US20010028343A1 - Touch panel with an integral wiring harness - Google Patents

Abstract

A method of manufacturing a touch screen panel in which a glass substrate is coated with a resistive layer, a dielectric border layer is deposited on the periphery of the resistive layer, a pattern of conductive edge electrodes is applied to the resistive layer, and a conductive wire trace pattern is applied to the dielectric border layer to electrically isolate the wire trace pattern from the edge electrodes. The invention also features a touch screen panel manufactured in accordance with this method.

Description

RELATED APPLICATIONS
• This application claims priority of Provisional application Ser. No. 60/179,874 filed Feb. 2, 2000.[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.[0002]
FIELD OF THE INVENTION
• This invention relates to a touch screen panel with an integral wiring harness which eliminates the bulky and unreliable prior art external wiring harnesses associated with touch screen panels and lowers the cost of manufacturing touch screen panel assemblies.[0003]
BACKGROUND OF THE INVENTION
• 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 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 a wiring harness 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 tape 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 readily noticeable and detract from the appearance of the touch screen panel.[0010]
SUMMARY OF THE INVENTION
• It is therefore an object of this invention to provide a touch screen panel with an integral wiring harness.[0011]
• It is a further object of this invention to provide a touch screen panel with an integral wiring harness 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 an integral wiring harness.[0014]
• It is a further object of this invention to provide such a method of manufacturing a touch screen panel with an integral wiring harness 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 an integral wiring harness which is less labor intensive and less costly than prior art methods.[0016]
• 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 an integral wiring harness wherein the prior art individual wires are replaced with conductive traces deposited on an insulative border layer on the panel either by printing or by some other method. The low profile conductive lands provide a more reliable, less expensive, and more aesthetically pleasing touch screen panel. The insulative border layer electrically isolates the conductive wire traces from the edge electrodes of the touch screen panel.[0017]
• This invention features a method of manufacturing a touch screen panel. A glass substrate is coated with a resistive layer, a dielectric border layer is deposited on the periphery of the resistive layer, and a pattern of conductive edge electrodes are applied to the resistive layer and typically, at the same time, a conductive wire trace pattern is applied to the dielectric border layer which electrically isolates the wire trace pattern from the edge electrodes printed on the resistive layer.[0018]
• The resistive layer is typically a tin oxide composition and the glass substrate is typically a soda lime glass composition. The step of depositing the dielectric border layer preferably includes screen printing a lead borosilicate glass composition on the periphery of the resistive layer. The step of applying the pattern of conductive edge electrodes to the resistive layer and the step of applying the conductive wire trace pattern to the dielectric border layer preferably includes screen printing silver/frit paste on the resistive layer to form the edge electrode pattern and screen printing a silver/frit paste on the dielectric border layer to form the wire trace pattern.[0019]
• The method of this invention may further include the step of applying a protective border layer over the edge electrodes and the wire traces. The protective border layer may be screen printed over the edge electrodes and the wire traces and typically the material used is a lead borosilicate glass composition. In the preferred embodiment the applied edge electrodes, wire traces, the dielectric border layer and the protective border layer are all fired at the same time.[0020]
• The panel is subjected to an elevated temperature in a first period of time to burn off any organic material and a dwell period at the elevated temperature to cure the electrodes and wire trace materials and to fuse the border layer material. The elevated temperature is typically between 500° C.-525° C., the first time period is approximately 5 minutes and the dwell period is approximately 2-3 minutes.[0021]
• A touch screen panel in accordance with the subject invention includes a glass substrate with a resistive layer deposited on one surface thereof, a dielectric border layer on the periphery of the resistive layer, a conductive wire trace pattern on the dielectric border layer, and a pattern of conductive edge electrodes on the resistive layer.[0022]
• The resistive layer is preferably a tin oxide composition and the glass substrate is typically a soda lime glass composition. The dielectric border layer is usually formed from a lead borosilicate glass composition. The conductive wire trace pattern and the conductive edge electrodes are typically formed form a silver/frit paste composition. The touch screen panel of the subject invention may further include a protective border layer over the edge electrodes and over the wire traces. Lead borosilicate glass may be used as the material for the protective border layer.[0023]
• In another embodiment, the wire trace pattern is placed over the edge electrode pattern and electrically isolated therefrom by a dielectric border layer between the wire trace pattern and the conductive edge electrodes. In accordance with this method, a glass substrate is coated with a resistive layer; a pattern of conductive edge electrodes are printed on the resistive layer, a dielectric border layer is printed over the conductive edge electrode pattern, and a wire trace pattern is printed on the dielectric border layer.[0024]
• A touch panel in accordance with this embodiment comprises a glass substrate with a resistive layer deposited on one surface thereof, a pattern of conductive edge electrodes on the resistive layer, a dielectric border layer over the pattern of conductive edge electrodes, and a wire trace pattern on the dielectric border layer.[0025]
BRIEF DESCRIPTION OF THE DRAWINGS
• 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:[0026]
• FIG. 1 is a schematic view of a prior art touch screen panel assembly;[0027]
• FIG. 2 is schematic view of a touch screen panel just before the dielectric border layer is applied to the resistive coating in accordance with the subject invention;[0028]
• FIG. 3 is a schematic view of the touch screen panel shown in FIG. 2 after the dielectric border layer is applied to the resistive coating;[0029]
• FIG. 4 is a schematic view of the touch screen panel shown in FIG. 3 after the pattern of conductive edge electrodes is applied to the resistive layer and the conductive wire trace pattern is applied to the dielectric border layer in accordance with the subject invention;[0030]
• FIG. 5 is a cross-sectional view of a portion of the touch screen panel in accordance with the subject invention after a protective insulative border layer is applied over the edge electrodes and the wire traces;[0031]
• FIG. 6 is a graph showing the temperatures and dwell times associated with a step of firing the applied edge electrodes, the wire traces, the dielectric border layer, and the insulative protective border layer in accordance with the subject invention;[0032]
• FIG. 7 is a flow chart depicting the primary manufacturing steps associated with making the touch screen panel of the subject invention;[0033]
• FIG. 8 is a cross sectional view of a touch panel in accordance with another embodiment of the subject invention in which the dielectric border layer is deposited over the edge electrode pattern;[0034]
• FIG. 9 is a top view of the touch screen panel after the border layer is deposited over the edge electrode pattern but before the wire trace pattern is screen printed thereon; and[0035]
• FIG. 10 is a flow chart depicting the primary manufacturing steps associated with assembling the touch screen panel shown in FIG. 8.[0036]
DISCLOSURE OF THE PREFERRED EMBODIMENT
• Prior art[0037]touch screen panel10, FIG. 1, includessubstrate12 which usually includes an insulative layer (e.g., glass), a resistive layer over the primary working surface of the insulative layer, and a pattern ofedge electrodes14 and terminal electrodes, usuallycorner electrodes16, on the resistive layer as is known in the art. There are additional corner electrodes (not shown) one at eachother corner18,20, and22 of the touch screen. Theedge electrodes14 repeat in some predetermined patterned fashion along eachedge24,26,28, and30 ofpanel10.
• [0038]Wires32,34,36, and38 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 workingsurface40 ofpanel10. So, for example,wire32 extends along edges24 and26 ofpanel10 to the corner electrode (not shown) atcorner18;wire34 extends alongedge24 ofpanel10 tocorner electrode16;wire38 extends along edges24 and30 ofpanel10 to a corner electrode (not shown) atcorner20; andwire36 extends alongedge24 ofpanel10 to a corner electrode (not shown) atcorner22. In some prior art embodiments, an electrical tape and then an insulatedcopper shield layer44 may be laid between the wires and the edge electrodes and to electrically isolateedge electrodes14. A hole is then formed in the insulative tape proximate each corner electrode as shown at46 in order to solder the ends of each wire to the appropriate corner electrode. Alternatively,layer44 ends just before each corner electrode. In other embodiments, the wires are simply taped to the edges ofpanel10. In still other embodiments,tape layer48 and/or a protective (e.g., “Kapton”)tape layer50 are placed over the wires. Insulated noiseshield tape layer44 may be placed over the edge electrodes and underwires32,34,36, and38.
• In FIG. 1, the thickness and width of[0039]border layers44,48, and50 are greatly exaggerated for the purposes of illustration as is the thickness ofsubstrate12. Actual touch screen panels are usually ⅛ inch thick or less and layers44,48, and50 are substantially thinner than that but stillwires32,34,36, and38 make the completed assembly appear somewhat bulky and unfinished.
• Moreover, prior art[0040]touch screen panel10 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 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.
• In the subject invention, in contrast, the wiring 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.[0041]
• [0042]Touch screen panel48, FIG. 2 in accordance with this invention is manufactured by applying resistive coating50 (e.g., tin antimony oxide) by a vacuum sputter process to glass substrate52 (e.g., soda lime glass).Coating50 is less than 1000 angstroms thick andsubstrate52 is typically between 1-3 mm thick and 15 inches on a diagonal.
• In this[0043]invention step100, FIG. 7dielectric border layer53, FIG. 3 is deposited on the periphery ofresistive coating50 by screen printing a lead borosilicate glass composition ⅛ inch wide and 10 microns thick (after firing) along the edges ofpanel48.Border layer53 provides electrical isolation between the individual wire traces of the wiring harness and electrical isolation between the wire traces and the edge electrodes of the edge electrode pattern.
• After[0044]dielectric border53 dries at 120° C. for 5 minutes, conductiveedge electrode pattern54, FIG. 4 is then screen printed onresistive coating50 using a conductive silver/frit paste available from DuPont (No. 7713) and at the same timewire trace pattern56 is screen printed onborder layer53 also using silver/frit paste,step102, FIG. 7.
• As shown in FIG. 4[0045]wire trace58 begins atjunction60 and extends along the edge ofpanel48 tocorner electrode62 ofelectrode pattern54.Wire trace64 similarly begins atjunction60 and extends along the opposite edge ofpanel48 tocorner electrode66 ofedge electrode pattern54.Wire trace68 begins atjunction60 and extends to cornerelectrode70 andwire trace72 begins at junction and extends to cornerelectrodes74 ofelectrode pattern54.
• The height of each wire trace is typically between 12-16 microns and each trace is between 0.015″ and 0.025″ wide.[0046]
• [0047]Edge electrode pattern54 may take the form of the pattern disclosed of co-pending application Ser. No. 09/169,391, or the forms disclosed in U.S. Pat. Nos. 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 ⅜ inch on the edges of[0048]panel48 and thus FIG. 4 is not to scale.
• After a drying operation at 120° C. for 5 minutes wherein the silver/frit paste is dried, an insulative lead borosilicate glass composition (DuPont DG-150) is typically screen printed about the border area of the touch panel over the wire trace pattern and the edge electrode pattern,[0049]step104, FIG. 7. The width of the protective border layer,86, FIG. 5 is typically ½ inch and it has a height of about 12 microns after firing.
• After lead[0050]borosilicate glass layer86 dries at 120° C. for 5 minutes, (an optional step) it and the conductive silver/frit paste of the edge electrode pattern, the wire trace pattern and the dielectric border layer are cured by firing at the same time in an infrared oven,step106, FIG. 7.
• During this firing step, the organic binders of the silver/frit paste, the dielectric layer, and the outer borosilicate layer must be allowed to escape the outer layer before the lead borosilicate glass layer fully cures to prevent voids and defects.[0051]
• Accordingly, in this invention, outgassing is allowed to occur before the peak temperature in an infrared oven is reached whereupon the silver/frit paste is cured and the lead borosilicate glass fully fuses.[0052]
• As shown in FIG. 6, the preferred firing profile consists of a ramp from room temperature up to 500° C.-525° 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° 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 firing profile may consist of a ramp from room temperature to 300° C. with a dwell period between 300-400° 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° C.-525° 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° 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 them 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, the dielectric border layer, and the lead borosilicate glass protective layer, the separate firing steps of the prior art are eliminated.[0053]
• After firing, a hard coat and/or anti-microbial, and/or anti-scratch coatings may be applied to the active area of the touch panel (and optionally over the protective border layer) by dipping and/or spraying techniques,[0054]step108, FIG. 7 and, after any of these additional coatings are cured, a wiring harness is attached tojunction60, FIG. 3, step110 FIG. 7.
• In another embodiment of the subject invention,[0055]dielectric border layer53, FIG. 8 is placed overedge electrode pattern54 to increase the active area ofpanel48.
• [0056]Glass substrate52 is coated withresistive layer50 as discussed above and then edgeelectrode pattern54 is screen printed onresistive layer50,step200, FIG. 10 and allowed to dry.Dielectric border layer53 is the screen printed overedge electrode pattern54,step202 as shown in FIG. 9 leaving gaps ororifices120,122,124, and126 indielectric border layer53 proximate the corner electrodes ofedge electrode pattern54 so that the terminal ends of the wire traces make electrical contact with the corner electrodes. Afterdielectric border layer53 dries,wire trace pattern68, FIG. 8 is screen printed ondielectric border layer54,step204, FIG. 10. The terminal ends of the wire traces extend throughorifices120,122,124, and126, FIG. 9 indielectric layer53 and make electrical contact with the corresponding corner electrodes of the edge electrode pattern underorifices120,122,124, and126. As shown at206, FIG. 10 processing then typically continues in accordance withsteps104,106,108 and110, FIG. 7 and typicallyprotective border layer86, FIG. 8 is applied by screen printing and the assembly is then fired.
• Although specific features of this invention are shown in some drawings and not 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.[0057]
• Other embodiments will occur to those skilled in the art and are within the following claims:[0058]

Claims (41)

What is claimed is:

1. A method of manufacturing a touch screen panel, the method comprising:

coating an insulative substrate with a resistive layer;

depositing a dielectric border layer on the periphery of the resistive layer; and

applying a pattern of conductive edge electrodes to the resistive layer and applying a conductive wire trace pattern to the dielectric border layer to electrically isolate the wire trace pattern from the edge electrodes.

2. The method of

claim 1

in which the resistive layer is a tin 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 depositing the dielectric border layer includes screen printing a lead borosilicate glass composition on the periphery of the resistive layer.

5. The method of

claim 1

in which the step of applying the pattern of conductive edge electrodes to the resistive layer and the step of applying the conductive wire trace pattern to the dielectric border layer includes screen printing silver/frit paste on the resistive layer to form the edge electrode pattern and simultaneously screen printing a silver/frit paste on the dielectric border layer to form the wire trace pattern.

6. The method of

claim 1

further including the step of applying a protective border layer over the edge electrodes and the wire traces.

7. The method of

claim 6

in which the step of applying the protective border layer includes screen printing an insulative composition over the edge electrodes and the wire traces.

8. The method of

claim 7

in which the insulative composition is a lead borosilicate glass composition.

9. The method of

claim 6

further including the step of firing the applied edge electrodes, the wire traces, the dielectric border layer, and the protective border layer.

10. The method of

claim 9

in which firing includes subjecting the panel to an elevated temperature in a first period of time to burn off any organic material and a dwell period at the elevated temperature to cure the electrodes and wire trace materials and to fuse the border layer materials.

11. The method of

claim 10

in which the elevated temperature is between 500° C.-525° C., the first time period is approximately 5 minutes and the dwell period is approximately 2-3 minutes.

12. A touch screen panel comprising:

a substrate with a resistive layer deposited on one surface thereof,

a dielectric border layer on the periphery of the resistive layer;

a conductive wire trace pattern on the dielectric border layer; and

a pattern of conductive edge electrodes on the resistive layer.

13. The touch screen panel of

claim 12

in which the resistive layer is a tin oxide composition.

14. The touch screen panel of

claim 12

in which the substrate is glass.

15. The touch screen panel of

claim 12

in which the dielectric border layer is formed from a lead borosilicate glass composition.

16. The touch screen panel of

claim 12

in which the conductive wire trace pattern is formed from a silver/frit paste composition.

17. The touch screen panel of

claim 12

in which the pattern of conductive edge electrodes are formed from a silver/frit paste composition.

18. The touch screen panel of

claim 12

further including a protective border layer over the edge electrodes and the wire traces.

19. The touch screen panel of

claim 18

in which the protective border layer is formed from a lead borosilicate glass composition.

20. A method of manufacturing a touch screen panel, the method comprising:

coating a substrate with a resistive layer;

applying a pattern of conductive edge electrodes to the resistive layer;

depositing a dielectric border layer over the conductive edge electrodes; and

applying a wire trace pattern on the dielectric border layer.

21. The method of

claim 20

in which the resistive layer is a tin oxide composition.

22. The method of

claim 20

in which the substrate is glass.

23. The method of

claim 20

in which the step of depositing the dielectric border layer over the conductive edge electrodes includes screen printing a lead borosilicate glass composition on the periphery of the touch screen panel over the conductive edge electrodes.

24. The method of

claim 20

in which the step of applying the pattern of conductive edge electrodes includes screen printing silver/frit paste on the resistive layer to form the edge electrode pattern.

25. The method of

claim 20

in which the step of applying a wire trace pattern includes screen printing silver/frit paste on the dielectric border layer to form the wire trace pattern thereon.

26. The method of

claim 20

further including the step applying a protective border layer over the wire trace pattern and the dielectric border layer.

27. The method of

claim 26

in which the step of applying the protective border layer includes screen printing an insulative composition over the wire trace pattern and the dielectric border layer.

28. The method of

claim 27

in which the insulative composition is a lead borosilicate glass composition.

29. The method of

claim 27

further including the step of firing the applied edge electrodes, the wire traces, the dielectric border layer, and the border layer.

30. The method of

claim 20

in which firing includes subjecting the panel to an elevated temperature in a first period of time to burn off any organic material and a dwell period at the elevated temperature to cure the electrodes and wire trace materials and to fuse the border layer materials.

31. The method of

claim 30

in which the elevated temperature is between 500° C.-525° C., the first time period is approximately 5 minutes and the dwell period is approximately 2-3 minutes.

32. A touch panel comprising:

a substrate with a resistive layer deposited on one surface thereof;

a pattern of conductive edge electrodes on the resistive layer;

a dielectric border layer over the pattern of conductive edge electrodes; and

a wire trace pattern on the dielectric border layer.

33. The touch panel of

claim 32

in which the resistive layer is a tin oxide composition.

34. The touch screen panel of

claim 32

in which the substrate is glass.

35. The touch screen panel of

claim 32

in which the dielectric border layer is formed from a lead borosilicate glass composition.

36. The touch screen panel of

claim 32

in which the conductive wire trace pattern is formed from a silver/frit paste composition.

37. The touch screen panel of

claim 32

in which the pattern of conductive edge electrodes are formed from a silver/frit composition.

38. The touch screen panel of

claim 32

further including a protective border layer over the edge electrodes and the wire traces.

39. The touch screen panel of

claim 38

in which the protective border layer is formed from a lead borosilicate glass composition.

40. A method of manufacturing a touch screen panel, the method comprising:

coating an insulative substrate with a resistive layer;

depositing a dielectric border layer on the periphery of the resistive layer;

applying a pattern of conductive edge electrodes to the resistive layer and applying a conductive wire trace pattern to the dielectric border layer to electrically isolate the wire trace pattern from the electrodes;

depositing a protective border layer over the edge electrodes and the wire traces to protect them; and

co-firing the wire trace pattern, the edge electrodes, the dielectric border layer, and the protective layer all at the same time.

41. A method of manufacturing a touch screen panel, the method comprising:

coating a substrate with a resistive layer;

applying a pattern of conductive edge electrodes to the resistive layer;

depositing a dielectric border layer over the conductive edge electrodes;

applying a wire trace pattern on the dielectric border layer;

applying a protective border layer over the wire trace pattern; and

co-firing the wire trace pattern, the edge electrodes, the dielectric border layer, and the protective border layer all at the same time.

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