WO2005003047A1

WO2005003047A1 - Pane which can be heated by means of invisible light

Info

Publication number: WO2005003047A1
Application number: PCT/IB2004/050994
Authority: WO
Inventors: Dietrich Bertram; Augustinus Gregorius Henricus Meijers; Walter Schlager; Lukas KÜPPER
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2003-07-03
Filing date: 2004-06-24
Publication date: 2005-01-13

Abstract

The invention relates to a pane (1) which can be heated by means of invisible light (5,6,7,8). The pane possesses a material (4) which is permeable to visible light and which absorbs invisible light. The material (4) absorbs the light and converts the light energy into heat. This heat is transmitted to the pane which is then warmed up, and any ice and condensation on the pane is also warmed up and cleared.

Description

Pane which can be heated by means of invisible light

The invention relates to a pane which can be heated by means of invisible light

One such pane, which is used as a windscreen in a vehicle, is known from DE 41 22 462. The windscreen can be heated by means of a lamp radiating infrared light. The lamp is positioned under the windscreen. The lamp has to burn for an extended period of time in order to warm the windscreen because the heating capacity is low-efficiency. Furthermore, red light is radiated forwards from the windscreen. This compromises safety because red light characterizes the rear end of a car. To enable the car to be driven safely, the car windscreen must be transparent and clear of any materials that may interrupt vision. Condensation and ice form on the windscreen in cold weather conditions, drastically reducing visibility and, therefore, preventing safe driving. However, it is tiresome and annoying to have to scrape the ice or wipe the condensation off the windscreen, especially in cold temperatures. Consequently, it could be useful to have this type of heating element integrated into the front or rear windscreen of the car, enabling the driver to clear the ice and condensation quickly and easily by raising the temperature of the pane. However, the heating element must also be invisible or be adequately transparent so as not to hinder the driver's view. Existing technical solutions to this problem are thin metal wires which run within the pane and which are heated by an electrical current. However, these wires are not invisible and, if they are placed in the windscreen in particular, can confuse the driver with dangerous consequences, causing him or her to pay more attention to the structures in the windscreen than to the road and the traffic. Another possible solution may be to use transparent metallic coatings or transparent conductive coatings with a terminating ohmic resistor and the same principle as that for electric heating. The biggest disadvantage with this solution is the level of costs associated with these types of coatings, especially for large-area applications. Consequently, it is an object of the present invention to indicate a simple pane which can be heated by means of invisible light. This object is solved in accordance with the features of claim 1. In accordance with the invention, the pane possesses a material which is permeable to visible light and which absorbs invisible light. The material absorbs the light and converts the light energy into heat. This heat is transmitted to the pane which is then warmed up, and any ice and condensation on the pane are also warmed up and cleared. The material which is permeable to visible light and which absorbs invisible light is simply applied to the pane as a film coating. The pane is advantageously designed as a laminated pane with a film which possesses a material which is permeable to visible light and which absorbs invisible light. One such multilayer pane is used as a windscreen in vehicles. A plastic film which is integrated into one such windscreen is impregnated with a dye which possesses the absorbent material. The material advantageously absorbs invisible light in the infrared range, hereinafter also referred to as the IR range, with a wavelength greater than 750 nm. The material advantageously absorbs invisible light in the ultraviolet range, hereinafter also referred to as the UV range, with a wavelength of less than 400 nm. UV light is rich in energy and can, therefore, achieve a high thermal output. The material advantageously absorbs invisible light in the IR and UV range. A higher thermal output can be achieved by using radiation from both ranges simultaneously. The light is advantageously coupled into the pane. Consequently, a light source is positioned in such a way that the light is conducted directly into a pane. The light source is positioned on or in the pane, the light is coupled directly into the pane. The light is advantageously coupled in via a fibre glass element or another optical fibre. The light can be coupled to several ends of the windscreen from a centrally positioned light source via several optical fibres. Distribution of the absorbent material advantageously possesses a gradient. The absorption gradient is low at a point of entry of the light so as to absorb strong radiation a little and higher at points which are further away from the point of entry of the light so as to absorb weak radiation more. Consequently, areas which are far apart can also be warmed well with radiation which has already been weakened, or places which are in particular need of being heated up can be warmed up more. The light advantageously strikes the surfaces of an absorber, which possesses the absorbent material, at a specified angle of incidence. This type of absorber is designed as a film, layer, coating or partial coating. The light, or light beam or light radiation to be more precise, is guided within a pane at a specified angle, which is known as wave guiding. This type of guiding is possible within the actual absorber or in a pane adjacent to the absorber. Total reflection occurs above a limit angle. The light is not radiated outwards, nor is it radiated forwards from a windscreen as red light; instead, all light is used for the purpose of absorption and, thus, for warming. The pane is advantageously used as a windscreen, with at least one glass element, in a vehicle. One such pane can be used in a vehicle as a front or rear windscreen made from glass or plastic. Such windscreens, with at least one glass element, are designed as panes of multilayer glass with an outer pane of glass, an inner pane of glass and a plastic film in-between, which is impregnated with a dye. Light is used to heat the window pane, so as to clear any condensation or ice. This is achieved by either using infrared-absorbent material and a light source which radiates infrared light and which is integrated into the pane, hereinafter referred to as the pane of glass or glass, or alternatively by means of a material, which absorbs near UV light, and a near UV light source. Irrespective of the method, the absorber must be transparent for the visible range so as to preserve the transparency of the window, and the light source must radiate within the invisible portion of the spectrum so as to avoid any reduction in contrast. Light is used which is invisible to the human eye so as to increase the temperature of the glass by means of an absorbent material which is integrated into the pane of glass. Consequently, the pane remains transparent, and this system functions harmlessly and is not confusing to the driver. Furthermore, this system is very inexpensive and easy to control. The light which can be used is radiated under 380 nm, in the near UV range, from indium, gallium and nitrogen-based light-emitting diodes, or InGaN or GaN-LEDs for short. This light can be absorbed by many different materials which do not absorb light in the visible range, which means that they are completely transparent to the eye. The material is either distributed in the glass as an intermediate layer or is applied to the glass as a coating. To come back to the near UV light, this light is distributed within the glass by means of total internal reflection, and the absorbing material converts the light energy into heat. This heat is transmitted to the glass which is then warmed up, and any ice and condensation on the glass is also warmed up and cleared. Alternatively, near IR light, e.g. with a wavelength above 750 nm, can be used in combination with a near IR-absorbent material. The LEDs or other light sources are positioned in such a way that the light is effectively conducted into the windscreen and distributed by means of total reflection. The absorbent material can also be distributed within the window with a density gradient in order to create different thermal outputs across the windscreen. Even though this type of pane is primarily used as a windscreen in a vehicle, this principle can also be transferred to other applications. It works on the principle that the light is distributed within the glass by means of internal total reflection. This means that, depending on how the light is introduced, the absorbent material must have a concentration gradient, where possible, so that the thermal output is distributed homogeneously within the pane of glass. It may also be applied with precise distribution in cases where some areas require higher temperatures than other areas. Light may also be conducted between the light source and the window glass by means of glass fibres or other optical fibres. In order to gain a better understanding, these and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings: Fig. 1 shows a heatable pane of multilayer glass with lamps radiating infrared light; Fig. 2 shows a heatable pane; Fig. 3 shows an absorption spectrum for an IR light-absorbent dye; and Fig. 4 shows a further absorption spectrum for another IR light-absorbent dye.

Fig. 1 shows a pane of multilayer glass 1 with an outer pane of glass 2, an inner pane of glass 3 and a plastic film 4 in-between, which is impregnated with a dye. The dye possesses UV light and IR light-absorbent material. The plastic film 4 acts as an absorption layer. Lamps 5, 6, 7 and 8 radiating infrared light are distributed evenly along the side face 9 of the pane of multilayer glass 1 and radiate infrared light with a wavelength of 909 - 910 nm. Fig. 2 shows a heatable pane 21 with a strip of glass 22 and an absorption layer 23. The strip of glass 22 is spray-coated with an IR light-absorbent dye. Once the solvent has dried, IR radiation with a wavelength of 950 nm is admitted into the pane of glass. Precisely because of the absoφtion of the layer 23, the light creates energy in the layer 23 which increases the temperature of the absoφtion layer 23 and, thus, the temperature of the pane of glass 22. Fig. 3 shows an absoφtion spectrum in which absoφtion is applied across the wavelength. One such absoφtion spectrum is achieved with a coating of Epolight 2063, dye no. IV-62B, recommended for laser diodes and coatings with maximum absoφtion at 910 nm, with dark green powder, absoφtion coefficient 74. The melting point is 147°C to 150°C. Fig. 4 shows an absoφtion spectrum in which absoφtion is applied across the wavelength. One such absoφtion spectrum is achieved with a coating of Epolight 2067, dye no. IV-67, recommended for laser diodes and coatings with maximum absoφtion at 909 nm, with green powder, absoφtion coefficient 94. The melting point is 148°C to 154°C. These spray-coatings are distributed by EPOLIN, INC., 358-364 Adams Street, Newark, NJ 07105. Also refer to the website at www.epolin.com.

REFERENCE LIST:

1 Pane of multilayer glass

2 Outer pane of glass

3 Inner pane of glass

4 Plastic film

5 Lamp

6 Lamp

7 Lamp

8 Lamp

9 Side face

10

11

12

13

14

15

16

17

18

19

20

21 Heatable pane

22 Glass strip

23 Absoφtion layer

24

25

Claims

CLAIMS:

1. A pane (1, 21), which can be heated by means of invisible light, characterized in that the pane (1, 21) possesses a material which is permeable to visible light and which absorbs invisible light.

2. A pane as claimed in claim 1 , characterized in that the material which is permeable to visible light and which absorbs invisible light is applied to the pane (21) as a film coating (23).

3. A pane as claimed in claim 1, characterized in that the pane (1) is designed as a laminated pane (1) with a film (4) which possesses material which is permeable to visible light and which absorbs invisible light.

4. A pane as claimed in any one of the preceding claims 1 - 3, characterized in that the material absorbs invisible light in the infrared range.

5. A pane as claimed in any one of the preceding claims 1 - 3, characterized in that the material absorbs invisible light in the ultraviolet range.

6. A pane as claimed in any one of the preceding claims 1 - 3, characterized in that the material absorbs invisible light in the infrared and ultraviolet range.

7. A pane as claimed in any one of the preceding claims 1 - 6, characterized in that the light is coupled into the pane.

8. A pane as claimed in any one of the preceding claims 1 - 7, characterized in that the light is coupled via an optical fibre.

9. A pane as claimed in any one of the preceding claims 1 - 3, characterized in that a distribution of the absorbent material possesses a gradient.

10. A pane as claimed in any one or more of the preceding claims, characterized in that the light strikes surfaces of an absorber (4, 23), which comprises the absorbent material, at a specified angle of incidence.

11. A pane as claimed in any one or more of the preceding claims 1 - 10, used as a windscreen, with at least one glass element (2, 3), in a vehicle.