges of panel 10. In still other embodiments, tape layer 48
and/or a protective (e.g., "Kapton") tape layer 50 are placed over
the wires. Insulated noise shield layer 44 may be placed over the
edge electrodes and under wires 32, 34, 36, and 38.
[0036] In FIG. 1, the thickness and width of border layers 44, 48,
and 50 are greatly exaggerated for the purposes of illustration as
is the thickness of substrate 12. Actual touch screen panels are
usually {fraction (1/8)} inch thick or less and layers 44, 48, and
50 are substantially thinner than that but still wires 32, 34, 36,
and 38 make the completed assembly appear somewhat bulky and
unfinished.
[0037] Moreover, prior art touch screen panel 10 in some cases is
not very reliable because the solder joints between the individual
wires and the corner electrodes can fail. Further, the act of
soldering the ends of each wire to the corner electrodes can damage
the electrodes or 2) even crack the substrate of the touch screen
panel. In addition, the assembly process wherein the wires are
soldered at their ends to the corner electrodes and taped to the
edges of the panel is labor intensive and hence costly.
[0038] In the subject invention, however, the wiring and protective
layer is integrated as a part of the touch screen panel so that
there are no bulky wires or layers of tape associated with the
touch screen panel as is the case with the prior art.
[0039] Touch screen panel 48, FIG. 2 in accordance with this
invention is manufactured by applying a resistive coating 50,
(e.g., tin antimony oxide) by a vacuum sputter process to glass
substrate 52 (e.g., a soda lime glass composition). Coating 50 is
less than 1000 angstroms thick and substrate 52 is typically
between 1-3 mm thick and 15 inches on a diagonal depending on the
specific application.
[0040] Conductive edge electrode pattern 54, FIG. 3 is then screen
printed on resistive coating 50 using a conductive silver/frit
paste, (DuPont 7713) and at the same time wire trace pattern 56 is
screen printed on resistive coating 50 also using conductive
silver/frit paste, step 100 FIG. 7.
[0041] As shown in FIG. 3 wire trace 58 begins at junction 60 and
extends along the edge of panel 48 to corner electrode 62 of edge
electrode pattern 54. Wire trace 64 similarly begins at junction 60
and extends along the opposite edit of panel 4S to corner electrode
66 of edge electrode pattern 54. Wire trace 68 begins at junction
60 and extend to corner electrode 70 and wire trace 72 begins at
junction 60 and extends to corner electrode 74 of edge electrode
pattern 54. The height of each wire trace is typically between
12-16 microns high and between 0.015" and 0.025" wide. Junction 60
uniquely forms a single attachment location for the controller
interface which creates the electrical field across the touch
screen.
[0042] Edge electrode pattern 54 may take the form of the pattern
disclosed in corresponding application Ser. No. 09/169,391 or the
forms disclosed in U.S. Pat. No. 4,198,539; 4,293,734; or 4,371,746
hereby incorporated herein by this reference. Typically the edge
electrode pattern and the wire trace pattern occupy only about 3/8
in. on the edges of panel 48 and thus FIG. 3 is not to scale.
[0043] After a drying operation at 120.degree. C. for 5 minutes to
dry the silver/frit paste, the next step in the process is to
electrically isolate each wire trace from the electrodes of the
edge electrode pattern other than the corner electrodes and, in
cases where there are two or more adjacent wire traces, to
electrically isolate them from each other, step 102, FIG. 7.
[0044] As shown in FIG. 4 laser 80 is used to ablate resistive
coating 50 in the area between wire trace 58 and edge electrode
pattern 54 to a depth typically corresponding to the top of glass
substrate 52. In this way, wire trace 58 is electrically isolated
from edge electrode pattern 54 and a similar technique is used to
isolate wire traces 58, 72, 68, and 64 from each other wherever
there are two or more traces and also from the edge electrodes of
the edge electrode pattern adjacent each wire trace.
[0045] In the preferred embodiment, a Q-switched YAG laser was used
to form a 0.008-0.010 inch wide trench 82 in resistive coating 50.
The laser beam had a wavelength of 1.06 microns, and the average
power was 32 watts. Other ablation or etching processes may be used
to provide electrical isolation and, in some cases, trench 82 need
not extend completely through resistive coating 50 provided
electrical isolation is provided (i.e., some or a little resistive
material may remain).
[0046] In the next step, a protective insulative border layer, 86,
FIG. 5 is deposited over the wire traces and the edge electrode
pattern filling the trenches between adjacent wires and the
trenches between the wire traces and the edge electrodes adjacent
them. In another embodiment, the insulative material is deposited
only in the trenches between the wire traces and the edge
electrodes adjacent them.
[0047] In the preferred embodiment, step 104, FIG. 7, an insulative
lead borosilicate lass composition (DuPont DG-150) is screen
printed about the border area of the touch panel over the wire
trace pattern and the edge electrode pattern. The width of border
layer 86, FIG. 5 is typically about 1/2 in. and has height of about
12 microns after firing.
[0048] After lead-borosilicate-glass layer 86 dries at 120.degree.
C. for 5 minutes (an optional step) it and the conductive
silver/frit paste of the edge electrode pattern and the wire trace
pattern are cured by firing, preferably at the same time in an
infrared oven, step 106, FIG. 7.
[0049] During this firing step, the organic binders of the
silver/frit paste and the lead borosilicate glass layer must be
allowed to escape the outer layer before the lead borosilicate
glass layer fully cures to prevent voids and defects.
[0050] Accordingly, outgassing is allowed to occur before the peak
temperature in the infrared oven is reached whereupon the
silver/frit paste is cured and the lead borosilicate glass fully
fuses.
[0051] As shown in FIG. 6, the preferred firing profile consists of
a ramp from room temperature up to 500.degree. C.-525.degree. C. in
approximately 5 minutes in order to complete the solvent
evaporation and burn out the organic binders in the thick film
materials. The ramp is followed by a dwell period above 500.degree.
C. for 2-3 minutes to allow the frit glass to melt and the silver
to sinter. The substrate is then brought back to ambient
temperature. An additional tiring profile may consist of a ramp
from room temperature to 300.degree. C. with a dwell period between
300-400.degree. C. for 6-10 minutes to provide additional time to
burn out the organic binders if required. This dwell period is
followed by a second ramp to the peak temperature of 500.degree.
C.-525.degree. C. with little or no dwell period. The substrate is
then brought back to ambient temperature. Before firing, a separate
drying step is performed to evaporate the solvents in the thick
film materials. The drying profile consists of a ramp to
120-135.degree. C. for a dwell period of 2-6 minutes and then
brought back to ambient temperature. The insulative lead
borosilicate glass layer advantageously protects the wire traces
and the edge electrodes and isolates then from each other. In the
prior art, tape was used which was unsightly and often peeled up
which left the edge electrodes and the wire traces unprotected.
Moreover, by co-firing the paste of the edge electrode pattern and
the wire traces, and the borosilicate glass protective layer, the
separate firing steps of the prior art are eliminated.
[0052] After firing, a hard coat and/or an anti-microbial and/or an
anti-scratch coatings may be applied to the active area of the
touch panel (and optionally over the protective border layer) by
spraying, and/or dipping techniques step 108, FIG. 7 and then a
wiring cable is attached to junction 60, FIG. 3, step 110, FIG.
7.
[0053] Although specific features of the invention are shown in
some drawings and not in others, this is for convenience only as
each feature may be combined with any or all of the other features
in accordance with the invention. The words "including",
"comprising", "having", and "with" as used herein are to be
interpreted broadly and comprehensively and are not limited to any
physical interconnection. Moreover, any embodiments disclosed in
the subject application are not to be taken as the only possible
embodiments.
[0054] Other embodiments will occur to those skilled in the art and
are within the following claims:
* * * * *