TRANSPARENT PANE HAVING AN ELECTRICAL HEATING LAYER, METHOD FOR THE PRODUCTION THEREOF, AND USE THEREOF

Abstract

A transparent pane, having at least one heatable, electrically conductive coating connected to at least two collection electrodes, provided for electrically connecting to a supply voltage to generate a heating current that flows across a heating field formed between the at least two collection electrodes is described. The heating field includes at least one communication window free from the heatable, electrically conductive coating. The transparent pane further includes at least one heatable, electrically conductive coating. The additional electrode is connected to one of the two collection electrodes via a respective current supply line.

Claims

1.-15. (canceled)

16. A transparent pane comprising: i) at least one heatable, electrically conductive coating connected to at least two collection electrodes adapted for electrical connection to two poles of a voltage source so that upon application of a supply voltage, a heating current flows via a heating field formed between the at least two collection electrodes, wherein: ia) the heating field has at least one communication window free of the heatable, electrically conductive coating, and ib) the heatable, electrically conductive coating is bounded by a peripheral coating edge, and a peripheral edge strip that is free of the electrically conductive coating and extends all the way to a peripheral pane edge of the transparent pane, ii) two first sides including a top side and a bottom side, and two second sides including a left side and a right side, iii) at least one heatable electrically conductive coating arranged outside the heating field and spatially separated from the heating field by a collection electrode of the at least two collection electrodes that runs along a first side of the pane edge; and iv) at least one additional electrode arranged in a region of each of the two second sides of the pane edge, each connected to a first collection electrode of the at least two collection electrodes via at least one power supply line that runs along the peripheral coating edge and along a respective one of the two second sides of the pane edge through one or more of: iva) a section of the peripheral edge strip, ivb) a section of the peripheral coating edge that is electrically decoupled from the heating field by a respective at least one associated coating free line, and ivc) a section of the electrically conductive coating arranged outside the heating field that is electrically decoupled from the heating field by a respective at least one associated coating free line; wherein the heatable electrically conductive coating arranged outside the heating field comprises: A) at least one connection conductor electrically associated with each of the at least one additional electrode, and electrically connected to a second collection electrode of the at least two collection electrodes via the electrically conductive coating, the second collection electrode having an opposite polarity from a polarity of the first collection electrode, and B) at least two systems of coating-free lines, each comprising at least four coating-free lines, positioned opposite one another as a mirror image relative to a vertical centerline and axis of symmetry of the transparent pane that are configured to direct the heating current, flowing upon application of a supply voltage, from each of the at least one additional electrode to the second collection electrode of opposite polarity via: B1) at least two current paths, a1 and a2 to a.sub.n, formed in regions of the electrically conductive coating arranged outside the heating field, and B2) the at least one connection conductor, wherein lengths of the current paths, a1 and a2 to a.sub.n, satisfy a mathematical relationship VH1:
VH.sub.1=h.sub.1/b.sub.n=0.5 to 2.0, where n represents an integer number from 2 to 30, a.sub.1 designates a current path from the at least one additional electrode to a nearest opposing section of the at least one connection conductor, h.sub.1 represents a height of the current path a.sub.1 delimited by two coating-free lines of the at least four coating-free lines a.sub.2 . . . a.sub.n designate remaining current paths, and b.sub.n represents a width of a current path a.sub.n.

17. The transparent pane according to claim 16, wherein each of the at least one additional electrode, the connection conductor associated therewith, the system of coating-free lines, and the current paths. a.sub.1 and a.sub.2+a.sub.n, are arranged as a mirror image relative to the vertical centerline and axis of symmetry of the transparent pane.

18. The transparent pane according to claim 16, wherein VH.sub.1=0.75 to 1.5.

19. The transparent pane according to claim 16, wherein VH.sub.1=0.8 to 1.2.

20. The transparent pane according to claim 16, wherein at least one of the at least four coating-free lines runs, at least in sections, in one or more of: a) rectilinearly, b) wave-shaped, c) meander-shaped, d) sawtooth-shaped, and e) zigzag-shaped.

21. The transparent pane according to claim 16, wherein at least one of the at least four coating-free lines runs, at least in sections, in one or more of: a) continuously, and b) as a broken line of discrete cuts.

22. The transparent pane according to claim 16, wherein at least one of the at least four coating-free lines is produced by laser ablation of the electrically conductive coating of the heating field, and/or of the electrically conductive coating.

23. The transparent pane according to claim 16, wherein in the installed state of the transparent pane, the heatable, electrically conductive coating arranged outside the heating field is arranged along the bottom side of the pane edge.

24. The transparent pane according to claim 16, wherein in the installed state of the transparent pane, the heatable, electrically conductive coating arranged outside the heating field is arranged along the top side of the pane edge.

25. The transparent pane according to claim 23, wherein the heatable, electrically conductive coating arranged outside the heating field is arranged in a region of a lower or of an upper wiper parking zone.

26. The transparent pane according to claim 16, wherein the at least four substantially horizontal coating-free lines have each a width of 10 μm to 1 mm.

27. The transparent pane according to claim 16, wherein at least one of the at least two collection electrodes is divided into at least two subregions spatially separated from one another.

28. A method for producing the transparent pane according to claim 16, the method comprising the following process steps: (A) producing an electrically conductive coating; (B) producing at least one coating-free communication window in the heatable, electrically conductive coating of the heating field; (C) forming: (c1) the at least two collection electrodes for connection to the two poles of the voltage source, said electrodes being electrically connected to the heatable, electrically conductive coating so that by application of a supply voltage, a heating current flows via a heating field situated between the two collection electrodes, and/or (c2) the at least two collection electrodes for connection to the two poles of the voltage source, said electrodes being electrically connected to the heatable, electrically conductive coating, wherein at least one of the at least two collection electrodes is divided into at least two subregions spatially separated from one another; (D) producing: (d1) in a region of each of the two second sides of the pane edge, the at least two additional electrodes opposite one another as a mirror image relative to the centerline and axis of symmetry of the transparent pane; (d2) at least two connection conductors as a mirror image opposite one another relative to the vertical centerline and axis of symmetry of the transparent pane and electrically associated with the additional electrodes, said connection conductors being electrically connected, upon application of a supply voltage, to the collection electrode of opposite polarity via the electrically conductive coating; and (d3) at least two power supply lines arranged as a mirror image of each other relative to the vertical centerline and axis of symmetry of the transparent pane, each of said supply lines respectively connecting the at least one additional electrode to at least one collection electrode or subregion thereof, and running along the coating edge and along a respective one of the two second sides of the pane edge, through one or more of: a section of the peripheral edge strip, a section of the peripheral coating edge that is electrically decoupled from the heating field by a respective at least one associated coating-free line, and a section of the electrically conductive coating arranged outside the heating field that is electrically decoupled from the heating field by a respective at least one associated coating-free line; (E) forming: (e1) at least two coating-free lines running along the power supply lines on the side of the heating field; (e2) at least two systems of coating-free lines positioned opposite one another as a mirror image, each comprising at least four coating free lines that are arranged so that, upon application of a supply voltage, they direct the heating current flowing from a respective one of the at least one additional electrode to the second collection electrode of opposite polarity via: at least two current paths, a.sub.1 and a.sub.2 to a.sub.n, and the at least one connection conductor, wherein lengths of the current paths, a.sub.1 and a.sub.2 to a.sub.n, satisfy a mathematical relationship VH1:
VH.sub.1=h.sub.1/b.sub.n=0.5 to 2.0, where n represents an integer number from 2 to 30, (a.sub.1) designates a current path from the at least one additional electrode to a nearest opposing section of the at least one connection conductor, (h.sub.1) represents a height of the current path a.sub.1 delimited by two coating-free lines of the at least four coating-free lines (a.sub.2 . . . a.sub.n) designate remaining current paths, and b.sub.n represents a width of a current path a.sub.n wherein the process steps (B) and (E) are performed one after the other or simultaneously, and wherein the process steps (C) and (D) are performed simultaneously or one after the other as well as before or after the process steps (B) and (E).

29. The method according to claim 28, wherein VH1=0.75 to 1.5.

30. The method according to claim 29, wherein: the at least two coating-free lines and the at least two systems of coating-free lines are produced by laser ablation of the electrically conductive coating inside and outside the heating field, and the process steps (C) and (D) are performed using screen printing.

31. A method, comprising using of the transparent pane produced in accordance with the method of claim 28 as a functional and/or decorative single piece and as an assembly part in furniture, appliances, buildings, and means of transportation.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0137] The invention is now explained in detail with reference being made to the accompanying figures. They depict in simplified, not-true-to-scale representation:

[0138] FIG. 1 a plan view of a windshield 1 according to the invention in simplified representation;

[0139] FIG. 2 a view of a vertical section through a detail of the windshield according to the invention of FIG. 1;

[0140] FIG. 3 a perspective view of a detail of the windshield according to the invention of FIG. 1;

[0141] FIG. 4 a plan view of the detail B of the windshield 1 according to the invention of FIG. 1;

[0142] FIG. 5 a plan view of the detail A from an exemplary embodiment of the windshield 1 according to the invention of FIG. 1;

[0143] FIG. 6 a plan view of the detail A from another exemplary embodiment of the windshield 1 according to the invention of FIG. 1, together with the enlarged detail C;

[0144] FIG. 7 a plan view of the detail A from yet another exemplary embodiment of the windshield 1 according to the invention of FIG. 1, together with the enlarged detail D;

[0145] FIG. 8 a plan view of the detail from yet another exemplary embodiment of the windshield 1 according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

[0146] FIG. 1 in Conjunction with FIGS. 2, 3, and 4

[0147] FIG. 1 depicts a transparent windshield 1 of a motor vehicle viewed from the inside in a simplified representation. Here, the windshield is implemented, for example, as a composite pane, whose structure is illustrated using the representation of a vertical section through a detail of the windshield 1 in FIG. 2 and using the perspective representation of a detail of the windshield 1 in FIG. 3.

[0148] Accordingly, the windshield 1 comprises two rigid individual panes, namely an outer pane 2 and an inner pane 3 that are firmly bonded to one another by a thermoplastic adhesive layer 4, here, for example, polyvinyl butyral film (PVB), an ethylene vinyl acetate film (EVA), or a polyurethane film (PU). The two individual panes 2, 3 have roughly the same size and shape and can, for example, have a trapezoidal curved contour, not shown in detail in the figures. They are made, for example, of glass, also possibly being constructed from a non-glass material such as plastic. For applications other than windshields, it would also be possible to produce the two individual panes 2, 3 from a flexible material. The contour of the windshield 1 is determined by a pane edge 5, common to the two individual panes 2, 3, the windshield 1 having, at the top and bottom, two first sides 6, 6′ positioned opposite one another as well as, on the left and the right, two second sides 7, 7′ opposite one another.

[0149] As shown in FIGS. 2 and 3, a transparent, electrically conductive coating 8 is deposited on the side of the inner pane 3 bonded to the adhesive layer 4. Here, the heatable, electrically conductive coating 8 is, for example, applied substantially to the entire surface of the inner pane 3, with a peripheral edge strip 9 on all sides not coated, such that a coating edge 10 of the electrically conductive coating 8 is set back inwardly relative to the pane edge 5. By this means, electrical isolation of the electrically conductive coating 8 relative to the outside is effected. Moreover, the electrically conductive coating 8 is protected against corrosion penetrating from the pane edge 5.

[0150] The electrically conductive coating 8 comprises, in a known manner, a layer sequence (not shown) with at least one electrically heatable, metallic sublayer, preferably silver, and, optionally, other sublayers such as antireflective and blocker layers. Advantageously, the layer sequence has high thermal stability such that it withstands the temperatures of typically 600° C. required for bending glass panes without damage, but also with the possibility of providing layer sequences with low thermal stability. It is equally possible for the electrically conductive coating 8 to be applied as a metallic single layer. It is likewise conceivable not to apply the electrically conductive coating 8 directly on the inner pane 3 but, instead, to apply it first on a carrier, for example, a plastic film that is subsequently glued to the outer and inner pane 2, 3. Alternatively, the carrier film can be bonded to adhesive films (e.g., PVB films) and glued as a trilayer arrangement to the inner and outer pane 2, 3. The heatable, electrically conductive coating 8 is preferably applied by sputtering or magnetron cathodic sputtering onto the inner or outer pane 2, 3.

[0151] As shown in FIG. 1, the electrically conductive coating 8 is electrically conductively connected adjacent the first side 6, 6′, i.e., on the upper and lower pane edge 5, to a strip-shaped upper collection electrode or busbar 11 and to a strip-shaped lower collection electrode 11′. The upper collection electrode 11 and the lower collection electrode 11′ are provided for connecting to, in each case, one pole of a voltage source (not shown). The two collection electrodes 11, 11′ of opposite polarity serve for uniform introduction and distribution of the heating current into the heating field 12 of the heatable coating 8 situated between them. The two collection electrodes 11, 11′ are, for example, printed onto the electrically conductive coating 8 and have, in each case, an at least approximately rectilinear course.

[0152] The collection electrodes 11, 11′ can also, however, be subdivided, in each case, into two subregions spatially separated from one another.

[0153] The upper collection electrode 11 in the installed state of the windshield 1 separates the heating field 12 from the subregion 8′″ of the electrically conductive coating 8 running along the upper first side 6 of the pane edge 5.

[0154] The lower collection electrode 11′ in the installed state of the windshield 1 separates the heating field 12 from the subregion 8′ running along the lower first side 6′. This subregion 8′ serves for the heating of the wiper parking zone. Further details of various embodiments according to the invention emerge from details A of the FIGS. 5 to 9.

[0155] Below the upper collection electrode 11, three coating-free communication windows are arranged in the heating field 12 centrally as a mirror image. In other words, they are divided in half by the imaginary vertical centerline M or axis of symmetry.

[0156] Two power supply lines 15, 15′ arranged as a mirror image relative to one another run from the two ends of the upper collection electrode 11 in the subregions 8″ of the coating 8 along the respective associated subregion of the coating edge to the additional electrodes 18, 18′ opposite one another in the subregion 8′. The power supply lines 15, 15′ and the additional electrodes 18, 18′ are made of the same material as the collection electrodes 11, 11′.

[0157] The power supply lines 15, 15′ and the additional electrodes 18, 18′ are electrically decoupled by the coating-free lines 16, 16′ associated in each case therewith, running along the power supply lines 15, 15′ on the side of the heating field 12 from the heating field 12. The coating-free lines 16, 16′ have a width of 100 μm. They are preferably producible by laser ablation.

[0158] The coating-free lines 16, 16′ run all the way to the upper collection electrode 11 and continue above the upper collection electrode 11 all the way to the peripheral edge strip 9 and separate the subregions 8″ running along the second sides 7, 7′ from the subregion 8′″ running along the upper first side 6 from one another. Further details emerge from the detail B of FIG. 4.

[0159] FIG. 4 depicts the intersection 17 of the coating-free line 16 with the upper collection electrode 11. Preferably, this intersection 17 is producible by printing, by screen printing, the upper collection electrode 11 over the coating-free line 16 previously produced by laser ablation.

[0160] FIG. 4 further depicts the preferred configuration of the black masking strip 13 as it is also use in the region of the lower collection electrode 11′ and the regions 8″, 15, 16. The masking strip 13 conceals the functional elements in these regions and also protects them against UV radiation, which can damage the functional elements. Specifically, the black masking strip 13 comprises a visually concealing, opaque subregion 13′, which transitions on its edge 13″ into the visually partially transparent subregion 13′″, which itself reaches to the edge 13″″. The visually partially transparent subregion 13′″ is, for example, a dot grid. Preferably, the masking strip 13 is applied to the inside, i.e., the side of the outer pane 2 turned toward the inner pane 3, by screen printing and fired prior to assembly, before the two panes 2 and 3 are bonded with the adhesive layer 4.

FIG. 5 in Conjunction with FIG. 1

[0161] FIG. 5 depicts a plan view of the detail A from an exemplary embodiment of the windshield 1 of FIG. 1.

[0162] The detail A portrays only the left subregion of the coating 8′ in the region of the wiper parking zone all the way to the centerline and axis of symmetry M. The right subregion of the coating 8′ is a mirror image of the left subregion 8′ and, consequently, is not portrayed.

[0163] In this exemplary embodiment of FIG. 5, the coating-free line 16 transitions into the system 16″ of three horizontal coating-free lines and one vertical coating-free line of a line width of 30 μm. In this system 16″, three horizontal coating-free lines arranged parallel to one another branch in the left subregion 8′ at three branching points 17″. The upper coating-free line touches the upper ends 20 of the vertically arranged additional electrode 18 and of the vertically arranged leg of the counter electrode/connection conductor 19. The central coating-free line touches the lower end 20 of the additional electrode and ends at its endpoint 21 on the vertically arranged leg of the counter electrode/connection conductor 19. The lower coating-free line runs from its branching point 17″ out parallel to the lower peripheral coating edge 10 along the lower first side 6′ on the way to the imaginary centerline M and beyond.

[0164] The upper coating-free line runs after the upper end 20 of the vertical leg of the counter electrode/connection conductor 19 vertically downward and crosses the horizontal leg of the counter electrode/connection conductor 19 in the intersection 17′ and continues below the horizontal leg all the way to the branching point 17″ of the lower coating-free line.

[0165] Details of the endpoints 20 are apparent from the enlarged detail C in FIG. 6. Details of the branching points 17″ are apparent from the enlarged detail D of FIG. 7.

[0166] Two current paths a.sub.1 and a.sub.2 are formed in the subregion 8′ by this system 16″ of four coating-free lines. The current path a.sub.1 runs from the additional electrode 18 to the vertical leg of the counter electrode/connection conductor 19; it is thus, in this embodiment and in the subsequently described embodiments, the first current path. From the horizontal leg of the counter electrode/connection conductor 19, the current path a.sub.2 runs all the way to the lower collection electrode 11′. The relationship VH.sub.1=0.9 wir and n=2. Upon application of a supply voltage of 12 V, the heating current flows in the system 16″ from the additional electrode 18 via the counter electrode/connection conductor 19 to the lower collection electrode 11′.

[0167] It is a very particular advantage of the system 16″, 18, 19 according to the invention that by means of it the coating 8′ is heated uniformly, the specific heating power being at 400 to 550 W/m.sup.2. Another very particular advantage of the system 16″, 18, 19 according to the invention is, furthermore, that the entire configuration can be adapted by a simple parallel shift P, for example, of the additional electrode 18 and/or of the vertical leg of the counter electrode/connection conductor 19 to the requirements of the individual case without the specific heating power being disadvantageously altered—for example, by the occurrence of hot spots and/or cold spots. The optimum configuration of the electrodes 18, 19 and of the current paths a.sub.1 . . . a.sub.n can be determined in a simple manner for the individual case using customary, known simulation programs.

[0168] Overall, even at particularly low temperatures<0° C., the embodiment of the transparent pane according to the invention 1 of FIG. 5 effectively prevents the windshield wipers from freezing in the wiper parking zone.

FIG. 6 in Conjunction with FIG. 1

[0169] FIG. 6 depicts a plan view of the detail A from an exemplary embodiment of the windshield 1 of FIG. 1.

[0170] As in FIG. 5, the detail A portrays only the left subregion of the coating 8′ in the region of the wiper parking zone all the way to the centerline and axis of symmetry M. Here again, the right subregion of the coating 8′ is a mirror image of the left subregion 8′ and, consequently, does not need to be portrayed.

[0171] In this exemplary embodiment of FIG. 6, the coating-free line 16 transitions into the system 16″ of a total of three horizontal and two vertical coating-free lines of a line width of 30 μm. In this system 16″, three horizontal coating-free lines arranged parallel to one another branch, in the left subregion 8′, at the three branching points 17″. The upper coating-free line touches the upper and of the additional electrode 18. For details, reference is made to the enlarged detail C of FIG. 6. Then, the coating-free line runs along the horizontal leg of the two-part counter electrode/connection conductor 19. In this region, a vertical coating line branches (branching point 17″), which line runs all the way to the lower horizontal coating-free line. The center horizontal coating-free line of the system 16″ touches the lower ends of the vertical additional electrode 18 and of the vertical leg of the two-part counter electrode/connection conductor 19 and runs all the way to the branching point 17″ with the coating-free line arranged along the vertical leg of the counter electrode/connection conductor 19. Details concerning the branching points 17″ are apparent from the detail D of FIG. 7.

[0172] In the region of the end of the horizontal leg of the two-part counter electrode/connection conductor 19, the coating-free line runs vertically downward and crosses a subregion of the counter electrode/connection conductor 19 spatially separated therefrom but electrically coupled to the horizontal leg. The intersection 17′ has the same configuration as the intersection 17 in FIG. 4. The subregion of the counter electrode/connection conductor 19 is then electrically coupled to the lower collection electrode 11′, namely, via the electrically conductive coating.

[0173] Three current paths a.sub.1, a.sub.2, and a.sub.3 are formed by this system 16″ of five coating-free lines. The current path a.sub.1 runs from the additional electrode 18 to the vertical leg of the two-part counter electrode/connection conductor 19. The current path a.sub.2 runs from the horizontal leg of the counter electrode/connection conductor 19 all the way to the separate horizontal subregion of the counter electrode/connection conductor 19. The current path a.sub.3 runs from the separate horizontal subregion of 19 to the lower collection electrode 11′.

[0174] The additional electrode 18 is directly connected to the first collection rail 11 via the power supply line 15. In contrast thereto, the counter electrode 19 is not directly connected to the second collection rail 11′. The counter electrode 19 is a connection conductor that connects to one another two coating segments that are formed by the coating-free lines such that a current can flow between the coating segments.

[0175] The current flow of all current paths a.sub.1-a.sub.n is driven by the difference in potential between the additional electrode 18 (connected to the first collection rail 11) and the second collection rail 11′. The segmentation of the conductive coating formed by the coating-free lines as well as the connection of the segments by means of the counter electrode(s) 19 serve to direct the current flow in the form of the current paths a.sub.1-a.sub.n.

[0176] The relationship VH.sub.1=1, the relationship VH.sub.2=1, and n=2 and 3. Upon application of a supply voltage of 12 V, the heating current flows in the system 16″ from the additional electrode 18 via the counter electrode/connection conductor 19 to the lower collection electrode 11′. Upon application of a supply voltage of 12 V, the current flows in the system 16″ from the additional electrode 18 via the two-part counter electrode/connection conductor 19 to the lower collection electrode 11′.

[0177] It is a very particular advantage of this system 16″, 18, 19 according to the invention as well that by this means the coating 8′ is heated uniformly, with the specific heating power at 400 to 550 W/m.sup.2. Another very particular advantage of the system 16″, 18, 19 according to the invention is, furthermore, that the entire configuration can be adapted, by a simple parallel shift P, for example, of the additional electrode 18 and/or of the vertical leg of the counter electrode/connection conductor 19, to the requirements of the individual case without the specific heating power adversely changing—for example, through the occurrence of hot spots and/or cold spots. The optimum configuration of the electrodes 18, 19 and of the current paths a.sub.1 . . . a.sub.n for the individual case can be determined in a simple manner using customary, known simulation programs.

[0178] Overall, the embodiment of the transparent pane 1 according to the invention of FIG. 6 effectively prevents the windshield wipers from freezing in the wiper parking zone even with particularly low temperatures of <0° C.

FIG. 7 in Conjunction with FIG. 1

[0179] FIG. 7 depicts a plan view of the detail A from an exemplary embodiment of the windshield 1 of FIG. 1.

[0180] As in FIGS. 5 and 6, the detail A portrays only the left subregion of the coating 8′ in the region of the wiper parking zone all the way to the centerline and axis of symmetry M. Here again, the right subregion of the coating 8′ is a mirror image of the left subregion 8′ and, consequently, does not need to be portrayed.

[0181] In this exemplary embodiment of FIG. 7, the coating-free line 16 transitions into the system 16″ of a total of three horizontal and three vertical coating-free lines of a line width of 30 μm. In this system 16″, three horizontal coating-free lines arranged parallel to one another branch, in the left subregion 8′, at the three branching points 17″. Of these, the upper coating-free line touches the upper end of the vertical additional electrode 18 and the upper end of the vertical leg of the three-part additional electrode 19. Thereafter, the upper coating-free line runs along the spatially separate upper subregion of the three-part counter electrode/connection conductor 19. The upper subregion is coupled to the lower horizontal leg of the three-part counter electrode and its third spatially separate lower subregion.

[0182] After the endpoint 20, there is a branching 17″ where one coating-free line branches vertically downward and runs along the vertical leg of the two three-part counter electrodes/connection conductors 19 (for details, cf. the enlarged detail D of FIG. 7), intersects the lower horizontal leg and ends at the lower horizontal coating-free line. In the further course, the upper horizontal coating-free line branches once more, whereupon the branched coating-free line runs vertically downward, touches the endpoint 20 of the horizontal lower leg, runs further through the gap between the end of the horizontal lower leg and the third horizontal subregion of the three-part counter electrode/connection conductor 19, and, after that, coincides with the lower horizontal coating-free line.

[0183] The upper coating-free line runs along the horizontal upper subregion of the counter electrode/connection conductor 19 and, after that, bends vertically downward, touches the end of the horizontal upper subregion, intersects at 17′ the horizontal, lower, third subregion of the three-part counter electrode/connection conductor 19, and then also coincides with the lower horizontal coating-free line.

[0184] The horizontal, lower, third subregion of the three-part counter electrode/connection conductor 19 then runs further all the way to the centerline and axis of symmetry M.

[0185] Four current paths a.sub.1, a.sub.2, a.sub.3, and a.sub.4 are formed by this system 16″ of six coating-free lines. The current path a.sub.1 runs from the additional electrode 18 to the vertical leg of the three-part counter electrode/connection conductor 19. The current path a.sub.2 runs from the horizontal lower leg of the counter electrode 19 all the way to the separate horizontal upper subregion of the counter electrode/connection conductor 19. The current path a.sub.3 runs from this separate horizontal upper subregion of 19 to the horizontal lower subregion of the three-part counter electrode/connection conductor 19. From there out, the current path a.sub.4 runs to the lower collection electrode 11′.

[0186] The relationship VH.sub.1=1.5 and n=2 to 4. Upon application of a supply voltage of 12 V, the current flows in the system 16″ from the additional electrode 18 via the three-part counter electrode 19 to the lower collection electrode 11′.

[0187] It is a very particular advantage of this system 16″, 18, 19 according to the invention as well that by means of it, the coating 8′ is heated uniformly, the specific heating power being at 400 to 550 W/m.sup.2. Another very particular advantage of the system 16″, 18, 19 is, furthermore, that the entire configuration can be adapted by simple parallel shifts P, for example, of the additional electrode 18 and/or of the vertical leg of the counter electrode/connection conductor 19 to the requirements of the individual case, without the specific heating power being disadvantageously altered—for example, by the occurrence of hot spots and/or cold spots. The configuration of the electrodes 18, 19 and of the current paths a.sub.1 . . . a.sub.n optimum for the individual case can be determined in a simple manner using customary, known simulation programs.

[0188] Overall, even at particularly low temperatures<0° C., the embodiment of the transparent pane 1 according to the invention of FIG. 7 effectively prevents the windshield wipers from freezing in the wiper parking zone.

FIG. 8 in Conjunction with FIG. 1

[0189] FIG. 8 depicts a plan view of the detail A from an exemplary embodiment of the windshield 1 of FIG. 1.

[0190] As in FIGS. 5, 6, and 7, the detail A portrays only the left subregion of the coating 8′ in the region of the wiper parking zone all the way to the centerline and axis of symmetry M. Here again, the right subregion of the coating 8′ is a mirror image of the left subregion 8′ and, consequently, does not need to be portrayed.

[0191] The design of the windshield 1 of FIG. 8 is a further development of the design of the windshield 1 of FIG. 6. The difference resides in the fact that in the design of FIG. 8 the coating 8′ in the region of the wiper parking zone is divided by two horizontal and ten vertical coating-free lines into ten current paths a.sub.1-a.sub.10 and not into three current paths a.sub.1-a.sub.3 by three horizontal and three vertical coating-free lines.

[0192] The relationship VH.sub.1=1.5 and n=2 to 5. Upon application of a supply voltage of 12 V, the current flows in the system 16″ from the additional electrode 18 via the four-part counter electrode/connection conductor 19 to the lower collection electrode 11′.

[0193] It is a very particular advantage of this system 16″, 18, 19 according to the invention as well that by this means the coating 8′ is heated especially uniformly, with the specific heating power at 500 to 700 to 0 W/m.sup.2. Another very particular advantage of the system 16″, 18, 19 according to the invention is that the entire configuration can be adapted, by simple parallel shifts P, for example, of the additional electrode 18 and/or of the vertical leg of the counter electrode/connection conductor 19, to the requirements of the individual case without the specific heating power adversely changing—for example, through the occurrence of hot spots and/or cold spots. The optimum configuration of the electrodes 18, 19 and of the current paths a.sub.1 . . . a.sub.n for the individual case can be determined in a simple manner using customary, known simulation programs.

[0194] Overall, the embodiment of the transparent pane 1 according to the invention of FIG. 7 effectively prevents the windshield wipers from freezing in the wiper parking zone, even with particularly low temperatures of <0° C.

[0195] In FIGS. 1 to 8, the reference characters have the following meaning: [0196] 1 windshield [0197] 2 outer pane [0198] 3 inner pane [0199] 4 adhesive layer [0200] 5 peripheral pane edge [0201] 6, upper first side of the pane edge 5 in the installed state of the windshield 1 [0202] 6′ lower first side of the pane edge 5 in the installed state of the windshield 1 [0203] 7, 7′ lateral second side of the pane edge 5 in the installed state of the windshield 1 [0204] 7 electrically conductive coating [0205] 8′ lower electrically conductive coating 8 arranged in the region of the wiper parking zone outside the heating field 12 along the lower first side 6′ of the pane edge 5 in the installed state of the windshield 1 [0206] 8″ subregions of the electrically conductive coating 8 arranged outside the heating field 12 along the second sides 7 and 7′ of the pane edge 5 in the installed state of the windshield 1 [0207] 8′″ subregion of the electrically conductive coating 8 arranged outside the heating field 12 along the upper first side 6 of the pane edge 5 in the installed state of the windshield 1 [0208] 9 peripheral edge strip free of the electrically conductive coating 8 [0209] 10 peripheral coating edge [0210] 11, upper collection electrode in the installed state of the windshield 1 [0211] 11′ lower collection electrode in the installed state of the windshield 1 [0212] 12 heating field [0213] 13 masking strip [0214] 13′ visually concealing, opaque subregion of the masking strip 13 [0215] 13″ edge of the visually concealing, opaque subregion of the masking strip 13 [0216] 13′″ visually partially transparent subregion of the masking strip 13 [0217] 13″″ edge of the visually partially transparent subregion of the masking strip 13 [0218] 14 communication window free of the electrically conductive coating 8 [0219] 15, 15′ power supply lines running from the upper collection electrode 11 along the respective associated coating edge 10 in the respective associated subregions 8″ to the additional electrodes 18, 18′ [0220] 16, 16′ coating-free line running along the power supply lines 15, 15′ on the side of the heating field 12 [0221] 16″ system of at least four coating-free lines in the coating 8′ in the region of the wiper parking zone [0222] 17 intersection of the coating-free lines 16, 16′ with the collection electrode 11 [0223] 17′ intersection of a coating-free line 16″ with a counter electrode 19 [0224] 17″ branching point of a coating-free line 16″ [0225] 18, 18′ additional electrodes electrically connected to the collection electrode 11 via power supply lines 15, 15′ arranged in the lower electrically conductive coating 8′ (wiper parking zone) [0226] 19 counter electrode to the additional electrode 18 (connection conductor) [0227] 20 endpoint of an additional electrode 18 or a counter electrode 19 on a coating-free line 16″ [0228] 21 endpoint of a coating-free line 16″ on an additional electrode 18 or a counter electrode 19 [0229] a.sub.1 length of the current path from the additional electrode 18 to the nearest opposing section of the counter electrode 19 [0230] a.sub.2, . . . , a.sub.n length of a current path [0231] h.sub.1 height of the current path a.sub.1 [0232] b.sub.2, . . . b.sub.n width of the current paths a.sub.2 to a.sub.n [0233] ½b.sub.6 one half of the width b.sub.6 [0234] A enlarged detail of the windshield 1 [0235] B enlarged detail of the windshield 1 [0236] C enlarged detail of the windshield 1 [0237] D enlarged detail of the windshield 1 [0238] M vertical centerline and axis of symmetry [0239] P parallel shift