LU87797A1 - HEATING MIRROR - Google Patents

Description

CLAIM OF THE PRIORITY of the patent application / utility model Brief Description filed in support of an application for

PATENT OF INVENTION at

Luxembourg

in the name of: GLAVERBEL

Chaussée de la Hulpe, 166 B-1170 BRUSSELS (Watermael-Boitsfort)

Belgium for: "Heated mirror"

Heated mirror.

The present invention relates to a heating mirror comprising an opaque metallic coating reflecting light in a specular manner deposited on a transparent sheet of glass.

Known heating mirrors have a heating network, which extends over most of the surface of the mirror, in which a circulation of electric current develops heat by the Joule effect. This heat is distributed over the entire surface of the mirror so that each point on the surface accessible to the touch is at a temperature not too high to avoid any risk of burns. Heated mirrors serve two different functions. In addition to their primary function of reflecting light rays like any mirror, they also give off heat. A classic example is that of heated bathroom mirrors in which slight heating is provided to remove the fogging that forms on the front of the mirror.

When these heating mirrors are powered by a very low voltage electric current source, for example 24 V, they present practically no danger to people and in particular no danger of electric shock. However, the supply of very low voltage in homes requires a transformation of the mains voltage, which leads to the presence of additional expensive and bulky equipment. In addition, if the heating power required is relatively high, the very low voltage supply requires the circulation of an electric current of high intensity, which poses problems of electrical connection and sufficient size of the collectors. The supply of the heating mirrors under the usual mains voltage, for example 220 V, reduces the intensity of the electric supply current, but requires an electrical safety check for the users. This can create difficulties when the heating mirror must give off enough heat to give a comfortable temperature to a room and operate in a humid environment, such as for example a bathroom.

The known heated mirrors do not meet the strict safety standards which currently govern the field of the use of electricity in a humid environment. The object of the present invention is an opaque panel acting as a mirror and as a heat source while having high protection against electric shock. The invention relates to a laminated heating mirror comprising a specular light-reflecting metallic coating deposited on a transparent glass sheet, characterized in that it comprises at least two sheets of glass secured by laminating using an intermediate polymeric material, one of the sheets of which carries, on its face oriented towards said polymeric material, an electrically conductive layer, electrically insulated from the external surface of the mirror, and two current collectors each connected to a conductive element of electricity for connection to the electrical power source, in that at least one of said conductive elements (hereinafter called "first conductive element") passes through at least part of said polymeric material and extends, inside the mirror, up to the immediate vicinity of the end of the other conductive element in a single connection zone ment located at the periphery of the mirror, and in that the edge of the polymeric material and the conductive layer are surrounded by electrically insulating material.

The heating mirror according to the invention facilitates the electrical connection to the supply sector in good safety conditions by the fact that the two supply wires can be connected in the same area since the connection end of the two conductive elements are in close proximity to each other, which facilitates connection using a single power cord with double electrical insulation. The entire electrical circuit is isolated inside the laminated panel. In addition, the presence of electrically insulating material which covers the edge of the polymeric material and which extends along the periphery of the laminate contributes to the production of additional insulation. It is thus possible to form an electric heating circuit having a heating surface as large as possible relative to the surface of the laminate and having double electrical insulation. On the other hand, by the fact that the conductive layer and the entire electrical circuit, except for the connection ends of the two conductive elements, are sandwiched inside the laminated assembly formed by the two sheets secured by polymer material, electrical safety can be maintained even in case of breakage of the sheets because the pieces will be held in place by the polymer material. The expression “double insulation” is used in the present description to mean the presence of additional independent insulation, in addition to the functional or main insulation, in order to continue to provide protection against electric shock in the event of failure. of functional insulation. The functional or main insulation is the insulation necessary to ensure the proper functioning of the device and the fundamental protection of people against electric shock.

It is surprising to be able to manufacture a laminated assembly according to the usual technique while the heating circuit and the electrical supply circuit are sealed inside the laminate, while providing a laminated mirror of high optical and mechanical quality. It is also surprising to obtain a laminated assembly which does not delaminate during the functional and accelerated aging tests when it comprises elements made of materials with different coefficient of thermal expansion and the largest possible heating surface.

Preferably, said first conductive element is embedded in said polymeric material. This arrangement of the path of the conductive element facilitates electrical insulation, which allows for example the presence of a reflective coating conductive of electricity in contact with the polymeric material. In all cases, this arrangement of the path of the conductive element promotes the lamination of the sheets to form the mirror.

The connection zone intended for the electrical connection can be, for example, in the center of one of the sides of the mirror, if the latter is of polygonal shape. The mirror can also be in the form of a circle and the connection zone will therefore be located at a location on the circumference. Preferably, however, the mirror is rectangular, the collectors extend along two opposite sides of the rectangle and said connection zone is located in a corner of the mirror. Using a simple electrical circuit, only the first conductive element must pass through the polymeric material and follow a relatively long path inside the laminate to transfer the electric current between the corresponding collector and the connection zone, because a end of the other collector can directly end near said corner, so that its corresponding conductive element can be very short.

In this embodiment, at the location of said connection zone, the corner of one of the glass sheets is preferably cut to allow the passage of the supply wires, and the connection of these to the said elements. conductors is embedded in an insulating material. The electrical connection is thus facilitated and double electrical insulation of the connection terminals can be more easily established with an acceptable aesthetic appearance. We can for example glue a piece of glass that covers the insulating material, to complete the double electrical insulation.

Preferably, at least the said conductive element comprises a flat metallic strip, which is advantageously a Cu strip, which allows the passage of a high intensity of electric current without excess thickness capable of disturbing the joining of the glass sheets. The collectors can be formed using a conductive lacquer, for example a silver lacquer, deposited by screen printing, and the conductive element formed by the Cu strip is brought into electrical contact with this conductive lacquer. A cut is made in the polymer material film to pass the Cu strip before the lamination operation.

The conductive layer can be deposited uniformly over the entire surface of a glass sheet and, to facilitate electrical insulation of the edges of the laminate, a groove can be made in the conductive layer all along the periphery, for example at 1 cm from the edge, so as to electrically isolate the marginal part from the rest of the layer. However, it is preferred that the surface of the sheet carrying said conductive layer has a marginal zone greater than 1 cm, preferably greater than 1.5 cm, devoid of any conductive material, which extends substantially along its entire periphery. High electrical insulation of the laminated edge is thus more easily obtained and preserved over time, especially in a humid environment. It is advantageous to leave a marginal area of 2 cm devoid of any electrically conductive material over the entire periphery of the sheet. For this, the conductive layer can be uniformly deposited over the entire surface of the sheet, then the marginal part is removed, for example using an abrasive wheel. One can also have a cover on the marginal part of the sheet before depositing the layer, for example by spraying. This cover prevents the formation of the layer on the glass where it is placed. It is for example formed by an adhesive strip or a paint which crumbles under the action of heat.

The conductive layer can be formed, for example, by gold, silver or copper deposited by sputtering under vacuum. It can also be formed from a metal deposited chemically or electrochemically. Preferably, the conductive layer is a layer of doped tin oxide. The doped tin oxide can form, on a glass sheet, a very hard heating layer which is easily obtained by pyrolysis, in a manner known per se. This layer is resistant to handling and therefore to lamination operations.

Preferably, the reflective coating is deposited on a first sheet of glass and is formed from a layer based on silver and / or copper which is electrically insulated from the conductive layer carried by another sheet by means of a paint. protective heat resistant and said polymeric material. The heat resistant paint improves the aging resistance of the heating mirror by ensuring the protection of the reflective coating despite the rise in temperature of the laminated assembly. The paint and polymer material assembly also ensures adequate insulation of the electrical heating circuit.

Advantageously, the two glass sheets have undergone a treatment for strengthening their mechanical strength. It may for example be a thermal quenching treatment. These sheets thus more easily resist the thermal shock created by a projection of drops of cold water on their surface when the latter is hot, which further improves electrical safety by preserving the integrity of the laminate.

Preferably, the glass sheet carrying the reflective coating is a glass sheet having undergone a chemical toughening treatment. The glass sheet carrying the reflective coating is a front sheet of the installed mirror since the primary function of a mirror is the specular reflection of light so as to generate a reflection, that of a face for example. Chemical toughening gives the glass sheet a very high impact resistance allowing it to withstand possible mechanical and thermal shocks. In addition, chemical quenching can be carried out on a thin sheet, which promotes the formation of a lighter mirror.

Preferably, the glass sheet carrying the reflective coating has a thickness of less than 3 mm, for example 2 mm. This small thickness limits the thermal insulation formed by the front glass sheet.

Preferably, the glass sheet carrying the conductive layer is a thermally hardened glass sheet. This mechanical reinforcement treatment can be obtained economically and it is easily compatible with the deposition of a layer by pyrolysis, for example.

Preferably, the mirror according to the invention comprises, on its external face, on the side which does not reflect light in a specular manner, a layer with low emissivity. The dorsal side of the mirror being weakly emissive, it is thus possible to reduce heat losses, by radiation towards the wall on which the mirror is fixed.

The edge of the mirror is preferably at least partially covered with electrically insulating and waterproof material to prevent the entry of moisture between the sheets. This joint improves the resistance over time, under humid conditions of use, of the electrical insulation between the conductive layer and the edge of the laminate. Advantageously, a silicone-based seal can be used.

In a first embodiment, the mirror according to the invention is surrounded by a metal frame, for example aluminum, or a plastic material, for example PVC. The presence of electrically insulating material along the periphery of the laminate ensures double insulation allowing the use of a metal frame, special care will however be taken to maintain double electrical insulation of the connection area with respect to the frame . The space between the frame and the edge of the laminate can be used to improve resistance to moisture penetration, as explained above, by placing a tight seal therein.

In a second embodiment, the sheet carrying the reflective coating is larger than another sheet which is secured to it, leaving a margin all along the periphery of the mirror. In this embodiment, the mirror has no frame and can therefore be produced more economically. The margin may be bordered by a rigid self-adhesive foam of plastic material, for example a polyurethane foam, and the space between this border and the edge of the laminate will be filled with the gasket of electrically insulating material, preferably a material impervious to water. water, such as silicone for example.

Preferably, the heating power of the mirror according to the invention is 2 2 greater than 500 W / m, and advantageously greater than 700 W / m. Such a heating power makes it possible to use the mirror according to the invention to provide heating, or supplementary heating, of a small room such as a bathroom. A power of 800 W / m advantageously ensures this heating without the risk of causing a dangerously high surface temperature of the front face of the mirror. The adaptation of the resistance per square of the conductive layer to obtain the desired specific power can be easily carried out, depending on the dimensions of the mirror, by adjusting the thickness of this layer, for a layer of given composition. One can also easily modify the specific conductivity by modifying the doping if the layer is formed by a semiconductor. By combining the two adjustment possibilities, it is possible to vary the resistance per square from 50 ohm to 1000 ohm

The collectors can be formed by spraying Cu with a flame, either directly on the glass before deposition of the layer, or after deposition of the layer. Advantageously, at least one of the collectors is formed by two strips of electrically conductive lacquer superimposed between which an edge of the conductive layer is sandwiched. This arrangement makes it possible to obtain a high electrical conduction which is preserved over time despite the circulation of a relatively intense current. In addition, the conductive lacquer can easily be applied according to the current screen printing technique.

The present invention will now be described, by way of example only, with reference to the appended figures in which:

Figure 1 is a partial plan view of the dorsal side of an embodiment of the heating mirror according to the invention;

Figures 2 and 3 are partial sections of the heating mirror according to Figure 1 viewed from the positions indicated by lines A-A 'and B-B' in Figure 1;

Figure 4 is a perspective view of a corner of the mirror of Figure 1 before its framing and before deposition of the insulating material on the edge of the interlayer polymeric material; and

Figure 5 is a partial section of another embodiment of the heating mirror according to the invention.

The heating mirror shown in Figures 1 to 4 comprises a laminated assembly 1 consisting of a glass sheet 2, carrying an opaque metallic coating 3 reflecting light in a specular manner, secured by laminating to a glass sheet 4 using an interlayer polymeric material formed by two films 5 and 6. It should be noted that the drawings are not to scale. It should also be noted that the two films 5 and 6 of interlayer polymeric material are drawn separately to facilitate understanding, while in the finished laminate these films are practically welded in a single layer of interlayer polymeric material. The glass sheet 4 carries a conductive layer 7 extending between two collectors 8 and 9. The collector 8 is formed by a strip of conductive lacquer 10 deposited on the edge of the conductive layer 7. In the embodiment shown, the first electrically conductive element is formed by a strip of Cu, one end of which extends over the entire length of the collector 8 and is held there in electrical contact to increase the electrical conductivity of the collector, and which extends under shape of the strip 12, up to a connection area 13. In this embodiment, the connection area 13 is located in a corner of the mirror. The strip 12 of the first conducting element crosses the sheet 6 of polymeric material at the location indicated by the reference 14 in FIG. 1 and follows a path situated between the films 5 and 6 of polymeric material as shown in FIG. 3, therefore located inside the laminate, up to the single connection area 13. The electrical connection of the collector 8 is thus carried out, via the strip 12 of the first conductive element, in the same connection area 13 as the electrical connection of the collector 9. The collector 9 is also formed of a lacquer strip on which an Cu strip has been placed in electrical contact, which extends over the entire length of the collector, in order to increase the electrical conductivity of the collector. This Cu strip extends in the form of the conductive element 30 to the connection zone 13. The electric supply cord 15 with double insulation, comprising two conductive wires, is connected to the strip 12 of the first conductive element and to the second conductive element 30, to this connection zone 13.

In FIG. 4, it can be seen that, at the location of the connection zone 13, the glass sheet 4 has a cut corner to allow the electrical connection. The Cu strip brought into contact with the collector 9 extends, outside the collector 9, beyond the cut in the corner of the sheet 4, in the form of the conductive element 30, to allow electrical connection in the area connection 13. After connection, the recess is then filled with an insulating material 16 such as araldite, which also fixes the end of the Cu strips. To make double electrical insulation, a small sheet of glass 17 4 mm thick can be glued above this area 13.

In the embodiment of Figures 1 to 3, the laminate 1 is surrounded by a frame 18, for example aluminum or PVC, and the space between the edge 19 of the laminate 1 and the frame 18 is filled with an electrically insulating and waterproof adhesive material 20, such as for example silicone. For the understanding of the drawing, this insulating material 20 has not been represented in FIG. 4. In FIG. 1, there have also been shown, in broken lines, fasteners 21 making it possible to fix the mirror on a wall. As a specific example, the sheet 2 is a glass sheet 2 mm thick which has undergone a chemical toughening treatment. The reflective coating 3 is formed by silvering in a manner known per se and comprises a layer of silver, a layer of copper and a layer of protective paint. In this specific example according to the invention, the protective paint is a thermosetting paint resistant to heat sold under the registered trademark "Triganite" and marketed by the company "Pearl Paint". The polymeric material is formed from two films 5 and 6 0.38 mm thick in PVB. The sheet 4 is a 4 mm thick glass sheet which has undergone a thermal hardening treatment. The conductive layer 7 is a doped SnC ^ layer with a thickness of about 70 nm obtained by pyrolysis. The conductive lacquer 10 is a cold-hardening silver-based lacquer. To improve the electrical conductivity of the collectors, it is possible to deposit a strip 31 of silver-based lacquer baked in the oven (shown in dashed lines in FIG. 2) before depositing the SnO 2 layer. At the location of the collectors, the SnC> 2 layer is thus sandwiched between two strips 10 and 31 of conductive lacquer. In this case, for example, two strips of conductive lacquer are deposited by screen printing on the glass sheet 4 at the location of the collectors and this glass sheet is heated in an oven. This conductive lacquer is baked. At the outlet of the oven, the SnC 4 layer is deposited and the glass sheet is rapidly cooled, by blowing cold air, so as to obtain thermally hardened glass. The strips of cold hardening conductive lacquers are then deposited and the Cu strips are applied before proceeding to the laminating operation.

In this specific example, the laminate 1 is a rectangle of 1183 mm by 683 mm, the resistance per square of the heating layer is 143 ohm and its total resistance is 82 ohm. The specific heating power 7 of the layer is 800 W / m and the power dissipated by the laminate 1 is 600 W. The temperature of the front face does not exceed 60 ° C. To prevent this temperature from being accidentally exceeded, a temperature limiter (not shown in the figures) can be placed. It is a small plastic case of 50x50x15 mm, with double electrical insulation, containing a bimetallic strip which cuts the power supply circuit for example at 60 ° C and restores it for example at 40 ° C. This box is glued to the external face of the glass sheet 4, near the connection area 13. The power cord 15 is connected to this box and this box is connected to the power supply sector.

The glazing according to this exemplary embodiment has successfully passed the safety tests for an electric heating system operating in a humid atmosphere and in particular the test of insulation resistance and dielectric strength at a voltage of 3.750 V.

As a variant of the specific example described above, the collectors 8 and 9 were formed by strips of Cu obtained by spraying Cu with a flame. In this example, the silver-based conductive lacquer has been omitted, as well as the end 11 of the first conductive element. The latter is therefore formed by the strip 12 which is a Cu strip welded to the end of the collector 8.

In the embodiment of Figure 5, the heating mirror has no frame. The reflective coating 21 is deposited on a sheet of chemically toughened glass 22. The conductive layer 23 is carried by the sheet 24 of thermally hardened glass. The two sheets 22 and 24 are joined together by laminating with the aid of a polymeric material in the form of two films 25 and 26. The glass sheet 24 is smaller than the sheet 22 so as to leave a margin 27. This margin 27 is bordered by a strip of self-adhesive polyurethane foam 28 and the space between the strip 28 and the edge of the sheet 24 is filled with an electrically insulating adhesive material 29 which is waterproof and watertight, for example silicone.

This exemplary embodiment has also successfully passed the electrical insulation tests for a humid environment. Its structure is lighter and it meets a certain demand, aesthetically, for unframed mirrors.

The exemplary embodiments shown in Figures 1 - 5 show a preferred solution in which the conductive layer 7, 23 has a smaller area than that of the sheet 4, 24 which carries it. The edge of the conductive layer is thus isolated both by the interlayer polymeric material and by the sealing material 20,29.

Claims (17)

1. Laminated heating mirror comprising a metallic coating reflecting light in a specular manner deposited on a transparent glass sheet, characterized in that it comprises at least two glass sheets secured by laminating using an interlayer polymeric material, one of the sheets of which carries, on its face oriented towards said polymeric material, an electrically conductive layer, electrically isolated from the external surface of the mirror, and two current collectors each connected to an electrically conductive element for connection to the electrical power source, in that at least one of said conductive elements (hereinafter called "first conductive element") passes through at least part of said polymeric material and extends, inside the mirror, up to the immediate vicinity of the end of the other conducting element in a single connection zone located at the periphery series of the mirror, and in that the portion of the polymeric material and the conductive layer are surrounded by electrically insulating material. 2. Heating mirror according to claim 1, characterized in that said first conductive element is embedded in said polymeric material. 3. Heating mirror according to one of claims 1 or 2, characterized in that the mirror is rectangular and the collectors extend along two opposite sides of the rectangle and in that said connection zone is located in a corner from the mirror. 4. Heating mirror according to claim 3, characterized in that at the place of said connection zone, the corner of one of the glass sheets is cut to allow the passage of the supply wires, and the connection of these to said conductive elements is embedded in an insulating material. 5. Heating mirror according to one of claims 1 to 4, characterized in that at least the said first conductive element comprises a flat metal strip, and preferably the said strip is a Cu strip. 6. Heating mirror according to one of claims 1 to 5, characterized in that the surface of the sheet carrying said conductive layer has a marginal area greater than 1 cm, preferably greater than 1.5 cm, free of any material conductive, which extends substantially along its entire periphery. 7. Heating mirror according to one of claims 1 to 6, characterized in that the conductive layer is a layer of doped tin oxide. 8. Heating mirror according to one of claims 1 to 7, characterized in that the reflective coating is deposited on a first glass sheet and is formed of a layer based on silver and / or copper which is electrically insulated of the conductive layer carried by another glass sheet by means of a heat-resistant protective paint and of the said polymeric material. 9. Heating mirror according to one of claims 1 to 8, characterized in that the two glass sheets have undergone a treatment of reinforcement of their mechanical resistance. 10. Heating mirror according to claim 9, characterized in that the glass sheet carrying the reflective coating is a glass sheet having undergone a chemical toughening treatment. 11. Heating mirror according to claim 10, characterized in that the glass sheet carrying the reflective coating has a thickness of less than 3 mm. 12. Heating mirror according to one of claims 9 to 11, characterized in that the glass sheet carrying the conductive layer is a sheet of thermally hardened glass. 13. Heating mirror according to one of claims 1 to 12, characterized in that it comprises, on its external face situated on the side which does not reflect light in a specular manner, a layer with low emissivity. 14. Heating mirror according to one of claims 1 to 13, characterized in that its edge is at least partially covered with electrically insulating and waterproof material. 15. Heating mirror according to one of claims 1 to 14, characterized in that the sheet carrying the reflective coating is larger than another sheet which is secured thereto, leaving a margin all along the periphery of the mirror. 16. Heating mirror according to one of claims 1 to 15, characterized 2 in that its heating power is greater than 500 W / m, and preferably greater than 700 W / m ^. 17. Heating mirror according to one of claims 1 to 16, characterized in that at least one of the collectors is formed by two strips of electrically conductive lacquer superimposed between which an edge of the conductive layer is sandwiched.