WO1991010564A1

WO1991010564A1 - Heatable windscreen

Info

Publication number: WO1991010564A1
Application number: PCT/DE1991/000022
Authority: WO
Inventors: Roland Müller; Werner Müller; Wolfgang Siefert
Original assignee: Renker Gmbh & Co Kg
Priority date: 1990-01-15
Filing date: 1991-01-12
Publication date: 1991-07-25

Abstract

The invention concerns a heatable vehicle windscreen with a transparent, electrically conducting coating having simultaneously produced zones (6, 7, 10) of different surface resistance and with different optical properties, the individual zones (6, 7, 10) being optimized for a high degree of transparency (6) or a high degree of protection against the sun's rays (10) or high heating capability (7).

Description

Heated pane

The invention relates to a heatable pane with a sequence of layers for achieving a high transmissivity in the visible spectral range and a high reflectivity in the infrared spectral range. The pane due to the low surface resistance of the layer sequence having a metal layer between two oxide layers by application an electrical power source is heated.

The published patent application DE 38 25 671 A1 describes a pane with a high transmission behavior in the visible spectral range and high reflection behavior for heat radiation of the type mentioned at the outset, the sequence of layers of which has a low electrical resistance, so that the pane by applying an electrical current source is heated. It is also known from this document to process such panes with a further uncoated pane to form sandwich panes which are particularly suitable for use in motor vehicles as a heated front or rear pane with an additional protective function against intensive solar radiation. In the case of laminated glass panes of this type, a tough-elastic intermediate layer made of a plastic, for example polyvinyl butyrate, is located between the two thin panes of mineral glass.

Heated front and rear windows with inserted heating wires that run horizontally or vertically are also known (DE 32 26 393 A1). Compared to a heatable pane of the type mentioned at the outset, however, these have the disadvantage that the heating wires are visible and visually disturb. There are also between the individual heating wires undesirable temperature fluctuations. Another disadvantage of such heating disks is that they do not offer sun protection. However, if localized heating is only desired in the area of the windshield wipers, heatable windshields with heating wires are more effective than the heatable windshield which is homogeneously heated over a large area.

The object of the invention is to create a heatable pane of the type mentioned at the outset, which combines the contradictory demands for high transparency in the visible spectral range, high sun protection in the infrared spectral range and high heating power.

This object is achieved according to the invention in that the pane has a plurality of regions which have the same properties in the horizontal direction in the installed state, gradients in the surface resistance being provided between these regions in the vertical direction.

The heatable pane has a sun visor area, a transparency area and a wiper area, each of which is optimized with regard to its optical and electrical properties. In this way, the requirements for maximum sun protection on the entire windshield, a transmission of more than 75 percent on a defined area of the windshield and effective heatability, in particular in the area of the stationary windshield wipers, are met. In one embodiment, the pane is provided with an upper contact path at the upper edge and with a lower contact path at the lower edge, the surface resistance in the windshield wiper region adjacent to the lower contact path having the highest surface resistance and the smallest in the sun visor region adjacent to the upper contact path and the surface resistance has an average value in the transparency range optimized for the transmission.

If the windshield is to be used essentially in countries with a lot of sunshine, it is advantageous if the windshield is provided with lateral contact strips on the right and left edge and the surface resistance of the coating in the windshield wiper area is lower than in the other areas is.

The arrangement can be such that the lateral contact strips do not extend to the sun visor area. In particular, the lateral contact strips can only extend along the windshield wiper region. The surface resistance in such an arrangement is larger in the transparency area and smaller in the sun visor area than in the windshield wiper area.

In another expedient embodiment, it is provided that the lateral contact strips only extend along the windshield wiper region and the transparency region, a high-resistance narrow separation zone extending horizontally into the contact strips being provided between these regions. The heatable pane can be produced in that the sequence of layers is applied to a glass pane serving as a substrate by sputtering. Alternatively, it is possible for the sequence of layers to be applied to a plastic film serving as a substrate by sputtering, which is laminated between two glass panes. In an expedient embodiment of the invention, the coated plastic film consists of polyester and is covered on both sides by a polyvinyl butyrate film and a glass pane.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing. Show it:

1 is a heatable disc with upper and lower contact tracks according to the invention in a view,

FIG. 2 shows a heatable pane with lateral contact strips in a representation corresponding to FIG. 1,

3 shows a heatable windshield which is modified compared to the heatable windshield according to FIG. 2 and has lateral contact strips only in the windshield wiper region,

4 shows a heatable pane in a representation corresponding to the preceding figures with lateral contact strips which are segmented by a separation zone between the pane wiper area and the transparency area for connection to two different current sources, 5 shows a heatable pane with lateral contact strips which extend laterally along the pane wiper area and the transparency area without interruption,

6 shows a schematic perspective illustration to illustrate the layer sequence on a substrate,

7 shows a schematic illustration for illustrating a cover panel for the material source of a device for cathode sputtering, which allows inhomogeneous coating in the vertical direction of a heatable pane for the simultaneous generation of all areas, and

Fig. 8 shows a heatable disc with segmented upper and lower contact tracks in a view.

1 shows a heatable pane which is provided with the overall reference number 1 and, due to its design, is designed in particular for colder zones in the northern part of Europe. The disc 1 extends between an upper edge 2 and a lower edge 3 and between a left edge 4 and a right edge 5. It can be bent in the manner shown in the drawing. Of course, it can also have a different and in particular a flat shape.

According to the regulations, the window has a transparency area 6 in the driver's field of vision with a transmission of more than 75 percent in the visible spectral range. The pane 1 preferably has a structure of several layers, a polyester film, which has a transparent, electrically conductive coating with a layer sequence of an oxide, metal and an oxide, being laminated between two glass panes with the interposition of polyvinyl butyrate plastic films . However, the transparent, electrically conductive layer sequence provided on the polyester film can also be applied directly to the glass of the pane 1.

In the transparency area 6, the transparent, electrically conductive layer composed of the layer sequence oxide-metal-oxide is homogeneously formed and has a surface resistance of 6 to 7 ohms per square, for example a solar energy transmission of 52 percent and a light transmission of 76 percent . The high transparency is achieved in that the highly reflective metal layer is reflected in the visible spectral range by a suitable choice of the thickness and the refractive index of the oxide used. If the oxide and metal layers are applied by sputtering or sputtering, the refractive index and the stoichiometry of the oxides can be influenced in the desired manner by changing the oxygen content and the reactive gas supply.

In order to achieve maximum transmission, a stoichiometry adjustment is also preferably carried out when the oxides are deposited together with a layer thickness adjustment.

While in the transparency area 6 an optimization with regard to the transparency in the visible is carried out, In the windshield wiper region 7 lying between the transparency region 6 and the lower edge 3, the heating output of the heatable windshield 1 is optimized. The demands for high transparency, high sun protection and high heating output are in opposite directions. For this reason, the disc 1 is divided into areas which are each optimized in terms of their function.

The windshield wiper region 7 has a layer structure which corresponds to the structure in the transparency region 6, but the coating is optimized with regard to the thickness of the individual layers of the transparent, electrically conductive layer and the stoichiometry of the oxides from the point of view of the heating power, with a high reflection and a Surface resistance of more than 7 ohms per square, for example 10 to 12 ohms per square, results. The highest heating output is required in the windshield wiper region 7, since most of the heating energy is required there to defrost the windshield wipers frozen in the rest position or to clear them of snow and ice.

The windshield wiper region 7 extends approximately to the boundary line 8 shown in dashed lines in FIG. 1. In the region of the boundary line 8 there is a transition in the surface resistance of the coating in the vertical direction, the optical properties only being relatively slow despite the gradient in the surface resistance change to avoid a visible dividing line.

At the upper edge, the transparency area 6 is delimited by a border line 9, which is likewise not visible to the driver, since the optical properties between the transparency area 6 and the sun lens the area 10 also change not visibly by leaps and bounds.

In the sun visor area 10, the layer structure is optimized with regard to the desired sun protection. In order to achieve a high level of sun protection, the layer structure is selected such that a solar energy transmission of approximately 20 to 25 percent with a light transmission of 45 to 50 percent and a surface resistance of 2 ohms per square meter is present.

It follows from the above discussion that the surface resistance is highest in the windshield wiper region 7 and smallest in the sun visor region 10, while it has an average value in the transparency region 6.

In the drawing, an upper contact path 11 can be seen at the upper edge 2 and a lower contact path 12 at the lower edge 3. The contact paths 11, 12 serve to connect electrical lines, not shown in the drawing, via which electrical current for heating the disc 1 is fed. The electrical resistance of the contact tracks 11, 12 is negligible compared to the resistance of the metal coating of the heatable disc 1. Since the electrical current flows serially through the sun visor area 10, the transparency area 6 and the windshield wiper area 7, the highest voltage drop and thus the highest heating output also result in the windshield wiper area with the highest surface resistance. Heating is at least carried out in the sun visor area 10 with the smallest surface resistance, and in the transmission area 6, with the selective heating provided in this way, there is medium heating, which is used for evaporation of moisture and for defrosting a thin layer of ice.

As can be seen from the above description, the surface resistance of the metal coating of the heatable disk 1 increases from the upper edge 2 to the lower edge 3, a positive gradient in the surface resistance thus being present. In the example described, the course of the resistance function is step-like with three levels, with a relatively steep transition between the levels. Instead of a staircase function in the sheet resistance, however, the coating can also be provided such that the resistance curve increases linearly from the upper edge 2 to the lower edge 3 or has a curve lying between these extremes.

The heatable windshield 1 described above permits locally different (selective) heating of a windshield, which can be designed as an automobile windshield or as a rear window. The heating thaws an ice layer, evaporates a moisture film and / or prevents the formation of both. The greatest heating power is in the lower pane area, i.e. H. present in the rest position of the windshield wipers or in the windshield wiper region 7.

The pane 1 has a full-surface coating that is transparent and electrically conductive, wherein it has a defined gradient in the sheet resistance in the vertical direction over the pane surface. The coating can either be applied directly on a glass pane or on a film. be seen that is laminated between glass panes.

If the contact tracks 11, 12 are arranged at the top and bottom in the manner shown in FIG. 1, the higher resistance in the lower part of the disk 1, i. H. be provided in the wiper area 7.

If the contact tracks are attached laterally, as shown in Fig. 2, the lower resistance in the lower region, i. H. be provided in the wiper area 27.

FIG. 2 shows a heatable pane 21 with a left contact path 13 and a right contact path 14. As in the exemplary embodiment according to FIG. 1, the pane provided with the reference symbol 21 has a transparent, electrically conductive and inhomogeneous coating in some areas, as in the case of the 1, different areas are provided. A windshield wiper region 27 extends between the lower edge 23 and a boundary line 28, but has a low surface resistance compared to the exemplary embodiment according to FIG. 1. Between the boundary line 28 and a boundary line 29 lying further up there is the transmission region 26 with an average surface resistance. In the direction of the upper edge 22, the upper limit line 29 is followed by the sun visor area 30, which also has an average surface resistance. With regard to the optical properties, the transparency region 26 between the boundary lines 28 and 29, which are not visible, has a high transmission for visible light. The sun visor area 30 is optimized in terms of its optical properties as sun protection. The disc Wiper area 27 is optimally designed with regard to its heating power.

If a voltage is applied between the left contact path 13 and the right contact path 14, the sun visor region 30, the transparency region 26 and the windshield wiper region 27 are electrically parallel, the highest current flowing there because of the lower surface resistance in the windshield wiper region 27 and thus the highest heat output there and heating power is present.

The gradient with respect to the surface resistances in the above-mentioned exemplary embodiments and in the exemplary embodiments described below is set such that no mechanical stresses occur as a result of large temperature differences. Transparent, electrically conductive layers with a high transparency of more than 80 percent and a low surface resistance of less than 10 ohms per square meter typically have the structure already mentioned above with a layer sequence of oxide, metal and oxide.

Such a structure is shown schematically in FIG. 6. Glass or a polyester film 31, which has a thickness of, for example, 50 micrometers, can be used directly as the substrate. With the aid of a plant for cathode sputtering, for thermal evaporation, for chemical vapor deposition, in particular a plasma-assisted chemical vapor deposition, or for plasma polymerization, an oxide layer 32 of 20 to 50 nanometers is applied to the polyester film. This can be, in particular, Sn0 ₂ , In ₂ 0 ₃ , Bi ₂ 0 ₃ , Nb ₂ 0 ₅ or Ti0 ₂ . As the next layer in the layer A thin metal layer 33 with a thickness of 10 to 30 nanometers is provided. Silver, gold or copper can be used as the metal. An oxide layer 34 with a thickness of 20 to 50 nanometers follows the metal layer 33. The choice of the thickness and the refractive index of the oxides makes it possible to antireflect the highly reflective metal layer 33 in the visible in order to achieve high transmission. The refractive index can be changed by the oxygen content of the oxide in the above-mentioned processes, in particular reactive sputtering or cathode sputtering.

In order to achieve the desired gradient in the sheet resistance of the metal layer 33, cathode sputtering between the material source 35 or target shown schematically in a plan view in FIG. 7 and the substrate to be coated, i. H. A shield is attached to the polyester film 31 or the glass pane, which consists of the two sheets 36, 37 shown in FIG. 7 with an intermediate space 38 which allows different amounts of layer material of the material source 35 to pass along its length and thus along the Width of the space 38 leads to different layer thicknesses when coating the polyester film 31 or the glass.

In order to achieve the maximum transmission along the resistance gradient, it is necessary to adapt the stoichiometry of the oxides in addition to the layer thickness adjustment when the oxides are deposited, which can be achieved by means of a defined, different supply of reactive gas over the coating width. In addition to the above-mentioned possibility of producing a resistance gradient transverse to the running direction of the substrate with the aid of a defined covering of the material source 35, it is also possible to provide a constant resistance transverse to the running direction of the substrate and the gradient of the surface resistance in the running direction of the substrate, in particular the Form polyester film 31. This can be achieved by changing the coating rate in a cathode sputtering or sputtering system in a computer-controlled manner by influencing the sputtering performance. In the case of series production, a gradient cycle then results synchronously with the web speed of the substrate, the regions mentioned in connection with FIGS. 1 and 2 being generated sequentially within each cycle. Such a solution has the advantage of lower material consumption since no material is caught by the cover panels 36, 37 of the shield.

FIG. 3 shows a further example of a heatable pane 41 with three areas that have been optimized in each case. In the middle area of the heatable pane 41 there is again a transparency area 46 with a light transmission of more than 75 percent in the visible spectral area. The surface resistance in the transparency area 46 is higher than in the underlying wiper area 47, which is provided with short lateral contact strips 43 and 44 and has an average surface resistance.

The transparent, electrically conductive coating in the embodiment shown in FIG. 3 in the sun visor area 50 is in turn adapted for particularly high sun protection. The sheet resistance in the solar The aperture area 50 is smaller than in the windshield wiper area 47. The surface resistance in the transparency area 46 is higher in the embodiment shown in FIG. 3 than in the windshield wiper area 47.

The embodiment of a heatable window 41 shown in FIG. 3 combines the advantages of a particularly high level of sun protection with a selective heating in the area of the window wiper blades that is gentle on the battery. Since the lateral contact strips 43, 44 are only present in the vicinity of the lower edge 3, the heating output is limited.

If the transparent, conductive layer is produced with a gradient by changing the coating rate, the running direction of the substrate and in particular the substrate film or the polyester film 31 is parallel to the contact strips 43, 44. If the above-described gradient film is covered by means of a Shield 36, 37 is produced, the running direction of the substrate in Fig. 3 is transverse to the contact strips 43, 44th

The layers of the gradient layer are adjusted in such a way that no jumps in transparency occur in the area of the boundary lines 8, 9, which can lead to irritation of the eye.

4 shows a further exemplary embodiment of a heatable pane with a transparent, electrically conductive layer which, instead of a homogeneous sheet resistance, has a sheet resistance which changes in the vertical direction of the sheet and can therefore also be referred to as a gradient layer or gradient film. In the exemplary embodiment of a heatable pane 51 shown in FIG. 4, a sun visor area 60 is provided, in which the transparent, electrically conductive layer has the highest metal layer thickness and the highest oxide layer thickness. As can be seen in FIG. 4, the sun visor area 60 has no electrical connection.

Between the sun visor area 60 and the underlying transparency area 56 as well as the transparency area 56 and the windshield wiper area 57 there is in each case a narrow separation zone 59 which is not recognizable to the eye and has a very high resistance to galvanic separation. In the vertical direction downward, the transparency region 56 follows with a very small metal layer thickness and oxide layer thickness. The heating power in the transparency area 56 is small, but it is sufficient to keep the pane 51 free of fogging in this area.

The transparency area 56 has its own transparency area contact tracks 53 and 54, which are attached to the sides of the transparency area 56 in the manner shown and are fed by a first circuit.

A second circuit is connected to the shorter contact strips 63, 64 which can be seen in FIG. 4 and which are assigned to a second heating circuit, by means of which the windshield wiper region 57 of the windshield 51 is heated. The windshield wiper region 57 generates a high heating power and has a small surface resistance. The metal layer thickness lies between the high metal layer thickness in the sun visor area and the small metal layer thickness in the transparency area 56.

Another example of a heatable disk 61 with a gradient film is illustrated in FIG. 5. The heating disk 61 shown there is particularly useful for areas with a climate such as that found in southern Europe.

The heating disk 61 has a sun visor area 70 with high sun protection. A separation zone 69 can be provided between the sun visor area 70 and the transparency area 66 with high transparency in order to electrically separate the sun visor area 70 from the rest of the pane 61. At the bottom, the transparency area 66, which should also offer the highest possible sun protection, is followed by a windshield wiper area 67 with a high heating power and a high reflection.

As can be seen in FIG. 5, a left contact path 71 and a right contact path 72 extend along the sides of the pane 61, but there is no contacting of the sun visor region 70.

The exemplary embodiments described above bring a solution to the opposing demands for high transparency, high sun protection and high performance. For this purpose, the pane 1, 21, 41, 51 or 61 is optimized in different segments or areas in the manner described above for either high transparency or high sun protection or high heating power, so that these opposing requirements can be optimized much better in the individual segments. The segment prescribed by law with high Transparency of more than 75 percent can be coated homogeneously, which leads to the values mentioned in connection with FIG. 1. The other areas of the panes 1, 21, 41, 51 and 61 can be optimally adapted to the required high sun protection and the heating power.

The discs according to the invention can be produced in such a way that, when coating in a system, the gradient is produced transversely to the feed direction of the substrate 31 by providing the material source 35 with suitably shaped cover plates 36, 37. Alternatively, it is possible to produce the gradient in the feed direction of the substrate 21 when coating in a system by changing the coating rate in a defined manner within continuously successive cycles.

FIG. 8 shows a modification of the heatable disk shown in FIG. 1 with upper and lower contact tracks. The embodiment shown in FIG. 8 differs from the exemplary embodiment described in connection with FIG. 1 in that, instead of a continuous upper contact track 11, an upper contact track 110 divided into two or more segments 111, 211 is provided. The mutually insulated segments 111 and 211 can, for example, each extend over the left and right half of the pane. It is also possible to use segments 111, 211 of different lengths, in order to be able to supply different areas of the pane with heating current.

Instead of a continuous lower contact track 12, the disk 1 shown in FIG. 8 has one lower contact path 120, which is divided into segments 112 and 212 which are insulated from one another. The segmentation of the lower contact path 120 into two or more segments 112, 212 corresponds to the segmentation of the upper contact path 110.

The disk 1 shown in FIG. 8 is otherwise constructed like the disk 1 described in connection with FIG. 1, which is why the same reference numerals have been used in FIG. 8 for the features already discussed as in FIG. 1. The segmentation of the upper one Contact track 110 and the lower contact track 120 allow, for example, a higher heating current to be provided on the driver side than on the passenger side. In this way, the heating power can be concentrated on a part of the pane 1.

Claims

PATENT CLAIMS

1. A heatable pane with a sequence of layers to achieve a high transmission capacity in the visible spectral range and a high reflectivity in the infrared spectral range, the pane being heatable by applying an electrical current source due to the low surface resistance of the layer sequence having a metal layer between two oxide layers. characterized in that the disc (1, 21, 41, 51, 61) has several properties (6, 7, 10; 26, 27, 30; 46, 47, 50) that have the same properties in the horizontal direction when installed ; 56, 57, 60; 66, 67, 70), whereby in the vertical direction between these areas (6, 7, 10; 26, 27, 30; 46, 47, 50; 56, 57, 60; 66 , 67, 70) gradients in the sheet resistance are provided.

2. Window according to claim 1, characterized in that the window has a sun visor area (10, 30, 50, 60, 70), a transparency area (6, 26, 46, 56, 66) and a wiper area (7, 27, 47, 57, 67), which are each optimized with regard to their optical and electrical properties.

3. Disc according to claim 1 or 2, characterized gekenn¬ characterized in that the disc (1) at the top. (2) with an upper contact track (11) and at the lower edge (3) with a lower contact track (12), the surface resistance in the lower contact track (12) adjacent wiper area (7) has the highest and in the upper contact track (11) adjacent sun visor area (10) has the smallest sheet resistance, the sheet resistance in the transparency area (6) optimized for transmission in one middle range.

4. Disc according to claim 1 or 2, characterized gekenn¬ characterized in that the disc (21) on the right and left edge with side contact strips (13, 14, 43, 44, 53, 63) is provided and the surface resistance of the coating in the windshield wiper area (27, 47, 57) is smaller than in the other areas (26, 30; 46, 50; 56, 60).

5. Window according to claim 4, characterized in that the lateral contact strips (43, 44) extend only along the window wiper region (47).

6. Window according to claim 5, characterized in that the surface resistance in the transparency area (46) is larger and in the sun visor area (50) is smaller than in the wiper area (47).

7. Window according to claim 4, characterized in that the lateral contact strips (53, 54, 63, 64) only extend along the wiper area (57) and the transparency area (56).

8. Window according to claim 7, characterized in that between the windshield wiper area (57) and the transparency area (56) up to Contact strip (53, 63; 54, 64) extending into the high-resistance narrow separation zone (59) is provided.

9. Disc according to one of the preceding claims, characterized in that the sequence of layers is applied to a glass pane serving as a substrate by sputtering.

10. Disc according to one of claims 1 to 8, characterized in that the sequence of layers on a plastic film serving as a substrate (31) is applied by sputtering, which is laminated between two discs.

11. A pane according to claim 10, characterized in that the coated Kunststoffol e consists of polyester (31) and is covered on both sides by a polyvinyl butyral film and a glass pane.

12. Disc according to one of claims 1 to 11, characterized in that when coating in a system the gradient is produced transversely to the feed direction of the substrate (31) by the material source (35) with suitably shaped cover plates (36, 37) is provided.

13. Disc according to one of claims 1 to 11, characterized in that, when coating in a system, the gradient in the feed direction of the substrate (31) is produced by the coating rate being changed in a defined manner within continuously successive cycles.

14. Disc according to one of claims 1 to 3, characterized in that an upper contact track (110) with contact track segments (111, 212) and a lower contact track (120) with segments (112, 212) is provided at the upper edge .

15. Disc according to one of claims 1 to 14, da¬ characterized in that the two oxide layers (32, 34) of the layer sequence have as the main component or exclusively niobium oxide.