PANE WITH AN ELECTRICAL HEATING REGION

Abstract

A pane with an electrical heating region is presented. The pane has a substantially trapezoidal first pane, an electrically conductive coating applied on part of a surface of the first pane, a substantially trapezoidal electrical heating region that is electrically divided from the electrically conductive coating by a separating line, and two collecting conductors connected to the electrically conductive coating in the electrical heating region.

Claims

1.-15. (canceled)

16. A pane, comprising: a substantially trapezoidal first pane with a surface, a first base with length l.sub.1 and a second base with length l.sub.2, wherein a ratio v of the length l.sub.1 to the length l.sub.2 is such that: v=l.sub.1:l.sub.2 is from 0.70:1 to 0.98:1 at least one electrically conductive coating applied on a part of the surface; at least one substantially trapezoidal electrical heating region electrically divided by at least one separating line from the electrically conductive coating, wherein a first base of the heating region is arranged immediately adjacent the first base of the first pane, and wherein a second base of the heating region is arranged immediately adjacent the second base of the first pane; and at least two collecting conductors connected to the electrically conductive coating in the electrical heating region, the at least two collecting conductors configured to establish an electrical connection to a voltage source such that a current path for a heating current is formed between the collecting conductors, wherein a ratio u of a length b.sub.1 of the first base of the heating region to a length b.sub.2 of the second base of the heating region is such that: u=b.sub.1:b.sub.2 is from v:0.99 to v:0.50.

17. The pane according to claim 16, wherein: u=b.sub.1:b.sub.2 is from v:0.99 to 0.99, or u=b.sub.1:b.sub.2 is from 1.01 to v:0.50.

18. The pane according to claim 16, wherein the first pane or the electrical heating region has a shape of a symmetrical trapezoid.

19. The pane according to claim 16, wherein the first base of the heating region is arranged substantially parallel to the first base of the first pane.

20. The pane according to claim 16, wherein the length of a shorter of the first base and the second base of the first pane is equal to the length of the immediately adjacent base of the heating region plus 2×r, wherein r is a width of an edge decoating region on each side of the pane.

21. The Pane according to claim 16, wherein a width d of the separating line is from 30 μm to 200 μm.

22. The Pane according to claim 21, wherein the width d of the separating line is from 70 μm to 140 μm.

23. The pane according to claim 16, wherein the collecting conductors are implemented as fired printing paste that has a specific resistance ρ.sub.a from 0.8 μohm.Math.cm to 7.0 μohm.Math.cm.

24. The pane according to claim 23, wherein the specific resistance ρ.sub.a is from 1.0 μohm.Math.cm to 2.5 μohm.Math.cm.

25. The pane according to claim 23, wherein the fired printing paste contains one or more of: a) metallic particles, b) metal particles, c) carbon particles and d) silver particles.

26. The pane according to claim 16, wherein the surface of the first pane is areally bonded to a second pane via a thermoplastic intermediate layer.

27. The pane according to claim 16, wherein the first pane or the second pane contains one of a) glass, b) polymers, and c) mixtures of a) and b).

28. The pane according to claim 27, wherein a) comprises flat glass, float glass, quarts glass, borosilicate glass, and/or soda lime glass.

29. The pane according to claim 27, where b) comprises one or more of polyethylene, polypropylene, polycarbonate, and/or polymethylmethacrylate.

30. The pane according to claim 16, wherein the electrically conductive coating is transparent.

31. The pane according to claim 16, wherein the electrically conductive coating has a sheet resistance from 0.4 ohm/square to 10 ohm/square.

32. The pane according to claim 31, wherein the sheet resistance is from 0.5 ohm/square to 1 ohm/square.

33. The pane according to claim 16, wherein the electrically conductive coating contains one or more of: a) silver (Ag), b) indium tin oxide (ITO), c) fluorine-doped tin oxide (SnO.sub.2:F), and d) aluminum-doped zinc oxide (ZnO:Al).

34. The pane according to claim 16, wherein the electrically conductive coating has, inside the electrical heating region, at least one coating-free region.

35. The pane according to claim 34, wherein the at least one coating-free region forms a communication window.

36. The pane according to claim 34, wherein the at least one coating free region is arranged in a center region of one of the first base and the second base of the first pane.

37. The pane according to claim 17, wherein a distance h.sub.1 between the at least two collecting conductors at a center of the electrical heating region is greater than a distance h.sub.2 between the at least two collecting conductors at outer edges of the electrical heating region.

38. A method for producing a pane with an electrical heating region, the method comprising: (a) preparing a substantially trapezoidal first pane having a surface, a first base with length l.sub.1, a second base with length l.sub.2, wherein a ratio v of the length l.sub.1 to the length l.sub.2 is such that: v=l.sub.1:l.sub.2 is from 0.70:1 to 0.98:1; (b) applying an electrically conductive coating on a part of the surface of the first pane; (c) providing an electrical division of at least one substantially trapezoidal electrical heating region from the electrically conductive coating by forming at least one separating line; arranging a first base of the heating region immediately adjacent the first base of the first pane; and arranging a second base of the heating region immediately adjacent the second base of the first pane, wherein a ratio u of a length b.sub.1 of the first base of the heating region to a length b.sub.2 of the second base of the heating region is such that: u=b.sub.1:b.sub.2 is from v:0.99 to v:0.50; and (d) providing at least two collecting conductors for connection to a voltage source, the at least two collecting electrodes being connected to the electrically conductive coating in the electrical heating region such that a current path for a heating current is formed between the at least two collecting conductors.

39. The method according to claim 38, wherein the separating lines are formed by laser patterning.

40. A method comprising using the pane according to claim 16 in one or more of a) means of transportation for travel on land, in the air, or on water, b) as a functional individual piece, and c) as a built-in component in furniture, appliances, and buildings.

41. The method according to claim 40, wherein a) comprises a windshield, a rear window, side panes, and/or roof panel of a motor vehicle.

42. The method according to claim 40, wherein c) comprises an electrical heater.

Description

[0087] In the following, the invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and not true to scale. The drawings in no way restrict the invention.

[0088] They depict:

[0089] FIG. 1A a top plan view of an embodiment of a pane according to the invention with an electrical heating layer,

[0090] FIG. 1B a cross-sectional view along the section line A-A′ through the pane of FIG. 1A,

[0091] FIG. 2A a top plan view of a prior art pane as a comparative example,

[0092] FIG. 2B simulation of the temperature distribution of the comparative example of FIG. 2A,

[0093] FIG. 3A a top plan view of another embodiment of a pane according to the invention,

[0094] FIG. 3B simulation of the temperature distribution of the pane according to the invention of FIG. 3A,

[0095] FIG. 4 a top plan view of another embodiment of a pane according to the invention,

[0096] FIG. 5 a top plan view of another embodiment of a pane according to the invention, and

[0097] FIG. 6 a detailed flowchart of an embodiment of the method according to the invention.

[0098] FIG. 1A depicts a top plan view of an exemplary embodiment of a pane 100 according to the invention with an electrical heating region 3. FIG. 1B depicts a cross-section through the pane 100 according to the invention of FIG. 1A along the section line A-A′. The pane 100 comprises a first pane 1 and a second pane 2, which are bonded to one another via a thermoplastic intermediate layer 4. The pane 100 is, for example, a motor vehicle pane and, in particular, the windshield of a passenger car. The first pane 1 is, for example, intended to be turned toward the interior in the installed position. The first pane 1 and the second pane 2 are made of soda lime glass. The thickness of the first pane 1 is, for example, 1.6 mm and the thickness of the second pane 2 is 2.1 mm. The thermoplastic intermediate layer 4 is made of polyvinyl butyral (PVB) and has a thickness of 0.76 mm. An electrically conductive coating 6 is applied on the inside surface Ill of the first pane 1. The electrically conductive coating 6 is a layer system that contains, for example, three electrically conductive silver layers that are separated from one another by dielectric layers. When a current flows through the electrically conductive coating 6 in the electrical heating region 3, it is heated as a result of its electrical resistance and Joule heating. The electrically conductive coating 6 can, consequently, be used for active heating of the pane 100.

[0099] The electrically conductive coating 6 extends, for example, over the entire surface Ill of the first pane 1 minus a peripheral frame-like uncoated region, the so-called edge decoating 8, with a width r of 10 mm. The edge decoating 8 serves for the electrical insulation between the voltage carrying electrically conductive coating 6 and the motor vehicle body. The region of the edge decoating 8 is hermetically sealed by adhesive bonding to the intermediate layer 4 in order to protect the electrically conductive coating 6 against damage and corrosion.

[0100] For the electrical contacting, in each case, a first collecting conductor 5.1 is arranged in the upper edge region of the pane 100 and another, second collecting conductor 5.2 is arranged in the lower edge region on the electrically conductive coating 6 in the electrical heating region 3. The collecting conductors 5.1, 5.2 contain, for example, silver particles and were applied in the screenprinting method and subsequently fired. The collecting conductors 5.1, 5.2 have, in the example depicted, a constant thickness of, for example, roughly 10 μm and a constant specific resistance of, for example, 2.3 μohm.Math.cm.

[0101] The electrical heating region 3 is electrically divided by a separating line 9 with a trapezoidal contour from the electrically conductive coating 6. This means that the separating line 9 galvanically isolates the electrically conductive coating 6 in the electrical heating region 3 from the electrically conductive coating 6. The collecting conductor 5.1 arranged on the first base 3.1 of the electrical heating region 3 has, for example, the length b.sub.1 of the first base 3.1 of the electrical heating region 3, and the collecting conductor 5.2 arranged on the lower, second base 3.2 of the electrical heating region 3 has, here, for example, the length b.sub.2 of the second base 3.2 of the electrical heating region 3.

[0102] In the exemplary embodiment depicted, the length l.sub.1 of the first base 1.1 of the first pane 1 is, for example, 900 mm and the length l.sub.2 of the second base 1.2 is, for example, 1000 mm. The ratio v of the length l.sub.1:l.sub.2 is thus v=900 mm:1000 mm=0.90:1=0.90.

[0103] In this example, the separating line 9 was selected such that the length b.sub.1 of the first base 3.1 of the electrical heating region 3 is b.sub.1=880 mm here. In other words, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 plus the width of a left and a right edge decoating of a total of 2×10 mm=20 mm corresponds to the length l.sub.1 of the shorter of the two bases of the first pane 1, in other words, l.sub.1=b.sub.1+2×10 mm.

[0104] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 is, in this example, b.sub.2=910 mm. Thus, the ratio of b.sub.1:b.sub.2=880 mm:910 mm=0.97.

[0105] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 was accordingly selected such that the ratio of the length b.sub.1:b.sub.2 with 0.97 falls within the range of v:0.99 (=0.90:0.99=0.91) to v:0.50 (=0.90:0.50=1.8). The ratio of the lengths b.sub.1:b.sub.2 is, at 0.97, actually in a preferred range according to the invention of v:0.99 (=0.90:0.99=0.91) to 0.99.

[0106] When an electrical voltage is applied on the collecting conductors 5.1, 5.2, a uniform current flows along a current path 11 through the electrically conductive coating 6 in the electrical heating region 3 between the collecting conductors 5.1, 5.2. Here, for example, a supply line 7 is arranged approx. centrally on each collecting conductor 5.1, 5.2. The supply line 7 is a foil conductor known per se. The supply line 7 is electrically conductively connected to the collecting conductor 5.1, 5.2 via a contact surface, for example, by means of a soldering compound, an electrically conductive adhesive, or by simple placement and pressure inside the pane 100. The foil conductor contains, for example, a tinned copper foil with a width of 10 mm and a thickness of 0.3 mm. Via the electrical supply lines 7, the collecting conductors 5.1, 5.2 are connected via connection cable 13 to a voltage source 14 which provides an onboard voltage customary for motor vehicles, preferably from 12 V to 15 V and, for example, roughly 14 V. Alternatively, the voltage source 14 can also have higher voltages, for example, from 35 V to 45 V and, in particular, 42 V.

[0107] By means of the selection of the ratio according to the invention of b.sub.1:b.sub.2 at 0.97, it was possible to obtain a significant improvement of the homogeneity of the heating power distribution in the electrical heating region 3, compared to a prior art pane, in which the entire electrically conductive coating 6 is heated.

[0108] FIG. 1B schematically depicts a cross-section through the pane 100 according to the invention along the section line A-A′. The separating line 9 has a width d of, for example, 100 μm and is introduced, for example, by laser patterning into the electrically conductive coating 6. Separating lines 9 with such a low width are hardly perceptible visually and disrupt vision through the pane 100 only a little, which is, particularly for an application in motor vehicles, of special importance for driving safety.

[0109] By means of an opaque color layer known per se as a blockout print, it is possible to prevent the region of the collecting conductors 5.1, 5.2 from being visible to an observer. The blockout print (not shown here) can, for example, be applied frame-like on the inside surface II of the second pane 2.

[0110] FIG. 2A depicts a prior art pane 100. The pane 100 comprises a first pane 1 and a second pane 2, which are bonded to one another via a thermoplastic intermediate layer 4. The pane 100 is, for example, a motor vehicle pane and, in particular, the windshield of a passenger car. The first pane 1 is, for example, intended to be turned toward the interior in the installed position. The first pane 1 and the second pane 2 are made of soda lime glass. The thickness of the first pane 1 is, for example, 1.6 mm and the thickness of the second pane 2 is 2.1 mm. The thermoplastic intermediate layer 4 is made of polyvinyl butyral (PVB) and has a thickness of 0.76 mm. An electrically conductive coating 6 that corresponds in structure to the electrically conductive coating 6 of FIG. 1 A is applied on the inside surface III of the first pane 1. In contrast to FIG. 1A, the second collecting conductor 5.2 arranged at the lower edge of the pane 100 in FIG. 2A has two supply lines 7 instead of only one supply line.

[0111] Moreover, the prior art pane 100 of FIG. 2A differs from the pane 100 according to the invention of FIG. 1A in that no separating lines 9 are introduced in the electrically conductive coating 6; and, consequently, the electrical heating region 3 corresponds to the entire area of the electrically conductive coating 6.

[0112] In the prior art comparative example depicted, the length l.sub.1 of the first base 1.1 of the first pane 1 is, for example, 1220 mm and the length l.sub.2 of the second base 1.2 is, for example, 1440 mm. The ratio v of the lengths l.sub.1:l.sub.2 is thus v=1220 mm:1440 mm=0.85:1=0.85.

[0113] In the prior art comparative example, the electrical heating region 3 corresponds to the entire area of the electrically conductive coating 6, since no division by a separating line is present. The length b.sub.1 of the first base 3.1 of the electrical heating region 3 is, consequently, b.sub.1=1200 mm and the length b.sub.2 of the second base 3.2 of the electrical heating region 3 is b.sub.2=1420 mm, with a width of an edge decoating 8 of r=10 mm. Thus, the ratio is b.sub.1:b.sub.2=1200 mm:1420 mm=0.85. Thus, the ratio of the lengths b.sub.1:b.sub.2, at 0.85 is outside the range according to the invention of v:0.99 (=0.85:0.99=0.86) to v:0.50 (=0.85:0.50=1.69).

[0114] In the comparative example depicted, the electrical heating layer 3 has, in the upper third of the pane and roughly central to the width of the pane, three coating-free regions 12, which can serve as communication windows.

[0115] The pane has, on the upper edge, a first collecting conductor 5.1. The current is fed through a supply line 7 into this first collecting conductor 5.1. The current flows through the electrical heating region 3 into a second collecting conductor 5.2, which is arranged in the lower region of the pane 100. The second collecting conductor 5.2 is connected at its right and its left end to one supply line 7 in each case. The collecting conductors 5.1, 5.2 have, for example, a width of 16 mm and a thickness of 10 μm. The electrically conductive coating 6 has, for example, a sheet resistance of 0.9 ohm/square. For a finite element simulation, a voltage of 14 V between the lower supply line 7 and the upper supply line 7 and an ambient temperature of 22° C. were assumed. In addition, a heating time of 12 minutes was assumed in the simulation.

[0116] FIG. 2B depicts the simulation of the temperature distribution of the prior art comparative of FIG. 2A. The positions of the supply lines 7 are indicated by arrows. The temperature distribution is nonuniform, in particular in the critical central field of vision 10. At the lower edge of the central field of vision 10, the pane 100 according to the comparative example has only a low temperature of T4=30.0° C. to 32.5° C. In the upper left and right corners, the temperature is, in contrast, in the range from T6=35.0° C. to 37.5° C. For a quick and uniform deicing and defogging function, a more uniform temperature distribution is necessary.

[0117] FIG. 3A depicts a top plan view of another embodiment of a pane 100 according to the invention. The first pane 1, the second pane 2, the electrically conductive coating 6, the thermoplastic intermediate layer 4, and the outer supply lines 7 are configured as in FIG. 2A. The essential difference relative to the prior art comparative example of FIG. 2A is that by means of a separating line 9 an electrical heating region 3 is separated from the electrically conductive coating 6. This separating line 9 limits the current flow from the first collecting conductor 5.1 to the opposing second collecting conductor 5.2. As the following simulation depicts, this makes it possible to obtain homogenization of the heating output distribution and the temperature distribution in the critical central field of vision 10 of the pane 100 according to the invention. The separating lines 9 were introduced into the electrical heating layer 3 by laser patterning. The width of the individual separating lines 9 is, for example, 100 μm, as a result of which the vision through the pane 100 and its visual appearance are only minimally affected.

[0118] In the exemplary embodiment depicted, the length l.sub.1 of the first base 1.1 of the first pane 1 is, for example, 1220 mm and the length l.sub.2 of the second base 1.2 is, for example, 1440 mm, corresponding to the comparative example of FIG. 2A. The ratio v of the lengths l.sub.1:l.sub.2 is thus v=1220 mm:1440 mm=0.85:1=0.85.

[0119] In this example, the separating line 9 was selected such that, here, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 is b.sub.1=1200 mm. In other words, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 plus the width of a left and a right edge decoating of a total of 2×10 mm=20 mm corresponds to the length l.sub.1 of the shorter of the two bases 3.1,3.2 of the first pane 1, i.e., l.sub.1=b.sub.1+2×10 mm.

[0120] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 is, in this example, likewise b.sub.2=1200 mm. Thus, the ratio of b.sub.1:b.sub.2=1200 mm:1200 mm=1.00.

[0121] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 was accordingly selected such that the ratio of the lengths b.sub.1:b.sub.2 at 1.00 lies within the range according to the invention from v:0.99 (=0.85:0.99=0.86) to v:0.50 (=0.85:0.50=1.69).

[0122] FIG. 3B depicts the stimulation of the temperature distribution of the pane 100 according to the invention of FIG. 3A. After 12 min., the entire central field of vision 10 has a uniform temperature distribution with a temperature of T5=32.5° C. to 35.0° C. In the case of weather-related icing or condensation, the complete central field of vision 10 would be completely freed of icing or condensation within a short time and unimpaired vision through the pane would be produced.

[0123] Table 1 summarizes the simulation results.

TABLE-US-00001 TABLE 1 Average specific Minimum Temperature heating power in the temperature in distribution in electrical heating the central field the central field region 3 of vision 10 of vision 10 Comparative 351.5 W/m.sup.2 30.0° C.-32.5° C. nonuniform example of FIG. and too little 2A (Prior Art) Pane 100 350.9 W/m.sup.2 32.5° C.-35.0° C. uniform and according to high the invention of FIG. 3A

[0124] The pane 100 according to the invention of FIG. 3A presents clearly improved heating properties compared to the prior art pane 100 of the comparative example of FIG. 2A. With virtually the same average specific heating power in the electrical heating region 3 of 351.5 W/m.sup.2 of the comparative example compared to 350.9 W/m.sup.2 of the pane 100 according to the invention of FIG. 3A, the pane 100 according to the invention of FIG. 3A has more uniform and higher heating of the important central field of vision 10 than the comparative example.

[0125] In particular, in the critical central field of vision 10, under the simulation conditions, the prior art pane has, on the lower edge, an extensive region with a temperature T4 from 30.0° C. to 32.5° C. and, in the upper left and right corners, a temperature from 35.0° C. to 37.5° C. This inhomogeneity results in an only unsatisfactory deicing and defogging function of the pane 100 in the central field of vision 10. The heating properties in the central field of vision 10 are insufficient to ensure quick, problem-free vision through the pane 100 under winter weather conditions.

[0126] The pane 100 according to the invention of FIG. 3A has, in the critical central field of vision 10, improved heating properties. Thus, after the same time of 12 min. as in the comparative example, simulations yielded uniform heating to an average temperature T5 from 32.5° C. to 35.0° C. over the entire central field of vision 10. By means of the small width of the separating lines 9, vision through the pane 100 according to the invention is only minimally impaired and satisfies the requirements for motor vehicle glazing.

[0127] This result was unexpected and surprising for the person skilled in the art.

[0128] FIG. 4 depicts a top plan view of another embodiment of a pane 100 according to the invention. The first pane 1 with the electrically conductive coating 6 corresponds in its structure and its dimensions to the pane 100 of FIG. 1A, wherein only the electrical heating region 3 is differently implemented by a different routing of the separating line 9. Moreover, the electrically conductive coating 6 has, in the electrical heating region 3, three coating-free regions 12, which are arranged in the upper region of the first pane 1 and roughly centrally relative to the bases 1.1,1.2.

[0129] In the exemplary embodiment depicted, the length l.sub.1 of the first base 1.1 of the first pane 1 is, for example, 900 mm and the length l.sub.2 of the second base 1.2 is, for example, 1000 mm, as already set forth in FIG. 1A. The ratio v of the lengths l.sub.1:l.sub.2 is thus v=900 mm:1000 mm=0.90:1=0.90.

[0130] In this example, the separating line 9 was selected such that, here, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 is b.sub.1=880 mm. In other words, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 plus the width of a left and a right edge decoating 8 corresponds to a total of 2×10 mm=20 mm of the length l.sub.1 of the shorter of the two bases of the first panel, i.e., l.sub.1=b.sub.1+2×10 mm.

[0131] In contrast to FIG. 1A, the length b.sub.2 of the second base 3.2 of the electrical heating region 3 in this example is b.sub.2=800 mm. Thus, the ratio is b.sub.1:b.sub.2=880 mm:800 mm=1.10.

[0132] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 was accordingly selected such that the ratio of the lengths b.sub.1:b.sub.2 at 1.10 in the region according to the invention is from v:0.99 (=0.90:0.99=0.91) to v:0.50 (=0.90:0.50=1.8).

[0133] The ratio of the lengths b.sub.1:b.sub.2 at 1.10 actually falls within the preferred range according to the invention of 1.01 to v:0.50 (=0.90:0.50=1.80).

[0134] It has been demonstrated that this solution according to the invention results in particularly homogeneous heating power distributions in electrical heating regions 3 when these have coating-free regions 12.

[0135] FIG. 5 depicts a top plan view of another embodiment of a pane 100 according to the invention. The first pane 1 with the electrically conductive coating 6 corresponds in its structure and its dimensions to the pane of FIG. 3A, wherein only the electrical heating region 3 is differently implemented by a different routing of the separating line 9.

[0136] In the exemplary embodiment depicted, the distance h.sub.1 between the collecting conductors 5.1, 5.2 in the center of the electrical heating region 3 is greater than the distance h.sub.2 between the collecting conductors 5.1, 5.2 on the outer edges of the electrical heating region 3. The distance h.sub.1 is, for example, 900 mm and the distance h.sub.2 is 800 mm.

[0137] In the exemplary embodiment depicted, the length l.sub.1 of the first base 1.1 of the first pane 1 is, for example, 1220 mm and the length l.sub.2 of the second base 1.2 is, for example, 1440 mm, as in the comparative example of FIG. 3A. The ratio v of the lengths l.sub.1:l.sub.2 is thus v=1220 mm:1440 mm=0.85:1=0.85.

[0138] In this example, the separating line 9 was selected such that, here, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 is b.sub.1=1200 mm. In other words, the length b.sub.1 of the first base 3.1 of the electrical heating region 3 plus the width of a left and a right edge decoating corresponds to a total of 2×10 mm=20 mm of the length l.sub.1 of the shorter of the two bases of the first pane 1, i.e., l.sub.1=b.sub.1+2×10 mm.

[0139] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 is, in this example, b.sub.2=1000 mm. Thus, the ratio of b.sub.1:b.sub.2=1200 mm:1000 mm=1.20.

[0140] The length b.sub.2 of the second base 3.2 of the electrical heating region 3 was accordingly selected such that the ratio of the lengths b.sub.1:b.sub.2 at 1.20 is in the range according to the invention from v:0.99 (=0.85:0.99=0.86) to v:0.50 (=0.85:0.50=1.69). Thus, the ratio of the length b.sub.1:b.sub.2 at 1.2 actually falls within a preferred range according to the invention from 1.01 to v:0.50 (=0.85:0.50=1.69).

[0141] Such a ratio of the lengths b.sub.1:b.sub.2 within the preferred range according to the invention from 1.01 to v:0.50 is particularly advantageous in electrical heating regions 3, whose distance h.sub.1 between the collecting conductors 5.1, 5.2 in the center of the electrical heating region 3 is greater than the distance h.sub.2 between the collecting conductors 5.1, 5.2 on the outer edges of the electrical heating region 3. This yields a significantly more homogeneous heating power distribution and a more uniform temperature distribution upon application of a voltage than with prior art panes, in which b.sub.1:b.sub.2 is outside the range according to the invention.

[0142] FIG. 6 depicts a flowchart of an exemplary embodiment of the method according to the invention for producing an electrically heatable pane 100.

[0143] It was possible to demonstrate that panes 100 according to the invention with separating lines 9 have significantly improved heating properties, improved homogeneity of the heating power distribution and more uniform temperature distribution with higher temperatures in particularly important regions of the pane. At the same time, vision through the pane 100 is only minimally impaired by the separating lines 9 according to the invention.

[0144] This result was unexpected and surprising for the person skilled in the art.

LIST OF REFERENCE CHARACTERS

[0145] 1 first pane [0146] 1.1 first base of the first pane 1 [0147] 1.2 second base of the first pane 1 [0148] 2 second pane [0149] 3 electrical heating region [0150] 3.1 first base of the electrical heating region 3 [0151] 3.2 second base of the electrical heating region 3 [0152] 4 thermoplastic intermediate layer [0153] 5.1,5.2 collecting conductors [0154] 6 electrically conductive coating [0155] 7 supply line [0156] 8 edge decoating [0157] 9 separating line [0158] 10 region [0159] 11 current path [0160] 12 coating-free region [0161] 13 connection cable [0162] 14 voltage source [0163] 100 pane [0164] II surface of the second pane 2 [0165] III surface of the first pane 1 [0166] b.sub.1, b.sub.2 length of the base of the electrical heating region 3 [0167] d width of the separating line 9 [0168] l.sub.1, l.sub.2 length of the base of the first pane 1 [0169] h.sub.1, h.sub.2 height of the electrical heating region 3 [0170] r width of the edge decoating 8 [0171] A-A′ section line