WO1994005524A1

WO1994005524A1 - Defrostable-defoggable window and method of manufacture

Info

Publication number: WO1994005524A1
Application number: PCT/US1992/007503
Authority: WO
Inventors: Peyton W. Wofford; Ronald F. Steingrubey
Original assignee: Ristance Corporation
Priority date: 1992-09-03
Filing date: 1992-09-03
Publication date: 1994-03-17

Abstract

An improved flexible defrostable-defoggable rear window or backlight (12) for a convertible automobile (10) which has fewer components or elements and is simpler to manufacture whereby costs are reduced. Two transparent, flexible, bondable, non-conductive plastic sheets (30, 42) corresponding to the window outline are bonded together with a limited-area, continuous semi-conductive ink pattern (32) bonded therebetween for electrically heating the window (12). The semi-conductive ink pattern (32) is integrally formed and continuous and does away with bus bars and other non-heating elements in the see-through area. A chosen heat capacity and heat distribution pattern over the window (12) can be readily achieved by selection of appropriate design variables for the semi-conductive ink pattern (32) which can advantageously be applied by silk-screening techniques.

Description

DEFROSTABLE-DEFOGGABLE WINDOW AND METHOD OF MANUFACTURE

BACKGROUND OF THE INVENTION

Field of the Invention This invention generally relates to windows of automobiles which when obscured by frost or fog can be heated sufficiently to defrost and defog the surfaces and restore and maintain the transparency thereof, and to a method of manufacturing the same. More particularly, the present invention cures the deficiencies of, and otherwise improves upon, prior art systems for defrosting and defogging the flexible windows or backlights encountered in convertible automobiles.

Discussion of Prior Art

Rigid glass panels including the rear windows of automobiles which may be heated through a plurality of electrical members mounted within the panels have been successfully used for many years. This technology, however, has not lent itself to the requirements of convertible automobiles which require that the rear window be flexible. Flexibility is critical because when the rear window is in the raised position, appearance or styling criteria and/or aerodynamic considerations dictate that the window have a curved configuration. But when the window is stored in a retracted position, space considerations dictate that it lie flat.

Prior solutions to the requirements of convertible automobile backlights, as well as other background prior art, are disclosed or cited in U.S. Patent 4,883,940, issued November 28, 1989, entitled "Heatable Composite Backlight Panel", all of said prior art being incorporated herein by reference. In said U.S. Patent 4,883,940, the patentee provides a composite flexible window structure comprising a plurality of electrical members within a transparent plastic laminate forming the window. The electrical members, e.g., semi-conductive ink stripes, extend between an outwardly-disposed anode and an oppositely- disposed cathode which are connectable to a source of electrical energy such as the automobile battery. The anode and cathode are also referred to herein as bus bars.

When manufacturing the window and prior to lamination of the plastic sheets making up the window, the bus bars which comprise thin copper strips are disposed on the inner surface of one of the lamina so as to form the anode and cathode for the heating system. Conductive inks are then silk screened between the bus bars so as to form the actual heating element. To ensure proper electrical connection between the silk screened heating elements and the bus bars, short copper strips are apparently applied between the extremities of the silk screened ink pattern and the bus bars and the conductive members are crimped, all prior to the lamination of the panel.

Manifestly, care must be taken to assure the integrity of the heating elements, the bus bars and the like, thereby raising the complexity and cost of manufacture and the need for increased quality control. The presence of the bus bars decreases window transparency by decreasing the see-through area without providing any offsetting function other than providing a conduit for the electrical energy. Moreover, since the bus bars are not heating elements, there are no continuous lateral limitations to the defrosted-defogged area, sometimes causing, at least initially, excessive irregularities in the see-through area which are undesired both functionally and aesthetically. Another potential shortcoming of the aforementioned prior-art design is the possibility of electrical discontinuity developing between the silk- screened semi-conductive ink and the copper strip bus bars. This problem of maintaining continuity between disparate materials can become acute over a period of time particularly in view of the repeated flexure of the convertible window as the automobile top is repeatedly raised and lowered. The use of disparate materials for the semi- conductive strips and the bus bars may also present an appearance problem. Both elements are visible within the laminated window and any differences in the appearance of each can be aesthetically disruptive. These and other shortcomings of prior art systems have inhibited the adoption of heated backlights in convertible automobiles.

OBJECTS OF THE INVENTION It is therefor a general object of the present invention to cope with such shortcomings of the prior art.

It is another object to provide a flexible defrostable-defoggable rear window or backlight for a convertible automobile which has fewer components or elements whereby costs are reduced.

It is still another object to provide a heatable, flexible backlight having less potential for hot spot formation or other failure and a longer useable life.

It is still another object to provide a flexible, defrostable-defoggable backlight wherein the opaque elements in the backlight occupy less area for a given heating capacity and thus greater see-through area, or more heating capacity for a given opaque area. It is still another object to provide a defrostable-defoggable window for a vehicle having both longitudinal and end-defining lateral heating elements, all interconnected, wherein substantially all visible components thereof perform a heating function when energized and all such components can be integrally formed in a single manufacturing step.

It is still another object to provide a flexible heated backlight of improved quality at lower costs.

It is a further object to provide a heatable, flexible backlight wherein the components of the heating system which are visible within the window have substantially the same composition and appearance and are protected on both sides by the overlying transparent laminae.

It is a further object to provide a simpler method of manufacturing heatable flexible rear windows for convertible automobiles and thus lower the cost thereof.

It is a still further object to provide a method of manufacturing heatable flexible windows wherein the heat distribution characteristics of the window may be preselected by simple adjustments in manufacturing variables.

These and other objects of the present invention will become apparent from the description hereinafter set forth.

SUMMARY OF THE INVENTION

These objects are achieved by a flexible, defrostable-defoggable window laminate which is similar to prior art assemblies but differs therefrom in critical respects. As with the prior art structures, the window comprises a first transparent, flexible, bondable, non- conductive plastic sheet corresponding substantially to the dimensions of the window outline and having electrical insulating properties; a second transparent, flexible, bondable, non-conductive plastic sheet disposed adjacent and in registry with the first plastic sheet, also corresponding substantially to the dimensions of the window and having electrical-insulating properties; and a limited area, integrally formed, semi-conductive ink pattern disposed between said first and second bondable plastic sheets for heating the same. As with the prior art structures, the inner adjacent surfaces of the first and second plastic sheets are bonded together and to the intervening integrally- formed, semi-conductive ink pattern. This results in a substantially-integral composite sheet with the semi- conductive ink pattern being bonded internally to the first and second plastic sheets and having thermally- conductive paths to the outer surfaces of the sheets. The semi-conductive heat pattern is designed to provide a substantially uniform heat distribution over the window surfaces without hot spot formation when the pattern is electrically energized.

The significant difference and improvement over prior art assemblies lies in part in the specific makeup of the embedded heating element, that is, the semi- conductive ink pattern which normally covers and renders opaque only a small or minor proportion of the total area of the window, e.g., less than about 20%, so as not to materially interfere with the transparency or see-through capability thereof, an important consideration for obvious reasons. In the present invention, the assembly employs an integrally-formed continuous semi-conductive ink pattern between the terminals of a controlled external source of electrical energy, e.g., the car battery, associated cables, wires or equivalent electrical conductors and usual intervening controls, switches and connectors. The ink pattern comprises a plurality of elongated, relatively-narrow, spaced, semi-conductive ink stripes between, and integrally formed with, respective semi-conductive end-connecting traces of enlarged cross- sectional area laterally-disposed adjacent the outer extremities of the window. The composition, size, location, spacing and heating capacities of the stripes and respective end-connecting lateral traces are selected to achieve the desired defrosting-defogging capability of the window.

In contrast to the continuous, integrally- formed, semi-conductive ink pattern of the present invention, the prior art assembly, as already indicated, embeds a multiple component discontinuous-heating structure, including the semi-conductive ink stripes and the copper strips or bus bars functioning as an anode and cathode, which are connected to an external power source. Any partial or total disruption in the electrical continuity at the junctures of the ink stripes and bus bars can lead to hot spot formation or heating failure. The semi-conductive ink pattern of the present invention does away with the bus bars and integrally forms the entire structure, all of which performs a heating function when energized. As a result, the manufacturing process is substantially simplified, fewer parts are involved, costs are lowered, the potential for failure, including hot- spot formation, lessened and a longer useable life made potentially possible. Moreover, since the entire visible embedded structure of the present invention is integrally formed from the same material, it is aesthetically less disruptive than the combination of heating elements and bus bars of the prior art. Furthermore, since substantially the entire embedded structure of the present invention functions as an integrally-formed heating element, less window area need be blocked as compared with the prior art structure employing bus bars having no significant heating function.

It should be recognized, of course, that the optimum heat distribution over the window may not necessarily be a uniform distribution. More or less heat may be required in some areas than in others depending upon differences in anticipated frost or fog accumulations. Thus, for example, when the vehicle is parked, ice and snow tend to accumulate at the lower portion of the rear window where the substantially vertical window-area and substantially horizontal tail or trunk area intersect. This situation may dictate a higher heat distribution at the lower portion of the window area. Other factors may also influence the optimum heat distribution including, for example, rising convection air currents in contact with the window on the inside or outside, a desire for initial clarity at the mid-portion area of the window, and the like. The window and method of manufacture of the present invention lend themselves to providing the design flexibility to meet the perceived needs at minimal cost, as will be apparent hereinafter.

As those skilled in the art will recognize, the width of the respective end-connecting lateral traces of the window of the present invention will normally be a substantial multiple, e.g., 5-50 times, preferably 8 to 30 times the width of each of the plurality of individual, spaced ink stripes therebetween, whereby to adjust the heat distribution pattern over the respective surfaces to be defrosted and defogged. This is manifest from the fact that the composition of the entire conductive ink pattern is substantially uniform throughout, whereby the resistivity in ohms per square per mil is also substantially uniform. The width of the ink stripes can also be varied from one another to achieve desired heat distribution, whether it be uniform or otherwise. The width of individual ink stripes or end-connecting traces can also be varied from end-to-end or center-to-ends, or the like, to achieve desired heating characteristics or patterns. Additional design flexibility is also present by, for example, varying the spacing between adjacent ink stripes.

Still another flexibility in heat distribution is provided by the ability to connect the source of electrical energy at any preselected point on the respective semi-conductive, end-connecting lateral traces. The effect of the connection point will be apparent from the detailed description of several alternative embodiments. In view of the availability of various means for adjusting heating capacity and heat distribution, as above indicated, the thickness and composition of the ink pattern can be substantially constant. Thus, the entire ink pattern, including the variations above set forth, can be applied by silk screening techniques in a single pass as those skilled in that art will recognize. The resulting greatly-simplified manufacturing process reduces the cost and results in a superior product.

In addition or alternatively, the thickness of the ink pattern can be adjusted uniformly or selectively, e.g., increasing the thickness of the end-connecting traces relative to the ink stripes, varying the thicknesses of the ink stripes from one area to another, or the like. Such alternatives, however, may involve multiple silk screening passes and thus additional manufacturing cost, typically less, however, than prior art alternatives.

As is apparent from the above description, the heat distribution over the window surface may be preselected by tailoring the manufacturing process to the size and configuration of the window and the defrosting- defogging load for which the system is being designed. As already indicated, such tailoring would take into consideration the number, length, location and spacing of the ink stripes, the size and pattern of both the ink stripes and end-connecting lateral ink traces, the composition and resulting resistivity thereof, the widths and thicknesses thereof, the point of connecting the electrical source to the lateral end-connecting ink traces, and the like, whereby to achieve the desired heating characteristics with the available electrical sources, typically the battery-based electrical system of the modern automobile. Such parameters must be chosen with the overriding requirements in mind that the resulting window be acceptable from transparency, flexibility and aesthetic or appearance standpoints.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be more clearly understood from the following detailed description of a specific and preferred embodiment read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of one embodiment of the defrostable-defoggable window of the present invention as employed as a backlight in a convertible automobile;

FIG. 2 is an elevation view of the embodiment of the defrostable-defoggable window of FIG. 1, on an enlarged scale, a portion of the upper plastic sheet being broken away for illustrative purposes, the embodiment having the integrally-formed extensions at the lower extremities of the end-connecting traces for connection to the electrical system of the automobile;

FIGS. 3 and 4 are fragmentary views similar to FIG. 2 except that the extensions for connections to the electrical system are at diagonally-opposed and intermediate locations, respectively; and FIGS. 5-7 are electrical schematics roughly corresponding to the embodiments of FIGS. 2-4, respectively, illustrating the approximate heat distribution patterns corresponding thereto. It should be understood that the drawings are not necessarily to scale and that certain aspects of the described embodiments are included to provide the environment for the invention or are illustrated by graphic symbols, schematic representations and fragmentary views. Thus, for example, the automobile itself, the electrical system thereof, and the overall size and shape of the heated window are not per se part of the invention. Accordingly, they are simply represented, including schematic representations and fragmentary views.

It should be recognized that certain verbiage as used herein should be construed in the light of the disclosure. Thus, for example, the terms "longitudinal" and "longitudinally-disposed" as used in connection with the semi-conductive ink stripes refer to the substantially-horizontal (albeit curved) elongated disposition thereof within the window, and the terms "lateral" and "laterally-disposed" as used in connection with the shorter semi-conductive end-connecting lateral traces refer to the substantially-vertical disposition thereof. The terms "left", "right", "upper", "lower", "top" or "bottom" should be construed with reference to the drawings. Similarly, for example, "non-conductive" and "semi-conductive" as used herein refer to electrical characteristics well known to those skilled in the art. Likewise, "defrost-defog" and counterpart adjectives thereof would also encompass "deice-de ist" and counterparts thereof, and the like. Accordingly, language should be liberally construed within the context of the invention. It should also be recognized that actual embodiments of the defrostable-defoggable window of the present invention may differ substantially, depending in part upon the particular convertible automobile for,which the window is designed. Such detail is considered well within the comprehension of those skilled in the art in the light of the present disclosure and without further amplification. It should be understood, of course, that the invention is not limited to the particular embodiments illustrated..

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, convertible automobile 10 has a rear window or backlight 12 which is defrostable and defoggable in accordance with the practice of the present invention. The electrical source for energizing the window is automotive battery 14 and the automotive electrical generator or alternator normally associated therewith (not shown) . Typically, automotive batteries are 12-volt units, with slightly-higher voltages usually being available because of the generator/alternator, an average value of 13 volts being used herein for design calculations. The electrical energy is supplied via schematically-presented leads 16 and 18 and on-off control switch 20 customarily located on the dash panel within convenient reach of the driver.

Referring to FIG. 2, the defrostable-defoggable window 12 comprises a first transparent flexible bondable plastic sheet 30. In actual size, it corresponds substantially to the dimensions of the window outline except for (a) small additional marginal areas needed for attachment to the convertible roof portion of automobile 10, and (b) means for connecting the semi-conductive ink pattern 32 to battery 14 via leads 16 and 18, as hereinafter discussed. Window-attachment means per se are not part of the present invention and are well known to those skilled in that field.

The shape or outline of window 12 and the ink pattern 32 are illustrative only and depend upon the particular convertible automobile, the design requirements thereof and dictates of the manufacturer. The present invention is not limited to any particular automobile window or ink pattern.

The limited-area, integrally-formed, semi- conductive ink pattern 32 is deposited on plastic sheet 30 by techniques known to those skilled in the art. For a source of the semi-conductive ink advantageously employed for pattern 32 and the silk screening of same on plastic sheet 30, applicants¹ assignee herein has relied upon Poly-Flex Circuits, Inc., 28 Kenney Drive, Cranston, Rhode Island 02920, with very successful results.

Integrally-formed, semi-conductive ink pattern 32 comprises a plurality of elongated, relatively-narrow, spaced semi-conductive ink stripes 34, which are between, and integrally-formed with, semi-conductive, end- connecting lateral ink traces 36 of enlarged cross- sectional area. As shown, integrally-formed lateral ink traces 36 are disposed adjacent the outer (left and right) extremities of ink stripes 34 and form part of the same heating circuit. As already indicated, the composition, size, location, spacing, pattern and heating capacity of the ink stripes 34 and end-connecting ink traces 36 are selected to achieve the desired defrosting- defogging capability of the window, as further set forth hereinafter.

In the embodiment of FIG. 2, both the first plastic sheet 30 and ink pattern 32 have lower semi- conductive ink extensions 38L and 40L, respectively, on the lower left side of FIG. 2, and 38R and 40R, respectively, on the lower right side of FIG. 2. The areas of ink extensions 40L and 4OR are broadened as compared with ink traces 36, e.g., about 2 to 3 times the width, so as to decrease the electrical resistance thereof and correspondingly reduce the heating capacity thereof. This reflects the fact that the extensions are not exposed and normally would need no defrosting and defogging capability. The larger area also assures good electrical contact with the source. The extensions are preferably integrally-formed with pattern 32 and are formed as part thereof during the same silk screening step, again simplifying manufacture.

As already apparent from FIG. 1, these extensions are the means by which the heating pattern 32 of window 12 is connectable to battery 14 via leads 16 and 18 and switch 20. The actual means of connection are matters of choice. An advantageous means, which can be adopted for use with the window of the present invention, is set forth by the same applicants' in their U.S. Patent Application Serial No. 07/784,762, filed October 30, 1991, presently pending. In accordance with the present invention, a second transparent, flexible bondable plastic sheet 42, substantially identical to first plastic sheet 30, overlies and is laminated to first plastic sheet 30 and the semi-conductive ink pattern 32 thereon. As a result, first and second plastic sheets 30 and 42 are bonded to each other and to the intervening ink pattern 32 whereby a substantially-integral composite sheet is formed with ink pattern 32 being bonded internally to both first and second plastic sheets 30 and 42. It should be noted that in the embodiment of

FIG. 2 the lower left and right extensions of overlying second plastic sheet 42 are not as long as extensions 38L and 40L or 38R and 40R, respectively. Thus, for example, the extensions of second plastic sheet 42 may be 0.5" to 1.5" shorter, typically 1" shorter. As a result, at least one surface of each of ink pattern extensions 40L and 4OR remains exposed to facilitate the electrical connection thereto, as those skilled in the art will recognize. The shorter extension of second plastic sheet 42 is indicated at the left side of FIG. 2 by edge 42'. The embodiments shown by the fragmentary views of FIGs. 3 and 4 are substantially the same as the embodiment of FIG. 2 except that the extensions for connecting the respective windows to the source of electrical energy have been relocated. In the case of FIG. 3, the right hand connection remains as in FIG. 2, but the left hand connection is disposed at the top or upper portion of the ink pattern rather than at the bottom or lower portion. In the embodiment of FIG. 4, both the left hand and the right hand extensions are at approximately the left hand and right hand mid-points of the end-connecting traces 36 of ink pattern 32, respectively.

Other points of connection may be chosen and the present invention is not limited to those illustrated. The particular point selected will effect the heat pattern, as will be recognized by those skilled in the art and as set forth hereinafter. The location of the connection may be chosen for such optimization of the heat pattern and/or to accommodate the optimum location of the electrical leads and connectors within the particular automobile body and convertible roof. The particular plastic and particular conductive inks for window 12 are not per se part of the present invention. In a preferred embodiment, both first plastic sheet 30 and second plastic sheet 42 are 0.02" thick sheets of a suitable grade of polyvinyl chloride (PVC) . After the semi-conductive ink pattern 32 is silk screened on the surface of first plastic sheet, the lamination of the first and second plastic sheets may be carried out by known techniques. In a preferred method, sheets 30 and 42 are pressed together between two highly- polished steel plates at elevated temperature and pressure, e.g., at least 180° F and at least 200 psi for at least about two minutes, as previously described in the aforementioned U.S. Patent 4,883,940. When properly processed the two PVC sheets 30 and 42, which prior to processing are opaque, become fused to semi-conductive ink pattern 32 and to each other and become clear. For such purposes, applicants' assignee herein has relied upon Regalite Plastics Corporation, 300 Needham Street, Newton Falls, Massachusetts 02164, and Ellay Incorporated, 6900 Elm Street, City of Commerce, California 90040, with successful results.

In a particular embodiment of the present invention, the semi-conductive ink employed for the silk screening step may be that available from the aforementioned Poly-Flex Circuits, Inc., and identified as its PF002 silver conductive ink, and equivalents. It is a highly flexible ink comprising a silver-filled composition in a polymer blend of vinyl and urethane. The resulting ink pattern typically has a resistivity of about 0.0075 ohms/square/mil, although, manifestly, other resistivities may be employed commensurate with the desired heating results.

FIG. 5 represents an electrical schematic roughly corresponding to the defrostable-defoggable window 12 of FIG. 2, the same reference numerals 32, 34 and 36 being used for the electrical counterparts of the semi-conductive ink pattern, ink stripes and ink traces, respectively. For simplicity, however, the length of each of the ink stripes 34 is assumed to be the same and the heating capacity of the semi-conductive extensions. For purposes of calculation, the following variables were chosen, the values being approximate: Voltage 13 Volts

Thickness of Ink Pattern 1 mil Resistance per Stripe (Avg.) 18 Ohms Number of Stripes 15 Length of Stripes (Avg.) 900 mm Width of Stripes 0.5 mm Length of End Traces 300 mm Width of End Traces 11.1 mm Resistance of End Traces 0.27 Ohm Resistivity of Ink 0.01 Ohms per square per mil

The approximate total heat output of about 121 watts for the window embodiment of FIG. 5 is representative of typical treating requirements, which may range from about 50 watts to about 170 watts, but are not limited thereto. The present invention lends itself to meeting such other requirements by adjustment of the various variables, as those skilled in the art will readily recognize.

As shown in FIG. 5, the heat distribution from the window embodiment of FIG. 2 is concentrated at the lower portion of the window, e.g., about 8.82 watts at the lowest stripe and about 1.56 watts at each of the two lowest segments of the ink traces. This contrasts with about 5.85 watts at the highest stripe and about 0.006 watts at each of the highest trace portions. It should be recognized that because of certain simplifying assumptions for ease of calculation, calculated heat values are approximate but do reflect the correct heat distribution pattern.

As shown in FIG. 6, where the electrical energy is connected at diagonally opposed locations, the total heat output is about the same, i.e., about 121 watts, but the heat distribution is substantially changed. It is highest in the outermost stripes 34 and lowest in the center stripes, albeit not substantially. In the lateral traces 36, the heat distribution is the reversal of each other, as shown.

As shown in FIG. 7, the total heat output is about 132 watts, and the heat distribution is again altered. More of it is concentrated in the stripes and, unlike the embodiment of FIG. 6, the center stripe has the highest output and the outer (upmost and lowermost) stripes the lowest. In the lateral ink traces 36, like the ink stripes, the heat distribution is highest at the center.

The heat patterns of FIGS. 5, 6 and 7 can be shifted by altering the various other variables already discussed, as will be apparent to those skilled in the art. This versatility is achievable within the context of a simplified manufacturing process or method using silk screening techniques.

As is apparent from the above description, the defrostable-defoggable vehicle window of the present invention overcomes shortcomings of the prior art and otherwise achieves the various objects of the present invention as previously set forth.

It is to be understood that allowed claims based on this disclosure are to be accorded a range of equivalents commensurate in scope with the advance made over the prior art.

Claims

Having described the invention, what is claimed is:

1. A defrostable-defoggable window for a vehicle comprising: (a) a first transparent, flexible, bondable, non-conductive plastic sheet corresponding substantially to the dimensions of the window outline and having electrical-insulating properties;

(b) a second transparent, flexible, bondable, non-conductive plastic sheet disposed adjacent and in registry with said first plastic sheet, also corresponding substantially to the dimensions of the window outline and having electrical-insulating properties; (c) a limited-area, integrally-formed, semi-conductive ink pattern disposed between said first and second bondable plastic sheets for heating same;

(d) the inner adjacent surfaces of said first and said second plastic sheets being bonded to each other and to the intervening integrally-formed, semi- conductive ink pattern whereby a substantially-integral composite sheet is formed with said semi-conductive ink pattern being bonded internally to the first and second plastic sheets so as to provide a predetermined heat distribution over the respective surfaces of the window when the pattern is electrically energized;

(e) said semi-conductive ink pattern covering only a minor proportion of the total area of the resulting substantially-integral composite sheet so as not to materially interfere with the transparency thereof and being disposed as a plurality of elongated, relatively-narrow, spaced, semi-conductive ink stripes between, and integrally-formed with, respective semi- conductive end-connecting traces of enlarged cross- sectional area laterally-disposed adjacent the outer extremities of the window, the composition, size, location and heating capacity of the semi-conductive ink stripes and respective integrally-formed, semi-conductive end-connecting traces being selected to achieve the predetermined defrosting-defogging capability of the window employing the available electrical-energy source;

(f) each of said respective integrally- formed, semi-conductive, end-connecting traces being electrically connectable to a controlled external source of electrical energy, whereby upon activation thereof a continuous electrical heating path is provided by said end-connecting traces and said ink stripes therebetween.

2. The defrostable-defoggable window of claim 1 wherein the composition of said electrically-semi- conductive ink pattern is substantially uniform throughout said end-connecting traces and said ink stripes therebetween.

3. The defrostable-defoggable window of claim 1 wherein the resistivity of said semi-conductive ink pattern in ohms per square per mil is substantially uniform throughout said end-connecting traces and said ink stripes therebetween.

4. The defrostable-defoggable window of claim 1 including an integrally-formed, semi-conductive extension of an extremity of each of said end-connecting traces to the periphery of said window where exposed portions of each are connected to the respective leads of an electrical energy source.

5. The defrostable-defoggable window of claim 4 wherein the respective extensions are at the lower extremities of said end-connecting traces.

6. The defrostable-defoggable window of claim 4 wherein the respective extensions are at the upper extremities of said end-connecting traces.

7. The defrostable-defoggable window of claim 4 wherein said respective extensions are at diagonally opposed extremities of said end-connecting traces. 8. The defrostable-defoggable window of claim 1 wherein said end connecting traces are electrically connectable to said controlled external source of energy at a location intermediate the extremities of each. 9. The defrostable-defoggable window of claim

1 wherein the cross-sectional width of said respective semi-conductive end-connecting traces is about 5 to 50 times the width of said semi-conductive ink stripes.

10. The defrostable-defoggable window of claim 1 wherein the thickness of said semi-conductive ink stripes and said semi-conductive end-connecting traces are substantially the same.

11. The defrostable-defoggable window of claim 1 wherein said ink stripes are substantially evenly spaced from one another.

12. The defrostable-defoggable window of claim 1 wherein said semi-conductive ink pattern covers less than about 20% of the total area of the window.

13. A defrostable-defoggable window for a vehicle comprising:

(a) a first transparent, flexible, bondable plastic sheet corresponding substantially to the dimensions of the window outline and having electrical- insulating properties; (b) a second transparent, flexible, bondable plastic sheet disposed adjacent and in registry with said first plastic sheet, also corresponding substantially to the dimensions of the window outline and having electrical-insulating properties; (c) a limited-area, integrally-formed, semi-conductive ink pattern disposed between said first and second bondable plastic sheets for heating same;

(e) said semi-conductive ink pattern covering only a minor proportion of the total area of the resulting substantially-integral composite sheet so as not to materially interfere with the transparency thereof and being disposed as a plurality of elongated, relatively-narrow, substantially-evenly-spaced, semi- conductive ink stripes between, and integrally-formed with, respective semi-conductive end-connecting traces of enlarged cross-sectional area adjacent the outer extremities of the window, the composition, size, location and heating capacity of the semi-conductive ink stripes and respective integrally-formed, semi-conductive end-connecting traces being selected to achieve the predetermined defrosting-defogging capability of the window employing the available electrical-energy source, the composition and thickness of the integrally-formed ink stripes and end-connecting traces being substantially uniform throughout;

(f) each of said respective integrally- formed, semi-conductive, end-connecting traces being electrically connectable to a controlled external source of electrical energy, whereby upon activation thereof a continuous electrical heating path is provided by said end-connecting traces and said ink stripes therebetween. 14. A method of making a flexible, defrostable-defoggable window for a vehicle comprising:

(a) providing a first transparent, flexible, bondable plastic sheet corresponding substantially to the dimensions of the window and having electrical insulating properties; (b) silk screening a limited area, integrally-formed, semi-conductive ink pattern on one side of a first plastic sheet, said semi-conductive pattern being disposed as a plurality of elongated, relatively-narrow, spaced, semi-conductive ink stripes between, and integrally-formed with, respective semi- conductive end-connecting traces of enlarged cross- sectional area adjacent the outer ends of the ink stripes, the composition, size, location, spacing, pattern and heating capacity of the stripes and respective end-connecting ink traces being selected to achieve the desired defrosting-defogging capability of the window using an available electrical energy source;

(c) laminating a second transparent, flexible, bondable plastic sheet, substantially identical to said first plastic sheet, to said one side of said first plastic sheet whereby said first and second plastic sheets are bonded to each other and to the intervening integrally-formed, semi-conductive ink pattern whereby a substantially integral composite sheet is formed with said electrically-semi-conductive ink pattern being bonded internally to the first and second plastic sheet;

(d) providing integrally-formed means to connect said semi-conductive end-connecting traces to said available electrical energy source, whereby upon activation thereof said integrally-formed, electrically- semi-conductive ink pattern is heated throughout its length so as to defrost and defog said window.

15. The method of claim 14 wherein the semi- conductive ink pattern silk screened on said first plastic sheet is substantially uniform in composition and thickness throughout the pattern. AMENDED CLAIMS

[received by the International Bureau on 30 April 1993 (30.04.93), original claims 1,2 and 14 amended; other claims unchanged (5 pages)]

1. (Amended) A defrostable-defoggable window for a vehicle comprising:

(a) a first transparent, bondable, non-conductive sheet corresponding substantially to the dimensions of the window outline and having electrical-insulating properties;

(b) a second transparent, bondable, non- conductive sheet disposed adjacent and in registry with said first sheet, also corresponding substantially to the dimensions of the window outline and having electrical-insulating properties;

(c) a limited-area, integrally-formed, semi- conductive ink pattern disposed between said first and second bondable sheets for heating same;

(d) the inner adjacent surfaces of said first and said second sheets being bonded to each other and to the intervening integrally-formed, semi-conductive ink pattern whereby a substantially-integral composite sheet is formed with said semi-conductive ink pattern being bonded internally to the first and second sheets so as to provide a predetermined heat distribution over the respective surfaces of the window when the pattern is electrically energized;

(e) said semi-conductive ink pattern covering only a minor proportion of the total area of the resulting substantially-integral composite sheet so as not to materially interfere with the transparency thereof and being disposed as a plurality of elongated, relatively-narrow, spaced, semi- conductive ink stripes between, and integrally-formed with, respective semi-conductive end-connecting traces of enlarged cross-sectional area disposed adjacent outer extremities of th window, the composition, size, location and heating capacity o the semi-conductive ink stripes and respective integrally-formed, semi-conductive end-connecting traces being selected to achiev the predetermined defrosting-defogging capability of the windo employing the available electrical-energy source;

(f) each of said respective integrally-formed, semi-conductive, end-connecting traces being electricall connectable to a controlled external source of electrical energy, whereby upon activation thereof a continuous electrical heatin path is provided by said end-connecting traces and said in stripes therebetween.

2. (Amended) The defrostable-defoggable window o claim 1 wherein said first and said second transparent, bondable, non-conductive sheets comprise flexible plastic and th composition of said electrically-semi-conductive ink pattern i substantially uniform throughout said end-connecting traces an said ink stripes therebetween.

3. The defrostable-defoggable window of claim wherein the resistivity of said semi-conductive ink pattern i ohms per square per mil is substantially uniform throughout sai end-connecting traces and said ink stripes therebetween.

4. The defrostable-defoggable window of claim including an integrally-formed, semi-conductive extension of a extremity of each of said end-connecting traces to the peripher of said window where exposed portions of each are connected t the respective leads of an electrical energy source.

5. The defrostable-defoggable window of claim wherein the respective extensions are at the lower extremities o said end-connecting traces.

6. The defrostable-defoggable window of claim wherein the respective extensions are at the upper extremities o said end-connecting traces.

7. The defrostable-defoggable window of claim wherein said respective extensions are at diagonally oppose extremities of said end-connecting traces.

8. The defrostable-defoggable window of claim wherein said end connecting traces are electrically connectabl to said controlled external source of energy at a locatio intermediate the extremities of each.

9. The defrostable-defoggable window of claim wherein the cross-sectional width of said respective semi conductive end-connecting traces is about 5 to 50 times the widt of said semi-conductive ink stripes.

10. The defrostable-defoggable window of claim wherein the thickness of said semi-conductive ink stripes an said semi-conductive end-connecting traces are substantially th same.

11. The defrostable-defoggable window of claim wherein said ink stripes are substantially evenly spaced from on another.

12. The defrostable-defoggable window of claim wherein said semi-conductive ink pattern covers less than abou 20% of the total area of the window.

13. A defrostable-defoggable window for a vehicl comprising:

(a) a first transparent, flexible, bondabl plastic sheet corresponding substantially to the dimensions o the window outline and having electrical-insulating properties;

(b) a second transparent, flexible, bondabl plastic sheet disposed adjacent and in registry with said firs plastic sheet, also corresponding substantially to the dimension of the window outline and having electrical-insulatin properties;

(c) a limited-area, integrally-formed, semi conductive ink pattern disposed between said first and secon bondable plastic sheets for heating same;

(d) the inner adjacent surfaces of said first an said second plastic sheets being bonded to each other and to th intervening integrally-formed, semi-conductive ink patter whereby a substantially-integral composite sheet is formed wit said semi-conductive ink pattern being bonded internally to th first and second plastic sheets so as to provide a predetermine heat distribution over the respective surfaces of the window whe the pattern is electrically energized;

(e) said semi-conductive ink pattern coverin only a minor proportion of the total area of the resultin substantially-integral composite sheet so as not to materiall interfere with the transparency thereof and being disposed as plurality of elongated, relatively-narrow, substantially-evenly spaced, semi-conductive ink stripes between, and integrally formed with, respective semi-conductive end-connecting traces o enlarged cross-sectional area adjacent the outer extremities o the window, the composition, size, location and heating capacit of the semi-conductive ink stripes and respective integrally- formed, semi-conductive end-connecting traces being selected t achieve the predetermined defrosting-defogging capability of the window employing the available electrical-energy source, th composition and thickness of the integrally-formed ink stripes and end-connecting traces being substantially uniform throughout;

(f) each of said respective integrally-formed, semi-conductive, end-connecting traces being electrically connectable to a controlled external source of electrical energy, whereby upon activation thereof a continuous electrical heatin path is provided by said end-connecting traces and said in stripes therebetween.

14. (Amended) A method of making a defrostable- defoggable window for a vehicle comprising:

(a) providing a first transparent, bondable sheet corresponding substantially to the dimensions of the window an having electrical insulating properties;

(b) silk screening a limited area, integrally- formed, semi-conductive ink pattern on one side of a first sheet, said semi-conductive pattern being disposed as a plurality o elongated, relatively-narrow, spaced, semi-conductive ink stripes between, and integrally-formed with, respective semi-conductiv end-connecting traces of enlarged cross-sectional area adjacen the outer ends of the ink stripes, the composition, size, location, spacing, pattern and heating capacity of the stripe and respective end-connecting ink traces being selected t achieve the desired defrosting-defogging capability of the windo using an available electrical energy source;

(c) laminating a second transparent, bondabl sheet, substantially identical to said first sheet, to said on side of said first sheet whereby said first and second sheets ar bonded to each other and to the intervening integrally-formed, semi-conductive ink pattern whereby a substantially integra composite sheet is formed with said electrically-semi-conductiv ink pattern being bonded internally to the first and secon sheet;

(d) providing integrally-formed means to connect said semi-conductive end-connecting traces to said availabl electrical energy source, whereby upon activation thereof sai integrally-formed, electrically-semi-conductive ink pattern is heated throughout its length so as to defrost and defog said window.

15. The method of claim 14 wherein the semi-conductive ink pattern silk screened on said first plastic sheet is substantially uniform in composition and thickness throughout the pattern.

STATEMENT UNDER VRTICLE19

The claims (i.e., claims 1-15) remain substantially as before. Claims 1, 2 and 14, however, have been amended herewith to avoid an unnecessary limitation and also to obviate a narrow interpretation which might unnecessarily be read into the claims. The scope of the amended claims is believed to be consistent with the patent documents cited in the International Search Report dated 21 December 1992, as well as the disclosure of the international application as filed.

As originally written, independent claims 1 and 14 were specific to a laminated window wherein the outer sheets were each described as "flexible" and "plastic". While such flexible plastic sheets are used in preferred embodiments, those skilled in the art will recognize that other materials, including flexible non-plastic sheets, or inflexible plastic sheets or in-flexible, non-plastic sheets, may also be fully operative. For example, applicants* invention lends itself to a safety glass embodiment wherein applicants' integrally- formed, semi-conductive ink pattern may be laminated within glass outer sheets forming a safety glass composite. So that claim 1 encompasses such embodiments, "flexible" and "plastic" have been deleted. Amended claim 2 and claim 13, however, are specific to the preferred embodiment employing flexible plastic sheets.

Claim 1 has also been amended to delete reference to the semi-conductive end-connecting traces being laterally- disposed. Such language might be misconstrued so as to limit applicants^• window unnecessarily to one wherein the integrally- formed, semi-conductive end-connectingtraces are substantially vertical and the integrally-formed semi-conductive ink stripes therebetween are substantially horizontal, as depicted in the drawings. It is otherwise apparent from applicants' disclosure that the integrally-formed stripes and end-connecting traces can be disposed in any orientation within the window laminate which would best achieve the desired defrosting-defogging capability. Such orientation, for example, would include substantially-vertical, integrally-formed stripes and substantially-horizontal, end-connecting traces.

As already indicated, these amendments are consistent with the application as filed. Thus, for example, the original disclosure states:

"The shape or outline of window 12 and the ink pattern 32 are illustrative only ... the present invention is not limited to any particular automobile window or ink pattern." (page 12, lines 3-8)

The intended breadth of the claims is otherwise reflected in the disclosure and claims as originally filed. Thus, for example, original claim 1 (and claim 1 as amended herein) specifies that:

"... the composition, size, location and heating capacity of the semi-conductive ink stripes and respective integrally-formed, semi- conductive end-connecting traces being selected to achieve the predetermined defrosting- defogging capability of the window employing the available electrical-energy source..."

The amendments do not have any impact on the description and the drawings and do not go beyond the disclosure of the international application as filed.