WO1992013328A1

WO1992013328A1 - Capacitive touch screen

Info

Publication number: WO1992013328A1
Application number: PCT/US1992/000257
Authority: WO
Inventors: Wayne W. Maw
Original assignee: Rgb Dynamics
Priority date: 1991-01-17
Filing date: 1992-01-14
Publication date: 1992-08-06
Also published as: AU1258392A

Abstract

A capacitive touch screen (10) for providing a user interface at a computer terminal or control panel. The capacitive touch screen (10) is provided on the back side thereof with a thin-film conductive metal layer (20) which serves as a grounded capacitor plate as well as an RFI shield. The other capacitor plate of the capacitive touch screen is also provided by a thin-film conductive metal layer (22) which is separated from the first thin-film conductive metal layer (20) by a dielectric layer (24a, 24b). However, the second thin-film indium tin oxide layer (22) is patterned by chemical or laser etching to provide discrete touch-sensitive capacitive areas (12a-12e) which can be discretely detected when a user touches the user interface side of the screen. The second thin-film conductive layer (22) which is patterned is located completely internally to the screen since there is a second dielectric layer (26) which is formed over the second thin-film metal layer (22).

Description

CAPACITIVE TOUCH SCREEN BACKGROUND

The Field of the Invention

The present invention relates to computer touch screens and control panels, and more particularly, the present invention relates to a capacitive touch screen for use at computer terminals and/or control panels. 0

Technology Review and Background

Capacitive touch screens are used in a variety of computerized systems as a means of providing user interface at computer terminals, control panels and the like. Such 5 capacitive touch screens operate on the principle that when a user touches a screen or control panel there is a change in the effective capacitance of an RC circuit. The change in the effective capacitance of the RC circuit in turn changes the oscillation frequency of an oscillator circuit, 0 which can then be detected so as to sense the area of the screen or control panel that has been touched. This accordingly allows various kinds of input and control signals to be effectively provided to the computer system by the simple expedient of having the user touch the

-> -, screen.

In the past it has been typical to provide a glass layer in connection with the touch screen which is coated on the user interface side of the glass screen with a thin- film layer of conductive material such as indium tin oxide

³⁰ (hereinafter sometimes "ITO") . The indium tin oxide layer is typically patterned by either chemical etching or by etching the thin-film conductive layer with a laser so as to provide various capacitive areas on the user interface side of the screen which are touch-sensitive. On the

-- opposite or back side of the glass layer there is typically deposited another thin-film layer of indium tin oxide which uniformly covers the other side of the glass layer. The uniform layer of indium tin oxide which is on the back side of the screen is typically electrically connected to earth ground so that that layer of conductive material acts as a grounded capacitor plate with the glass layer serving as a dielectric material between the grounded capacitor plate and various capacitive touch-sensitive areas which are patterned on the front user interface side of the screen. The- _unifor conductive layer on the back side of the screen also serves as a shield for filtering radio frequency interference or noise from the control circuitry and/or cathode ray circuitry and apparatus.

When indium tin oxide is deposited at an extremely thin thickness (on the order of several hundred A) , the ITO will remain conductive but is optically transparent so that, for example, light emitting diodes or the beam of a cathode ray can still be visually perceived through the thin-film layer. However, because the coating of indium tin oxide is so thin (typically on the order of 400 A) over time the layer that is patterned on the user interface side of the screen will begin to wear and may also be easily scratched or damaged. This in turn will decrease the effectiveness of the various touch-sensitive capacitive areas that are used for user control.

Another problem which exists with the above-described type of conventional touch screen is that because the thin- film conductive layer which is patterned on the user interface side of the screen is a conductive layer and is directly connected to the electronic control circuitry which interfaces the touch-sensitive capacitive areas to the rest of the computer system, and because the control screen is .activated by the touch of a user, it is not uncommon to have static electricity discharged into the touch-sensitive capacitive areas of the screen, with the potential for damaging the electronic circuitry. This accordingly requires additional protective circuitry to typically be designed and built into the electronic control circuit, thus increasing its complexity and cost.

Further problems which have been experienced in connection with using conventional capacitive touch screens arise when such touch screens are intended for use in harsh environments, as for example in some types of chemical industrial control processes or the like. Again, due to the extremely thin coating which is required in order to preserve optical clarity, the thin-film indium tin oxide may be subjected to degradation because of the harsh chemicals in the environment. In some cases this may be minimized or eliminated by putting a further coating of silicone dioxide over the indium tin oxide layer but this of course adds further complication and expense to the manufacture of the capacitive touch screen.

Yet a further problem sometimes exists when capacitive touch screens are intended for use in very tightly controlled environments such as industrial clean rooms or in certain types of other sterile conditions such as may be encountered in the medical field. In these types of environments, users are often required to use thin, skin¬ tight rubber gloves and when doing so the rubber glove, which is itself a dielectric, may significantly reduce the level of capacitance that is to be sensed, to the point where it may be difficult for the control circuitry to discriminate when a user is attempting to activate one of the touch-sensitive areas on the screen. This may be compensated for by devising algorithms which are designed to detect lower levels of capacitance, but this in turn may also render the overall system less flexible because if a user attempts to activate an area when not using a rubber glove, the increased level of capacitance may tend to overpower the detection algorithm, causing erroneous data. Still a further area of concern exists with respect to the conventional capacitive touch screen technology in that occasionally for some types of applications there is increased risk of breakage with respect to the screen. In such cases, it may be desirable to protect users from direct contact with the glass layer in the event of such breakage, which typically will require laminating an additional layer of material such as urethane to the glass to ^"minimize the risk of exposure to sharp glass shards in the event of breakage. This increases expense and further complicates the manufacture of the touch screen.

__.3 Brief Summary and Objects of the Invention In view of the prior state of the art, it is a primary objective of the present invention to provide a capacitive touch sensitive screen which effectively eliminates wear of the thin-film conductive coatings used for defining the

20 capacitive touch-sensitive areas so that such thin-film coatings will not be subject to wear from touch contact or other environmental conditions such as abrasives, or acidic or caustic chemicals.

Another important object of the present invention is to provide a capacitive touch screen which is more effectively

25 protected from static electric discharges from a user without the need for additional expense of electronic components.

Still a further object of the present invention is to provide a capacitive touch screen which effectively reduces 0 the potential of user injury from broken glass in the event that the screen should be shattered.

Yet another important object of the present invention is to provide a capacitive touch screen which can be effectively used in environments such as clean rooms or the like where users are required to use thin rubber gloves as well as in environments where the use of gloves is not required, without having to alter detection algorithms to accommodate such differing environments. ₅ These and other objects and advantages of the present invention will become more fully apparent from the following drawings and detailed description of the invention or may be learned from the practice of the invention. Briefly summarized, the above and other objects 1₀ and advantages are realized in a capacitive touch screen which in one presently preferred embodiment is comprised of two glass substrates which are laminated together. Each of the glass substrates has on one side thereof a thin-film indium tin oxide layer deposited. The thin-film indium tin

__.:_. oxide layer on one of the substrates is positioned so as to be on the back side of the screen and is uniformly deposited on that side so as to form an essentially continuous conductive layer which serves as the grounded plate of a capacitor and which also serves to filter radio

20 frequency noise. The other thin-film indium tin oxide layer is patterned and serves as the active conductive layer performing the various touch-sensitive capacitive areas which will be activated by a user at the user interface side of the screen. The patterned, active touch-

25 sensitive layer of thin-film indium tin oxide is positioned so that the glass substrate on which it is deposited faces outwardly and becomes the user interface side of the screen, thereby positioning the active conductive layer on the inside of the screen so as to be protected from wear due to touching by the user as well as thereby being

30 protected from caustic environmental conditions such as harsh chemicals or the like. The two glass substrates are laminated together using an optically clear laminating material such as polyurethane or polyvinylbutelate (PVB) .

By positioning the active thin-film indium tin oxide

35 capacitive layer on the inside of the screen, the glass substrate for that thin-film layer also serves as a protective dielectric layer which insulates the active indium tin oxide conductive layer from damage due to static = electric discharges, and also effectively eliminates any significant differences in the capacitance levels to be detected irrespective of whether rubber gloves are worn or not.

1₀ BRIEF DESCRIPTION OF THE DRAWINGS

^' In order that the manner in which the above-recited and other advantages and objects of the invention are obtained, a more particular description of the invention will be rendered by reference to specific embodiments thereof which

_ D are illustrated in the appended drawings. Understanding that these drawings depict only presently preferred embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and

20 detail through the use of the accompanying drawings in which:

Figure 1 is a perspective view of one presently preferred embodiment of the capacitive touch screen of the present invention, illustrating in particular the various

25 touch-sensitive areas of the screen which may be activated.

Figure 2 is an enlarged perspective view of a portion of the capacitive touch screen of Figure 1 with the portion along line 2-2 of Fig. 1 broken away to reveal the cross- sectional structure of the screen in greater detail, as well as illustrating in greater detail the touch-sensitive 0 areas which are patterned on the screen.

Figure 3 is an enlarged cross-sectional view which more particularly illustrates the various layers from which the capacitive touch screen of Figure 1 is constructed.

Figure 4 is an exploded perspective view which more 5 particularly illustrates several of the layers for purposes of depicting how the touch-sensitive areas are protected on an interior surface of one of the layers of the screen.

Figure 5 is an enlarged cross-sectional view which illustrates a second presently preferred embodiment of the capacitive touch screen of the present invention.

Figure 6 is a perspective view of the capacitive touch screen of the embodiment of Figure 6.

Figure 7 is an enlarged perspective view with portions broken away in the region of line 7-7 in Figure 6 so as to more particularly illustrate the cross-sectional structure of the embodiment of Figure 6 as well as more particularly illustrating the outer most touch-sensitive capacitive areas of that embodiment. Figure 8 is an enlarged cross-sectional view of a third presently preferred embodiment of a capacitive touch screen constructed in accordance with the present invention.

Figure 9 is an enlarged cross-sectional view of a further embodiment of a capacitive touch screen which may be constructed in accordance with the present invention.

Figure 10 is an enlarged cross-sectional view of still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT Reference is next made to a detailed description of the presently preferred embodiments of the invention as well as the presently understood best mode for practicing the invention, by reference to the accompanying drawings wherein like parts are designated with like numerals throughout.

With reference first to Figure 1, the capacitive touch screen of the present invention is illustrated in one presently preferred embodiment thereof as a curved screen for use, for example, at a computer terminal or the like.

The capacitive touch screen is generally designated at 10 δ and includes a plurality of capacitive touch-sensitive areas as generally designated at 12.

As illustrated in greater detail in the perspective view of Figure 2, the capacitive touch-sensitive areas 12 are typically patterned so aε to form a plurality of discrete touch-sensitive areas 12a-12e. Capacitive touch- sensitive areas 12a-12c each constitute areas which can be discretely detected when the screen is touched by a user. Touch-sensitive areas 12d and 12e are typically electrically connected so that together they form a single touch-sensitive area which can be activated.

With further reference to Figure 2, each of the touch- sensitive areas 12a-l2e are formed on the thin-film conductive coating, as hereinafter more fully described, which is deposited on one of the discrete layers of the screen. The thin-film conductive coating is etched either chemically or, for example, by laser etching so as to form the discrete touch-sensitive areas 12a-12b. Further, the etched pattern also forms conductive runs 14a-14c which terminate at a peripheral edge in conductive terminals 16a- 16e. The conductive terminals 16a-16e provide the connecting points to the control circuitry (not shown) which is used for purposes of detection and input to the control circuitry and computer system. The areas which are represented at 18 are indicative of the portions of the thin-film conductive coating which are removed by the etching process so as to form the touch-sensitive areas 12a-12e as well as the conductive runs 14a-14c and conductive terminals 16a-16e.

The various layers from which the capacitive touch screen 10 is constructed can be best understood in reference to Figures 2-4 taken together. As shown in those drawing figures, in one aspect of the present invention the capacitive touch screen comprises a first thin-film conductive means for providing a grounded capacitor plate layer. In the embodiment of Figures 1-4 the first thin- film conductive means for providing the grounded capacitive plate layer is comprised of a thin-film conductive coating of indium tin oxide which is on the order of about 400 A thick. The thin-film conductive layer comprises a uniform coating which is typically connected to earth ground. The thin-film conductive coating 20, in addition to providing a grounded capacitor plate layer, also serves as a shield for filtering to ground radio frequency interference and noise which may be generated by the cathode ray and computer control circuitry. As described in connection with other embodiments as illustrated in some of the later drawing figures, the first thin-film conductive means can also in some circumstances be comprised of a tin oxide layer which may typically be on the order of about 500 A to 5,000 A thick, and is preferably 3,000 A.

In a further aspect of the invention, the capacitive touch screen 10 comprises a second thin-film conductive means for providing a patterned touch-sensitive capacitive layer. In the embodiment illustrated in Figures 1-4 the second thin-film conductive means is comprised of a second thin-film coating of indium tin oxide 22 which is also on the order of about 400 A thick. At 400 A, indium tin oxide tends to still be an effective electrical conductor but also is thin enough so that it is optically transparent so that for example, a cathode ray or a light emitting diode which must be viewed through the touch screen will not be visually blocked or impaired. In other embodiments of the invention to be described more fully hereinafter, the second thin-film conductive means may also be comprised, for example, of a conductive coating of tin oxide which may be in the range of 500 A to 5,000 A thick.

In still a further aspect of the invention, the capacitive touch screen 10 is comprised of a first dielectric means for providing an essentially continuous dielectric layer interposed between the first and second conductive means. As illustrated in the embodiment of Figures 1-4, the first dielectric means is comprised, for example, of a first glass substrate layer 24a and a lamination layer 24b. The first glass substrate layer 24a is preferably on the order of about .062 inches thick and the lamination layer 24b is preferably on the order of about .015 inches thick.

In still a further aspect of the invention the capacitive touch screen 10 is comprised of a second dielectric means formed over the second conductive means for providing an optically transparent layer which is thick enough and hard enough to protect the second conductive means from damage due to static electric discharge from a user and from damage due to surface wear and scratching, and which therefore has a substantial thickness typically on the order of at least .005 inches or greater. In the embodiment of Figures 1-4, the second dielectric means is comprised, for example, of a second glass substrate layer 26 which is preferably .062 inches thick.

As best illustrated in Figure 3, each of the layers is curved so that the overall capacitive touch screen 10 can be implemented in connection with a computer terminal or the like. As will be seen best in reference to Figures

3 and 4, the thin-film conductive coating 20 which is deposited on the first glass substrate layer 24a is formed on the back side of the screen. The thin-film conductive layer 20 as noted above forms the grounded capacitor plate layer of the capacitive touch screen. The thin-film conductive layer 22 which is patterned and which is formed on the inside surface of the second glass substrate layer

26 forms the other capacitive plate and is the layer which is touch-sensitive from the user interface side of the screen. However, it is important to note that the various touch-sensitive capacitive areas which are patterned on the thin-film conductive coating 22 are not formed directly on the outer surface of the glass substrate layer 26, but rather, contrary to conventional technology, are formed on the inside surface of the second glass substrate layer 26. The two substrates are then laminated together using the laminating material 24b using conventional vacuum autoclaving apparatus.

Significantly, since the touch-sensitive capacitive areas which are patterned on the thin-film conductive layer 22 are located completely internally on the screen, they are not subject to wear from the user's touch nor are they subject to degradation due to exposure to harsh environments such as chemicals or abrasives. This virtually eliminates any wear of the thin-film conductive coating 22 over the life of the touch screen.

Furthermore, since the second glass substrate 26 is a dielectric, the thickness Dl of the glass substrate, which is substantial (typically on the order of .005 of an inch or thicker and preferably in the range of .062 inches), effectively serves to protect the thin-film layer 22 from static electric discharge which may occur when a user touches the screen. This is because the dielectric material of the second glass substrate 26 will insulate the thin-film conductive coating 22. Accordingly, this eliminates the need for additional electronic components and complexity in the electronic control circuitry which is external to the screen.

The effective capacitance which is provided by the dielectric characteristic of the second glass substrate 26 is high enough so that the difference between touching the user interface side of the screen either with or without a thin rubber glove on the hand of the user will not make any significant difference in the relative capacitive values which are otherwise sensed, thereby rendering the capacitive touch screen useful in a wider variety of environments and applications without having to devise separation detection algorithms for those differing environments.

While it is presently preferred that the thickness of the two glass substrates 24a and 26 be virtually the same in order to simplify the manufacturing procedure, the scope of the invention is not limited to that preferred thickness for the two glass substrate layers 24a and 26. Various design considerations may be taken into account in determining the relative thicknesses of the two glass substrate layers 24a and 26, such as, for example, the fact that the distance D2 provides a parasitic capacitance because of the dielectric characteristics of the glass substrate 24a. The parasitic capacitance should provide on one hand a sufficient capacitive value so as to lend some stability to the oscillation circuitry (not shown) but on the other hand should not be so great as to adversely effect the ability to detect the changing capacitance when the user interface side of the screen is touched. Moreover, a further consideration to be taken into account, particularly in relation to the thickness of the second glass substrate layer 26, is the ability to laminate that layer without having a rejection rate which is too high due to breakage of the glass as the thickness is decreased. It is presently anticipated, for example, that the range of thickness for the glass substrate layer 26 may be anywhere from .005 inches thick and greater.

A second embodiment as generally designated at 10a is illustrated in Figures 5-7. In that embodiment of the invention, the capacitive touch screen 10a is identical to the embodiment of Figures 1-4 except for two additional layers 28 and 30 which are added to the user interface side of the touch screen 10a. Layer 28 is a third thin-film conductive coating of indium tin oxide which is also on the order of about 400 A thick. Layer 30 is a third dielectric layer which is a thin-film layer on the order of about 5,000 A to 10,000 A thick. The thin-film dielectric layer 30 is typically comprised of a material such as silicone dioxide or titanium oxide. Both of the layers 28 and 30 are once again thin enough so as to be optically transparent.

The thin conductive coating 28 is patterned as best illustrated in Figures 6 and 7 to form discrete touch- sensitive areas 28a and 28b over the entire surface of the touch screen 10a. These areas are, as in the case of the active touch sensitive capacitive areas patterned onto the thin-film conductive layer 22 formed by chemical or laser etching to remove the portions 18 thereby forming the discrete areas 28a and 28b. The layer 28 is a passive layer which is used to enhance the user's electrical contact when touching the user interface side of the screen. Accordingly, if a user touches the screen with the very tip of a finger the discrete areas 28a and 28b will effectively increase the conductive area which is sensed from the user's touch. This helps to minimize data errors in using the capacitive touch screen.

The thin-film dielectric layer 30 is provided to simply protect the thin-film conductive layer 28 from undue wear and from exposure to chemically caustic or abrasive environments.

In yet a further embodiment as generally designated at 10c in Figure 8, the capacitive touch screen of the present invention may be implemented by depositing both of the thin-film conductive coating layers 20 and 22 on opposite sides of the first glass substrate layer 24 and by then laminating that layer with the laminating material 32 to the second glass substrate layer 26. However, the embodiment of Figure 8 is otherwise essentially identical in the other characteristics of the embodiments described previously. In yet a further embodiment of the invention, as illustrated generally at lOd in Figure 9, the capacitive touch screen of the invention may be implemented using a slightly different construction which is more suitable for applications where the capacitive touch screen is intended as a flat control panel or the like. In that embodiment the first thin-film conductive layer 34 is preferably a tin oxide layer which is on the order of 500 A to 5,000 A 0 thick, and is preferably 3,000 A. As in the case of the other embodiments, the thin-film conductive layer 34 is formed on the back side of the panel and serves as a grounded capacitor plate layer which also provides an RFI shield. The thin-film conductive layer 34 is deposited on 5 one side of the first glass substrate layer 36a which is preferably on the order of about one-eighth of an inch thick. A second glass substrate layer 36c is laminated at one side thereof with a laminating material 36b to the first glass substrate layer 36a. The two glass substrate 0 layers 36a and 36c together with the laminating material 36b together comprise a dielectric means which separates the capacitive plate layer formed by the first thin-film conductive layer 34 and a second thin-film conductive layer 38. ^ The second thin-film conductive layer 38 is also a tin oxide layer which is on the order of about 500 A to 5,000 A thick, is preferably 3,000 A, and is patterned to provide the touch sensitive areas in the manner previously described. The second thin-film conductive coating 38 is ⁰ then covered by a third glass substrate layer 42 which is on the order of about .062 inches to about .090 inches thick. The lamination layer 40 is typically on the order of about .015 inches thick.

In the embodiment which is illustrated in the cross- sectional view at Figure 10, the capacitive touch screen generally designated lOe is essentially identical to the embodiment of the capacitive touch screen lOd in Figure 9 except for two changes. By comparison of Figures 9 and 10, it will be noted that in the embodiment of the capacitive touch screen lOe the first glass substrate layer 36a and also the laminating material 36b which are illustrated in Figure 9 are not present in the embodiment of Figure 10. Furthermore, in the embodiment of Figure 10 there is included a thick-film layer 44 which is comprised of a graphic design patterned onto the back side of the glass substrate layer 36c. The layer 44 may be prepared using any one of a number of conventional techniques for placing the graphic design onto the back side of glass substrate layer 36c, as for example by silk screening, lithographic processes, photographic processes or the like.

In this type of capacitive touch screen lOe, there is no need for the first thin-film conductive layer 34 (see Fig. 9) which is used as the RF shield since background noise may not be present to any significant extent in the type of application for which the capacitive touch screen lOe is designed. In other words, rather than having a cathode ray, LED or LCD with the associated control circuitry which must be viewed through the touch screen, in the embodiment of the touch screen lOe the graphic design which is patterned onto layer 44 is used as a static display of information that identifies the appropriate touch-sensitive areas that are intended to provide the desired user interface functions. Accordingly, in the embodiment of Figure 10 there is no need for the additional glass substrate layer 36a, the laminating material 36b or the thin-film conductive layer 34 which are otherwise shown in Figure 9 since the user interface information is provided merely by means of the graphic pattern that is provided from layer 44. The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. What is claimed is:

Claims

1. A capacitive touch screen comprising: a first thin-film conductive means for providing a grounded capacitor plate layer; a second thin-film conductive means for providing a patterned touch-sensitive capacitive layer; a first dielectric means for providing a continuous dielectric layer interposed between said first and second conductive means; and 0 a second dielectric means, formed over said second conductive means for providing an optically transparent layer having a substantial thickness which is equal to or greater than .005 inch. c . . . . 2. A capacitive touch screen as defined in claim 1 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

⁰ 3. A capacitive touch screen as defined in claim 1 wherein said first thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

5 4. A capacitive touch screen as defined in claim 1 wherein said second thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

⁰ 5. A capacitive touch screen as defined in claim 1 wherein said second thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

5 6. A capacitive touch screen as defined in claims 2 or 4 wherein each said layer is curved so that said touch screen is curved.

7. A capacitive touch screen as defined in claims 3 or 5 wherein each said layer is flat so that said touch screen is flat.

8. A capacitive touch screen as defined in claim 1 wherein said first dielectric means comprises a glass substrate layer onto which said grounded capacitor plate layer is formed on one side thereof, and onto which a lamination layer is formed on the other side thereof.

9. A capacitive touch screen as defined in claim 8 wherein said first dielectric means further comprises a second glass substrate layer and wherein said lamination layer is interposed between said glass substrate layers.

10. A capacitive touch screen as defined in claim 8 wherein said lamination layer is formed between said patterned touch-sensitive capacitive layer and said glass substrate.

11. A capacitive touch screen as defined in claim 8 wherein said glass substrate layer is on the order of about .062 of an inch thick, and said lamination layer is on the order of about .015 of an inch thick.

12. A capacitive touch screen as defined in claim 10 wherein said optically transparent layer comprises a second glass substrate layer. 13. A capacitive touch screen as defined in claim 12 wherein said second glass substrate layer is on the order of about .062 of an inch thick.

14. A capacitive touch screen as defined in claim 12 wherein said optically transparent layer further comprises a third thin-film conductive means for providing a layer patterned to provide touch-sensitive capacitive areas.

15. A capacitive touch screen as defined in claim 14 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

16. A capacitive touch screen as defined in claim 14 wherein said optically transparent layer further comprises a thin-film dielectric layer formed over said third thin- film conductive means.

17. A capacitive touch screen as defined in claim 16 wherein said thin-film dielectric layer is comprised of a material from the group of silicone dioxide and titanium oxide, and is on the order of from about 5,000 A to 10,000 A thick.

18. A capacitive touch screen as defined in claim 9 wherein each said glass substrate layer is on the order of about one eighth inch thick, and wherein said lamination layer is on the order of about .015 inch thick.

19. A capacitive touch screen as defined in claim 9 wherein said second dielectric means comprises a third glass layer and a second lamination layer interposed between said second thin-film conductive means and the third glass layer. 20. A capacitive touch screen as defined in claim 19 wherein said third glass layer is on the order of from about .062 of an inch to .090 of an inch thick, and wherein said second lamination layer is on the order of about .015 of an inch thick.

.0 21. A capacitive touch screen as defined in claim 1 wherein said first dielectric means comprises a glass substrate layer.

22. A capacitive touch screen as defined in claim 21

_D wherein said glass substrate layer is on the order of about .062 of an inch thick.

23. A capacitive touch screen as defined in claim 21 wherein said second dielectric layer comprises a second layer and a lamination layer interposed between said second

20 thin-film conductive means and the second glass layer.

24. A capacitive touch screen as defined in claim 23 wherein second glass layer is on the order of about .062 of an inch thick, and wherein said lamination layer is on the

25 order of about .015 of an inch thick.

25. A capacitive touch screen comprising: a first thin-film conductive means for providing a grounded capacitor plate layer;

30 a second thin-film conductive means for providing a patterned touch-sensitive capacitive layer; a first dielectric means for providing a continuous dielectric layer interposed between said first and second conductive means; and 5 a second dielectric means, formed over said second conductive means for providing an optically transparent layer which is thick enough and hard enough to protect said second conductive means from damage due to static electric discharge from a user and from damage due to surface wear and scratching.

26. A capacitive touch screen as defined in claim 25 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

27. A capacitive touch screen as defined in claim 25 wherein said first thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

28. A capacitive touch screen as defined in claim 25 wherein said second thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

29. A capacitive touch screen as defined in claim 25 wherein said second thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

30. A capacitive touch screen as defined in claims 26 or 28 wherein each said layer is curved so that said touch screen is curved.

31. A capacitive touch screen as defined in claims 27 or 29 wherein each said layer is flat so that said touch screen is flat.

32. A capacitive touch screen as defined in claim 25 wherein said first dielectric means comprises a glass substrate layer onto which grounded capacitor plate layer is formed on one side thereof, and onto which a lamination - layer is formed on the other side thereof.

33. A capacitive touch screen as defined in claim 32 wherein said first dielectric means further comprises a second glass substrate layer and wherein said lamination

-_₀ layer is interposed between said glass substrate layers.

34. A capacitive touch screen as defined in claim 32 wherein said lamination layer is formed between said patterned touch-sensitive capacitive layer and said glass

_ ___,_.— -< substrate.

35. A capacitive touch screen as defined in claim 32 wherein said glass substrate layer is on the order of about .062 of an inch thick, and said lamination layer is on the

20 order of about .015 of an inch thick.

36. A capacitive touch screen as defined in claim 34 wherein said optically transparent layer comprises a second glass substrate layer.

25

37. A capacitive touch screen as defined in claim 36 wherein said second glass substrate layer is on the order of about .062 of an inch thick.

38. A capacitive touch screen as defined in claim 36 0 wherein said optically transparent layer further comprises a third thin-film conductive means for providing a layer patterned to provide touch-sensitive capacitive areas.

39. A capacitive touch screen as defined in claim 38 5 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

40. A capacitive touch screen as defined in claim 38 wherein said optically transparent layer further comprises a thin-film dielectric layer formed over said third thin- film conductive means. 0

^• 41. A capacitive touch screen as defined in claim 40 wherein said thin-film dielectric layer is comprised of a material from the group of silicone dioxide and titanium oxide, and is on the order of from about 5,000 A to 10,000 5 A thick.

42. A capacitive touch screen as defined in claim 33 wherein each said glass substrate layer is on the order of about one eighth inch thick, and wherein said lamination layer is on the order of about .015 inch thick. 0

43. A capacitive touch screen as defined in claim 33 wherein said second dielectric means comprises a third glass layer and a second lamination layer interposed between said second thin-film conductive means and the 5 third glass layer.

44. A capacitive touch screen as defined in claim 43 wherein said third glass layer is on the order of from about .062 of an inch to .090 of an inch thick, and wherein

30 said second lamination layer is on the order of about .015 of an inch thick.

45. A capacitive touch screen as defined in claim 25 wherein said first dielectric means comprises a glass

J D substrate layer. 46. A capacitive touch screen as defined in claim 45 wherein said glass substrate layer is on the order of about .062 of an inch thick.

47. A capacitive touch screen as defined in claim 45 wherein said second dielectric layer comprises a second layer and a lamination layer interposed between said second thin-film conductive means and the second glass layer.

48. A capacitive touch screen as defined in claim 47 wherein second glass layer is on the order of about .062 of an inch thick, and wherein said lamination layer is on the order of about .015 of an inch thick.

49. A capacitive touch screen comprising: a first glass substrate layer having a thickness in the range of from about .030 of an inch to about .070 of an inch. a first thin-film indium tin oxide (ITO) layer uniformly deposited so as to form an essentially continuous conductive layer on one side of said first glass substrate layer which provides a grounded capacitor plate, said first thin-film ITO layer having a thickness of about 400 A; a second glass substrate layer having a thickness which is equal to or greater than about .005 of an inch; a second thin-film indium tin oxide layer patterned on one side of said second glass substrate layer so as to form a plurality of touch-sensitive capacitive areas, said second thin-film ITO layer having a thickness of about 400 A; and a layer of optically clear laminating material joining said second thin-film ITO layer to said first glass substrate layer. 50. A capacitive touch screen as defined in claim 49 wherein each said glass substrate layer is essentially the same thickness and the overall thickness of said screen is about one eighth of an inch.

51. A capacitive touch screen as defined in claim 49 wherein each said layer is curved so that said touch screen is curved.

52. A capacitive touch screen as defined in claim 49 further comprising a third thin-film layer of indium tin oxide patterned on a second side of said second glass substrate layer so as to form a plurality of touch- sensitive capacitive areas generally corresponding in size and shape to those of said second thin-film ITO layer, said third thin-film ITO layer having a thickness of about 400 A.

53. A capacitive touch screen as defined in claim 52 further comprising an optically clear dielectric layer formed over said third thin-film ITO layer.

54. A capacitive touch screen as defined in claim 53 wherein said thin-film dielectric layer is comprised of a material from the group of silicone dioxide and titanium oxide, and is on the order of from about 5,000 A to 10,000 A thick.

55. A capacitive touch screen comprising: a first glass substrate layer having a thickness in the range of from about .030 of an inch to about .070 of an inch; a first thin-film indium tin oxide (ITO) layer uniformly deposited so as to form a conductive layer on one side of said first glass substrate layer which provides a grounded capacitor plate, said first thin- = film ITO layer having a thickness of about 400 A; a second thin-film ITO layer patterned on a second side of said first glass substrate layer so as to form a plurality of touch-sensitive capacitive areas thereon, said second thin-film ITO layer having a

-_₀ thickness of about 400 A; a second glass substrate layer formed over said second thin-film ITO layer and having a thickness which is equal to or greater than about .005 of an inch; and a layer of optically clear laminating material joining said second glass substrate layer to said second thin-film ITO layer.

56. A capacitive touch screen as defined in claim 55 wherein each said glass substrate layer is essentially the

_ same thickness and the overall thickness of said screen is about one eighth of an inch.

57. A capacitive touch screen as defined in claim 55 wherein each said layer is curved so that said touch screen is curved. 5

58. A capacitive touch screen comprising: a first glass substrate layer having a thickness on the order of about one-eighth inch thick; a first thin-film tin oxide layer uniformly 0 deposited so as to form an essentially continuous conductive layer on one side of said first glass substrate layer so as to provide a grounded capacitor plate, said first thin-film tin oxide layer having a thickness in the range of from about 500 A to 5,000 A; 5 a second glass substrate layer having a thickness in the range of about one-eighth of an inch; a second thin-film tin oxide layer patterned on one side of said second glass substrate layer so as to form a plurality of touch-sensitive capacitive areas, said second thin-film ITO layer having a thickness in the range of from about 500 A to 5,000 A; a first layer of optically clear laminating material joining said first and second glass substrate 0 layers; a third glass layer formed over said second thin- film tin oxide layer and having a thickness in the range of from about .062 of an inch to .090 of an inch; and a second layer of optically clear laminating material joining said third glass layer to said second thin-film tin oxide layer.

59. A capacitive touch screen as defined in claim 58

20 wherein each said layer is flat so that said touch screen is flat.

60. A capacitive touch screen comprising: a first dielectric means for providing a continuous dielectric layer which serves as a back side

< O of said capacitive touch screen; a thin-film conductive means for providing a patterned touch-sensitive capacitive layer; and a second dielectric means, formed over said thin- film conductive means such that said thin-film

30 conductive means iε interposed between said first and second dielectric means, for providing an optically transparent layer at a user side of said capacitive touch screen, said optically tranεparent layer having a substantial thicknesε to protect said thin-film

35 conductive means from damage due to static electric discharge from the user and having sufficient hardness to protect said thin-film conductive eanε from damage due to surface wear and scratching.

61. A capacitive touch screen as defined in claim 1 wherein said second dielectric means has a thickness which is equal to or greater than .005 inch.

62. A capacitive touch screen aε defined in claim 60 further comprising a layer defining a graphic pattern formed onto a side of said first dielectric means which is oriented toward the back side of said capacitive touch screen.

0

io

0

5 [received by the International Bureau on 30 June 1992 (30.06.92); original claims 1-62 replaced by amended claims 1-62 (12 pages)]

1. A capacitive touch screen comprising: a first thin-film conductive means for providing continuous, non-patterned grounded capacitor plate layer; a second thin-film conductive means for providing a patterned touch-sensitive capacitive layer; a first dielectric means for providing a dielectric layer that extends from said first conducted means to the second conductive means; and a second dielectric means, formed over said . second conductive means for providing an optically transparent layer having a substantial thickness which is equal to or greater than .005 inch.

2. A capacitive touch screen as defined in claim 1 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

3. A capacitive touch screen as defined in claim 1 wherein said first thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

4. A capacitive touch screen as defined in claim 1 wherein said second thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

5. A capacitive touch screen as defined in claim 1 wherein said second thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

6. A capacitive touch screen as defined in claims 2 or 4 wherein each said layer is curved so that said touch screen is curved.

10. A capacitive touch screen as defined in claim 8 wherein said lamination layer is formed between said patterned touch-sensitive capacitive layer and said glass substrate layer.

12. A capacitive touch screen as defined in claim 10 wherein said optically transparent layer comprises a second glass substrate layer.

13. A capacitive touch screen as defined in claim 12 wherein said second glass substrate layer is on the order of about .062 of an inch thick.

18. A capacitive touch screen as defined in claim 9 wherein each said glasε substrate layer is on the order of about one eighth inch thick, and wherein said lamination layer is on the order of about .015 inch thick.

19. A capacitive touch screen as defined in claim 9 wherein said second dielectric means comprises a third glass layer and a second lamination layer interposed between said second thin-film conductive means and the third glass layer. 1

20. A capacitive touch screen as defined in claim 19 wherein said third glass layer is on the order of from about .062 of an inch to .090 of an inch thick, and wherein

_ said second lamination layer is on the order of about .015 5 of an inch thick.

21. A capacitive touch screen as defined in claim 1 wherein said first dielectric means comprises a glass substrate layer.

22. A capacitive touch screen as defined in claim 21 wherein said glass substrate layer is on the order of about .062 of an inch thick.

23. A capacitive touch screen as defined in claim 21 wherein said second dielectric layer comprises a second layer and a lamination layer interposed between said second thin-film conductive means and the second glass layer.

24. A capacitive touch screen as defined in claim 23 wherein second glass layer is on the order of about .062 of an inch thick, and wherein said lamination layer is on the order of about .015 of an inch thick.

25. A capacitive touch screen comprising: a first thin-film conductive means for providing continuous, non-patterned grounded capacitor plate layer; a second thin-film conductive means for providing a patterned touch-sensitive capacitive layer; a first dielectric means for providing a dielectric layer that extends from said first conductive means to the second conductive means; and a second dielectric means, formed over said second conductive means for providing an optically transparent layer which is thick enough and hard enough to protect said second conductive means from damage due to static electric discharge from a user and from damage due to surface wear and scratching.

27. A capacitive touch screen as defined in claim 25 wherein εaid first thin-film conductive means comprises a layer of tin oxide on the order of about 500 A to 5,000 A thick.

32. A capacitive touch screen as defined in claim 25 wherein said first dielectric means comprises a glasε substrate layer onto which grounded capacitor plate layer is formed on one side thereof, and onto which a lamination layer is formed on the other side thereof.

33. A capacitive touch screen as defined in claim 32 wherein said first dielectric means further comprises a second glass substrate layer and wherein said lamination layer is interposed between said glass substrate layers.

34. A capacitive touch screen as defined in claim 32 wherein said lamination layer is formed between said patterned touch-sensitive capacitive layer and said glass substrate layer.

35. A capacitive touch screen as defined in claim 32 wherein said glass substrate layer is on the order of about .062 of an inch thick, and said lamination layer is on the order of about .015 of an inch thick.

37. A capacitive touch screen as defined in claim 36 wherein said second glasε substrate layer is on the order of about .062 of an inch thick.

38. A capacitive touch screen as defined in claim 36 wherein said optically transparent layer further comprises a third thin-film conductive means for providing a layer patterned to provide touch-sensitive capacitive areas.

39. A capacitive touch screen as defined in claim 38 wherein said first thin-film conductive means comprises a layer of indium tin oxide on the order of about 400 A thick.

40. A capacitive touch screen as defined in claim 38 wherein said optically transparent layer further comprises a thin-film dielectric layer formed over said third thin- film conductive means.

41. A capacitive touch screen as defined in claim 40 wherein said thin-film dielectric layer is comprised of a material from the group of silicone dioxide and titanium oxide, and is on the order of from about 5,000 A to 10,000 A thick.

42. A capacitive touch screen as defined in claim 33 wherein each said glass substrate layer is on the order of about one eighth inch thick, and wherein said lamination layer is on the order of about .015 inch thick.

43. A capacitive touch screen as defined in claim 33 wherein said second dielectric means comprises a third glass layer and a second lamination layer interposed between said second thin-film conductive means and the third glass layer.

44. A capacitive touch screen as defined in claim 43 wherein said third glass layer is on the order of from about .062 of an inch to .090 of an inch thick, and wherein said second lamination layer is on the order of about .015 of an inch thick.

45. A capacitive touch screen as defined in claim 25 wherein said first dielectric means comprises a glass substrate layer.

46. A capacitive touch screen as defined in claim 45 wherein said glass substrate layer is on the order of about .062 of an inch thick.

49. A capacitive touch screen comprising: a first glass substrate layer having a thickness in the range of from about .030 of an inch to about .070 of an inch. a first thin-film indium tin oxide (ITO) layer uniformly deposited so as to form an essentially continuous, non-patterned conductive layer on one side of said first glass subεtrate layer which provides a grounded capacitor plate, said first thin-film ITO layer having a thickness of about 400 A; a second glass substrate layer having a thickness which is equal to or greater than about .005 of an inch; a second thin-film indium tin oxide layer patterned on one side of said second glasε substrate layer so as to form a plurality of touch-sensitive capacitive areas, said second thin-film ITO layer having a thickness of about 400 A; and a layer of optically clear laminating material joining said second thin-film ITO layer to said first glass substrate layer so that the first glass 1 substrate layer together with the layer of optically clear lamination material form a dielectric layer that extends from the second thin-film ITO layer to the _ first thin-film ITO layer.

50. A capacitive touch screen as defined in claim 49 wherein each said glass substrate layer is essentially the same thickness and the overall thickness of said screen is about one eighth of an inch.

52. A capacitive touch screen as defined in claim 49 further comprising a third thin-film layer of indium tin oxide patterned on a second side of said second glasε substrate layer so as to form a plurality of touch- sensitive capacitive areas generally corresponding in size and shape to those of said second thin-film ITO layer, said third thin-film ITO layer having a thickness of about 400 A.

54. A capacitive touch screen as defined in claim 53 wherein said thin-film dielectric layer is comprised of a material from the group of silicone dioxide and titanium oxide, and is on the order of from about 5,000 A to 10,000 A thick. 1

55. A capacitive touch screen comprising: a first glass substrate layer having a thickness in the range of from about .030 of an inch to about

5 _ .070 of an inch; a first thin-film indium tin oxide (ITO) layer uniformly deposited so as to form a conductive layer on one side of said first glass substrate layer which provides a grounded capacitor plate, said first thin-

■J film ITO layer having a thickness of about 400 A; a second thin-film ITO layer patterned on a second side of said first glass substrate layer so as to form a plurality of touch-sensitive capacitive areas thereon, said second thin-film ITO layer having

- a a thicknesε of about 400 A; a second glasε εubstrate layer formed over said second thin-film ITO layer and having a thickness which is equal to or greater than about .005 of an inch; and o ^a layer of optically clear laminating material joining said second glasε εubεtrate layer to said second thin-film ITO layer.

56. A capacitive touch screen as defined in claim 55 wherein each said glasε substrate layer is essentially the 5 same thickness and the overall thickness of said screen is about one eighth of an inch.

57. A capacitive touch screen as defined in claim 55 wherein each said layer is curved so that said touch screen 0 is curved.

58. A capacitive touch screen compriεing: a firεt glaεε substrate layer having a thickness on the order of about one-eighth inch thick; a first thin-film tin oxide layer uniformly deposited so as to form an esεentially continuouε conductive layer on one side of said first glasε substrate layer εo aε to provide a grounded capacitor plate, said first thin-film tin oxide layer having a thickness in the range of from about 500 A to 5,000 A; a second glasε εubεtrate layer having a thickneεε in the range of about one-eighth of an inch; a second thin-film tin oxide layer patterned on one side of said second glaεε substrate layer so as to form a plurality of touch-sensitive capacitive areas, said second thin-film ITO layer having a thickness in the range of from about 500 A to 5,000 A; a first layer of optically clear laminating material joining said first and second glass substrate layers; a third glasε layer formed over εaid εecond thin- film tin oxide layer and having a thickness in the range of from about .062 of an inch to .090 of an inch; and a second layer of optically clear laminating material joining said third glass layer to said second thin-film tin oxide layer.

59. A capacitive touch screen as defined in claim 58 wherein each said layer is flat so that said touch screen is flat.

60. A capacitive touch εcreen compriεing: a firεt dielectric means for providing a continuous dielectric layer which serves as a back side of said capacitive touch screen; a thin-film conductive means for providing a patterned touch-sensitive capacitive layer; and a εecond dielectric meanε, formed over said thin- film conductive means such that εaid thin-film conductive meanε iε interpoεed between said first and second dielectric means, for providing an optically transparent layer at a user side of εaid capacitive touch screen, said optically transparent layer having a substantial thickness to protect said thin-film conductive means from damage due to static electric discharge from the user and having sufficient hardnesε to protect said thin-film conductive means from damage due to surface wear and scratching.

61. A capacitive touch screen as defined in claim 1 wherein said second dielectric means haε a thickneεε which iε equal to or greater than .005 inch.

62. A capacitive touch εcreen aε defined in claim 60 further comprising a layer defining a graphic pattern formed onto a side of said first dielectric means which is oriented toward the back side of said capacitive touch screen.